An end region regulation method for controlling incoming flow boundary layer distortion

Abstract

The present application relates to a kind of control end region regulation method of incoming flow boundary layer distortion, belong to the technical field of aero-engine aerodynamic design.In the position of blade end region leading edge, vortex generator is arranged, for correcting the direction of leading edge airflow.First, according to the height of original prototype boundary layer, the height of required vortex generator is determined.Then, according to the height of original prototype suction surface separation, the length of vortex generator is determined, so that it generates appropriate size of concentrated shedding vortex.When the size of vortex generator is determined, according to the height of incoming flow attack angle and boundary layer distortion, the position of vortex generator is determined, and the arrangement of leading edge vortex generator is realized.The present application reduces the incoming flow attack angle, and enhances the end region flow capacity.The present application does not affect the blade itself profile and structure, and can be flexibly adjusted according to different compressor and incoming flow distortion model.Control scheme.Compared with traditional control technology, the design efficiency is further improved.The present application improves the corner separation of end region, and effectively improves the end region aerodynamic performance.

Description

Technical Field

[0001] This invention relates to an end-region control method for controlling the torsion of the incoming boundary layer, belonging to the field of aero-engine aerodynamic design technology. Background Technology

[0002] The aerodynamic design of aero engines has a crucial impact on engine performance. Among these challenges, the aerodynamic design difficulties for core aero engine components such as compressors and turbines are primarily concentrated in the end regions. Numerous studies have shown that end-region aerodynamic losses can account for more than 30% of the total aerodynamic losses of a compressor.

[0003] End-zone aerodynamic losses have a significant negative impact on the overall performance of the compressor. The main causes include boundary layer convergence due to the adverse pressure gradient, lateral secondary flow caused by circumferential pressure difference, and boundary layer distortion due to uneven incoming flow. In particular, the end-zone incoming flow distortion is persistent due to factors such as relative rotation, lateral secondary flow in the upstream blade passage end zone, and inter-blade leakage. This end-zone flow distortion forces the elementary blades to operate at high angles of attack, causing corner separation and further deteriorating compressor performance.

[0004] Currently, research on end-area control techniques for incoming flow distortion is relatively limited. Sauer et al. found that using a convex hull on the endwall at the leading edge can reduce secondary flow losses intensified by airflow distortion. Hoeger, through studies on in-line blades, discovered that boundary layer distortion under varying operating conditions has a significant impact on compressor aerodynamic performance, proposing a modification scheme involving adding corner rounding structures, and suggesting that applying leading-edge rounding can eliminate separation clusters and improve blade loading capacity. However, further in-depth research is needed on the control mechanism, design criteria, and application stability.

[0005] Therefore, the key to effectively controlling the boundary layer distortion of the incoming flow is to apply flow control measures near the leading edge of the blades to straighten the distorted flow and enable the incoming flow to operate at a normal or small angle of attack. Summary of the Invention

[0006] The purpose of this invention is to effectively solve the technical problem of compressor boundary layer distortion in aero-engine design. It creatively proposes an end-region control method for controlling the boundary layer distortion of the incoming flow, which can reduce the angle of attack of the incoming flow and lift the low-energy fluid at the root.

[0007] The innovations of this invention include: arranging a vortex generator-like device at the leading edge of the blade tip region to correct the airflow direction at the leading edge. First, the required vortex generator height is determined based on the prototype boundary layer height. Then, the vortex generator length is determined based on the prototype suction surface separation height to generate a concentrated shedding vortex of appropriate size. After determining the vortex generator size, the vortex generator position is determined based on the incoming flow angle of attack and the boundary layer torsion height, thus realizing the leading edge vortex generator arrangement.

[0008] Beneficial effects

[0009] The method of the present invention has the following advantages compared with the prior art:

[0010] 1. This invention improves the twisted incoming flow of the boundary layer near the leading edge of the blade by using concentrated vortices generated by a vortex generator, thereby reducing the angle of attack of the incoming flow and enhancing the flow capacity in the end region;

[0011] 2. This invention uses a vortex generator to adjust the airflow direction without affecting the blade profile and structure. The control scheme can be flexibly adjusted according to different compressors and incoming flow distortion models. Compared with traditional control technologies, this further improves design efficiency.

[0012] 3. This invention elevates the low-energy fluid within the boundary layer to the mainstream, thereby reducing boundary layer convergence and accumulation, further improving corner separation in the end region, and effectively enhancing the aerodynamic performance of the end region. Attached Figure Description

[0013] Figure 1 This is the prototype cascade geometry in the method embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of the incoming boundary layer model in an embodiment of the method of the present invention;

[0015] Figure 3 This is the turbulent kinetic energy flow field near the endwall of the prototype blade cascade in the method embodiment of the present invention;

[0016] Figure 4 This is a schematic diagram showing the size and position of the eddy current generator in an embodiment of the method of the present invention;

[0017] Figure 5 This is a schematic diagram of the angle of attack of the eddy current generator in an embodiment of the method of the present invention;

[0018] Figure 6 This is the flow field of the design scheme in the embodiment of the method of the present invention. Detailed Implementation

[0019] The method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] The present invention is achieved using the following technical solution.

[0021] An end-region control method for controlling the torsion of the incoming boundary layer includes the following steps:

[0022] Step 1: Input data preparation and checking.

[0023] The required input data includes: blade and endwall geometric coordinates, blade pitch t, ​​blade chord length C and axial chord length Cx, mounting angle γ, and blade leading edge coordinates (X). LE Y LE (X) LE Represents the axial coordinate of the leading edge point, Y LE (Represents the circumferential coordinates of the leading edge point), blade inlet metal angle β 1k and the angle of attack i, and the separation height H of the prototype suction surface. sep (This can be obtained from numerical simulation results).

[0024] Step 2: Design the incoming boundary layer model.

[0025] Given the velocity distribution of the inlet torsional boundary layer, the maximum torsional velocity Vy_max and its corresponding boundary layer height h1, and the overall boundary layer height h2, where linear control is used from 0 to h1, and 1 / 7 law control is used from h1 to h2, as shown in Equation 1:

[0026]

[0027] Among them, V main The current velocity is represented by h, the current boundary layer height is represented by h, and the current velocity is represented by V.

[0028] Step 3: Determine the size of the eddy current generator.

[0029] The height of the eddy current generator is determined based on the height h1 of the boundary layer where the maximum torsional velocity is located. Preferably, the height of the eddy current generator ranges from 0.3h1 to 0.8h1.

[0030] The turbulent kinetic energy distribution TKE near the prototype endwall flow field is extracted, as shown in Equation 2:

[0031]

[0032] Where the subscript z represents the axial velocity, y represents the circumferential velocity, and v′ represents the instantaneous velocity. This indicates the average speed.

[0033] Numerical simulations were performed with different vortex generator lengths. The resulting changes in the boundary layer flow near the leading edge were compared, and the vortex generator length was determined based on the end-region flow field to effectively control suction surface corner separation. Finally, the vortex generator thickness was set to ensure the strength of the VG structure; preferably, the value ranged from 0.5 mm to 1.0 mm.

[0034] Step 4: Arrangement of end-zone eddy current generators.

[0035] Given the dimensions of the vortex generator, the location of the vortex generator is determined based on the numerical results of the flow in the end region.

[0036] First, give the axial distance D between the point of maximum axial position of the eddy current generator and the leading edge point. LE The axial position of the eddy current generator should be close to the boundary of the recirculation zone formed by the leading edge stagnation point to avoid eddy current generator failure. The circumferential position is directly opposite the leading edge point to control the angle of attack of the incoming flow.

[0037] Step 5: Determine the geometric angle of the eddy current generator.

[0038] The eddy current generator makes an angle α with the horizontal direction. VG The expression is shown in Equation 3:

[0039] α VG =β 1k +i+Δα (3)

[0040] Where, β 1k Δα represents the angle of attack of the imported metal, i represents the current angle of attack under operating conditions, and Δα represents the angle of attack of the eddy current generator, preferably 5°-10°.

[0041] Through flow field simulation, the geometric angle that yields the best working effect for the eddy current generator is selected.

[0042] Step 6: Verify the design results.

[0043] The flow field of the vortex generator near the leading edge was simulated to verify whether the large angle of attack of the incoming flow in the corner region was improved and whether the corner separation was effectively reduced.

[0044] Calculate the flow field characteristics, and if the results are abnormal, re-define the design parameters.

[0045] Provided it is used properly, the design results should meet the needs of engineering applications.

[0046] Example

[0047] This embodiment describes a specific implementation scheme for applying the method of the present invention.

[0048] The application scenario of this embodiment is a planar blade cascade with a maximum blade thickness of 7% of the chord length, located at the 42% chord length position, a leading edge radius of 0.67mm, a trailing edge radius of 0.32mm, and a blade bend angle of 25°.

[0049] According to the implementation steps of this invention, the initial state is... Figure 1 The inflow distortion control is performed using a planar blade cascade, and the specific implementation steps are as follows:

[0050] The input data includes: blade and endwall geometric coordinates; blade pitch t = 27 mm; blade chord length C = 48.73 mm; axial chord length Cx = 48 mm; installation angle γ = 9.96°; and blade leading edge coordinates (X). LE =0.0, Y LE =0.0); Blade inlet metal angle β 1k =25°; Subsequent steps were carried out under a large angle of attack condition, with an angle of attack of 5°. The separation height H of the prototype suction surface was obtained based on the numerical simulation results. sep =14.96% mm.

[0051] Given the maximum torsional velocity Vy_max = 8.2 m / s and its height h1 = 2.2 mm, and the overall boundary layer height at the leading edge is 10 mm, the velocity distribution of the inlet torsional boundary layer obtained from the model is as follows: Figure 2 As shown.

[0052] With h1 = 2.2 mm, the maximum height of the eddy current generator ranges from 0.66 mm to 1.76 mm; a height of 1 mm is chosen. The turbulent kinetic energy distribution (TKE) near the prototype's endwall at a distance of 1 mm is shown below. Figure 3 As shown, to ensure the intensity of the concentrated shedding vortex, the length of the vortex generator is set to 5 mm. Due to the low height of the vortex generator (VG), the thickness of the VG is set to 0.5 mm to reduce aerodynamic losses while ensuring structural strength.

[0053] The eddy current generator position parameter is the axial position from the leading edge point, D. LE The value is taken as the recirculation zone formed by the leading edge stagnation point, and is set to 2.2 mm. The size and position of the eddy current generator are as follows: Figure 4 As shown.

[0054] For this implementation case, as described in step 1 regarding the input parameters, β 1k Given an angle of 25° and i = 5°, flow field simulation shows that the optimal control angle Δα is 7°, ultimately yielding α. VG It is 37°, such as Figure 5 As shown.

[0055] Numerical simulation was performed on the vortex generator arrangement described in this embodiment, and the resulting blade wall streamlines and zero axial velocity isosurface are shown below. Figure 6 As shown in the figure, the size and strength of the hub-side separation zone are reduced after the application of end-area flow torsion control, indicating that the design is reasonable and effective.

[0056] The above description is merely an illustrative embodiment of the present invention, and the present invention should not be limited to the content disclosed in this embodiment and the accompanying drawings. Any equivalent or modified versions made without departing from the spirit of the present invention fall within the scope of protection of the present invention.

Claims

1. A method for controlling the end-region distortion of the incoming boundary layer, characterized in that: A vortex generator-like device is placed at the leading edge of the blade tip region to correct the direction of the airflow at the leading edge; First, determine the required eddy current generator height based on the prototype boundary layer height; Then, the length of the vortex generator is determined based on the separation height of the prototype suction surface, so that it generates a concentrated shedding vortex of appropriate size; Once the size of the eddy generator is determined, the position of the eddy generator is determined based on the angle of attack of the incoming flow and the height of the boundary layer torsion, thus realizing the arrangement of the leading edge eddy generator. The design of the flow boundary layer model is as follows: Given the velocity distribution of the inlet torsional boundary layer, the maximum torsional velocity Vy_max and its corresponding boundary layer height h1, and the overall boundary layer height h2, where linear control is used from 0 to h1, and 1 / 7 law control is used from h1 to h2, as shown in Equation 1: （1） Among them, V main The current velocity is represented by h, the current boundary layer height is h, and the current velocity is V. Then, determine the height of the eddy current generator; determine the height of the eddy current generator based on the height h1 of the boundary layer where the maximum torsional velocity is located; Given different vortex generator lengths and performing numerical simulations, the turbulent kinetic energy distribution TKE near the prototype endwall flow field is extracted, as shown in Equation 2: （2） Where the subscript z represents the axial velocity and y represents the circumferential velocity; Indicates instantaneous velocity. Indicates average speed; By comparing the changes in the boundary layer near the leading edge caused by the vortex generator, the length of the vortex generator is determined in combination with the flow field in the end region, so that it can effectively control the separation of the suction surface corner region; finally, the thickness of the vortex generator is given to ensure the strength of the VG structure. Given the dimensions of the vortex generator, determine the location of the vortex generator based on the numerical results of the flow in the end region; First, give the axial distance D between the point of maximum axial position of the eddy current generator and the leading edge point. LE The axial position of the eddy current generator should be close to the boundary of the recirculation zone formed by the stagnation point at the leading edge to avoid eddy current generator failure; the circumferential position should be directly opposite the leading edge point to control the angle of attack of the incoming flow. The method for determining the geometric angles of the eddy current generator is as follows: The angle between the eddy current generator and the horizontal direction The expression is shown in Equation 3: （3） in, It is an imported metal corner. Angle of attack for the current operating conditions; This indicates the angle of attack of the eddy current generator.

2. The end-region control method for controlling the distortion of the incoming boundary layer as described in claim 1, characterized in that, This includes input data preparation and checking; The required input data are: blade and endwall geometric coordinates, blade pitch t, ​​blade chord length C and axial chord length Cx, installation angle γ, and blade leading edge coordinates (X). LE Y LE ), blade inlet metal angle β 1k and the angle of attack i, and the separation height H of the prototype suction surface. sep .

3. The end-region control method for controlling the distortion of the incoming boundary layer as described in claim 1, characterized in that, The height of the eddy current generator ranges from 0.3h1 to 0.8h1.

4. The end-region control method for controlling the distortion of the incoming boundary layer as described in claim 1, characterized in that, The thickness of the eddy current generator ranges from 0.5mm to 1.0mm.

5. The end-region control method for controlling the torsion of the incoming boundary layer as described in claim 1, characterized in that, Take 5°-10°.

6. The end-region control method for controlling the torsion of the incoming boundary layer as described in claim 1, characterized in that, Including the verification of design results; Simulations were performed on the flow field of the vortex generator near the leading edge to verify whether the large angle of attack of the incoming flow in the corner region was improved and whether the corner separation was effectively reduced. Calculate the flow field characteristics, and if the results are abnormal, re-define the design parameters.

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