JP2011052689A - High-turning diffuser strut equipped with flow crossover slot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turning strut (50") used in a diffuser (42) of a turbine engine. <P>SOLUTION: This high-turning diffuser strut is constituted in such a way that a first surface and a second surface (74, 76) opposing to each other are suspended from a leading edge (72) of the turning strut (50") and terminate at a trailing edge (78) of it, the slot (80) is extended by passing through the turning strut (50"), and its volume is reduced from the first surface (74) to the second surface (76). During turndown operation, an exhaust air stream collides with the leading edge (72) at a deflection swirl angle, pressure of the exhaust air stream on the first surface (74) becomes higher than that on the second surface (76), and the exhaust air stream flows by passing through the slot (80). The exhaust air stream passing through the slot (80) is accelerated due to the reduction of volume of the slot (80) and joins the exhaust air stream on the second surface (76). Momentum of the exhaust air stream on the second surface (76) is increased to maintain a second laminar flow boundary layer (92) on the second surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The subject matter described herein relates to turbine engines, and more particularly to turning struts in a diffuser of a turbine engine.

  A gas turbine engine includes a compressor having a plurality of compressor blades disposed on a shaft, the compressor blades and the shaft being configured to form a gradually decreasing volume. The air stream drawn into the gas turbine is pressurized as the air stream flows through the compressor. A plurality of combustors are arranged downstream of the compressor, where air and fuel are mixed and fuel is ignited and burned, as is known. A multi-stage turbine is arranged downstream of the combustor. The first stage of the multi-stage turbine is formed by a plurality of turbine vanes arranged on the compressor shaft. The final stage of the multi-stage turbine is formed by a plurality of turbine vanes arranged on an output drive shaft that rotates independently of the compressor shaft. The heated pressurized air stream from the combustor rotates the multi-stage turbine. The rotation of the first stage of the multistage turbine rotates the shaft of the compressor. The final stage rotation of the multi-stage turbine rotates the output drive shaft, which in turn drives the generator. A diffuser is disposed behind the last stage of the multi-stage turbine and is configured to decelerate the exhaust flow and convert dynamic energy into a static pressure increase. The diffuser includes a plurality of turning struts consisting of support struts surrounded by aerodynamic fairings. The diverting struts redirect the flow from the multistage turbine in the axial direction when operating the gas turbine engine within the design performance range. The turning struts are arranged circumferentially within the annular space of the diffuser.

US Pat. No. 5,813,828

  According to one aspect of the invention, a turning strut for use in a turbine engine diffuser includes a curved leading edge, a first tapered surface depending from the curved leading edge at one end thereof, and at one end thereof. It has the 2nd taper surface drooping from the curve front edge, and the rear edge formed in the other end part of the 1st and 2nd taper surface. The second tapered surface is disposed opposite the first tapered surface. At least one slot extends through the diverting strut from the first tapered surface to the second tapered surface. At least one slot has a reduced volume from the first tapered surface to the second tapered surface. At least one slot is disposed proximate to the curved leading edge.

  In accordance with another aspect of the present invention, a method for redirecting flow in a diffuser of a turbine engine includes impinging flow against a leading edge of a diverting strut at a swivel angle that is deviated from a design point swivel angle. The method further includes forming a first laminar boundary layer at the first tapered surface by the flow at the first tapered surface of the turning strut, and the flow at the second tapered surface of the turning strut. Forming a second laminar boundary layer at the second tapered surface. The first tapered surface depends from the front edge at one end thereof. The second tapered surface depends from the front edge at one end thereof. The second surface is disposed to face the first surface. The deflection swivel angle creates a pressure difference between the flows at the first and second surfaces. The flow at the first surface is at a higher pressure than the flow at the second surface. The method includes creating a flow through at least one slot extending from the first surface to the second surface through the turning struts. The flow through the at least one slot is from the first surface to the second surface and is the result of a pressure difference between the flows at the first and second surfaces. The method further includes accelerating the flow through the at least one slot by reducing the volume of the at least one slot from the first surface to the second surface. The method further includes the step of merging the flow from the at least one slot with the flow at the second surface. The momentum of the flow at the second surface is increased to maintain a second laminar boundary layer on the second surface.

  According to yet another aspect of the present invention, a turning strut for use in a turbine engine diffuser is generally elongated having first and second surfaces formed by a leading edge and depending from the leading edge. It has a teardrop shape, the second surface is disposed opposite the first surface, and the first and second surfaces terminate at the trailing edge. At least one slot extends from the first surface to the second surface through the turning strut. At least one slot has a reduced volume from the first surface to the second surface. At least one slot is disposed proximate to the leading edge.

  These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

  The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the claims appended hereto. The foregoing and other features and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings.

1 is a schematic cross-sectional view of a typical gas turbine engine with a diffuser. 1 is a schematic cross-sectional view of a prior art turning strut operating at a design point pivot angle. FIG. FIG. 3 is a schematic cross-sectional view of the turning strut of FIG. 2 operating at a turning angle deviated from the design point turning angle. 1 is a schematic cross-sectional view of an embodiment of a turning strut of the present invention operating at a design point pivot angle. FIG. FIG. 5 is a partial side view of the direction change strut of FIG. 4. FIG. 5 is another partial side view of the turning strut of FIG. 4. FIG. 5 is a schematic cross-sectional view of the turning strut of FIG. 4 operating at a turning angle deviated from the design point turning angle.

  The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

  Referring to FIG. 1, a high power gas turbine engine is indicated generally by the reference numeral 10. The gas turbine engine 10 has a generally annular shape formed by an outer turbine casing 12. An inlet 14 is formed at one end of the gas turbine engine 10. The inlet 14 leads to a compressor 16 formed by a plurality of compressor blades 18 disposed within the casing 12. The compressor blade 18 is disposed on a shaft 20 that extends along the centerline 22 of the casing 12, and the compressor blade 18 and the shaft 20 are configured to form a gradually decreasing volume. The air flow drawn into the gas turbine engine 10 at the inlet 14 is pressurized as the air flow passes through the compressor 16. A plurality of combustors 24 are disposed downstream of the compressor 16 and are disposed axially around the shaft 20. The combustor 24 has a premixing chamber and a combustion chamber (both not shown). The air flow from the compressor 16 is sucked into the premixing chamber through the inlet port 26. Further, fuel from the fuel inlet 28 is fed into the premixing chamber. As is well known, the air and fuel are mixed in the premixing chamber to form a fuel and air mixture, and this fuel and air mixture flows into the combustion chamber and is ignited and combusted in the combustion chamber. A multi-stage turbine 30 is disposed in the casing 12 downstream of the combustor 24. The first stage 32 of the multistage turbine 30 is formed by a plurality of turbine vanes 34 disposed on the shaft 20. The final stage 36 of the multistage turbine 30 is formed by a plurality of turbine vanes 38 disposed on the output drive shaft 40. The output drive shaft 40 also extends along the centerline 22 of the casing 12 because the output drive shaft 40 is axially aligned with the shaft 20 but rotates independently of the shaft 20. The heated pressurized air flow from the combustor 24 rotates the multistage turbine 30. The rotation of the first stage 32 of the multi-stage turbine 30 rotates the shaft 20, which in turn drives the compressor 16. The rotation of the final stage 36 of the multi-stage turbine 30 rotates the output drive shaft 40, which in turn drives a generator (not shown). A diffuser 42 is disposed behind the final stage 36 of the multi-stage turbine 30 and is configured to decelerate the exhaust flow and convert dynamic energy into a static pressure increase. The diffuser 42 includes a plurality of turning struts 50 comprised of support struts surrounded by aerodynamic fairings. The turning strut 50 turns the flow 44 from the multi-stage turbine 30 in the axial direction to generate the flow 46 when the gas turbine engine 10 is operating within the design performance range. The direction changing strut 50 is disposed in the circumferential direction in the annular space of the diffuser 42.

  Referring to FIG. 2, a prior art turning strut represented by reference numeral 50 'is shown in schematic cross-section as having an overall elongated teardrop shape. The turning strut 50 ′ has a curved front (edge) surface 52 that leads to tapered surfaces 54 and 56 that meet at the trailing edge 58. The diverting strut 50 'is designed to divert the exhaust stream 60 with limited efficiency reduction when operating the gas turbine 10 within its design performance range. More specifically, the flow 60 impinges on the pre-curved surface 52 of the turning strut 50 'at the design point entrance pivot angle so that the flow 60 around the turning strut 50' is uniform. . Accordingly, laminar boundary layers 62 and 64 are formed on the surface of the turning strut 50 '. This is achieved with high reliability when operating the gas turbine engine 10 within its design performance range.

  However, sometimes it may be desirable to operate the gas turbine engine 10 below its design performance range. This will include operation during off-peak energy demand or other low energy demand conditions. During such operation, often referred to as “turn-down” operation, the flow rate of the exhaust around the turning strut 50 ′ is less than the optimal flow rate.

  Referring to FIG. 3, a turning strut 50 'during turndown operation is shown, in which case the flow 60 is turned at a turning angle that is largely deviated from the design point inlet turning angle (FIG. 2). Collides with the pre-curved surface 52 of 50 '. The flow 60 at this deflection swivel angle impinges on the pre-curved surface 52 of the turning strut 50 '. Stream 60 continues to flow along surface 54 to form laminar boundary layer 62. The flow 60 continues to flow along the surface 56 to form a laminar boundary layer 64 that separates downstream of the separation point 66. The laminar boundary layer 64 separates from the surface 56 when the momentum of the flow in the laminar boundary layer 64 decreases to a point where it becomes zero. As the laminar boundary layer 64 delaminates from the surface 56, the laminar boundary layer 64 causes a reverse flow on the surface 56. As the laminar boundary layer 64 separates, the laminar boundary layer 64 creates a wake 68 that causes an increase in pressure drag, which adversely affects the efficiency of the system. A plurality of vortex flows 70 are generated in the wake 68. As the vortices 70 begin to detach from the surface 56, they will detach at a constant frequency. The disengagement of the vortex 70 can cause vibration in the strut 50 ', which can add additional system inefficiencies such as increased noise and back pressure.

  Referring to FIGS. 4, 5 and 6, an embodiment of the turning strut represented by reference numeral 50 ″ is shown in schematic cross-sectional view (FIG. 4) as having a generally elongated teardrop shape. The turning strut 50 ″ has a curved leading edge 72 that leads to tapered surfaces 74 and 76 that meet at the trailing edge 78. A plurality of slots 80 extend through the diverting strut 50 "from an inlet 82 (Fig. 5) at the surface 74 to an outlet 84 (Fig. 6) at the surface 76. The slot 80 is in front of the diverting strut 50". Located close to the edge 72. The slot 80 is generally rectangular in shape with aligned and rounded ends. The area of the inlet 82 is larger than the area of the outlet 84. As a result, the volume of the slot 80 gradually decreases from the inlet 82 to the outlet 84. The schematic cross-sectional view of the slot 80 (FIG. 4) shows a generally complex curve that is generally serpentine. The diverting strut 50 "is designed to divert the exhaust flow 86 with limited efficiency reduction when operating the gas turbine engine 10 within its design performance range. The stream 86 impinges on the curved front (edge) surface 72 of the turning strut 50 "at the design point entrance pivot angle, so that the flow 86 around the turning strut 50" is uniform. Flow boundary layers 88 and 90 are formed on surfaces 74 and 76, respectively, of diverting strut 50 ". At the design point pivot angle, the pressure difference between the flow on the surface 74 and the flow on the surface 76 is negligible, so that any flow through the slot 80 is negligible.

  Referring now to FIG. 7, there is shown a turning strut 50 "during turndown operation, in which case the flow 86 is at a swivel angle greatly deviated from the design point inlet swivel angle (FIG. 4). Collides with the curved leading edge 72 of the turning strut 50 ". Stream 86 continues to flow along surface 74 to form laminar boundary layer 88. Stream 86 continues to flow along surface 76 to form laminar boundary layer 92. The deflection swivel angle creates a pressure difference between the flows at surfaces 74 and 76. A high pressure flow is formed on surface 74 and a low pressure flow is formed on surface 76. The pressure difference between the surfaces 74 and 76 creates a suction action in the slot 80 and creates a flow through the slot. The gradually decreasing volume of slot 80 increases the speed of flow through slot 80 according to Bernoulli's law. Bernoulli's law states that with respect to the correlation between fluid velocity and pressure, the pressure decreases when the fluid velocity increases and the pressure increases when the fluid velocity decreases. Therefore, the flow that flows into the slot 80 at the inlet 82 accelerates toward the outlet 84 through the slot 80. The flow exiting the slot 80 is faster than the flow at the upstream end of the surface 76. These flows merge at the outlet 84 so that the flow at the surface 76 downstream of the outlet 84 is accelerated. Unlike the prior art described above, this accelerated flow at surface 76 does not delaminate. This flow momentum does not drop to zero and the flow uniformity between the surfaces 74 and 76 is maintained. As described above, the slot 80 is serpentine to allow inflow into the inlet 82 and outflow from the outlet 84. More specifically, the direction of flow at surface 74 leads to inlet 82, and outlet 84 is along the direction of flow at surface 76. Accordingly, the pressure drag is reduced, thereby increasing the efficiency of the diffuser 42 and reducing the component stress.

  Although the present invention has been described in detail only with respect to a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Moreover, while various embodiments of the invention have been described, it is to be understood that aspects of the invention can include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is limited only by the scope of the claims.

10 Gas turbine engine 12 Outer turbine casing 14 Inlet 16 Compressor 18 Compressor blade 20 Shaft 22 Center line 24 Combustor 26 Inlet port 28 Fuel inlet 30 Multistage turbine 32 First stage 34 Turbine blade 36 Final stage 38 Turbine blade 40 Output shaft 42 diffuser 44 flow 46 flow 50 turning strut 50 'turning strut 50 "turning strut 52 front curved surface 54 tapered surface 56 tapered surface 58 trailing edge 60 flow 62 laminar boundary layer 64 laminar boundary layer 66 separation point 68 accompanied Flow 70 vortex 72 curved leading edge 74 taper surface 76 taper surface 78 trailing edge 80 slot 82 inlet 84 outlet 86 flow 88 laminar boundary layer 90 laminar boundary layer 92 laminar boundary layer

Claims (6)

A turning strut (50 ″) for use in a diffuser (42) of a turbine engine (10),
A curved leading edge (72);
A first tapered surface (74) depending from the curved leading edge (72) at one end thereof;
A second taper surface (76) depending at one end thereof from the curved leading edge (72) and facing the first taper surface (74);
A trailing edge (78) formed at the other end of the first and second tapered surfaces (74, 76);
Extends from the first taper surface (74) to the second taper surface (76) through the diverting strut (50 ") and from the first taper surface (74) to the second taper surface At least one slot (80) whose volume is reduced to (76) and disposed proximate to said curved leading edge (72);
A turning strut.   The turning strut of claim 1, wherein the at least one slot (80) comprises a plurality of aligned slots.   The turning strut of claim 1, wherein the at least one slot (80) has a generally rectangular shape with a rounded end.   The turning strut of claim 1, wherein the at least one slot (80) has a generally compound curved shape.   The turning strut of claim 4, wherein the generally compound curve shape comprises a serpentine shape.   The at least one slot (80) is disposed proximate to the curved leading edge (72) to provide a laminar boundary layer on the second tapered surface (76) during turndown operation of the turbine engine (10). The turning strut of claim 1, wherein (92) is maintained.

Images