A scaled-down simulation method for intake secondary flow system based on equal flow ratio

Abstract

This invention discloses a scaled-down simulation method for secondary flow systems in air intakes based on equal flow ratios, belonging to the field of scaled-down simulation technology for wind tunnel testing. It solves the problem that traditional scaled-down simulation methods in the prior art struggle to provide applicable orifice scaling principles for secondary flow systems in aircraft air intakes. This invention obtains the total flow rate of the secondary flow system in the scaled-down model by numerically simulating a full-size aircraft model to acquire the main flow rate and incoming aerodynamic parameters at the secondary flow paths in the full-size air intake. It then selects the basic flow path structure parameters and orifice distribution method for the scaled-down model; establishes a mathematical model to obtain the actual flow rate of the basic flow path; and distributes the basic flow paths according to their number and layout parameters within the secondary flow region defined in the scaled-down model using the selected distribution method, obtaining the orifice system distribution result, and thus the final design result of the secondary flow system. This invention can reflect the actual effect of the secondary flow system and can be applied to scaled-down simulation of secondary flow systems.

Description

Technical Field

[0001] The invention relates to a scaled-down simulation method for an intake duct secondary flow system, and in particular to a scaled-down simulation method for an intake duct secondary flow system based on equal flow ratio, and belongs to the technical field of scaled-down simulation of wind tunnel tests. Background Art

[0002] The altitude range, speed range, stealth, and comprehensive combat capability of modern aircraft have made great progress. The technological advancement and complexity of the inlet design are also increasing day by day. In order to make the airflow entering the engine have higher total pressure recovery performance and lower flow field distortion, it is often necessary to use the inlet secondary flow system to improve the performance of the inlet by introducing or removing a small part of the airflow. The working principle and working mode of the inlet secondary flow system are also different under different flight speed conditions or engine operating conditions.

[0003] The scaling simulation method in the prior art discloses keeping the opening ratio of the test model and the ratio of the hole depth to the hole diameter as constants, but the scaling principle of the leakage holes and hole depth of the model and other test components is not introduced. In addition, there are theoretically infinite groups of scaling methods that keep the opening ratio of the model and the ratio of the hole depth to the hole diameter as constants. It is still unknown what ratio of leakage hole scaling simulation is applicable.

[0004] Therefore, a scaling simulation method suitable for the secondary flow system of the aircraft inlet duct is needed, which has a clear scaling principle for the leakage holes. Summary of the invention

[0005] A brief overview of the present invention is provided below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0006] In view of this, in order to solve the problem that traditional scaling simulation methods in the prior art are difficult to provide a scaling principle for leakage holes in the secondary flow system of an aircraft inlet duct, the present invention provides a scaling simulation method for the secondary flow system of an inlet duct based on equal flow ratio.

[0007] The technical solution is as follows: A method for simulating a scaled-down intake secondary flow system based on equal flow ratios, comprising the following steps:

[0008] S1. By numerically simulating a full-scale aircraft model, the aerodynamic parameters of the mainstream flow and the secondary flow path of the full-scale inlet are obtained;

[0009] S2. Determine the primary and secondary flow ratios of a full-scale aircraft model using numerical simulation methods or as specified by the designer;

[0010] S3. Determine the scaling parameters of the scaled model according to the requirements of the inlet wind tunnel test, and obtain the mainstream flow of the scaled model using a numerical simulation method;

[0011] S4. According to the scaling parameters of the scaled model, the total flow rate of the scaled model secondary flow system is obtained based on the same primary and secondary flow rate ratio of the full-size aircraft model and the scaled model;

[0012] S5. According to the design requirements of the full-size aircraft model, select the basic flow path structure parameters and the hole distribution method in the same opening area of ​​the scaled model;

[0013] Specifically: the layout parameters are used to describe the distribution of the holes, and the layout parameters include the flow direction distance x of the leakage holes and the span direction distance y of the leakage holes;

[0014] S6. Introduce the incoming flow aerodynamic parameters and the basic flow path structural parameters to establish a mathematical model, combine the influencing factors obtained by the layout parameters to obtain the basic flow path flow coefficient, and obtain the actual flow of the basic flow path according to the designed basic flow path flow area;

[0015] S7. According to the total flow of the secondary flow system of the scaled model, the number of basic flow paths opened is obtained;

[0016] S8. Use the selected distribution method to distribute the basic flow paths in the secondary flow area set by the scaled model according to their opening quantity and layout parameters, obtain the porous system distribution result, and then obtain the final secondary flow system design result.

[0017] Furthermore, in S1, the incoming flow aerodynamic parameters include the local Mach number , local static pressure P of the secondary flow system, local total temperature T0 of the secondary flow system, inlet and outlet pressure ratio of the secondary flow system and boundary layer conditions in front of the secondary flow system inlet.

[0018] Furthermore, in S2, the ratio of the primary and secondary flow rates of the full-scale aircraft model is It is expressed as:

[0019] ;

[0020] in, is the total flow rate of the secondary flow system of the full-scale aircraft model, This is the mainstream flow for a full-scale aircraft model.

[0021] Furthermore, in said S4, the total flow of the scaled model secondary flow system It is expressed as:

[0022] ;

[0023] in, This is the mainstream flow of the scaled model.

[0024] Furthermore, in S5, the basic flow path structural parameters include the wall thickness h of the scaled model secondary flow opening area, the flow path inclination angle of a single basic flow path of the scaled model secondary flow system, and the flow path inclination angle h of the single basic flow path of the scaled model secondary flow system. and the diameter of the secondary flow path ;

[0025] Flow path inclination of a single basic flow path of the secondary flow system of the scaled model The value range is 20° to 90°.

[0026] Furthermore, in S6, the mathematical model It is expressed as:

[0027] ;

[0028] in, is a multivariate function;

[0029] Basic flow coefficient It is expressed as:

[0030] ;

[0031] Among them, K is the layout parameter influencing factor, K=f(x, y), are the polynomial coefficients obtained by fitting, For mathematical models The 0 to 3 order sub-terms obtained by the interaction of the influencing factors in , j is the total number of polynomial terms;

[0032] Actual flow rate of basic flow path It is expressed as:

[0033] ;

[0034] ;

[0035] in, is the theoretical flow rate of the basic flow path, A is the flow area of ​​the basic flow path, is the air gas constant, , is the specific heat ratio, for air, =1.4.

[0036] Furthermore, in S7, the number of basic flow paths opened is It is expressed as:

[0037] .

[0038] The beneficial effects of the present invention are as follows: the present invention can provide a wind tunnel model secondary flow system scaled-down design result that can reflect the actual effect of the secondary flow system based on the actual secondary flow system design of the aircraft and in combination with the requirements of the wind tunnel test, so that the design of the wind tunnel model secondary flow system can be consistent with the effect of the full-size aircraft model and meet the needs of secondary flow system performance evaluation; the present invention can be applied to secondary flow systems of various forms such as slit type and circular hole type. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0040] Figure 1 The figure is a flow chart of a scaled-down simulation method for an intake secondary flow system based on equal flow ratio. DETAILED DESCRIPTION

[0041] In order to make the technical solutions and advantages of the embodiments of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0042] refer to Figure 1 The present embodiment is described in detail, a method for simulating a scaled-down intake secondary flow system based on equal flow ratio, specifically comprising the following steps:

[0043] S1. By numerically simulating a full-scale aircraft model, the aerodynamic parameters of the mainstream flow and the secondary flow path of the full-scale inlet are obtained;

[0044] S2. Determine the primary and secondary flow ratios of a full-scale aircraft model using numerical simulation methods or as specified by the designer;

[0045] S3. Determine the scaling parameters of the scaled model according to the requirements of the inlet wind tunnel test, and obtain the mainstream flow of the scaled model using a numerical simulation method;

[0046] S4. According to the scaling parameters of the scaled model, the total flow rate of the scaled model secondary flow system is obtained based on the same primary and secondary flow rate ratio of the full-size aircraft model and the scaled model;

[0047] S5. According to the design requirements of the full-size aircraft model, select the basic flow path structure parameters and the hole distribution method in the same opening area of ​​the scaled model;

[0048] Specifically: the layout parameters are used to describe the distribution mode between the holes, and the layout parameters include the flow direction distance x of the leakage holes and the span direction distance y of the leakage holes;

[0049] S6. Introduce the incoming flow aerodynamic parameters and the basic flow path structural parameters to establish a mathematical model, combine the influencing factors obtained by the layout parameters to obtain the basic flow path flow coefficient, and obtain the actual flow of the basic flow path according to the designed basic flow path flow area;

[0050] S7. According to the total flow of the secondary flow system of the scaled model, the number of basic flow paths opened is obtained;

[0051] S8. Use the selected distribution method to distribute the basic flow paths in the secondary flow area set by the scaled model according to their opening quantity and layout parameters, obtain the porous system distribution result, and then obtain the final secondary flow system design result.

[0052] Furthermore, in S1, the incoming flow aerodynamic parameters include the local Mach number That is, the local Mach number of the leakage system, the local static pressure P of the secondary flow system, the local total temperature T0 of the secondary flow system, and the inlet and outlet pressure ratio of the secondary flow system That is, the pressure ratio of the inlet and outlet of the leak hole and the boundary layer conditions in front of the secondary flow system inlet.

[0053] Furthermore, in S2, the ratio of the primary and secondary flow rates of the full-scale aircraft model is It is expressed as:

[0054] ;

[0055] in, is the total flow rate of the secondary flow system of the full-scale aircraft model, This is the mainstream flow for a full-scale aircraft model.

[0056] Furthermore, in said S4, the total flow of the scaled model secondary flow system It is expressed as:

[0057] ;

[0058] in, is the mainstream flow of the scaled model, obtained by numerical simulation method.

[0059] Furthermore, in S5, the basic flow path structural parameters include the wall thickness h of the scaled model secondary flow opening area, i.e., the thickness of the leakage hole, the flow path inclination angle of a single basic flow path of the scaled model secondary flow system, That is, the angle between the leakage hole and the normal line of the model wall and the diameter of the hole-shaped secondary flow path That is, the diameter of a single leakage hole;

[0060] Flow path inclination of a single basic flow path of the secondary flow system of the scaled model The value range is 20° to 90°.

[0061] Furthermore, in S6, the mathematical model It is expressed as:

[0062] ;

[0063] in, is a multivariate function;

[0064] Basic flow coefficient It is expressed as:

[0065] ;

[0066] Among them, K is the layout parameter influencing factor, K=f(x, y), are the polynomial coefficients obtained by fitting, For mathematical models The 0 to 3 order sub-terms obtained by the interaction of the influencing factors in , j is the total number of polynomial terms;

[0067] Actual flow rate of basic flow path It is expressed as:

[0068] ;

[0069] ;

[0070] in, is the theoretical flow rate of the basic flow path, A is the flow area of ​​the basic flow path, is the air gas constant, , is the specific heat ratio, for air, .

[0071] Furthermore, in S7, the number of basic flow paths opened is It is expressed as:

[0072] .

[0073] Specifically, the final design result of the secondary flow system is obtained, that is, under the condition of given incoming flow aerodynamic parameters, the flow path inclination angle of a single basic flow path of the secondary flow system of the scaled model can be given. , the wall thickness h of the secondary flow area of ​​the scaled model, the diameter of the pore secondary flow path , the flow distance x of the leakage hole, the span distance y of the leakage hole and the number of holes opened The porous system release demand is the target scaled-down model of the secondary flow system total flow m.

[0074] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

Claims

1. A method for simulating the scaled-down intake secondary flow system based on equal flow ratio, characterized in that: The following steps are involved: S1. By numerically simulating a full-scale aircraft model, the aerodynamic parameters of the mainstream flow and the secondary flow path of the full-scale inlet are obtained; S2. Determine the primary and secondary flow ratios of a full-scale aircraft model using numerical simulation methods or as specified by the designer; S3. Determine the scaling parameters of the scaled model according to the requirements of the inlet wind tunnel test, and obtain the mainstream flow of the scaled model using a numerical simulation method; S4. According to the scaling parameters of the scaled model, the total flow rate of the scaled model secondary flow system is obtained based on the same primary and secondary flow rate ratio of the full-size aircraft model and the scaled model; S5. According to the design requirements of the full-size aircraft model, select the basic flow path structure parameters and the hole distribution method in the same opening area of ​​the scaled model; Specifically: the layout parameters are used to describe the distribution of the holes, and the layout parameters include the flow direction distance x of the leakage holes and the span direction distance y of the leakage holes; S6. Introduce the incoming flow aerodynamic parameters and the basic flow path structural parameters to establish a mathematical model, combine the influencing factors obtained by the layout parameters to obtain the basic flow path flow coefficient, and obtain the actual flow of the basic flow path according to the designed basic flow path flow area; S7. According to the total flow of the secondary flow system of the scaled model and the actual flow of the basic flow path, the number of basic flow paths opened is obtained; S8. Using the selected distribution method, distribute the basic flow paths in the secondary flow area set by the scaled model according to the number of openings and layout parameters, obtain the porous system distribution result, and then obtain the final design result of the secondary flow system; In S6, the basic flow path flow coefficient C is expressed as: Among them, K is the layout parameter influencing factor, K = f (x, y), a i are the polynomial coefficients obtained by fitting, I i are the 0th to 3rd order sub-terms obtained by the interaction of various influencing factors in the mathematical model, and j is the total number of polynomial terms; Actual flow rate of basic flow path m r It is expressed as: m r =m i *C Among them, m i is the theoretical flow rate of the basic flow path, A is the flow area of ​​the basic flow path, R air is the air gas constant, R air =287.06J / (Kg·K), γ is the specific heat ratio, for air, γ=1.4, T0 is the local total temperature of the secondary flow system, and P is the local static pressure of the secondary flow system.

2. The method for simulating the scaled-down intake secondary flow system based on equal flow ratio according to claim 1, characterized in that: In S1, the incoming flow aerodynamic parameters include the local Mach number Ma, the local static pressure P of the secondary flow system, the local total temperature T0 of the secondary flow system, the inlet and outlet pressure ratio NPR of the secondary flow system, and the boundary layer conditions in front of the inlet of the secondary flow system.

3. The method for simulating the scaled-down intake secondary flow system based on equal flow ratio according to claim 2, characterized in that: In S2, the primary and secondary flow ratio Φ of the full-scale aircraft model is expressed as: Among them, m 全 is the total flow rate of the secondary flow system of the full-scale aircraft model, M 全 This is the mainstream flow for a full-scale aircraft model.

4. The method for simulating the scaled-down intake secondary flow system based on equal flow ratio according to claim 3, characterized in that: In S4, the total flow rate m of the scaled model secondary flow system is expressed as: m=Φ*M Where M is the mainstream flow of the scaled model.

5. The method for simulating the scaled-down intake secondary flow system based on equal flow ratio according to claim 4, characterized in that: In said S5, the basic flow path structural parameters include the wall thickness h of the scaled model secondary flow opening area, the flow path inclination angle α of a single basic flow path of the scaled model secondary flow system, and the diameter D of the hole-shaped secondary flow path; The flow path inclination angle α of a single basic flow path of the scaled model secondary flow system ranges from 20° to 90°.

6. The method for simulating the scaled-down intake secondary flow system based on equal flow ratio according to claim 5, characterized in that: In S6, the mathematical model C′ is expressed as: C′=f(Ma,NPR,D,α,h) Where f is a multivariate function.

7. The method for simulating the scaled-down intake secondary flow system based on equal flow ratio according to claim 6, characterized in that: In S7, the number a′ of the basic flow paths is expressed as:

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