Resistance and noise reduction blade grid based on blade tip and winglet fusion

Abstract

The invention belongs to the technical field of aviation turbine design, and particularly relates to a resistance and noise reduction cascade based on blade tip winglet fusion. The resistance and noise reduction cascade comprises blades and a specific blade tip and winglet fusion scheme, and the blades are characterized in that winglets are added to blade tips, and blade tip and winglet fusion modification is carried out. According to blade tip winglet fusion, a winglet is added to a blade tip, and the blade tip and the winglet are connected through a smooth curve within the thickness scale of a boundary layer between the surface of the blade tip and the surface of the winglet. According to the method, blade tip winglet fusion shaping is carried out on the blade tip of the plane blade grid, the width-to-height ratio of a gap channel can be increased, then circulation resistance is increased, the blade top leakage flow rate is reduced, the blade top leakage vortex strength is weakened, the pneumatic and acoustic performance of the turbine blade is improved, and the engineering requirements for resistance reduction and noise reduction of the blade grid are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of aero-turbine design, and particularly relates to a drag-reducing and noise-reducing cascade based on Blended Blade Tip and Winglet (abbreviated as BBTW). Background Art

[0002] In the 1970s, inspired by the fact that large raptors spread their wings and deflect the wingtip feathers upward during high-altitude flight to reduce drag, the Ames Research Center proposed the concept of implementing winglets at the wingtips of aircraft, and installed winglets on the KC-135 tanker, resulting in a 6.2% reduction in total drag, a 15% reduction in induced drag, and a 7.5% increase in range. Subsequently, the winglet technology has been continuously developed and has made significant contributions to the optimization of aircraft performance. Its main mechanisms are as follows:

[0003] 1. Acting as end plates to suppress tip vortices, reduce induced drag, and increase lift;

[0004] 2. Breaking the concentrated vortices dragged out at the wingtips into small-scale vortex lines and rapidly decaying, thereby dissipating the wingtip vortices;

[0005] 3. The distortion of the wingtip flow field generates an inward lateral force, which can provide thrust and lift;

[0006] 4. Delaying the separation of the wingtip airflow, increasing the stall angle of attack, and reducing the adverse pressure gradient.

[0007] Subsequently, some scholars introduced this technology into the internal flow field of turbines and found that the winglet structure at the blade tip has good application value for the performance and noise reduction of turbomachinery. However, the direct intersection of the winglet and the blade tip will cause stress concentration problems at this location. Although the process fillet can avoid stress concentration, it often fails to properly consider the side effects caused by the high loss or separation at the intersection of the leakage flow and the boundary layer here. By implementing the blended winglet modification at the blade tip of the planar cascade, the aspect ratio of the clearance channel can be increased, thereby increasing the flow resistance, reducing the flow rate of the tip leakage flow, weakening the intensity of the tip leakage vortex, and thus improving the aerodynamic and acoustic performance of the turbine blades, meeting the engineering requirements of drag reduction and noise reduction of the cascade. Summary of the Invention

[0008] The present invention provides a drag-reducing and noise-reducing cascade based on blended winglets at the blade tip. By implementing the blended winglet modification at the blade tip of the planar cascade, the aspect ratio of the clearance channel can be increased, thereby increasing the flow resistance, reducing the flow rate of the tip leakage flow, weakening the intensity of the tip leakage vortex, and thus improving the aerodynamic and acoustic performance of the turbine blades, meeting the engineering requirements of drag reduction and noise reduction of the cascade.

[0009] To achieve the above object, the present invention adopts the following specific technical solutions:

[0010] A drag - reducing and noise - reducing cascade based on the fusion of winglets, the drag - reducing and noise - reducing cascade comprising blades;

[0011] Add winglets to the tips of the blades, and perform winglet - tip fusion modification on the tips and the winglets on the suction surface and the pressure surface of the blades to increase the aspect ratio of the clearance channel.

[0012] Furthermore, the winglet - tip fusion modification is achieved by connecting the tip and the winglet with a smooth curve within the boundary - layer thickness scale.

[0013] Furthermore, the scheme adopted for the winglet - tip fusion modification includes the maximum fusion position, the maximum fusion thickness, and the fusion curve.

[0014] Furthermore, the maximum fusion position on the pressure surface is at the 50% chord - length position of the cascade pressure surface.

[0015] Furthermore, the maximum fusion position on the suction surface is at the 50% chord - length position of the cascade suction surface.

[0016] Furthermore, the maximum fusion thickness on the pressure surface is 0.8 mm.

[0017] Furthermore, the maximum fusion thickness on the suction surface is 1.5 mm.

[0018] Furthermore, the fusion curve is a Bessel curve.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] Based on the winglet - tip technology and the dihedral - angle principle, the winglet - tip fusion technology is derived. The drag - reducing and noise - reducing cascade of the present invention can increase the aspect ratio of the clearance channel by performing winglet - tip fusion modification at the tips of the planar cascade blades, thereby increasing the flow resistance, reducing the flow rate of the tip leakage flow, weakening the intensity of the tip leakage vortex, and thus improving the aerodynamic and acoustic performance of the turbomachine blades, meeting the engineering requirements of drag reduction and noise reduction for the cascade.

[0021] The drag - reducing and noise - reducing cascade of the present invention uses a smooth curve connection within the boundary - layer thickness between the tip surface and the winglet surface, while avoiding the high losses or side effects caused by the intersection of the leakage flow and the boundary layer or separation, improving the aerodynamic and acoustic performance of the turbomachine blades, and meeting the engineering requirements of drag reduction and noise reduction for the cascade.

[0022] The drag - reducing and noise - reducing cascade of the present invention greatly increases the angle between the suction surface of the blade and the winglet, which helps to reduce the separation and shedding of the boundary layer on the suction surface in this area. However, the BBTW itself will reduce the effective flow - through area of the S1 stream - surface element in the tip region and increase the wetted area, thus bringing a certain degree of metal blockage and frictional loss.

[0023] The drag-reducing and noise-reducing cascade of the present invention reduces the pressure difference between the suction surface and the pressure surface of the cascade in the tip clearance region. At the same time, the aspect ratio of the tip clearance region is increased, the boundary layer of the inner boundary of the tip clearance thickens, so that the tip leakage vortex dissipates, the flow velocity of the leakage flow decreases, and the intensity of the leakage vortex weakens. Furthermore, the total sound pressure levels of the near-field and far-field noises of the cascade vortex noise are reduced, meeting the requirement of cascade noise reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of the drag-reducing and noise-reducing cascade of the present invention and the prototype cascade;

[0025] Figure 2 is a comparison diagram of the flow rate-efficiency characteristic curves of the drag-reducing and noise-reducing cascade of the present invention and the prototype cascade;

[0026] Figure 3 is a noise spectrum diagram at the core of the tip leakage vortex of the drag-reducing and noise-reducing cascade of the present invention and the prototype cascade;

[0027] Figure 4 is a far-field noise directivity distribution diagram of the drag-reducing and noise-reducing cascade and the prototype cascade of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] As Figure 1 shown in the structure, the embodiment of the present invention provides a drag-reducing and noise-reducing cascade based on the integration of winglets at the tip. The drag-reducing and noise-reducing cascade includes blades; winglets are added to the blade tips (Blade Tip) of the blades, and the tip and the winglets are subjected to tip-winglet integration modification on the suction surface SS (Suction Surface) and the pressure surface PS (Pressure Surface) of the blades. That is, the tip-winglet integration modification connects the tip and the winglet with a smooth curve within the boundary layer thickness scale to increase the aspect ratio of the clearance channel.

[0030] When performing the tip-winglet integration modification on the tip and the winglet, the solutions adopted for the tip-winglet integration modification include the maximum integration position, the maximum integration thickness, and the integration curve, where:

[0031] The maximum fusion position of the pressure surface is at the 50% chord length position of the cascade pressure surface. The maximum fusion position of the suction surface is at the 50% chord length position of the cascade suction surface. The maximum fusion thickness of the pressure surface is 0.8 mm. The maximum fusion thickness of the suction surface is 1.5 mm. The fusion curve is a Bessel curve.

[0032] Based on the tip vane technology and the dihedral angle principle, the tip vane fusion technology is derived. The drag-reducing and noise-reducing cascade of the present invention can increase the aspect ratio of the clearance channel by implementing tip vane fusion modification at the tip of the planar cascade, thereby increasing the flow resistance, reducing the flow rate of the tip leakage flow, and weakening the intensity of the tip leakage vortex, so as to improve the aerodynamic and acoustic performance of the turbine blade and meet the engineering requirements of drag reduction and noise reduction of the cascade.

[0033] The drag-reducing and noise-reducing cascade of the present invention uses a smooth curve connection within the boundary layer thickness between the tip surface and the vane surface to improve the aerodynamic and acoustic performance of the turbine blade while avoiding the side effects of high losses or separation caused by the intersection of the leakage flow and the boundary layer, meeting the engineering requirements of drag reduction and noise reduction of the cascade.

[0034] The drag-reducing and noise-reducing cascade of the present invention greatly increases the angle between the suction surface of the blade and the vane, which helps to reduce the separation and shedding of the boundary layer on the suction surface in this area. However, BBTW itself will reduce the effective flow area of the S1 stream surface element in the tip region and increase the wetted area, thus bringing a certain degree of metal blockage and friction loss. Professor Wu Zhonghua, a famous impeller machinery expert in China, proposed the general theory of two types of relative stream surfaces. This theory divides the internal part of the turbine into the stream surface (S1 stream surface) between one blade and another blade.

[0035] The drag-reducing and noise-reducing cascade of the present invention reduces the pressure difference between the suction surface and the pressure surface of the cascade in the tip clearance region. At the same time, it increases the aspect ratio of the tip clearance region, thickens the boundary layer of the inner boundary of the tip clearance, dissipates the tip leakage vortex, reduces the flow velocity of the leakage flow, weakens the intensity of the leakage vortex, and further reduces the total sound pressure level of the near and far field noise of the cascade vortex noise, realizing the requirement of cascade noise reduction.

[0036] In this embodiment, the tip vane fusion technology is applied to a certain low-speed axial compressor cascade, and a drag-reducing and noise-reducing cascade based on tip vane fusion is designed, as Figure 1 shown. For the low-speed axial compressor cascade, specific parameters are selected within its design space by the Latin hypercube sampling method to determine the tip vane fusion design scheme. The maximum fusion position of the pressure surface of the tip vane fusion scheme is at the 50% chord length position of the cascade pressure surface, the maximum fusion thickness of the pressure surface is 0.8 mm, the maximum fusion position of the suction surface is at the 50% chord length position of the cascade pressure surface, the maximum fusion thickness of the suction surface is 1.5 mm, and the fusion curve of the tip vane fusion scheme is a Bessel curve.

[0037] The aerodynamic characteristics of the prototype cascade and the cascade with winglets integrated at the tip were analyzed. Figure 2 This is a comparison chart of the flow rate - efficiency characteristic curves of the drag - reduction and noise - reduction cascade BBTW of the embodiment of the present invention and the prototype cascade Ori. The near - field noise and far - field noise of the prototype cascade Ori and the drag - reduction and noise - reduction cascade BBTW of the embodiment of the present invention were analyzed, and the results are as Figure 3 and Figure 4 shown.

[0038] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A drag-reducing and noise-reducing cascade based on the fusion of winglets, characterized in that, Including blades; Adding winglets to the tips of the blades, and performing winglet-tip blending modification on the tip and the winglet on the suction surface and the pressure surface of the blade to increase the aspect ratio of the clearance channel.

2. The drag-reducing and noise-reducing cascade according to claim 1, characterized in that, The winglet-tip blending modification is achieved by connecting the tip and the winglet with a smooth curve within the boundary layer thickness scale.

3. The drag-reducing and noise-reducing cascade according to claim 2, wherein The scheme adopted for the winglet-tip blending modification includes the maximum blending position, the maximum blending thickness, and the blending curve.

4. The drag-reducing and noise-reducing cascade according to claim 3, wherein The maximum blending position on the pressure surface is at the 50% chord length position of the cascade pressure surface.

5. The drag-reducing and noise-reducing cascade according to claim 4, characterized in that, The maximum blending position on the suction surface is at the 50% chord length position of the cascade suction surface.

6. The drag-reducing and noise-reducing cascade according to claim 5, characterized in that, The maximum blending thickness on the pressure surface is 0.8 mm.

7. The drag-reducing and noise-reducing cascade according to claim 6, wherein The maximum blending thickness on the suction surface is 1.5 mm.

8. The drag-reducing and noise-reducing cascade according to any one of claims 3-7, characterized in that The blending curve is a Bessel curve.

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