A method of designing a flow adjustable intake passage

Abstract

The application discloses a kind of adjustable intake passage design methods of flow rate.By synergic regulation precursor angle rotation, throat height change and lip mask front and rear telescopic quantity, realize the dynamic flow rate matching and aerodynamic performance optimization of intake passage in wide speed range working condition, finally, while meeting the demand of large flow rate, significantly improve the performance and flow stability of intake passage.The scheme realizes the self-adaptive control of profile by modular geometric adjustment mechanism, solves the problem of performance drop of traditional fixed intake passage at non-design point and limited adjustment range of existing adjustable scheme, and is suitable for hypersonic aircraft and variable cycle engine.

Description

Technical Field

[0001] This invention relates to the field of aircraft design, and in particular to a design method for an air intake with a wide range of adjustable flow rates. Background Technology

[0002] The air intake is a core component of an aircraft, directly affecting engine performance and flight safety. Its main function is to efficiently convert incoming airflow into the stable, high-pressure airflow required by the engine.

[0003] Wide-range adjustable two-dimensional inlets are a key technology in the aerospace field developed to meet the needs of hypersonic vehicles and advanced air-breathing propulsion systems. Their core objective is to achieve efficient air intake capture and flow control for aircraft across a wide speed range (subsonic / transonic / supersonic / hypersonic) and multiple operating conditions through dynamic geometric adjustment capabilities, including adjusting the fore-and-aft position of the lip mask and the throat height. This addresses the problem of drastic performance degradation of traditional fixed-geometry inlets outside of design points. However, designing an effective method to create a high-flow-rate adjustable inlet that meets the startup conditions remains a challenge.

[0004] Existing adjustable intake systems mostly use rotating lips and compression throats to match engine operating conditions. This adjustment method has very limited flow regulation and cannot meet a wide range of flow regulation needs. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for designing an adjustable air intake, which can be used to design an adjustable air intake that meets the starting conditions.

[0006] Technical solution: This invention provides a method for designing an adjustable air intake, comprising the following steps:

[0007] 1) Set the flow rate requirement Q, flight altitude and forebody length L under the condition of incoming Mach number M0 in the target velocity range. At the same time, calculate the capture altitude H0 based on the incoming Mach number M0 and the inlet width D using the following formula; where γ is the specific heat ratio, R is the gas constant, ρ0 is the incoming gas density and T0 is the incoming gas temperature.

[0008]

[0009] Where a0 is the speed of sound at this flight altitude, and the capture altitude H0 is the vertical distance from the lip mask tip O to the forebody tip P;

[0010] 2) Set the lip cover (1) to be adjustable for front and back extension. Combine H0, front body length L and lip cover tip O position to determine the tilt angle θ of the front body. The tilt angle θ is dynamically adjusted by rotating the front body around the fixed hinge point A.

[0011] 3) Based on the oblique shock wave relation, determine the relationship between the shock wave angle β and the tilt angle θ;

[0012] 4) Adjust the front and back extension of the lip shield (1) so that the oblique shock wave (6) converges at the tip O of the lip shield until the shock wave sealing condition is met, and determine the position of the lip shield;

[0013] 5) Select a throat Mach number M2 between 1.3 and 1.6;

[0014] 6) Calculate the throat height H2 and adjust the inner compression surface accordingly to achieve throat geometry control;

[0015] 7) The inlet height H1 of the air intake is calculated based on the throat height H2 and the positions of the fixed hinge point A and the lip tip O, and then the internal contraction ratio ICR is calculated.

[0016] Furthermore, the flow requirement Q mentioned in step 1) is to be preset according to the aircraft engine operating conditions and speed range. The density ρ0 and temperature T0 of the incoming flow are obtained from the flight altitude through the ISA standard atmospheric table, and the forebody length L is the distance from the inlet of the air intake to the hinge point A.

[0017] Furthermore, in step 2), since the lip cover (1) is adjusted by stretching back and forth, that is, the height of the lip cover tip O is determined, and the position of the front end point P in the vertical direction is determined by the obtained capture height H0; when the fixed hinge point A is fixed, the front body tilt angle θ is also determined.

[0018] Furthermore, in step 3): the formula for calculating the oblique shock wave is as follows:

[0019]

[0020] The shock angle β of the oblique shock wave is obtained by using the Mach number M0 and the tilt angle θ through chart lookup, interpolation calculation, or program iterative calculation.

[0021] Furthermore, in step 4), in order to meet the aerodynamic requirements of the shock wave sealing, the oblique shock wave (6) passes through the tip of the lip cover O, and the lip cover (1) is set to be adjustable for front and rear extension. That is, after the height of the lip cover is determined, the oblique shock wave (6) passes through the tip of the lip cover O to determine the position of the tip of the lip cover O and thus determine the position of the lip cover.

[0022] Furthermore, in step 6), the selection of the throat Mach number M2 is based on the balance between the intake anti-separation margin and the total pressure recovery performance. The throat height H2 is calculated by the following formula, where ρ2 is the density of the incoming flow at the throat position.

[0023] .

[0024] Further, in step 7), the inner compression surface includes a first inner compression surface (3), a second inner compression surface (4), and a third inner compression surface (5), wherein the front end of the first inner compression surface is hinged to the rear end of the front body (2) at point A, the front end of the second inner compression surface is hinged to the rear end of the first inner compression surface at point B, and the front end of the third inner compression surface is hinged to the rear end of the second inner compression surface at point C. The adjustment of the inner compression surface includes:

[0025] The first inner compression surface (3) rotates around point A to change the throat height H2;

[0026] The second inner compression surface (4) is kept parallel to the lip cover (1) by moving the two non-fixed hinge points B and C.

[0027] The third inner compression surface (5) rotates around point C to assist the movement of the second inner compression surface (4).

[0028] Furthermore, in step 7), the internal contraction ratio ICR is the ratio of the inlet cross-sectional area A1 to the throat area A2, and the internal contraction ratio ICR is calculated using the following formula:

[0029]

[0030] M1 is the Mach number at the inlet of the air intake; determine whether the calculated ICR can meet the start-up conditions of the air intake. If the conditions are met, complete the air intake design based on gas dynamics.

[0031] Furthermore, according to the one-dimensional isentropic flow equation, the relationship between the area ratio and the Mach number is:

[0032]

[0033] Among them, A ∗ γ is the area at the throat at the critical time, and γ is the specific heat ratio.

[0034] When the throat Mach number reaches the speed of sound, i.e., M2=1, the maximum internal contraction ratio is reached. Substituting this into the one-dimensional isentropic flow equation, we get:

[0035]

[0036] This formula is known as the Kantrowitz limit, which represents the maximum internal contraction ratio that the intake can initiate at a given incoming Mach number.

[0037] Beneficial Effects: Compared with existing technologies, this invention can design an adjustable air intake with adjustable lip mask position and throat height by rotating the forebody, ensuring the intake meets startup conditions. Furthermore, this design method innovatively proposes achieving high-flow-rate inlet while simultaneously sealing the shock wave by translating the lip mask and rotating the forebody, based on the Mach number requirements of different operating speed ranges. Simultaneously, through related throat adjustments, a high-performance adjustable air intake design is achieved.

[0038] The present invention also provides an air intake designed according to the above-mentioned flow-adjustable air intake design method, including a lip cover (1), a front body (2), a first inner compression surface (3), a second inner compression surface (4), and a third inner compression surface (5) that move along the front-rear direction of the air intake, wherein the front end of the first inner compression surface is hinged to the rear end of the front body (2), the front end of the second inner compression surface is hinged to the rear end of the first inner compression surface, and the front end of the third inner compression surface is hinged to the rear end of the second inner compression surface; a portion of the rear section of the first inner compression surface, the second inner compression surface, and the third inner compression surface together with the lip cover form an inner channel of the air intake. Attached Figure Description

[0039] Figure 1 Flowchart of the design method for an ultra-large flow adjustable air intake in this invention.

[0040] Figure 2 This is a two-dimensional cross-sectional schematic diagram of the air intake designed in this invention under incoming flow Mach 5 conditions.

[0041] Figure 3 This is a two-dimensional cross-sectional schematic diagram of the air intake designed in this invention under incoming flow Mach 2 conditions. Detailed Implementation

[0042] This invention provides a design method for a high-flow-rate adjustable intake under high-speed incoming flow conditions. The structure of the target intake designed by this method is as follows: Figure 2 , Figure 3 As shown, the system includes a lip cover 1, a front body 2, a first inner compression surface 3, a second inner compression surface 4, and a third inner compression surface 5, all of which move along the front-rear direction of the air intake. The front end of the first inner compression surface 3 is hinged to the rear end of the front body 2; the front end of the second inner compression surface 4 is hinged to the rear end of the first inner compression surface 3; and the front end of the third inner compression surface 5 is hinged to the rear end of the second inner compression surface 4. A portion of the rear section of the first inner compression surface 3, the second inner compression surface 4, and the third inner compression surface 5 together form the inner channel of the air intake with the lip cover. The lip cover 1 is adjustable for front-rear extension.

[0043] like Figure 1 As shown, the design method of the high-flow-rate regulating intake under high-speed incoming flow conditions in this embodiment includes the following:

[0044] 1. The flow rate requirement Q is preset according to the aircraft engine operating conditions and speed range. Other aerodynamic parameters of the incoming flow, such as ρ0 and T0, can be calculated from the flight altitude. The forebody length L is the distance from the air intake to the hinge point A.

[0045] 2. The formula for calculating the required flow rate Q is as follows:

[0046]

[0047] The capture height H0 is constrained by the incoming flow parameters to ensure the geometric correlation between the forebody tip P and the lip mask tip O.

[0048] 3. Since the lip cover 1 is adjusted by stretching back and forth, the height of the lip cover tip O is fixed. The vertical position of the front end point P of the front body is then determined by the obtained capture height H0. When the fixed hinge point A is fixed, the front body tilt angle θ is also determined.

[0049] 4. The formula for calculating oblique shock waves is as follows:

[0050]

[0051] The shock angle β of the oblique shock wave can be calculated from the Mach number M0 and the slope angle θ by means of chart lookup, interpolation calculation, or iterative calculation by program.

[0052] 5. In order to meet the aerodynamic requirements of shock wave sealing, the oblique shock wave 6 passes through the tip O of the lip cover. The lip cover 1 is set to be adjustable for front and rear extension. That is, after the height of the lip cover is determined, the oblique shock wave 6 passes through the tip O of the lip cover to determine the position of the tip O of the lip cover and thus determine the position of the lip cover.

[0053] 6. The target Mach number M2 is selected based on the balance between the intake anti-separation margin and the total pressure recovery performance, and closed-loop control is achieved through real-time feedback of the throat height H2. Considering the impact on performance, it is finally determined to be between 1.3 and 1.6.

[0054]

[0055] Meanwhile, the parameter changes of the airflow after passing through the oblique shock wave 6 can be obtained from the parameter change formula before and after the oblique shock wave. Thus, the aerodynamic parameters after the oblique shock wave can be calculated using the following formula. Where M1 is the Mach number at the inlet of the air intake, and the remaining aerodynamic parameters can be used to evaluate the aerodynamic performance of the air intake.

[0056]

[0057]

[0058]

[0059]

[0060] 7. Adjustment of the inner compression surface includes:

[0061] The first inner compression surface 3 rotates around point A to change the throat height H2;

[0062] The second inner compression surface 4 maintains parallelism with the lip cover 1 by oblique translation.

[0063] The third inner compression surface 5 rotates around point C to match the surface curvature, preventing flow separation and assisting the translation of the second inner compression surface 4.

[0064] 8. The internal contraction ratio can be calculated using the area-Mach number formula for one-dimensional isentropic flow.

[0065]

[0066]

[0067] A larger contraction ratio can improve compression efficiency, but it may cause flow separation or shock wave oscillations, preventing the intake from starting. The core of Kantrowitz theory is to determine the maximum internal contraction ratio at which the intake can start for a given incoming Mach number (M0).

[0068] According to the one-dimensional isentropic flow equation, the relationship between the area ratio and the Mach number is as follows:

[0069]

[0070] Among them, A ∗ γ is the critical area (area at the throat), and γ is the specific heat ratio (1.4 for air).

[0071] When the Mach number in the throat reaches the speed of sound (M2=1), the maximum internal contraction ratio is reached. Substituting this into the previous one-dimensional isentropic flow equation, we can obtain...

[0072]

[0073] This formula is known as the Kantrowitz limit, which represents the maximum internal contraction ratio that the intake can initiate at a given incoming Mach number.

[0074] Determine whether the calculated ICR meets the intake duct start-up conditions. If the conditions are met, the intake duct design based on gas dynamics can be completed.

[0075] Based on the above design method, the designed flow-adjustable intake duct is as follows: Figure 2 , Figure 3 As shown. Among them, Figure 2 This is a two-dimensional cross-sectional schematic diagram of the air intake under Mach 5 inflow conditions. Figure 3 This is a two-dimensional cross-sectional schematic diagram of the air intake under Mach 2 incoming flow conditions.

Claims

1. A method for designing an adjustable air intake, characterized in that, Includes the following steps: 1) Set the flow rate requirement Q, flight altitude and forebody length L under the condition of incoming Mach number M0 in the target velocity range. At the same time, calculate the capture altitude H0 based on the incoming Mach number M0 and the inlet width D using the following formula; where γ is the specific heat ratio, R is the gas constant, ρ0 is the incoming gas density and T0 is the incoming gas temperature. ， Where a0 is the speed of sound at this flight altitude, and the capture altitude H0 is the vertical distance from the lip mask tip O to the forebody tip P; 2) Set the lip cover (1) to be adjustable for front and back extension. Combine H0, front body length L and lip cover tip O position to determine the tilt angle θ of the front body. The tilt angle θ is dynamically adjusted by rotating the front body around the fixed hinge point A. 3) Based on the oblique shock wave relation, determine the relationship between the shock wave angle β and the tilt angle θ; 4) Adjust the front and back extension of the lip shield (1) so that the oblique shock wave (6) converges at the tip O of the lip shield until the shock wave sealing condition is met, and determine the position of the lip shield; 5) Select a throat Mach number M2 between 1.3 and 1.6; 6) Calculate the throat height H2 and adjust the inner compression surface accordingly to achieve throat geometry control; 7) The inlet height H1 of the air intake is calculated based on the throat height H2 and the positions of the fixed hinge point A and the lip tip O, and then the internal contraction ratio ICR is calculated.

2. The adjustable air intake design method according to claim 1, characterized in that: The flow requirement Q mentioned in step 1) is to be preset according to the aircraft engine operating conditions and speed range. The density ρ0 and temperature T0 of the incoming flow are obtained from the flight altitude through the ISA standard atmospheric table. The forebody length L is the distance from the inlet of the air intake to the hinge point A.

3. The adjustable air intake design method according to claim 2, characterized in that: In step 2), since the lip cover (1) is adjusted by stretching back and forth, the height of the lip cover tip O is determined. The position of the front end point P in the vertical direction is determined by the obtained capture height H0. When the fixed hinge point A is fixed, the front body tilt angle θ is also determined.

4. The adjustable air intake design method according to claim 3, characterized in that... In step 3), the formula for calculating the oblique shock wave is as follows: ， The shock angle β of the oblique shock wave is obtained by using the Mach number M0 and the tilt angle θ through chart lookup, interpolation calculation, or program iterative calculation.

5. The adjustable air intake design method according to claim 4, characterized in that: In step 4), in order to meet the aerodynamic requirements of the shock wave sealing, the oblique shock wave (6) passes through the tip point O of the lip cover, and the lip cover (1) is set to be adjustable for front and rear extension. That is, after the height of the lip cover is determined, the oblique shock wave (6) passes through the tip point O of the lip cover to determine the position of the tip point O of the lip cover and thus determine the position of the lip cover.

6. The adjustable air intake design method according to claim 5, characterized in that: In step 6), the selection of the throat Mach number M2 is based on the balance between the intake anti-separation margin and the total pressure recovery performance. The throat height H2 is calculated by the following formula, where ρ2 is the density of the incoming flow at the throat position. 。 7. The adjustable air intake design method according to claim 6, characterized in that: Step 7) The inner compression surface includes a first inner compression surface (3), a second inner compression surface (4), and a third inner compression surface (5). The front end of the first inner compression surface is hinged to the rear end of the front body (2) at point A. The front end of the second inner compression surface is hinged to the rear end of the first inner compression surface at point B. The front end of the third inner compression surface is hinged to the rear end of the second inner compression surface at point C. The adjustment of the inner compression surface includes: The first inner compression surface (3) rotates around point A to change the throat height H2; The second inner compression surface (4) is kept parallel to the lip cover (1) by moving the two non-fixed hinge points B and C. The third inner compression surface (5) rotates around point C to assist the movement of the second inner compression surface (4).

8. The adjustable air intake design method according to claim 7, characterized in that: In step 7), the internal contraction ratio (ICR) is the ratio of the inlet cross-sectional area A1 to the throat area A2. The internal contraction ratio (ICR) is calculated using the following formula: ， M1 is the Mach number at the inlet of the air intake; determine whether the calculated ICR can meet the start-up conditions of the air intake. If the conditions are met, complete the air intake design based on gas dynamics.

9. An intake duct designed according to the flow-adjustable intake duct design method according to any one of claims 1 to 8, characterized in that: It includes a lip cover (1) that moves along the front and rear direction of the air intake, a front body (2), a first inner compression surface (3), a second inner compression surface (4), and a third inner compression surface (5), wherein the front end of the first inner compression surface is hinged to the rear end of the front body (2), the front end of the second inner compression surface is hinged to the rear end of the first inner compression surface, and the front end of the third inner compression surface is hinged to the rear end of the second inner compression surface; a portion of the rear section of the first inner compression surface, the second inner compression surface, and the third inner compression surface together with the lip cover form the inner channel of the air intake.

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