Design method of inward rotation type air inlet channel based on flow field self-adjustment

Abstract

The invention discloses a flow field self-adjustment-based inward rotation type air inlet channel design method which comprises the following steps: S1, generating an air inlet channel profile scheme under a given design point incoming flow condition; s2, the molded surface of the air inlet channel is modified under the incoming flow condition of a given starting point, and the molded surface of the air inlet channel with a groove is formed; s3, generating an air inlet channel reference molded surface based on pneumatics; s4, on the basis of the reference molded surface of the air inlet channel, the self-adaptive adjusting capacity of the pneumatic throat channel is checked within the operation range; s5, on the basis of the air inlet channel reference molded surface designed and completed in the step S4, generating the inward rotation type air inlet channel with the pneumatic self-adaptive adjusting capacity; and S6, iteration and optimization are carried out on the inward rotation type air inlet channel formed in the step S5. The flow channel area at the throat of the air inlet channel is controlled through the virtual wall face formed by the separation area, then wide-area operation of the air inlet channel is achieved, and the suction-free air inlet channel with the rectangular section and the fixed geometry and capable of operating within the Mach number range of 3-7 is designed.

Description

Technical Field

[0001] The present application relates to the field of ramjet internal flow aerodynamics, and in particular to a method for designing an inward-rotating air inlet based on flow field self-regulation. Background Art

[0002] In order to achieve stable operation of the air inlet over a wide speed range, the flow control methods such as suction and discharge widely used in aircraft air inlets face serious problems such as narrow application range and risk of thermal damage to pores in high-speed environments; geometric adjustment methods have difficulties such as high-temperature dynamic seals / immature materials and high risk of thermal damage to gaps. Developing wide-range air inlets with fixed geometric configurations and avoiding solutions such as geometric adjustment mechanisms and slit suction that affect structural strength under high temperature conditions are of great significance for achieving long-duration, large-load, and repeatable high-speed flights. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a design method for an inward-turning air inlet based on flow field self-regulation. The present invention designs the inward-turning air inlet profile and uses the aerodynamic throat principle to achieve adaptive adjustment of the inward-turning air inlet under wide-range conditions, broadens the working range of the inward-turning air inlet, and avoids structural and thermal protection problems caused by technical means such as geometric adjustment and suction. The design method does not include an inward-turning air inlet with three-dimensional curved surface features.

[0004] The present invention provides a method for designing an inner-rotating air intake based on flow field self-regulation, which is characterized by comprising the following steps:

[0005] S1, under the condition of the incoming flow at a given design point (generally exceeding Mach number 5), the external compression surface and lip are designed by two-dimensional shock wave theory to generate the inlet profile so that the external compression shock wave I and lip shock wave I meet the shock wave contact requirements;

[0006] S2, under the condition of the incoming flow at a given starting point (generally less than or equal to Mach number 4), the inlet profile generated by S1 is calculated by two-dimensional shock wave theory, and the generated external compression shock wave II and lip shock wave II are generated. Since the incoming flow Mach number at the starting point is lower than the incoming flow Mach number at the design point, the external compression shock wave II is located outside the lip, and the lip shock wave II is located upstream of the lip shock wave I. The inlet profile is modified upstream of the lip shock wave incident point, and grooves are set on the inlet profile to form an inlet profile with grooves;

[0007] S3, under the given starting point flow condition, the inlet profile with grooves formed by S2 is numerically simulated and calculated. Under the starting point condition, the lip shock wave II is incident on the wall surface, generating a separation zone, extracting the separation zone boundary of the separation zone, and replacing the inlet profile with the separation zone boundary to generate an aerodynamic-based inlet reference profile;

[0008] S4, for the aerodynamic-based inlet reference profile formed by S3, numerical simulation calculations are carried out within the operating range to test the aerodynamic throat adaptive adjustment capability according to the flow field characteristics;

[0009] Under the starting point conditions, there is almost no separation zone, ensuring that the inlet can start normally at a lower incoming flow speed; as the incoming flow Mach number increases, the size of the separation zone will increase accordingly, squeezing the mainstream area outside the separation zone, and the boundary of the separation zone will equivalently form an aerodynamic wall, which will compress the airflow in the mainstream area more strongly. If a large amount of overflow is generated in the inlet within the design operating range, or a large-amplitude oscillation occurs in the separation zone, return to S3, modify the aerodynamic-based inlet reference profile, and expand the inlet flow area;

[0010] S5, the aerodynamic-based inlet reference profile designed in S4 is rotated along the symmetry axis to form an axisymmetric inner cone inlet. The inlet airflow capture entrance shape is given according to the aircraft shape requirements. Under the design point flow condition, the inner cone inlet will also form an external compression shock wave I. Streamline tracking is performed from the inlet entrance to form a series of streamlines, and the streamlines downstream of the external compression shock wave I are combined to form an inner rotating inlet with aerodynamic self-regulation capability.

[0011] S6, perform CFD calculations on the inward-turning air inlet formed in S5, evaluate the performance parameters of the air inlet under various operating conditions based on the calculation results, and compare them with the performance parameter index requirements. If the index requirements are not met, return to S3 to modify the aerodynamic-based air inlet reference surface; if the index requirements are met, complete the design of the inward-turning air inlet based on flow field self-regulation.

[0012] Furthermore, in S1, the external compression shock wave I is a plurality of oblique shock waves, a curvilinear shock wave, or a combination of a curvilinear shock wave and an oblique shock wave.

[0013] Furthermore, in S5, the shape of the inner cone air inlet can be rectangular, elliptical or circular.

[0014] Furthermore, in S6, the performance parameters of the inlet duct include the outlet total pressure recovery coefficient and the outlet Mach number.

[0015] Beneficial effects of the present invention:

[0016] The present invention utilizes the characteristic of the separation zone that adaptively adjusts as the incoming flow conditions change, and proposes the "aerodynamic throat" principle, that is, by reasonably designing the shape of the inlet wall, the "virtual wall" formed by the separation zone is used to control the flow area at the inlet throat, thereby achieving wide-range operation of the inlet. A rectangular cross-section, fixed geometry, non-suction inlet is designed that can operate in the Mach number range of 3-7, providing a scientific basis for the refined design of fixed geometry, non-suction, wide-speed range rotary inlets. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the profile of the air inlet under the design point flow condition in Example S1 of the present invention;

[0018] Figure 2 Schematic diagram of the inlet profile and shock wave under the starting point inflow condition in Example S2 of the present invention;

[0019] Figure 3 Schematic diagram of the profile of the inlet duct with grooves under the starting point flow condition in Example S2 of the present invention;

[0020] Figure 4 Schematic diagram of the flow field of the inlet duct with grooves under the starting point flow condition in Example S3 of the present invention;

[0021] Figure 5 Schematic diagram of an air intake duct reference profile based on aerodynamics in Example S3 of the present invention;

[0022] Figure 6 is the numerical simulation calculation result of the air inlet duct reference profile in Example S4 of the present invention;

[0023] Figure 7 Schematic diagram of the design of the inner-rotating air intake in Example S4 of the present invention;

[0024] Figure 8 The inner rotating air inlet designed in Example S5 of the present invention;

[0025] In the figure, 1. external compression surface, 2. lip, 3. external compression shock wave I, 4. lip shock wave I, 5. external compression shock wave II, 6. lip shock wave II, 7. separation zone, 8. separation zone boundary, 9. aerodynamic-based inlet reference profile, 10. mainstream area, 21. inner cone inlet, 22. inlet airflow capture entrance shape, 23. streamline, 24. inward-turning inlet. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described below in conjunction with the accompanying drawings and embodiments.

[0027] Example 1

[0028] In Example 1, the design point Mach number of the inward-turning inlet is 6, and the starting point Mach number is 3; the performance index requires that at the design point, the outlet total pressure recovery coefficient is greater than 0.4 and the outlet Mach number is less than 3.

[0029] The present invention provides a method for designing an inner-rotating air intake based on flow field self-regulation, which is characterized by comprising the following steps:

[0030] S1, at a given design point, under the condition of Mach number 6, the outer compression surface 1 and lip 2 are designed by two-dimensional shock wave theory to generate the following Figure 1 The inlet profile shown makes the external compression shock wave Ⅰ3 and the lip shock wave Ⅰ4 meet the shock wave contact requirement;

[0031] S2, under the condition of Mach number 3 inflow at a given starting point, the inlet profile generated by S1 is calculated by two-dimensional shock wave theory, and the generated external compression shock wave Ⅱ5 and lip shock wave Ⅱ6 are as follows: Figure 2 As shown in FIG. 1 , since the incoming flow Mach number at the starting point is lower than the incoming flow Mach number at the design point, the external compression shock wave II5 is located outside the lip 2, and the lip shock wave II6 is located upstream of the lip shock wave I4. The inlet profile is modified upstream of the lip shock wave incident point, and a groove is set on the inlet profile. The groove depth is equal to the boundary layer thickness at the groove, forming an inlet profile with a groove, as shown in FIG. Figure 3 As shown;

[0032] S3, at a given starting point and Mach number 3.5 inflow conditions, the inlet profile with grooves formed by S2 is numerically simulated. Under the starting point conditions, the lip shock wave II 6 enters the wall surface, generating a separation zone 7, such as Figure 4 As shown, the separation zone boundary 8 of the separation zone 7 is extracted, and the separation zone boundary 8 is used to replace the air intake duct profile to generate an air intake duct reference profile 9 based on aerodynamics, as shown in FIG. Figure 5 shown.

[0033] S4, for the aerodynamic-based inlet duct reference profile 9 formed by S3, numerical simulation calculations are carried out in the range of Mach number 3-7, and its aerodynamic throat adaptive adjustment ability is tested according to the flow field characteristics; the numerical simulation calculations of the aerodynamic-based inlet duct reference profile are as follows Figure 6 As shown;

[0034] Under the inflow condition of Mach number 3 at the starting point, almost no separation zone is generated, ensuring that the air inlet can start normally at a lower inflow speed; with the increase of the inflow Mach number, under the inflow condition of Mach number 6 at the design point, an obvious separation zone 7 appears, and the size of the separation zone 7 will increase accordingly, squeezing the mainstream area 10 outside the separation zone, and the boundary of the separation zone is equivalent to forming an aerodynamic wall surface, which compresses the airflow of the mainstream area 10 more strongly; if a large amount of overflow is generated in the air inlet within the design operating range, or a large-amplitude oscillation is generated in the separation zone, then return to S3, modify the aerodynamic-based air inlet reference profile 9, and expand the air inlet flow area; if the requirements are met, enter S5;

[0035] S5, the aerodynamically designed air intake duct reference profile 9 in S4 is rotated along the symmetry axis to form an axisymmetric inner cone air intake duct 21, such as Figure 7As shown, according to the requirements of the aircraft shape, the airflow capture entrance shape 22 of the inlet is given. Under the design point flow condition, the inner cone inlet will also form an external compression shock wave Ⅰ3. Streamline tracking is performed from the inlet entrance 22 to form a series of streamlines. The streamlines 23 downstream of the external compression shock wave Ⅰ3 are combined to form an inner rotating inlet 24 with aerodynamic self-regulation capability. The inner rotating inlet designed in this embodiment is as shown in FIG. Figure 8 As shown;

[0036] S6, CFD calculation is performed on the inner-rotating air inlet 24 formed in S5, and the performance parameters of the air inlet under various operating conditions are evaluated according to the calculation results, and compared with the performance parameter index requirements. If the index requirements are not met, return to S3 to modify the aerodynamic-based air inlet reference profile 9; if the index requirements are met, the design of the inner-rotating air inlet based on flow field self-regulation is completed. The total pressure recovery coefficient of the air inlet outlet of the embodiment of the present invention is 0.42, and the outlet Mach number is 2.85, which meets the performance index requirements.

[0037] Furthermore, in S1, the external compression shock wave I3 is a plurality of oblique shock waves, a curvilinear shock wave, or a combination of a curvilinear shock wave and an oblique shock wave.

[0038] Furthermore, in S5, the shape of the inner cone air inlet 21 can be rectangular, elliptical or circular.

[0039] Furthermore, in S6, the performance parameters of the inlet duct include the outlet total pressure recovery coefficient and the outlet Mach number.

[0040] The present invention is described in detail above in combination with specific implementation methods and exemplary examples. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments; the above description cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, the technical solution of the present invention and its implementation methods may be subjected to a variety of equivalent substitutions, modifications or improvements, all of which fall within the scope of the present invention; the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for designing an inward-turning air intake based on flow field self-regulation, characterized in that: The following steps are involved: S1, under the condition of the incoming flow at a given design point, the external compression surface (1) and the lip (2) are designed by two-dimensional shock wave theory to generate the inlet profile so that the external compression shock wave I (3) and the lip shock wave I (4) meet the shock wave contact requirement; S2, under the condition of the incoming flow at the given starting point, the inlet profile generated by S1 is calculated by the two-dimensional shock wave theory, and it is obtained that the external compression shock wave II (5) is located outside the lip (2), and the lip shock wave II (6) is located upstream of the lip shock wave I (4). The inlet profile is modified upstream of the lip shock wave incident point, and grooves are set on the inlet profile to form an inlet profile with grooves; S3, under the given starting point flow condition, the inlet profile with grooves formed by S2 is numerically simulated and calculated. Under the starting point condition, the lip shock wave II (6) is incident on the wall surface, generating a separation zone (7), extracting the separation zone boundary (8) of the separation zone (7), replacing the inlet profile with the separation zone boundary (8), and generating an aerodynamic-based inlet reference profile (9); S4, for the aerodynamic-based inlet reference profile (9) formed by S3, numerical simulation calculations are carried out within the operating range, and the aerodynamic throat adaptive adjustment capability is tested according to the flow field characteristics. As the incoming flow Mach number increases, the size of the separation zone (7) will increase accordingly, squeezing the mainstream zone (10) outside the separation zone; If a large amount of overflow occurs in the intake duct or a large amplitude oscillation occurs in the separation zone within the design operating range, then return to S3, modify the aerodynamic-based intake duct reference profile (9), and expand the intake duct flow area; if the requirements are met, enter S5; S5, the aerodynamically-based inlet reference profile (9) designed in S4 is rotated along the axis of symmetry to form an axisymmetric inner cone inlet (21), and the inlet airflow capture entrance shape (22) is given according to the aircraft shape requirements. Under the design point incoming flow condition, the inner cone inlet forms an outer compression surface shock wave I (3), streamlines are traced from the inlet entrance (22) to form a series of streamlines, and the streamlines (23) downstream of the outer compression surface shock wave I (3) are combined to form an inner rotating inlet (24) with aerodynamic self-regulation capability; S6, performing CFD calculation on the inward-turning air inlet (24) formed in S5, evaluating the performance parameters of the air inlet under various operating conditions based on the calculation results, and comparing them with the performance parameter index requirements. If the index requirements are not met, returning to S3, modifying the aerodynamic-based air inlet reference profile (9); if the index requirements are met, completing the design of the inward-turning air inlet based on flow field self-regulation.

2. The method for designing an inward-rotating air intake based on flow field self-regulation according to claim 1, characterized in that: In S1, the external compression shock wave I (3) is a combination of multiple oblique shock waves, a curvilinear shock wave, or a curvilinear shock wave and an oblique shock wave.

3. The method for designing an inward-rotating air intake based on flow field self-regulation according to claim 1, characterized in that: In S5, the shape of the inner cone air inlet (21) can be rectangular, elliptical or circular.

4. The method for designing an inward-rotating air intake based on flow field self-regulation according to claim 1, characterized in that: In S6, the performance parameters of the inlet duct include the outlet total pressure recovery coefficient and the outlet Mach number.

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