阅读说明：本技术 一种压气机叶型非对称前缘设计方法 (Design method for asymmetric leading edge of compressor blade profile ) 是由 高丽敏 杨冠华 王浩浩 张栋 于 2020-06-24 设计创作，主要内容包括：本发明涉及一种压气机叶型的非对称前缘设计方法,对叶型前缘进行参数化,并减小压力面侧前缘设计空间,扩展吸力面侧前缘设计空间,基于三次NURBS曲线生分别生成吸力面和压力面侧前缘型线并判断是否满足曲率连续。本方法所设计前缘在满足曲率连续的前提下,实现了吸、压力面两侧非对称的前缘型线构造,使吸力面侧前缘型线曲率进一步缩小,吸力峰强度明显削弱,叶型整体损失降低。(The invention relates to a method for designing an asymmetric leading edge of a compressor blade profile, which is characterized by carrying out parameterization on a leading edge of the compressor blade profile, reducing a design space of the leading edge on a pressure surface side, expanding the design space of the leading edge on a suction surface side, respectively generating molded lines of the leading edge on the suction surface side and the leading edge on the pressure surface side based on a cubic NURBS curve and judging whether the continuous curvature is met. The designed front edge realizes the asymmetrical front edge molded line structure on the two sides of the suction surface and the pressure surface on the premise of meeting the requirement of continuous curvature, so that the front edge molded line curvature on the suction surface side is further reduced, the strength of a suction peak is obviously weakened, and the overall loss of the blade profile is reduced.)

1. A design method for an asymmetric leading edge of a compressor blade profile is characterized by comprising the following steps: comprises the following steps:

step 1, constructing a front edge parameterization control line according to a geometric molded line of a blade profile to be designed, and a point S_CAnd P_CIs the connection point of the leading edge of the blade profile with the suction surface and the pressure surface of the blade body respectively, and is a line SS_CWith PP_CIs an extension line at the blade body, is respectively tangent with the molded line of the suction surface and the molded line of the pressure surface, and a line SP passes through a leading edge point D, is arranged in a direction vertical to the geometric air inlet angle of the blade profile and is perpendicular to the SS_CAnd PP_CRespectively intersect at point S and point P, point S₁、S₂、P₁、P₂Each being a movable point on a respective tangent line segment, the parameterized control line comprising a segment SS_CSegment SP and segment PP_CComposition is carried out;

step 2, adjusting the leading edge molded line design space, moving the original leading edge point D to the point P along the line segment SP, and obtaining a new leading edge point D₁The design space of leading edge profile on suction side is adjusted to D₁S+SS_CThe design space of the leading edge profile on the pressure surface side is adjusted to D₁P+PP_CFrom point D₁、S₁、S₂、S_CFour points are used as control points of the profile line on the side of the asymmetric leading edge suction surface, point D₁、P₁、P₂、P_CFour points are used as control points of the asymmetric leading edge pressure surface side molded line;

step 3, modifying the control point, and moving S in the leading edge control point on the suction surface side₁Dot sum S₂Point, and pressure side leading edge controlP in a dot₁Point sum P₂The moving range of the point is limited on the control line segment where the point is located, and the following are defined:

to be provided with

step 4, generating a leading edge molded line and combining the newly obtained suction surface leading edge control points D₁、S₁、S₂、S_CGenerating an open cubic NURBS curve for the control point; at the same time, the newly obtained pressure surface leading edge control point combination D₁、P₁、P₂、P_CFor the control points, a first three NURBS curve is generated, which is generated as follows:

calculating N from the Deboolean-Cocker recursion equation_i,3(u)：

Step 5, judging whether the curvature is continuous or not, and calculating a new leading edge point D₁Two-side curvature, suction surface front edge and blade body connecting point S_CTwo-side curvature, pressure surface front edge and blade body connecting point P_CThe two-side curvature has the following calculation formula:

and (3) calculating the curvature error of the two sides within the range that the delta kappa/kappa is less than or equal to 0.5%, namely, considering that the curvature of the curve at the end point position is continuous to obtain a group of asymmetric leading edge profile design results, and repeating the step (3) if the curvature error is discontinuous.

2. The method for designing the asymmetrical leading edge of the compressor airfoil according to claim 1, wherein: and (3) parameterizing the blade profile leading edge through a cubic NURBS curve, and reducing the design space of the leading edge on the pressure surface side to expand the design space of the leading edge on the suction surface side so as to generate an asymmetric leading edge profile.

Technical Field

The invention relates to a design method of an asymmetric leading edge of a compressor blade profile. In particular to a design method for a leading edge molded line of an axial flow compressor blade profile of an aircraft engine or a gas turbine.

Background

The compressor is one of the key parts of an aeroengine and a gas turbine, the blade is the basic component unit of the compressor, and the aerodynamic performance of the blade profile needs to be continuously improved in order to improve the efficiency of the compressor. The front edge is the initial position of the blade profile surface flow, and compared with other parts, the shape of the blade profile front edge directly influences the development of the boundary layer along the blade surface and the downstream flow field structure, and plays an important role in the overall performance of the blade profile.

The large and discontinuous curvature of the leading edge, which causes excessive expansion of the air flow to generate the suction peak of the leading edge pressure distribution, is one of the main sources of the blade profile loss. By reasonably designing the leading edge molded line, the curvature distribution of the leading edge can be improved, the continuous curvature is realized, the suction peak is weakened, the separation bubble is controlled, and the pneumatic performance of the blade profile is improved.

The currently available leading edge shaping methods result in leading edges that are symmetrical both on the suction side and on the pressure side. For a compressor blade profile, the flow on the suction surface side is more important and unstable, the pneumatic loss source of the blade profile occupies a larger part and has higher sensitivity to the shape of the leading edge, and the flow on the pressure surface side is more stable, the loss is lower and the influence of the leading edge is smaller. Therefore, the asymmetric design of the leading edges on the two sides can be carried out, the leading edge profile design space on the suction surface side is expanded by sacrificing part of the leading edge profile design space on the pressure surface side, the curvature of the leading edge on the suction surface side is further reduced, the strength of a suction peak is weakened, and the overall aerodynamic performance of the blade profile is further improved.

Disclosure of Invention

The traditional design method of the leading edge has the defects that the curvature of the molded lines of the arc-shaped leading edge and the oval leading edge is large and the connection part with the blade body is discontinuous, so that the larger suction peak intensity and the leading edge separation bubble are caused; the existing curvature continuous front edge design treats molded lines on both sides of the suction surface and the pressure surface equally, and during design, the variable design spaces of the molded lines on the front edge on both sides are consistent, so that the further control on the curvature of the molded line on the front edge on the suction surface side is limited, the strength of a suction peak of the front edge cannot be further weakened, and the pneumatic loss is large under a large inlet airflow angle.

In order to solve the problems, the invention provides an effective compressor blade profile asymmetric leading edge design method, which parameterizes a blade profile leading edge through three times of NURBS curves, reduces a pressure surface side leading edge design space to expand a suction surface side leading edge design space and generates an asymmetric leading edge profile. The method not only meets the requirement of continuous curvature of the front edge, but also realizes the asymmetric front edge molded line structure at the two sides of the suction surface and the pressure surface, the curvature of the front edge molded line at the suction surface side is further reduced, and the suction peak intensity and the blade loss are reduced.

The design method of the asymmetrical leading edge of the compressor blade profile comprises the following steps:

step 1, constructing a front edge parameterization control line according to the geometric molded line of the blade profile to be designed. Including original leading edge point D, line segment SS_CSegment SP and segment PP_C。

And 2, adjusting the design space of the leading edge profile. Moving the original leading edge point D to the point P along the line segment SP to obtain a new leading edge point D₁The design space of leading edge profile on suction side is adjusted to D₁S+SS_CThe design space of the leading edge profile on the pressure surface side is adjusted to D₁P+PP_C。

And 3, modifying the control point. Moving S in leading edge control points on suction side₁Dot sum S₂Point, and P in pressure surface side leading edge control point₁Point sum P₂And (4) obtaining a group of new control point combinations of the front edge of the suction surface and the front edge of the pressure surface side.

And 4, generating a leading edge molded line. With newly obtained suction surface leading edge control point combination D₁、S₁、S₂、S_CGenerating an open cubic NURBS curve for the control point; at the same time, the newly obtained pressure surface leading edge control point combination D₁、P₁、P₂、P_CFor control points, a first three NURBS curve is generated.

And 5, judging whether the curvature is continuous or not. Calculating a new leading edge point D₁Two-side curvature, suction surface front edge and blade body connecting point S_CTwo-side curvature, pressure surface front edge and blade body connecting point P_CAnd (3) curvature of two sides and judging whether the curvature is continuous or not, if the curvature is continuous, obtaining a group of front edge design results, and if the curvature is discontinuous, repeating the step (3).

The invention has the advantages that the asymmetric leading edge design can be rapidly carried out on the blade profile of the air compressor, the obtained leading edge molded line can ensure the continuous curvature, and simultaneously has the asymmetric characteristic, so that the curvature of the leading edge on the suction surface side is further reduced, the strength of the suction peak of the leading edge is obviously weakened, the overall aerodynamic loss of the blade profile is obviously reduced, and the low-loss working range is enlarged.

Drawings

FIG. 1 is an asymmetric leading edge design flow;

FIG. 2 is a schematic diagram of an asymmetric leading edge profile configuration method;

FIG. 3 is a result of an asymmetric leading edge profile design;

FIG. 4 is a comparison of aerodynamic performance of an asymmetric leading edge profile.

Detailed Description

The specific steps of the present invention will be further explained with reference to the accompanying drawings.

Step 1, constructing a front edge parameterization control line according to the geometric molded line of the blade profile to be designed. Point S_CAnd P_CIs the connection point of the leading edge of the blade profile with the suction surface and the pressure surface of the blade body respectively, and is a line SS_CWith PP_CIs an extension line at the blade body, is respectively tangent with the molded line of the suction surface and the molded line of the pressure surface, and a line SP passes through a leading edge point D, is arranged in a direction vertical to the geometric air inlet angle of the blade profile and is perpendicular to the SS_CAnd PP_CRespectively intersect at point S and point P, point S₁、S₂、P₁、P₂Respectively, movable points on the corresponding tangent line segments. The parameterized control line comprises a segment SS_CSegment SP and segment PP_CAnd (4) forming.

And 2, adjusting the design space of the leading edge profile. Moving the original leading edge point D to the point P along the line segment SP to obtain a new leading edge point D₁The design space of leading edge profile on suction side is adjusted to D₁S+SS_CThe design space of the leading edge profile on the pressure surface side is adjusted to D₁P+PP_C. From point D₁、S₁、S₂、S_CFour points are used as control points of the profile line on the side of the asymmetric leading edge suction surface, point D₁、P₁、P₂、P_CFour points are used as control points of the asymmetric leading edge pressure surface side molded line.

And 3, modifying the control point. Moving S in leading edge control points on suction side₁Dot sum S₂Point, and P in pressure surface side leading edge control point₁Point sum P₂The moving range of the point is limited to the control of each pointOn the line segment. Defining:

to be provided withFour variables are taken as design variables, and the change interval is (0, 1)]. By varying the values of the design variables, a corresponding set of leading edge control point combinations can be obtained.

And 4, generating a leading edge molded line. With newly obtained suction surface leading edge control point combination D₁、S₁、S₂、S_CGenerating an open cubic NURBS curve for the control point; at the same time, the newly obtained pressure surface leading edge control point combination D₁、P₁、P₂、P_CFor control points, a first three NURBS curve is generated. The curves are defined as follows:

calculating N from the Deboolean-Cocker recursion equation_i,3(u)：

And 5, judging whether the curvature is continuous or not. Calculating a new leading edge point D₁Two-side curvature, suction surface front edge and blade body connecting point S_CTwo-side curvature, pressure surface front edge and blade bodyConnection point P_CThe two-side curvature has the following calculation formula:

and (3) calculating the curvature error of the two sides within the range that the delta kappa/kappa is less than or equal to 0.5%, namely, considering that the curvature of the curve at the end point position is continuous to obtain a group of asymmetric leading edge profile design results, and repeating the step (3) if the curvature error is discontinuous.