Design Method of Dual-Duct Fan Hybrid Exhaust Test Device

Abstract

The present invention provides a design method for a dual-duct fan mixed exhaust test device, comprising the following steps: Step 1, determining the axial position of the outlet of the intermediate casing, the axial length of the mixed exhaust, and the radial height of the outlet of the mixed exhaust; Step 2, determining the shape of the mixed exhaust inner flow path based on the results of Step 1; Step 3, determining the shape of the inner-outer flow path according to the expansion ratio based on the shape of the mixed exhaust inner flow path in Step 2; Step 4, determining the shape of the mixed exhaust outer flow path and the mixing intersection point of the inner and outer ducts according to the outlet extension shape of the mode selection valve. The present invention can achieve the performance measurement of the dual-duct fan variable duct ratio test, improve the overall performance measurement of the fan component under variable duct ratio conditions, and has important guiding significance for the variable cycle whole machine test research.

Description

Technical Field

[0001] The present invention relates to the technical field of aero engines, and particularly to a design method for a dual-duct fan hybrid exhaust test device. Background Art

[0002] With the increasing demand of aircraft for power plants, it is urgent to improve the performance of turbofan engines. As one of the key components of turbofan engines, the performance of the fan directly affects the thrust-to-weight ratio and fuel consumption rate of the engine. To meet the power requirements of new aircraft, it is necessary to carry out the performance design and test verification of high-performance dual-duct fans. In the design of dual-duct fans, the design methods and processes have been basically mastered. After aerodynamic performance design, structural strength design and machining trial production, component tests are required for test verification. At present, in the multi-duct fan tests, there are many deficiencies in the existing test devices, and it is difficult to realize the variable duct ratio test with large flow regulation. Therefore, it is necessary to improve the design of the test rig.

[0003] Based on the above requirements, the fan component test rig needs to be adaptively designed for the outlet exhaust section. Conventional fans all adopt single-duct component tests, and only verify the performance of the combined test of the fan and the intermediate casing in the whole engine test. Moreover, the intermediate casing has a fixed duct ratio and does not perform flow regulation. However, the intermediate casing of a variable cycle engine needs to achieve flow variation to realize the function of duct ratio adjustment. The change of the outlet flow will have a great impact on the fan performance. To reduce the risk of the fan performance not meeting the standards in the whole engine test, the combined test of the fan component and the intermediate casing component is adopted in the component test to quantitatively verify the influence of the duct ratio change on the fan performance. To realize the variable duct ratio test and the performance test scheme design, a new type of hybrid exhaust structure is adopted for the exhaust section of the intermediate casing, which can not only ensure the fluidity of the large flow in the fan inner duct in the single-duct mode, but also ensure the performance test layout of the outer duct air flow in the dual-duct mode. Summary of the Invention

[0004] In view of this, the embodiments of the present specification provide a design method for a dual-duct fan hybrid exhaust test device to ensure that the designed dual-duct fan hybrid exhaust test device can effectively ensure the air flow fluidity of the fan when the duct ratio changes.

[0005] The embodiments of the present specification provide the following technical solutions: A design method for a dual-duct fan hybrid exhaust test device, including the following steps: Step 1, determine the outlet axial position of the intermediate casing, the axial length of the hybrid exhaust, and the outlet radial height of the hybrid exhaust; Step 2, determine the shape of the inner flow channel of the hybrid exhaust according to the results of Step 1; Step 3, determine the shape of the outer flow channel of the inner duct according to the expansion ratio based on the shape of the inner flow channel of the hybrid exhaust in Step 2; Step 4, determine the shape of the outer flow channel of the hybrid exhaust and the intersection point of the inner and outer ducts according to the outlet extension shape of the mode selection valve.

[0006] Further, Step 1 is specifically as follows: Add an extension section at the outlet of the intermediate casing, and the size of the extension section at the outlet of the intermediate casing is 50% to 100% of the radial height of the inner flow path outlet of the intermediate casing.

[0007] Further, Step 1 also includes: After determining the extension section at the outlet of the intermediate casing, determine the starting position of the mixed exhaust section, extend axially a set axial length L backward from the starting position of the mixed exhaust section to determine the axial position of the termination position of the mixed exhaust section, and determine the radial position of the termination position of the mixed exhaust section according to the height of the exhaust section at the outlet of the conventional fan tester, and determine the coordinates of the termination position of the mixed exhaust section.

[0008] Further, the coordinates of the starting position of the mixed exhaust section are (x1, y1), and the coordinates of the termination position of the mixed exhaust section are (x2, y2). Step 2 is specifically as follows: A cubic curve is used for smooth transition between the starting position and the termination position of the mixed exhaust section, and the control equation of the curve is y = ax 3 + bx 2 , where Based on the control equation of the curve, the flow path is discretized. According to the interval of l = (x2 - x1) / 100, the coordinates (x3, y3) of the discrete points are obtained, where

[0009] Further, Step 3 is specifically as follows: An expanding channel is adopted, and the value of the area expansion ratio k is 1.05 - 1.2. The geometric point coordinates A'(x4, y4), B'(x5, y5), and D'(x6, y6) of the outer flow path of the inner flow path are obtained by the area superposition method. The expression of the geometric points of the inner-outer flow path is:

[0010] Further, Step 4 is specifically as follows: The horizontal extension method is adopted for the outlet of the mode selection valve to obtain the outer flow path. The outer-outer flow path extends backward to the outer outlet, the inner-outer flow path extends backward and intersects with the inner-outer flow path, and the shape of the mixed exhaust outer flow path and the mixing intersection point of the inner and outer flows are determined.

[0011] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in the embodiments of this specification at least include: The present invention can realize the performance measurement of the dual-duct fan with variable duct ratio, improve the overall performance measurement of the fan component under the variable duct ratio working condition, and has important guiding significance for the experimental research of the variable cycle whole machine. Description of the Drawings

[0012] To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for use in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0013] Figure 1 It is a schematic diagram of the main parameters of the outlet mixed exhaust section design of the embodiment of the present invention;

[0014] Figure 2 It is a schematic flow diagram of the embodiment of the present invention. Detailed implementation manners

[0015] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0016] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0017] As Figure 1 and Figure 2 shown, in order to ensure the measurement of the aerodynamic parameters of the inner flow path outlet section of the dual-duct fan intermediate casing, an intermediate casing outlet extension section C is added. The intermediate casing outlet extension section C is (50% - 100%)h, where h is the radial height of the inner flow path outlet of the intermediate casing.

[0018] After determining the intermediate casing outlet extension section C, the starting position A of the mixed exhaust section is determined. After determining the starting point A, a set axial length L is extended backward to determine the axial position of the termination position B of the mixed exhaust section, and according to the height of the outlet exhaust section of the conventional fan tester, the radial position of the termination position B of the mixed exhaust section is determined, and then the coordinates of the termination position B of the mixed exhaust section are determined.

[0019] After determining the coordinates of point A(x1, y1) and point B(x2, y2), a cubic curve is used for smooth transition between point A(x1, y1) and point B(x2, y2). The control equation of the curve is as follows: y = ax 3 + bx 2 .

[0020] Where:

[0021] Based on the obtained control curve equation, the flow channel is discretized. According to the interval of l = (x2 - x1) / 100, the discrete point D(x3, y3) is obtained. Among them,

[0022] Based on the discrete points in the AB section, the geometric points of the outer wall surface are obtained by the area superposition method. Considering the thickening of the boundary layer and the blockage of the flow channel, an expanding channel is adopted, and the area expansion ratio is k. The expansion ratio is recommended to be selected from 1.05 to 1.2. Therefore, the geometric point coordinates of the outer flow channel of the inner flow path are A'(x4, y4), B'(x5, y5), and D'(x6, y6). The corresponding expressions of each point in the inner and outer flow paths are as follows:

[0023] x4 = x1

[0024] y4 = y1 + h;

[0025] x5 = x2

[0026]

[0027] x6 = x3

[0028]

[0029] The outer bypass flow path is obtained by horizontally extending the outer bypass of the intermediate casing. The outer bypass outer flow path extends backward from point F to F'. The inner bypass flow path extends backward from point E and intersects with the outer flow path of the inner flow path at point E', thereby determining the shape of the mixed exhaust outer flow path and the mixing intersection point of the inner and outer bypasses.

[0030] Through the design method of the embodiment of the present invention, the geometric shape of the outlet exhaust section of the combined test of the fan component and the intermediate casing of a variable cycle turbofan engine can be obtained. Using this exhaust section geometry for structural design can achieve the performance measurement of the double bypass fan variable bypass ratio test, improve the overall performance measurement of the fan component under variable bypass ratio conditions, and has important guiding significance for the research of the variable cycle engine test.

[0031] The embodiment of the present invention performs polynomial curve control on the inner bypass exhaust section of the fan, and through the equal-proportion expansion of the flow path geometry area, effectively ensures the air flow through the fan when the bypass ratio changes. The multi-bypass fan exhaust section designed by this method can ensure that the fan has high flow-through performance under all working conditions, reduce the error generation in the overall performance measurement of the fan, obtain the combined performance of the fan and the intermediate casing, and reduce the risk of the aeroengine overall test.

[0032] The above is only a specific embodiment of the present invention and cannot be used to limit the scope of the invention implementation. Therefore, the replacement of equivalent components or the equivalent changes and modifications made according to the protection scope of the present invention patent should still fall within the scope covered by this patent. In addition, the technical features in the present invention, between technical features, between technical features and technical solutions, and between technical solutions can be freely combined and used.

Claims

1. A design method for a dual-ducted fan hybrid exhaust test device, characterized in that, It includes the following steps: Step 1: Determine the axial position of the outlet of the intermediate casing, the axial length of the mixed exhaust, and the radial height of the outlet of the mixed exhaust; Step 2: Determine the shape of the mixed exhaust inner flow path based on the results of Step 1; Step 3: Determine the shape of the inner-outer flow path based on the expansion ratio according to the shape of the mixed exhaust inner flow path in Step 2; Step 4: Determine the shape of the mixed exhaust outer flow path and the mixing intersection of the inner and outer flows based on the outlet extension shape of the mode selection valve; Specifically, Step 1 is as follows: Add an extension section to the outlet of the intermediate casing, and the size of the extension section at the outlet of the intermediate casing is 50% to 100% of the radial height of the inner outlet of the intermediate casing; Step 1 further includes: After determining the extension section at the outlet of the intermediate casing, determine the starting position of the mixed exhaust section, extend backward by a set axial length L from the starting position of the mixed exhaust section to determine the axial position of the termination position of the mixed exhaust section, and determine the radial position of the termination position of the mixed exhaust section according to the height of the outlet exhaust section of the conventional fan tester, and determine the coordinates of the termination position of the mixed exhaust section; The coordinates of the starting position of the mixed exhaust section are ( ), and the coordinates of the ending position of the mixed exhaust section are ( ). The specific content of the second step is as follows: A cubic curve is used for smooth transition between the starting position and the ending position of the mixed exhaust section, and the control equation of the curve is , where , ; Discretize the flow channel based on the control equation of the curve. According to discontinuity, the coordinates of the discrete points are obtained ([[]] ), where ; Specifically, Step 3 is as follows: An expansion-type channel is adopted, and the value of the area expansion ratio k is 1.05 - 1.

2. The geometric point coordinates A'( )、B'( ) and D'( ) of the outer flow path of the inner flow path are obtained by area method superposition. The expression of the geometric points of the inner and outer flow paths is as follows: ; ; , where h is the radial height at the inner flow path outlet of the intermediate casing.

2. The design method for a dual-ducted fan hybrid exhaust test device according to claim 1, characterized in that, Specifically, Step 4 is as follows: Adopt a horizontal extension method for the outlet of the mode selection valve to obtain the outer flow path. The outer flow path of the outer flow extends backward to the outer outlet, and the inner flow path of the outer flow extends backward and intersects with the inner-outer flow path of the inner flow to determine the shape of the mixed exhaust outer flow path and the mixing intersection of the inner and outer flows.

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