CN-115600341-B - Design method of front duct flow path of variable cycle engine

Abstract

The application provides a design method of a front duct flow path of a variable cycle engine, which is characterized in that the design method of the front duct flow path is realized by controlling the change rule of the typical cross-section area of the front duct along the path, and the reasonable outlet valve characteristic is obtained by reducing the internal flow loss of the front duct and realizing the reasonable front duct ejector valve characteristic on the premise of meeting the index requirement of the outlet area of the front duct and ensuring that the blocking phenomenon does not occur in the front duct, and the reasonable front duct flow path is realized by reversely calculating the radial length of the typical cross-section according to the typical cross-section pneumatic area and the inner wall surface flow path, so that the change rule of the cross-section area of the front duct along the path is determined, and the reasonable front duct along the path can be formed, the flow loss in the front duct and the idle stroke length of a front duct valve are reduced.

Inventors

• LI XIAOQING

Assignees

• 中国航发沈阳发动机研究所

Dates

Publication Date

20260505

Application Date

20221027

Claims (1)

1. 1. A method of designing a front bypass flow path of a variable cycle engine, comprising: Taking the included angle alpha between the inner wall surface of the front duct and the axis of the engine to be 30-60 degrees; Calculating to obtain a minimum flow area A in the front duct according to the maximum flow index of the front duct and the maximum Mach number allowed in the front duct; taking the aerodynamic area C=max (A, B) of the section of the maximum thickness position of the support plate, wherein B is the index requirement of the aerodynamic area adjusting range of the front duct outlet; the front duct outlet aerodynamic area D is determined, satisfying B is more than or equal to D is more than or equal to C; Determining the leaf shape and the number of the support plates of the front duct and the positions of the support plates in the front duct according to the strength requirement, and further calculating to obtain the distance R support plate max1 from the intersection point of the maximum thickness position of the support plates and the inner wall surface of the front duct to the axis of the engine along the vertical line, and the distance M support plate max1 from the meridian of the aerodynamic section to the axis of the engine; based on C, R support plates max1 and M support plates max1, calculating to obtain a distance R support plate max2 from the intersection point of the maximum thickness position of the support plate and the outer wall surface of the front culvert to the axis of the engine along the vertical line, and a distance M support plate max2 from the meridian of the aerodynamic section to the axis of the engine along the meridian of the aerodynamic section; calculating to obtain the radial length of the pneumatic section at the maximum thickness position of the support plate Further determining the intersection point of the maximum thickness position of the support plate and the outer wall surface of the front duct; based on the D, calculating to obtain the distance R2 between the intersection point of the valve and the outer wall surface of the front duct and the axis of the engine along the vertical line, and the distance M2 between the intersection point of the valve and the outer wall surface of the front duct and the axis of the engine along the meridian of the pneumatic section; Calculating to obtain the length K=M2-M1 of the meridian of the pneumatic section of the front duct outlet, and further obtaining the intersection point of the pneumatic section of the front duct outlet and the outer wall surface of the front duct, wherein M1 is the distance from the intersection point of the pneumatic section and the inner wall surface of the front duct to the axis of the engine along the meridian of the pneumatic section; And determining the outer wall surface of the front duct based on the intersection point of the maximum thickness position of the support plate and the outer wall surface of the front duct and the intersection point of the pneumatic section of the outlet of the front duct and the outer wall surface of the front duct.

Description

Design method of front duct flow path of variable cycle engine Technical Field The application belongs to the technical field of design of front duct flow paths of variable cycle engines, and particularly relates to a design method of a front duct flow path of a variable cycle engine. Background Compared with a conventional cycle engine, the variable cycle engine is provided with the front duct between the core engine driving fan, the high-pressure air compressor and the outer duct, a plurality of support plates are circumferentially arranged in the front duct, and valves are arranged at the outlet positions of the front duct, so that the engine can be efficiently adapted to different flight states by controlling the opening of the valves, adjusting the air-entraining amount of the driving fan and the high-pressure air compressor to the outer duct, thereby changing the duct ratio. At present, when designing the front duct of a variable cycle engine, the structural design of a valve arranged at the outlet part of the front duct and the strength and the function of a valve adjusting mechanism of the front duct are concerned, the pneumatic performance of the front duct is concerned less, and the situations that the front duct is large in loss, the idle stroke length of the valve is overlong and the valve characteristics are unreasonable are caused due to improper design of a front duct flow path. The present application has been made in view of the above-described technical drawbacks. It should be noted that the above disclosure of the background art is only for aiding in understanding the inventive concept and technical solution of the present application, which is not necessarily prior art to the present patent application, and should not be used for evaluating the novelty and creativity of the present application in the case where no clear evidence indicates that the above content has been disclosed at the filing date of the present application. Disclosure of Invention It is an object of the present application to provide a method of designing a front bypass flow path for a variable cycle engine that overcomes or mitigates at least one of the known technical drawbacks. The technical scheme of the application is as follows: a method of designing a front bypass flow path of a variable cycle engine, comprising: Taking the included angle alpha between the inner wall surface of the front duct and the axis of the engine to be 30-60 degrees; Calculating to obtain a minimum flow area A in the front duct according to the maximum flow index of the front duct and the maximum Mach number allowed in the front duct; taking the aerodynamic area C=max (A, B) of the section of the maximum thickness position of the support plate, wherein B is the index requirement of the aerodynamic area adjusting range of the front duct outlet; the front duct outlet aerodynamic area D is determined, satisfying B is more than or equal to D is more than or equal to C; Determining the leaf shape and the number of the support plates of the front duct and the positions of the support plates in the front duct according to the strength requirement to obtain the distances R support plate inlets 1 and R support plate outlets 1 from the intersection points of the front edge and the tail edge of the support plates and the inner wall surface of the front duct to the axis of the engine along the vertical line, and the distances M support plate inlets 1 and M support plate outlets 1 from the meridian of the pneumatic section to the axis of the engine; according to the support plate blade shape, the R support plate inlet 1, the R support plate outlet 1, the M support plate inlet 1 and the M support plate outlet 1, the distance R support plate max1 between the intersection point of the support plate maximum thickness position and the inner wall surface of the front culvert and the engine axis along the vertical line is calculated, and the distance M support plate max1 between the meridian of the pneumatic section and the engine axis is calculated; based on C, R support plates max1 and M support plates max1, calculating to obtain a distance R support plate max2 from the intersection point of the maximum thickness position of the support plate and the outer wall surface of the front culvert to the axis of the engine along the vertical line, and a distance M support plate max2 from the meridian of the aerodynamic section to the axis of the engine along the meridian of the aerodynamic section; Calculating to obtain the meridian length H=the maximum thickness position of the support plate and the maximum thickness position of the support plate max2-M support plate max1, and further determining the intersection point of the maximum thickness position of the support plate and the outer wall surface of the front duct; based on the D, calculating to obtain the distance R2 between the intersection point of the valve and the outer wall surface of the front duct and t