GAS TURBINE ENGINES AND METHODS FOR COOLING COMPONENTS THEREOF WITH MID-IMPELLER BLEED COOLING AIR
Gas turbine engines and methods for cooling components thereof with mid-impeller bleed (MIB) cooling air having a pressure are provided. The gas turbine engine has a compressor comprising an impeller body and an impeller shroud at least partially surrounding the impeller body. The impeller shroud has a plurality of MIB openings disposed therein. At least one edge treatment is provided thereto. The edge treatment substantially preserves pressure of the cooling air during entrance into and discharge out of the MIB opening. The plurality of MIB openings may be extended MIB openings in a thickened impeller shroud. The centerline of the MIB openings may be oriented to be substantially aligned with an averaged local absolute flow velocity vector of the cooling air at the inlet section of the MIB opening in order to extract cooling air in a direction that has a vector component in a tangential, an axial, and a radial flow direction.
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The present invention generally relates to gas turbine engines, and more particularly relates to gas turbine engines and methods for cooling components thereof with mid-impeller bleed cooling air.
BACKGROUNDA gas turbine engine typically includes a compressor, a combustor, and a turbine. Airflow entering the compressor is compressed and directed to the combustor where it is mixed with fuel and ignited, producing hot combustion gases used to drive the turbine. Due to the high temperature of the combustion gases, the turbine must be cooled in order to maintain acceptable material temperatures for the turbine components. Typically, these turbine components are air cooled and cooling air is often channeled through a turbine cooling circuit to the turbine for use as a cooling source.
Extracting cooling air from the compressor may affect overall gas turbine engine performance. To minimize a reduction in engine performance, cooling air is typically extracted from the lowest compressor stage that has a sufficient pressure for the turbine. Generally, because the temperature of air flowing through the compressor increases at each stage of the compressor, utilizing cooling air extracted from the lowest feasible compressor stage results in a lower engine performance penalty. Furthermore, the turbine is cooled more effectively when the cooling air is extracted from a source having a lower temperature. In gas turbine engines including centrifugal compressors/impellers, cooling air is typically extracted at an inlet and/or exit of the centrifugal compressor/impeller. On one hand, cooling air extraction from the inlet of the centrifugal compressor may not have sufficient pressure for the turbine application for which it is intended. On the other hand, cooling air from the exit thereof is often at a higher pressure level than needed for turbine cooling. An associated engine performance loss results from utilizing cooling air at such an excessive pressure level. This is because additional work was done to compress such air making it thermodynamically expensive and furthermore cooling performance is adversely impacted because such air is at a higher temperature level. As a result, overall engine performance is affected and the turbine is ineffectively cooled.
It has been recognized that cooling air extraction from the middle of the centrifugal compressor/impeller (i.e., mid-impeller bleed (“MIB”)) is thermodynamically less expensive than cooling air extracted from the exit of the centrifugal compressor, with cooler air, and better engine performance, but the pressure of the cooling air extracted mid-impeller is lower than at the exit. Pressure preservation is therefore an important aspect of a mid-impeller bleed system. In a conventional mid-impeller bleed (MIB) system, the cooling air is extracted from the engine flow path through substantially cylindrical bleed openings or slots (hereinafter a “conventional MIB opening”) in a stationary impeller shroud of the centrifugal compressor. Conventional MIB openings are typically located between the inlet and exit of the impeller/centrifugal compressor at a constant radial distance from the engine centerline. Entrance and exit of cooling air into and out of conventional MIB openings result in pressure losses. Conventional bleed openings may have sharp edges at constant area inlet and outlet sections with a relatively short conical diffuser section between the inlet and outlet sections, contributing to such pressure losses. In addition, conventional MIB openings are oriented in the same plane normal to the direction of airflow permitting extraction of the larger tangential flow component only, while ignoring the smaller radial and axial flow components of the local velocity.
Accordingly, it is desirable to provide gas turbine engines and methods for cooling components thereof with mid-impeller bleed (MIB) cooling air. In addition, it is desirable to extract less thermodynamically expensive MIB cooling air while maximizing pressure, thereby preserving or recovering as much pressure as possible for subsequent applications. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this
BACKGROUND OF THE INVENTION BRIEF SUMMARYMethods are provided for cooling components of a gas turbine engine with mid-impeller bleed (MIB) cooling air having a pressure, according to exemplary embodiments of the present invention. The gas turbine engine has a compressor comprising an impeller body and an impeller shroud at least partially surrounding the impeller body. The impeller shroud has a plurality of MIB openings disposed therein. At least one edge treatment is provided to at least one MIB opening of the plurality of MIB openings in the impeller shroud. The at least one edge treatment substantially preserves the pressure of the MIB cooling air during entrance into, discharge out of, or both entrance into and discharge out of the at least one MIB opening.
A gas turbine engine is provided for cooling components thereof with cooling air in accordance with yet another exemplary embodiment of the present invention. The gas turbine engine includes a compressor that compresses intake air into intermediate pressure cooling air and high pressure air. The intermediate pressure cooling air is formed upstream of the high pressure air. The compressor comprises an impeller, an impeller shroud, and a plurality of MIB openings disposed in the impeller shroud. The plurality of MIB openings have a length co-terminating with a thickness of the impeller shroud, and an inlet section in flow communication with an engine flow path to extract the intermediate pressure cooling air therefrom, an outlet section in flow communication with a turbine, and a conical diffuser section between the inlet and outlet sections. The at least one MIB opening of the plurality of MIB openings has at least one edge treatment.
A compressor for a gas turbine engine is provided for cooling components thereof with cooling air in accordance with yet another exemplary embodiment of the present invention. The compressor comprises an impeller body having an exit and a thickened impeller shroud at least partially surrounding the impeller body. The thickened impeller shroud has a plurality of extended mid-impeller bleed (MIB) openings extending therethrough adapted to extract at least a portion of a tangential flow component, an axial flow component, and a radial flow component of cooling air from an engine flow path. The plurality of extended MIB openings is disposed at a distance from the exit of the impeller body. At least one extended MIB opening of the plurality of extended MIB openings has an inlet section, an outlet section, and an elongated conical diffuser section between the inlet and outlet sections. The inlet section has a leading edge and the outlet section has a trailing edge. The at least one extended MIB opening has a centerline orientation adapted to be substantially aligned with a local absolute flow velocity of the cooling air.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description.
Various exemplary embodiments are directed to gas turbine engines and methods for cooling components thereof with mid-impeller bleed (hereinafter “MIB”) cooling air. Specially designed mid-impeller bleed openings (hereinafter “MIB openings”) disposed in an impeller shroud of a compressor extract cooling airflow from an engine flow path and provide this cooling air to a plenum of the compressor for use in subsequently cooling the engine components. The dynamic pressure of the cooling airflow through the MIB openings is substantially recovered by providing the MIB openings with at least one edge treatment. Unless otherwise specified, the term “MIB openings” as used herein includes both conventional MIB openings and extended MIB openings according to exemplary embodiments, as hereinafter described. The extended MIB openings are disposed in a thickened impeller shroud according to exemplary embodiments, as hereinafter described. Unless otherwise specified, the term “impeller shroud” as used herein includes both a conventional impeller shroud and the thickened impeller shroud. As used herein, the term “dynamic pressure” means pressure associated with the kinetic energy of the airflow. The term “dynamic pressure recovery” or the like refers to a reduction of dynamic pressure with resultant increase in static pressure by reducing the velocity of the airflow in a manner that minimizes pressure losses, i.e., by gradually increasing flow area in the direction of flow. Thus, “dynamic pressure recovery” as used herein means the conversion of dynamic pressure into static pressure. The methods as described herein, according to exemplary embodiments, permit the preservation of dynamic pressure to maximize the amount thereof that can be converted to static pressure by, for example, minimizing pressure loss. The extended MIB openings are more effective at dynamic pressure recovery than conventional MIB openings. The centerline of the MIB openings may additionally or alternatively be oriented to be substantially aligned with an averaged local total flow velocity vector to extract tangential, radial, and axial flow components of the cooling airflow, thus also improving dynamic pressure recovery over conventional MIB openings that substantially ignore the radial and axial flow components.
Referring to
In
The step of forming the impeller shroud further comprises forming a plurality of MIB openings therein. The plurality of MIB openings is disposed in the impeller shroud at a distance from the impeller exit of the impeller body, as hereinafter described. The plurality of MIB openings may be conventional MIB openings 61a disposed in a conventional impeller shroud 58 (shown in dotted lines through the conventional impeller shroud 58 of
Referring again to
Referring now to
Referring now to
Geometry of the MIB openings is defined in terms of the following dimensions (See, e.g.,
L=length of conical diffuser section
d1=inlet section diameter
d2=outlet section diameter
L/d1=length of conical diffuser section/inlet section diameter
Divergence cone angle=2θ
Area ratio=d22/d12
The area ratio=d22/d12 applies to MIB openings having a circular cross-section. While the MIB openings 61a and 61b are described with a circular cross-sectional area perpendicular to the bulk flow direction through the MIB opening and the same is shown through the accompanying figures, it is to be understood that MIB openings having a non-circular cross-section perpendicular to the bulk airflow through the MIB opening (i.e., a “non-circular cross-sectional flow area”) may be used in other embodiments, in which case “diameter” is determined by the hydraulic diameter (Dh) defined by the following equation:
Dh=4*(Flow Area)/(Wetted Perimeter)
wherein:
flow area=cross-sectional area perpendicular to the bulk airflow through the non-circular MIB opening; and
wetted perimeter=perimeter of the Flow Area in contact with the airflow.
The extended MIB openings 61b have a greater L/d1 relative to the L/d1 of conventional MIB openings 61a with a reasonable cone angle because of the greater length (L) of the extended MIB openings 61b. In accordance with exemplary embodiments, the thickened impeller shroud 60 creates room for the extended MIB openings 61b, providing additional area for the extended MIB openings 61b and for at least one edge treatment, as hereinafter described. An area ratio (d22/d12) of about 1 to about 3 is preferred, but higher or lower area ratios may be used. The thickened impeller shroud and the longer length (L) of the elongated conical diffuser section in the extended MIB openings 61b relative to the conical diffuser section in the conventional MIB openings 61a substantially ensures a reasonable cone angle at a given area ratio. In general, the longer the length (L) for a given area ratio, the more efficient the conical diffuser section is in converting inlet dynamic pressure into static pressure at an exit of the MIB opening. It is known that a higher L/d1 provides improved pressure recovery, with less variability in diffuser area ratio and more consistent MIB opening performance The divergence cone angle of the (elongated) conical diffuser section is generally between about 0 degrees and about 15 degrees, although it is to be understood that higher divergence cone angles may be used. For a given L, the higher the divergence cone angle, the higher the area ratio. With the thinner conventional impeller shroud 58, there may not be enough room for an optimal divergence cone angle. However, if the divergence cone angle of the conical diffuser section is too great, flow separation within the MIB opening may occur. The thickened impeller shroud 60 also makes it easier to substantially align a centerline of the extended MIB openings 61b with an averaged local absolute total flow velocity vector of the MIB cooling air at the MIB opening inlet, as hereinafter described. As noted above, the extended MIB openings 61b provide better dynamic pressure recovery than conventional MIB openings 61a.
In accordance with exemplary embodiments, the step of forming the impeller shroud further comprises orienting a centerline 94 of each of the MIB openings of the plurality of MIB openings to be substantially aligned with the averaged local absolute flow velocity of the MIB cooling air at the inlet of the MIB opening. While the orientation of extended MIB openings disposed in the thickened impeller shroud 60 is hereinafter described, conventional MIB openings 61a may have their centerline oriented in impeller shroud 58 in the same manner as noted below in order to extract tangential, axial, and radial flow components of the cooling air, unlike conventional MIB openings that do not have their centerline substantially aligned with the averaged local absolute flow velocity of the MIB cooling air at the inlet of the MIB opening. Without such centerline orientation, only a fraction of the tangential flow component is extracted and the axial and radial velocity components are ignored. Referring now to
Referring specifically to
Once the centerline orientation of the first MIB opening in the impeller shroud has been determined as described above, the other MIB openings in the impeller shroud may be generated by rotating the impeller shroud to define a MIB opening pattern. The other MIB openings have substantially the same orientation relative to datums A and B as the first MIB opening therein. Alternatively, the centerline orientation of each of the MIB openings in the impeller shroud may be determined independently using the two rotation angles as described above.
Substantial alignment of the centerline 94 of the extended MIB opening with the averaged local airflow velocity vector is to maximize the capture of dynamic pressure of the cooling air and convert it into static pressure inside the plenum where the cooling air is collected for delivery to the cooling destinations in the turbine. The plenum 78 is a manifold of the compressor where cooling air from all MIB openings is collected, as hereinafter described.
EXAMPLEThe following example is provided for illustration purposes only, and is not meant to limit the various embodiments of the present invention in any way. In an exemplary thickened impeller shroud of 0.280 inches thick, the geometry and orientation of an exemplary extended MIB opening may be as follows, with reference to the figures as indicated:
Geometry (FIGS. 9-11)
- d1=0.097 inch diameter at inlet section
- d2=0.137 inch diameter at outlet section
- L=0.329 inches
- Θ=3.5° (half angle)
- L/d1=3.4
- Area ratio=d22/d12=2.0
Centerline Orientation (FIGS. 12 a-12c) - angle (α) (
FIG. 12 a)=36° - First Rotation angle (β) (
FIG. 12 b)=20° - Second Rotation angle (γ) (
FIG. 12 c)=18° - Dimension x=2.8 inches
Referring again to
Referring specifically to
Referring specifically to
The impeller shroud may be formed prior to or substantially simultaneously with the step of providing at least one edge treatment. In addition, while “formation” of an impeller shroud is described, it is to be understood that the at least one edge treatment may be provided to at least one MIB opening in a commercially available impeller shroud having a plurality of MIB openings disposed therein.
Referring again to
The cooling circuit 40 of the compressor is in flow communication with both the centrifugal compressor 50 and turbine 20 (not shown in
The combustor 18 (not shown in
During operation of the gas turbine engine, as illustrated in
The gas turbine engine components are cooled with MIB cooling air supplied to the turbine (not shown in
The cooling circuit piping (not shown) channels the intermediate pressure cooling air 76 aftward to the turbine 20. The intermediate pressure cooling air 76 reduces turbine temperatures which improves mechanical capability and rotor durability. The desired temperature and pressure of cooling air 76 extracted mid-impeller are determined by the temperature and pressure requirements of the application for which the cooling air is to be used. While the cooling air is shown in
From the foregoing, it is to be appreciated that the gas turbine engines and methods for cooling components thereof with mid-impeller bleed (MIB) cooling air according to exemplary embodiments of the present invention provide improved pressure recovery by extracting cooling air through MIB openings having a configuration, geometry, and orientation according to exemplary embodiments as described herein. The MIB openings according to exemplary embodiments maximize pressure of the cooling air and reduce pressure losses thereof associated with cooling airflow entrance into and/or exit therefrom, thereby providing sufficient pressure for the turbine application for which the cooling air is intended and permitting use of thermodynamically less expensive cooling air, resulting in improving overall engine performance and effectively cooling the components of the gas turbine engine.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
Claims
1. A method for cooling components of a gas turbine engine with mid-impeller bleed (MIB) cooling air having a pressure, the gas turbine engine having a compressor comprising an impeller body and an impeller shroud at least partially surrounding the impeller body, the method comprising:
- providing at least one edge treatment to at least one MIB opening of a plurality of MIB openings disposed in the impeller shroud, the at least one edge treatment substantially preserving the pressure of the MIB cooling air during entrance into, discharge out of, or both entrance into and discharge out of the at least one MIB opening.
2. The method of claim 1, wherein the step of providing at least one edge treatment comprises providing the at least one edge treatment at one or both of a leading edge and a trailing edge of one or both of an entrance into and an exit out of the at least one MIB opening.
3. The method of claim 2, wherein the step of providing at least one edge treatment comprises providing a radial edge, an angled edge, or a combination thereof
4. The method of claim 1, further comprising the step of forming the impeller shroud prior to or substantially simultaneously with the step of providing at least one edge treatment.
5. The method of claim 4, wherein the step of forming the impeller shroud comprises forming the plurality of MIB openings disposed therein, each MIB opening of the plurality of MIB openings having an inlet section, an outlet section, and a conical diffuser section between the inlet and outlet sections, the entrance into the at least one MIB opening at the inlet section and the exit out of the at least one MIB opening at the outlet section.
6. The method of claim 5, wherein the step of forming the impeller shroud comprises orienting a centerline of each MIB opening of the plurality of MIB openings to be substantially aligned with an averaged local absolute flow velocity vector of the MIB cooling air at the inlet section of each MIB opening.
7. The method of claim 6, wherein the step of forming the impeller shroud comprises orienting the plurality of MIB openings to extend through the impeller shroud at a predetermined tangential angle, a predetermined axial angle, and a predetermined radial angle to extract the MIB cooling air in a direction that has a vector component in a tangential, an axial, and a radial flow direction.
8. The method of claim 7, wherein the step of forming the impeller shroud comprises forming a thickened impeller shroud and wherein the plurality of MIB openings comprise a plurality of extended MIB openings disposed in the thickened impeller shroud each having an extended inlet section, an extended outlet section, and an elongated conical diffuser section between the extended inlet and outlet sections.
9. The method of claim 8, wherein the step of providing at least one edge treatment comprises providing the at least one edge treatment to at least one extended MIB opening of the plurality of extended MIB openings disposed in the thickened impeller shroud.
10. The method of claim 9, wherein the step of providing at least one edge treatment comprises providing the at least one edge treatment at one or both of the leading edge and the trailing edge of one or both of the entrance into the extended inlet section and the exit of the extended outlet section.
11. The method of claim 10, wherein the step of providing at least one edge treatment comprises providing a radial edge, an angled edge, or a combination thereof
12. A gas turbine engine including a compressor that compresses inlet air into intermediate pressure cooling air and high pressure air, the intermediate pressure cooling air formed upstream of the high pressure air, the compressor comprising
- an impeller;
- an impeller shroud; and
- a plurality of MIB openings disposed in the impeller shroud and having a length co-terminating with a thickness of the impeller shroud, and each MIB opening of the plurality of MIB openings having an inlet section in flow communication with an engine flow path to extract the intermediate pressure cooling air therefrom, an outlet section in flow communication with a turbine, and a conical diffuser section between the inlet and outlet sections, at least one MIB opening of the plurality of MIB openings having at least one edge treatment.
13. The gas turbine engine of claim 12, wherein the at least one edge treatment is at one or both of a leading edge and a trailing edge of one or both of an entrance into the inlet section and an exit of the outlet section.
14. The gas turbine engine of claim 13, wherein the at least one edge treatment comprises a radial edge, an angled edge, or a combination thereof
15. The gas turbine engine of claim 12, wherein a centerline orientation of each MIB opening of the plurality of MIB openings is substantially aligned with an averaged local absolute flow velocity vector of the intermediate pressure cooling air to extract tangential, axial, and radial velocity flow components therefrom.
16. The gas turbine engine of claim 12, wherein the plurality of MIB openings comprise a plurality of extended MIB openings and the impeller shroud comprises a thickened impeller shroud.
17. The gas turbine engine of claim 16, wherein the inlet section and the outlet section of the plurality of extended MIB openings have an increased area and the conical diffuser section thereof is elongated.
18. A compressor for a gas turbine engine, the compressor comprising:
- an impeller body having an impeller exit;
- a thickened impeller shroud at least partially surrounding the impeller body and having a plurality of extended mid-impeller bleed (MIB) openings extending therethrough adapted to extract at least a portion of a tangential flow component, an axial flow component, and a radial flow component of cooling air from an engine flow path and disposed at a distance from the impeller exit, the plurality of extended MIB openings each having: an inlet section, an outlet section, and an elongated conical diffuser section between the inlet and outlet sections, the inlet section having a leading edge and a trailing edge at an entrance thereof and the outlet section having a leading edge and a trailing edge at an exit thereof; a centerline orientation adapted to be substantially aligned with an averaged local absolute flow velocity vector of the cooling air at the inlet section of the extended MIB opening.
19. The compressor of claim 18, wherein one or both of the leading and trailing edges at one or both of the entrance and exit of the extended MIB opening is shaped to define at least one edge treatment.
20. The compressor of claim 19, wherein the at least one edge treatment comprises a radial edge, an angled edge, or a combination thereof
Type: Application
Filed: Aug 25, 2011
Publication Date: Feb 28, 2013
Applicant: HONEYWELL INTERNATIONAL INC. (Morristown, NJ)
Inventors: Kin Poon (Tempe, AZ), Jeff Howe (Chandler, AZ), Michael T. Todd Barton (Phoenix, AZ), Frank Mignano (Phoenix, AZ), Mahmoud Mansour (Phoenix, AZ), Nick Nolcheff (Chandler, AZ), Scott Taylor (Phoenix, AZ), Steve Trzcinski (Gilbert, AZ), Ardeshir Riahi (Scottsdale, AZ), Jeff Guymon (Gilbert, AZ), Alan Hemmingson (Tempe, AZ), Alex Mirzamoghadam (Phoenix, AZ)
Application Number: 13/218,224
International Classification: F04D 27/02 (20060101); F01D 5/08 (20060101);