A wide-range air inlet passage design method based on double-shoulder wave-breaking flow field stability control

Abstract

The application provides a wide-range air inlet channel design method based on double-shoulder wave-damping flow field stability control, which comprises the following steps: constructing two shoulders corresponding to high and low Mach numbers of the air inlet channel, so that the lip cover shock wave is always located between the two shoulders; and using the expansion wave formed by the shoulders to greatly weaken the strength of the lip cover shock wave, so that the size of the separation zone is inhibited, and the flow field stability control of the wide-range air inlet channel is realized from the source of the wave system organization. Compared with the existing suction flow field stability control method, the actual flow for the engine is improved, the additional resistance of the suction groove is reduced, and the performance of the wide-range air inlet channel is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of air-breathing hypersonic vehicles, and more specifically to a wide-area air intake design method based on the stable control of the wave-absorbing flow field on both shoulders. Background Technology

[0002] As air-breathing hypersonic vehicles continue to expand their flight capabilities across wider speed and airspace ranges, the engines are required to operate within this wider range. The air intake, responsible for efficiently compressing the free-flowing air to provide the necessary airflow to the engine, is an essential component of air-breathing ramjet-powered aircraft. Its flow field stability directly affects the aerodynamics of the aircraft and the stable operating boundary of the engine. However, the free-flowing air is compressed step-by-step through the intake, a process against the pressure gradient. Especially with low-Mach number incoming air, the resistance to back pressure is poor, easily leading to instability in the intake flow field, resulting in large flow separation zones and preventing engine startup. Therefore, widening the lower boundary of the operating Mach number of hypersonic air intakes is of significant supporting importance for the development of wide-range aircraft.

[0003] In reality, shock waves and boundary layer interference are severe in wide-area inlets, especially the interference between the lip-induced shock wave and the boundary layer. Inevitably, flow separation occurs in the constriction section within the inlet. Improper suppression or control of this separation zone can lead to instability in the inlet flow field, causing the separation zone to continuously expand under the influence of the reverse pressure gradient until it ceases to function. In engineering practice, numerous suction channels are designed in the shock wave-boundary layer interference region to expel the high-pressure boundary layer from the engine flow path, effectively suppressing and controlling the separation zone. However, these suction channels cause losses in compressed airflow and additional aerodynamic drag. If the interference intensity between the lip-induced shock wave and the boundary layer can be reduced at the source through wave system organization, eliminating or suppressing the size of the separation zone and improving the flow field stability at low Mach numbers in wide-area inlets, suction channels can be eliminated or their number reduced, further improving inlet performance. Therefore, it is essential to develop flow field stability control methods for wide-area inlets based on wave system organization. Summary of the Invention

[0004] Purpose of the invention: To solve the above problems, this invention provides a wide-range air intake design method for stable control of the wave-damping flow field on both shoulders. This method achieves stable control of the flow field over a wide Mach number range in the air intake without using suction slots, thereby improving the performance of the air intake and meeting the requirements of wide-range flight.

[0005] Technical solution: To achieve the above objectives, the technical solution adopted by this invention includes the following steps:

[0006] The method of three-stage external compression and one-stage internal compression is adopted. The deflection angles of the first and second stage compression surfaces are given artificially. The Mach number and angle before and after each stage compression shock wave are obtained by theoretical oblique shock wave relationship. According to the geometric principle of compression shock wave sealing and lip mask shock wave shoulder wave dissipation, the preliminary profile scheme of the air intake is determined by theoretical oblique shock wave relationship.

[0007] 1) Using the high Mach number of the wide-range intake as the design Mach number, a three-stage external compression and a one-stage internal compression method is adopted. Given the deflection angles of the first and second stage compression surfaces, the Mach number and angle before and after each stage compression shock wave are obtained from the theoretical oblique shock wave relationship. According to the geometric relationship corresponding to the compression shock wave sealing and lip mask shock wave shoulder wave damping principle, the preliminary profile scheme of the intake is determined.

[0008] 2) Considering the structural thermal protection requirements, the leading edge and lip of the air intake are rounded and passivated. Based on the shock wave position obtained by numerical simulation under viscous passivation conditions, with the goal of sealing the compression shock wave and damping the shock wave shoulder of the lip mask, the length of the first-stage compression surface and the second-stage compression surface, the flow direction position of the lip mask, and the position of the air intake shoulder are optimized.

[0009] 3) The average Mach number M of the mass flow rate at the throat outlet section t For high Mach number M h With approximately half of the target value as the objective, the throat height h corresponding to a high Mach number is determined iteratively. t This forms the basic shape scheme for a wide-area air intake.

[0010] 4) Using the intersection of the second-stage compression surface and the third-stage compression surface as the axis of rotation, and the third-stage compression surface as the rotation adjustment surface, a throat height adjustment scheme using a slider to push a parallel double connecting rod is adopted to achieve the adjustment of the contraction ratio in the wide-range intake duct.

[0011] 5) Rotate the third-stage compression surface clockwise by an angle δ to increase the throat height, thus achieving a wide-range inlet with a low Mach number M. l Numerical simulations were used to obtain the Mach number M at the throat exit. t The position of the low Mach number lip shock wave is determined iteratively by aiming for the Mach number at the throat exit to be about half that of the low Mach number.

[0012] 6) Based on the location of the low Mach number lip shock wave, the third-stage compression surface is redesigned. An inflection point is added to the original straight section to construct the second intake shoulder, forming a three-stage compression surface with a shoulder. The inflection point is located on the low Mach number lip shock wave. The specific location can be determined according to the fact that the expansion angle of the low Mach number shoulder is equal to the expansion angle of the high Mach number shoulder. Thus, a preliminary scheme for a wide-area intake with stable control of the double-shoulder wave-absorbing flow field is formed.

[0013] 7) For the preliminary scheme of wide-area inlet for stable control of wave-absorbing flow field in the double-shoulder section, numerical simulations of high Mach number and low Mach number were completed to obtain the position of the lip shock wave and the Mach number of the throat outlet section under the double-shoulder profile. The position of the inflection point of the third-stage compression surface and the height of the throat were iteratively optimized.

[0014] 8) The expansion wave-damping effect of the second intake shoulder is enhanced by using a cubic Bézier curve. The midpoints of the two straight segments of the third-stage compression surface are used as the tangent endpoints. By changing the length coefficient of the endpoints of the Bézier curve and adjusting the Bézier curve, it is made to deflect rapidly at the low Mach number lip shock wave.

[0015] Furthermore, the high Mach number is generally taken as the upper limit of the working Mach number range, but should not exceed Mach number 7.0.

[0016] Furthermore, the deflection angle between the first-stage compression surface and the second-stage compression surface should not be too large, generally within 6°.

[0017] Furthermore, the shock wave sealing is achieved by the first-stage compression shock wave and the second-stage compression shock wave striking the intake lip.

[0018] Furthermore, the shoulder wave suppression is achieved by a high Mach number lip shock wave striking the intersection of the third-stage compression surface and the throat profile.

[0019] Furthermore, the length of the larynx is generally equal to the height h of the larynx. t Approximately 1 to 3 times that of the standard.

[0020] Furthermore, the low Mach number is generally taken as the lower limit of the working Mach number range, but should not be lower than Mach number 2.5.

[0021] Furthermore, the wide-range air intake has a low Mach number M. l The numerical simulation was performed under conditions with a suction tank.

[0022] Furthermore, the low Mach number shoulder expansion angle is an acute angle formed by two straight line segments of the third-level compression surface with an inflection point, and should generally be no less than 6°.

[0023] Furthermore, the high Mach number shoulder expansion angle is the acute angle formed by the tail end of the third-stage compression surface with an inflection point and the throat, and should generally be no less than 6°.

[0024] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: A double-shoulder design is constructed according to the upper and lower values ​​of the operating Mach number range. The lip shock wave is always located between the two shoulders, and the expansion wave formed by the shoulders significantly weakens the intensity of the lip shock wave, suppressing the size of the separation zone and achieving stable flow field control in the wide-range inlet. Compared with existing suction flow field stabilization control methods, this invention increases the actual flow rate for the engine and reduces the additional resistance of the suction channel, greatly benefiting the improvement of wide-range inlet performance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the high Mach number profile of the wide-range air intake described in this invention.

[0026] Figure 2 This is a schematic diagram illustrating the principle of the wide-range intake duct adjustment scheme described in this invention.

[0027] Figure 3 This is a schematic diagram of the low Mach number profile of the wide-range air intake described in this invention.

[0028] Figure 4 This is a schematic diagram of the wide-area air intake double-shoulder design described in this invention.

[0029] Figure 5 This is a schematic diagram of the wide-area air intake based on the stable control of the double-shoulder wave-damping flow field as described in this invention.

[0030] Figure 6 This is a schematic diagram illustrating the enhanced design of the shoulder expansion wave-damping effect described in this invention. Detailed Implementation

[0031] This invention discloses a method for stabilizing and controlling the flow field in a wide-area air intake based on double-shoulder wave reduction. Please refer to [link / reference]. Figures 1 to 5 As shown, the detailed implementation steps of this invention will be described below using a wide-area two-dimensional air intake as an example.

[0032] 1. For example Figure 1 As shown, the design Mach number is the high Mach number of the wide-range intake. A three-stage external compression and a one-stage internal compression method are adopted. The deflection angles of the first and second stage compression surfaces are given empirically. The Mach number and angle before and after each stage compression shock wave are obtained according to the theoretical oblique shock wave relationship. The preliminary profile scheme of the intake is determined according to the geometric relationship corresponding to the compression shock wave sealing and lip mask shock wave shoulder wave damping principle.

[0033] For high Mach numbers, the upper limit of the working Mach number range of the inlet is generally selected, but it should not exceed Mach number 7.0.

[0034] The deflection angles θ1 of the first-stage compression surface 1 and θ2 of the second-stage compression surface 2 should not be too large, generally within 6°.

[0035] Based on the theoretical oblique shock wave relationship shown below, the design Mach number M... h The deflection angle θ1 of the first-stage compression surface 1 can be used to calculate the angle β1 and the Mach number M1 of the first-stage compression shock wave 10. Furthermore, the angle β2 and the Mach number M2 of the second-stage compression shock wave 9 can be calculated from M1 and θ2. Ignoring the influence of the third-stage compression shock wave 8, the deflection angle θ1 of the airflow after compression by the lip cover 6 is then calculated. c The sum of θ1 and θ2, combined with M2, allows us to calculate β. c .

[0036]

[0037] In the formula: M1 is the Mach number of the oblique shock wave front; M2 is the Mach number of the oblique shock wave back; β is the shock wave angle; θ is the deflection angle; and γ is the specific heat ratio of the gas, which is taken as 1.4.

[0038] Based on the sealing of the first-stage compression shock wave 10 and the second-stage compression shock wave 9 (i.e., intersecting at point F of the inlet lip), the length of the first-stage compression surface 1 and the position of the lip cover 6 can be determined by geometric relationships.

[0039] The third-stage compression shock wave 8 can hit the inside of the lip cover. First, arbitrarily give the deflection angle of the third-stage compression surface 3, and its starting position C should be located upstream of the inlet section of the air intake.

[0040] The lip shield 6 is designed according to the principle of minimum aerodynamic drag, that is, it adopts a flat lip shield with single-stage internal compression. The lip shield-induced shock wave 7 intersects at point D on the first intake shoulder of the intake duct (the intersection point D of the third-stage compression surface 3 and the throat 4). The third-stage compression surface 3 can be determined by geometric relationship.

[0041] The length of the larynx 4 is generally equal to the larynx height h. t The throat passage 4 and the tail end of the lip cover 6 form the throat passage outlet section 5, which is 1 to 3 times larger than the throat passage 4.

[0042] 2. Considering the requirements of structural thermal protection, the leading edge A and the lip F of the air intake are rounded and passivated. Based on the position of the shock wave system under the viscous passivation condition obtained by numerical simulation, with the goal of sealing the compression shock wave and damping the shock wave shoulder of the lip mask, the length of the first-stage compression surface 1 and the second-stage compression surface 2, the flow direction position of the lip mask 6, and the position of the first air intake shoulder D are optimized.

[0043] Considering the actual viscosity and passivation conditions, the angle of the compression shock wave is slightly increased, and the lip mask 6 moves upstream according to the position of the first-stage compression shock wave 10; based on the optimized position of the lip mask 6 and the angle of the second-stage compression shock wave 9, the length of the first-stage compression surface 1 is shortened; based on the position of the lip mask-induced shock wave 7, the length of the throat 4 is adjusted to ensure that the high Mach number lip mask-induced shock wave 7 hits point D on the shoulder of the first intake.

[0044] 3. The average Mach number M of the mass flow rate at the throat outlet section 5. t For high Mach number M h The target is about half of the throat Mach number M. t Significantly exceeds high Mach number M h If the height of the larynx is half, then decrease the height of the larynx 4; conversely, if it is half, increase the height of the larynx 4 until the laryngeal Mach number M... t With high Mach number M h With a deviation within ±0.2, the throat height h corresponding to a high Mach number is determined iteratively. t This forms the basic shape scheme of the wide-area air intake.

[0045] 4. For example Figure 2 As shown, with the intersection point C of the second-stage compression surface 2 and the third-stage compression surface 3 as the axis of rotation, and the third-stage compression surface 3 as the rotation adjustment surface, the throat height adjustment scheme of the parallel double connecting rod 12 driven by the slider 11 is adopted to achieve a wide-range intake duct internal contraction ratio h2 / h. t The adjustment.

[0046] 5. Rotate the third-stage compression surface 3 clockwise by an angle δ to increase the height of the throat 4, thus completing the wide-range intake duct with a low Mach number M. l Numerical simulations were used to obtain the average Mach number M of the mass flow rate at the throat outlet section 5. t The position of the low Mach number lip shock wave 13, and the Mach number M at the throat exit. t For low Mach number M l With approximately half of the target value as the objective, the low Mach number M is determined iteratively. l The height of the inferior larynx 4, if the larynx Mach number M t Significantly exceeds low Mach number M l If the height of larynx 4 is half, then decrease the height of larynx 4; conversely, if it is half, increase the height of larynx 4 until the larynx Mach number M is reached. t With low Mach number M l The deviation is within ±0.2.

[0047] low Mach number M l Generally, the lower limit of the wide-range inlet operating Mach number range is taken, but it should not be lower than Mach number 2.5.

[0048] During the numerical calculation, the approximate location of the low Mach number lip shock wave 13 hitting the third-stage compression surface 3 is estimated according to the oblique shock wave relationship, and an venting groove 14 is designed nearby to avoid the inability of the intake duct to start during the numerical calculation, which would affect the determination of the height of the low Mach number throat 4.

[0049] 6. For example Figure 3As shown, based on the position of the low Mach number lip shock wave 13, the third-stage compression surface 3 is redesigned. An inflection point G is added in the middle of the straight segment CD to construct the second shoulder of the intake, forming a three-stage compression surface 15 with a shoulder. The shoulder point G of the second intake is located on the low Mach number lip shock wave 13. Thus, a preliminary scheme for a wide-area intake with stable control of the wave-absorbing flow field with double shoulders is formed.

[0050] like Figure 4 As shown, the angle between line segment CF and line segment FD is the low Mach number shoulder expansion angle θ. l Rotate the shoulder-mounted third-stage compression surface 15 counterclockwise by δ degrees to restore the height of the high Mach number throat 4. At this point, the angle between line segment FD and throat 4 is the high Mach number shoulder expansion angle θ. h Moving the shoulder point G of the second air intake along the low Mach number lip shock wave 13 can simultaneously change the shoulder expansion angle θ corresponding to high and low Mach numbers. l and θ h The position of the second intake shoulder G can be determined by the fact that the shoulder expansion angles are equal at high and low Mach numbers, i.e., θ. l =θ h The angle is generally not less than 6°.

[0051] 7. For example Figure 5 As shown, a preliminary scheme for a wide-area air intake with stable flow field control at the double shoulders is presented, achieving high Mach number M h and low Mach number M l Numerical simulations were used to obtain the position 13 of the low Mach number lip shock wave and the Mach number of the throat outlet section 5 under the double shoulder profile. With the goal of the high Mach number lip shock wave 7 hitting the shoulder D of the first intake and the low Mach number lip shock wave 13 hitting the shoulder G of the second intake as the objective, the position of the inflection point G of the third-stage compression surface 15 and the height of the throat 4 were iteratively optimized.

[0052] 8. For example Figure 6 As shown, if the structure allows, a cubic Bézier curve 16 can be used to enhance the expansion wave-damping effect of the shoulder G of the second air intake. The midpoints H and I of line segments CF and DE are taken as the tangent endpoints, respectively. By changing the length coefficients n1 and n2 of the endpoints of the Bézier curve, the curve is adjusted so that it deflects rapidly at the low Mach number lip shock wave 13.

Claims

1. A wide-area air intake design method based on stable control of the double-shoulder wave-damping flow field, characterized in that, Includes the following steps: 1) Using the high Mach number of the wide-range intake as the design Mach number, a three-stage external compression and a one-stage internal compression method is adopted. Given the deflection angles of the first and second stage compression surfaces, the Mach number and angle before and after each stage compression shock wave are obtained from the theoretical oblique shock wave relationship. According to the geometric relationship corresponding to the compression shock wave sealing and lip mask shock wave shoulder wave damping principle, the preliminary surface scheme of the intake is determined. The three-stage external compression method includes the first stage compression surface (1), the second stage compression surface (2) and the third stage compression surface (3) extending from front to back. The third stage compression surface (3) extends into the inner channel of the intake. The one-stage internal compression method is a flat lip mask with one-stage internal compression. 2) The leading edge and lip of the intake are rounded. Based on the position of the shock system under viscous passivation conditions obtained by numerical simulation, with the goal of compressing the shock wave seal and the shock wave shoulder of the lip mask, the length of the first-stage compression surface (1) and the second-stage compression surface (2), the flow direction position of the lip mask (6), and the first intake shoulder ( D The position of ); 3) The average Mach number of the mass flow rate at the throat outlet section (5) M t For high Mach number M h The target is approximately half of the mass flow rate, if the average Mach number is... M t Significantly exceeding high Mach numbers M h If half of the height of the larynx (4) is reduced, the height of the larynx (4) will be decreased. h t Conversely, it increases the height of the larynx (4). h t up to the average Mach number of the mass flow rate. M t With high Mach number M h The deviations between them are within the preset deviation, forming the basic surface scheme of the wide-area air intake; 4) Using the intersection of the second-stage compression surface (2) and the third-stage compression surface (3) as the axis of rotation, the third-stage compression surface (3) is used as the rotation adjustment surface. The back of the third-stage compression surface (3) is hinged to one end of the parallel double connecting rod (12), and the other end of the parallel double connecting rod (12) is hinged to a slider (11). The slider (11) is used to push the parallel double connecting rod (12) to make the third-stage compression surface (3) move closer to or away from the lip cover, thereby adjusting the height of the throat (4) and realizing the adjustment of the contraction ratio in the wide-range intake passage. 5) Rotate the third-stage compression surface (3) clockwise by an angle δ Increasing the height of the throat (4) enables a wide-range air intake with low Mach number. M l Numerical simulation was used to obtain the average Mach number of the mass flow rate at the throat outlet section (5). M t The location of the low Mach number lip shock (13), and the Mach number averaged by mass flow rate. M t for low Mach number M l The target is approximately half of the mass flow rate, if the average Mach number is... M t Significantly exceeding low Mach numbers M l If the mass flow rate is half of the average Mach number, then the height of the throat (4) is reduced; conversely, if the mass flow rate is half of the average Mach number, then the height of the throat (4) is increased until the average Mach number of the mass flow rate is reached. M t With low Mach number M l The deviation is within the preset deviation; 6) Based on the position of the low Mach number lip shock wave (13), the third-stage compression surface (3) is redesigned, and an inflection point is added in the middle of the compression surface to construct the shoulder of the second air intake. G ), forming a three-stage compression surface with a shoulder (15), the second intake shoulder ( G Located on the low Mach number lip shock wave (13), the specific location is determined according to the equal expansion angle of the low Mach number shoulder and the expansion angle of the high Mach number shoulder. Thus, a preliminary scheme for a wide-area intake with stable control of the double-shoulder wave-absorbing flow field is formed. 7) For the preliminary scheme of wide-area inlet for stable control of the wave-absorbing flow field of the double shoulders, numerical simulations of high Mach number and low Mach number were completed to obtain the position of the lip shock wave under the double shoulder profile and the Mach number of the throat outlet section (5). The high Mach number lip shock wave (7) hits the first inlet shoulder exactly ( D At point 13, the low Mach number shock wave from the lip mask hit the shoulder of the second air intake. G Adjust the position of the inflection point of the third-stage compression surface (3) and the height of the throat (4) for the target; 8) Employ cubic Bézier curves (16) to enhance the shoulder of the second air intake ( G The expansion wave-damping effect of the third-order compression surface (3) is respectively located at the midpoint of the two straight line segments ( ). H, I (13) is the tangent endpoint. By changing the length coefficient of the endpoint of the Bezier curve and adjusting the Bezier curve, it can be rapidly deflected at the low Mach number lip shock wave.

2. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The high Mach number is taken as the upper limit of the working Mach number range, but does not exceed Mach number 7.

0.

3. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The deflection angles of the first-stage compression surface and the second-stage compression surface are within 6°.

4. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The principle of sealing the compression shock wave is to design the first-stage compression shock wave (10) and the second-stage compression shock wave (9) at Mach number to hit the inlet lip.

5. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The principle of shock wave dissipation at the shoulder of the lip mask is that the high Mach number lip mask shock wave (7) hits the intersection of the third compression surface (3) and the throat surface (4).

6. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The length of the larynx is the height of the larynx. h t 1 to 3 times.

7. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The low Mach number is the lower limit of the working Mach number range, but not lower than Mach number 2.

5.

8. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The low Mach number of the wide-range air intake M l The numerical simulation was completed under the condition that the approximate position of the low Mach number lip shock wave (13) hitting the third compression surface (3) was determined based on the oblique shock wave relationship, and the suction groove (14) was designed.

9. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 1, characterized in that, The low Mach number shoulder expansion angle is an acute angle formed by two straight line segments of the third-stage compression surface with an inflection point, and is not less than 6°; the high Mach number shoulder expansion angle is an acute angle formed by the tail end of the third-stage compression surface with an inflection point and the throat, and is not less than 6°.

10. The wide-area air intake design method based on the stable control of the double-shoulder wave-damping flow field according to claim 9, characterized in that, In step (6), moving the shoulder (G) point of the second intake along the low Mach number lip shock wave (13) can simultaneously change the shoulder expansion angle corresponding to the high and low Mach numbers. θ l and θ h ， The shoulder of the second air intake is determined according to the equal expansion angles of the shoulder at high and low Mach numbers. G The position of ) θ l = θ h .

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