A method for counter-designing an optimal coupling shock wave system in a binary mixed compression inlet

Abstract

This invention discloses a reverse design method for the optimal coupling shock wave system of internal and external compression in a two-dimensional mixed-pressure inlet, comprising the following steps: S1, assigning initial values ​​to known design parameters; S2, estimating the total turning angle of external compression and obtaining the corresponding total turning angle of internal compression; S3, using the design parameters obtained in steps S1 and S2, employing the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method to design the optimal shock wave system for external compression, obtaining the external compression outlet flow field parameters; S4, using the design parameters obtained in steps S1-S3, employing the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method to design the optimal shock wave system for internal compression, obtaining the internal compression outlet flow field parameters; S5, determining whether the internal compression outlet Mach number obtained in step S4 meets the standard. If it does, the design ends; otherwise, steps S2-S4 are repeated until the internal compression outlet Mach number meets the standard. This invention achieves automatic optimization of the optimal coupling shock wave system of internal and external compression in reverse design, with a simple process and clear physical meaning.

Description

Technical Field

[0001] This invention relates to the field of air intake design and aircraft airframe / propulsion integration technology, and in particular to a reverse design method for optimal internal and external compression coupling shock wave system of a two-dimensional mixed-pressure air intake. Background Technology

[0002] The two-dimensional mixed-pressure inlet is one of the most widely used supersonic / hypersonic inlets. Its design includes both external and internal compression, and using a series of oblique shock waves to decelerate and pressurize the incoming flow is the most effective compression method. The forward design problem of inlet compression using a series of oblique shock waves refers to designing the optimal shock system (corresponding to the maximum total pressure recovery coefficient) given the incoming flow conditions and solving for the inlet outlet parameters. However, a more interesting technical problem in design is the inverse design problem of global optimization of the inlet, that is: given the incoming flow conditions and outlet parameters of the inlet, the goal is to design the optimal shock system. This problem can be specifically described as follows:

[0003] Given the parameters of the incoming static pressure, static temperature, Mach number, and flow direction angle of the intake duct, and specifying the Mach number and flow direction angle of the outlet airflow of the intake duct, as well as the number of shock waves for the internal and external compression of the intake duct, a globally optimal shock wave system design is performed for the two-dimensional mixed-pressure intake duct to maximize the total pressure recovery coefficient of the entire compression system.

[0004] Oswatitsch's equal-intensity shock wave theory is an important principle for designing the optimal shock wave system for air intakes. This theory states that for an air intake employing a series of shock wave compressions, the total pressure recovery coefficient of the shock wave system is maximized when the normal Mach number of the wavefront of each oblique shock wave is equal; this shock wave system is called the optimal shock wave system.

[0005] In existing technologies, the study "Performance Research of Hypersonic Two-Dimensional Inlet under Different Angles of Attack" employs a decoupled design technology for the internal and external compression of a two-dimensional mixed-pressure inlet. While the external compression utilizes an optimal shock system design, the internal compression is not mentioned. Its internal and external compression are decoupled, not coupled, and lack automatic optimization capabilities. Furthermore, this design method continuously advances downstream by setting upstream parameters (primarily shock parameters such as compression angle and shock angle) to ultimately obtain all downstream parameters (the final parameters obtained in the paper are the Mach number and azimuth angle after the entire compression process). This is essentially a "forward design" method, which cannot account for situations where the inlet outlet azimuth angle is not zero. Moreover, the design has significant mathematical implications but limited practical application. Summary of the Invention

[0006] This invention aims to provide a reverse design method for the optimal coupling shock wave system of internal and external compression in a binary mixed-pressure intake. It realizes the reverse design of the optimal coupling shock wave system of internal and external compression automatically, and the process is simple and the physical meaning is clear.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A reverse design method for the optimal coupling shock wave system between the inner and outer compression sides of a two-dimensional mixed-pressure inlet includes the following steps:

[0009] S1. Assign initial values ​​to the known design parameters;

[0010] S2. Estimate the total external compression turning angle and obtain the corresponding total internal compression turning angle;

[0011] S3. Using the design parameters obtained from steps S1 and S2, the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method are used to design the optimal shock wave system for the external compression, and the external compression outlet flow field parameters are obtained.

[0012] S4. Using the design parameters obtained from steps S1-S3, the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method are used to design the optimal shock wave system for the internal compression, and the internal compression outlet flow field parameters are obtained.

[0013] S5. Determine whether the Mach number of the internal compression outlet obtained in step S4 meets the standard. If it does, end the design. Otherwise, repeat steps S2-S4 until the Mach number of the internal compression outlet meets the standard.

[0014] Furthermore, the initial design parameters for step S1 include the number of oblique shock wave systems compressed inside and outside the intake duct, the incoming flow parameters of the intake duct, and the outlet parameters of the intake duct. The incoming flow parameters of the intake duct include static pressure, static temperature, Mach number, azimuth angle, total pressure, and total temperature. The outlet parameters of the intake duct include the outlet Mach number and the outlet azimuth angle.

[0015] Furthermore, in step S2, the total internal compression turning angle is equal to the difference between the total external compression turning angle and the angle difference between the inlet and outlet directions of the intake manifold.

[0016] Furthermore, in step S3, the optimal shock system design for external compression is specifically as follows:

[0017] S31, Set initial values ​​for the exit Mach number prediction of the external compression wave system of the intake duct;

[0018] S32. Based on the exit Mach number of the externally compressed shock system, calculate the static temperature ratio before and after the externally compressed shock system.

[0019] S33. Based on the static temperature ratio before and after the externally compressed shock wave system, calculate the static temperature ratio of each externally compressed shock wave.

[0020] S34. Based on the static temperature ratio of each shock wave under external compression, the normal Mach number of the wavefront of each shock wave under external compression is obtained.

[0021] S35. Based on the normal Mach number of each shock wave in external compression, obtain the shock wave angle, compression turning angle and backflow field parameters of each shock wave.

[0022] S36. Superimpose and calculate the compression turning angle of each shock wave to obtain the total external compression turning angle corresponding to the estimated exit Mach number;

[0023] S37. Compare the total external compression turning angle obtained in step S36 with the total external compression turning angle estimated in step S2. If the difference is within the error range, the design of the optimal external compression shock system is completed. Otherwise, repeat steps S31-S37 until the difference is within the error range.

[0024] Furthermore, in step S4, the optimal shock system design for internal compression is specifically performed as follows:

[0025] S41, Set initial values ​​for the exit Mach number prediction of the compression wave system in the intake duct;

[0026] S42. Based on the exit Mach number of the internally compressed shock system, the static temperature ratio before and after the internally compressed shock system is obtained.

[0027] S43. Based on the static temperature ratio before and after the internally compressed shock wave system, the static temperature ratio of each internally compressed shock wave is obtained.

[0028] S44. Based on the static temperature ratio of each shock wave in internal compression, the normal Mach number of the wavefront of each shock wave in internal compression is obtained.

[0029] S45. Based on the normal Mach number of each shock wave in the internal compression, obtain the shock wave angle, compression turning angle and backflow field parameters of each shock wave.

[0030] S46. Superimpose and calculate the compression turning angles of each shock wave to obtain the total internal compression turning angle corresponding to the estimated exit Mach number.

[0031] S47. Compare the total internal compression turning angle obtained in step S46 with the total internal compression turning angle calculated in step S2. If the difference is within the error range, the design of the optimal internal compression shock system is completed. Otherwise, repeat steps S41-S47 until the difference is within the error range.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) This invention uses Oswatitsch's equal intensity wave distribution theory multiple times, which not only achieves the optimal shock wave system design for external compression and internal compression, but also maximizes the total pressure recovery coefficient of the entire compression system, thus achieving a high-performance intake design.

[0034] (2) This invention is an automatic optimization method for the inverse design of the optimal coupled shock wave system for internal and external compression. On the one hand, given the parameters as incoming flow parameters, the number of internal and external compression oblique shock wave systems, and inlet outlet parameters, all upstream wave systems and flow field parameters are designed, which is a typical inverse design method. On the other hand, through a mathematical process of prediction-correction-iteration, an external compression total turning angle is first predicted, and an outlet Mach number is obtained through the design of the optimal shock wave system. The difference between the outlet Mach number and the specified value is compared, and the total turning angle is repeatedly corrected until the difference is within the error range. This is a typical automatic optimization process for the optimal shock wave system for internal and external compression.

[0035] (3) This invention can be applied to situations where the air intake outlet direction angle is not zero, thus expanding its application range;

[0036] (4) This invention provides a novel analytical solution to the problem “Given the exit Mach number, find the optimal shock system for external or internal compression”;

[0037] (5) This invention provides a novel prediction-correction-iteration solution for the problem “Given the total turning angle, find the optimal shock system for external or internal compression”;

[0038] (6) This invention provides a complete prediction-correction-iteration solution for the problem “Given the incoming Mach number, the outlet Mach number, and the outlet direction angle of the two-dimensional mixed-pressure intake, find the optimal shock wave system for the entire intake”. Attached Figure Description

[0039] Figure 1 This is a flowchart of an inverse design method for the optimal coupling shock wave system between the inner and outer compression sides of a binary mixed-pressure intake, provided by an embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of the oblique shock wave model provided in an embodiment of the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0042] like Figure 1 and Figure 2 The method shown is an inverse design method for the optimal coupling shock wave system between the inner and outer compression sides of a two-dimensional mixed-pressure inlet, comprising the following steps:

[0043] S1. Assign initial values ​​to the known design parameters;

[0044] Specifically, for high-speed planar two-dimensional mixed-pressure inlet, an inverse design method for optimal coupling shock wave systems of internal and external compression is established. The initial design parameters include the number of oblique shock wave systems for internal and external compression of the inlet, the inlet flow parameters, and the inlet outlet parameters. The inlet flow parameters include static pressure, static temperature, Mach number, azimuth angle, total pressure, and total temperature. The outlet parameters include the outlet Mach number and the outlet azimuth angle. Both internal and external compression of the inlet use oblique shock waves, and the number of shock wave systems is known.

[0045] S2. Estimate the total external compression turning angle and obtain the corresponding total internal compression turning angle;

[0046] Specifically, estimate the total external compression turning angle and obtain the corresponding total internal compression turning angle from the angle difference between the inlet and outlet directions of the intake. The geometric relationship is: incoming flow direction angle + total external compression turning angle - total internal compression turning angle = outlet direction angle; that is: total internal compression turning angle = incoming flow direction angle + total external compression turning angle - outlet direction angle = total external compression turning angle - (outlet direction angle - incoming flow direction angle) = total external compression turning angle - (difference between inlet and outlet directions).

[0047] S3. Using the design parameters obtained from steps S1 and S2, the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method are used to design the optimal shock wave system for the external compression, and the external compression outlet flow field parameters are obtained.

[0048] S4. Using the design parameters obtained from steps S1-S3, the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method are used to design the optimal shock wave system for the internal compression, and the internal compression outlet flow field parameters are obtained.

[0049] Specifically, step S3: Estimate the exit Mach number of the external compression, and solve for the normal Mach number of the wavefront of each shock wave. According to the theory of oblique shock waves:

[0050] T2 * / T1 * =1 (1)

[0051] Among them, T2 * T1 is the total temperature of the flow field behind the first shock wave. * The total temperature of the incoming flow (hereinafter the same) means that the shock wave is an adiabatic process, so the total temperature of the entire external compression remains constant, and the total temperature of the outlet is equal to the total temperature of the incoming flow:

[0052]

[0053] in, This refers to the total temperature at the outlet (the same applies below). The Mach number at the outlet is Ma. N+1 Since this has already been estimated, the static temperature at the outlet can be easily calculated:

[0054]

[0055] Among them, T N+1 Here, γ is the outlet static temperature, and γ is the specific heat ratio (the same applies below). Dividing the outlet static temperature by the incoming static temperature yields the static temperature ratio for the entire external compression. Furthermore, since the static temperature ratio of an oblique shock wave is only a function of the wavefront normal Mach number:

[0056]

[0057] Where T2 is the static temperature of the flow field behind the first shock wave, and T1 is the static temperature of the incoming flow (the same applies below). According to Oswatitsch's equal intensity theory, the normal Mach number of each shock front is equal, therefore the static temperature ratio of each shock wave is equal (both are functions of the normal Mach number of the first shock front):

[0058]

[0059] Clearly, the overall static temperature ratio of external compression is simply the Nth power of the static temperature ratio of each shock wave (where N is the number of shock waves in external compression):

[0060]

[0061] Therefore, the static temperature ratio generated by each shock wave can be calculated as the Nth root of the static temperature ratio of the entire external compression. This gives the static temperature ratio of each shock wave:

[0062]

[0063] Will Substitute the value into formula (4) to solve for the value of . By discarding unreasonable roots and taking the square root of the reasonable roots, it is easy to obtain the normal Mach number of the wavefront for each shock wave.

[0064] Then, the shock angle, compression turning angle, and backflow field parameters of each shock wave are obtained by using the wavefront normal Mach number of each shock wave.

[0065] For the first oblique shock wave, the shock angle can be calculated based on the incoming Mach number and the normal Mach number, i.e.:

[0066]

[0067] Where Ma1 is the incoming Mach number, Ma 1n Let be the normal Mach number, and β be the shock angle (the same applies below). Therefore, the compression angle can be calculated, i.e.:

[0068]

[0069] Where δ is the compression turning angle. The waveback Mach number can be obtained from the following formula:

[0070]

[0071] Where Ma2 is the Mach number behind the wave. The hydrostatic pressure behind the wave can be calculated using the following formula:

[0072]

[0073] Where p1 is the incoming static pressure and p2 is the post-wave static pressure.

[0074] In this way, we obtain the shock wave angle, compression turning angle, post-wave Mach number, direction angle, and post-wave flow field parameters of the first shock wave.

[0075] The Mach number and azimuth angle behind the first shock wave are the same as the Mach number and azimuth angle before the second shock wave. The back-wave flow field parameters of the first shock wave are the same as the front-wave parameters of the second shock wave. Applying the same process to the second shock wave yields its shock angle, compression inflection angle, back-wave Mach number, azimuth angle, and back-wave flow field parameters. Continuing the calculations until all wave systems of external compression are solved, we obtain the Mach number, azimuth angle, and outlet flow field parameters after external compression ends.

[0076] The total airflow turning angle corresponding to the previously estimated exit Mach number is obtained by superimposing the compression turning angles of all shock waves.

[0077] Using a prediction-correction-iteration method, the calculated total airflow turning angle after external compression is compared with the predicted total airflow turning angle. If the difference between the two is large, a correction method is used for correction, and the correction is automatically iterated until the difference is within the error range. In this way, the optimal shock wave system for external compression at a specified total turning angle is obtained.

[0078] It should be noted that the solution process for the optimal shock system design of internal compression is similar to that of the optimal shock system design of external compression. If the Mach number and direction angle at the end of external compression are regarded as the incoming Mach number and direction angle, and the oblique shock number and total turning angle of internal compression are regarded as the oblique shock number and total turning angle of external compression, then the two processes are consistent. Therefore, the process of designing the optimal shock system of internal compression will not be described again.

[0079] S5. Determine whether the Mach number of the internal compression outlet obtained in step S4 meets the standard. If it does, end the design. Otherwise, repeat steps S2-S4 until the Mach number of the internal compression outlet meets the standard.

[0080] Specifically, using the prediction-correction-iteration method, the Mach number after the internal compression ends, obtained by prediction, is compared with the specified exit Mach number. If the difference between the two is greater than the specified error, automatic iterative correction is performed until the difference between the two is within the specified error range. In this way, the total turning angle of external compression and internal compression and all the backflow field parameters are obtained.

[0081] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific structures and / or characteristics in the solutions are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A reverse design method for the optimal coupling shock wave system between the inner and outer compression sides of a binary mixed-pressure inlet, characterized in that, Includes the following steps: S1. Assign initial values ​​to the known design parameters; S2. Estimate the total external compression turning angle and obtain the corresponding total internal compression turning angle; S3. Using the design parameters obtained from steps S1 and S2, the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method are used to design the optimal shock wave system for the external compression, and the external compression outlet flow field parameters are obtained. S4. Using the design parameters obtained from steps S1-S3, the Oswatitsch equal-intensity shock wave theory and the prediction-correction-iteration method are used to design the optimal shock wave system for the internal compression, and the internal compression outlet flow field parameters are obtained. S5. Determine whether the internal compression outlet Mach number obtained in step S4 meets the standard. If it does, end the design. Otherwise, repeat steps S2-S4 until the internal compression outlet Mach number meets the standard. The initial design parameters for step S1 include the number of oblique shock wave systems compressed inside and outside the intake duct, the incoming flow parameters of the intake duct, and the outlet parameters of the intake duct. The incoming flow parameters of the intake duct include static pressure, static temperature, Mach number, azimuth angle, total pressure, and total temperature. The outlet parameters of the intake duct include the outlet Mach number and the outlet azimuth angle. In step S2, the total internal compression turning angle is equal to the difference between the total external compression turning angle and the angle difference between the inlet and outlet directions of the intake manifold. In step S3, the optimal shock system design for external compression is performed as follows: S31, Set initial values ​​for the exit Mach number prediction of the external compression wave system of the intake duct; S32. Based on the exit Mach number of the externally compressed shock system, calculate the static temperature ratio before and after the externally compressed shock system. S33. Based on the static temperature ratio before and after the externally compressed shock wave system, calculate the static temperature ratio of each externally compressed shock wave. S34. Based on the static temperature ratio of each shock wave under external compression, the normal Mach number of the wavefront of each shock wave under external compression is obtained. S35. Based on the normal Mach number of each shock wave in external compression, obtain the shock wave angle, compression turning angle and backflow field parameters of each shock wave. S36. Superimpose and calculate the compression turning angle of each shock wave to obtain the total external compression turning angle corresponding to the estimated exit Mach number; S37. Compare the total external compression angle obtained in step S36 with the total external compression angle estimated in step S2. If the difference is within the error range, the design of the optimal external compression shock system is completed. Otherwise, repeat steps S31-S37 until the difference is within the error range. In step S4, the optimal shock system design for internal compression is performed as follows: S41, Set initial values ​​for the exit Mach number prediction of the compression wave system in the intake duct; S42. Based on the exit Mach number of the internally compressed shock system, the static temperature ratio before and after the internally compressed shock system is obtained. S43. Based on the static temperature ratio before and after the internally compressed shock wave system, the static temperature ratio of each internally compressed shock wave is obtained. S44. Based on the static temperature ratio of each shock wave in internal compression, the normal Mach number of the wavefront of each shock wave in internal compression is obtained. S45. Based on the normal Mach number of each shock wave in the internal compression, obtain the shock wave angle, compression turning angle and backflow field parameters of each shock wave. S46. Superimpose and calculate the compression turning angles of each shock wave to obtain the total internal compression turning angle corresponding to the estimated exit Mach number. S47. Compare the total internal compression turning angle obtained in step S46 with the total internal compression turning angle calculated in step S2. If the difference is within the error range, the design of the optimal internal compression shock system is completed. Otherwise, repeat steps S41-S47 until the difference is within the error range.

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