A design method for an inward-rotating air inlet based on flow field self-regulation

Abstract

This application discloses a design method for an inward-turning inlet based on flow field self-regulation, comprising the following steps: S1. Generating an inlet profile scheme under given design point inflow conditions; S2. Modifying the inlet profile under given starting point inflow conditions to form an inlet profile with grooves; S3. Generating an aerodynamic-based inlet reference profile; S4. Verifying the adaptive adjustment capability of the aerodynamic throat within the operating range based on the inlet reference profile; S5. Generating an inward-turning inlet with aerodynamic adaptive adjustment capability based on the inlet reference profile designed in S4; and S6. Iterating and optimizing the inward-turning inlet formed in S5. The present invention utilizes the virtual wall formed in the separation zone 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 within the Mach number range of 3-7.

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] To achieve stable operation of inlets over a wide speed range, flow control methods such as suction and bleed flow, widely used in aircraft inlets, face serious challenges at high speeds, including a narrow range of applicability and the risk of thermal damage to pores. Geometric adjustment methods also face challenges such as immature high-temperature dynamic seals and materials, and a high risk of thermal damage to gaps. Developing a wide-range inlet with a fixed geometry, avoiding solutions such as geometric adjustment mechanisms and slotted suction that compromise structural strength under high-temperature conditions, is crucial for achieving long-duration, high-load, and repeatable high-speed flight. Summary of the Invention

[0003] In light of this, the present invention aims to provide a design method for an inward-turning inlet based on flow field self-regulation. By designing the inward-turning inlet profile and utilizing the principle of an aerodynamic throat, this invention achieves adaptive adjustment of the inward-turning inlet over a wide range of conditions, broadening the inward-turning inlet's operating range and avoiding the structural and thermal protection issues associated with geometric adjustment and aspiration techniques. This design method does not include inward-turning inlets with three-dimensional curved surface features.

[0004] The present invention provides a method for designing an inward-rotating air inlet 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 outer compression surface and lip are designed by two-dimensional shock wave theory to generate the inlet profile so that the outer compression shock wave I and the lip shock wave I meet the shock wave contact requirement;

[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 using the two-dimensional shock wave theory. The generated external compression shock wave II and lip shock wave II are located outside the lip, and the lip shock wave II is located upstream of the lip shock wave I because the incoming flow Mach number at the starting point is lower than the incoming flow Mach number at the design point. The inlet profile is modified upstream of the lip shock wave incident point by setting grooves on the inlet profile to form an inlet profile with grooves;

[0007] S3, under the given starting point flow conditions, numerical simulation calculation is performed on the inlet profile with grooves formed by S2. Under the starting point conditions, the lip shock wave II is incident on the wall surface, generating a separation zone. The separation zone boundary is extracted and the separation zone boundary is used to replace the inlet profile to generate an aerodynamic-based inlet reference profile.

[0008] S4, for the aerodynamic-based inlet duct reference surface formed in S3, numerical simulation calculations are carried out within the operating range to verify its aerodynamic throat adaptive adjustment capability based on the flow field characteristics;

[0009] Under starting point conditions, a separation zone is virtually nonexistent, ensuring the inlet can start normally at relatively low incoming flow velocities. As the incoming flow Mach number increases, the size of the separation zone increases, squeezing the mainstream flow outside the separation zone. The separation zone boundary effectively forms an aerodynamic wall, further compressing the mainstream flow. If, within the design operating range, the inlet generates significant overflow or the separation zone experiences large-amplitude oscillations, return to S3, modify the aerodynamically-based inlet reference profile, and expand the inlet flow area.

[0010] S5: The aerodynamically designed inlet reference profile completed in S4 is rotated along the axis of symmetry to form an axisymmetric inner cone inlet. The inlet airflow capture inlet shape is given according to the aircraft shape requirements. Under the design point inflow conditions, the inner cone inlet will also form an external compression shock wave I. Streamlines are traced from the inlet airflow capture inlet shape to form a series of streamlines. The streamlines downstream of the external compression shock wave I are combined to form an inward-rotating inlet with aerodynamic self-regulation capability.

[0011] S6: Perform CFD calculations on the inward-turning air inlet formed in S5. Based on the calculation results, evaluate the performance parameters of the air inlet under various operating conditions and compare them with the performance parameter index requirements. If the index requirements are not met, return to S3 and 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 intake is rectangular, elliptical or circular.

[0014] Furthermore, in S6, the performance parameters of the inlet 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 it can adaptively adjust as the incoming flow conditions change, and proposes the "aerodynamic throat" principle, that is, by rationally designing the shape of the inlet wall, the "virtual wall" formed in 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 inlet duct profile under the design point inflow 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 air inlet with grooves under the starting point inflow 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 inflow 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 inward-rotating air intake in Example S4 of the present invention;

[0024] Figure 8 The inward-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 surface, 10. Main stream area, 21. Inner cone inlet, 22. Inlet airflow capture inlet shape, 23. Streamline, 24. Inward-turning inlet. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described below with reference to 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 requirements are 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 inward-rotating air inlet based on flow field self-regulation, which is characterized by comprising the following steps:

[0030] S1, at a given design point and under the incoming flow 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 Figure 1, since the Mach number of the inflow at the starting point is lower than the Mach number of the inflow 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 grooves, as shown in Figure 1. Figure 3 As shown;

[0032] S3, under the 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, as shown in 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 the 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; as the inflow Mach number increases, under the inflow condition of Mach number 6 at the design point, a clear separation zone 7 appears, and the size of the separation zone 7 will increase accordingly, squeezing the mainstream area 10 outside the separation zone. The boundary of the separation zone is equivalent to forming an aerodynamic wall, which compresses the airflow in the mainstream area 10 more strongly; if a large amount of overflow is generated in the air inlet within the design operating range, or the separation zone produces large-amplitude oscillations, then return to S3, modify the aerodynamic-based air inlet reference surface 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 is rotated along the symmetry axis to form an axisymmetric inner cone air intake duct 21, as shown in FIG. Figure 7As shown, according to the requirements of the aircraft shape, the inlet airflow capture inlet shape 22 is given. Under the design point inflow condition, the inner cone inlet will also form an external compression shock wave I3. Streamline tracing is performed from the inlet airflow capture inlet shape 22 to form a series of streamlines. The streamlines 23 downstream of the external compression shock wave I3 are combined to form an inward-rotating inlet 24 with aerodynamic self-regulation capability. The inward-rotating inlet designed in this embodiment is shown in FIG. Figure 8 As shown;

[0036] S6. Perform CFD calculations on the inward-turning inlet 24 formed in S5. Based on the calculation results, evaluate the inlet's performance parameters under various operating conditions and compare them with the required performance parameters. If the parameters do not meet the requirements, return to S3 and modify the aerodynamic-based inlet reference profile 9. If the parameters meet the requirements, the design of the inward-turning inlet based on flow field self-regulation is completed. The inlet outlet total pressure recovery coefficient of this embodiment of the present invention is 0.42, and the outlet Mach number is 2.85, meeting the performance 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 include the outlet total pressure recovery coefficient and the outlet Mach number.

[0040] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. The above description is illustrative and not exhaustive, and is not limited to the disclosed embodiments; the above description should not be construed as limiting the present invention. Those skilled in the art will appreciate that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention, all of which fall within the scope of the present invention; the scope of protection of the present invention shall be subject to the appended claims.

Claims

1. A design method for an inward-turning air intake based on flow field self-regulation, characterized in that: The following steps are involved: S1, under the given design point incoming flow conditions, the outer compression surface (1) and the lip (2) are designed by two-dimensional shock wave theory to generate the inlet profile so that the outer compression shock wave I (3) and the lip shock wave I (4) meet the shock wave contact requirement; S2, under the given starting point flow condition, the inlet profile generated by S1 is calculated by 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). The separation zone boundary (8) of the separation zone (7) is extracted, and the separation zone boundary (8) is used to replace the inlet profile to generate an aerodynamic-based inlet reference profile (9); S4, for the aerodynamic-based inlet duct 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 based on 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 designed inlet reference profile (9) completed in S4 is rotated along the symmetry axis to form an axisymmetric inner cone inlet (21), and the inlet airflow capture inlet 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), and streamlines are traced from the inlet airflow capture inlet shape (22) to form a series of streamlines. 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, perform CFD calculation on the inward-turning air inlet (24) 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 and modify the aerodynamic-based air inlet reference surface (9); if the index requirements are met, complete the design of the inward-turning air inlet based on flow field self-regulation.

2. The method for designing an inward-turning 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-turning 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) is rectangular, elliptical or circular.

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

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