JP2012031855A - System and apparatus relating to diffuser in combustion turbine engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge diffuser.SOLUTION: The discharge diffuser includes: a forward section (101) and a dump cavity (110), the forward section (101) being configured to direct discharge from a compressor to the dump cavity (110); an inner diffuser wall (102) that forms an inner radial flowpath of the forward section (101); and an outer diffuser wall (104) that forms an outer radial flowpath of the forward section (101). The discharge diffuser includes an overhanging step (116) at an aft lip (113) of the inner diffuser wall (102).

Description

This application generally includes all types of combustion turbines or rotary engines, including gas turbine engines, aircraft engines, and others, unless otherwise stated as used herein. Related to turbine diffuser design.
More specifically, but not limited to, this application relates to turbine diffuser designs that provide robust diffuser and CDC performance.

  In general, a turbine engine includes a compressor that supplies highly pressurized air to a combustor for combustion with fuel. The resulting flow of hot gas from the combustor can drive the turbine and extract work from the turbine. The turbine engine can be configured with an axial compressor mechanically coupled to a downstream turbine by a common shaft or rotor and a combustor located between the compressor and the turbine. The air exits the compressor at a relatively high speed and usually utilizes a diffuser to initially reduce the velocity of the pressurized air flow and minimize subsequent pressure losses. The diffuser can include a splitter vane that divides the air flow into separate diffuser passages. The diffuser dump or cavity directs air to the annular channel surrounding the combustor after receiving an air flow from the diffuser and further decelerating there. Like the conventional one, the compressor is provided with an inner compressor discharge inner barrel and a compressor discharge casing (CDC). The CDC interconnects the inner barrel and the first stage nozzle.

  The main cause of loss and turbulence in the diffuser is vortex generation as the flow enters the diffuser dump cavity. The diffuser dump cavity has the highest diffusion gradient and causes vortex formation. As the fluid flow moves forward, a vortex grows and begins to interact with the upstream section of the diffuser. Eddy current growth lifts the fluid flow upstream of the diffuser dump region, causes high losses and causes pre-diffuser and CDC performance degradation.

US Pat. No. 5,737,915

  As a result, there is a need for improved systems and devices that trap eddy currents and prevent their growth in the diffuser dump cavity, thus reducing overall losses and ensuring robust diffuser performance. To do.

  Accordingly, this application describes a discharge diffuser that includes a forward section and a dump cavity, the forward section configured to direct discharge from the compressor to the dump cavity, the discharge diffuser being In addition, an inner diffuser wall defining a radially inner flow path of the upstream section and an outer diffuser wall defining a radially outer flow path of the upstream section, the discharge diffuser overhangs the rear lip of the inner diffuser wall. Including steps.

  The present application further describes a discharge diffuser that includes a forward section configured to direct compressor discharge from the compressor to a dump cavity, the forward section comprising an inner diffuser wall and an outer diffuser. The outer diffuser wall flares outwardly to form an enlarged flow path therethrough, the dump cavity includes an area of increased volume located downstream of the upstream section, the dump cavity The discharge diffuser includes an overhang step at a rear lip of the inner diffuser wall, and the overhang step has a step wall inclined radially inward and upstream from the rear lip. And the stepped wall undercuts a portion of the inner diffuser wall.

  These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments made in conjunction with the drawings and the claims.

  These and other features of the invention will be more fully understood and appreciated by careful consideration of the following detailed description of illustrative embodiments of the invention made in conjunction with the accompanying drawings. It will be.

1 shows an exemplary discharge diffuser for a combustor in a combustion turbine engine that includes a vortex trap or overhang stage according to embodiments of the present application. FIG. FIG. 4 illustrates an exemplary discharge diffuser including a vortex trap or overhang step according to another embodiment of the present application. FIG. 3 illustrates exemplary dimensions of various portions of a vortex trap or overhang step according to an exemplary embodiment of the present application. The figure which shows the fluid flow pattern in the conventional diffuser. FIG. 4 shows a fluid flow pattern in a discharge diffuser having a vortex trap or overhang step according to an exemplary embodiment of the present application.

  As an initial important matter, in order to clearly communicate the invention of this application, it is necessary to select terms that refer to and describe specific parts or machine components of the combustion turbine engine. Wherever possible, generic industry terms will be used and adopted to be consistent with their common meaning. However, all such terms should be given a broad meaning and should not be interpreted narrowly so that the meaning intended herein and the technical scope of the claims are unduly limited. Is not intended. Those skilled in the art will appreciate that certain components can often be expressed using several different terms. In addition, what can be described herein as a single part can be described as including and consisting of several component parts in another context, or What can be described herein as a multi-component part can be formed into a single part and in some cases referred to as a single part. Accordingly, in understanding the technical scope of the present invention described herein, not only the terms and descriptions presented, but also the structure, configuration, function, and / or use of the components illustrated herein. Please pay attention.

  Further, as used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of working fluid through the turbine. Thus, the term “downstream” means a direction that substantially corresponds to the direction of flow of the working fluid, and the term “upstream” means a direction that is generally opposite to the direction of flow of the working fluid. The terms “backward” and “forward” can be used to describe the relative position within the turbine engine. It will be appreciated that the compressor is generally represented as being located on the “front” side of the turbine engine, while the turbine section is located on the “rear” side. Thus, as used herein, “front” describes the position closer to the compressor, and “rear” describes the position closer to the turbine. The term “radial” means movement or position perpendicular to the axis. The term “radial” is often necessary to describe parts at different axial positions with respect to the axis. In this case, the first component is herein “radially inward” of the second component when the first component is closer to the axis than the second component. Or it can be described as “inward”. On the other hand, if the first component is farther from the axis than the second component, the first component is “radially outward” or “outward” of the second component. Can be described. The term “axial” means a movement or position parallel to the axis. Finally, the term “circumferential” means movement or position about an axis.

  FIG. 1 illustrates an exemplary compressor discharge diffuser 100 in a combustion turbine engine that includes a vortex trap or overhang stage according to an exemplary embodiment of the present application. The discharge diffuser 100 can guide pressurized fluid from a compressor (not shown) to a combustor (not shown). In general, the air in the turbine engine exits the compressor at a relatively high speed and enters the diffuser 100 where it is then decelerated.

  As indicated by the arrows in FIG. 1, the pressurized fluid first flows into the front section 101 of the discharge diffuser 100. The front section 101 can include an inner diffuser wall 102 and an outer diffuser wall 104. It will be appreciated that the outer diffuser wall 104 flares outward and the diffuser walls 102, 104 form an enlarged flow path through the front section 101, thereby slowing the incoming pressurized air. In addition, an annular splitter vane 105 can be included (as shown).

  The splitter vane 105 divides the front section 101 of the discharge diffuser 100 into two passages, a first passage 106 and a second passage 108, which pass the compressor discharge (fluid) into the dump cavity 110. Lead. (FIGS. 1-3 depict only a portion of the dump cavity 110, while FIGS. 4 and 5 illustrate additional areas of the dump cavity 110.) Part of this disclosure In this embodiment, the discharge diffuser 100 can include any number of splitter vanes, or alternatively, can include a single enlarged annular passage without splitter vanes.

  In general, the discharge diffuser 100 includes a dump cavity 110 that receives an air flow (shown by arrows) from the front section 101. It will be appreciated that in the dump cavity 110 air is directed into an annular channel surrounding the combustor. FIG. 1 shows a dump cavity 110 as a region of increased volume located approximately downstream of the rear end points of the inner diffuser wall 102 and the outer diffuser wall 104. The dump cavity 110 can include an inner cavity wall 112 that defines a radially inner boundary of the dump cavity 110 and, as described above, the dump cavity 110 can surround at least a portion of the combustor. The dump cavity 110 has a significantly higher diffusion gradient, which typically results in the formation of one or more vortices (not shown) during operation. Those skilled in the art will appreciate that such vortex formation is a major cause of losses and turbulence, which adversely affects engine efficiency. In general, as the fluid flow moves downstream, vortex flow grows and begins to interact with the upstream section 101 of the discharge diffuser 100, causing further efficiency degradation.

  The inner diffuser wall 102 terminates at a rear lip 113. As used herein, the rear lip 113 is a downstream or rear end point of the inner diffuser wall 102 as shown in FIGS. In some embodiments, the inner diffuser wall 102 can include a transition step 116 disposed immediately in front of the rear lip 113, as shown. It will be appreciated that the rear lip 113 provides a transition point from the front section 101 of the discharge diffuser 100 to the dump cavity 110. In a conventional design as shown in FIG. 4, a radial step is provided at this location, and this step has a step that is substantially aligned in the radial direction.

  According to embodiments of the present application, the discharge diffuser 100 includes an overhang step 116 that minimizes or traps eddy currents or prevents eddy current growth in this region, as further described below. . The overhang step 116 is generally inclined radially inward and upstream, as shown in the cross-sectional views of FIGS. 1-3, thereby undercutting the rear portion of the inner diffuser wall 102. including. More specifically, the overhang step 116 includes a step wall 118 that slopes from a starting point at the rear lip 113 of the inner diffuser wall 102 in a direction that includes both an inward component and an axial upstream component. The step wall 118 is connected at one end to the inner diffuser wall 102 and at the other end to the inner cavity wall 112 at the front edge (referred to herein as the dump cavity front edge 117). It will be appreciated that, according to embodiments of the present application, the axial position of the dump cavity front edge 117 is ahead of the axial position of the rear lip 113. Of course, it is this configuration that forms the overhang step 116, which in turn creates flow dynamics that reduce the formation of vortex flow by the diffuser 100 during engine operation.

  The step wall 118 can be planar as shown, and in a cross-sectional view, in particular forms an angle 306 with the radial reference line shown in FIG. As used herein, this angle will be referred to as the step wall angle 306. In the prior art, the step wall 118 is aligned with the radial reference line as described above, so the step wall angle 306 is approximately 0 °. In other conventional configurations (not shown), the step wall 118 forms a positive angle with the radial reference line, which is used herein. In this case, this means that the step wall 118 is inclined inward in the radial direction and backward. However, as taught in this application, the step wall 118 forms a negative angle with the radial reference line, which, as described above, is an overhang or undercut. Form. It has been found that configurations having a particular step wall angle 306 or step wall angle 306 within a certain range provide enhanced performance. For example, in one preferred embodiment, the step wall angle 306 includes a range of about −20 ° to −60 °. More preferably, the step wall angle 306 includes a range of about −30 ° to −50 °. In some applications, the ideal step wall angle 306 includes about −40 °. As will be described in more detail below, the slope of the step wall 118 forms a vortex trap that prevents vortex growth and prevents vortex flow from interacting with fluid in the forward section 101 of the diffuser 100.

  The rear lip 113 of the inner diffuser wall 102 can include several preferred configurations. In one configuration, as shown in FIG. 1, the rear lip 113 can have a smooth circular edge. In another preferred embodiment, as shown in FIG. 2, the rear lip 113 can have an acute edge. In yet another preferred embodiment, as shown in FIG. 3, the posterior lip 113 includes a substantially radially aligned flat surface. These alternative forms of the rear lip 113 have been verified to be effective in capturing vortex flow and reducing aerodynamic losses. Although these described configurations of the rear lip 113 represent a preferred embodiment, it will be appreciated that other configurations are possible.

  In a preferred embodiment, the shape of the connection formed between the step wall 118 and the inner cavity wall 112 as shown includes a circular fillet region. As will be appreciated, this can prevent stress concentration. Other configurations are also possible.

  Furthermore, flow pattern experiments and computer modeling have revealed that certain dimensions are particularly more effective than others in controlling or limiting vortex formation. FIG. 3 serves to illustrate exemplary dimensions of various portions of an exemplary eddy current trap 300 within the diffuser 100. For example, the radial height 312 of the overhang step 116 may be about 4-6 inches. More preferably, this radial height 312 can be about 4.4 inches. In some embodiments, the distance 302 between the transition step 114 and the rear lip 113 can be about 3.5-4.5 inches. More preferably, this distance 302 can be about 4 inches. In some embodiments, the flat edge height 304 (see FIG. 3) of the rear lip 113 can be between about 0 and 1 inch. More preferably, this height 304 can be about 0.5 inches. In some embodiments, the arcuate radius 308 formed between the step wall 118 and the inner cavity wall 112 can be about 0.5-2 inches. More desirably, this radius 308 may be about 1 inch. Further, the height 310 of the transition step 114 can be about 0.2 to 1 inch. More preferably, the height 310 can be approximately 0.5 inches. The above dimensions are optimal for minimizing overall losses due to eddy current (not shown) growth and limiting the interaction of the vortex with the upstream fluid flow. It will be appreciated that these dimensions can be varied depending on the application and that these dimensions are merely representative of the preferred method of implementation.

  FIG. 4 shows the fluid flow pattern in the conventional diffuser 400 and the experimental results. The conventional diffuser 400 includes a first passage 106 and a second passage 108 through which pressurized fluid travels to the dump cavity 110 as indicated by the arrows. A step 402 having a substantially radially oriented step wall connects the inner diffuser wall 102 to an inner cavity wall 112 of a dump cavity 110 that is inward relative to the inner diffuser wall 102. The dump cavity 110 has the highest diffusion gradient and causes vortex generation. A vortex 404 (represented by the shaded area) is formed proximate to the step 402 as fluid enters the dump cavity 110. The vortex 404 grows as the fluid moves downstream and begins to interact with the fluid in the front section of the conventional diffuser 400. The fluid flow backflowing in the dump cavity 110 ascends the step 402, which is a substantially vertical wall, so that it interacts with the upstream flow and helps further growth of the vortex 400. This interaction can be seen in FIG. 4, where fluid is shown flowing into the second passage 108. This growth of the vortex 404 lifts the flow upstream of the dump cavity 110, resulting in significant losses and reduced pre-diffuser and CDC performance.

  FIG. 5 shows a fluid flow pattern and its experimental results in the diffuser 100 according to an embodiment of the present application. As described above, the first leg 118 may be inclined radially inward and upstream such that the first leg 118 undercuts a portion of the inner diffuser wall 102. Further, the rear lip 113 can have an axial position that is rearward relative to the dump cavity front end edge 117. FIG. 5 shows a relaxed vortex flow 502 formed in close proximity to the step wall 118. The slope of the step wall 118 forms a vortex trap in the dump cavity 110 to prevent the growth of the relaxed vortex 502 and prevent the vortex interaction with the forward section 101 of the diffuser 100. FIG. 5 shows that the relaxed vortex 502 is substantially independent of the second passage 108 as compared to the vortex 404 in FIG. 4, which has a large interaction with the second passage 108. This comparison shows that this design of the diffuser 100 can prevent the growth of the relaxed vortex 502 and make the relaxed vortex 502 substantially independent of the upstream fluid flow. ing.

  This design of the diffuser 100 also allows for uniform flow distribution across the transition piece 504 and prevents hot spot formation. The resulting flow region reduces overall losses and improves diffuser 100 performance. Suppressing the relaxed vortex flow 502 frees you from the strict requirement to have a uniform flow profile in the compressor without adversely affecting performance. Loss reduction in the CDC also allows for higher loss margins when designing the compressor or combustor, which can provide significant performance and economic benefits.

  Table 1 compares the performance of the conventional diffuser 400 with the performance of the diffuser 100. There are four possible scenarios with different leakage levels between the airfoil and CDC at S14 set in the 14th stator (S14) of the compressor. The 0.3% leakage in S14 is a design point in the present embodiment. The pressure loss is obtained by the following formula 1.

Note that in general, great efforts have been made to maintain such low level leakage uniformly. Loss reduction in the diffuser 100 can provide some degree of freedom in compressor and combustor design and can further alleviate the stringent requirements for maintaining leakage levels.

  Table 1 shows that the diffuser 100 reduces pressure loss due to eddy current growth compared to the conventional diffuser 400. Note that the claimed diffuser design provides robust performance not only at the design point, but also over various operating conditions. Accordingly, the diffuser 100 according to embodiments of the present disclosure inhibits vortex growth and limits interaction with upstream vortex flow, resulting in significant improvements in diffuser and CDC performance.

  As will be appreciated by those skilled in the art, many of the various features and configurations described above with respect to some exemplary embodiments may be further selectively applied to form other possible embodiments of the present invention. Can do. For brevity and in view of the ability of those skilled in the art, all possible iterations have not been shown or discussed in detail, but all combinations and implementations encompassed by some claims or others are possible. These embodiments are intended to be part of this application. In addition, from the above description of several exemplary embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are also intended to be covered by the appended claims. Further, the foregoing description is only for the described embodiments of the present application, and without departing from the technical idea and the technical scope of the present application, which is defined by the appended claims and their equivalents. It will be apparent that many changes and modifications can be made in the book.

100 compressor discharge diffuser 101 forward section 102 inner diffuser wall 104 outer diffuser wall 105 annular splitter vane 106 first passage 108 second passage 110 dump cavity 112 inner cavity wall 113 rear lip 114 transition step 116 overhang step 118 step Wall 117 Step cavity forward edge 300 Eddy trap 302 Width 304 Flat edge height 306 Angle 307 Radial axis 308 Radius 310 Height 312 Radial distance 400 Conventional diffuser 402 Step 404 Eddy current 500 Fluid Flow pattern 502 Relaxed vortex flow 504 Transition piece

Claims (12)

A discharge diffuser in a combustion turbine engine comprising a compressor, a combustor and a turbine,
Including a forward section (101) and a dump cavity (110);
The forward section (101) is configured to direct discharge from the compressor to the dump cavity (110);
The discharge diffuser is
An inner diffuser wall (102) defining a radially inner flow path of the front section (101);
An outer diffuser wall (104) forming a radially outer flow path of the front section (101);
The discharge diffuser includes an overhang step (116) at a rear lip (113) of the inner diffuser wall (102).
Discharge diffuser. The outer diffuser wall (104) flares outward, and the inner diffuser wall (102) and the outer diffuser wall (104) form an enlarged flow path,
The rear lip (113) includes a downstream termination point of the inner diffuser wall (102);
The dump cavity (110) includes a region of increased volume located downstream of the flared inner and outer diffuser walls (102, 104) of the front section (101), and the dump cavity (110) Configured to surround at least a portion of the vessel,
The discharge diffuser according to claim 1. The overhang step (116) includes a step wall (118) extending from a rear lip (113) of the front section (101) to an inner cavity wall (112) of the dump cavity (110);
The inner cavity wall (112) includes a radially inner boundary of the dump cavity (110);
The discharge diffuser according to claim 1.   The step wall (118) includes a radial step that is inclined from a starting point at a rear lip (113) of the inner diffuser wall (102) in a direction including both an inward component and an axial upstream component. The discharge diffuser according to claim 3.   The overhang step (116) includes a radial step inclined radially inward and upstream from the rear lip (113), the radial step being a portion of the inner diffuser wall (102). The discharge diffuser according to claim 3, wherein undercutting is performed. The dump cavity (110) includes an inner cavity wall (112) that forms a radially inner boundary of the dump cavity (110), and the overhang step (116) connects the inner diffuser wall (102) to the Including a step wall (118) coupled to the inner cavity wall (112);
The discharge diffuser according to claim 1. The inner cavity wall (112) includes a position that is inward relative to the inner diffuser wall (102);
The radial height of the overhang step (116) includes the distance that the inner cavity wall (112) is closer to the inside of the inner diffuser wall (102) by that amount, and the step wall (118) ) At one end thereof to the inner diffuser wall (102) at the rear lip (113) and at the other end to the inner cavity wall (112) at the dump cavity front edge (117).
The discharge diffuser according to claim 6.   The overhang step (116) is configured such that the rear lip (113) includes an axial position that is rearward relative to an axial position of the dump cavity front edge (117). Discharge diffuser as described. The step wall (118) comprises a substantially planar shape;
The step wall angle (306) includes an angle formed between a plane of the step wall (118) and a radial orientation reference line, and the overhang step (116) includes the step wall angle. (306) is configured to include a range of 20-60 degrees;
The discharge diffuser according to claim 8. The step wall (118) comprises a substantially planar shape;
The step wall angle (306) includes an angle formed between a plane of the step wall (118) and a radial orientation reference line, and the overhang step (116) includes the step wall angle. (306) is configured to include a range of 30-50 degrees;
The discharge diffuser according to claim 8. The rear lip (113) includes one of a circular edge, an acute edge, and a radially aligned flat edge, and the dump cavity front edge (117) includes a filleted edge. Including,
The discharge diffuser according to claim 8. A radial height of the overhang step (116) comprises 4 to 6 inches;
A radial height of the overhang step (116) further comprises a transition step (114) installed on the inner diffuser wall (102);
The distance between the transition step (114) installed on the inner diffuser wall (102) and the rear lip (113) comprises 3.5 to 4.5 inches, and the transition step ( 114) includes a radial height of about 0.5 inches;
The discharge diffuser according to claim 8.