Abstract: A low NO.sub.x burner combustion system which may be adjusted for optimum burn rates, temperature and oxygen levels. The burner incorporates a plurality of gas nozzles which individually inspirate a portion of the combustion air and a spin vane diffuser to rotate and mix the gases within the primary combustion zone. The diffuser is axially adjustable in order to vary the distance between the vane and the first combustion zone while the blades of the diffuser can be angularly adjusted to optimize the rotation and mix of the gases. Air for combustion is supplied through primary, secondary and tertiary passages to create distinct combustion zones for complete combustion. The flow rate of the combustion air is controlled through a damper in accordance with the burn characteristics. The angular and axial position of the diffuser and the damper control of combustion air can be automatically adjusted throughout the firing range of the burner in response to demand levels.

Abstract: Method and apparatus for generating an oxy-fuel flame with lowered NOX products by confining the oxy-fuel flame produced in a concentric orifice burner along a path defined by the rate of flame propagation and the diameter of the burner.

Abstract: Disclosed is a structure of a burner which can be fueled with gas fuel or oil fuel. The main features includes: a specially designed swirl generator; an annular hollow gas gun; an oil gun received in the gas gun where the gas jets of the gas gun and the oil jets of the oil gun have an predetermined angle with respect to the centerline. Under designed operating conditions, a swirling air flow can be generated with a low pressure drop and low turbulences, which is beneficial to flame stability, reducing flame temperature, and delaying the mixing of air and fuel, thus inhibiting the formation of NO.sub.x. Staging air and flue gas recirculation are available for further reduction of nitrogen oxides.

Abstract: An air-cooled oxygen-gas burner for use with a direct fired furnace. The burner comprises a body formed from three concentric metal tubes supported in a cylindrical housing secured about a conical bore in a refractory side wall of a furnace. The three concentric tubes have a cone shaped inner end which are adjustable to define a nozzle with annular openings therebetween of variable size to vary the shape of a flame produced by a mixture of combustible gas, oxygen and air fed under pressure, respectively, in each of two chambers defined between the three concentric metal tubes and a chamber defined between the tubes and the cylinder housing. The combustible gas is fed in the inner chamber, the oxygen in the intermediate chamber, while the air is fed in the outer chamber to cool the concentric tube assembly and the furnace refractory about the burner nozzle.

Abstract: High velocity gas injection system wherein high velocity and low velocity gases are injected into a cavity in a defined relationship such that the low velocity gas forms a protective barrier from combustion zone damage due to the flow dynamics caused by the high velocity gas.

Abstract: A burner (1) for feeding solid and liquid or gaseous fuel into a burning zone (8) of a kiln, for instance a rotary kiln, and comprising central duct (2) for liquid or gaseous fuel, a surrounding annular duct (3) for primary air and a further surrounding annular duct (4) for solid fuel is provided with an outer duct system (5) for feeding yet an amount of primary air into the burning zone (8), the duct system (5) being in the form of a heat exchanger for transferring heat from the inner kiln compartment surrounding the burner (1) to the primary air transported in the duct system (5) and thereby increasing the velocity of the air passing through the system without any corresponding increase of the fan power or the energy consumption of the kiln plant, but with a substantial decrease in the amount of primary air fed to the burning zone. The duct system (5) is separated from the remainder parts of the burner (1) by an insulating layer (7).

Abstract: The invention is a process for combusting a gaseous fuel in a burner to result in low NO.sub.x emissions by first feeding a gaseous fuel stream and an air stream to a premixer where the fuel and air streams are mixed to form a fuel-air mixture. The fuel and air streams are fed to the premixer at a fuel to air equivalence ratio of less than 1 (i.e., fuel-lean). Second, the fuel-air mixture is passed to a combustion chamber where the fuel is substantially combusted to produce a combustion chamber jet and flue gases. The combustion chamber jet and flue gases pass into a heating zone which may include a furnace, heater, or boiler. Third, at least two high-velocity fuel streams, optionally diluted with a nonreactive thermal ballast, are passed to the heating zone contemporaneously with the second step. The high-velocity fuel streams entrain at least a portion of the flue gases. The fuel in the high-velocity fuel streams is partially combusted prior to coming into contact with the combustion chamber jet.

Abstract: A burner for the combustion of a fuel plus air mixture comprises a central nozzle pipe having an inner surface with a portion which diverges outwardly. An axially moveable plug is positioned within the nozzle pipe and includes an outer wall with a diverging section extending within the diverging section of the nozzle pipe. By axially moving the plug, the cross sectional area of the space between the diverging surfaces increases and decreases for respectively decreasing and increasing the velocity of the fuel plus air mixture passing through the nozzle space. This reduces the formation of NO.sub.x and the length of the flame produced by the burner.

Abstract: An oxy-fuel system for reducing NO.sub.x formation in corrosive high temperature environments including a self-cooled adjustable oxy-fuel burner that generally produces a luminous flame having a concentric fuel rich phase and an outer surrounding oxidizer rich phase the flame directed through a precombustor mounted on the flame end of the burner the precombustor having a length to diameter (L/d) ratio fixed by the firing rate of the burner.

Abstract: The present invention provides a burner for burning a fuel in an oxidant. In accordance with the apparatus, a fuel nozzle is provided for producing a fuel jet of the fuel adapted to burn within the oxidant with the flame extending outwardly from the fuel nozzle and such that the particles of fuel become increasingly more buoyant along the length of the flame. A lower oxidant nozzle is located below the fuel nozzle for creating a lower oxidant jet of the oxidant that produces a low-pressure field below the fuel jet for downwardly spreading the fuel into the oxidant. Additionally, an upper oxidant nozzle is located above the fuel and lower oxidant nozzles for creating an upper oxidant jet of the oxidant to burn the increasingly more buoyant particles of the fuel. The velocities of the upper and lower oxidant jets can be adjusted independently of their mass flow rates to adjust the flame shape from sharp (convection dominated) to lazy (radiation dominated) without changing the stoichiometry of the flame.

Abstract: A combustion method employing fuel-rich combustion with an upstream recirculation zone followed by a downstream plug flow zone enabling rapid heating and processing without excessive NO.sub.x generation or particulate emissions.

Abstract: A regenerative burner having heat storage units with combustion effluent/combustion air ducts therethrough, fuel intake means and a burner body, wherein the burner is designed to suppress NOx formation and to control flame shape and characteristic in the regenerative system during combustion. The regenerative burner may include a burner baffle, or may include a plurality of gas jets entrained in generally converging fashion for control of the flame characteristics and shape dispositive of NOx formation. The burner may provide for staged combustion, either by means of sequential fuel injection or sequential provision of combustion air, or the burner may depress NOx formation by vitiation of combustion air with products of combustion. The present regenerative burners suppress NOx formation yet preserve the remaining characteristic features of regenerative systems.

Abstract: This invention relates to a process for exploitation of a burner and to a burner for rotary tubular furnaces, wherein fuels and primary combustion air are supplied concentrically and the burner comprises a burner nozzle which comprises concentric supply conduits for the fuel and for the primary combustion air in the form of axial air and eddying air. In order to procure a process and burner which may operate with a smaller proportion of primary air and a greater range of adjustment, a dead zone is provided at the center of the flame directly all around a central fuel conduit and within an annular fuel supply conduit, in which a very small proportion of fuel is sent.

Abstract: A power fuel oil burner is provided that includes an electrical motor having a double ended shaft. A squirrel-cage blower overlies the motor. A scroll housing includes a scroll wall that overlies and radially surrounds the blades of the blower. A motor mount integral with the scroll housing supports the motor. The scroll housing is an integral die-cast casting. A fuel pump is driven by a second end of the shaft externally of the scroll housing. A mounting member includes an open cylindrical portion and a radial flange portion. The cylindrical portion is received within the air outlet of the scroll housing, and a cylindrical burner tube is received within the cylindrical portion of the mounting member for communication with the air blower. An integral sheet metal stamped flamelock is disposed within the burner tube downstream of the burner means, is cup-shaped and has an annular frusto-conical portion and an annular ring portion extending radially inward from the frusto-conical portion.

Abstract: A parallel flow liquid fuel burner is disclosed which has a device for injecting fuel in a central flame stabilizer; the stabilizer comprises a blade-containing rose situated around a central hub itself situated around the injection device and the injection device comprises several fuel injection orifices adapted to provide separate elementary flames.

Abstract: Improved methods and burner apparatus are provided for discharging mixtures f fuel and air into furnace spaces wherein said mixtures are burned and flue gases having low NO.sub.x content are formed therefrom. The methods basically comprise discharging a first fuel mixture containing a portion of the fuel and flue gases from the furnace space into the furnace space whereby the mixture is burned in a primary reaction zone therein and flue gases having low NO.sub.x content are formed therefrom, and then discharging the remaining portion of the fuel into a secondary reaction zone wherein the remaining portion of fuel mixes with air and flue gases to form a second fuel mixture which is burned in the secondary reaction zone and additional flue gases having low NO.sub.x contents are formed therefrom.

Abstract: A burner for a hearth including a gun for introducing a primary comburant and a gun for supplying a secondary comburant, with a device for supplying a gaseous fuel and a deflector stabilizer arranged substantially at an extremity of the gun introducing the primary comburant. The fuel supply device includes a first fuel injector arrangement adapted to produce a first jet of fuel substantially axially or slightly divergent with respect to a longitudinal center axis of the burner, and a second fuel injector arrangement adapted to produce a second jet of fuel divergent with respect to the longitudinal center axis of the burner.

Abstract: An improved process and apparatus for reducing NO.sub.x content of flue gas effluent from a furnace, the improvement comprising a burner assembly having a burner and flue gas recirculating system for collecting and passing internally recirculating flue gas into a combustion zone for reaction with a combustion flame. The burner preferably has a plurality of fuel dispensing nozzles peripherally disposed about the combustion zone to aspirate collected internally recirculating flue gas into the combustion zone, and has a plurality of fluid driven eductors to drive further amounts of collected internally recirculating flue gas into the combustion zone.

Abstract: The formation of nitrogen oxides during the operation of burners for solid, liquid, and gaseous fuels is reduced by means of an exhaust gas feed-back system. The exhaust gases are injected into a combustion chamber through openings provided in the region of stabilizer via a flame pipe and, by choice, also around the flame pipe. Preferably, the combustion air as well as the exhaust gases are activated by an active aerosol. The exhaust gas feed-back is effected by means of a longitudinally slidable adaptor pipe and an adaptor pipe shoulder enclosing the flame pipe at least partly. The regulation of the exhaust gas streams is achieved by displacing the adaptor pipe and the adaptor pipe shoulder.

Abstract: In a combustion installation, a mixture of fresh air (D) and exhaust gas (C) is fed to the burner (A) via a mixing/conveying device (EFG). There is provided in the combustion installation a heat exchanger (M), which undertakes the thermal conditioning of the mixture (H) before the latter is fed into the burner (A).

Abstract: Combustion method and apparatus establishing coherent jet oxidant flow within a cavity recessed from the main combustion area enabling operation without need for water cooling.

Abstract: Improved methods and burner apparatus are provided for discharging mixtures of fuel and air into furnace spaces wherein said mixtures are burned and flue gases having low NO.sub.x content are formed therefrom. The methods basically comprise discharging a first fuel mixture containing a portion of the fuel and flue gases from the furnace space into the furnace space whereby the mixture is burned in a primary reaction zone therein and flue gases having low NO.sub.x content are formed therefrom, and then discharging the remaining portion of the fuel into a secondary reaction zone wherein the remaining portion of fuel mixes with air and flue gases to form a second fuel mixture which is burned in the secondary reaction zone and additional flue gases having low NO.sub.x content are formed therefrom.

Abstract: A burner apparatus which comprises a pilot burner including a nozzle and swirlers disposed around the nozzle, and a plurality of main burners which are arranged around the pilot burner and each of which comprises a nozzle and swirlers disposed around the nozzle; and the angle of the swirlers for the pilot burner is set larger than the angle of the swirlers for the main burner so that the angles of the two types of swirlers cross. NOx production can be considerably reduced with a very simple structure based on the present invention for combustion in boilers and gas turbines.

Abstract: An oxygen-fuel burner is disclosed wherein the atomizing fluid not only atomizes a liquid fuel, but also functions to cool the burner tip and prevent eddying of the atomized fuel from collecting on the burner tip, which could create undesirable high temperatures upon ignition. Further, oxygen may be utilized as an atomizing fluid in view of the fact that the atomization of the fuel is accomplished so close to the discharge end of the burner and the discharge velocity is maintained at such a high level, that the contact time of the oxy-fuel within the burner is extremely short, thereby precluding preignition within the burner. Further, the oxygen itself also functions to cool the burner tip and prevent preignition or cracking of the liquid fuel in the atomizing chamber. The burner may be utilized with carbon dioxide as an atomizing fluid wherein the burner temperature is thus lowered reducing the amount of NO.sub.

Abstract: A high-speed type burner tile assembly including a cylindrical mixing tile having a central through-hole, and a combustion tile having a tip portion aligned with the mixing tile. The tip portion of the combustion tile is coaxially extended into the central cylindrical through-hole of the mixing tile to provide diffusion air delivery passages extending in parallel with the axis of the mixing tile between the tip portion and the inner surface of the through-hole of the mixing tile, thereby permitting the supply of a large volume of diffusion air at low pressures and increasing linearity of the combustion gas supplied into a furnace.

Abstract: There is disclosed a blower-type burner for use with heating boilers which is effective for reducing NO.sub.x pollutants produced by flue gases. The device is mountable about an opening in a closure or sealing panel of a furnace body and provides for containment of the flue gas path within the burner. A separated dual impeller system provides for complete separation of the flue gas path from a combustion intake system.

Abstract: A burner for mixing and burning a gaseous fuel includes an inner pipe, carrying the gaseous fuel, and an outer pipe, carrying combustion air in the annular space between the inner and outer pipes. A cone-shaped horn is affixed to the end of the inner pipe. The horn extends near the inner surface of the outer pipe, leaving a narrow annular space therebetween. An alternating series of air jetting portions and blind portions around the periphery of the large end of the horn encourage the formation of mixing vortices as air passes through the air jetting portions. A plurality of radially directed fuel jetting openings in the inner pipe, upstream of the horn, inject gaseous fuel into the combustion air to form a lean air-fuel mixture. A plurality of jet openings at the end of the inner pipe, within the horn, direct gaseous fuel generally parallel to the diverging wall of the horn.

Abstract: A burner nozzle for burning petroleum products. The burner nozzle includes a fluid conduit with an air jacket disposed therearound such that a dead air space is defined therebetween to prevent fluid leakage from entering the air jacket. The burner nozzle comprises a replaceable air jetting assembly which provides an annular stream of air, either cylindrical or conical in configuration, which impinges the fluid stream exiting the nozzle for atomization thereof. The jetting assembly includes a replaceable and interchangeable jetting insert. A swirl chamber is provided in the fluid conduit to impart a swirling motion to fluid flowing therethrough. The swirl chamber is clamped in position on opposite sides thereof so that it is always in compression, thus allowing use of non-weldable materials. One embodiment has a variable air jetting orifice.

Abstract: A cyclone combustion apparatus includes a combustion chamber having a substantially cylindrical wall, a substantially cylindrical exit throat at the rear end of the combustion chamber, means for supplying fuel into the combustion chamber at a front end thereof, means for supplying air into the combustion chamber and for forming a cyclonic flow pattern of hot gases for combustion within the chamber, and heat exchange means surrounding and extending throughout the axial length of the combustion chamber. The means for supplying air includes a plenum chamber having an air inlet and an annular air supply opening in communication with and coaxial with the combustion chamber. The annular air supply opening has spaced radial vanes tilted at a selected angle from the axis of the combustion chamber. The means for supplying fuel includes a fuel plenum chamber having a fuel inlet and a plurality of radially spaced fuel holes for supplying fuel in the annular air supply opening between the spaced radial vanes.

Abstract: An atomizing burner with a nozzle tube having a mouth opening edge, for feeding liquid fuel to a firing chamber, is to be improved in that, for the purposes of combustion of heavy oil the nozzle tube 33 is surrounded by a jacket tube (14) which projects beyond the mouth opening edge (34) of the nozzle tube and with same forms an annular space (50) for secondary air (z) which can be supplied to the heavy oil downstream of a primary air flow (y) in the flow direction. In addition the jacket tube (14) is to be provided with lateral openings (51) for the secondary air (Z) to be introduced into the annular space (50).

Abstract: The smokeless ignitor of the present invention prevents visible emissions upon cold or hot start-up of coal-fired or oil-fired utility boilers. The smokeless ignitor satisfies flame stability and combustion requirements by establishing a flame with 15-30% mass recirculation rate, a recirculation zone length of 0.75-1.5 effective throat diameters, a spray SMD of less than 120 microns and a STU value of .+-.50% or less.

Abstract: A regenerative burner having heat storage units with combustion effluent/combustion air ducts therethrough, fuel intake means and a burner body, wherein the burner is designed to suppress NOx formation and to control flame shape and characteristic in the regenerative system during combustion. The regenerative burner may include a burner baffle, or may include a plurality of gas jets entrained in generally converging fashion for control of the flame characteristics and shape dispositive of NOx formation. The burner may provide for staged combustion, either by means of sequential fuel injection or sequential provision of combustion air, or the burner may depress NOx formation by vitiation of combustion air with products of combustion. The present regenerative burners suppress NOx formation yet preserve the remaining characteristic features of regenerative systems.

Abstract: A nozzle mix, open power burner includes an air housing for receiving pressurized air from a blower. A flame retention plate including a plurality of openings therein is adapted for placement at the outlet of the air housing, so that air supplied to the housing is outletted therefrom through the flame retention plate openings. A gas tube extends through the air housing and includes a gas discharge outlet downstream of the flame retention plate. Gas is discharged from the gas outlet in a direction radially outwardly relative to the longitudinal axis of the gas tube, so that gas is discharged into the flow path of air passing through the flame retention plate. A hot surface igniter is provided downstream of the flame retention plate for igniting the mixed gas and air.

Abstract: A burner apparatus having particular advantage for use with rotary kilns of the type used to process cement, lime, and the like, provides adjustable flame geometry and location within the combustion zone. Either gaseous or liquid fuels can be fired with highly selective heat flux as required for processing. Air and gaseous fuel injection means are controllable to vary the velocity of injection and thereby alter flame geometry. This is achieved by disposing an axially-adjustable control baffle in a crossectional area of changing transition section formed by coaxial members, between which an air supply conduit is formed. The control baffle is cylindrical and fits in and moves within the air supply conduit. The transition section has frustoconical surfaces opposite frustoconical surfaces on the control baffle so that different gaseous mass flow can be regulated around a central flame resulting in an adjustable flame geometry.

Abstract: Method and apparatus to carry out combustion with more uniform temperature distribution and with reduced NO.sub.x generation comprising oxidant injection through a nozzle having straight and angled orifices with aspiration into the angled oxidant and downstream consolidation of the oxidant streams.

Abstract: A burner assembly (75) for the combustion of liquid fuels in furnaces (12) and the like. The assembly comprises fuel gun means (78) for creating a mixture of combustible fuel and an atomizing medium and injecting a stream of the mixture into the interior of a furnace; housing means (76) supporting the fuel gun means, attachable to the furnace, so that the combustible fuel mixture is delivered to the interior of the furnace for combustion and for supplying a first flow of air (B) into the furnace separate from the air mixed with the fuel to encompass the injected fuel mixture; and sirler means (79) having a plurality of blades (94) interposed within the housing means so that the first flow moves around and through the blades for imparting a rotation to the first flow of air to break up the stream of fuel mixture.

Abstract: A method for combusting fuel containing bound nitrogen to achieve reduced NO.sub.x emissions wherein the oxidant and fuel are injected separately into a combustion zone through a burner and the oxidant is injected with a momentum equal to at least three times the fuel stream momentum and at an angle equal to or greater than the sum of the angles of the fuel stream periphery and oxidant stream periphery with their respective centerlines.

Abstract: This invention concerns the burning of fuels, such as natural gas, at high temperatures. The invention includes a high-efficiency burner which achieves substantially complete combusiton at modest cost. The burner of the present invention includes a generally cylindrical housing having a central bore and two concentric annular regions. A lance is inserted through the central bore, and protrudes slightly from the front face of the burner housing. The fuel is directed through the inner annular region, and oxygen-enriched combustion air is directed through the outer annular region. Substantially pure oxygen is directed through the lance. The gases in the lance and the annular regions do not communicate with each other within the burner housing, and all burnign takes place outside the housing. The same supply of oxygen can be used to supply the lance and to enrich the combustion air.

Abstract: The invention relates to a process and an apparatus intended to effect the combustion of a mixture of air and liquid or gaseous fuel, wherein the injection of the fuel is staged without that of the air for combustion being staged. According to the invention, in addition to the primary means (20, 34) for injecting fuel into the passage (10, 14) supplying air to the burner, secondary injection means (24) mounted inside said passage are provided and comprise a main part (24a) which is extended by a terminal part (24b) bent in such a manner that the end of said terminal part is situated downstream of the end of the primary means (20, 34) and at a distance from the axis (2) of said passage which is greater than the minimum section of the latter. The invention is applicable both to so-called parallel air admission burners and to burners having swirl vanes.

Abstract: An improved burner having a very particularly designed gas element for the combustion of coal, oil or gas places a plurality of retractable and rotatable gas elements in close proximity to the outlet end of a tubular burner nozzle of the burner which are shielded from combustion air provided around the tubular burner nozzle by a flame stabilizing ring having a plurality of openings adapted to closely receive each of the plurality of retractable and rotatable gas elements. Eddies produced by the flame stabilizing ring create a low oxygen/fuel rich flame resulting in reduced NO.sub.x formation.

Abstract: A burner and combustion method employing oxygen or oxygen-enriched air as the oxidant comprising a low velocity oxidant stream in proximity to high velocity main oxidant within a combustion zone enabling efficient combustion with a stable flame at very high oxidant velocities.

Abstract: Described is a gas burner, that works with an excess of combustion air.According to the invention the gas burner is provided with a by-pass conduit for a portion of the combustion air and with a built-in gas control valve and a built-in air control valve, which valves are coupled to be moveable in synchronism, and the air control valve is provided with means for adjustably dividing the combustion air.

Abstract: The wall (5) of a tube (2) for delivering pulverized fuel to the outlet (4) of an oxy-fuel burner (1) forms part of a chamber (6) which is pressurized or evacuated. The pressure in the chamber is continuously monitored. If the pressure in the chamber (6) changes in a way indicative that the wall (5) of the oxy-fuel burner (1) has failed the oxy-fuel burner (1) is automatically shut down.

Abstract: Disclosed is a burner for the partial combustion of a solid carbonaceous fuel wherein coal, e.g., finely divided coal, is supplied to a reactor space via a central channel disposed along the longitudinal axis of the burner, and oxygen-containing gas is supplied via an annular channel surrounding said central channel, and heat from the combustion is removed from the hollow front face of the burner by coolant flowed through said front face spirally about the longitudinal axis of the burner.

Abstract: The nozzle comprises an axial chamber (23) provided in a first part (21) and into which the fuel gas is fed, and a chamber (24) which surrounds the chamber (23) and into which air is fed; the two chambers (23) and (24) are separated from the combustion chamber (4) by a front plate (5) in which three series of apertures are provided, namely a series of peripheral apertures (31) arranged to pass secondary air with a velocity having an axial and tangential component, a second series of apertures (32) disposed on a more inner circumference and arranged to pass primary air and also having an axial and possibly also tangential component, and a third series of more central apertures arranged to pass gas; by virtue of said apertures the burner thermal output is adjustable to the extent of enabling it to be varied within a very wide range of values.

Abstract: A burner and combustion method employing oxygen or oxygen-enriched air as the oxidant comprising a low velocity fuel stream in proximity to high velocity main fuel within a combustion zone enabling efficient combustion with a stable flame at very high fuel velocities.

Abstract: A protruding mantle separates burner internals from the hot gasification environment. The mantle is cooled by at least one of the feedstreams. The lining can be made of ceramics such as silicon carbide and/or silicon nitride. In order to lower thermo-mechanical stress the lining is thin-walled.

Abstract: A process to combust fuel and oxidant at high efficiency and with low NO.sub.x generation even when the fuel has non-uniform characteristics and the oxidant is pure oxygen, wherein fuel and oxidant are first combusted within a high velocity oxidant-rich jet, fuel is mixed with combustion products in a recirculation zone and the mixture is aspirated into the oxidant-rich jet and combusted in a diffuse secondary flame at the periphery of the oxidant-rich jet.

Abstract: The invention relates to a method and a burner in which a proportion of the fuel is delivered via an outer annular duct and accelerated at the outlet end to a high speed, while a further proportion of the fuel is delivered via a second, inner annular duct and retarded at the outlet end to a slow speed. This results in stabilization and regulation of the principal flame by a permanent pilot flame.

Abstract: The emission of NOx, soot and particulates is minimized by combusting fuel in two sequential steps, viz. a first combustion step wherein a number of fuel jets and a substoichiometric amount of combustion air in the form of an equal number of high-velocity air jets are injected into a combustion chamber in such a manner that(a) each fuel jet merges into one high velocity air jet,(b) the characteristic mixing time of each fuel jet is less than about 10.sup.-4 sec, and(c) a plurality of separate fuel/air jets is generated forming at ignition a plurality of primary flames in which a residence time for the fuel of substantially at least 100 ms is maintained;and a second combustion step comprising introducing further combustion air into said combustion chamber for complete combustion of the fuel.