Turbomachine with compressor diffuser bleed for uniform exit flow

A bleed arrangement for a turbomachine that results in uniform flow to the combustor. A turbomachine includes a compressor, a combustor disposed to receive the compressed air from the compressor through a flow path, and a diffuser disposed in the flow path between the compressor and the combustor. A number of bleed holes are disposed downstream in the flow path from the diffuser and are configured to direct bleed air compressed by the compressor away from the combustor. The number of bleed holes have a plural number of sizes configured to provide uniform compressor exit flow distribution around a circumference of the diffuser.

TECHNICAL FIELD

Embodiments of the subject matter described herein generally relate to turbomachinery air flow. More particularly, embodiments of the subject matter relate to the configuration of bleed openings to minimize nonuniformity in deswirl exit flow directed to the combustor.

BACKGROUND

A turbomachine such as a gas turbine engine may be used to power various types of vehicles and/or systems. Gas turbine engines typically include a compressor that receives and compresses incoming gas such as air, a combustor in which the compressed gas is mixed with fuel and burned to produce high-pressure and high-velocity exhaust gas, and one or more turbines that extract energy from the gas exiting the combustor.

Diffusers are employed in compression systems to reduce the velocity of compressed airflow, while increasing static pressure prior to delivery of the airflow into, for example, a combustion section of the gas turbine engine. Diffusers typically contain a plurality of airfoils or vanes, which are arranged in an annular array between two annular plates. Collectively, the vanes and the plates form an annular flowbody with a number of flow passages, which includes inlets distributed along its inner periphery and outlets distributed along outer periphery. Diffuser flow passages or channels connect the diffuser inlets to the diffuser outlets, with adjacent passages partitioned or separated by the vanes. The vanes are dimensioned and shaped such that the diffuser flow passages increase in cross-sectional flow area, moving from the inlets toward the outlets, to provide the desired diffusion functionality as compressed airflow is directed through the diffuser.

Diffusers are commonly utilized within gas turbine engines and other turbomachines containing impellers or other compressor rotors. A given diffuser may be positioned around a compressor impeller to receive the compressed airflow discharged therefrom. The airflow decelerates and static pressure increases as the airflow passes through the diffuser. The airflow may further be conditioned by other components, such as a deswirl section, contained in the gas turbine engine and located downstream of the diffuser. The deswirl section may itself contain a number of vanes that further condition the airflow prior to its delivery to the combustor. After deswirl, the air flow is delivered into the combustor, injected with a fuel mist, and ignited to generate combustive gasses.

Air may be bled from the compressor section for a variety of purposes. Bleeding air may lead to nonuniformity in the air flow leaving the compressor section as it is directed to the combustor. The operation of the combustor is a function of the airflow delivered to it. For example, the combustor preferably receives a consistent air flow rate as the compressor impeller rotates.

Accordingly, it is desirable to deliver uniform flow to a gas turbine engines combustor including in engines with bleed taken from the compressor's exit/diffuser area. It is also desirable to deliver uniform air to the combustor to enable a lower pattern factor at the turbine inlet. A lower pattern factor reduces the intensity of the hot streak entering the turbine and increases turbine durability. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.

BRIEF SUMMARY

This summary is provided to describe select concepts in a simplified form that are further described in the Detailed Description section of this disclosure. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In a number of embodiments, a turbomachine includes a compressor, a combustor disposed to receive the compressed air from the compressor through a flow path, and a diffuser disposed in the flow path between the compressor and the combustor. A number of bleed holes are disposed downstream in the flow path from the diffuser and are configured to direct bleed air compressed by the compressor away from the combustor. The bleed holes have a plural number of sizes configured to provide uniform compressor exit flow distribution around a circumference of the diffuser.

In a number of additional embodiments, a turbomachine includes a compressor configured to compress air. A combustor is disposed to receive the compressed air from the compressor through a flow path. A diffuser is disposed in the flow path between the compressor and the combustor, and directs the air through the flow path. A deswirl section is disposed in the flow path between the diffuser and the combustor and receives the air directed by the diffuser. A bleed system is disposed to receive a feed air flow. A plenum is disposed between the bleed system and the flow path. A number of bleed holes are disposed downstream in the flow path from the diffuser and are configured to bleed the feed air flow, as compressed by the compressor, away from the combustor. The bleed holes are formed in a plural number of sizes and are configured to provide uniform compressor exit flow distribution around a circumference of the diffuser. The bleed holes provide the feed air flow to the plenum, where an amount of the feed air delivered to the plenum from each of the passages is approximately equal.

In a number of other embodiments, a turbomachine includes a compressor configured to compress air. A combustor is disposed to receive the compressed air from the compressor through a flow path. A diffuser is disposed in the flow path between the compressor and the combustor. Vanes are distributed circumferentially around the compressor with a flow passage defined between each adjacent two of the vanes. A cover defines a plenum. Bleed holes extend through the cover and are disposed to bleed air from a point downstream in the flow path from the diffuser, and are configured to direct the bleed air compressed by the compressor away from the combustor. The bleed holes have a plural number of sizes configured to provide uniform compressor exit flow distribution around a circumference of the diffuser and are disposed in the flow passages to provide a feed air flow to the plenum. An amount of the feed air delivered to the plenum from each of the passages is approximately equal.

DETAILED DESCRIPTION

In a number of embodiments, turbomachine compressor bleed is configured to avoid flow nonuniformity in the core flow directed to the combustor. Attaining a uniform exit flow condition, such as at the exit of deswirl, optimizes combustor performance and hot-section turbine component durability. The approach is adaptable to various diffuser bleed flow designs and is compatible with left-hand or right-hand engine bleed sources. Varying bleed hole diameters distributed circumferentially, substantially reduces unwanted effects on diffuser performance. In addition, the total area of the bleed holes minimizes disruption of the flow distribution and leads to an acceptable plenum pressure drop (e.g., <5 psid/34.5 kiloPascal), approximately, when the bleed flow is activated/initiated. The pattern factor of the combustor as a result of the resulting uniform bleed extraction is very small and acceptable, which may not otherwise be the case with nonuniform flow conditions.

In embodiments and examples described herein, applications such as turbomachines may be described in association with an aircraft gas turbine engine, but the disclosure is not limited in utility to such an application. In the example of a gas turbine engine with bleed from the diffuser area of a centrifugal compressor, the variation of bleed hole sizes offsets circumferentially distributed flow variations that may otherwise result from bleed draws. The embodiments disclosed herein have applicability where uniform flow downstream from bleed holes is similarly desirable. For example, various other engine environments, as well as different types of rotating or otherwise moving machinery will benefit from the features described herein. Thus, no particular feature or characteristic is constrained to an aircraft, or an aircraft engine, and the principles disclosed herein may be embodied in other vehicles, and/or in other turbomachinery or equipment.

A schematic, partially sectioned view of an engine assembly20is shown inFIG.1according to an exemplary embodiment. The engine assembly20in general, includes an inlet section22, a gearbox24, a compressor section26, a combustion section30, a turbine section32, a shaft35, and an exhaust section34, all of which may be disposed within, or defined by, a cowling28(with various internal shrouding not shown). The compressor section26, the combustion section30, the turbine section32, and the exhaust section34may collectively be referred to as the engine core36. During operation, air enters the inlet section22from atmosphere and is directed into the compressor section26. The compressor section26may include one or more rotors or impellers or a series of compressor rotors and/or impellers that increase the pressure of the air, which is then directed toward the combustion section30, such as through a diffuser38. Air/gases generally flow through the core36. Air directed out of the core36may be referred to as bleed. The engine assembly may include a number of additional components that are not illustrated for simplicity. For example, an inlet guide vane section may be located upstream of the compressor section26.

Referring additionally toFIG.2along withFIG.1, the compressor section26includes a compressor44configured as an axi-centrifugal compression system with axial rotor(s)43with at least one centrifugal impeller40rotating about an axis42. In other embodiments, any number of stages including a single stage may be employed. The impeller40rotates imparting a tangential velocity to the air46received from the inlet section22and a shroud48around the impeller40directs the air radially outward into the diffuser38, which includes a number of circumferentially distributed diffuser vanes50(also illustrated inFIG.4), defining flow passages of a flow path to the combustion section30. The diffuser38directs the air through the flow path into a deswirl section52. The deswirl section52includes another set of circumferentially distributed vanes54to straighten the flow leaving the compressor section26and directed through the flow path to the combustion section30.

In the combustion section30, the straightened high-pressure air from the compressor section26is mixed with fuel and combusted in a combustor56. The gases from the combusted fuel and air are then directed into the turbine section32. The turbine section32includes a rotor58with a series of turbines, which may be disposed in axial flow series or in other arrangements and which also rotate about the axis42, which in this embodiment is a common axis42with the compressor44. The combustion gas60from the combustion section30expands through, and rotates, the rotor58of the turbine section32, from which power is derived. From the turbine section32, the air/gas62is then exhausted from the engine core36through the exhaust section34to the atmosphere.

As shown inFIGS.1and2, the engine assembly20includes a bleed system68with a number of loads for using the bleed air. In this embodiment, some of the air compressed by the compressor44is selectively directed to an inertial particle separator70. The inertial particle separator70may be selectively operated on an intermittent basis when needed to remove particulate from the air46received at the inlet section22. Also in this embodiment, some of the air compressed by the compressor44is selectively directed to an engine anti-ice system72. The anti-ice system72may be located at positions such as upstream of the inlet section22, in the inertial particle separator70or in the inlet guide vane section of the compressor44. The engine anti-ice system72may be selectively operated on an intermittent basis when needed to prevent icing. In additional embodiments, other or additional systems may be included in the bleed system68that use bleed air from the compressor44.

The bleed system68draws bleed air74from a plenum76through bleed port(s) including a bleed port81that is/are open to the plenum76. The plenum76is defined by various components including a cover78and a wall79. Feed air80is received into the plenum76through bleed holes (represented by bleed hole101), through the wall79. The bleed holes (e.g., bleed hole101) extract the feed air80from the flow path in the diffuser exit region88(shown inFIG.4), and may be located downstream from the diffuser vanes50. The feed air80is extracted in the exit region88, such as downstream of the throats of the passages90(shown inFIG.4). In some embodiments, the feed air80may be extracted downstream of the deswirl section52, with the bleed holes101et al. located downstream of the deswirl section52, with the plenum76configured to receive the feed air80. As such, the plenum76provides the bleed air74flow for selective draw by the inertial particle separator70and/or the anti-ice system72, and/or other systems of the bleed system68.

Referring toFIG.3, a schematic, axial cross section illustrates the location of the plenum76relative to the axis42and shows that it is annular in shape. The illustration shows the cover78as viewed in an axial direction from the inside of the plenum76. The bleed port81, along with bleed ports82,83,84and85are distributed circumferentially (in circumferential direction86), around the plenum76and provide openings through the cover78. The bleed ports81-85are irregularly spaced around the plenum76. Accordingly, when the systems coupled with the bleed ports81-85selectively draw air through any number of the bleed ports81-85, that air is extracted at certain locations around the circumference of the compressor section26. In the current embodiment, the bleed ports81-85are defined to support both right-hand and left-hand positions of the engine assembly20. As a result, the use of the bleed ports81-85, and the amount of air they pull, may vary. For example when on one side of the associated aircraft, bleed port81may be connected with, and supply, the inertial particle separator70, while when on the other side of the aircraft, bleed port85may be connected with, and supply, the inertial particle separator.

Each of the bleed ports81-85when active, may draw a different amount of air as compared to others of the bleed ports81-85. In addition, the bleed ports81-85may not all be active simultaneously (and each may be intermittently activated), with some drawing bleed air74while others do not. When bleed air74is drawn, a resulting pressure drop may occur across the bleed holes101et al., in the area of the active bleed port(s)81-85. Such a pressure drop would act to draw the feed air80through those of the bleed holes101-150(seeFIG.4), in the area of the active bleed port(s)81-85. If not compensated for, this would result in the diffuser flow channels/passages at the radial location(s) of those bleed holes101-150delivering a different amount of core flow than other flow channels around the diffuser38, which would supply nonuniform flow to the combustion section30.

Referring toFIG.4, a schematic cross section is shown through the area of the diffuser38. The illustration shows the wall79and the bleed holes101-150as viewed in an axial direction from the inside of the diffuser38. In this view the bleed ports81-85are located in the foreground relative to the plane ofFIG.4. As shown, the diffuser38includes the number of vanes50disposed around the circumference of the compressor section26radially outward from the impeller40(which itself includes a number of vanes that aren't illustrated). An exit region88of the diffuser38is an area where the air exits the diffuser38and includes the transition out of the diffuser38. The vanes50define a number of flow passages90between each pair of adjacent vanes50through which flow from the impeller40is directed. In the current embodiment, the diffuser38includes twenty-five vanes50and twenty-five flow passages90. In other embodiments a different number of passages90may be included.

The bleed holes101-150are distributed around the circumference of the compressor section26. The bleed holes101-150are circumferentially distributed, in the circumferential direction86, with spacings that may be the same or that may vary.FIG.4illustrates an embodiment showing the bleed holes101-150and their location with respect to diffuser exit region88in the depicted orientation. In embodiments, the exit region88may overlap the downstream ends94(at their radially outermost, trailing ends) of the vanes50. The bleed holes101-150allow air to pass from the passages90into the plenum76. In the current embodiment there are two of the bleed holes101-150in each one of the passages90. In other embodiments, a different number of individual bleed holes101-50may be included in each of the passages90. For example, one or more bleed holes101-50are included in each passage90. In general, each passage90has at least one bleed hole and the total number of all bleed holes is a multiple (e.g., 1 times, 2 times, 3 times, . . . ) of the number of vanes50. In addition, the bleed holes101-150are sized differently depending on where they are located relative to the bleed ports81-85.

Referring additionally toFIG.5, a meridional section is shown through one passage90. In the current embodiment, the bleed holes101-150are located in the exit region88radially outward from the diffuser38and at the downstream (radially outward) ends94of the vanes50at the outlet from the passages90in the exit region88of the vanes50. In embodiments, the bleed holes101-150are located closer to the downstream ends94than to the upstream ends96. The bleed holes101-150are configured to minimize losses on the bleed side (the feed air80, the plenum76and the bleed air74), and to minimize the impact on the core flow side (flow to the combustor56). In general, this is accomplished by forming the bleed holes101-150in a variety of different sizes with larger bleed holes101-150located further away from the circumferential locations of the bleed ports81-85and smaller bleed holes101-150located closer to the bleed ports81-85, The result is that the flow through the passages90is consistent around the circumference of the deswirl section52and around the diffuser38, and as delivered to the combustion section30. The benefits also result from the radial location of the bleed holes101-150downstream in the exit region88of the diffuser38and upstream from or in the deswirl section52.

In the current embodiment, the bleed holes101-150are formed in three different sizes (diameters). It should be appreciated that the size of the bleed holes101-150, the number of different sizes included, and the specific bleed hole sizes and their locations are parameters determined for each specific application and will therefore vary between applications. The sizes are determined to result in bleed flow rates through different bleed holes101-1:50for a uniform exit flow condition at the exit of deswirl section52. In general, those of the bleed holes101-150located closer to the circumferential position of a bleed port81-85are relatively larger, and those located further from the bleed ports81-85are relatively smaller. In spite of their different sizes, each of the bleed holes delivers substantially the same flow rate to the plenum76. In one exemplary embodiment, the bleed holes108-111and138-143have diameters of 7.54 millimeters (19/64 inch); the bleed holes101-107,112-113,130-137and144-150have diameters of 8.33 millimeters (21/64 inch); and the bleed holes114-129have diameters of 9.52 millimeters (⅜ inch). As such, the sizes of the bleed holes101-150vary in a non-symmetrical pattern around the circumference of the compressor44. The smallest of the bleed holes108-111are located in the vicinity of the bleed port81, which, in this embodiment, has the highest bleed air74flow rate. In other embodiments for application of the engine system20, the smallest of the bleed holes may be in the vicinity of another bleed port, such as bleed port85. The largest of the bleed holes114-129are located in the area of bleed ports82-83, which have the lowest bleed air74flow. The medium sized bleed holes101-107,112-113,130-137and144-150are located in circumferential positions as groupings between groupings of the largest bleed holes114-129and smallest bleed holes108-111and138-143. The largest bleed holes114-129have an open area (71.18 square millimeters) that is 59% larger than the size of the open area (44.65 square millimeters) of the smallest bleed holes108-111. The sizing of the bleed holes101-150at their various locations may be determined using computational fluid dynamics software knowing the physical dimensions of the compressor stage, the bleed air74flow rates through the bleed ports81-85and the output of the impeller40. The result is that the flow rate through the passages90is uniform where each passage90has approximately the same flow rate around the circumference of the compressor section26so that non-uniformity in the flow to the combustion section30is avoided, even when bleed air74flow is active. Variation in the sizes of the bleed holes101-150minimizes disruption of the compressor exit flow distribution and the total bleed area allows an acceptable plenum76pressure drop when the bleeds are activated. For example, an acceptable/low pressure drop of less than 5 psid/34.5 kPa), approximately may occur.

Referring toFIG.6, a graph160shows deviation from average bleed hole flow normalizing the data as a percent of total flow from the compressor on the vertical axis162versus bleed hole number on the horizontal axis164. In summary, the bleed holes101-150each have a flow that is approximately the same. The flow distribution is shown for each bleed hole101-150for both a right-hand application (by the solid dots), and a left-hand application (by the outline dots), of the engine assembly20, The flow through each bleed hole101-150is represented by the dots as a data point for a percentage variance from the average bleed hole mass flow rate, relative to total flow exiting the compressor (e.g., bleed hole flow minus average bleed hole flow/total compressor flow). The flow through the various bleed holes101-150varies approximately ±0.03% of the total flow through the compressor44for either a right-hand application or a left-hand application. This minor variation results in uniform flow to the combustor56around the circumference of the diffuser38/deswirl section52. It also means that the amount of flow delivered through each of the bleed holes101-1.50and from each of the passages90, is approximately equal.

Referring toFIG.7, aspects of the diffuser38and its exit region88are schematically shown in cross-section showing the positioning of bleed holes138-141in the exit region88. The exit region88begins, and extends downstream from a cover passage exit designated by a reference line170that extends across the passage90from a point172at the trailing end of one vane50to the closest point174on an adjacent vane50. The bleed holes138-141are shown as representatives of the bleed holes101-150. The vanes50each have a suction surface152and an opposite pressure surface154. The bleed holes101-150are not evenly spaced circumferentially. As shown the pair139and140is offset toward one vane50versus the other. For example, the pair139and140may be located further away from the suction surface152and closer to the pressure surface154to reduce impact on centrifugal compressor performance and operability. In other embodiments depending on the specifics of the application, the pair139and140may be positioned differently. In this case, the distance156from the suction surface152to the bleed hole140is greater than the distance158from the pressure surface154to the bleed hole139.

Accordingly, locating and sizing bleed holes results in minimized losses on the bleed side and minimized impact on the core flow side of a gas turbine engine with a centrifugal compressor. The bleed associated with each diffuser passage, downstream of the centrifugal compressor impeller, results in a uniform flow to the combustor at all circumferential positions. While at least one exemplary embodiment has been presented in the foregoing detailed description of the inventive subject matter, 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 inventive subject matter 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 inventive subject matter. 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 inventive subject matter as set forth in the appended claims.