An active control structure for weakening the horseshoe vortex on the leading edge of a turbine guide vane

Abstract

The present invention proposes an active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane. An annular gap structure is formed between the combustion chamber outlet solid wall and the turbine guide vane inlet end wall, and two air flows are injected into the mainstream channel through the annular gap structure. The mainstream gas and the two air flows meet at the trailing edge of the combustion chamber solid wall at the gap outlet to form an unsteady shedding vortex. By adjusting the momentum ratio of the two air flows to the mainstream, the intensity of the positive and negative vorticity of the shedding vortex can be changed. When the rotation direction of the main shedding vortex is opposite to the rotation direction of the downstream horseshoe vortex pressure surface branch and the same as the rotation direction of the horseshoe vortex suction surface branch, the main shedding vortex can weaken the horseshoe vortex pressure surface branch and strengthen the suction surface branch. By weakening the horseshoe vortex pressure surface branch, the intensity of the channel vortex evolved from it can be weakened; and the horseshoe vortex suction surface branch whose strength has grown can further weaken the channel vortex intensity because it is opposite to the channel vortex, thereby significantly reducing the intensity and loss of the secondary flow.

Description

Technical Field

[0001] The present invention relates to the field of turbines for turbomachinery such as ground-based gas turbines and aircraft engines. It relates to an active control structure for weakening the horseshoe vortex at the leading edge of turbine blades, and more particularly, to a structure for weakening and suppressing the horseshoe vortex at the leading edge of a low-viscosity, low-aspect-ratio high-pressure turbine guide vane passage. More specifically, the invention employs a novel active control structure to suppress secondary flow within the high-pressure turbine guide vane passage at the combustion chamber outlet, thereby reducing flow losses, improving the flow field uniformity at the turbine outlet, and enhancing turbine performance. Background Art

[0002] In modern ground-based gas turbines and aircraft engines, due to the increasing thermal and aerodynamic loads on turbines, low-viscosity, low-aspect-ratio turbine designs are becoming a trend, particularly for the first-stage high-pressure turbine guide vane located at the combustion chamber outlet. According to classical secondary flow theory for turbine blades, horseshoe vortices and channel vortices are the primary components of the blade's secondary flow vortex system and a significant source of secondary flow losses. The horseshoe vortex formed at the leading edge of the blade consists of a pressure branch located on the pressure side of the blade and a suction branch located on the suction side of the blade, with the two horseshoe vortex branches rotating in opposite directions. The pressure branch then develops downstream within the blade channel, gradually forming a channel vortex under the action of lateral pressure within the channel; the suction branch, on the other hand, surrounds the channel vortex and develops downstream together.

[0003] The leading edge radius of low-viscosity, low-aspect-ratio turbine blades is usually 3 to 5 times the leading edge radius of conventional turbine guide vane blades. Obviously, this will cause a significant increase in the leading edge horseshoe vortex. The enhanced horseshoe vortex structure will undoubtedly lead to a significant increase in the complexity of the vortex structure in the turbine guide vane channel, the unevenness of the flow field at the outlet, and the degree of total pressure loss, causing higher secondary flow losses and reducing turbine performance. Taking effective control measures to weaken the leading edge horseshoe vortex has important engineering value for improving turbine performance. Regarding the control measures for the leading edge horseshoe vortex structure, the existing public technology is mainly the leading edge shaping technology. Such as Figure 1 As shown in the figure, by changing the radius of the leading edge of the blade root, the local flow state is changed and the horseshoe vortex structure is weakened. However, this type of structure weakens the two side branches of the horseshoe vortex, but at the same time it also leads to larger wall corner vortices, which still causes flow losses and affects turbine performance. Summary of the Invention

[0004] (1) Technical issues

[0005] In view of the above-mentioned defects and deficiencies of the prior art, in order to weaken the secondary flow such as the leading edge horseshoe vortex in the blade channel of the low-viscosity, low-aspect-ratio high-pressure turbine guide vane, the present invention proposes an active control structure for weakening the leading edge horseshoe vortex of the turbine guide vane. The turbine guide vane is a low-viscosity, low-aspect-ratio high-pressure turbine guide vane. With the help of the inherent step structure between the combustion chamber outlet solid wall and the turbine guide vane inlet end wall, a narrow annular gap structure is constructed. Two air flows are injected into the mainstream channel through the annular gap structure. The two air flows and the mainstream gas meet at the trailing edge of the combustion chamber solid wall at the gap outlet to form an unsteady The shedding vortex can change the intensity of the positive and negative vorticity of the shedding vortex by adjusting the momentum ratio of the two airflows to the mainstream. When the rotation direction of the main shedding vortex is opposite to the rotation direction of the downstream horseshoe vortex pressure surface branch, and the same as the rotation direction of the horseshoe vortex suction surface branch, the main shedding vortex can weaken the horseshoe vortex pressure surface branch and promote the growth of the horseshoe vortex suction surface branch. By weakening the horseshoe vortex pressure surface branch, the intensity of the channel vortex evolved from it can be weakened; and the horseshoe vortex suction surface branch, whose strength has grown, can further weaken the channel vortex intensity because it is opposite to the channel vortex, thereby significantly reducing the intensity and loss of the secondary flow.

[0006] (2) Technical solution

[0007] In order to achieve the purpose of the present invention, the technical solutions adopted by the present invention are as follows:

[0008] An active control structure for weakening the horseshoe vortex at the leading edge of a turbine guide vane, wherein the turbine guide vane is a low-viscosity, low-aspect-ratio high-pressure turbine guide vane, wherein the space between each turbine guide vane in the turbine guide vane is formed as a turbine guide vane channel, wherein the control structure comprises a combustion chamber outlet solid wall and a turbine guide vane inlet end wall arranged downstream of the combustion chamber outlet solid wall and coaxially, wherein the turbine guide vane inlet end wall is sleeved outside the combustion chamber outlet solid wall to form a step structure, and wherein the control structure comprises:

[0009] A radial gap is formed between the turbine guide vane inlet end wall and the combustion chamber outlet solid wall, so that a narrow annular gap is formed therebetween. The annular gap is used to inject two airflows with adjustable momentum ratio into the mainstream gas channel. The two airflows meet the mainstream gas at the trailing edge of the combustion chamber outlet solid wall at the annular gap outlet position to form an unsteady vortex shedding. The unsteady vortex shedding includes a positive vortex branch and a negative vortex branch with opposite rotation directions and appearing alternately.

[0010] The momentum of the two airflows is adjustable. By adjusting the momentum ratio of the two airflows to the mainstream gas, the strength of the positive vorticity branch and the negative vorticity branch in the unsteady shedding vortex can be changed, and the branch with greater strength among the positive vorticity branches and the negative vorticity branches forms a primary shedding vortex, and the branch with less strength forms a secondary shedding vortex.

[0011] When the momentum of the two airflows is adjusted so that the rotation direction of the main shedding vortex is opposite to the rotation direction of the pressure surface branch of the horseshoe vortex at the leading edge of the downstream turbine guide vane but the same as the rotation direction of the suction surface branch of the horseshoe vortex, the pressure surface branch of the horseshoe vortex can be weakened and the suction surface branch of the horseshoe vortex can be strengthened. Then, by weakening the pressure surface branch of the horseshoe vortex, the intensity of the channel vortex evolved from it can be suppressed, and by strengthening the suction surface branch of the horseshoe vortex, the intensity of the channel vortex can be further weakened.

[0012] Preferably, the step height H+h formed between the combustion chamber outlet solid wall and the turbine guide vane inlet end wall is 2.5-5.5 mm, where H is the radial height of the annular gap and h is the wall thickness of the combustion chamber outlet solid wall. The annular gap height H is a key control variable for controlling the momentum of the two airflows. If H is too large, a larger amount of the two airflows may be required to achieve the desired momentum, potentially resulting in additional aerodynamic mixing losses.

[0013] Preferably, the combustion chamber is fabricated from sheet metal, with a wall thickness h of 0.5 to 1.5 mm. If the wall thickness is too small, the boundary layers on both sides of the combustion chamber wall will directly intermingle, preventing the formation of an effective shedding vortex structure. If the wall thickness is too large, the boundary layers on both sides of the combustion chamber wall will form a separation vortex at the trailing edge of the wall, preventing the formation of an effective shedding vortex.

[0014] Preferably, the axial distance S between the trailing edge of the combustion chamber outlet solid wall and the leading edge of the downstream turbine guide vane is 2 to 10 mm. If this axial distance S is too large, the shedding vortex will be rapidly mixed and dissipated, not only failing to suppress the horseshoe vortex but also consuming additional mainstream energy. If the distance is too small, the potential flow effect of the guide vane leading edge will change the pressure distribution in the trailing edge area of the combustion chamber outlet solid wall, and even affect the formation of the shedding vortex.

[0015] In the active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention, two air flows are ejected into the mainstream channel through the annular gap between the solid wall at the combustion chamber outlet and the turbine guide vane inlet end wall. The two air flows axially in the annular slit and form a boundary layer near the wall. At the outlet of the annular gap, due to the difference in momentum between the boundary layer of the two air flows and the boundary layer of the mainstream, an unsteady shedding vortex is formed at the trailing edge of the solid wall at the combustion chamber outlet. The unsteady shedding vortex consists of a positive vortex branch and a negative vortex branch, and the positive and negative vortex branches have opposite rotation directions and appear alternately.

[0016] Preferably, the aspect ratio L / H of the annular gap is 4 to 8, wherein L is the axial height of the annular gap and H is the radial height of the annular gap, so as to ensure that a sufficient boundary layer can be developed in the annular gap while avoiding flow separation of the two airflows at the inlet of the annular gap.

[0017] In the active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention, the strength contrast of the positive and negative vortex branches in the shedding vortex can be changed by adjusting the momentum ratio of the two airflows to the mainstream combustion gas. When the rotation direction of the main shedding vortex (the branch with greater strength among the positive and negative vortex branches) is ensured to be opposite to the rotation direction of the downstream horseshoe vortex pressure surface branch, and the same as the rotation direction of the horseshoe vortex suction surface branch, the main shedding vortex can weaken the horseshoe vortex pressure surface branch and promote the growth of the horseshoe vortex suction surface branch; while the secondary shedding vortex has almost no effect on the mainstream. By weakening the horseshoe vortex pressure surface branch, the intensity of the channel vortex evolved from it can be weakened; and the horseshoe vortex suction surface branch, whose intensity is grown, can further weaken the channel vortex intensity because it is opposite to the channel vortex, thereby significantly reducing the intensity and loss of the secondary flow.

[0018] Preferably, the momentum ratio of the two airflows to the mainstream gas is 3 to 15, so as to ensure smooth generation of shedding vortices while reducing disturbance to the mainstream and lowering mixing losses.

[0019] (3) Technical effects

[0020] Compared with the prior art, the active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention can achieve at least the following effects:

[0021] (1) Simple structure. The active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention does not increase the complexity of the structure. It mainly relies on existing components and can be simply modified in existing gas turbines or applied to newly designed gas turbines.

[0022] (2) Low manufacturing cost. Compared with other structures such as non-axisymmetric end walls and leading edge modification for controlling secondary flow, the active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention does not have any processing difficulties and is easy to implement;

[0023] (3) Significant effect. In the active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention, since the solid wall at the combustion chamber outlet is annular, the induced shedding vortex will also be consistent with the solid wall at the combustion chamber outlet, forming an annular vortex structure; and the horseshoe vortex at the leading edge of the blade is parallel to the annular wall of the flow channel. The shedding vortex is in the same direction as the horseshoe vortex, so it can act on the horseshoe vortex over a larger contact surface, which can more effectively weaken the secondary flow.

[0024] (4) Wide operating range. The active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention achieves active regulation of the horseshoe vortex by guiding the positive-negative vortex contrast of the shedding vortex. This can effectively suppress the secondary flow structure, reduce secondary flow losses, and improve turbine performance under any engine operating conditions.

[0025] (5) The active control structure of the present invention for weakening the horseshoe vortex at the leading edge of the turbine guide vane does not affect each other with the existing technical strategies and can be used in a superimposed manner to further improve the secondary flow suppression effect and reduce secondary flow losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the existing turbine guide vane leading edge modification structure.

[0027] Figure 2 This is a schematic diagram of the step structure between the existing combustion chamber outlet solid wall and the turbine guide vane inlet end wall.

[0028] Figure 3 Schematic diagram of the active control structure for weakening the horseshoe vortex at the leading edge of the turbine guide vane of the present invention.

[0029] In the figure,

[0030] Combustion chamber 10 , combustion chamber outlet solid wall 11 , turbine guide vane 20 , turbine guide vane inlet end wall 21 , turbine guide vane blade 22 , and step structure 30 . DETAILED DESCRIPTION

[0031] In order to better understand the present invention, the content of the present invention will be further illustrated below in conjunction with the embodiments so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the following are only preferred embodiments of the present invention, but the content of the present invention is not limited to the following embodiments. In fact, various modifications and variations can be made in the present invention without departing from the scope or spirit of the present invention, which will be apparent to those skilled in the art. For example, the features shown or described as part of one embodiment can be used together with another embodiment to produce another embodiment. Therefore, it is intended that the present invention include such modifications and variations within the scope of the appended claims and their equivalents.

[0032] Due to the difference in thermal expansion between various components during engine operation, in order to avoid thermal stress concentration, an inherent step structure 30 exists between the outlet solid wall 11 of the combustion chamber 10 and the inlet end wall 21 of the turbine guide vane 20. Figure 2 shown.

[0033] like Figure 3As shown, the present invention is to weaken the secondary flow such as the leading edge horseshoe vortex in the low-viscosity, low-aspect-ratio high-pressure turbine guide vane channel, and proposes an active control structure for weakening the leading edge horseshoe vortex of the turbine guide vane. The turbine guide vane 20 is a low-viscosity, low-aspect-ratio high-pressure turbine guide vane. The space between each turbine guide vane 21 in the turbine guide vane 20 forms a turbine guide vane channel. The control structure includes a combustion chamber outlet solid wall 11 and a turbine guide vane inlet end wall 21 arranged downstream of the combustion chamber outlet solid wall 11 and coaxially arranged. The turbine guide vane inlet end wall 21 is sleeved on the outside of the combustion chamber outlet solid wall 11 to form a step structure. With the help of the step structure between the combustion chamber outlet solid wall 11 and the turbine guide vane inlet end wall 21, a narrow annular gap is constructed. The annular gap is used to inject two airflows with adjustable momentum ratio into the mainstream gas channel. The two airflows and the mainstream gas are at the annular gap outlet position. After the two airflows meet at the trailing edge of the combustion chamber outlet solid wall 11, an unsteady shedding vortex is formed, and the unsteady shedding vortex includes a positive vortex branch and a negative vortex branch with opposite rotation directions and appearing alternately; the momentum of the two airflows is adjustable, and the strength of the positive vortex branch and the negative vortex branch in the unsteady shedding vortex can be changed by adjusting the momentum ratio of the two airflows to the mainstream gas, and the branch with larger strength among the positive vortex branches and the negative vortex branches forms the main shedding vortex, and the branch with smaller strength forms the secondary shedding vortex; when the momentum of the two airflows is adjusted so that the rotation direction of the main shedding vortex is opposite to the rotation direction of the pressure surface branch of the horseshoe vortex at the leading edge of the downstream turbine guide vane and the same as the rotation direction of the suction surface branch of the horseshoe vortex, the pressure surface branch of the horseshoe vortex can be weakened and the suction surface branch of the horseshoe vortex can be strengthened, and then the intensity of the channel vortex evolved from it can be suppressed by weakening the pressure surface branch of the horseshoe vortex, and the intensity of the channel vortex can be further weakened by strengthening the suction surface branch of the horseshoe vortex.

[0034] In a preferred embodiment of the present invention, the step height H+h formed between the combustion chamber outlet solid wall 11 and the turbine guide vane inlet end wall 21 is 2.5~5.5mm, wherein H is the radial height of the annular gap, and h is the wall thickness of the combustion chamber outlet solid wall 11, which is 0.5~1.5mm. The annular gap height H is an important control variable for controlling the momentum of the two airflows. If H is too large, a larger amount of two airflow flow may be required to achieve the required momentum of the two airflows, which may cause additional aerodynamic mixing losses; for the wall thickness h of the combustion chamber outlet solid wall, if its thickness h is too small, the boundary layers on both sides of the combustion chamber solid wall will be directly mixed and cannot form an effective shedding vortex structure; if its thickness h is too large, the boundary layers on both sides of the combustion chamber solid wall will form separation vortices at the trailing edge of the solid wall, and cannot form an effective shedding vortex. The axial distance S between the trailing edge of the combustion chamber outlet solid wall 11 and the leading edge of the downstream turbine guide vane 22 is 2 to 10 mm. If this distance S is too large, the shedding vortex will be rapidly mixed and dissipated, not only failing to suppress the horseshoe vortex but also consuming additional mainstream energy. If the distance S is too small, the potential flow effect of the guide vane leading edge will change the pressure distribution in the trailing edge area of the combustion chamber outlet solid wall, and even affect the formation of the shedding vortex. The aspect ratio L / H of the annular gap is 4 to 8, where L is the axial height of the annular gap and H is the radial height of the annular gap. This ensures that a sufficient boundary layer can develop in the annular gap while preventing the two airflows from separating at the annular gap entrance.

[0035] In the present invention's active control structure for weakening the horseshoe vortex at the leading edge of a turbine guide vane, the strength of the positive and negative vorticity branches in the shedding vortex can be varied by adjusting the momentum ratio of the two airflows to the mainstream gas flow, with the momentum ratio between the two airflows and the mainstream gas flow ranging from 3 to 15. By ensuring that the rotation direction of the primary shedding vortex (the stronger of the positive and negative vorticity branches) is opposite to that of the downstream horseshoe vortex pressure branch but the same as that of the horseshoe vortex suction branch, the primary shedding vortex can weaken the horseshoe vortex pressure branch while promoting the growth of the horseshoe vortex suction branch; while the secondary shedding vortex has little impact on the mainstream flow. By weakening the horseshoe vortex pressure branch, the strength of the channel vortex that evolves from it can be weakened. The horseshoe vortex suction branch, which has grown in strength, further weakens the channel vortex strength due to its opposite rotation direction to the channel vortex, thereby significantly reducing the strength and losses of the secondary flow. Through the above-described embodiments, the objectives of the present invention are fully and effectively achieved. All equivalent or simple variations based on the structure, features, and principles described in the patent concept are included within the scope of protection of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0036] Some parts of the present invention are well known to those skilled in the art and are not described in detail.

Claims

1. An active control structure for weakening the horseshoe vortex at the leading edge of a turbine guide vane, wherein the turbine guide vane is a low-viscosity, low-aspect-ratio high-pressure turbine guide vane, wherein the space between each turbine guide vane in the turbine guide vane forms a turbine guide vane vane channel, wherein the control structure comprises a combustion chamber outlet solid wall and a turbine guide vane inlet end wall disposed downstream of the combustion chamber outlet solid wall and coaxially arranged, wherein the turbine guide vane inlet end wall is sleeved outside the combustion chamber outlet solid wall to form a stepped structure, characterized in that: A radial gap is formed between the turbine guide vane inlet end wall and the combustion chamber outlet solid wall, so that a narrow annular gap is formed therebetween. The annular gap is used to inject two airflows with adjustable momentum ratio into the mainstream gas channel. The two airflows meet the mainstream gas at the trailing edge of the combustion chamber outlet solid wall at the annular gap outlet position to form an unsteady vortex shedding. The unsteady vortex shedding includes a positive vortex branch and a negative vortex branch with opposite rotation directions and appearing alternately. The momentum of the two airflows is adjustable, and the strength of the positive vorticity branch and the negative vorticity branch in the unsteady shedding vortex is changed by adjusting the momentum ratio of the two airflows to the mainstream gas, and the branch with greater strength among the positive vorticity branches and the negative vorticity branches forms a primary shedding vortex, and the branch with less strength forms a secondary shedding vortex; The momentum of the two airflows is adjusted such that the momentum ratio of the two airflows to the mainstream combustion gas is 3 to 15, so that the rotation direction of the main shedding vortex is opposite to the rotation direction of the pressure side branch of the horseshoe vortex at the leading edge of the downstream turbine guide vane, but is the same as the rotation direction of the suction side branch of the horseshoe vortex, thereby weakening the pressure side branch of the horseshoe vortex and strengthening the suction side branch of the horseshoe vortex. Subsequently, by weakening the pressure side branch of the horseshoe vortex, the intensity of the channel vortex evolved therefrom is suppressed, and by strengthening the suction side branch of the horseshoe vortex, the intensity of the channel vortex is further weakened. And wherein, the aspect ratio L / H of the annular gap is 4 to 8, wherein L is the axial height of the annular gap, and H is the radial height of the annular gap.

2. The active control structure for weakening the horseshoe vortex at the leading edge of a turbine guide vane according to claim 1, characterized in that: The step height H+h formed between the combustion chamber outlet solid wall and the turbine guide vane inlet end wall is 2.5 to 5.5 mm, wherein H is the radial height of the annular gap, and h is the wall thickness of the combustion chamber outlet solid wall, and the wall thickness h of the combustion chamber outlet solid wall is 0.5 to 1.5 mm.

3. The active control structure for weakening the horseshoe vortex at the leading edge of a turbine guide vane according to claim 1, characterized in that: The axial distance S between the trailing edge of the combustion chamber outlet solid wall and the leading edge of the downstream turbine guide vane is 2 to 10 mm.

Images