An air compressor stator blade profile for low reynolds number forced transition and a design method thereof

Abstract

The application provides a compressor stator airfoil for low Reynolds number forced transition and a design method thereof, and belongs to the technical field of compressors. The compressor stator airfoil comprises a leading edge, a trailing edge, a suction surface and a pressure surface. The suction surface comprises a front section, a step section and a rear section. The front section starts from a leading edge tangent point and ends at a step starting point. The step section starts at the step starting point and ends at a step ending point. The rear section starts at the step ending point and ends at a trailing edge tangent point. The leading edge tangent point is a tangent point between the leading edge and the suction surface. The trailing edge tangent point is a tangent point between the trailing edge and the suction surface. The step section comprises a step rising section and a step drop section. The step rising section is a gradually rising curve. The step drop section is an abruptly falling straight line. A connecting point between the step rising section and the step drop section is a step vertex. The step rising section starts at the step starting point and ends at the step vertex. The step drop section starts at the step vertex and ends at the step ending point. The airfoil provided by the application enhances the flow anti-separation ability and reduces the airfoil loss.

Description

Technical Field

[0001] This application relates to the field of compressor technology, and in particular to a compressor stator vane profile for forced transition at low Reynolds number and its design method. Background Technology

[0002] When aero-engines enter extremely high altitudes, the compressor Reynolds number drops significantly. Under the influence of the adverse pressure gradient, the laminar flow on the blade surface is prone to closed separation bubbles or even large open separation, causing severe channel blockage and a significant increase in total pressure loss. This leads to degradation of compressor aerodynamic performance and a reduction in the stable operating range. Forcing the laminar flow on the blade surface to transition into turbulent flow with stronger anti-separation capabilities is one effective way to suppress the low Reynolds number effect, but current conventional airfoils cannot achieve this forced transition function. Summary of the Invention

[0003] In view of this, embodiments of this application provide a compressor stator vane profile and its design method for forced transition at low Reynolds numbers, so as to achieve forced transition of the laminar boundary layer of the compressor suction surface to a turbulent boundary layer under low Reynolds number conditions, thereby achieving the effect of suppressing flow separation and improving performance.

[0004] In a first aspect, embodiments of this application provide a compressor stator blade profile for forced transition at low Reynolds numbers, including a leading edge, a trailing edge, a suction surface, and a pressure surface. The suction surface includes a leading section, a step section, and a trailing section. The leading section extends from the tangent point of the leading edge to the start point of the step, the step section extends from the start point of the step to the end point of the step, and the trailing section extends from the end point of the step to the tangent point of the trailing edge. The tangent point of the leading edge is the point of tangency between the leading edge and the suction surface, and the tangent point of the trailing edge is the point of tangency between the trailing edge and the suction surface. The step section includes a step rising section and a step falling section. The step rising section is configured as a gradually rising curve, and the step falling section is configured as a sharply falling straight line. The connection point between the step rising section and the step falling section is the step apex. The step rising section extends from the step start point to the step apex, and the step falling section extends from the step apex to the step end point.

[0005] According to a specific implementation of this application, the chordal position of the step termination point is set to 3~10% of the chord length, and the chordal position of the step start point is the chordal position of the step termination point minus 1~2% of the chord length.

[0006] According to one specific implementation of the embodiments of this application, the step height of the platform stage is 0.1~0.5mm.

[0007] According to one specific implementation of the embodiments of this application, the leading edge is set to be elliptical or circular, and the trailing edge is set to be elliptical or circular.

[0008] Secondly, embodiments of this application also provide a method for designing the stator vane profile of a compressor for forced transition at low Reynolds number as described in any embodiment of the first aspect, the method comprising:

[0009] The mid-arc line is obtained based on the meridional streamline coordinates of the airfoil and the designed blade angle distribution;

[0010] Based on the thickness distribution design of the mid-arc line, the blade profile of the basic blade shape is obtained. The blade profile includes the pressure surface profile and the suction surface profile.

[0011] The suction surface curve is modified by a step-by-step process to obtain the modified suction surface curve, which includes the front section, the step-by-step process, and the rear section.

[0012] Determine the shape of the leading and trailing edges, and determine the final airfoil shape based on the pressure surface curve and the modified suction surface curve.

[0013] According to a specific implementation of an embodiment of this application, the step of designing the thickness distribution based on the mid-arc line to obtain the blade curve of the basic blade shape includes:

[0014] Using the point on the middle arc as the center point, symmetrical stacking is performed in the normal direction of the middle arc according to the designed thickness distribution to obtain the blade curve of the basic blade shape.

[0015] According to a specific implementation of an embodiment of this application, the step-by-step reshaping of the suction surface curve includes:

[0016] Set the starting point B of the step in the chord direction L1, the ending point D of the step in the chord direction L2, and the step height H on the suction surface;

[0017] Extract the portion of the curve after the chordal position L2 at the end point D of the suction surface step to obtain the rear segment DE of the suction surface, with point E being the tail edge tangent point.

[0018] Take discrete points on curve AB before the starting point B of the suction surface step to form a set of discrete points in the front segment, with point A as the tangent point of the front edge.

[0019] By raising the step height H upwards along the normal direction of the suction surface curve at the step end point D, we obtain the step apex C;

[0020] The step vertex C is added to the previous discrete point set as the last point. The spline curve is generated by the updated previous discrete point set to generate the suction front AB and the step rising segment BC.

[0021] Connect the top point C of the step with the bottom point D of the step using a straight line to generate the step drop segment CD.

[0022] Based on the generated suction surface rear section DE, suction surface front section AB, step rising section BC, and step drop section CD, the suction surface curve of the compressor stator vane is obtained.

[0023] According to a specific implementation of an embodiment of this application, the step of raising the step height H upward along the normal direction of the suction surface curve at the step termination point D to obtain the step vertex C includes:

[0024] Based on the coordinates of the step termination point D (x D ,y D ), and calculate the slope k of the suction surface curve at the step termination point D, and the step height H, to obtain the coordinates (x, y) of the step vertex C. C ,y C ), x C = y C = .

[0025] According to a specific implementation of an embodiment of this application, the step of generating a spline curve from the updated set of discrete points in the preceding segment includes:

[0026] The updated discrete point set of the first segment is fitted with cubic polynomial spline segments to obtain spline curves.

[0027] According to a specific implementation of an embodiment of this application, the step of performing cubic polynomial spline piecewise fitting on the updated set of discrete points in the preceding segment to obtain a spline curve includes:

[0028] Let the updated set of discrete points in the first segment be [(x1,y1), (x2,y2), …, (x n ,y n ), (x C ,y C )],(x n ,y n (x) represents the coordinates of the nth discrete point in the previous discrete point set. C ,y C Let C be the coordinate of the vertex C of the step.

[0029] In [x1, x C Subintervals [x] between each adjacent point within ] i ,x i+1 Construct spline functions on [the surface]:

[0030] F i (x) = a i + b i (xx i ) + c i (xx i ) 2+ d i (xx i ) 3 ,

[0031] Among them, F i (x) is a spline function, a i b is the first coefficient. i c is the second coefficient. i The third coefficient, d i The fourth coefficient, x i Let x be the x-coordinate of the i-th discrete point. i+1 Let x be the x-coordinate of the (i+1)th discrete point;

[0032] Substituting the boundary conditions into the spline function, we solve for the first, second, third, and fourth coefficients to obtain the spline curve. The boundary conditions include:

[0033]

[0034] Among them, y i Let y be the ordinate of the i-th discrete point. i+1 Let be the ordinate of the (i+1)th discrete point. The first derivative of the spline function. It is the second derivative of the spline function.

[0035] Beneficial effects:

[0036] The compressor stator blade profile and its design method for forced transition at low Reynolds number in the embodiments of this application, by setting a step on the suction surface curve, can force the laminar boundary layer to transition to a turbulent boundary layer through the separation bubble created by the step when operating in an environment with a blade chord Reynolds number of 3E4~1E5, thereby enhancing the flow's anti-separation capability and reducing blade losses. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the compressor stator vane type for forced transition at low Reynolds number according to an embodiment of the present invention;

[0039] Figure 2 This is an enlarged view of a stage according to an embodiment of the present invention;

[0040] Figure 3This is a schematic diagram showing the stage position of the suction surface setting platform according to an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram showing the arrangement of discrete points on the front section curve of the suction head according to an embodiment of the present invention;

[0042] Figure 5 This is a schematic diagram illustrating the acquisition of step vertices according to an embodiment of the present invention;

[0043] Figure 6 This is a schematic diagram of a spline curve connecting the front section of the suction head and the stage according to an embodiment of the present invention;

[0044] Figure 7 A schematic diagram of a stepped airfoil with a suction surface obtained by supplementing the leading and trailing edges according to an embodiment of the present invention;

[0045] Figure 8 This is a schematic diagram comparing the loss coefficients of a new blade profile and its prototype at different Reynolds numbers according to an embodiment of the present invention.

[0046] Figure 9 This is a schematic diagram comparing the flow field of a new blade and a prototype under low Reynolds number conditions according to an embodiment of the present invention. Figure (a) is the prototype and Figure (b) is the new blade.

[0047] Figure 10 This is a schematic diagram of a new airfoil controlled separated flow under low Reynolds number conditions according to an embodiment of the present invention.

[0048] In the diagram: 1. Leading edge; 2. Front section; 3. Step section; 31. Step rising section; 32. Step drop section; 4. Rear section; 5. Tail edge; 6. Pressure surface; 7. Suction surface. Detailed Implementation

[0049] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0050] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0052] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0053] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0054] In a first aspect, embodiments of this application provide a compressor stator blade profile for forced transition at low Reynolds numbers, including a leading edge 1, a trailing edge 5, a suction surface 7, and a pressure surface 6. The suction surface 7 includes a leading section 2, a step 3, and a trailing section 4. The leading section 2 starts from the leading edge tangent point and ends at the step initiation point. The step 3 starts from the step initiation point and ends at the step termination point. The trailing section 4 starts from the step termination point and ends at the trailing edge tangent point. The leading edge tangent point is the tangent point between the leading edge 1 and the suction surface 7, and the trailing edge tangent point is the tangent point between the trailing edge 5 and the suction surface 7. The step 3 includes a step rising section 31 and a step drop section 32. The step rising section 31 is configured as a gradually rising curve, and the step drop section 32 is configured as a steeply falling straight line. The connection point between the step rising section 31 and the step drop section 32 is the step apex. The step rising section 31 starts from the step initiation point and ends at the step apex, and the step drop section 32 starts from the step apex and ends at the step termination point.

[0055] like Figure 1 and Figure 2As shown, the blade profile in this embodiment includes a leading edge 1, a trailing edge 5, a suction surface 7, and a pressure surface 6. The suction surface 7 is divided into three parts: a leading section 2 (AB), a step-like section (BCD), and a trailing section (DE). The leading section 2 extends from the leading edge tangent point A to the step start point B. The step-like section 3 extends from the step start point B to the step end point D. The trailing section 4 extends from the step end point D to the trailing edge tangent point E. The step-like section 3 of the suction surface 7 is further divided into a step-ascending section BC and a step-drop section CD. The step-ascending section BC extends from the step start point B to the step apex C and is a gradually rising curve. The step-drop section CD extends from the step apex C to the step end point D and is a steeply descending straight line.

[0056] The leading edge tangent point A is the intersection of the leading edge 1 and the suction surface 7, where the leading edge 1 and the suction surface 7 transition smoothly. The trailing edge tangent point E is the intersection of the trailing edge 5 and the suction surface 7, similarly ensuring a smooth connection between the trailing edge 5 and the suction surface 7. The gradual lifting design of the step-up section BC means that from the step starting point B to the step apex C, the height of the suction surface 7 gradually increases along the blade height direction, and its curve shape is optimized by fluid dynamics to guide the airflow to flow smoothly. The abrupt descent of the step drop section CD forms a significant geometric change at the step apex C, causing a strong pressure gradient change in the airflow passing through this point, thereby triggering the boundary layer transition. This stepped structure, which transitions from a curve to a straight line, forms a unique disturbance source on the suction surface 7. It can effectively control the flow state of the airflow under low Reynolds number conditions. When operating in an environment with a blade chord Reynolds number of 3E4 to 1E5, the separation bubble created by the rear step can force the laminar boundary layer to transition into a turbulent boundary layer, enhance the flow's anti-separation ability, and thus reduce blade losses.

[0057] In one embodiment, refer to Figure 3 The platform stage 3 is set before the throat of the suction surface 7. The chord position of the step end point is set to 3~10% of the chord length, and the chord position of the step start point is the chord position of the step end point minus 1~2% of the chord length.

[0058] Specifically, if the chordal position of the step termination point is set to 3% of the chord length, then the chordal position of the step initiation point is 2% to 1% of the chord length; when the chordal position of the step termination point is 10% of the chord length, the chordal position of the step initiation point is correspondingly 9% to 8% of the chord length. This setting of the chordal position allows the step structure to play a role in the early stage of airflow passing through the suction surface 7, introducing disturbances before the laminar boundary layer has fully developed, thereby more effectively triggering the transition process. At the same time, controlling the length of the step in the chordal direction within the range of 1% to 2% of the chord length ensures that a sufficiently strong pressure gradient is formed to promote boundary layer transition, while avoiding excessive flow loss due to excessively long steps.

[0059] In one embodiment, the step height of stage 3 is 0.1~0.5mm.

[0060] In one embodiment, the leading edge 1 is set to be elliptical or circular, and the trailing edge 5 is set to be elliptical or circular.

[0061] Secondly, embodiments of this application also provide a method for designing the stator vane profile of a compressor for forced transition at low Reynolds number as described in any embodiment of the first aspect, the method comprising:

[0062] Step S1: Obtain the mid-arc line based on the meridional streamline coordinates of the blade shape and the designed blade angle distribution;

[0063] Step S2: Design the thickness distribution based on the middle arc line to obtain the blade curve of the basic blade shape. The blade curve includes the pressure surface curve 6 and the suction surface curve 7.

[0064] Step S3, refer to Figures 3 to 6 The suction surface 7 curve is modified by stage 3 to obtain the modified suction surface 7 curve, which includes the front section 2, stage 3 and the rear section 4.

[0065] Step S4, refer to Figure 7 The shapes of the leading edge 1 and trailing edge 5 are determined, and the final blade shape is determined based on the pressure surface curve 6 and the modified suction surface curve 7.

[0066] In specific implementation, the leading and trailing edges of this application can be elliptical or circular. The leading edge 1 and trailing edge 5 are added to the obtained blade part. Then, the profile at the junction is locally smoothed to keep the zero-order, first-order and second-order derivatives at the junction of the leading edge 1, trailing edge 5, suction surface 7 and pressure surface 6 continuous.

[0067] Furthermore, the step of designing the thickness distribution based on the mid-arc line to obtain the blade curve of the basic blade shape includes:

[0068] Using the point on the middle arc as the center point, symmetrically stacking is performed in the normal direction of the middle arc according to the designed thickness distribution to obtain the blade curve of the basic blade shape, including the pressure surface curve 6 and the suction surface curve 7.

[0069] Furthermore, in the step of modifying the suction surface 7 curve in stage 3, the pressure surface 6 curve and the suction surface 7 curve obtained based on the mid-arc line and thickness distribution are the initial blade shape. The pressure surface 6 is not adjusted, and the suction surface 7 is modified in the following steps, specifically including:

[0070] Step S31, refer to Figure 3 On the suction surface 7, set the chord position L1 of the step start point B, the chord position L2 of the step end point D, and the step height H;

[0071] Specifically, the chordal position L1 of the step starting point B is used to control the gradient of the step rising section 31, the chordal position L2 of the step ending point D is used to control the position of the separation bubble, and the step height H is used to control the size of the separation bubble; generally, the step 3 is set before the throat of the suction surface 7, L2 can be selected as 3~10% of the chord length, L1 can be selected as L2 minus 1~2% of the chord length, and H can be selected as 0.1~0.5mm;

[0072] Step S32: Extract the part of the curve after the chordal position L2 of the termination point D of the suction surface 7 step, and obtain the rear segment DE of the suction surface 7, with point E as the tail edge tangent point;

[0073] Step S33, refer to Figure 4 Discrete points are taken on the curve AB before the starting point B of the suction surface step 7 to form the set of discrete points of the front segment 2, with point A being the tangent point of the leading edge.

[0074] Specifically, taking the compressor axis as the x-axis and the tangential direction of the rotor rotation as the y-axis, and discretizing the first segment 2 curve into n points, the discrete point set of the first segment 2 can be represented as [(x1,y1), (x2,y2), …, (x n ,y n This step generates a discrete point set so that a smooth curve can be used to fit the front section AB of the suction surface 7 and the step rising section BC later, avoiding the influence of curvature discontinuity at the junction point B of the two sections on the flow field.

[0075] Step S34, refer to Figure 5 The step end point D is raised by lifting the step height H along the normal of the suction surface curve 7 at that point, thus obtaining the step apex C;

[0076] Specifically, based on the coordinates (x, y) of the step termination point D D ,y D And given the slope k of the suction surface curve at point D, the coordinates of the step vertex C can be obtained as follows: ;

[0077] Step S35, refer to Figure 6 The step vertex C is added as the last point to the discrete point set of the first segment 2. The spline curve is generated by the updated discrete point set of the first segment 2, and the suction surface 7, the first segment AB and the step rising segment BC are generated.

[0078] Step S36, refer to Figure 6 Connect the top point C of the step with a straight line to the bottom point D of the step, thus generating the step drop segment CD;

[0079] Step S37: Based on the generated suction surface 7 rear section DE, suction surface 7 front section AB, step rising section BC, and step drop section CD, obtain the suction surface 7 curve of the compressor stator vane type.

[0080] Furthermore, the step of generating a spline curve using the updated set of discrete points in the first segment 2 includes:

[0081] The updated discrete point set of the first segment 2 is fitted with cubic polynomial spline piecewise to obtain the spline curve.

[0082] Furthermore, the step of performing cubic polynomial spline piecewise fitting on the updated first segment 2 discrete point set to obtain the spline curve includes:

[0083] Let the updated discrete point set of the first segment 2 be [(x1,y1), (x2,y2), …, (x n ,y n ), (x C ,y C )],(x n ,y n (x) represents the coordinates of the nth discrete point in the set of discrete points in the first two segments. C ,y C Let C be the coordinate of the vertex C of the step.

[0084] In [x1, x C Subintervals [x] between each adjacent point within ] i ,x i+1 Construct spline functions on [the surface]:

[0085] F i (x) = a i + b i (xx i ) + c i (xx i ) 2 + d i (xx i ) 3 ,

[0086] Among them, F i (x) is a spline function, a i b is the first coefficient. i c is the second coefficient. i The third coefficient, d i The fourth coefficient, x i Let x be the x-coordinate of the i-th discrete point. i+1 Let x be the x-coordinate of the (i+1)th discrete point;

[0087] Substituting the boundary conditions into the spline function, we solve for the first, second, third, and fourth coefficients to obtain the spline curve. The boundary conditions include:

[0088]

[0089] Among them, y i Let y be the ordinate of the i-th discrete point. i+1 Let be the ordinate of the (i+1)th discrete point. The first derivative of the spline function. It is the second derivative of the spline function.

[0090] In this embodiment, since the front section 2 of the suction surface 7 is the curved segment of the original airfoil, and the stepped rising section 31 is a modified segment based on the original airfoil profile, the two curves are generated independently, and there may be a curvature discontinuity at the junction point B. To avoid this problem, the two curves are broken down into discrete point sets and refitted with a smooth spline curve to ensure curvature continuity. In this embodiment, spline fitting using a cubic polynomial ensures that the fitted curve is continuous not only in function values ​​at each discrete point, but also in the first and second derivatives, thus forming a smooth transition curve between the front section 2 of the suction surface 7 and the stepped rising section 31, avoiding local flow disturbances caused by abrupt curvature changes. This fitting method preserves the aerodynamic characteristics of the front section 2 of the original airfoil and lays the groundwork for the geometric abrupt change of the subsequent stepped drop section 32 through the smooth rise of the stepped rising section 31, achieving a natural transition from smooth flow to disturbance triggering.

[0091] Further, in step S4, the shapes of the leading edge 1 and trailing edge 5 are determined. Based on the pressure surface 6 curve and the modified suction surface 7 curve, the final airfoil profile is determined. Specifically, the leading edge 1 adopts an elliptical or circular design to reduce flow losses at the air inlet; the trailing edge 5 also adopts an elliptical or circular design to reduce the wake effect at the air outlet. The designed leading edge 1 is smoothly connected to the leading edge tangent point A of the leading section 2 of the suction surface 7 and the leading edge 1 portion of the pressure surface 6. The designed trailing edge 5 is smoothly connected to the trailing edge tangent point E of the trailing section 4 of the suction surface 7 and the trailing edge 5 portion of the pressure surface 6, ultimately forming a complete compressor stator airfoil profile.

[0092] The compressor stator blade profile obtained through the above design method can effectively trigger boundary layer transition in stage 3 on its suction surface 7 under low Reynolds number conditions. When the airflow passes through the suction surface 7, it first passes through the smooth curve of the first section 2, where the airflow remains laminar and accelerates smoothly. Subsequently, the airflow enters stage 3, where the gradually rising curve of the step-up section 31 causes the airflow path to bend slightly upward, and the airflow can still maintain a relatively stable laminar boundary layer. When the airflow reaches the step apex C, it suddenly encounters the abrupt descent of the step drop section 32. This drastic change in geometry causes a significant adverse pressure gradient to be generated near the step apex C, leading to rapid boundary layer separation and the formation of separation bubbles. The turbulent flow inside the separation bubbles generates a large number of turbulent vortices, which, through momentum exchange with the mainstream, force the laminar boundary layer to transform into a turbulent boundary layer. The transformed turbulent boundary layer has a stronger momentum transfer capability, which can effectively resist the adverse pressure gradient that may occur downstream, avoid the occurrence of large-area flow separation, thereby significantly reducing the friction loss and separation loss of the airfoil surface, and improving the efficiency and stable operating range of the compressor under low Reynolds number conditions.

[0093] In order to test the effect of the suction surface 7 post-step compressor stator blade profile proposed in this application for forced transition at low Reynolds number, the blade profile of the first stage stator blade of a certain low Reynolds number compressor was used as a prototype, and a new blade profile was obtained by redesigning it using the design method of this application. The performance of the new blade profile and the prototype were compared at different Reynolds number ranges.

[0094] In this embodiment, the airfoil is designed with an incoming Mach number of 0.6 and a Reynolds number of 5E4. The prototype is a multi-circle airfoil. The design parameters of the new airfoil, redesigned according to the design method of this application, are L1 = 2% chord length, L2 = 4% chord length, and H = 0.3 mm. The airfoil loss coefficient is determined by numerical calculation using the computational fluid dynamics software CFX. Figure 8 The study presents a comparison of the airfoil loss coefficient changes between the prototype and the new airfoil at an incoming flow angle of attack of -0.4° within the Reynolds number range of 3E4 to 4E5. When the Reynolds number is below 1E5, the loss coefficient of the new airfoil decreases by 22% to 31% compared to the prototype.

[0095] The main reason for the reduced loss coefficient of the new airfoil under low Reynolds number conditions is that the new airfoil provides good control over laminar open-loop separation on the suction surface of the 7-blade at low Reynolds number conditions. Taking the state point of Reynolds number 5E4 as an example, such as... Figure 9 As shown, the new blade shape eliminates the large open separation in the rear half of the suction surface 7.

[0096] The main reason why the new airfoil suppresses separation under low Reynolds number conditions is that the laminar boundary layer on the suction surface is forcibly transformed into a turbulent boundary layer with stronger anti-separation capabilities, such as... Figure 10As shown, the new blade profile draws out a long strip of separation bubble after the rear step. The separation bubble induces separation transition, and the subsequent flow is a turbulent boundary layer, thereby achieving the purpose of eliminating open separation and reducing losses.

[0097] The embodiments provided by this invention achieve effective control of boundary layer transition under low Reynolds number (blade chord Reynolds number 3E4~1E5) conditions by setting a specific structured step 3 on the suction surface 7 of the compressor stator blade. This step 3 consists of a gradually rising curved ascent section BC and a sharply descending straight drop section CD. By rationally setting its chordal position and step height, disturbances can be introduced into the airflow early as it passes through the suction surface 7. The geometric abrupt change in the step drop section 32 generates a strong pressure gradient, inducing the formation of small-scale separated bubbles, thereby forcibly transitioning the laminar boundary layer to a turbulent boundary layer. Test results show that, compared with the prototype airfoil, the airfoil designed using this invention can reduce the airfoil loss coefficient by 22-31% under low Reynolds number conditions (Reynolds number below 1E5). The main reason is that the laminar open large separation in the rear half of the suction surface 7 is successfully eliminated. The transition from laminar to turbulent flow is achieved through the separation bubble induced by the rear step, which enhances the flow's anti-separation ability, thereby effectively reducing airfoil loss and improving the aerodynamic performance and stable operating range of the compressor in low Reynolds number environments.

[0098] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for designing the stator vane profile of a compressor for forced transition at low Reynolds numbers, characterized in that, The method includes: The mid-arc line is obtained based on the meridional streamline coordinates of the airfoil and the designed blade angle distribution; Based on the thickness distribution design of the middle arc, the blade curve of the basic blade shape is obtained. The blade curve includes the pressure surface (6) curve and the suction surface (7) curve. The suction surface (7) curve is modified by stage (3) to obtain the modified suction surface (7) curve. The modified suction surface (7) curve includes the front section (2), stage (3) and the rear section (4). Determine the shape of the leading edge (1) and trailing edge (5), and determine the final blade shape based on the pressure surface (6) curve and the modified suction surface (7) curve; The step-by-step (3) modification of the suction surface (7) curve includes: Set the chordal position L1 of the step start point B, the chordal position L2 of the step end point D, and the step height H on the suction surface (7); Cut off the part of the curve after the chord position L2 of the step termination point D of the suction surface (7) to obtain the rear segment DE of the suction surface (7), with point E being the tail edge tangent point; Take discrete points on the curve AB before the starting point B of the suction surface (7) step to form the discrete point set of the front segment (2), with point A being the tangent point of the front edge; Raise the step height H upward along the normal of the suction surface (7) curve at the end point D of the step to obtain the step apex C; The step vertex C is added as the last point to the discrete point set of the previous segment (2). The spline curve is generated through the updated discrete point set of the previous segment (2) to generate the suction surface (7) the previous segment AB and the step rising segment BC. Connect the top point C of the step with the bottom point D of the step using a straight line to generate the step drop segment CD. Based on the generated suction surface (7) rear section DE, suction surface (7) front section AB, step rising section BC and step drop section CD, the suction surface (7) curve of the compressor stationary vane type is obtained. The step height H is raised upward along the normal direction of the suction surface (7) curve at the end point D of the step to obtain the step apex C, including: Based on the coordinates of the step termination point D (x D ,y D ), and the slope k of the suction surface (7) curve at the step termination point D and the step height H, to obtain the coordinates (x, y) of the step vertex C. C ,y C ), x C = y C = .

2. The design method according to claim 1, characterized in that, The process of designing the thickness distribution based on the mid-arc line to obtain the blade curve of the basic blade shape includes: Using the point on the middle arc as the center point, symmetrical stacking is performed in the normal direction of the middle arc according to the designed thickness distribution to obtain the blade curve of the basic blade shape.

3. The design method according to claim 1, characterized in that, The process of generating spline curves from the updated discrete point set of the preceding segment (2) includes: The updated discrete point set of the first segment (2) is fitted with cubic polynomial spline piecewise to obtain the spline curve.

4. The design method according to claim 3, characterized in that, The step of performing cubic polynomial spline piecewise fitting on the updated discrete point set of the first segment (2) to obtain the spline curve includes: Let the updated discrete point set of the first segment (2) be [(x1,y1), (x2,y2), …, (x n ,y n ), (x C ,y C )],(x n ,y n ) represents the coordinates of the nth discrete point in the discrete point set of the previous segment (2), (x C ,y C Let C be the coordinate of the top vertex of the step. In [x1, x C Subintervals [x] between each adjacent point within ] i ,x i+1 Construct spline functions on [the surface]: F i (x) = a i + b i (x-x i ) + c i (x-x i ) 2 + d i (x-x i ) 3 , Among them, F i (x) is a spline function, a i b is the first coefficient. i c is the second coefficient. i The third coefficient, d i The fourth coefficient, x i Let x be the x-coordinate of the i-th discrete point. i+1 Let x be the x-coordinate of the (i+1)th discrete point; Substituting the boundary conditions into the spline function, we solve for the first, second, third, and fourth coefficients to obtain the spline curve. The boundary conditions include: Among them, y i Let y be the ordinate of the i-th discrete point. i+1 Let be the ordinate of the (i+1)th discrete point. The first derivative of the spline function. It is the second derivative of the spline function.

5. A compressor stator vane profile for forced transition at low Reynolds numbers, designed using the design method described in any one of claims 1-4, characterized in that, It includes a leading edge (1), a trailing edge (5), a suction surface (7), and a pressure surface (6). The suction surface (7) includes a front section (2), a platform stage (3), and a rear section (4). The front section (2) starts from the tangent point of the leading edge and ends at the starting point of the step. The platform stage (3) starts from the starting point of the step and ends at the ending point of the step. The rear section (4) starts from the ending point of the step and ends at the tangent point of the trailing edge. The tangent point of the leading edge is the tangent point between the leading edge (1) and the suction surface (7). The tangent point of the trailing edge is the tangent point between the trailing edge (5) and the suction surface (6). The tangent point of the force surface (7); the stage (3) includes the step rising section (31) and the step drop section (32). The step rising section (31) is set as a gradually rising curve, and the step drop section (32) is set as a straight line that drops sharply. The connection point of the step rising section (31) and the step drop section (32) is the top of the step. The step rising section (31) starts from the starting point of the step and ends at the top of the step. The step drop section (32) starts from the top of the step and ends at the end point of the step.

6. The compressor stator vane profile for forced transition at low Reynolds number according to claim 5, characterized in that, The chord position of the step termination point is set to 3~10% of the chord length, and the chord position of the step start point is the chord position of the step termination point minus 1~2% of the chord length.

7. The compressor stator vane profile for forced transition at low Reynolds number according to claim 5, characterized in that, The step height of stage (3) is 0.1~0.5mm.

8. The compressor stator vane profile for forced transition at low Reynolds number according to claim 5, characterized in that, The leading edge (1) is set to be elliptical or circular, and the trailing edge (5) is set to be elliptical or circular.

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