An active control structure for weakening secondary flow in a turbine guide vane passage

Abstract

This invention provides an active control structure to weaken the secondary flow within the turbine guide vane passage. By arranging multiple discrete slit structures discontinuously distributed circumferentially on the upstream side of the turbine guide vane passage, and setting discrete ribs between the discrete slits, these structures, together with the combustion chamber solid wall, form a discrete step structure. This creates two incoming airflows with pre-swirl and uneven circumferential pressure distribution near the turbine guide vane inlet endwall, thereby offsetting or reducing the leading-edge potential flow effect and suppressing the generation of horseshoe vortices. Furthermore, it adjusts the lateral pressure gradient within the turbine guide vane passage to offset or weaken the crossflow effect, suppressing the migration and evolution of channel vortices within the vane passage. Ultimately, this achieves the goals of reducing flow losses, improving the flow field uniformity at the turbine outlet, and enhancing turbine performance.

Description

Technical Field

[0001] This invention belongs to the field of turbines in turbomachinery such as ground gas turbines and aero engines. It relates to an active control structure that weakens the secondary flow in the turbine guide vane passage. More specifically, it adopts a new active control structure to suppress the secondary flow in the high-pressure turbine guide vane passage at the combustion chamber outlet, reduce flow losses, improve the flow field uniformity at the turbine outlet, and improve turbine performance. Background Technology

[0002] In modern ground-based gas turbines and aero-engines, the increasing aerodynamic loads on turbines and the growing complexity of their internal vortex structures lead to more severe flow losses and non-uniformity in the outlet flow field, significantly reducing turbine performance. Secondary flow is a major contributing factor. Therefore, effective flow control techniques must be adopted to weaken secondary flow and reduce aerodynamic losses. According to classical turbine secondary flow theory, the incoming boundary layer impacts the leading edge of the blade, forming horseshoe vortices under the influence of potential flow effects and radial pressure gradients. These horseshoe vortices then propagate downstream, forming channel vortex structures under the influence of transverse pressure gradients within the channel. To weaken the secondary flow within the turbine guide vane channel, counteract or reduce transverse flow effects, and suppress the formation of horseshoe vortices, new methods and effective measures need to be proposed from a theoretical perspective. Summary of the Invention

[0003] (I) Technical Issues

[0004] To address the aforementioned deficiencies and shortcomings of existing technologies, this invention provides an active control structure for weakening secondary flow within the turbine guide vane passage. By arranging a novel structure upstream of the turbine guide vane passage, two airflows with pre-swirling properties and uneven circumferential pressure distribution are created near the turbine guide vane inlet endwall. This counteracts or reduces the leading-edge potential flow effect, thereby suppressing the generation of horseshoe vortices. Furthermore, the transverse pressure gradient within the turbine guide vane passage is adjusted to counteract or weaken the crossflow effect, suppressing the migration and evolution of channel vortices within the vane passage. Ultimately, this achieves the goals of reducing flow losses, improving the flow field uniformity at the turbine outlet, and enhancing turbine performance.

[0005] (II) Technical Solution

[0006] To suppress secondary flow within the turbine blade passages, the technical solution adopted in this invention is as follows:

[0007] An active control structure for weakening secondary flow within a turbine guide vane passage includes a combustion chamber outlet solid wall and a turbine guide vane inlet end wall disposed downstream of the combustion chamber outlet solid wall. Turbine guide vanes are evenly distributed circumferentially along the downstream side of the turbine guide vane inlet end wall, and the space between adjacent turbine guide vanes forms a turbine guide vane passage. The structure is characterized in that…

[0008] When the active control structure is located on the high-radius casing side, the radius of the turbine guide vane inlet end wall is larger than the radius of the combustion chamber outlet solid wall, and the upstream side of the turbine guide vane inlet end wall is concentrically fitted outside the downstream side of the combustion chamber outlet solid wall; when the active control structure is located on the low-radius hub side, the radius of the turbine guide vane inlet end wall is smaller than the radius of the combustion chamber outlet solid wall, and the upstream side of the turbine guide vane inlet end wall is concentrically fitted inside the downstream side of the combustion chamber outlet solid wall. The two overlap and fit together axially and form an annular channel circumferentially.

[0009] The annular channel is provided with a plurality of strip-shaped discrete ribs evenly arranged along the circumference, and each strip-shaped discrete rib is arranged in an inclined manner that is not parallel to the axial direction within the annular channel. The space between each strip-shaped discrete rib forms a plurality of discrete slots that are discontinuously distributed along the circumference. The space between each strip-shaped discrete rib and the solid wall of the combustion chamber outlet forms a plurality of discrete steps that are discontinuously distributed along the circumference. Each discrete step corresponds one-to-one with a turbine guide vane passage in the circumference direction. Each discrete slot is used to inject two streams of air into the main gas passage.

[0010] In the active control structure for weakening secondary flow within the turbine guide vane passage of the present invention, a discrete slot structure with discontinuous circumferential distribution is provided upstream of the turbine guide vane. Discrete ribs are provided between the discrete slots, forming a discrete step structure together with the combustion chamber solid wall. By utilizing the discrete step structure formed between the discrete slots, a local high static pressure zone is created downstream of each discrete step, which can adjust the pressure distribution in the leading edge inlet region of the turbine guide vane and counteract the influence of the static pressure potential flow effect at the leading edge of the vane.

[0011] Preferably, each of the discrete steps is located in the middle of the turbine guide vane passage between the blades in the circumferential direction.

[0012] Preferably, the discrete slits are located axially upstream of the leading edge of the turbine guide vane, and each discrete slit has a lateral angle θ with the circumferential direction, such that its outlet direction is toward the pressure surface side of the turbine guide vane. The discrete slits introduce two high-momentum airflows into the main gas flow channel to weaken or offset the lateral pressure gradient in the turbine guide vane channel and reduce the influence of the crossflow effect on the low-energy fluid near the end wall of the channel.

[0013] Furthermore, the lateral angle θ has a numerical range of 20° to 85°. By adjusting the lateral angle θ, the components of the tangential momentum and axial momentum of the two airflows can be adjusted. The tangential momentum is used to counteract the crossflow effect within the turbine guide vane passage, while the axial momentum can improve the boundary layer's resistance to separation within the turbine guide vane passage.

[0014] Furthermore, the lateral angle θ is selected comprehensively based on the flow rates of the two airflows. This is because when the flow rates of the two airflows are too large, an excessively large lateral angle may cause flow separation on the suction surface of the blade's leading edge. Therefore, the lateral angle θ should be selected comprehensively in conjunction with the flow rates of the two airflows to prevent flow separation on the blade's suction surface.

[0015] Preferably, the width W of the discrete slit is adjustable. By changing the width W of the discrete slit, the circumferential range of action of the discrete slit can be adjusted. Under the same two-stream airflow, the smaller the slit width W, the greater the momentum of the two-stream airflow, and the larger the corresponding axial range of action; however, if W is too small, when the discrete slit jet cannot cover the leading edge region of the blade, the control over the secondary flow will be lost.

[0016] Furthermore, the width W of the discrete slot is not less than the leading edge diameter of the turbine guide vane located downstream of it.

[0017] Preferably, the axial distance S between the discrete slot and the leading edge of the turbine guide vane is adjustable. The strength of the coherent interaction between the low-energy fluid in the boundary layer of the turbine guide vane channel and the potential flow region at the leading edge of the vane can be adjusted by the axial distance S.

[0018] In the active control structure for weakening secondary flow in the turbine guide vane passage of the present invention, the effect on the mainstream flow field is improved by adjusting the position of the discrete slot in the flow field: by changing the relative axial distance S between the discrete slot and the leading edge of the blade cascade, the strength of the coherent interaction between the low-energy fluid in the boundary layer and the potential flow region at the leading edge of the blade cascade can be adjusted; by changing the relative circumferential position of the discrete slot relative to the blade cascade, the range of influence of the two airflows on the flow fields of the pressure surface and suction surface of the blade can be adjusted.

[0019] (III) Technical Effects

[0020] Compared to traditional secondary flow suppression measures, the active control structure for weakening secondary flow within the turbine guide vane passage of the present invention has the following advantages:

[0021] (1) Unlike the passive non-axisymmetric endwall technology, the discrete slot structure in the active control structure for weakening the secondary flow in the turbine guide vane channel of the present invention is an active control strategy that can achieve ideal control effect under any conditions.

[0022] (2) The structure is simple. The active control structure for weakening the secondary flow in the turbine guide vane channel of the present invention can be applied to existing or future engine designs, and has great application potential. Attached Figure Description

[0023] Figure 1 This is a radial cross-sectional view of the active control structure for weakening secondary flow in the turbine guide vane passage of the present invention.

[0024] Figure 2 This is the right view along direction B (axial direction) of the present invention.

[0025] Figure 3 This is a top view of the present invention along direction A (circumferential direction).

[0026] In the picture:

[0027] Combustion chamber outlet solid wall 11, turbine guide vane inlet end wall 21, turbine guide vane blade 22, strip-shaped discrete ribs 31, discrete slots 32. Detailed Implementation

[0028] To better understand the present invention, the following embodiments further illustrate the content of the invention, so that the advantages and features of the invention can be more easily understood by those skilled in the art. It should be noted that the following descriptions are merely preferred embodiments of the present invention, but the content of the invention is not limited to the following embodiments. In fact, various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention, which will be apparent to those skilled in the art. For example, features shown or described as part of one embodiment can be used with another embodiment to produce yet another embodiment. Therefore, it is intended that such modifications and variations be included within the scope of the appended claims and their equivalents.

[0029] like Figure 1-3 As shown, the active control structure for weakening the secondary flow in the turbine guide vane 22 channel of the present invention includes a combustion chamber outlet solid wall 11 and a turbine guide vane inlet end wall 21 disposed downstream of the combustion chamber outlet solid wall 11. Turbine guide vanes 22 are evenly distributed circumferentially on the downstream side of the turbine guide vane inlet end wall 21, and the space between two adjacent turbine guide vanes 22 is formed as a turbine guide vane 22 channel.

[0030] When the active control structure is located on the high-radius casing side, the radius of the turbine guide vane inlet end wall 21 is larger than the radius of the combustion chamber outlet solid wall 11, and the upstream side of the turbine guide vane inlet end wall 21 is concentrically fitted outside the downstream side of the combustion chamber outlet solid wall 11. When the active control structure is located on the low-radius hub side, the radius of the turbine guide vane inlet end wall 21 is smaller than the radius of the combustion chamber outlet solid wall 11, and the upstream side of the turbine guide vane inlet end wall 21 is concentrically fitted inside the downstream side of the combustion chamber outlet solid wall 11. The two overlap and fit together axially and form a circumferential structure. An annular channel is provided; multiple strip-shaped discrete ribs 31 are uniformly arranged in the circumferential direction within the annular channel, and each strip-shaped discrete rib 31 is arranged in an inclined manner that is not parallel to the axial direction within the annular channel. The space between each strip-shaped discrete rib 31 forms multiple discrete slots 32 that are discontinuously distributed in the circumferential direction. Each strip-shaped discrete rib 31 and the combustion chamber outlet solid wall 11 form multiple discrete steps that are discontinuously distributed in the circumferential direction. Each discrete step corresponds one-to-one with the turbine guide vane 22 channel in the circumferential direction. Each discrete slot 32 is used to inject two streams of air into the mainstream gas passage.

[0031] In the active control structure for weakening secondary flow within the turbine guide vane passage of the present invention, a discrete slot structure with discontinuous circumferential distribution is provided upstream of the turbine guide vane. Discrete ribs 31 are provided between the discrete slots 32, forming a discrete step structure together with the combustion chamber solid wall. By utilizing the discrete step structure formed between the discrete slots 32, a local high static pressure zone is formed downstream of each discrete step, which can adjust the pressure distribution in the leading edge inlet region of the turbine guide vane and counteract the influence of the static pressure potential flow effect at the leading edge of the vane.

[0032] In a preferred embodiment of the invention, each discrete step is located circumferentially in the middle of the turbine guide vane passage between the blades. The discrete slits 32 are located axially upstream of the leading edge of the turbine guide vane, and each discrete slit 32 has a lateral angle θ with the circumferential direction, such that its outlet direction faces the pressure surface side of the turbine guide vane. High-momentum dual airflows are introduced into the main gas flow passage through each discrete slit 32 to weaken or offset the lateral pressure gradient within the turbine guide vane passage, reducing the influence of crossflow effects on the low-energy fluid near the endwall of the passage. Furthermore, the lateral angle θ ranges from 20° to 85°. The lateral angle θ adjusts the components of the tangential and axial momentum of the dual airflows. The tangential momentum counteracts the crossflow effect within the turbine guide vane passage, while the axial momentum improves the boundary layer's resistance to separation within the passage. Furthermore, the lateral angle θ is selected based on a comprehensive consideration of the flow rates of the dual airflows. The reason is that when the flow rates of the two air streams are too large, an excessively large lateral angle may cause flow separation on the suction surface of the blade leading edge. Therefore, the lateral angle θ should be selected in conjunction with the flow rates of the two air streams to prevent flow separation on the suction surface of the blade.

[0033] In a preferred embodiment of the present invention, the width W of the discrete slit 32 is adjustable. By changing the width W of the discrete slit 32, the circumferential range of action of the discrete slit 32 can be adjusted. Under the same two-stream airflow, the smaller the slit width W, the greater the momentum of the two-stream airflow, and the larger the corresponding axial range of action; however, if W is too small, when the jet from the discrete slit 32 cannot cover the leading edge region of the blade, it will lose control over the secondary flow. Furthermore, the width W of the discrete slit 32 is not less than the leading edge diameter of the turbine guide vane located downstream of it. The axial distance S between the discrete slit 32 and the leading edge of the turbine guide vane is adjustable. By adjusting the axial distance S, the strength of the coherent interaction between the low-energy fluid in the boundary layer of the turbine guide vane channel and the potential flow region at the leading edge of the blade can be adjusted.

[0034] In the active control structure for weakening secondary flow in the turbine guide vane passage of the present invention, the effect on the mainstream flow field is improved by adjusting the position of the discrete slot 32 in the flow field: by changing the relative axial distance S between the discrete slot 32 and the leading edge of the blade cascade, the strength of the coherent interaction between the low-energy fluid in the boundary layer and the potential flow region at the leading edge of the blade cascade can be adjusted; by changing the relative circumferential position of the discrete slot 32 relative to the blade cascade, the range of influence of the two airflows on the flow fields of the pressure surface and suction surface of the blade can be adjusted.

[0035] The objectives of this invention have been fully and effectively achieved through the above embodiments. All equivalent or simple variations made to the structures, features, and principles described in this patent concept are included within the protection scope of this patent. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the structure of this invention or exceed the scope defined in these claims, all of which should fall within the protection scope of this invention.

[0036] The parts of this invention not described in detail are well-known to those skilled in the art.

Claims

1. An active control structure for weakening secondary flow within a turbine guide vane passage, comprising a combustion chamber outlet solid wall and a turbine guide vane inlet end wall disposed downstream of the combustion chamber outlet solid wall, wherein turbine guide vanes are evenly distributed circumferentially on the downstream side of the turbine guide vane inlet end wall, and the space between two adjacent turbine guide vanes forms a turbine guide vane passage, characterized in that, When the active control structure is located on the high-radius casing side, the radius of the turbine guide inlet end wall is greater than the radius of the combustion chamber outlet solid wall, and the upstream side of the turbine guide inlet end wall is concentrically sleeved outside the downstream side of the combustion chamber outlet solid wall. When the active control structure is located on the low-radius hub side, the radius of the turbine guide inlet end wall is smaller than the radius of the combustion chamber outlet solid wall, and the upstream side of the turbine guide inlet end wall is concentrically fitted inside the downstream side of the combustion chamber outlet solid wall. The turbine guide vane inlet end wall and the combustion chamber outlet solid wall overlap and fit together in the axial direction and form an annular channel in the circumferential direction. The annular channel is provided with a plurality of strip-shaped discrete ribs evenly arranged along the circumference, and each of the strip-shaped discrete ribs is arranged in an inclined manner that is not parallel to the axial direction in the annular channel. The space between each strip-shaped discrete rib is formed as a plurality of discrete slots that are discontinuously distributed along the circumference. The space between each strip-shaped discrete rib and the solid wall of the combustion chamber outlet is formed as a plurality of discrete steps that are discontinuously distributed along the circumference. Each discrete step corresponds one-to-one with a turbine guide vane passage in the circumference direction. Each discrete slot is used to inject two streams of air into the main gas passage. Furthermore, the discrete slits are located upstream of the leading edge of the turbine guide vane in the axial direction, and each discrete slit has a lateral angle θ with the circumferential direction, so that its outlet direction is toward the pressure surface side of the turbine guide vane. The discrete slits introduce two high-momentum airflows into the mainstream gas passage to weaken or offset the lateral pressure gradient in the turbine guide vane passage and reduce the influence of the crossflow effect on the low-energy fluid near the end wall of the passage. The width W of the discrete slit is not less than the leading edge diameter of the turbine guide vane downstream of it, and the width of the discrete slit is adjustable. By changing the width of the discrete slit, its circumferential range of action can be adjusted. Furthermore, under the same two airflow flow rates, the smaller the slit width, the greater the flow rate of the two airflows, and the larger the corresponding axial range of action. If the discrete slit is too small, its jet cannot cover the leading edge area of ​​the blade, and it will lose control over the secondary flow.

2. The active control structure for weakening secondary flow in the turbine guide vane passage according to claim 1, characterized in that, Each of the discrete steps is located in the middle of the turbine guide vane passage between the blades in the circumferential direction.

3. The active control structure for weakening secondary flow in the turbine guide vane passage according to claim 1, characterized in that, The lateral included angle θ has a numerical range of 20° to 85°.

4. The active control structure for weakening secondary flow in the turbine guide vane passage according to claim 3, characterized in that, The lateral angle θ is selected based on the combined flow rates of the two airflows.

5. The active control structure for weakening secondary flow in the turbine guide vane passage according to claim 1, characterized in that, The axial distance S between the discrete slot and the leading edge of the turbine guide vane is adjustable. The strength of the coherent interaction between the low-energy fluid in the boundary layer of the turbine guide vane channel and the potential flow region at the leading edge of the vane can be adjusted by the axial distance S.

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