An end region regulation method suitable for separation of a dominant corner region of a boundary layer intersection

Abstract

The present application relates to a kind of end region regulation methods suitable for boundary layer intersection dominant corner separation, belong to the technical field of aero-engine design and manufacture.Firstly, the maximum blade / end wall fusion position and the maximum fusion height are selected according to the height of the channel in the boundary layer, and the side wall blade body fusion structure is completed.Then, the position of the flow field boundary layer separation point is checked to verify that the corner separation caused by the intersection of the boundary layer is effectively weakened.On this basis, according to the intensity of the transverse secondary flow in the flow field, the size and position of the end region vortex generator are determined, and the effective elimination of the end region corner separation is realized.The present application can effectively weaken the intersection of the boundary layer, control the transverse secondary flow, greatly improve the performance of the compressor end region;It can quickly control or even weaken the corner separation through the side wall blade body fusion and end region vortex generator, improve the design efficiency of existing control measures;By precisely controlling the corner area backflow of different span height, the accumulation of a large amount of low-energy fluid in the end region is avoided, and the through-flow capacity of the end region is improved.

Description

Technical Field

[0001] This invention relates to an end-region control method applicable to boundary layer convergence-dominated corner separation, specifically an end-region control method for axial compressors with boundary layer convergence as the dominant corner separation problem, belonging to the field of aero-engine design and manufacturing technology. Background Technology

[0002] With the continuous development of aero-engine design and manufacturing capabilities, their aerodynamic performance has made great strides. However, it is still necessary to maximize the organization of high-performance, homogenized, and low-loss flow within the confined space of the fan / compressor under strong adverse pressure gradient conditions in order to ensure their aerodynamic performance.

[0003] Complex flow in the end region causes significant aerodynamic losses and remains a major factor limiting fan / compressor load breakthroughs. The complexity of compressor end-region flow is mainly manifested in: numerous and coupled influencing factors, strong flow unsteadiness, and diverse separation vortex structures. Studies have found that as blade load increases, on the one hand, the adverse pressure gradient within the flow channel strengthens, causing primary boundary layer separation in the lower kinetic energy elementary blades in the end region. This leads to mutual compression and convergence of the boundary layers between the blades and endwalls in the corner region, further compressing the flow. On the other hand, the lateral pressure difference within the channel increases, strengthening the lateral secondary flow at the endwalls. Low-energy fluids within the boundary layer are carried into the corner region, intensifying their radial migration along the blade surface, making corner separation even more severe. Therefore, two different corner-separation flow structures have emerged in the fan / compressor end region: one dominated by boundary layer convergence and the other by lateral secondary flow.

[0004] Currently, passive control measures for flow in the fan / compressor end region cannot provide precise control for different corner separation structures. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of traditional end-region control methods, such as their lack of specificity for compressor boundary layer convergence problems, leading to poor control performance. Specifically, for corner separation flow structures dominated by boundary layer convergence, this invention creatively proposes an end-region control method applicable to corner separation caused by boundary layer convergence, capable of weakening or even eliminating corner separation. The key to this invention lies in the selection of different flow control measures to weaken end-region boundary layer convergence and thus eliminate corner separation.

[0006] The technical solution adopted in this invention includes:

[0007] First, based on the boundary layer height within the channel, the maximum blade / endwall fusion position and maximum fusion height are selected to complete the sidewall-blade fusion structure. Then, the location of the boundary layer separation point in the flow field is checked to verify the effective reduction of corner separation caused by boundary layer convergence. Based on this, the size and location of the end-region vortex generator are determined according to the intensity of the transverse secondary flow in the flow field, achieving effective elimination of corner separation in the end region.

[0008] Beneficial effects

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. This invention can effectively reduce boundary layer convergence and control lateral secondary flow, thereby significantly improving compressor end-area performance;

[0011] 2. This invention can quickly control or even weaken corner separation through sidewall blade integration and end-zone vortex generator, thereby improving the design efficiency of existing control measures;

[0012] 3. This invention avoids the accumulation of a large amount of low-energy fluid in the end region by precisely controlling the backflow in the corner region with different expansion heights, thereby improving the flow capacity of the end region. Attached Figure Description

[0013] Figure 1 This refers to the spanwise cross-sectional geometry of the prototype cascade in the method embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of the end-area encryption geometry in an embodiment of the method of the present invention;

[0015] Figure 3 This is a schematic diagram of the sidewall blade fusion geometry in an embodiment of the method of the present invention;

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

[0017] Figure 5 This is a schematic diagram of the control scheme design parameters in an embodiment of the method of the present invention;

[0018] Figure 6 These are the static pressure cloud diagrams and wall limit streamlines of the design results in the embodiments of the method of the present invention. Detailed Implementation

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

[0020] An end-region control method suitable for separating dominant corner regions at boundary layer intersections includes the following steps:

[0021] Step 1: Preparation and checking of input data.

[0022] The required input data includes: blade and endwall geometry, blade chord length c, blade pitch t, ​​and boundary layer height H at the blade leading edge. BL Location S of the suction surface separation point sep (i.e., the chord length position where the axial velocity is 0);

[0023] The input data that needs to be checked includes: the blade channel geometry must meet the periodicity requirement, and the geometry of the prototype blade end area has been densified to ensure smooth subsequent shaping.

[0024] Step 2: Select the position where the suction surface and blades fuse to the maximum extent.

[0025] Specifically, the maximum fusion position W of the sidewall blades is first determined based on the input suction surface separation point position. max It should be positioned before the separation point and after 10% of the chord length to ensure that the radial pressure gradient generated by the sidewall fusion can effectively lift the low-energy fluid in the boundary layer that has begun to accumulate.

[0026] Step 3: Determine the maximum height of the suction surface blade fusion.

[0027] Specifically, after determining the maximum fusion location, based on the input boundary layer height H... BL Determine the maximum fusion height H max .

[0028] Preferably, the maximum fusion height is 20% to 50% of the endwall boundary layer thickness at the leading edge position, ensuring that the sidewall fusion generates an effective radial pressure gradient to control separation without causing significant frictional loss.

[0029] Step 4: Construct the suction surface blade fusion geometry.

[0030] Specifically, after determining the maximum fusion height and location, a Bezier curve is used to describe the fusion shape of the sidewall blades, with the leading and trailing edge fusion height set to 0. The fusion shape of the blades is then spanwise interpolated to complete the three-dimensional geometry.

[0031] Among them, the spanwise interpolation reference preferably adopts a 45° tilt angle linear control, which simplifies the control method while ensuring geometric smoothness.

[0032] Step 5: Check the flow field in the corner region.

[0033] Specifically, numerical simulations are performed on the flow field in the end region where blade fusion is applied to check whether the suction surface separation position has shifted backward and whether the area with axial velocity less than 0 near the blade and endwall has been effectively reduced. If the separation is eliminated below 5% of the blade height, proceed to step 6; if a large separation area still exists, return to steps 2 to 4 and adjust the maximum position and corresponding height of blade fusion until the low-energy fluid accumulation at the blade root is eliminated.

[0034] Step 6: Determine the dimensions of the end-region eddy current generator.

[0035] Based on the effective control of the corner separation caused by the boundary layer convergence in step 5, the axial vorticity distribution near the endwall flow field is further extracted. Given the height and length of the vortex generator, it generates reverse vorticity capable of changing the direction of the transverse secondary flow. Finally, the thickness of the vortex generator is determined to ensure the structural strength of the VG.

[0036] Step 7: Arrange the end zone eddy current generator.

[0037] Based on the numerical results of the end-region flow, the prototype two-dimensional streamline distribution at the top of the vortex generator is extracted, and the position and angle of attack of the vortex generator are arranged according to the airflow direction. Preferably, the design angle of attack of the vortex generator is in the range of 15°-25°.

[0038] Step 8: Check the flow field in the corner region.

[0039] Numerical simulation of the flow field in the end region after the vortex generator arrangement is completed is performed. If the secondary flow is not completely eliminated, return to steps 6 to 7 and readjust the vortex generator design to ensure that no lateral secondary flow is entrained in the corner separation of the suction surface, and corner separation of more than 5% expansion height is effectively eliminated.

[0040] Example

[0041] This example describes a specific implementation scheme for applying the method of the present invention.

[0042] This embodiment applies to a planar blade cascade with an inlet Mach number of 0.7, an inlet metal angle of 50.38°, and an outlet metal angle of 33.32°. According to the implementation steps of this invention, a two-dimensional cross-section is... Figure 1 Flow control in the end region is achieved using planar blade cascades. The specific implementation steps are as follows:

[0043] First, read in the input data, which includes the geometric coordinates of the blade and endwall, the blade chord length c = 70 mm, the blade pitch t = 35 mm, and the boundary layer height H at the leading edge of the blade. BL =13mm; Suction surface separation point position S sep =30.69%; the blade passage geometry meets the periodicity requirements, and the section below 30% of the end height has been densified, such as... Figure 2 As shown.

[0044] Based on the axial separation position, the maximum fusion position of the sidewall blade should be between 10% and 30.69% of the chord length. Through numerical simulation, the resulting radial pressure gradient was evaluated, and the maximum fusion position was determined to be at 21% of the chord length.

[0045] The maximum fusion height should be at H BLWithin the range of 20%-50%, for this embodiment it should be 2.6mm-7.5mm. The numerical results show that at the current maximum fusion position, when the maximum fusion height is 3mm, the boundary layer intersection can be effectively reduced.

[0046] After determining the maximum fusion position and maximum fusion height of the sidewall blades, the blade fusion shape is determined using two third-order Bezier curves with the maximum fusion position as the boundary. The fusion height at the leading and trailing edges is 0, and the middle position is interpolated using the maximum fusion height and position. Further, the blade fusion shape is spanwise modeled, and the cross-sections of each span height of the prototype are interpolated according to the blade fusion height at different axial positions. The final sidewall blade fusion shape is as follows: Figure 3 As shown.

[0047] Numerical simulations were performed on the aforementioned blade fusion design end region to ensure consistency with the prototype's inlet Mach number. The separation point S was identified during the simulation. sep Compared to the prototype, the blade was moved to a 36% axial position, and the accumulation of low-energy fluid at the blade root was effectively reduced, resulting in a decrease in the total pressure loss coefficient.

[0048] After completing the blade integration design, the axial vorticity contour map at the 0.5% span height position was extracted. The vortex generator was given a height of 1 mm and a length of 3 mm, with a thickness of 0.5 mm selected to ensure structural strength. Numerical simulations revealed that it can generate a suitable vortex, and its direction is opposite to that of the transverse secondary flow vortex.

[0049] First, based on the dimensions of the prototype separation zone and the axial position of the transverse secondary flow initiation, the vortex generator is positioned axially at a distance of -0.02 times the chord length from the leading edge, ahead of the crest line; its circumferential position is 0.68t from the suction surface side. The airflow angle at this position on the prototype is 45°, and a vortex generator angle of attack of 16° is selected. The dimensions and position of the vortex generator are as follows... Figure 4 and Figure 5 As shown.

[0050] Numerical simulation of the flow field at the blade tip region of the completed vortex generator design shows that there is no transverse secondary flow entrainment at the suction surface for separation. The airflow deflection direction decreases, and it continues to flow downstream, avoiding accumulation in the corner region. Separation above 5% expansion height is effectively eliminated. Its static pressure coefficient contour map and wall limiting streamlines are as follows: Figure 6 As shown.

[0051] 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 of boundary layer intersection dominance angle separation, characterized in that, First, the maximum blade / endwall fusion position and maximum fusion height are selected based on the boundary layer height within the channel to complete the sidewall blade fusion structure. Then, the location of the boundary layer separation point in the flow field is checked to verify the effective reduction of corner separation caused by boundary layer convergence. On this basis, the size and location of the end-zone vortex generator are determined according to the intensity of the transverse secondary flow in the flow field to effectively eliminate corner separation in the end zone. Specifically, the following steps are included: Step 1: Preparation and checking of input data; The required input data includes: blade and endwall geometry, blade chord length c, blade pitch t, ​​and boundary layer height H at the blade leading edge. BL Location S of the suction surface separation point sep ; The input data that needs to be checked includes: the blade channel geometry must meet the periodicity requirement, and the geometry of the prototype blade end area has been refined. Step 2: Select the position where the suction surface and blades fuse to the maximum extent; The maximum fusion position W of the sidewall blades is determined based on the input suction surface separation point location. max This ensures that the radial pressure gradient generated by sidewall fusion can effectively lift the low-energy fluid in the boundary layer that has begun to accumulate. Step 3: Determine the maximum height of the suction surface blade fusion; Based on the input boundary layer height H BL Determine the maximum fusion height H max ; Step 4: Construct the suction surface blade fusion geometry; Bezier curves are used to describe the fusion shape of the sidewall blades, with the leading and trailing edge fusion height being 0. The blade fusion shape is then interpolated in the spanwise direction to complete the three-dimensional geometry. Step 5: Check the flow field separation in the corner region; Numerical simulation of the flow field in the end region where blade fusion is applied is performed to check whether the suction surface separation position has shifted backward and whether the area with axial velocity less than 0 near the blade and endwall has been effectively reduced; if the separation is eliminated below 5% of the blade height, proceed to step 6; if a large separation area still exists, return to steps 2 to 4 and adjust the maximum position and corresponding height of blade fusion until the low-energy fluid accumulation at the blade root is eliminated. Step 6: Determine the dimensions of the end-region eddy current generator; Based on the effective control of the corner separation caused by the boundary layer intersection in step 5, the axial vorticity distribution near the endwall flow field is further extracted. The height and length of the vortex generator are given to generate reverse vorticity that can change the direction of the transverse secondary flow. Finally, the thickness of the vortex generator is given to ensure the strength of the VG structure. Step 7: Arrange the end-area eddy current generator; Based on the numerical results of the end region flow, the prototype two-dimensional streamline distribution at the top of the vortex generator is extracted, and the position and angle of attack of the vortex generator are arranged according to the airflow direction. Step 8: Check the flow field separation in the corner region; Numerical simulation of the flow field in the end region after the vortex generator arrangement is completed is performed. If the secondary flow is not completely eliminated, return to steps 6 and 7 and readjust the vortex generator design to ensure that no lateral secondary flow is entrained in the corner separation of the suction surface, and corner separation of more than 5% expansion height is effectively eliminated.

2. The end-region control method for separating the dominant angle region at boundary layer intersections as described in claim 1, characterized in that, In step 2, the maximum fusion position W of the sidewall blade fusion. max It is located before the separation point and after the 10% chord length position.

3. The end-region control method for separating the dominant angle region at boundary layer intersections as described in claim 1, characterized in that, In step 3, the maximum fusion height is 20% to 50% of the endwall boundary layer thickness at the leading edge position.

4. The end-region control method for separating the dominant angle region at boundary layer intersections as described in claim 1, characterized in that, In step 4, the spanwise interpolation reference uses a straight line control with a tilt angle of 45°.

5. The end-region control method for separating the dominant angle region at boundary layer intersections as described in claim 1, characterized in that, In step 7, the eddy current generator is designed with an angle of attack range of 15°-25°.

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