A subsonic scramjet engine inlet structure and determination method

Abstract

This invention relates to an inlet structure and determination method for a subsonic and scramjet engine. The outer compression section of the inlet consists of an outer compression section horizontal plane, a first panel, a second panel, and a third panel. An angled lip is provided at the inlet of the lower end face of the inner compression section. When determining the inlet structure parameters, the design of the subsonic and scramjet engine inlet is combined. Only the inlet Mach number needs to be determined to automatically identify and select the appropriate ramjet engine inlet geometry determination process, ultimately outputting the optimal inlet geometry that meets the design requirements. This invention enables rapid two-dimensional inlet structure design for subsonic and scramjet engines and provides optimized shape and performance parameters, laying the foundation for subsequent overall propulsion performance analysis of the ramjet engine.

Description

Technical Field

[0001] This invention belongs to the field of high-speed aircraft ramjet engine design technology, and relates to an inlet structure and determination method for a subsonic and scramjet engine. Background Technology

[0002] Hypersonic vehicles refer to aircraft with flight speeds exceeding Mach 5. They can significantly reduce the time required for intercontinental transport of personnel and cargo, and can also be used as hypersonic weapons to quickly strike long-range targets, making them a current and future research hotspot in the aerospace field. Hypersonic cruise vehicles are a typical example of hypersonic vehicles and have received widespread attention from countries around the world. Research shows that when the Mach number is less than 3, turbojet engines outperform ramjet engines; when the Mach number is greater than 3, ramjet engines outperform turbojet engines. Therefore, the propulsion systems of hypersonic cruise vehicles generally employ subsonic / scramjet engines.

[0003] As the primary propulsion system for hypersonic cruise vehicles, the technological level of ramjet engines can significantly impact the development progress of these vehicles. A ramjet engine can be broadly divided into an air intake, combustion chamber, and exhaust nozzle. The air intake compresses air, the combustion chamber mixes and combusts air and fuel, and the exhaust nozzle expands and expels high-energy gases to obtain kinetic energy. The ramjet engine air intake can be further divided into an outer compression section, an inner compression section, and an isolation section, all composed of multiple wedge surfaces. The outer compression section pre-compresses the incoming airflow using several oblique shock waves, providing the intake with a sufficiently high flow field quality and the required flow rate. The inner compression section further compresses the airflow using shock waves, ensuring that the Mach number and pressure meet design specifications, while simultaneously aligning the airflow direction with the engine axis.

[0004] The performance of a ramjet engine's air intake directly affects whether the engine can operate normally and generate sufficient thrust, and these performance characteristics are closely related to the geometry of the air intake. As a crucial component of hypersonic cruise vehicles, research on ramjet engine air intakes is of paramount importance.

[0005] Existing ramjet engine inlet configuration designs mostly employ numerical methods, which involve a very large amount of multi-stage iterative calculations, consuming a lot of time and reducing the overall efficiency of multidisciplinary optimization design of aircraft. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a structure and determination method for the inlet of a subsonic and scramjet engine. After the design inlet Mach number is determined, the two-dimensional inlet shape design of the subsonic and scramjet engines is carried out quickly, and the optimized shape and performance parameters are determined, providing a structural basis for the subsequent overall propulsion performance analysis of the ramjet engine.

[0007] The solution of this invention is: an intake structure for a subsonic and supersonic ramjet engine, comprising an outer compression section and an inner compression section. The leeward side of the outer compression section is a horizontal plane, and the windward side of the outer compression section is formed by sequentially splicing a first panel, a second panel, and a third panel. The third panel is connected to the upper end face of the inner compression section, and a lip with an angle is provided at the inlet of the lower end face of the inner compression section. The acute angle formed by the plane of the first panel and the horizontal plane of the outer compression section is the first wedge angle, the acute angle formed by the plane of the second panel and the plane of the first panel is the second wedge angle, the acute angle formed by the plane of the third panel and the plane of the second panel is the third wedge angle, the acute angle formed by the plane of the lip and the lower end face of the inner compression section is the lip deflection angle, and the acute angle formed by the plane of the third panel and the upper end face of the inner compression section is the fifth deflection angle.

[0008] When the incoming flow velocity exceeds the preset Mach number threshold, the airflow forms the first oblique shock wave after passing the first wedge angle, the second oblique shock wave after passing the second wedge angle, the third oblique shock wave after passing the third wedge angle, the fourth oblique shock wave after passing the lip deflection angle, and the fifth oblique shock wave after passing the fifth deflection angle. For the intake of a subsonic ramjet engine, after the fifth oblique shock wave, a normal shock wave is formed in the compression section inside the intake, which reduces the airflow velocity to subsonic speed.

[0009] Furthermore, when the design value of the inlet Mach number of the ramjet engine is not greater than the limit value, the determination method of the inlet geometry parameters for the subsonic ramjet mode includes the following process:

[0010] Step 1: Input the boundary conditions of the intake duct of the sub-gas ramjet engine, including the minimum inlet Mach number of the intake duct, the design value of the inlet Mach number of the intake duct, the minimum value of the first wedge angle, the minimum value of the second wedge angle, the minimum value of the third wedge angle, the minimum lip deflection angle, and the threshold value of the total pressure recovery coefficient of the first intake duct; arbitrarily select the longitudinal section of the intake duct structure as the first section, and give the coordinates of the intersection point of the line formed by the first panel and the leeward side of the outer compression section with the first section, and the coordinates of the intersection point of the inlet boundary of the lip with the first section;

[0011] Step 2: Define the value ranges for the first wedge angle, second wedge angle, third wedge angle, and lip deflection angle, and uniformly select values ​​within their respective ranges;

[0012] Step 3: Within the range of values ​​in Step 2, give a set of variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle. Calculate the variable value for the fifth deflection angle based on the given variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle.

[0013] Step 4: Starting with the first oblique shock wave, substitute the design value of the inlet Mach number, the first wedge angle, the second wedge angle, the third wedge angle, the lip deflection angle, and the fifth deflection angle obtained in Step 3 into the oblique shock wave formula in sequence, and calculate the shock wave angle, Mach number after the wave, pressure, and density of each oblique shock wave. Based on the shock wave angle, Mach number after the wave, and pressure of each oblique shock wave, calculate the total pressure recovery coefficient before and after each oblique shock wave.

[0014] Step 5: Based on the Mach number, pressure, and density behind the fifth oblique shock wave, calculate and output the Mach number, pressure, and density behind the normal shock wave using the normal shock wave formula, and calculate the total pressure recovery coefficient before and after the normal shock wave.

[0015] Step 6: Based on the product of the total pressure recovery coefficients before and after each oblique shock wave and the total pressure recovery coefficients before and after each normal shock wave, obtain the total pressure recovery coefficient of the inlet and output the total pressure recovery coefficient of the inlet.

[0016] Step 7: Determine whether the total pressure recovery coefficient of the intake duct in Step 6 is greater than the threshold of the total pressure recovery coefficient of the first intake duct. If yes, proceed to Step 8; otherwise, jump to Step 3 to start the next iteration.

[0017] Step 8: Replace the intake inlet Mach number design value input in Step 4 with the minimum intake inlet Mach number, and repeat Steps 4 to 6 to calculate the intake total pressure recovery coefficient corresponding to the minimum inlet Mach number.

[0018] Step 9: If the total pressure recovery coefficient of the intake duct corresponding to the minimum inlet Mach number is zero, jump to Step 3 to start the next iteration; if it is not zero, assign the current total pressure recovery coefficient of the intake duct to the threshold of the first total pressure recovery coefficient of the intake duct.

[0019] Step 10: Repeat steps 3 through 9. After iteration, output the threshold value of the first intake total pressure recovery coefficient that is the largest within the range of variable values ​​in step 2. At the same time, output the corresponding variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle of the intake. Based on the coordinates of the intersection of the line formed by the first panel and the leeward side of the outer compression section with the first profile, the coordinates of the intersection of the inlet boundary of the lip with the first profile, and the constraint conditions that the oblique shock wave can form, use trigonometric function relationships to determine the coordinates of the intersection of the line formed by the second panel and the first panel with the first profile, the coordinates of the intersection of the line formed by the second panel and the third panel with the first profile, the coordinates of the intersection of the line formed by the upper end face of the third panel and the inner compression section with the first profile, and the coordinates of the intersection of the line formed by the lip and the lower end face of the inner compression section with the first profile.

[0020] Furthermore, the design value of the inlet Mach number is the cruise Mach number of the high-speed aircraft; the limiting value is the mode transition value from the subsonic ramjet mode to the scramjet mode.

[0021] Furthermore, when the design value of the inlet Mach number of the ramjet engine is not greater than the limit value, the determined inlet outlet airflow parameters of the sub-fuel ramjet mode include: the first inlet outlet Mach number, the first outlet pressure, and the first outlet density; wherein, the first inlet outlet Mach number is the normal shock wave back Mach number corresponding to the largest first inlet total pressure recovery coefficient threshold in step ten, the first outlet pressure is the normal shock wave back pressure corresponding to the largest first inlet total pressure recovery coefficient threshold in step ten, and the first outlet density is the normal shock wave back density corresponding to the largest first inlet total pressure recovery coefficient threshold.

[0022] Furthermore, the calculation of the fifth deflection angle variable value described in step three is as follows: the fifth deflection angle variable value is equal to the sum of the first wedge angle, second wedge angle, and third wedge angle variable values ​​minus the lip deflection angle variable value.

[0023] Furthermore, in step four, when calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient of the first oblique shock wave using the oblique shock wave relationship, the inputs are the design value of the inlet Mach number and the variable value of the first wedge angle; when calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient of the second oblique shock wave, the inputs are the post-shock Mach number of the first oblique shock wave and the variable value of the second wedge angle; when calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient of the third oblique shock wave... When calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient before and after the oblique shock wave, the inputs are the Mach number after the second oblique shock wave and the third wedge angle variable value; when calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient before and after the oblique shock wave of the fourth oblique shock wave, the inputs are the Mach number after the third oblique shock wave and the lip deflection angle variable value; when calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient before and after the oblique shock wave of the fifth oblique shock wave, the inputs are the Mach number after the fourth oblique shock wave and the fifth deflection angle variable value.

[0024] Furthermore, the calculation method for the shock angle of each oblique shock wave in step four is as follows:

[0025]

[0026] Where, β i , i = 1, 2, ..., 5 correspond to the shock angles of the i-th oblique shock wave; θ i i = 1, 2, ..., 5 correspond to the variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle obtained in each step of step three, respectively; Ma i ,i=1,2,…,5 correspond to the design value of the inlet Mach number, the Mach number behind the first oblique shock wave, the Mach number behind the second oblique shock wave, the Mach number behind the third oblique shock wave, and the Mach number behind the fourth oblique shock wave, respectively; γ is the specific heat ratio, which is taken as 1.4 in standard atmosphere.

[0027] Furthermore, when the design value of the inlet Mach number of the ramjet engine exceeds the limit, the determination method for the inlet geometry parameters of the scramjet mode includes the following process:

[0028] S1. Input the design value of the Mach number at the inlet of the scramjet engine, the minimum values ​​of the first wedge angle, the second wedge angle, the third wedge angle, the minimum value of the lip deflection angle, and the threshold value of the total pressure recovery coefficient of the second inlet; arbitrarily select the first section of the inlet structure, and give the coordinates of the intersection point of the line formed by the first panel and the leeward side of the outer compression section with the first section, and the coordinates of the intersection point of the inlet boundary of the lip with the first section;

[0029] S2. Give the range of values ​​for the first wedge angle, second wedge angle, third wedge angle, and lip deflection angle respectively, and take values ​​uniformly within their respective ranges;

[0030] S3. Within the range of values ​​of S2, given a set of variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle, calculate the variable value for the fifth deflection angle based on the given variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle.

[0031] S4. Starting from the first oblique shock wave, substitute the design value of the Mach number at the inlet of the air intake, the three wedge angles, the lip deflection angle, and the fifth deflection angle obtained in S3 into the oblique shock wave formula in turn, and calculate the shock wave angle, Mach number after the wave, pressure, and density of each oblique shock wave. Based on the shock wave angle, Mach number after the wave, and pressure of each oblique shock wave, calculate the total pressure recovery coefficient before and after each oblique shock wave.

[0032] S5. Based on the product of the total pressure recovery coefficients before and after each oblique shock wave, obtain the total pressure recovery coefficient of the inlet. Output the total pressure recovery coefficient of the inlet, the first wedge angle, the second wedge angle, the third wedge angle, the lip deflection angle, the fifth deflection angle variable value obtained in step three, the Mach number after the fifth oblique shock wave, the pressure, and the density.

[0033] S6. Determine whether the total pressure recovery coefficient of the intake duct obtained in S5 is greater than the threshold of the second total pressure recovery coefficient of the intake duct. If so, assign the current total pressure recovery coefficient of the intake duct to the threshold of the second total pressure recovery coefficient of the intake duct. Otherwise, jump to S3 to start the next iteration.

[0034] S7. Repeat S3 to S6. After iteration, output the threshold value of the second intake total pressure recovery coefficient that is the largest within the range of variable S2. At the same time, output the corresponding variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle of the intake. Based on the coordinates of the intersection of the line formed by the first panel and the leeward side of the outer compression section with the first profile, the coordinates of the intersection of the inlet boundary of the lip with the first profile, and the constraint conditions that the oblique shock wave can form, use trigonometric function relationships to determine the coordinates of the intersection of the line formed by the second panel and the first panel with the first profile, the coordinates of the intersection of the line formed by the second panel and the third panel with the first profile, the coordinates of the intersection of the line formed by the third panel and the upper end face of the inner compression section with the first profile, and the coordinates of the intersection of the line formed by the lip and the lower end face of the inner compression section with the first profile.

[0035] Furthermore, the determined inlet outlet airflow parameters for the scramjet mode include: the second inlet outlet Mach number, the second outlet pressure, and the second outlet density; wherein, the second inlet outlet Mach number is the fifth oblique shock wave back Mach number corresponding to the largest second inlet total pressure recovery coefficient threshold in step seven, the second outlet pressure is the fifth oblique shock wave back pressure corresponding to the largest second inlet total pressure recovery coefficient threshold in step seven, and the second outlet density is the fifth oblique shock wave back density corresponding to the largest first inlet total pressure recovery coefficient threshold in step seven.

[0036] The advantages of this invention compared to the prior art are:

[0037] (1) This invention combines the design of the inlet duct of a subsonic ramjet engine with the design of the inlet duct of a supersonic ramjet engine. Only the inlet Mach number needs to be determined to automatically determine and select the corresponding ramjet engine inlet geometry configuration determination process, and finally output the optimal inlet geometry configuration that meets the design requirements.

[0038] (2) The present invention performs a transposition transformation on the θ-β-Ma relation of the oblique shock wave relation, transforming the need to consult charts to determine the β value into a direct solution by solving the equation, making the oblique shock wave relation easier to program and improving the computational efficiency.

[0039] (3) The method of the present invention for determining the geometric configuration of the intake duct of a ramjet engine with a three-wedge external compression section and a lip deflection angle can be extended to the determination of the general intake duct geometry of a ramjet engine with a multi-wedge external compression section. The parameter determination method is simple, easy to expand and easy to integrate. Attached Figure Description

[0040] Figure 1 This is a geometric schematic diagram of the intake duct of a two-dimensional ramjet engine with a wedge-shaped lip deflection angle, as shown in Example 3.

[0041] Figure 2This is a schematic diagram of the airflow field in the intake duct of a two-dimensional ramjet engine with a wedge-shaped lip deflection angle, as shown in Example 3.

[0042] Figure 3 This is a flowchart of the method for determining the inlet parameters of a subsonic and scramjet engine according to an embodiment of the present invention;

[0043] Figure 4 This is a flowchart illustrating the determination of inlet parameters for a sub-gas ramjet engine according to an embodiment of the present invention;

[0044] Figure 5 This is a flowchart illustrating the determination of inlet parameters for a scramjet engine according to an embodiment of the present invention. Detailed Implementation

[0045] The invention will now be further described with reference to the accompanying drawings.

[0046] like Figure 1 As shown, the ramjet engine intake structure of this embodiment includes an outer compression section and an inner compression section. The leeward side of the outer compression section is a horizontal plane, and the windward side of the outer compression section is formed by sequentially splicing a first panel, a second panel, and a third panel. The third panel is connected to the upper end face of the inner compression section, and a lip with an angle is provided at the inlet of the lower end face of the inner compression section. The acute angle formed by the plane of the first panel and the horizontal plane of the outer compression section is the first wedge angle, the acute angle formed by the plane of the second panel and the plane of the first panel is the second wedge angle, the acute angle formed by the plane of the third panel and the plane of the second panel is the third wedge angle, the acute angle formed by the plane of the lip and the lower end face of the inner compression section is the lip deflection angle, and the acute angle formed by the plane of the third panel and the upper end face of the inner compression section is the fifth deflection angle.

[0047] If any longitudinal section of the intake structure is arbitrarily selected as the first section, then the six geometric design points (points 1 to 6) of the ramjet engine intake are as follows: Point 1 is the coordinate of the intersection of the line formed by the first panel and the leeward side of the outer compression section with the first section; Point 2 is the coordinate of the intersection of the line formed by the second panel and the first panel with the first section; Point 3 is the coordinate of the intersection of the line formed by the second panel and the third panel with the first section; Point 4 is the coordinate of the intersection of the line formed by the third panel and the upper end face of the inner compression section with the first section; Point 5 is the coordinate of the intersection of the inlet boundary of the lip with the first section; and Point 6 is the coordinate of the intersection of the line formed by the lip and the lower end face of the inner compression section with the first section.

[0048] like Figure 2As shown, when the incoming flow velocity exceeds a certain Mach number, the airflow forms a first oblique shock wave after passing the first wedge angle, a second oblique shock wave after passing the second wedge angle, a third oblique shock wave after passing the third wedge angle, a fourth oblique shock wave after passing the lip deflection angle, and a fifth oblique shock wave after passing the fifth deflection angle. For a subsonic ramjet engine inlet, after the fifth oblique shock wave, a normal shock wave is formed after passing through the compression section inside the inlet, reducing the airflow velocity to subsonic speed. For a scramjet engine inlet, no normal shock wave is generated.

[0049] like Figure 3 As shown, the method for determining the intake structure of the ramjet engine of the present invention includes the following steps:

[0050] Step 1: Input the design value of the Mach number at the intake of the ramjet engine.

[0051] like Figure 2 As shown, the airflow flowing into the intake duct must pass through five oblique shock waves. For a subsonic ramjet engine, since it needs to decelerate to subsonic speed, it must pass through an additional normal shock wave.

[0052] The design value of the inlet Mach number described in this invention is generally the cruise Mach number of a hypersonic cruise aircraft.

[0053] Step 2: Determine whether the design value of the Mach number at the intake duct is greater than the limit value; the limit value is the mode transition value from subsonic ramjet mode to supersonic ramjet mode.

[0054] Step 3: If the design value of the Mach number at the air intake is not greater than the limit, call the subsonic ramjet engine parameter determination process; otherwise, call the scramjet engine parameter determination process.

[0055] The process for determining the parameters of the sub-steam ramjet engine is as follows: Figure 4 As shown, it includes the following steps:

[0056] Step 1: Input the boundary conditions for the sub-gas turbine ramjet engine inlet, including the minimum inlet Mach number Ma. min-inlet-inflow Design value of Mach number at the air intake (Ma1), minimum value of first wedge angle (θ) 1-min The minimum value of the second wedge angle θ 2-min The minimum value of the third wedge angle θ 3-min Minimum lip deflection angle θ 4-min Threshold σ for total pressure recovery coefficient of the first intake duct max-inlet Given the coordinates of the intersection point (point 1) of the line formed by the first panel and the leeward side of the outer compression section with the first profile, and the coordinates of the intersection point (point 5) of the entrance boundary of the lip with the first profile.

[0057] Step 2: Specify the value ranges for the first wedge angle, second wedge angle, third wedge angle, and lip deflection angle, and uniformly select values ​​within their respective ranges.

[0058] The first wedge angle θ1 ranges from [θ 1-min ,θ 1-max ], will [θ 1-min ,θ 1-max Divide the data into N1 segments, where N1 is a positive integer greater than 1. Then the length Δθ1 of each segment is (θ... 1-max -θ 1-min Let i = 1, ..., N1+1, then the i-th first wedge angle θ 1(i) =θ 1-min +△θ1(i-1); the range of the second wedge angle θ2 is [θ 2-min ,θ 2-max ], will [θ 2-min ,θ 2-max Divide the data into N2 segments, where N2 is a positive integer greater than 1. Then the length of each segment, Δθ2, is (θ... 2-max -θ 2-min Let j = 1, ..., N2+1, then the j-th second wedge angle θ 2(j) =θ 2-min +△θ2(j-1); The range of the third wedge angle θ3 is [θ 3-min ,θ 3-max ], will [θ 3-min ,θ 3-max Divide the data into N3 segments, where N3 is a positive integer greater than 1. Then the length of each segment, Δθ3, is (θ... 3-max -θ 3-min Let k = 1, ..., N3+1, then the kth third wedge angle θ 3(k) =θ 3-min +△θ3(k-1); the range of the lip deflection angle θ4 is [θ 4-min ,θ 4-max ], will [θ 4-min ,θ 4-max Divide the data into N4 segments, where N4 is a positive integer greater than 1. Then the length of each segment, Δθ4, is (θ... 4-max -θ 4-min Let l = 1, ..., N4+1, then the l-th lip deflection angle θ 4(l) =θ 4-min +△θ4(l-1).

[0059] Step 3: Within the range of values ​​in Step 2, give a set of variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle. Calculate the variable value for the fifth deflection angle based on the given variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle.

[0060] The first wedge angle is θ. 1(i) The second wedge angle is θ. 2(j) The third wedge angle is θ. 3(k) The lip deflection angle is taken as θ. 4(l) Therefore, the value of the fifth deflection angle variable is: θ5 = θ 1(i) +θ 2(j) +θ 3(k) -θ 4(l) .

[0061] During the iteration process, step three updates only one angle variable value in each iteration to ensure that all possible combinations of the five angle variables are covered.

[0062] Step 4: Starting with the first oblique shock wave, substitute the design value of the inlet Mach number, the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle obtained in Step 3 into the oblique shock wave formula in sequence to calculate the shock wave angle, Mach number after the wave, pressure, and density of each oblique shock wave. Based on the shock wave angle, Mach number after the wave, and pressure of each oblique shock wave, calculate the total pressure recovery coefficient before and after each oblique shock wave.

[0063] The oblique shock wave calculation program calculates the shock wave angle β1, post-shock Mach number Ma2, pressure p2, density ρ2, and total pressure recovery coefficient σ before and after the oblique shock wave for the first oblique shock wave. 21 At that time, the inputs are the design value of the inlet Mach number Ma1 and the first wedge angle θ. 1(i) Calculate the shock angle β2, post-shock Mach number Ma3, pressure p3, density ρ3, and total pressure recovery coefficient σ before and after the second oblique shock wave. 32 At that time, the input to the oblique shock wave calculation program is the Mach number Ma2 of the first oblique shock wave and the second wedge angle θ. 2(j) Calculate the shock angle β3, post-shock Mach number Ma4, pressure p4, density ρ4, and total pressure restitution coefficient σ before and after the third oblique shock wave. 43 At that time, the input to the oblique shock wave calculation program is the Mach number Ma3 behind the second oblique shock wave and the third wedge angle θ. 3(j) Calculate the shock angle β4, post-shock Mach number Ma5, pressure p5, density ρ5, and total pressure recovery coefficient σ before and after the fourth oblique shock wave. 54 At that time, the input to the oblique shock wave calculation program is the Mach number Ma4 behind the third oblique shock wave and the lip deflection angle θ. 4(j) Calculate the shock angle β5, Mach number Ma6, pressure p6, density ρ6, and total pressure recovery coefficient σ before and after the fifth oblique shock wave. 65 At that time, the input to the oblique shock wave calculation program is the Mach number Ma5 behind the fourth oblique shock wave and the fifth deflection angle θ5.

[0064] Taking the first oblique shock wave as an example, the solutions for each physical quantity are as follows: Given Ma1, θ 1(i) Let p1 and ρ1 be the incoming flow pressure and ρ1 be the incoming flow density; then Ma2, p2, ρ2, σ 21 The calculation is as follows:

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] In the above formula, γ is the specific heat ratio, which is taken as 1.4 in standard atmosphere. The calculation of β1 will be explained at the end.

[0072] Similarly, after the second oblique shock wave, Ma3, p3, ρ3, σ 32 After the third oblique shock wave, Ma4, p4, ρ4, σ 43 After the fourth oblique shock wave, Ma5, p5, ρ5, σ 54 After the fifth oblique shock wave, Ma6, p6, ρ6, σ 65 The results are obtained from formulas (1) to (6).

[0073] Step 5: Based on the Mach number, pressure, and density behind the fifth oblique shock wave, calculate the Mach number, pressure, and density behind the normal shock wave using the normal shock wave formula, and calculate the total pressure recovery coefficient before and after the normal shock wave.

[0074] Among these, the normal shock wave relation is used to calculate the Mach number Ma7, pressure p7, density ρ7, and total pressure restitution coefficient σ before and after the normal shock wave. 76 Given Ma6, p6, ρ6, then Ma7, p7, ρ7, σ 76 The calculation is as follows:

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] Step Six: Based on the product of the total pressure recovery coefficients before and after each oblique shock wave and the total pressure recovery coefficients before and after each normal shock wave, obtain the total pressure recovery coefficient of the inlet. Output the total pressure recovery coefficient of the inlet, the Mach number at the inlet outlet, the outlet pressure, the outlet density, and the variable values ​​of the first wedge angle, the second wedge angle, the third wedge angle, the lip deflection angle, and the fifth deflection angle obtained in Step Three. Wherein, the inlet outlet Mach number is the Mach number behind the normal shock wave, the outlet pressure is the pressure behind the normal shock wave, and the outlet density is the density behind the normal shock wave. These three parameters serve as the outlet airflow parameters of the inlet.

[0082] Intake total pressure recovery coefficient σ inlet The product of the total pressure recovery coefficients before and after each shock wave is calculated as follows:

[0083] σ inlet =σ 21 σ 32 σ 43 σ 54 σ 65 σ 76 (13)

[0084] The fifth deflection angle θ5 output in each iteration is:

[0085] θ5=θ 1(i) +θ 2(j) +θ 3(k) -θ 4(l) (14)

[0086] Step 7: Determine whether the total pressure recovery coefficient of the intake duct in Step 6 is greater than the threshold of the total pressure recovery coefficient of the first intake duct. If yes, proceed to Step 8; otherwise, jump to Step 3 to start the next iteration.

[0087] Step 8: Replace the intake inlet Mach number design value entered in Step 4 with the minimum intake inlet Mach number. min-inlet-inflow Repeat steps four through six to calculate the intake total pressure recovery coefficient corresponding to the minimum inlet Mach number.

[0088] Step 9: If the total pressure recovery coefficient of the intake duct corresponding to the minimum inlet Mach number is zero, it indicates that the intake duct cannot start at the minimum inlet Mach number. Then, jump to Step 3 to start the next iteration. If it is not zero, assign the current total pressure recovery coefficient of the intake duct to the threshold of the first total pressure recovery coefficient of the intake duct.

[0089] Step 10: Repeat steps 3 to 9. After iteration, output the threshold value of the first intake total pressure recovery coefficient that is the largest within the range of variable values ​​in step 2. At the same time, output the corresponding variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, fifth deflection angle, intake outlet Mach number, outlet pressure, outlet density, and intake inlet Mach number design value.

[0090] Step 11: Based on the constraints of the intersection point (point 1) of the line formed by the first panel and the leeward side of the outer compression section with the first profile, the intersection point (point 5) of the inlet boundary of the lip with the first profile, and the constraint conditions for the formation of oblique shock waves, the intersection point (point 2) of the line formed by the second panel and the first panel with the first profile, the intersection point (point 3) of the line formed by the second panel and the third panel with the first profile, the intersection point (point 4) of the line formed by the upper end face of the third panel and the inner compression section with the first profile, and the intersection point (point 6) of the line formed by the lip and the lower end face of the inner compression section with the first profile are determined using trigonometric function relationships. The optimal intake geometric parameters of the ramjet engine under the design value of the intake Mach number are obtained.

[0091] In addition, in this embodiment, after calculating the shock wave angle and Mach number behind the shock wave using the oblique shock wave relationship in step four, the maximum deflection angle corresponding to the Mach number behind each oblique shock wave is calculated using empirical formulas. It is then determined whether the corresponding deflection angle variable value is less than the corresponding maximum deflection angle, and simultaneously, it is determined whether the Mach number behind the oblique shock wave is greater than the minimum inlet Mach number of the inlet duct. min-inlet-inflow If any of the conditions are not met, the current iteration will be terminated.

[0092] The process of the optimized design of the scramjet engine is as follows: Figure 5 As shown, the steps are as follows:

[0093] Step 1: Input the design value of the Mach number at the inlet of the scramjet engine, the minimum values ​​of the first wedge angle, the second wedge angle, the third wedge angle, the minimum value of the lip deflection angle, and the threshold value of the total pressure recovery coefficient of the second inlet; give the coordinates of the intersection point (point 1) of the line formed by the first panel and the leeward side of the outer compression section with the first profile, and the coordinates of the intersection point (point 5) of the inlet boundary of the lip with the first profile.

[0094] Step 2: Specify the value ranges for the first wedge angle, second wedge angle, third wedge angle, and lip deflection angle, and uniformly select values ​​within their respective ranges.

[0095] Step 3: Within the range of values ​​in Step 2, give a set of variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle. Calculate the variable value for the fifth deflection angle based on the given variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle.

[0096] Step 4: Starting with the first oblique shock wave, substitute the design value of the inlet Mach number, the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle obtained in Step 3 into the oblique shock wave formula in sequence to calculate the shock wave angle, Mach number after the wave, pressure, and density of each oblique shock wave. Based on the shock wave angle, Mach number after the wave, and pressure of each oblique shock wave, calculate the total pressure recovery coefficient before and after each oblique shock wave.

[0097] Step 5: Based on the product of the total pressure recovery coefficients before and after each oblique shock wave, obtain the total pressure recovery coefficient of the inlet. Output the total pressure recovery coefficient of the inlet, the Mach number at the inlet outlet, the outlet pressure, the outlet density, and the variable values ​​of the first wedge angle, the second wedge angle, the third wedge angle, the lip deflection angle, and the fifth deflection angle obtained in Step 3. Among them, the Mach number at the inlet outlet is the Mach number behind the fifth oblique shock wave, the outlet pressure is the pressure behind the fifth oblique shock wave, and the outlet density is the density behind the fifth oblique shock wave. The above three parameters are used as the outlet airflow parameters of the inlet.

[0098] Step 6: Determine whether the total pressure recovery coefficient of the intake duct obtained in Step 5 is greater than the threshold of the second total pressure recovery coefficient of the intake duct. If so, assign the current total pressure recovery coefficient of the intake duct to the threshold of the second total pressure recovery coefficient of the intake duct. Otherwise, jump to Step 3 to start the next iteration.

[0099] Step 7: Repeat steps 3 to 6. After iteration, output the threshold value of the second intake total pressure recovery coefficient that is the largest within the range of variable values ​​in step 2. At the same time, output the corresponding variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, fifth deflection angle, intake outlet Mach number, outlet pressure, outlet density, and intake inlet Mach number design value.

[0100] Step 8: Based on the constraints of the intersection point (point 1) of the line formed by the first panel and the leeward side of the outer compression section with the first profile, the intersection point (point 5) of the inlet boundary of the lip with the first profile, and the constraint conditions for the formation of oblique shock waves, the intersection point (point 2) of the line formed by the second panel and the first panel with the first profile, the intersection point (point 3) of the line formed by the second panel and the third panel with the first profile, the intersection point (point 4) of the line formed by the line formed by the upper end face of the third panel and the inner compression section with the first profile, and the intersection point (point 6) of the line formed by the line formed by the lip and the lower end face of the inner compression section with the first profile are determined using trigonometric function relationships; thus, the optimal intake geometric parameters of the ramjet engine under the design value of the intake Mach number are obtained.

[0101] Regarding the shock angle β i The calculation is explained in detail below: The θ in the oblique shock wave relation is transformed by rearranging terms. i -β i -Ma i The relational expression is transformed into the unknown quantity tanβi Calculate tanβ using Cardan's formula for a cubic equation in one variable. i The value is finally obtained by calculating β using inverse trigonometric functions. i Value; that is, the known deflection angle θ i Wavefront Mach number Ma i Solve the equation to find the shock angle β. i .

[0102] Where, θ i i = 1, 2, ..., 5 correspond to the variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle obtained in each step of step three, respectively; β i , i = 1, 2, ..., 5 correspond to the shock angles of the i-th oblique shock wave obtained from solving the equation each time; Ma i i = 1, 2, ..., 5 correspond to the design value of the inlet Mach number, the Mach number behind the first oblique shock wave, the Mach number behind the second oblique shock wave, the Mach number behind the third oblique shock wave, and the Mach number behind the fourth oblique shock wave, respectively.

[0103] Taking the solution of β1 as an example, the relationship between θ1-β1-Ma1 is as follows:

[0104]

[0105] cotβ1, sin 2 β1,cos2β1 can be expressed in tanβ1 form as follows:

[0106]

[0107]

[0108]

[0109] Substituting equations (16), (17), and (18) into equation (15) and rearranging the terms, we get:

[0110]

[0111] tanβ1 can be obtained using Karl der Quadratic formula, and the shock angle β1 can be calculated using inverse trigonometric functions. When calculating β2, replace Ma1 with Ma2, θ1 with θ2, and β1 with β2 in formulas (15) to (19) to solve. And so on, to obtain β3, β4, and β5.

[0112] The parts of this invention not described in detail are common knowledge to those skilled in the art.

[0113] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for determining the intake structure of a subsonic and scramjet engine, wherein the intake structure of the subsonic and scramjet engine includes an outer compression section and an inner compression section. The leeward side of the outer compression section is a horizontal plane, and the windward side of the outer compression section is formed by sequentially splicing a first panel, a second panel, and a third panel. The third panel is connected to the upper end face of the inner compression section, and a lip with an angle is provided at the inlet of the lower end face of the inner compression section. The acute angle formed by the plane of the first panel and the horizontal plane of the outer compression section is the first wedge angle, the acute angle formed by the plane of the second panel and the plane of the first panel is the second wedge angle, the acute angle formed by the plane of the third panel and the plane of the second panel is the third wedge angle, the acute angle formed by the plane of the lip and the lower end face of the inner compression section is the lip deflection angle, and the acute angle formed by the plane of the third panel and the upper end face of the inner compression section is the fifth deflection angle. When the incoming flow velocity exceeds the preset Mach number threshold, the airflow forms the first oblique shock wave after passing the first wedge angle, the second oblique shock wave after passing the second wedge angle, the third oblique shock wave after passing the third wedge angle, the fourth oblique shock wave after passing the lip deflection angle, and the fifth oblique shock wave after passing the fifth deflection angle. For the intake of a subsonic ramjet engine, after the fifth oblique shock wave, a normal shock wave is formed after passing through the compression section inside the intake, which reduces the airflow velocity to subsonic speed. Its features are, When the design value of the inlet Mach number of the ramjet engine is not greater than the limit value, the determination method of the inlet geometry parameters in the sub-fuel ramjet mode includes the following process: Step 1: Input the boundary conditions of the intake duct of the sub-gas ramjet engine, including the minimum inlet Mach number of the intake duct, the design value of the inlet Mach number of the intake duct, the minimum value of the first wedge angle, the minimum value of the second wedge angle, the minimum value of the third wedge angle, the minimum lip deflection angle, and the threshold value of the total pressure recovery coefficient of the first intake duct. Arbitrarily select a longitudinal section of the intake structure as the first section, and give the coordinates of the intersection of the line formed by the first panel and the leeward side of the outer compression section with the first section, and the coordinates of the intersection of the inlet boundary of the lip with the first section. Step 2: Define the value ranges for the first wedge angle, second wedge angle, third wedge angle, and lip deflection angle, and uniformly select values ​​within their respective ranges; Step 3: Within the range of values ​​in Step 2, give a set of variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle. Calculate the variable value for the fifth deflection angle based on the given variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle. Step 4: Starting with the first oblique shock wave, substitute the design value of the inlet Mach number, the first wedge angle, the second wedge angle, the third wedge angle, the lip deflection angle, and the fifth deflection angle obtained in Step 3 into the oblique shock wave formula in sequence, and calculate the shock wave angle, Mach number after the wave, pressure, and density of each oblique shock wave. Based on the shock wave angle, Mach number after the wave, and pressure of each oblique shock wave, calculate the total pressure recovery coefficient before and after each oblique shock wave. Step 5: Based on the Mach number, pressure, and density behind the fifth oblique shock wave, calculate and output the Mach number, pressure, and density behind the normal shock wave using the normal shock wave formula, and calculate the total pressure recovery coefficient before and after the normal shock wave. Step 6: Based on the product of the total pressure recovery coefficients before and after each oblique shock wave and the total pressure recovery coefficients before and after each normal shock wave, obtain the total pressure recovery coefficient of the inlet and output the total pressure recovery coefficient of the inlet. Step 7: Determine whether the total pressure recovery coefficient of the intake duct in Step 6 is greater than the threshold of the total pressure recovery coefficient of the first intake duct. If yes, proceed to Step 8; otherwise, jump to Step 3 to start the next iteration. Step 8: Replace the intake inlet Mach number design value input in Step 4 with the minimum intake inlet Mach number, and repeat Steps 4 to 6 to calculate the intake total pressure recovery coefficient corresponding to the minimum inlet Mach number. Step 9: If the total pressure recovery coefficient of the intake duct corresponding to the minimum inlet Mach number is zero, jump to Step 3 to start the next iteration; if it is not zero, assign the current total pressure recovery coefficient of the intake duct to the threshold of the first total pressure recovery coefficient of the intake duct. Step 10: Repeat steps 3 through 9. After iteration, output the threshold value of the first intake total pressure recovery coefficient that is the largest within the range of variable values ​​in step 2. At the same time, output the corresponding variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle of the intake. Based on the coordinates of the intersection of the line formed by the first panel and the leeward side of the outer compression section with the first profile, the coordinates of the intersection of the inlet boundary of the lip with the first profile, and the constraint conditions that the oblique shock wave can form, use trigonometric function relationships to determine the coordinates of the intersection of the line formed by the second panel and the first panel with the first profile, the coordinates of the intersection of the line formed by the second panel and the third panel with the first profile, the coordinates of the intersection of the line formed by the upper end face of the third panel and the inner compression section with the first profile, and the coordinates of the intersection of the line formed by the lip and the lower end face of the inner compression section with the first profile.

2. The method for determining the inlet structure of a subsonic and scramjet engine according to claim 1, characterized in that, The design value for the inlet Mach number is the cruise Mach number of a high-speed aircraft; the limiting value is the mode transition value from subsonic ramjet mode to scramjet mode.

3. The method for determining the inlet structure of a subsonic and scramjet engine according to claim 2, characterized in that, When the design value of the inlet Mach number of the ramjet engine is not greater than the limit value, the determined inlet outlet airflow parameters of the sub-fuel ramjet mode include: the first inlet outlet Mach number, the first outlet pressure, and the first outlet density; wherein, the first inlet outlet Mach number is the normal shock wave back Mach number corresponding to the largest first inlet total pressure recovery coefficient threshold in step ten, the first outlet pressure is the normal shock wave back pressure corresponding to the largest first inlet total pressure recovery coefficient threshold in step ten, and the first outlet density is the normal shock wave back density corresponding to the largest first inlet total pressure recovery coefficient threshold.

4. The method for determining the inlet structure of a subsonic and scramjet engine according to claim 2, characterized in that, The calculation of the fifth deflection angle variable value described in step three is as follows: the fifth deflection angle variable value is equal to the sum of the first wedge angle, second wedge angle, and third wedge angle variable values ​​minus the lip deflection angle variable value.

5. The method for determining the inlet structure of a subsonic and scramjet engine according to claim 2, characterized in that, In step four, when calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient of the first oblique shock wave using the oblique shock wave relationship, the inputs are the design value of the inlet Mach number and the variable value of the first wedge angle. When calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient of the second oblique shock wave, the inputs are the post-shock Mach number of the first oblique shock wave and the variable values ​​of the second wedge angle. When calculating the shock angle, post-shock Mach number, pressure, density, and total pressure recovery coefficient of the third oblique shock wave... When calculating the total pressure recovery coefficient before and after the oblique shock wave, the inputs are the Mach number after the second oblique shock wave and the third wedge angle variable value; when calculating the shock wave angle, Mach number after the wave, pressure, density, and total pressure recovery coefficient before and after the oblique shock wave of the fourth oblique shock wave, the inputs are the Mach number after the wave of the third oblique shock wave and the lip deflection angle variable value; when calculating the shock wave angle, Mach number after the wave, pressure, density, and total pressure recovery coefficient before and after the oblique shock wave of the fifth oblique shock wave, the inputs are the Mach number after the wave of the fourth oblique shock wave and the fifth deflection angle variable value.

6. The method for determining the inlet structure of a subsonic and scramjet engine according to claim 2, characterized in that, The calculation method for the shock angle of each oblique shock wave in step four is as follows: Where, β i , i = 1, 2, ..., 5 correspond to the shock angles of the i-th oblique shock wave; θ i i = 1, 2, ..., 5 correspond to the variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle obtained in each step of step three, respectively; Ma i ,i=1,2,…,5 correspond to the design value of the inlet Mach number, the Mach number behind the first oblique shock wave, the Mach number behind the second oblique shock wave, the Mach number behind the third oblique shock wave, and the Mach number behind the fourth oblique shock wave, respectively; γ is the specific heat ratio, which is taken as 1.4 in standard atmosphere.

7. A method for determining the intake structure of a subsonic and scramjet engine, wherein the intake structure of the subsonic and scramjet engine includes an outer compression section and an inner compression section. The leeward side of the outer compression section is a horizontal plane, and the windward side of the outer compression section is formed by sequentially splicing a first panel, a second panel, and a third panel. The third panel is connected to the upper end face of the inner compression section, and a lip with an angle is provided at the inlet of the lower end face of the inner compression section. The acute angle formed by the plane of the first panel and the horizontal plane of the outer compression section is the first wedge angle, the acute angle formed by the plane of the second panel and the plane of the first panel is the second wedge angle, the acute angle formed by the plane of the third panel and the plane of the second panel is the third wedge angle, the acute angle formed by the plane of the lip and the lower end face of the inner compression section is the lip deflection angle, and the acute angle formed by the plane of the third panel and the upper end face of the inner compression section is the fifth deflection angle. When the incoming flow velocity exceeds the preset Mach number threshold, the airflow forms the first oblique shock wave after passing the first wedge angle, the second oblique shock wave after passing the second wedge angle, the third oblique shock wave after passing the third wedge angle, the fourth oblique shock wave after passing the lip deflection angle, and the fifth oblique shock wave after passing the fifth deflection angle. For the intake of a subsonic ramjet engine, after the fifth oblique shock wave, a normal shock wave is formed after passing through the compression section inside the intake, which reduces the airflow velocity to subsonic speed. Its features are, When the design value of the inlet Mach number of a ramjet engine exceeds the limit, the determination of the inlet geometry parameters for the scramjet mode includes the following process: S1. Input the design value of the Mach number at the inlet of the scramjet engine, the minimum values ​​of the first wedge angle, the second wedge angle, the third wedge angle, the minimum value of the lip deflection angle, and the threshold value of the total pressure recovery coefficient of the second inlet; arbitrarily select the first section of the inlet structure, and give the coordinates of the intersection point of the line formed by the first panel and the leeward side of the outer compression section with the first section, and the coordinates of the intersection point of the inlet boundary of the lip with the first section; S2. Give the range of values ​​for the first wedge angle, second wedge angle, third wedge angle, and lip deflection angle respectively, and take values ​​uniformly within their respective ranges; S3. Within the range of values ​​of S2, given a set of variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle, calculate the variable value for the fifth deflection angle based on the given variable values ​​for the first wedge angle, the second wedge angle, the third wedge angle, and the lip deflection angle. S4. Starting from the first oblique shock wave, substitute the design value of the Mach number at the inlet of the air intake, the three wedge angles, the lip deflection angle, and the fifth deflection angle obtained in S3 into the oblique shock wave formula in turn, and calculate the shock wave angle, Mach number after the wave, pressure, and density of each oblique shock wave. Based on the shock wave angle, Mach number after the wave, and pressure of each oblique shock wave, calculate the total pressure recovery coefficient before and after each oblique shock wave. S5. Based on the product of the total pressure recovery coefficients before and after each oblique shock wave, obtain the total pressure recovery coefficient of the inlet. Output the total pressure recovery coefficient of the inlet, the first wedge angle, the second wedge angle, the third wedge angle, the lip deflection angle, the fifth deflection angle variable value obtained in step three, the Mach number after the fifth oblique shock wave, the pressure, and the density. S6. Determine whether the total pressure recovery coefficient of the intake duct obtained in S5 is greater than the threshold of the second total pressure recovery coefficient of the intake duct. If so, assign the current total pressure recovery coefficient of the intake duct to the threshold of the second total pressure recovery coefficient of the intake duct. Otherwise, jump to S3 to start the next iteration. S7. Repeat S3 to S6. After iteration, output the threshold value of the second intake total pressure recovery coefficient that is the largest within the range of variable S2. At the same time, output the corresponding variable values ​​of the first wedge angle, second wedge angle, third wedge angle, lip deflection angle, and fifth deflection angle of the intake. Based on the coordinates of the intersection of the line formed by the first panel and the leeward side of the outer compression section with the first profile, the coordinates of the intersection of the inlet boundary of the lip with the first profile, and the constraint conditions that the oblique shock wave can form, use trigonometric function relationships to determine the coordinates of the intersection of the line formed by the second panel and the first panel with the first profile, the coordinates of the intersection of the line formed by the second panel and the third panel with the first profile, the coordinates of the intersection of the line formed by the third panel and the upper end face of the inner compression section with the first profile, and the coordinates of the intersection of the line formed by the lip and the lower end face of the inner compression section with the first profile.

8. The method for determining the inlet structure of a subsonic and scramjet engine according to claim 7, characterized in that, The determined inlet outlet airflow parameters for the scramjet mode include: the second inlet outlet Mach number, the second outlet pressure, and the second outlet density; wherein, the second inlet outlet Mach number is the fifth oblique shock wave back Mach number corresponding to the largest second inlet total pressure recovery coefficient threshold in step seven, the second outlet pressure is the fifth oblique shock wave back pressure corresponding to the largest second inlet total pressure recovery coefficient threshold in step seven, and the second outlet density is the fifth oblique shock wave back density corresponding to the largest first inlet total pressure recovery coefficient threshold in step seven.

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