Combustion apparatus and methods

Abstract

A combustion apparatus is described having a generally elongated combustion container with a longitudinal axis, a proximal end, an exhaust end spaced axially forward from the proximal end, a proximal end wall, an exhaust end wall, and an all-around sidewall extending between the end walls and about the longitudinal axis. The end walls and sidewall substantially define a combustion chamber. The apparatus also includes a combustion chamber exhaust positioned on the exhaust end, a fuel-air delivery system positioned to direct fuel into the combustion chamber, and an air inlet located generally tangentially on the sidewall to direct air flow generally tangentially into the chamber and induce swirl about the longitudinal axis.

Description

The present application claims the benefit of U.S. Provisional Application Ser. No. 61/403,290, filed on Sep. 12, 2010 (pending). The disclosure of the previously filed provisional application is hereby incorporated by reference for all purposes and made a part of the present disclosure.

This invention was made with government support under Contract Nos. ONR N00014-10-C-0334 and ONR N00014-09-C-0121 awarded by the Office of Naval Research. The government has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a fuel combustion method and an apparatus for performing same. More particularly, the invention relates to an apparatus and/or method for providing a generally uniformly volume distributed combustion, and further, an improved apparatus and/or method of mixing for uniformly volume distributed combustion.

2. Description of Related Art

It was arguably not until the late 1970s and early 1980s, as a result of the first and the second energy crisis, that research and development activities began to seriously focus on improving energy efficiency. Similarly, in the same time period, industry began to truly recognize the need for eliminating noxious pollutants such as nitrogen oxides, mostly due to concerns over human health and concern for the environment.

To achieve these goals, the combustion temperature must be less than that at which nitrogen oxidizes. On the other hand, the combustion temperature must be high enough for complete combustion with carbon monoxide totally burnt. Therefore, the optimal combustion temperature must be around 1100° C. For combustion to occur at the optimal temperature, fuel and an oxidizer must be finely mixed and preheated throughout the entire combustor volume. Although uniformly distributed (flameless) combustion was discovered circa 1911, it was not until recently that uniformly distributed combustion (flameless oxidation) has become a focus of industrial research.

In flameless combustion, ignition occurs and progresses with generally no visible or audible signs of a flame that is usually associated with burning. As early as 1989, it was found that combustion in a furnace could be sustained even with an extremely low concentration of oxygen, if the combustion air was sufficiently preheated. Particularly, during experiments with a self-recuperative burner, it was observed that at furnace combustion temperatures of about 1000° C. and an air preheat temperature of about 650° C., no flame was visible and no ultraviolet signal was detected. Nevertheless, the fuel was totally burnt, and carbon monoxide as well as nitric oxide content of the exhaust was found to be extremely low.

Conventionally, to initiate flameless combustion, preheated oxidizing air and gas fuel is fed into a combustion chamber at relatively high injection speeds. The geometry of the combustion chamber and the high injection speed of the fuel-air mixture create large internal recirculation of the combustion mixture. Once the recirculation is sufficient, the combustion becomes distributed throughout the volume of the combustion chamber and the flame is no longer visible. Further, as an application of such a principle, nitric oxide emission can be reduced through the dilution of the combustion air with the circulated burned gas in the furnace. Dilution of the combustion air can reduce the oxygen content of the oxidizer, which decreases temperature fluctuations in the combustion chamber as well as the mean temperature, resulting in low amounts of nitric oxide emission.

Recognizing the potential benefits of flameless combustion, the industry has attempted to develop various types of combustion chambers which support flameless combustion. For example, U.S. Pat. No. 6,796,789 by Gibson et al., entitled “Method to Facilitate Flameless Combustion Absent Catalyst or High-Temperature Oxidant” describes an oval-shaped combustion chamber configured to circulate gas fuel with flue gas and combustible air. U.S. Pat. No. 5,340,020 by Manus et al., titled “Method and Apparatus for Generating Heat by Flameless Combustion of a Fuel in a Gas Flow” describes a combustion apparatus, which utilizes a catalyst for producing the flameless combustion. U.S. Pat. No. 6,826,912 B2, issued on Dec. 7, 2004 by Y. Levy et al., entitled “Design of Adiabatic Combustors” describes a gas turbine combustion chamber, to produce high-pressure gases for the turbine. The combustion chamber has a primary combustion zone containing a substantially vitiated-air zone into which the fuel is injected. The primary air inlet is positioned and directed to produce an internal recirculation that generates a ring-like vortex within the primary zone, thereby providing the vitiated-air zone and maintaining therein a state of flameless oxidation.

U.S. Pat. No. 5,839,270 by Jirnov et al., entitled “Sliding-Blade Rotary Air-Heat Engine with Isothermal Compression of Air” describes a particularly efficient combustion chamber originally configured for use with the sliding-blade rotary air-heat engine. The Jirnov “vortex” combustion combined with a straight-flow pre-combustion chamber successfully solved problems associated with multi-fuel operation with a high completeness of combustion over the wide range of the coefficient of air concentration, while producing a substantial drop in toxicity of the exhaust gases. The combustor was also characterized by providing a simplified combustor design and ease of fabrication, high thermal as well as volumetric efficiency, while being able to employ various types of combustible hydrocarbon gas or liquid fuel.

Yet another combustion apparatus suitable for flameless combustion is described in U.S. patent application Ser. No. 12/774,576, filed May 5, 2010, and entitled “Apparatus and Methods for Providing Uniformly Distributed Combustion of Fuel”, (which application is assigned to a common assignee of the present application and includes at least one common applicant/inventor). The disclosure of U.S. patent application Ser. No. 12/774,576 is incorporated herein by reference for all purposes and made a part of the present disclosure. In this previously filed application, a combustion chamber is described as including a precombustion chamber in addition to a main combustion chamber. The pre-combustion chamber provides delivery of a super-rich fuel and air mixture, ignition, and/or partial combustion and decomposition of heavy and low grade fuels. In operation with the Jirnov engine, prior to entering the pre-combustion chamber, the combustion air is preheated by exhaust gases and then, upon entry, heating coils in the pre-combustion chamber further heat the air. Heated fuel is also injected into the pre-combustion chamber prior to entry into the main vortex combustion chamber.

To further facilitate uniformly volume distributed combustion of fuel, the pre-combustion chamber in this previous application provides at least one air injection inlet port positioned to induce a first stage vortex in the pre-combustion chamber. Further, the pre-combustion chamber is interfaced with the main combustion chamber to induce a second stage vortex in the mian combustion chamber. Specifically, the entry of the fuel-air mixture into the main vortex combustion chamber is such that a very large swirl is created which helps ensure proper mixture and a substantially uniform combustion within the combustion chamber. The main vortex Combustion chamber may also be equipped with an elongated combustion exhaust conduit. The conduit extends from the exhaust of the combustion chamber to the opposite end of the chamber. The combustion exhaust conduit provided therefore is a physical or structural barrier between the inlet to the main vortex combustion chamber and its exhaust.

In recent years, due to the cost of fuel and due to concern for the environment, there has been a high interest in the use of bio-fuels. Bio-fuels can include solid, liquid or gas fuel derived from recently expired biological material. Theoretically, bio-fuel can be produced from any biological carbon source, the most common of which includes plants as well as plant-derived materials. The bio-fuel industry is expanding in Europe, Asia and the Americas. The most common use for bio-fuels is as liquid fuels for automotive transport. However, there is also a desire within the industry to use bio-fuels to generate steam and/or electricity. Bio-diesel is the most common bio-fuel in Europe, and is becoming more popular in Asia and America. Biodiesel can be produced from oils or fats and forms into a liquid similar in composition to petroleum diesel.

For example, bio-diesel production can result in glycerol (glycerin) as a by-product at one part glycerol for every 10 parts biodiesel. This has resulted in saturation in the market for glycerol. Accordingly, rather than being able to sell the glycerol, many companies have to pay for its disposal. Sources indicate that the 2006 levels of glycerol production were at about 350,000 tons per annum in the USA, and 600,000 tons per annum in Europe. Sources further indicate that such levels will only increase as biodiesel will become more popular as a homegrown energy source and as Europe implements EU directive 2003/30/EC, which requires replacement of 5.75% of petroleum fuels with bio-fuel, across all member states by 2010. Therefore, inventors recognized the need for an apparatus as well as methods of economically disposing of glycerin or other byproducts in an environmentally friendly and energy efficient manner.

The applicants also recognize that, although considered a waste product of biodiesel fuel production, byproducts, such as glycerin, have significant energy delivery potential. Glycerin, however, along with some other forms of waste/bio-fuels, has characteristics which must be overcome in order to employ them as a fuel source. Conditions required for efficient combustion of glycerin and other waste/bio-fuels include preheating, fuel fine atomization, fast and fine mixing with oxidizer as well as sufficient residence time in a combustion chamber. Therefore, recognized by the applicants is the need for an apparatus and methods for economically and efficiently burning such heavily viscous waste/bio-fuels in a combustion chamber to produce an exhaust which can be utilized as an energy source.

Further recognized by the applicants is the need for such an apparatus and methods which can provide uniform volume-distributed oxidation to thereby decrease harmful emissions and increase energy efficiency. To this end, it is also desirable to provide improved means and apparatus for uniform volume distributed oxidation and uniform flameless combustion.

SUMMARY OF THE INVENTION

In view of the foregoing, embodiments of the present invention advantageously provide an apparatus and methods for economically and efficiently burning gaseous and liquid fuels, as well as viscous low-grade bio-fuels. Embodiments of the present invention also advantageously provide an apparatus a combustion chamber configured to provide a uniform volume distributed fuel-oxidizer mixture to thereby decrease nitric oxide emissions and increase energy efficiency. Embodiments of the invention also include related methods of operating same, and more particularly, combustion methods including advantageously organizing flows within a chamber to enhance mixing and/or heat transfer. Embodiments of the present invention provide an apparatus and methods which improve upon the Jirnov vortex combustion chamber and precombustion chamber and methods described in U.S. Pat. No. 5,839,270 by Jirnov et al., entitled “Sliding-Blade Rotary Air-Heat Engine with Isothermal Compression of Air” and the U.S. patent application Ser. No. 12/774,576, filed May 5, 2010, titled “Apparatus and Methods for Providing Uniformly Distributed Combustion of Fuel.”

As used herein, the term “fine mixing” is a term known by those skilled in the art, and means that the distance between an oxidizer molecule and a fuel molecule become close or substantially close to the free path of molecules. The term “fast mixing” is also a term in the art and means that the time of mixing is significantly shorter than the residence time (axial length dimension/axial velocity). The mixing time is generally understood to be equal to a dimension scale of eddies divided by the turbulence velocity (difference in two magnitude of velocities). It is desirable for the mixing time to be substantially smaller small than the combustion time (which is a function of temperature, pressure etc.). In other, more specific descriptions of aspects of the invention provided here, the term mixing may refer also to facilitating and enhancing the heat transfer between “mixed’ or distributed constituents of the combustion chamber.

In the pursuit of desirable combustion properties, including stable and substantially complete fuel burning with low levels of harmful emissions, it is desirable to generate high speed counter flows, and fine scale Karman eddies so as to promote fast and fine mixing of combustion constituents. As further understood by applicants, fast and fine mixing, including preheating, facilitates uniformly volume distributed oxidation and uniform flameless combustion. To achieve these specific conditions, applicants sought to provide a combustor and method that entail the specific organization of advantageous flows preceding or simultaneous with combustion.

In one aspect, a combustion apparatus is disclosed having a generally elongated combustion container. The container has a longitudinal axis, a proximal end, an exhaust end spaced axially forward from the proximal end, a proximate end wall, an exhaust end wall, and an all-around sidewall extending between the end walls and about the longitudinal axis, the end walls and sidewall substantially defining a combustion chamber. The apparatus further includes a combustion chamber exhaust positioned on the exhaust end, a delivery system positioned to direct fuel into the combustion chamber for combustion, and an air inlet located generally tangentially on the sidewall to direct air flow generally tangentially into the chamber and induce swirl about the longitudinal axis. In a preferred embodiment, an outside casing is provided about the combustion container and spaced circumferentially outward from the container to define an air annulus therebetween. The casing is equipped with an outer air inlet that communicates an external air supply with both the annulus and the air inlet into the combustor chamber. Accordingly, the air annulus can direct air flow toward the proximate end and along the outside of the container thereby exchanging heat with the side walls of the container and more preferably, directing hot air to the proximate end and in the vicinity of a fuel-air delivery system associated with the combustion chamber. In this way, the annulus serves to cool the side walls and recirculate the heat loss back into the combustion chamber.

In another aspect, a method of combustion is provided. The method entails providing an elongated combustion container having a longitudinal axis, a pair of axially spaced apart end walls generally defining a proximate end and a distal end, a sidewall extending between the end walls, and an exhaust opening in the distal end. Fuel is delivered into the chamber at the proximal end and tangential air flow is introduced into the combustion chamber to induce swirl flow about the longitudinal axis. The swirl flow further induces meridional circulation in the combustion chamber, including circulatory regions and flow through regions exiting the exhaust opening. Furthermore, combustion is initiated in the combustion chamber, which includes exhausting hot gases through the exhaust opening.

In yet another aspect, a fuel and air delivery system is disclosed having a radial air swirler and a fuel nozzle. The air swirler includes a swirl chamber positioned about a swirl axis, a radial inlet for introducing rotational air flow into the swirl chamber, and a central opening positioned to receive swirling flow from the chamber. The fuel nozzle is directed axially through the central opening of the swirler, and wherein the air swirler further includes a nozzle outlet in fluid communication with the central opening and having an all around forwardly diverging sidewall for directing a diverging annular swirl flow outward.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features and advantages of the present invention may be understood in more detail, a more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings that form a part of this specification. It is to be noted, however, that the drawings illustrate only various exemplary embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it may include other effective embodiments as well.

FIG. 1 is a longitudinal cross-sectional view of a combustion apparatus, according to the present invention;

FIG. 2 is a lateral cross-sectional view along line 2-2 in FIG. 1;

FIG. 3 is a lateral cross-sectional view along line 3-3 in FIG. 1;

FIG. 4 is a detailed side view of a fuel-air mixture delivery system in FIG. 1;

FIG. 4A is a simplified side view illustration of the fuel-air delivery system in FIG. 4 further illustrating a local circulation region generated by the system, according to the present invention;

FIG. 5 is a perspective view of an air swirler according to the present invention;

FIG. 6 is a graphical diagram illustrating fuel and air and flow characteristics proximate the fuel-air delivery system in FIG. 4 during operation, according to the present invention;

FIG. 7 is a simplified schematic of the combustion apparatus in FIG. 1 and circulatory flows generated therein, according to the present invention;

FIG. 7A is a simplified representation of the results of numerical simulations describing meridional motion in the combustion apparatus in FIG. 7;

FIGS. 8A-8E are simplified illustrations of particle swirl trajectories generated in the combustion apparatus in FIG. 7 during operation, according to the present invention;

FIG. 9 is a simplified schematic of an alternative combustion apparatus and circulatory flows generated therein, according to the present invention;

FIG. 9A is a simplified representation of results of numerical simulations describing meridional motion in the combustion apparatus in FIG. 9;

FIG. 10 is a simplified schematic of circulatory flows generated inside a combustion apparatus, according to an alternative embodiment of the present invention;

FIG. 10A is a simplified representation of results of numerical simulations describing meridional motion in the combustion apparatus in FIG. 10;

FIG. 11 is a simplified side view illustration of an alternate combustor apparatus in the form of a burner, according to the present invention;

FIG. 12 is a simplified schematic of yet another alternative embodiment of a combustion apparatus, and circulatory flows generated therein, according to the present invention;

FIG. 13A is a perspective view of a combustion apparatus according to yet another alternative embodiment of the present invention;

FIG. 13B is a side view of the combustion apparatus in FIG. 13A;

FIG. 13C is a rear view of the combustion apparatus in FIG. 13A;

FIG. 13D is a longitudinal cross-sectional view of the combustion apparatus in FIG. 13A;

FIG. 14A is a perspective view of a combustion liner and transition piece, according to the present invention;

FIG. 14B is a side view of the combustor components in FIG. 14A;

FIG. 14C is a longitudinal cross-sectional view of the combustor components in FIG. 14B;

FIG. 14D is a rear view of the combustor components in FIG. 14A;

FIG. 14E is a front view of the combustor components in FIG. 14A;

FIG. 14F is a lateral cross-sectional view across line 14F-14F in FIG. 14B;

FIGS. 15A and 15B simplified illustration of fluid dynamics proximate multiple fuel-air delivery systems as implemented in the combustion apparatus of FIG. 13, according to the present invention;

FIG. 16A is an axial end view of an alternate combustion apparatus, according to the present invention;

FIG. 16B is a detailed cross-sectional view of a transition piece operable with the combustion apparatus in FIG. 16A;

FIG. 17A is a simplified representation of a combustion apparatus according to the invention; and

FIG. 17B is a simplified representation of an alternate embodiment of the combustion apparatus.

DETAILED DESCRIPTION

The present invention will now be described more fully with reference to the accompanying drawings, which illustrate the various exemplary embodiments of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited by the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough as well as complete and will fully convey the scope of the invention to those skilled in the art and the best and preferred modes of practicing the invention.

FIGS. 1-17 depict various combustion systems, components of combustion systems, and various applications of the combustion systems, embodying or exemplifying one or more aspects of the present invention. In one respect, a combustion apparatus according to the invention and its various applications represent improvements to the vortex combustion chamber and the precombustor and main combustor configurations described above. More specifically, the combustion apparatus and its method of operation achieves generally uniformly volume distributed oxidation and further, improves mixing of fluids (e.g., fuel, air, flue gas, and other combustion constituents) in the combustion apparatus. In further aspects, the combustion apparatus and method achieve fast and fine mixing of fluids for combustion. The inventive combustion apparatus can achieve flameless combustion conditions at the exit, substantially complete combustion, and very low levels of nitric oxide (NOx) and carbon monoxide (CO) emissions. Embodiments of the invention are, therefore, well suited for use with turbines and heating systems. Specific applications of the combustion apparatus according to the invention include those utilizing a conventional liquid fuel such as jet propellant, diesel, kerosene, or gasoline, or a gaseous fuel, such as hydrogen, CO, or carbohydrate. Other applications may utilize the burning of a waste fuel, such as glycerol (glycerin) and emulsified heavy oil (with water) fuels.

Exemplary Combustion Apparatus and Method

Referring first to FIGS. 1-5, a combustion apparatus 7, according to an embodiment of the present invention, features a generally cylindrical outer casing or housing 13 defined partly by a longitudinal axis YY. The outer housing 13 includes an all-around sidewall 15 positioned about the axis YY and extending between a pair of end walls 17, 19. In embodiments described herein, the outer housing 13 (i.e., the combustion apparatus 7) is operationally engaged with a fuel supply (fuel pipe 21) at or near the proximal end wall 17, a transition piece at the opposite or distal end wall 19, and a high pressure air source, such as a compressor, at the sidewall 15.

Referring to FIG. 1 specifically, the proximal end wall 17 is positioned on the left side of the Figure while the distal end wall 19 is spaced axially to the right and across the axial length of the outer housing 13. The end walls 17, 19 are preferably arranged in mutual parallel relation and generally perpendicular to the longitudinal axis YY.

In preferred embodiments, the combustion apparatus 7 exhausts hot flue gases at the distal end and through a centrally located exhaust opening 25. An exhaust pipe 23 extends though the distal end wall 19 and engages the exhaust opening 25 to receive the high pressure, hot flue gases. The exhaust pipe 23 communicates the gases to a transition piece, turbine, nozzle, or other component, as required by the specific application. In some of the descriptions provided herein, components, fluids, or processes described at or about the distal end wall 19 may be referred to as being forward or downstream of components or fluids described as near the proximal end wall 17. The distal side or end of the combustion apparatus 7 may also be referred to as the exhaust or exhaust end.

The combustion apparatus 7 also includes an elongated, preferably cylindrical combustor liner (or combustion container) 31 having a diameter less than that of the outer housing 13. The combustor liner 31 is positioned centrally within the outer housing 13 about the longitudinal axis YY, thereby defining an elongated cavity or combustion chamber 33. The preferably cylindrical combustor liner 31 is further described as including all around sidewalls 35 that extend axially between a substantially enclosed proximal end wall 37 and a partially open distal end wall 39. The distal end wall 37 is located substantially adjacent the distal end wall 19 of the housing 13, such that the centrally located exhaust opening 25 goes through both end walls 19, 39. The proximal end wall 37 is preferably spaced axially forward of the proximal end wall 17 of the outer housing 13 to define a cylindrical space 9 therebetween. In preferred embodiments, the proximal end wall 37 and the area thereabout are utilized for receiving primary air, liquid or gaseous fuel, and delivering the desired fuel-air mixture for combustion. The cylindrical space 9 accommodates some of the components and facilitates some of the processes involved, as further described below.

The combustor liner 31 is also sized such that when the combustor liner 31 is centered within the housing 13, an annulus 41 of desired gap width is provided between the outer housing 3 and the combustor liner 31. As shown in FIG. 1, the annulus 41 extends circumferentially about the liner 31 and also axially past each end wall 37, 39 and into the cylindrical space 9. The outer housing 13 is further equipped with an air inlet opening 29 in the sidewall 15 and an air inlet pipe 27 that engages the inlet opening 29. The air inlet pipe 27 delivers pressurized air from the external compressor into the annulus 41 and the annulus 41 communicates the pressurized air throughout the outside of the liner 31, including the cylindrical space 9.

Pressurized air is also delivered to the combustion chamber 33. In the embodiment depicted by FIGS. 1-2, the sidewall 35 of the liner 31 includes a tangential opening or inlet 43 that corresponds with the air inlet opening 29 of the outer housing 13. The opening 43 is spaced directly inwardly from the air inlet opening 29 and is positioned tangentially on the sidewall 35. The opening 43 fluidly communicates, therefore, with the air inlet pipe 27 and allows injection of high pressure air into the combustion chamber 33. Due to the location of the openings 29, 43, high pressure air enters the combustion chamber 33 generally tangentially and at relatively high velocity, thereby facilitating swirl flow about the axis YY. Furthermore, the air inlet pipe 27 and opening 43 deliver high pressure, fresh air into the combustion chamber 33 and induces commencement of swirl flow at an axial location substantially near the exhaust 25 (i.e., well past the axial midpoint of the combustion chamber 33).

The configuration in FIG. 1 contrasts with that of previously described combustors. In the earlier-described combustor of U.S. patent application Ser. No. 12/774,576, the pressurized air inlet is also located axially and physically close to the exhaust. A combustion exhaust conduit is positioned around the exhaust, however, to provide a physical barrier directly between the inlet and the exhaust and to ensure that the fresh air inflow travels at least substantially the axial length of the combustor chamber before exiting the chamber.

Fuel-Air Delivery System

Referring specifically to FIGS. 3 and 4, the proximal end wall 37 of the combustor liner 31 supports an arrangement for delivering fuel and air for combustion purposes (hereinafter, fuel-air nozzle or fuel-air delivery system 45). In accordance with a further aspect of the invention, operation of the fuel-air delivery system 45 generates local circulation regions that serve as flame holders and help to quickly vaporize droplets of liquid fuel. The fuel-air mixture delivery system 45 may be described as including a disc-shaped swirler nozzle or swirler 47 and a fuel nozzle 49 operable with the swirler 47 to deliver fuel and air into the combustion chamber 33. Connected with the fuel pipe 21, the fuel nozzle 49 delivers a highly atomized jet or spray of liquid fuel into the local circulation region and the rest of the combustion chamber 33 (or a gaseous fuel in other applications). The fuel-air delivery system 45 may also be described as including an igniter (not shown in the Figures for this embodiment) positioned proximate the 10 local circulation region LCR and/or the fuel nozzle 49 to initiate combustion.

The primary components of the swirler 47 include a pair of open-centered circular discs or plates 53 that are attached to the proximal end wall 37 and about a circular opening in the end wall 37 and a swirl axis ZZ (which is preferably coincidental with axis YY). Independent of the end wall 37, the circular plates 53 are spaced apart in mutually parallel relation to define a swirl chamber and a converging air path therebetween. A plurality of radially arranged guide vanes are supported between the plates 53 just inside of the periphery of the plates 53. The radial guide vanes 55 are spaced apart and similarly angled to draw primary air into the swirl chamber along generally the same tangential direction (relative to swirl axis ZZ). Because the swirler 47 draws air from inlets that are on a plane generally parallel to the swirl axis ZZ, the swirler 47 is sometimes described as being a radial swirler or having radial inlets (as opposed to as axial swirlers or axial inlets).

The swirler 47 further includes a forwardly extending swirler nozzle or a diverging outlet 51, which for convenience of description may be referred to simply as cone 51 (although, the configuration may be more cone-like than a true geometrical cone). In an aspect of the invention, the cone 51 defines a divergent sidewall 61 positioned about swirl axis ZZ, but which diverges from the axis YY along the forward axial direction. The divergent sidewall 61 is shaped in a specific advantageous manner, as further described below. The open center of the swirler 47 preferably corresponds with the opening in the end wall 37 so that the cone 51 extends forwardly and outwardly in the combustion chamber 33 (see e.g., FIG. 4). In alternate embodiments, the cone 51 may be independently constructed from and attached to the swirler plates 53.

In respect to Figures of specific embodiments provided herein, the cone 51 or divergent sidewall 61 may be described as having or defining an internal region or zone Zi radially inward of the cone 51 (also referred to as the fuel and air delivery zone Zi). Just forward of the end wall 37, the diameter of the divergent sidewall 61 is reduced to define a throat area or throat 57 of minimum diameter. The fuel nozzle 49 extends through the center opening of the swirler plates 53 and into the throat 57. The fuel nozzle 49 is centered on the swirl axis ZZ to establish an annular gap 59 between it and the swirler plates 53. The nozzle 49 is, therefore, positioned to deliver an atomized fuel spray into the internal zone Zi of the cone 51.

In accordance with the invention, a pathway of rotating air flow A1 commences at the inlets between successive guide vanes 55 and rotates about the axis ZZ. While advancing radially inward, the air flow A1 intensifies as the rotational path shortens and converges on the annular gap 59 and the swirl axis ZZ. This creates a low pressure area at the center of the swirler 47. Upon entry into the annular gap 49, the now swirling flow presses against the center rim of the forward plate 55 and then the base of the sidewall 61. The annular swirl flow A3 moves axially forward, moving past the throat 57 and then, into the zone Zi defined internally (i.e., surrounded) by the cone 51. Centrifugal force presses the diverging, rotating flow to the sidewall where it forms an annular jet-like outflow A3.

As illustrated in FIG. 4A, operation of the fuel-air delivery system 45 generates a local circular flow or circulation region CR in and around the cone 51 and into the combustion chamber 33. The graphical diagram of FIG. 6 is provided to further illustrate the fluid dynamics that are present and occurring directly in front of the swirler 47 and in the cone zone or region Zi, and the local circulation region LCR formed thereabout. The diagram provides a side profile of the zone Zi with indications representing the movement of fuel spray, air, and hot flue gases within the zone Zi of the divergent sidewall 61. A representation of the fuel nozzle 49 is provided at the graph origin, generally in the throat 57 and along the swirl axis ZZ. The diagram indicates counterflow CF of hot flue gases directed back into the throat 57, a thin annular section of swirling jet-like air outflow A3 from the swirler 47 advancing forwardly along the divergent sidewall 61, and an area of atomized fuel spray FS from a tip 63 of the fuel nozzle 49.

The profile of the sidewall 61 has the shape of the streamline indicated by the bold curve SW. In preferred embodiments, the sidewall profile is described by the relation, r/rmin=xs{x[2xs−(1+xs)x](1+xs)}−½, x=cos θ, and xs=cos θs. In this equation, r is the length of a line connecting the axis-bottom intersection and a point on the sidewall, rmin is the minimum value of r, θ is the angle between the line and the axis, and θs is the θ value for a point located at the sidewall upper edge. The parameters, rmin and θs, can be conveniently selected depending on the air flow rate and the fuel spray angle δ (see the angle between the swirl axis ZZ and the dotted line). Thus, a fuel spray angle δ 5 may be achieved that is sufficiently less than the sidewall angle θs to ensure that the thin air flow A3 passes by the hot flue gas counterflow CF.

In accordance with the present invention, several operational features arise from the design of the swirler 47 and the sidewall profile. First, the surface of sidewall 61 exhibits relatively little or low drag due to its design as a stream surface. Secondly, the swirler 47 generates a low pressure area, which can be largely attributed to a rarefaction near the throat 57 generated by focused air rotation about axis ZZ. A strong suction is generated at the throat 57 which draws hot flue gases passing in front of the swirler 47 and the local circulation zone LCR. This suction creates a hot counter flow-CF toward the throat 57. As FIGS. 4A and 6 reveal, the counter flow CF occupies a wide area (diameter) across the cone 51, which is indicative of the strength of the suction created by the swirler 47 and allowed by the angle θ of the sidewall 61. The strong suction and resulting counterflow CF may also cause fuel droplets to flow into back into the throat 87 and potentially past the nozzle tip 63. To guard against escape and possible deposit of these counterflowing fuel droplets, air flow A2 is directed through the annular gap 59 to engage and divert the counter flow CF thereabout.

Furthermore, because the swirling jet outflow A3 is pressed to the diverging part of the sidewall 61 by centrifugal force, there is little swirl in the center and in the hot flue gas counter flows CF. With reference again to the diagram of FIG. 6, the counterflow CF efficiently transports hot flue gases to the throat 57 and the tip 63 of the nozzle 49. The hot flue gases heat fuel emitted by the fuel nozzle 49 into the region between the swirl axis ZZ and the dotted line in FIG. 8B. The hot flue gas also heats the air flow A3, help evaporate liquid fuel droplets and initiate combustion near the nozzle tip 63. The counterflows CF also decelerate the travel of the sprayed droplets, which increases their residence time in the hot environment and facilitates evaporation. Also, since swirl is nearly absent in the spray region, the droplets are not rapidly driven to the sidewall by centrifugal force and, therefore, do not deposit on the sidewall. Finally, the stagnant annular region separating the near-sidewall outflow and the near-axis inflow serves effectively as a flame holder providing stable moderate-temperature combustion.

In operation, the combustion apparatus 7 according to the invention initiates a combustion process with multiple advantageous features. In one aspect of the invention, such a combustion method is achieved utilizing a single combustion chamber for flameless combustion.

In a further aspect, a method of combustion according to the invention involves the advantageous high-speed circulation of combustion fluids (air, fuel, and/or fuel-air mixture) inside the combustion chamber. More specifically, preferable operation of the combustion apparatus 7, according to the invention, establishes dual modes of circulation or fluid flow: a first mode entailing the revolution of fluid particles around the longitudinal axis YY (swirl) and a second mode entailing circulatory meridional motion of the combustion fluids. As described below, this dual mode of circulation enhances the mixing of air and fuel in the combustion chamber and helps achieve desired combustion characteristics and temperature profiles.

Advantageous Circulation in the Combustion Chamber

The simplified schematic of FIG. 7 illustrates the axial and circular flows (of air, fuel, other combustion constituents, and their mixtures) generated in the combustion chamber 33 according to the present invention. More particularly, FIG. 7 reveals two types of global axial flows induced in the combustion apparatus 7 according to the invention: circulatory flows generally centered about circulatory regions CR and flow-through (flows) in the flow-through regions FT, which exit the chamber 33 as exhaust. As discussed below in respect to FIG. 7A, the circulatory meridional motion in the combustion chamber 33 is initiated by centrifugal convection. Pressurized air introduced into the chamber 33 is cooler than the interior part of the chamber 33. As this incoming air flows near the sidewall 35, its temperature increases and approaches the flue gas temperature. An axial temperature gradient is therefore provided along the sidewall 35. This temperature gradient combines with swirl flow about the axis YY to drive meridional circulation within the chamber 33 (even with no flow-through). This driving mechanism further combines with the effect of combustion in the chamber 33 and flow-through (discussed further below) to induce high-speed circulatory flows within the chamber 33.

Additionally, the applicants utilize the contribution of swirl-decay mechanisms in generating counter-flows (i.e., both the circulation and the U-shape flow-through, in the combustion chamber). Generally, air-sidewall friction causes a pressure drop in the air flow in the axial direction. Thus, the pressure at air inlet 43 is significantly higher than the pressure at the end of axial flow travel, near the proximal end wall 37. Pressure is also lower at the swirl vortex. Thus, pressure near the sidewall 35 at the proximal end is significantly greater than the pressure at the axis YY (the swirl axis) near the proximal end wall 37. Finally, the pressure at the axis YY near the distal end wall 39 is greater than the pressure at the axis YY at the proximal end wall 37. This is primarily due to the swirl rotational speed having decreased along the axial length of the sidewall 35 friction and effecting less of a pressure drop at the proximal end. The above-described pressure gradients help drive the meridional motion and in particular, the advantageous turns and reverse flows made by fluid flow in the combustion chamber 33. These pressure gradients and swirl decay effects are also utilized in the embodiments of the present invention through strategic arrangement of the tangential and axial air inlets, as described below.

Referring first to the schematic of FIG. 7, high-pressure fresh air A0 enters the combustion chamber 33 through the air inlet 43. Because the air inlet 43 is positioned tangentially to the sidewall 35 of the cylindrical combustion liner 33, the high velocity air inflow A0 into the cylindrical chamber 33 is directed tangentially near the inside surface of the sidewall 15 35 and generally transverse to the longitudinal axis YY. This high velocity tangential inflow A0 induces and drives a swirling motion (illustrated in FIG. 8) of the air particles about the chamber axis YY. In preferred methods utilizing the combustion apparatus 7 of FIGS. 1-5, this air inflow A0 is presented at an axial location physically near the exhaust opening 25 and exhaust flow E0 of the chamber 33. The desired swirl about the longitudinal axis YY also commences at this near-exhaust axial location. Notably, the direct path between the air inlet opening 43 and the exhaust opening 25 is relatively short—well below the value of the diameter of the chamber 33 and possibly, slightly longer than its radius. This direct path is described as being a “clear direct path” (i.e., free of any structural barrier obstructing or diverting a direct flow path), as opposed to an obstructed path (i.e., characterized by a combustion exhaust tube, baffle, or other structural barrier physically separating the pressurized air inflow from the exhaust flow).

The fresh air inflow A0 has, of course, a temperature that is significantly less than that of the gases already inside the chamber 33, especially the hot flue gases. Thus, the constituents of this fresh air inflow A0 generally are of a higher density than the hot gases and other combustion particulates. In the combustion chamber 33 of the invention, centrifugal buoyancy and centrifugal force act to push the higher-density air radially outward. The effect of centrifugal acceleration on the air particles may be larger than that of gravitational acceleration by four to five orders of magnitude. As a result, even a small difference in temperature (and therefore in density) causes stratification (until mixing and combustion together heat the incoming flow up to the flue gas temperature in the circulation regions CR). Since most of the incoming air initially flows in a thin, annular layer close to the sidewall 35, its axial velocity is low compared with that of the existing circulatory flows and the central flow-through. The maximum axial velocity of the near-sidewall flow is estimated to be around one third of that of the near-axis flow. The relatively low axial velocity of the near-sidewall air flow increases its residence time, however, and thus, provides sufficient time for the preheating, mixing and combustion of air. In preferred embodiments, the residence time of the near sidewall air flow may be higher than the mixing time by orders of magnitude, and its combustion time smaller than the mixing time.

Returning to FIG. 7, the swirling air inflow A0 generally advances from the air inlet 43 (the “cold” side of the combustion chamber 33) to the proximal end wall 37 of the combustion chamber 33 (the “hot” side of the combustion chamber 33) primarily due to centrifugal convection. The flow lines in FIG. 7A isolate and illustrate the meridional motion or circulation of the fluid mixture (air and fuel) inside the combustion chamber 33. The flow streams or flow lines are substantially symmetric about axis YY in all directions and thus, only a one-half section of the chamber 33 is represented. As mentioned above, the flow lines A0 advancing from the air inlet 43 are concentrated along the sidewall 35, well away from the center of the combustion chamber 33. Upon reaching the region of the proximal end wall 37, the flow lines turn radially 20 inward toward the axis YY and into the proximity of the fuel-air mixture delivery system 45. From there, the flow lines again turn about ninety degrees into the axial direction of the exhaust 25, thereby completing a U-turn. In this return air flow, the flow lines are directed generally centrally in the combustion chamber 33 and alongside longitudinal axis YY.

As shown in FIG. 7A, the returning air flow along the longitudinal axis YY takes two different paths. A portion of the returning flow flows through and out of the combustion chamber (via the exhaust 25). This flow-through portion FT is situated near the axis YY of the combustion chamber 33, and in general axial alignment with the exhaust 25. Another portion of the return flow is situated radially outward of the flow-through portion FT, but also directed axially toward the exhaust 25. Before reaching the exhaust 25, the flow lines of this portion turn 90 degrees and head radially outward. Then, before reaching the sidewall 35, this outward flow again turns 90 degrees (a second U-turn) and in the opposite axial direction, while engaging the freshly incoming pressurized air flow A0 into the combustion chamber 33. As shown in FIG. 7A, the returning flow lines are situated radially inward of the sidewall 35 and the freshly incoming pressurized air A0 that flow along the sidewall 35. These flow lines, which are again directed axially toward the “hot” side of the chamber 33, represent full circulation of gases in the combustion chamber 33. The region or pattern defined by this meridional circulation is referred to herein as the circulatory region CR. As shown in FIG. 7, two circulating regions CR are established during operation of the combustion apparatus 7.

The high-speed circulatory flows generally consist of hot flue gases moving in the circumferential, axial, and radial directions. Notably, the circulatory flows are located downstream of the swirler 47 and the nozzle 49. The nozzle and swirler arrangement and orientation provide for the injection of atomized fuel into the circulatory region CR. Droplets of liquid fuel introduced into the region CR will evaporate quickly upon contact with the hot flow. Gaseous fuel introduced into the region CR, on the other hand, will be quickly preheated and mixed by the hot, high-speed and turbulent flow.

In one aspect of the present invention, the circular flow described above and illustrated in FIGS. 7 and 7A interacts advantageously with the freshly entering inflow A0 of pressurized air. As the freshly entering air advances along the sidewall 35, this incoming air is heated through contact and mixing with the hotter flue gases that are moving in the circulatory regions CR. Fuel droplets injected by the fuel nozzle 49 enter the hot flue gas region, revolve about the axis YY, and are also pushed toward the sidewall 35 by centrifugal force. As the droplets move toward the sidewall 35, flue gases in the circulatory region CR heat and then cause the droplets to begin to evaporate. As the preheated air and fuel meet near the sidewall 35, combustion commences. The resulting overheated combustion products move toward the chamber axis YY driven by centrifugal buoyancy. These fresh combustion products mix with and heat the flue gases in the circulatory region CR. A portion of the flue gases travel along the longitudinal axis YY to the exhaust 25, while the rest of the flue gases continue the circulatory motion described above.

The direction of cooler incoming air flows along the sidewalls 35 provide yet another benefit. The cooler air flow provides a buffer between the combustion region and the sidewalls and end walls of the liner 31, and helps to maintain the sidewalls 35 at cooler temperatures. Such thermal protection allows for the use of lower-cost material for the sidewall 35 and typically results in a more double and longer lasting sidewall 35.

FIG. 7A also represents the results of numerical simulations of the circular flow schematically shown in FIG. 7. More specifically, FIG. 7A illustrates the analytical solution of the Navier-Stokes equations for a compressible ideal gas. This solution describes a flow in a rotating cylindrical container, in which wall temperature varies in the axial direction. As described above, the gas swirls around the axis, advances along the sidewall 35 from the cold end wall 39′ to the hot end wall 37′, turns toward the axis YY near the hot end wall 37′, flows along the axis YY to the cold wall 39′, and then turns outward to the sidewall 35′ near the cold end wall 39′. The flow described, which incorporates both swirl around the axis YY and meridional circulation, is referred to as centrifugal convection. During operation, swirl and an axial temperature gradient are also generated in the combustion chamber 33 of the present invention. Accordingly, centrifugal convection is induced inside the combustion chamber 33, particularly, inside the circulatory regions CR schematically shown in FIG. 7. The advanced solution also describes the additional swirl decay mechanism of the circulation flow and takes into account effects of the inflow and the exhaust in the combustor.

Double Spiral Swirl Promotes Fast and Fine Mixing throughout

In a further aspect of the invention, swirl generated in the combustion chamber 33 is characterized by an advantageous double-spiral geometric pattern. FIGS. 8A-8E provides three dimensional views of air and flue gas particle trajectories induced in the combustion chamber 33, according to the present invention. Trajectories Ta, Tb, and Tc follow particles moving inside one of the circulation regions CR. In more detail, trajectory Ta follows a particle moving close to the center of the circulation region CR (see the inner closed curve Si in FIG. 7A) while trajectory Tc follows a particle moving along the circulation region CR boundary. Trajectory Tb follows a particle moving between trajectories Ta and Tc. The other trajectories, Td and Te, are associated with particles moving in the flow-through region FT. Trajectory Td follows a particle moving in the flow-through region FT, but close to the circulation region CR. Trajectory Te, on the other hand, follows a particle initially moving close to the sidewall 35 of the combustion chamber 33 and then along the longitudinal axis YY toward the exhaust 25.

For each of the trajectories in FIG. 8, an outer spiral So is established near the sidewall 35 while an inner spiral Si is established radially inward of the outer spiral So and closer to the axis YY. The wavy and counter-flowing motion provided by this double-spiral geometry promotes fast and fine mixing of air, fuel, and flue gas throughout the entire combustion chamber, thereby enhancing volume-distributed oxidation. Temperature readings at various remote locations in the combustion chamber 33 revealed fairly well uniform temperature distributions throughout the chamber 33. This is further indication that the dual mode of circulation according to the present invention achieves efficient mixing of fluids in the combustion chamber during operation.

Comparison of trajectories Td and Te also reveals that a particle moving close to the sidewall, (e), makes more revolutions around the axis YY than the particle remote from the sidewall, (d). The particle close to the sidewall 35 has, therefore, a lower axial velocity than that the one remote from the sidewall 35. Furthermore, the particle close to the sidewall 35 has a longer residence time in the combustion chamber 33 than the particle remote from the sidewall 35. As centrifugal stratification provides that the colder particles will be closer to the sidewall 35 than the hotter particles, the cold particles are provided sufficient time to heat up. Moving slowly along the sidewall 35, the cold particles are continually heated by the hot sidewall 35, by the hotter flue gases with which it mixes, and finally due to heat from combustion. Trajectory (e) in FIG. 8, which is typical for initially cold particles, shows that a cold particle spends more than 90% of its residence time moving along the sidewall 35 and near the end wall 37. (Note also that the axial length of preferred combustion chambers is longer than its diameter (elongated combustion chambers), and often substantially longer). The particle's travel along the axis YY (between end walls 37, 39) takes less than 10% of its residence time. Keeping in mind such behavior of the flow particles, an alternative embodiment of the combustion chamber is provided and described below.

Volume Dominance and High-Speed Circulatory Flows

An important feature revealed in FIGS. 7 and 7A is a circulatory region CR that occupies about ⅔ of the volume of the combustion chamber 33. The flow-through region F0 occupies only the remaining ⅓ of the chamber volume. Such volume dominance by the circulatory flow makes the combustion stable even for a high-speed flow-through. Applicants have observed, for example, a stable combustion at an incoming air velocity exceeding 200 m/s.

The volume dominance and high-speed motion of the circulatory flows provide intense and fine mixing of incoming air with flue gases. The circulatory flows quickly heat up the incoming air up to the self-ignition temperature. The volume dominance and high temperature of the circulatory flows also provide intense preheating and evaporation (for liquids) of fuel injected by the nozzle 49 into the circulatory flow regions CR. The fast and fine mixing results in uniform distribution of both fuel and air in the entire combustion chamber volume. Therefore the fuel and air meet and combust everywhere in the chamber 33, i.e., volume-distributed oxidizing occurs.

The volume dominance, high speed and high temperature of the circulatory flows also help to establish the circulatory regions CR as safe and efficient flame holders. Because the flow-through regions FT is pressed proximate the combustor sidewall 35 by centrifugal force and centrifugal buoyancy, the flow-through streams cannot readily cause blow-out and/or cool down the circulatory flows. Furthermore, combustion uniformly heats all of the constituents throughout the chamber 33 due to intense mixing and, in particular, maintains the circulatory flow at high temperature. Combustion also causes the through-flow and circulation flows to accelerate and thus, maintain the circulatory flows at high-speed.

FIGS. 7 and 7A also illustrate that, near the exhaust 25 and distal end wall 39, the circulatory flow is turned outward to the sidewall 35. This counter flow blocks what would otherwise have been a short-cut passage of entering air flow A0 directly to the exhaust 25. This flow feature acts in conjunction with centrifugal force to push the higher-density incoming air flow A0 toward the sidewall 35. In one respect, these flow features provide the flow barrier function exhibited by the combustion exhaust conduit discussed above. The results are that the flow lines are longer, the residence time for air-fuel mixtures in the combustion chamber are longer, and a more complete combustion is assured.

Alternate Combustion Apparatus and Methods

FIG. 9 is an operational schematic representing operation of a combustion apparatus 107 in accordance with an alternative embodiment of the invention, wherein like reference numerals are used to indicate like elements. Operation of the combustion apparatus 107 provides many of the same advantages that are available with the earlier-described combustion apparatus 7 of FIGS. 1-5. The configuration of the elongated combustion apparatus 107 is substantially similar to that of the combustion apparatus of FIGS. 1-5, except for one structural variation: the provision of an air inlet 171 into the cylindrical combustion liner 131 adjacent the proximal end wall 137. In contrast to the earlier described embodiment, the air inlet 171 is located remotely from the chamber exhaust 125. As with the earlier embodiment, the air inlet 171 is positioned and configured to direct fresh air inflow A0 tangentially into the cylindrical chamber 133. The fuel-air mixture delivery system 145 and flue gas exhaust 125 are located substantially axially on opposite sides of the chamber 133. As before, operation of the combustion apparatus 107 generates dual modes of circulation in the chamber: swirl about the longitudinal axis YY and meridional motion.

FIG. 9 also illustrates the meridional motion of the fluid flows in the combustion chamber 107 during operation. Noting the influence of swirl decay mechanisms, the initial inflow A0, while drawn along the sidewall 135, travels from the proximal side of the chamber 133 to the distal or exhaust side of the chamber 133 and gradually decreases in swirl velocity. At the distal end wall 139, the flow lines turn inwardly toward the axis YY (region of low pressure). Then, some of the flow lines turn and are directed in the reverse axial direction toward the proximal end wall 137. Some flow lines go out as flue gas exhaust E0 through the exhaust opening 125. Notably, the flow-through flow lines (and flow-through regions, FT) are found along the side wall 135 and along the distal end wall 139. Unlike operation of the earlier described combustion apparatus 7, the central core region near and about the axis YY in this embodiment is not occupied by flow-through flow lines, but by circulating flow lines (and circulating regions, CR).

As compared with operation of the earlier-described combustion apparatus 7, operation of this combustor 107 features a shorter passage length (the flow-through flow line from the air inlet 171 to the exhaust 25). Accordingly, the residence time of the particle in the flow-through line is shorter. Seemingly, this feature would present a significant performance disadvantage, especially considering the benefits provided by longer residence times as explained above in respect to the combustion apparatus 7 of FIGS. 1-5. This alternate design does, however, provide its own unique and advantageous feature. As shown in FIG. 9, operation of the combustion apparatus 107 generates a larger circulation region CR than the earlier-described combustion apparatus 7. Now including the core region about the axis YY, the larger circulation region CR occupies an even greater volume of the combustion chamber 133.

FIG. 9A provides a representation of the numerical flow simulations schematically shown in FIG. 9 (similar to that provided by FIG. 7A). The simulations reveal circulatory regions CR inside the combustion chamber 133 that occupy about ¾ of the interior volume, while the flowthrough region FT now occupies only about ¼ of the interior volume. The increased dominance of the circulatory flow results in a higher volume-averaged temperature. Therefore, more thermal energy is available for heating water and other diluting species in low-grade fuels. This makes the combustor design illustrated in FIG. 9 well suited for burning low-grade fuels, such as glycerol.

FIG. 10 depicts a simplified schematic of yet another embodiment of a combustion apparatus according to the invention. In this schematic, only one-half of the combustion apparatus 207 and a combustion chamber 233 is represented. The combustion apparatus 207 is equipped with two tangential air inlets 243a, 243b located at opposite axial ends of the combustion chamber 233. High pressure, high velocity air enters the chamber 23 at each inlet 243. Both air inflows A1, A2 travel near the sidewall 235, with the air inflow A1 at the exhaust end moving toward the proximal end and the air inflow A2 at the proximal end moving, in the opposite direction, toward the distal or exhaust end. Midway across the axial length of the chamber 233, the two air flows A1, A2 collide, mix, and then turn inward toward the chamber axis YY. Near the axis YY, the resulting air flow turns again and advances toward the exhaust 225.

FIG. 10A represents the results of numerical simulations of the internal flows inside the combustion apparatus 207 during operation, similar to FIG. 7A in respect to the combustion apparatus 7 of FIGS. 1-5. Operation of the combustion apparatus 207 reveals two circulatory regions, CR1 and CR2, with beneficial features similar to those circulatory regions CR described above. One of the circulatory flows or regions, CR1, is located in a dilution zone, while the other, CR2, is located in the combustion zone. The enhanced mixing in the combustion zone helps provide stable and low-emission combustion. The enhanced mixing in the dilution zone helps finalize and complete the combustion of fuel rendering species concentrations in the exhaust flow more uniform.

The provision of a second inlet 243b near the proximal end wall 237 advantageously provides for a higher speed, cooler flow-through at the “hot” proximal end. The local circulation region LCR and combustion zone are present at the proximal end. In the previous configuration, the sidewall 235 at the proximal end experiences higher temperatures due to its proximity to the combustion zone and also, because the inlet air flow A0 gets hotter and slows as it travels axially along the sidewall 35 before arriving at the proximal end. The higher speed, cooler air inflow A2 provides a more effective cooling fluid flow. Additionally, the addition of higher speed swirl flow near and in contact with the local circulation zone LCR and near the fuel spray from the nozzle 149 enhances mixing and heating of combustion constituents. More particularly, the addition of higher speed swirl flow at the proximal end helps to generate counter-flows (flows in opposite directions), thereby promoting the occurrence of swirling vortices and Karman eddies. These eddies facilitate the desired fast and fine mixing of combustion constituents.

Burner

The simplified illustration of FIG. 11 provides an alternative combustion apparatus according to an alternative embodiment of the invention. The combustion apparatus in this embodiment is in the form of a burner 307. The burner 307 utilizes a fuel-air delivery system 345 that is substantially similar to the system 145 described in respect to FIGS. 3-6. In this application, the burner 307 is not confined within a combustion liner and does not exhausts into a transition piece, turbine, or other device. The burner 307 is particularly suited for use in direct heating applications.

As before, the fuel-air delivery system 345 includes a fuel nozzle 349, a radial air swirler 347, and a swirler nozzle or cone 351 extending forwardly along a swirler axis ZZ. The cone 351 further includes a divergent sidewall 361 having an advantageous profile as described previously. In this alternate configuration, the air swirler 347 and fuel nozzle 349 are supported within a casing 381. More specifically, the swirler 347 is mounted on the inside wall of a flange or backplate 383, such that the cone 351 extends outward through a central opening of the backplate 383. As second backplate 385 encloses the casing 381 to define an air chamber 385. As shown in FIG. 11, an air inlet 387 extends through the casing 381 to supply pressurized air to the air chamber 385.

During operation, an air inflow A1 is drawn by radial guide vanes 355 of the swirler 347. The guide vanes 355 generate a high speed rotational internal flow that converges on the center of the swirler 347 and advances forwardly therefrom into a throat 357 of the swirler 347 and along the divergent sidewall 361 of the cone 351 (as discussed previously). Additional air flow A2 is drawn through an annular gap 359 around the nozzle 349 and passed into the throat 385 to engage any counter flowing fuel droplets drawn back into the swirler 347 or throat 385. As also described earlier, a jet-like air swirl flow A3 generated by the swirler 347 is pressed thinly and annularly against the sidewall 361, while and fuel spray is directed outwardly by the nozzle 349 from the area of the throat 385. Advantageously, the angle of the fuel spray is designed to be less than that of the sidewall 361 so that the thin jet-like layer of air swirl A3 near the sidewall 361 is clear from the extent of the fuel spray.

As illustrated in FIG. 11, the fuel-air delivery system 345 generates a local circulation region LCR in front of the cone 351. The local circulation region LCR is characterized by hot gas counterflow CF and eddies generated by oppositely-directed (counter) flows. Accordingly, the local circulation region LCR provides fast and fine mixing of air, fuel, and species concentrations.

The simplified schematic of FIG. 12 illustrates yet another single-chamber combustion apparatus 407 according to the present invention, and the beneficial modes of circulation generated therein. In this variation, the combustion apparatus 407 includes a combustor liner 431 that is fitted with a diaphragm 477. The diaphragm 477 is essentially formed by the introduction of circumferential baffles 479 in the combustion chamber 433 and at a desired axial distance from the proximal end wall 437 (of the combustion chamber 433). An additional end wall 479 is added rearward of the proximal end wall 437 to create a cylindrical air space 409 dedicated to the fuel-air delivery system 445. The diaphragm 477 separates the combustion chamber 433 into a main combustion chamber 433a and a pre-chamber 433b. The fuel-air delivery system 445 is positioned to extend and direct primary air and fuel spray into the prechamber 433b.

In this embodiment, the combustor liner 431 is equipped with two pressurized air inlets 443. A tangential air inlet 443a is located near the exhaust 425 as before and a second tangential or radial air inlet 443b is located in the cylindrical air space 409. This second air inlet 443b supplies primary air A1 to the fuel-air delivery system 445. Independent of the first air inlet 443a, this dedicated inlet 443a may be equipped with the required valves and controls to allow independent regulation of the primary air A1 feed to the delivery system 445. Specifically, the primary air fed to the swirler 447 may be controlled directly and independently of the air inflow A0 utilized in the combustion chamber 433.

During operation, the combustion apparatus 407 generates, in addition to swirl about the longitudinal axis YY, global meridional circulation similar to that described in respect to combustion apparatus 407. An additional or local meridional circulation is also generated, however, local to the pre-chamber 433b. As illustrated in FIG. 11, a portion of the flow along the distal side of the baffles 479 in the main combustion chamber 433a is diverted into the prechamber 433b to form circular flow (or counterflow) region CR2. This circulatory region CR2 helps cool the prechamber 433b and advantageously interacts with local circulation regions LCR. Furthermore, the counterflow presented by this circulatory region CR2 helps in drawing hot flue gases into the local circulation regions CR2 and creating the desired counterflow CF therein. The counterflow also help to generate Karman eddies, which, as discussed previously, helps promote fast and fine mixing of combustion constituents.

The diaphragm 477 also helps to minimize the effect of increased air inflow A0 on the local circulation regions LCR. In particular, the baffles 479 help to mitigate the effects of higher inflows and prevent blow out in the local circulation region LCR. Accordingly, modes of operation requiring higher rate of air inflows may be achieved by the combustor 407 without compromising the performance of the fuel-air delivery systems 445 and local circulation regions LCR. FIGS. 13-14 depict yet another combustion apparatus 507 according to an embodiment of the present invention. The combustion apparatus 507 employs many of the same components and provide many of the same operational features as earlier described embodiments. Referring first to FIGS. 13A-13D, the combustion apparatus 507 includes an outer housing 513 having a proximal end wall 517 and a distal or exhaust end 519, both of which are preferably aligned about a longitudinal axis YY. As best shown in FIGS. 13A and 13B, a cylindrical air duct or casing 589 wraps about the outer housing 513 near the exhaust end. The casing 589 further includes an air inlet pipe 527 for delivering high pressure air from an external compressor or equal. The outer housing 513 is preferably a cylindrical body with flanged proximal and distal ends. As described in earlier embodiments, the proximal end generally provides receipt of a fuel supply while the distal or exhaust end communicates hot flue gases to a turbine or other required component. The outer housing 513 in this embodiment receives five individual fuel supply pipes 521 at the proximal end wall 517. Four of the fuel pipes are equally spaced from and surrounds the fifth fuel pipe 521, which is preferably centered about the axis YY.

The combustion apparatus 507 further includes a cylindrical combustor liner 531 and a slightly conical transition piece 587 attached to the combustor liner 531. As shown in FIG. 13D, the transition piece 587 is positioned about the longitudinal axis YY and attached to a distal end wall 539 of the combustor liner 531. The transition piece 587 is equipped with a conical end wall 599 situated at the open end to direct exhaust gases to an annular exhaust opening 599a. The combustor liner 531 is sized relative to the outer housing 513 to create a gap or annulus 541 therebetween. As shown, for example, by FIG. 13D, the annulus 541 extends from the transition piece 587 all the way to the proximal end wall 517. The air inlet casing 589 communicates with the annulus 541 to supply pressurized air throughout the extent of the annulus 541 and about both the liner 531 and the transition piece 587. Referring now to FIG. 14A-14C, the combustor liner 531 has a substantially closed proximal end wall 537, a substantially open distal or exhaust end wall 539, and a sidewall 535 extending axially 10 therebetween. The sidewall 531 defines, at least partly, a cylindrical combustion chamber 533, according to the present invention. The combustor liner 531, in this variation of the invention, is equipped with a pair of circumferential air inlets 543a, 543b, as opposed to a single opening in the sidewall 531. The air inlet openings 543a, 543b are provided by plurality of radial guide vanes 593 circumferentially positioned about the proximal and distal ends of the combustor liner 531. A first air inlet 543a is positioned near the chamber exhaust 525, as with previously described embodiments. The second air inlet 543b is positioned near the proximal end wall 537.

As shown in the Figures, the two air inlets 543a, 543b may have substantially the same configuration. Each air inlet 543a, 543b provides a set of radial guide vanes 593 arranged about the periphery, with each vane being positioned angularly to direct swirling air flow tangentially (not radially) into the combustion chamber 533. The configurations of the two air inlets 543a, 543b differ, however, in that the direction of the guide vanes 593 for one inlet is generally clockwise while those of the other inlet are counter-clockwise. Thus, the directions of tangential air flows downstream of the air inlets 543a, 543b and the swirl flows about axis YY generated thereby, are also in opposite rotational directions (clockwise or counter clockwise) and will collide and mix midway across the sidewall 535.

FIGS. 14A-14C also show a backplate or flange 595 placed adjacent the proximal side of the circumferential air inlet 543b. The backplate 595 conveniently provides support for a fuel-air mixture delivery system 545′ of the combustion apparatus 507. In a further aspect of the present invention, the fuel-air delivery system 545′ actually includes five separate fuel-air mixture delivery systems 545 or, put in another way, five separate air swirler 547-fuel nozzle 549 combinations for directing the desired fuel and air into the combustion zone. Individually, each of the delivery systems 545 is configured substantially the same as the fuel-air delivery system 45 described in respect to the combustion apparatus 7 of FIGS. 1-3. Each fuel-air delivery system 545 includes a swirler 54 having a swirler nozzle or cone 551 extending into the combustion chamber 533 and a fuel nozzle 549 extending through the air swirler 547 to a throat 557 or within the cone 551. As best shown in FIG. 14D, in a preferred arrangement, a first delivery system 545 is situated centrally on the back plate 595 and generally about the longitudinal axis YY. The remaining four delivery systems 545 are spaced outward from and about the first delivery system 545 (this also determines the relative positions of the cone 551 and local circulation regions LCR generated in the combustion chamber 533). As shown in the side views of FIGS. 14B and 14C, the first or center delivery system 545 is preferably raised from the back plate 595, so as to extend axially rearward of the other four delivery systems 545. In this way, the swirler 547 of the center delivery system 545 is exposed to primary air flow from the annulus 541 (and not blocked by the other swirlers 547).

In this embodiment, two igniters 597 are provided and positioned on either side of the center fuel-air delivery systems 545. The igniters 597 extend into the combustion chamber 533 at an axial position proximate the rim of the cones 551. As discussed previously in respect to the fuel-air delivery system 145, each of the systems 545 generates a local circulation region LCR in front of and within each cone 551 (see e.g., FIGS. 4A and 6). Each of the local circulation regions LCR has the features and properties discussed previously in respect to FIGS. 4A and 6. Among other things, the local circulation regions LCR provide effective flame holders and quickly heats and/or evaporizes fuel injected by the nozzle 549.

The simplified flow representations (and their discussion) in FIGS. 10 and 10a are applicable and indicative of the flows and meridional motion that are induced in the combustion chamber 533 of this embodiment. The unique configuration of the combustion apparatus 507 translates to beneficial features in the flows in the combustion chamber 533.

During operation of the combustion apparatus, the combustion chamber 533 features two annular regions of high speed axial flow. The first is an annular region near the liner sidewall 535 and the other is located near the axis YY. These two regions of high speed flow is separated by an annular region of counterflow (in the portion of the chamber 533 near the fuel-air delivery system 545) or by lower-speed co-flow (near the middle of the chamber 533). In addition, the similar counterflow and the low-speed co-flow are located near the axis YY. The instability of this complex flow, having multiple shear layers, generates turbulent Karmantype eddies densely packed throughout entire combustion chamber 533. The presence of largescale eddies and small-scale turbulence result yet again in fast and fine mixing of air, fuel, and flue gases, thereby promoting stable and complete combustion with low level of harmful emission. FIGS. 15A and 15B are provided to illustrate the additional and enhance flow dynamics generated by the multiple swirler configuration of FIGS. 14 and 15. In particular, the utilization of multiple fuel-air mixture delivery systems 545 translates to multiple local circulation regions LCR and multiple regions of counterflows CF. As discussed above, the presence of counterflows CF in the operation of this combustor apparatus 507 provide for the desirable generation of swirl vortices or fine scale Karman vortices. Specifically, these vortices Vx are generated in the transition regions between counterflow CF.

FIG. 15A is front plan view of the area of the fuel delivery system 545′ near the proximal end of the combustion chamber 533. As shown, a thin jet-like air flow A3 is directed outward on the divergent sidewall 561 of the swirler cone 551. This high speed swirling flows A3 are characteristic of each of the local circulation regions LCR, and are present near the periphery of the region LCR. The peripheries of the various local circulation zones LCR encroach on other peripheries, in respect to the central fuel-air delivery system 545 and each of the four surrounding fuel-air mixture delivery systems 545. Thus, there exist counter flowing swirling air flows A3, and in the transition region between these, desirable vortices Vx form (as shown in FIG. 15A).

Now turning to the side or profile view of FIG. 15B, swirl vortices Vx in the longitudinal planes are also generated. As mentioned previously in respect to FIG. 4A, the hot flue gas counterflows CF are directed back to the area of the fuel nozzle 549, while the thin jetlike swirling air flow A3 presses forwardly along the divergent sidewall 561. Furthermore, the counterflow CF drawn toward the nozzle 549 also reverse direction and flow outward at certain places. Thus, there are transition regions in and near the region of the cone 551 at which inward flow and outward flow are found. Fine scale Karman vortices are advantageously developed in these transition regions.

As further shown in FIG. 15B, there are transition regions outside of the cone 551 and/or the local circulation regions LCR. Outward flows necessarily extend out of or escape these regions. As discussed throughout this disclosure, organized axial flows are generated in the combustion chamber 533. Some of these axial flows are found in or near the proximal end and meet or flow aside the outward flows. Transition regions and Karman vortices occur, for example, near the sidewall 535 and axially forward of the cones 551.

Thus, in a preferred combustion apparatus and method of combustion according to the invention, a combustion liner is provided having at least one air injection inlet tangentially positioned to induce high-speed swirl about the chamber axis. The combustion liner is further configured, and the inlet port(s) is properly positioned, so as to induce a desired high-speed meridional motion inside the chamber. Relatively large circular flow regions are generated and interact with flow-through regions, which include regions along the sidewalls. More preferably, at least one air-fuel swirler is provided for generating a narrow annular jet and a wide suction flow. The resulting multiple shear layers, densely packed Karman-type eddies, fine-scale turbulence, and particle trajectories of double-spiral geometry cause fast and fine mixing of air, fuel and flue gases as well as extremely uniform temperature distribution. The large circulation/flow-through volume ratio and high-speed circulation provide stable combustion, rapid preheating and mixing of injected fuel, and uniformly occurring oxidation in the entire combustion chamber or combustion liner volume at optimal temperature with minimum harmful emission.

FIG. 16A provides an exhaust end view of an alternate combustion apparatus 607, according to the invention The combustion apparatus 607 of this embodiment employs an arrangement of four circumferentially spaced-apart air inlet pipes 627 (for pressurized air supply) that communicate with a housing 613. The housing 613 extends over a transition piece 687 and is spaced therefrom by way of annulus or gap 641. Pressurized air entering the annulus 641 reaches, therefore, the outside of the transition piece 687 (in addition to the combustion chamber and the outside of the liner).

The transition piece 687 is provided for engagement with a turbine or other suitable mechanism. The transition piece 687 has a diameter that increases gradually from the end at which it engages a combustion liner 631 and receives exhaust gases, to an exhaust opening 605 downstream. As shown in FIG. 16B, the front of the transition piece 687 is substantially occupied by a hollow conical end wall 699 (and a cap 673 spaced just axially inward of the end wall 699). The end wall 699 is sized smaller than the housing 613, so that a circumferential gap 671 is provided therebetween. The gap 671 presents an annular exhaust opening 671 for the escape of combustion chamber exhaust gases. Because of its location in the direct path of hot exhaust gases, the end wall 699 may be exposed to and experience extremely high temperatures. Accordingly, in some applications, the end wall 699 may be made of or supplemented with materials capable of withstanding high heat conditions. In one aspect of the invention, the combustor apparatus 607 is equipped with an integrated cooling system for reducing the effect of high temperatures on the end wall 699 and other components of the transition piece 687.

In this embodiment, the hollow end wall 699 is configured with an interior hollow or cavity 675. At about the axis YY, an axially extending port 677 is provided from the cavity 675 to the outside of the end wall 699 (inside of the transition piece 687). The cap 673 is attached to the end wall 699 by a short rod 685 (near the port 677) and is centered on the axis YY.

Furthermore, the end wall 699 is supported in place by four short tubes 695 that extend from the housing 613. The tubes 695, which are open to the annulus 641 on one end and the cavity 675 on the other end, communicate relatively cool air from the annulus 641 to the end wall 699. Air flow directed into the cavity 675 converge on the axis YY and then exit through the port 677. The pressurized air spills into the annular gap between the cap 673 and the end wall 699, and then deflected by the cap 673. From there, the deflected air flow moves outward to the exhaust opening 671 along the inside surface of the end wall 699. In this way, air flow convectively cools the outside, as well as the inside, of the end wall 699.

In one aspect of an invention provided in the present disclosure, a combustor features a single combustion chamber that receives fuel and air (or other oxidizer) and initiates combustion. More specifically, the combustor employs a combustion container having an elongated combustion chamber and a tangential air inlet into the chamber that induces swirl about the chamber axis and meridional circulation, thereby effecting advantageous mixing and preheating. Furthermore, the combustion container is preferably configured such that the tangential air inlet is located proximate the chamber's exhaust (without any structural barriers directly between the inlet and the exhaust). FIG. 17A provides a simplified representation of such a combustion container (with indications of swirl flow omitted). Key structural elements represented and noted in the Figure include: a single, elongated combustion chamber; a tangential air inlet (for swirl); and the air inlet is proximate the exhaust.

An important additional element of a preferred combustor's design is the inclusion or incorporation of a casing that substantially encloses the container but is spaced outwardly from the combustion container to create a gap or annulus. This annulus serves to divert and direct air flow about the outside of the combustion container and\or to a fuel-air delivery system of the chamber. In this way, the annulus airflow serves to cool the combustion container and re-direct heat and energy back to the combustion process. This preferred embodiment of the combustor with a “Casing and Annulus for Air Flow Cooling and Energy Recapture” is also illustrated in the combustors of FIGS. 1 and 13-16, but may also be incorporated and adapted with the combustors described in respect to FIGS. 7 and 12.

To elaborate, FIG. 17B provides a simplified illustration of a combustor having, among other elements, a casing (C), an air flow annulus (A), and a combustion container (L) defining a combustion chamber (Ch). As the air flow is directed toward the proximate end and in the vicinity of the fuel-air delivery system (FA), it cools the sidewalls of the container (L) through convective (and conductive) heat transfer, which, in turn, facilitates heat transfer between hot gases inside the combustor chamber (Ch) and the sidewalls. As a further result, the air flow through the annulus is heated. The air flow and the heat loss (from the combustor) captured by it is directed back to the proximate end, and serves the fuel-air delivery system (FA) with a hotter air supply. In this way and in accordance with one aspect of the invention, a significant amount of the heat loss through the sidewalls is re-circulated into the combustion chamber (Ch).

In the drawings and specification, there have been disclosed a typical preferred embodiments of the present invention, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The present invention has been described in considerable detail with specific reference to the illustrated embodiments. It will become apparent, however, that various modifications and changes can be made within the spirit and scope of the invention as described in the foregoing applications. For example, various components and systems described herein may be utilized in different combustion applications or in different combinations and configurations.

Claims

1. A combustion apparatus comprising:

a generally elongated combustion container having a longitudinal axis, a proximal end, an exhaust end spaced axially forward from the proximal end, proximate end wall, an exhaust end wall, and an all-around sidewall extending between the end walls and about the longitudinal axis, the end walls and sidewall substantially defining a combustion chamber; a combustion chamber exhaust positioned on the exhaust end; a delivery system positioned to direct fuel into the combustion chamber for combustion; and an air inlet located generally tangentially on the sidewall to direct air flow generally tangentially into the chamber and induce swirl about the longitudinal axis.

2. The combustion apparatus of claim 1, wherein the air inlet is positioned forwardly of a longitudinal axis midpoint of the chamber such that the tangentially directed air flow into the chamber commences a swirl flow axially proximate the exhaust and such that the swirl flow advances axially therefrom toward the proximal end.

3. The combustion apparatus of claim 1, wherein the exhaust includes an exhaust opening located on the exhaust end wall, the air inlet is located on the sidewall axially proximate the exhaust opening, and the delivery system is located on the proximal end wall to initiate combustion in the proximate end of the combustion chamber.

4. The combustion apparatus of claim 3, wherein the combustion container is cylindrical and is configured such that a distance of a clear direct path between the air inlet and the exhaust opening is less than a diameter of the combustion container.

5. The combustion apparatus of claim 1, wherein the air inlet includes a plurality of tangentially directed radial guide vanes arranged circumferentially about the sidewall.

6. The combustion apparatus of claim 1, further comprising an air supply; and

an outer casing spaced circumferentially outward of and about the combustion container to define an annulus between the combustion container and the outer casing, the outer casing further including an outer air inlet fluidly communicating the air supply with both the annulus and the air inlet of the combustion container.

7. The combustion apparatus of claim 1, wherein the delivery system includes an air swirler positioned to express an annular air swirl into the combustion chamber at the proximate end and includes a radial inlet, a swirl chamber having an outlet with a swirl axis that is substantially parallel or coincident with the longitudinal axis of the combustion chamber, and a swirl nozzle outlet extending axially forward about the swirl axis into the combustion chamber, the swirl nozzle outlet defining a fuel and air delivery zone radially internal thereof.

8. The combustion apparatus of claim 7, wherein the air swirler nozzle includes a base portion including a swirl chamber for receiving air flow and an axially diverging outlet extending forwardly of the base for expressing an annular swirling air outflow.

9. The combustion apparatus of claim 7, wherein the fuel-air delivery system is a fuel-air delivery system that includes a fuel nozzle directed axially into the air nozzle, the fuel nozzle including an outlet tip positioned for directing fuel into a region defined internally by the nozzle outlet.

10. The combustion apparatus of claim 9, wherein the air swirler has a longitudinal swirl axis and an axial opening about the swirl axis, the swirl axis being aligned with an axis of the nozzle outlet, and wherein the fuel nozzle is directed through the axial opening and the radial inlet is configured to deliver a swirling air flow about the swirl axis, and wherein the axial opening defines an annular gap about the fuel nozzle, the air swirler being configured to receive air flow though the annular gap and to a region of the nozzle outlet about the nozzle tip.

11. The combustion apparatus of claim 1, wherein the combustion chamber includes a diaphragm dividing the combustion chamber into a dilution region and a local combustion zone proximate the proximate end wall, the diaphragm including a partial barrier wall extending into the chamber generally transversely to the longitudinal axis.

12. The combustion apparatus of claim 1, wherein the delivery system includes an air swirler and fuel nozzle, the apparatus further comprising a supply air inlet in direct fluid communication with the delivery system, the combustion container being further configured to separate air inlet flow into the combustion chamber from supply air flow to the delivery system.

13. The combustion apparatus of claim 12, further comprising an air chamber adjacent and in fluid communication with the supply air inlet and the fuel-air delivery system, the air chamber being separate from the combustion chamber and the air inlet thereto.

14. A method of combustion comprising the steps of:

providing an elongated combustion container having a longitudinal axis, a pair of axially spaced apart end walls generally defining a proximate end and a distal end, a sidewall extending between the end walls, and an exhaust opening in the distal end;

delivering fuel into the chamber at the proximal end;

introducing tangential air flow into the combustion chamber to induce swirl flow about the longitudinal axis, whereby the swirl flow further induces meridional circulation in the combustion chamber;

including circulatory regions and flow through regions exiting the exhaust opening; and

initiating combustion in the combustion chamber including exhausting hot gases through the exhaust opening.

15. The method of claim 14, wherein during the step of introducing tangential air flow, the swirl flow further induces meridional circulation including circulatory regions and flow through regions exiting the exhaust opening.

16. The combustion method of claim 14, further comprising the steps of:

positioning an air swirler in the proximate end whereby a swirl axis is parallel or

coincidental with the longitudinal axis of the combustion chamber and a swirler outlet includes a sidewall that extends axially forward into the chamber and defines an outlet zone radially internal thereof;

generating a local circulation region in the proximate end, including generating a swirling flow about the swirler axis such that suction is generated at the swirl axis and the swirling air flow is expressed outwardly and annularly along the sidewall and directing fuel spray into the outlet zone, whereby the fuel spray is separate from the annular air swirl and whereby a counterflow of hot gases from the combustion chamber is drawn into the outlet zone by the swirl suction to substantially vaporize fuel therein.

17. The combustion method of claim 16, wherein the step of introducing tangential air flow further induces circulated meridional motion of combustion fluids said method further comprising delivering a liquid fuel spray at the proximate end and an annular swirling air flow about the fuel spray, whereby the swirling flow diverges axially outward away from the fuel spray and a suction is generated to induce a generally axial counterflow radially inward of the annular swirling flow, and whereby the counterflow includes hot gases from the combustion chamber that substantially vaporizes fuel droplets from the liquid fuel spray.

18. The combustion method of claim 17, wherein the annular swirling air flow and the generally axial counterflow generates a local circulation region in the proximate end.

19. The combustion method of claim 18, wherein the meridional circulation includes both global circulation regions and flow through regions in the combustion chamber, wherein the flow through regions are concentrated along the sidewall and about the longitudinal axis to exit through an exhaust opening on the distal end wall and the circulation regions are surrounded by the flow through regions and interact therewith.

20. The combustion method of claim 19, wherein the step of introducing tangential air flow includes introducing the tangential air flow proximate the exhaust opening, whereby swirl flow and flow through regions commence in the distal end.

21. A fuel and air delivery system comprising:

a radial air swirler having a swirl chamber positioned about a swirl axis, a radial inlet for introducing rotational air flow into the swirl chamber, and a central opening positioned to receive swirling flow from the chamber; and

a fuel nozzle directed axially through the central opening of the swirler; and

wherein the air swirler further includes a nozzle outlet in fluid communication with the central opening and having an all around forwardly diverging sidewall for directing a diverging annular swirl flow outward.

22. The system of claim 21, wherein the sidewall defines an outlet zone internal thereof, the fuel nozzle being positioned to direct a fuel spray into the outlet zone.

23. The system of claim 21, wherein the fuel nozzle and the sidewall are configured such that the fuel nozzle directs a spray angle relative to the swirl axis that is less than a sidewall angle relative to the swirl axis, such that the fuel spray is spaced inwardly of the annular swirl flow along the sidewall.

24. The system of claim 21, wherein the central opening defines an annular gap between the fuel nozzle and the swirl chamber, the annular gap being configured to pass an axial air flow into the outlet zone, and

wherein the air swirler includes a throat defined by a reduced diameter area of the sidewall, the air swirler being operable to generate a low pressure area about the throat such that a counterflow is drawn toward the throat.