A control method for scramjet engines based on the position of the shock train in the isolator

Abstract

The present invention provides a control method for a scramjet engine based on the position of the shock train in the isolator to solve the technical problem that existing dual-mode scramjet engines cannot start when operating under low-altitude and low-Mach-number conditions due to excessive back pressure in the combustion chamber. The present invention takes the position of the shock train in the engine isolator and the pressure distribution on the combustion chamber wall as controlled parameters, and performs real-time control on the position of the shock train in the isolator and the pressure distribution on the combustion chamber wall, so that the scramjet engine operates accurately in a predetermined state throughout the flight trajectory. By controlling the position of the shock train in the isolator, it is ensured that the engine will not fail to start, and by controlling the pressure on the combustion chamber wall, it is ensured that the engine generates sufficient thrust to achieve the control of the scramjet engine.

Description

Technical Field

[0001] The present invention relates to the technical field of scramjet engine control, and specifically relates to a control method for a scramjet engine based on the position of the shock train in the isolator. Background Art

[0002] With the development of dual-mode scramjet engine technology, flight tests have been successively carried out at home and abroad. The control problem of dual-mode scramjet engines has gradually attracted the attention of experts at home and abroad. In the HyShot-X flight test project in the United States, the development of a scramjet engine control system was completed. The Kholod program led by Russia also designed a closed-loop control system with wall pressure feedback specifically for flight tests. However, in the flight tests, the engine still failed to start due to problems caused by the inlet, resulting in the failure of the flight test. From the results of several publicly reported flight tests, when the dual-mode scramjet engine operates under low-altitude and low-Mach number conditions, the engine fails to start due to excessive back pressure in the combustion chamber.

[0003] Patent CN115453886A proposes a multi-variable limit protection control method for a scramjet engine, using a fixed pressure ratio threshold as the safety critical value. However, the most likely time for the engine to fail to start is when the incoming flow Mach number and flight altitude are small and the fuel supply is large. At this time, the airflow parameters at the engine inlet are constantly changing, and the fixed threshold is not suitable as the safety critical value. The Kholod flight test in Russia used a fixed threshold, resulting in the engine still failing to start during the flight test.

[0004] In summary, achieving safe and effective control of scramjet engines throughout the flight trajectory is one of the key technologies for hypersonic vehicle control. The existing engine control technologies are not sufficient to meet the requirements of complex flight missions. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the existing dual-mode scramjet engine fails to start due to excessive back pressure in the combustion chamber when operating under low-altitude and low-Mach number conditions, and provides a control method for a scramjet engine based on the position of the shock train in the isolator.

[0006] The concept of the present invention is as follows: by installing pressure sensors on the isolator and combustion chamber wall surfaces to monitor the pressure distribution on the isolator and combustion chamber wall surfaces of the scramjet engine in real time, the engine controller then adjusts the fuel supply position and the opening degree of the high-speed regulating valve according to the real-time pressure distribution on the isolator and combustion chamber wall surfaces, and changes the fuel supply mode and flow rate in real time, so that when the engine has a relatively low incoming flow Mach number and a relatively low flight altitude, it can overcome the problems of relatively large air density and relatively large flight resistance in the atmosphere at this time, and provide sufficient thrust; at the same time, it is ensured that the engine will not fail to start due to excessive back pressure in the combustion chamber.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A control method for a scramjet engine based on the position of the shock train in the isolator, characterized in that it includes the following steps:

[0009] Step 1: Based on the fuel supply scheme of the engine, obtain the expected position of the shock train in the isolator and the pressure distribution on the combustion chamber wall surface;

[0010] The fuel supply scheme is a pre-formulated fuel supply plan or obtained by an on-board engine model according to the incoming flow conditions and the engine capture flow rate; the capture flow rate is calculated by the measured Mach number Ma0, altitude H0, and flight angle of attack α0 in real time;

[0011] Step 2: Calculate the current position of the shock train in the isolator according to the real-time pressure distribution on the isolator wall surface, compare the current position of the shock train with the expected position of the shock train in the isolator obtained in Step 1, judge whether there is a risk of engine non-start at present, and adjust the fuel supply of the most upstream fuel supply point of the engine;

[0012] Step 3: Measure the current pressure distribution on the combustion chamber wall surface, compare it with the expected pressure distribution on the combustion chamber wall surface obtained in Step 1, and then, while adjusting the fuel supply of the most upstream fuel supply point of the engine in Step 2, adjust the fuel supply flow rate of the downstream fuel supply points of the engine in real time based on the pressure distribution on the combustion chamber wall surface.

[0013] Further, Step 1 is specifically as follows:

[0014] When the fuel supply scheme is a pre-formulated fuel supply plan, the expected position of the shock train in the isolator and the pressure distribution on the combustion chamber wall surface are: the position of the shock train in the isolator and the pressure distribution on the combustion chamber wall surface obtained by using numerical calculation and ground test methods before the flight test for each state point when the engine operates on the flight trajectory;

[0015] When the fuel supply scheme is obtained by an on-board engine model based on the oncoming flow conditions and the engine capture flow rate, the expected isolator shock train position and the combustion chamber wall pressure distribution are as follows: Input the Mach number Ma0, altitude H0, and flight angle of attack α0 of the oncoming flow state measured in real time into the on-board engine model to obtain the isolator shock train position and the combustion chamber wall pressure distribution at each state point when the engine operates on the flight trajectory.

[0016] Further, step 2 is specifically as follows:

[0017] 2.1. Uniformly distribute wall pressure sensors on the midline of the upper wall surface of the isolator at the same layout interval;

[0018] 2.2. Based on the wall pressure values monitored in real time by the wall pressure sensors arranged in step 2.1, calculate the current isolator shock train position:

[0019]

[0020] In the formula, X LE (t) is the isolator shock train position at time t, P s,x (t) is the wall pressure at the horizontal position X at time t, P s,x,cold is the wall pressure during cold flow at the horizontal position X at time t, and λ2 is a constant related to the Mach number Ma0;

[0021] 2.3. Calculate the difference between the expected isolator shock train position and the current isolator shock train position. If the difference is negative, it is considered that there is a risk of engine non-start, and reduce the fuel supply of the most upstream fuel supply point of the engine; if the difference is positive, it is considered that the engine still has performance potential, and increase the fuel supply of the most upstream fuel supply point of the engine.

[0022] Further, step 2 is specifically as follows:

[0023] 2.1. Uniformly distribute wall pressure sensors on the midline of the upper wall surface of the isolator at the same layout interval;

[0024] 2.2. Based on the wall pressure values monitored in real time by the wall pressure sensors arranged in step 2.1, calculate the current isolator shock train position:

[0025]

[0026] In the formula, X LE (t) is the isolator shock train position at time t, P s,x (t) is the wall pressure at the horizontal position X at time t, P s,x,cold is the wall pressure during cold flow at the horizontal position X at time t, and λ2 is a constant related to the Mach number Ma0;

[0027] 2.3. Determine whether the calculated position of the current shock train in the isolation section exceeds the set primary safety warning boundary. If it does, reduce the fuel supply of the most upstream fuel supply point of the engine and maintain it for a period of time; if not, supply fuel to the engine according to the engine acceleration state control logic, and return to step 2.2;

[0028] 2.4. Determine whether the current engine has reached the target acceleration. If it has, maintain the current fuel supply of the engine; if not, proceed to step 2.5;

[0029] 2.5. Determine whether the current position of the shock train in the isolation section exceeds the set secondary safety warning boundary. If it does, maintain the current fuel supply of the engine, return to step 2.2, and adjust and control the fuel supply of the most upstream fuel supply point of the engine in real time; if not, increase the fuel supply of the most upstream fuel supply point of the engine, and return to step 2.4.

[0030] Further, it is characterized in that:

[0031] In step 2.2, when the calculated position of the current shock train in the isolation section is between the two sensor layout points, the position of the shock train in the isolation section is corrected by interpolation calculation.

[0032] Further, in step 2.1, the layout interval is 2 - 10 cm.

[0033] Further, step 3 is specifically as follows:

[0034] 3.1. Set high-frequency wall pressure monitoring points at the key cross-sections of the combustion chamber, take the pressure values of the monitoring points as the current combustion chamber wall pressure, and obtain the current combustion chamber wall pressure distribution;

[0035] 3.2. Determine the combustion chamber wall pressure of each key cross-section through the expected combustion chamber wall pressure distribution obtained in step 1, calculate the difference between the combustion chamber wall pressure of each key cross-section minus the current combustion chamber key cross-section wall pressure, and adjust and control the fuel supply of the corresponding fuel supply points downstream of the engine in real time through the actuators set in the engine control system that are the same in number and in one-to-one correspondence with the key cross-sections;

[0036] If the difference is negative, reduce the fuel supply of the corresponding fuel supply point downstream of the engine; if the difference is positive, increase the fuel supply of the corresponding fuel supply point downstream of the engine.

[0037] Further, in step 3.1, the positions of the key cross-sections are determined by numerical calculation and ground test data, and there is a monotonic correspondence relationship between the wall pressure of each key cross-section and the fuel supply of the corresponding actuator.

[0038] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0039] The control method of a scramjet engine based on the position of the shock train in the isolator proposed by the present invention uses the position of the shock train in the engine isolator and the pressure distribution on the combustion chamber wall as controlled parameters to perform real-time control on the position of the shock train in the isolator and the pressure distribution on the combustion chamber wall, so that the scramjet engine accurately operates in a predetermined state throughout the flight trajectory. By controlling the position of the shock train in the isolator, it is ensured that the engine does not fail to start. By controlling the pressure on the combustion chamber wall, it is ensured that the engine generates sufficient thrust to achieve the control of the scramjet engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is the schematic diagram of the control method of the scramjet engine based on the position of the shock train in the isolator of the present invention;

[0041] Figure 2 is the flow chart of adjusting and controlling the engine fuel supply based on the position of the shock train in the isolator in the control method of the present invention;

[0042] Figure 3 is the comparison diagram of the shock train position calculated from the pressure distribution in the isolator and the shock train position measured by the schlieren test using the control method of the present invention;

[0043] Figure 4 is the wall pressure distribution diagram of simultaneously increasing the fuel supply and the pressure downstream of the combustion chamber using the control method of the present invention when the position of the shock train in the isolator remains unchanged;

[0044] Figure 5 is the wall pressure distribution diagram of the isolator and the combustion chamber when the position of the shock train in the isolator is controlled at different positions using the control method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] To make the objectives, advantages, and features of the present invention clearer, the following further elaborates in detail on the control method of the scramjet engine based on the position of the shock train in the isolator proposed by the present invention in combination with the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0046] As Figure 1 shown, the control method of the scramjet engine based on the position of the shock train in the isolator provided in this embodiment specifically includes the following steps:

[0047] Step 1: The engine controller calculates the engine capture flow rate, that is, the air flow rate flowing into the combustion chamber of the engine, according to the real-time measured Mach number Ma0, altitude H0, and flight angle of attack α0.

[0048] Step 2: Based on the fuel supply scheme of the engine, the expected position of the shock train in the isolator and the pressure distribution on the combustion chamber wall are obtained.

[0049] The fuel supply plan can be determined according to a pre - established fuel supply plan, or can be obtained by real - time calculation through an on - board engine model based on the on - coming flow conditions.

[0050] The preset fuel supply plan is generally designed based on test and numerical simulation results. During the engine operation, the control system needs to ensure that it always operates within the safety working boundaries such as temperature and pressure. Therefore, after determining that the engine is operating within the safety working boundaries, the engine actuator supplies fuel to the engine according to the obtained fuel supply flow rate and fuel supply position. When the engine determines that it has or is about to operate outside the safety boundary, it will adjust the fuel supply flow rate and position to obtain the fuel supply flow rate and position that ensure the engine operates within the safety working boundaries, and the control system supplies fuel to the engine according to this fuel supply plan.

[0051] When the fuel supply plan adopts a pre - established fuel supply plan, the expected positions of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall are: the positions of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall at each state point of the engine operating on the flight trajectory obtained by means of numerical calculation and ground tests before the flight test;

[0052] When the fuel supply plan is determined based on an on - board engine model according to the on - coming flow conditions and the captured flow rate, the expected positions of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall are: the positions of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall at each state point of the engine operating on the flight trajectory obtained by inputting the real - time measured on - coming flow state Mach number Ma0, altitude H0, and flight angle of attack α0 into the on - board engine model;

[0053] During actual flight, the positions of the shock wave train in the engine isolator and the pressure distribution in the combustion chamber are controlled to the expected targets.

[0054] Step 3: Calculate the current position of the shock wave train in the isolator according to the real - time pressure distribution on the isolator wall, compare the current shock wave train position with the expected position of the shock wave train in the isolator obtained in Step 2, determine whether there is a risk of engine non - start for the current engine, and adjust the fuel supply at the most upstream fuel supply point of the engine for control;

[0055] 3.1. Evenly distribute wall pressure sensors at a certain interval on the mid - line of the upper wall of the isolator;

[0056] The interval between the sensors can be 2 - 10 cm, and generally, wall pressure sensors are evenly distributed at an interval of 5 cm;

[0057] 3.2. Based on the pressure values obtained by real - time monitoring of the sensors arranged in Step 3.1, calculate the current position of the shock wave train in the isolator, and its algorithm is calculated according to the following formula:

[0058]

[0059] In the formula, X LE (t) is the position of the shock wave train in the isolation section at time t, and P s,x (t) is the wall pressure at the position of X in the horizontal direction at time t, and P s,x,cold is the wall pressure during cold flow at the position of X in the horizontal direction at time t, and λ2 is a constant related to the Mach number Ma0; the position of X in the horizontal direction refers to the position corresponding to the coordinate of X (mm) from the inlet to the outlet of the upper wall of the isolation section;

[0060] When the calculated current position of the shock wave train in the isolation section is between the two sensor layout points, the position of the shock wave train in the isolation section is corrected by interpolation calculation;

[0061] 3.3. Embed the current position of the shock wave train in the isolation section obtained in step 3.2 into the engine closed-loop control system, so that the control system can determine and control the position of the shock wave train in the isolation section according to the real-time wall pressure distribution;

[0062] Specifically: Calculate the difference between the expected position of the shock wave train in the isolation section and the current position of the shock wave train in the isolation section. If the difference is negative, it is considered that there is a risk of engine non-start, and the fuel supply of the most upstream fuel supply point of the engine is reduced; if the difference is positive, it is considered that the engine still has performance potential, and the fuel supply of the most upstream fuel supply point of the engine is increased.

[0063] Step 4. Calculate the current combustion chamber wall pressure distribution, compare it with the expected combustion chamber wall pressure distribution obtained in step 2, and then, while adjusting and controlling the fuel supply of the most upstream fuel supply point of the engine in step 3, adjust and control the fuel supply flow of the downstream fuel supply points of the engine in real time based on the combustion chamber wall pressure distribution;

[0064] 4.1. Set high-frequency wall pressure monitoring points at the key sections of the combustion chamber, and use the pressure values of the monitoring points as the current combustion chamber wall pressure to obtain the current combustion chamber wall pressure distribution;

[0065] The key sections are determined through numerical calculations and ground test data, and the number of key sections is equal to the number of actuators in the engine; the selection of the key section positions is such that each actuator corresponds to a key section one by one, and the wall pressure on each key section has a monotonic correspondence with the fuel supply of the corresponding actuator;

[0066] The actuators mainly include fuel supply valve switches, high-speed regulating valves, etc., and adjust the fuel supply position and flow of each fuel supply point of the engine in real time according to the instructions of the control system;

[0067] 4.2. Determine the combustion chamber wall pressure at each key section based on the expected combustion chamber wall pressure distribution obtained in Step 2, calculate the difference between the combustion chamber wall pressure at each key section and the current combustion chamber key section wall pressure, and adjust and control the fuel supply amount at the corresponding fuel supply point downstream of the engine in real time by setting actuators in the engine control system that are the same in number as and in one-to-one correspondence with the number of key sections;

[0068] If the difference is negative, reduce the fuel supply amount at the corresponding fuel supply point downstream of the engine; if the difference is positive, increase the fuel supply amount at the corresponding fuel supply point downstream of the engine.

[0069] Embodiment 2

[0070] In the above Step 3, calculate the current isolator shock train position based on the real-time isolator wall pressure distribution, compare the current shock train position with the expected isolator shock train position obtained in Step 2, determine whether there is a risk of engine non-start in the current engine, and adjust and control the fuel supply at the most upstream fuel supply point of the engine. Another method can also be adopted, specifically:

[0071] As Figure 2 shown, determining and controlling the isolator shock train position based on the real-time wall pressure distribution can also be:

[0072] In order to ensure that the engine does not fail to start due to excessive combustion chamber back pressure while maximizing the performance potential of the engine, when the incoming flow Mach number is small and the fuel supply amount is large, the scramjet engine operates in the subsonic combustion mode. At this time, the engine is prone to non-start caused by excessive fuel supply or excessive combustion chamber back pressure. It is necessary to monitor the isolator shock train position in real time. To ensure the safe and stable operation of the engine, two levels of safety and stability warning boundaries are set according to the different positions of the isolator shock train. The safety margin of the first-level safety warning boundary is smaller than that of the second-level safety warning boundary.

[0073] It should be noted that the safety and stability warning boundary is obtained based on the oncoming flow conditions. Different oncoming flow conditions result in different shock train positions corresponding to the safety and stability boundary. When the actual shock train position exceeds the primary safety warning boundary, the maximum state control logic is then entered. To ensure the safe and stable operation of the engine, the first operation for safe and stable operation in the maximum state is to reduce the fuel supply to the safe flow rate and maintain it for an appropriate period. Subsequently, it is determined whether the current acceleration meets the requirements of the flight mission. If it does, this fuel supply is maintained and the next control cycle is entered; if the acceleration requirement is not met, it is necessary to determine whether the current actual shock train position exceeds the secondary safety warning boundary. If the actual shock train position exceeds the secondary safety warning boundary at this time, it indicates that the engine cannot further increase the fuel supply. If the actual shock train position does not exceed the secondary safety warning boundary at this time, it means that there is still performance potential within the safe operating range of the engine, and the fuel flow rate can be appropriately increased at this time. After increasing the fuel flow rate, it is determined whether the current acceleration meets the requirements of the flight mission. If it does, this fuel supply is maintained and the next control cycle is entered. If not, it continues to be determined whether the current shock train position exceeds the secondary safety warning boundary. If it has exceeded the secondary safety operating boundary at this time, this fuel supply flow rate is maintained and the next control cycle is entered.

[0074] Specifically:

[0075] 3.1. Wall pressure sensors are evenly distributed at certain intervals on the midline of the upper wall surface of the isolator;

[0076] The interval between the sensors can be 2 - 10 cm, and generally, the wall pressure sensors are evenly distributed at an interval of 5 cm;

[0077] 3.2. Based on the pressure values obtained by real-time monitoring of the sensors arranged in step 3.1, calculate the current shock train position in the isolator. Its algorithm is calculated according to the following formula:

[0078]

[0079] In the formula, X LE (t) is the shock train position in the isolator at time t, P s,x (t) is the wall pressure at the horizontal position X, P s,x,cold is the wall pressure during cold flow at the horizontal position X at time t, and λ2 is a constant related to the Mach number Ma0;

[0080] When the calculated current shock train position in the isolator is between the two sensor layout points, the shock train position in the isolator is corrected by interpolation calculation;

[0081] 3.3. Determine whether the calculated position of the current shock train in the isolation section exceeds the set primary safety warning boundary. If so, reduce the fuel supply of the most upstream fuel supply point of the engine and maintain it for a period of time; if not, supply fuel to the engine according to the engine acceleration state control logic, and return to step 3.2 until the position of the current shock train in the isolation section exceeds the set primary safety warning boundary;

[0082] 3.4. Determine whether the current engine has reached the target acceleration. If so, maintain the current engine fuel supply; if not, proceed to step 3.5;

[0083] 3.4. Determine whether the position of the current shock train in the isolation section exceeds the set secondary safety warning boundary. If so, maintain the current engine fuel supply; if not, increase the fuel supply of the most upstream fuel supply point of the engine until the engine reaches the target acceleration, and then maintain the engine fuel supply.

[0084] Appendix Figure 3 is a comparison diagram of the shock train position calculated from the pressure distribution in the isolation section and the shock train position measured by the schlieren test. It can be seen from the figure that the position of the shock train in the isolation section calculated by using the method of the present invention through the isolation section pressure is consistent with the actual shock train position.

[0085] Appendix Figure 4 is the test result of controlling the engine by using the method of the present invention. It can be seen that in the test, using the method of the present invention, the control effect of maintaining the position of the shock train in the isolation section unchanged while increasing the pressure on the downstream wall of the combustion chamber is achieved.

[0086] Appendix Figure 5 is the wall pressure distribution diagram of controlling the shock train in the isolation section at different positions by using the method of the present invention. It can be seen from the figure that accurate control of the position of the shock train in the isolation section can be achieved, providing a basis for accurately adjusting the engine fuel supply.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present invention.

Claims

1. A control method for a scramjet engine based on the position of the shock train in the isolation section, characterized in that, It includes the following steps: Step 1: Based on the fuel supply scheme of the engine, obtain the expected position of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall; The fuel supply scheme is a pre-established fuel supply plan or obtained by an on-board engine model according to the oncoming flow conditions and the engine capture flow rate; the capture flow rate is calculated through the Mach number Ma0, altitude H0, and flight angle of attack α0 measured in real time; Step 2: Calculate the current position of the shock wave train in the isolator according to the real-time pressure distribution on the isolator wall, compare the current position of the shock wave train with the expected position of the shock wave train in the isolator obtained in Step 1, determine whether there is a risk of engine non-start at present, and adjust the fuel supply of the most upstream fuel supply point of the engine; Step 3: Measure the current pressure distribution on the combustion chamber wall, compare it with the expected pressure distribution on the combustion chamber wall obtained in Step 1, and then, while adjusting the fuel supply of the most upstream fuel supply point of the engine in Step 2, adjust the fuel supply flow rate of the downstream fuel supply point of the engine in real time based on the pressure distribution on the combustion chamber wall.

2. The scramjet engine control method based on the position of the shock train in the isolation section according to claim 1, wherein Specifically, Step 1 is as follows: When the fuel supply scheme is a pre-established fuel supply plan, the expected position of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall are: the position of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall at each state point of the engine operating on the flight trajectory obtained by means of numerical calculation and ground tests before the flight test; When the fuel supply scheme is obtained by an on-board engine model according to the oncoming flow conditions and the engine capture flow rate, the expected position of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall are: input the real-time measured oncoming flow state Mach number Ma0, altitude H0, and flight angle of attack α0 into the on-board engine model, and obtain the position of the shock wave train in the isolator and the pressure distribution on the combustion chamber wall at each state point of the engine operating on the flight trajectory.

3. The scramjet engine control method based on the position of the shock train in the isolation section according to claim 2, wherein Specifically, Step 2 is as follows: 2.1 Uniformly arrange wall pressure sensors on the midline of the upper wall surface of the isolator at the same layout interval; 2.2 Calculate the current position of the shock wave train in the isolator based on the wall pressure values monitored in real time by the wall pressure sensors arranged in Step 2.1; where X LE (t) is the position of the shock train in the isolation section at time t, and P s,x (t) is the wall pressure at the X position in the horizontal direction at time t, and P s,x,cold is the wall pressure during cold flow at the X position in the horizontal direction at time t, and λ2 is a constant related to the Mach number Ma0; 2.3 Calculate the difference between the expected position of the shock wave train in the isolator and the current position of the shock wave train in the isolator. If the difference is negative, it is considered that there is a risk of engine non-start, and reduce the fuel supply of the most upstream fuel supply point of the engine; if the difference is positive, it is considered that the engine still has performance potential, and increase the fuel supply of the most upstream fuel supply point of the engine.

4. The control method of a scramjet engine based on the position of the shock train in the isolation section according to claim 2, wherein Specifically, Step 2 is as follows: 2.1 Uniformly arrange wall pressure sensors on the midline of the upper wall surface of the isolator at the same layout interval; 2.2 Calculate the current position of the shock wave train in the isolator based on the wall pressure values monitored in real time by the wall pressure sensors arranged in Step 2.1; where X LE (t) is the position of the shock wave train in the isolation section at time t, and P s,x (t) is the wall pressure at the X position in the horizontal direction at time t, and P s,x,cold is the wall pressure during cold flow at the X position in the horizontal direction at time t, and λ2 is a constant related to the Mach number Ma0; 2.3 Judge whether the calculated current position of the shock wave train in the isolator exceeds the set first-level safety warning boundary. If so, reduce the fuel supply of the most upstream fuel supply point of the engine and maintain it for a period of time; if not, supply fuel to the engine according to the engine acceleration state control logic, and return to Step 2.2; 2.4 Judge whether the current engine reaches the target acceleration. If so, maintain the current fuel supply of the engine; if not, enter Step 2.5; 2.

5. Determine whether the position of the shock train in the current isolation section exceeds the set secondary safety warning boundary. If so, maintain the current engine fuel supply, return to step 2.2, and adjust and control the fuel supply of the most upstream fuel supply point of the engine in real time. If not, increase the fuel supply of the most upstream fuel supply point of the engine and return to step 2.

4.

5. The scramjet engine control method based on the position of the shock train in the isolation section according to claim 3 or 4, characterized in that: In step 2.2, when it is calculated that the position of the shock train in the current isolation section is between the two sensor layout points, the position of the shock train in the isolation section is corrected by interpolation calculation.

6. The scramjet engine control method based on the position of the shock train in the isolation section according to claim 5, characterized in that: In step 2.1, the layout interval is 2 - 10 cm.

7. The scramjet engine control method based on the position of the shock train in the isolation section according to claim 6, characterized in that, Step 3 is specifically as follows: 3.

1. Set high-frequency wall pressure monitoring points at the key cross-sections of the combustion chamber, use the pressure values of the monitoring points as the current combustion chamber wall pressure, and obtain the current combustion chamber wall pressure distribution. 3.

2. Determine the combustion chamber wall pressure of each key cross-section through the expected combustion chamber wall pressure distribution obtained in step 1, calculate the difference between the combustion chamber wall pressure of each key cross-section minus the current combustion chamber key cross-section wall pressure, and adjust and control the fuel supply of the corresponding fuel supply points downstream of the engine in real time through actuators set in the engine control system that are the same in number and in one-to-one correspondence with the key cross-sections. If the difference is negative, reduce the fuel supply of the corresponding fuel supply point downstream of the engine; if the difference is positive, increase the fuel supply of the corresponding fuel supply point downstream of the engine.

8. The scramjet engine control method based on the position of the shock train in the isolation section according to claim 7, characterized in that: In step 3.1, the position of the key cross-section is determined by numerical calculation and ground test data, and there is a monotonic correspondence between the wall pressure on each key cross-section and the fuel supply of the corresponding actuator.

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