A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet

Abstract

The present invention belongs to the technical field of scramjet engines, and discloses a protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. Step 1: Determine the safety margin characterization of the inlet; Step 2: Based on the safety margin characterization of the inlet in Step 1, select the target position of the shock train; Step 3: Based on the target position of the shock train selected in Step 2, monitor the safety margin of the inlet; Step 4: Based on the safety margin of the inlet monitored in Step 3, perform closed-loop control on the inlet margin. The present invention can timely identify the working state when the inlet fails to start, and more importantly, can avoid the occurrence of inlet non-start, and implement safety margin control on the inlet.

Description

Technical Field

[0001] The present invention belongs to the technical field of scramjet engines, and particularly relates to a protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. Background Art

[0002] Hypersonic vehicles, with their flight speeds far exceeding those of conventional aircraft, are "killer" weapons for achieving high-speed maneuverable penetration and striking moving targets of the enemy, and have become one of the technological high points in the current aerospace field. As the aerodynamic interface between a hypersonic vehicle and a scramjet engine, the inlet is the main "compressor" of the engine, undertaking important tasks such as reducing the oncoming flow velocity, increasing the oncoming flow pressure and temperature, meeting the engine flow demand, and reasonably organizing the forebody flow. Its design form and performance have a significant impact on the operating ability and working performance of the engine.

[0003] In the X-51A flight test accident, the inlet often fails to start, which has led to research in the academic community on the coupling relationship between hypersonic inlets, isolators, and combustors. In recent years, through the analysis of numerical simulations and ground tests of the non-start problem, a large amount of research has been carried out in terms of engine structure and control systems. The main characteristics of the inlet failing to start are a sharp drop in the captured flow rate and a deterioration of the flow field quality, resulting in the engine being unable to generate normal thrust, and even causing surges that lead to mechanical structure damage or combustor flameout. The non-start of the inlet is a strongly nonlinear and abrupt process. For inlets with a wide flight speed range, they may experience three working conditions: non-start at low Mach numbers, start state, and non-start at high Mach numbers. It is very difficult to solve the non-start problem only through the optimization design of the inlet, so it is necessary to monitor its state and use a feedback control system for protection. Summary of the Invention

[0004] The present invention provides a protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet, which can timely identify the working state when the inlet fails to start, and more importantly, can avoid the occurrence of the inlet failing to start and implement safety margin control for the inlet.

[0005] The present invention is achieved through the following technical solutions:

[0006] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet, the protection control method specifically includes the following steps:

[0007] Step 1: Determine the safety margin characterization of the inlet;

[0008] Step 2: Select the target position of the shock train based on the safety margin characterization of the inlet in Step 1;

[0009] Step 3: Monitor the safety margin of the inlet based on the target position of the shock train selected in Step 2;

[0010] Step 4: Based on the safety margin of the inlet monitored in Step 3, perform closed-loop control on the inlet margin.

[0011] A protection control method for characterizing the safety margin of the leading edge position of the shock train of a hypersonic inlet. Specifically, Step 1 is to quantitatively characterize the safety margin as the distance between the leading edge of the shock train and the throat. The definition formula of the safety margin is:

[0012] Safety margin = 1 – L shock / L iso (1)

[0013] Where L shock is the length of the shock train, and L iso is the length of the inlet-isolation section.

[0014] A protection control method for characterizing the safety margin of the leading edge position of the shock train of a hypersonic inlet. Specifically, Step 2 is to select a position far from the background shock reflection point as the target position of the shock train when performing equal margin control on the inlet.

[0015] A protection control method for characterizing the safety margin of the leading edge position of the shock train of a hypersonic inlet. Specifically, Step 3 is to obtain the leading edge position of the shock train in the isolation section by using the pressure ratio method.

[0016] A protection control method for characterizing the safety margin of the leading edge position of the shock train of a hypersonic inlet. First, record the pressure values at several wall positions in the through-flow state as the reference pressure p Tare,i (i = 1, 2,...), and record the pressure at each position at each moment as p s,i (kΔt); thus, the pressure ratio vector is obtained as shown in the following formula:

[0017]

[0018] Interpolate based on the pressure ratio vector PR(kΔt) and design a threshold according to the actual flow field conditions; when the pressure ratio vector reaches this threshold, an estimated value of the leading edge position of the shock train in the isolation section can be obtained.

[0019] A protection control method for characterizing the safety margin of the leading edge position of the shock train of a hypersonic inlet. The method for estimating the leading edge position of the shock train is summarized in the form of Equation (3); where I is the interpolation method, x tr is the position of the measured pressure value, and pr des = 1.5:

[0020] x sh,PR(kΔt) = I(PR(kΔt), x tr , pr des ) (3)

[0021] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. The specific steps of step 4 are as follows:

[0022] Step 4.1: Select 10 equally spaced pressure measurement points on the cowl side and the forebody side in the inlet-isolation section respectively;

[0023] Step 4.2: Process the pressure values obtained from the pressure measurement points in step 4.1.

[0024] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. The specific processing of the obtained pressure values in step 4.2 is as follows:

[0025] Step 4.2.1: Estimate the leading edge position of the shock train at the current moment using the pressure ratio method;

[0026] Step 4.2.2: Design a PI controller;

[0027] Step 4.2.3: Use the PID Tuner toolbox to adjust the parameters in the PI controller. The form of the PI controller is P + I(1 / s), and perform equal-margin closed-loop control of the inlet.

[0028] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. The specific design of the PI controller in step 4.2.2 is as follows: Give a backpressure boundary condition at the outlet of the hypersonic inlet, and observe the change of the leading edge position of the shock train in the inlet-isolation section; Use the system identification toolbox to take the backpressure boundary condition as the input and the corresponding change of the leading edge position of the shock train as the output, and identify a first-order transfer function.

[0029] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above method steps are implemented.

[0030] The beneficial effects of the present invention are:

[0031] Based on a number of pressure measurement points on the cowl and forebody sides of the hypersonic inlet, the present invention monitors the leading edge position of the shock train and characterizes the safety margin of the inlet by the distance between the leading edge position of the shock train and the throat.

[0032] When the safety margin of the inlet is low, the present invention timely adjusts the backpressure condition to ensure that the inlet is in a high-performance working state and does not enter the unstart state due to too low a safety margin. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the safety margin of the inlet of the present invention.

[0034] Figure 2 It is a diagram showing the background wave system and the wall pressure distribution of the hypersonic inlet-isolation section of the present invention.

[0035] Figure 3 It is a schematic diagram of obtaining the leading edge position of the shock train by the pressure ratio method in the present invention

[0036] Figure 4 It is a schematic diagram of the safety margin control loop of the inlet of the present invention

[0037] Figure 5 It is a schematic diagram of the variation of the leading edge position of the shock train under the given step back pressure condition in the present invention, where Figure 6 (a) Schematic diagram of the step back pressure boundary condition Figure 5 (b) Schematic diagram of the variation of the leading edge position of the shock train.

[0038] Figure 6 It is a schematic diagram of the influence of the background wave system on the variation law of the leading edge position of the shock train in the present invention, where Figure 6 (a) Schematic diagram of the influence of the unstable variation law Figure 6 (b) Schematic diagram of the influence of the stable variation law.

[0039] Figure 7 It is a diagram of the identification result of the transfer function of the present invention.

[0040] Figure 8 It is a diagram of the closed-loop control result in the all-digital platform of the present invention. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet, the protection control method specifically includes the following steps:

[0043] Step 1: Determine the safety margin characterization of the inlet;

[0044] Step 2: Select the target position of the shock train based on the safety margin characterization of the inlet in Step 1;

[0045] Step 3: Based on the target position of the shock train selected in Step 2, monitor the safety margin of the inlet.

[0046] Step 4: Based on the safety margin of the inlet monitored in Step 3, perform closed-loop control on the inlet margin.

[0047] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. The determination of the safety margin of the inlet in Step 1 is specifically as follows:

[0048] The specific characterization of the safety margin is as follows: During the process of continuously increasing the back pressure at the outlet of the hypersonic inlet-isolation section, whether the inlet will experience a non-start phenomenon is related to the movement of the shock train. When the back pressure at the outlet of the inlet-isolation section is relatively low, the shock train is located downstream of the inlet-isolation section, and the safety margin is relatively high, and the working state is safe, but the potential of the engine is utilized less. When the back pressure at the outlet of the inlet-isolation section is relatively high, the shock train is located in the mid-upper reaches near the throat of the inlet-isolation section, and the engine is in a high-performance working state, but the safety margin is relatively low. Once the shock train crosses the throat, a non-start phenomenon of the inlet occurs. According to the above description of the safety margin of the inlet-isolation section, the safety margin is quantitatively characterized as the distance between the leading edge of the shock train and the throat, as Figure 1 shown; the definition formula of the safety margin is:

[0049] Safety margin = 1 – L shock / L iso (1)

[0050] where L shock is the length of the shock train, and L iso is the length of the inlet-isolation section.

[0051] Analyze the definition formula of the safety margin: At low back pressure, the shock train is located downstream of the inlet-isolation section, the length of the shock train is relatively small, the safety margin is close to 1, and the working state of the inlet is relatively safe; at high back pressure, the shock train is located in the mid-upper reaches of the inlet-isolation section, the shock train is longer, the safety margin is close to 0, and the working state of the inlet is close to the non-start boundary. When the shock train moves upstream and crosses the throat and is even pushed out of the inlet-isolation section, the safety margin is a negative value at this time, which also means that a non-start phenomenon of the inlet occurs.

[0052] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. In step 2, based on the safety margin characterization of the inlet in step 1, the target position of the shock train is selected. Specifically, although the movement of the shock train is driven by the back pressure at the outlet of the inlet-isolation section, there is no linear relationship between them, and it is impossible to simply fit the relationship between the shock train position and the back pressure at the inlet outlet for open-loop control. During the movement of the shock train in the isolation section, unstable and uncontrollable jumps occur at the background shock reflection point. Therefore, closed-loop control is required when controlling the shock train position, and the position where the shock train can be stable, that is, the position far from the background shock reflection point, is selected. As Figure 2 Shown is the background wave system and the pressure distribution on both side walls calculated for the hypersonic inlet-isolation section under flow-through conditions;

[0053] There will be a significant local pressure increase at the background shock reflection point. Therefore, the region where the shock train cannot be stable can be intuitively obtained based on the background wave system and the wall pressure distribution. When performing equal-margin control on this inlet, a position far from the background shock reflection point is selected as the target position of the shock train.

[0054] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. In step 3, based on the target position of the shock train selected in step 2, the safety margin of the inlet is monitored. Specifically, in order to control the leading edge position of the shock train, it is necessary to monitor the leading edge position of the shock train in real time. The leading edge position of the shock train in the isolation section is obtained by the pressure ratio method.

[0055] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. First, record the pressure values at several wall positions under the flow-through state as the reference pressure p Tare,i (i = 1, 2,...), and record the pressure at each position at each moment as p s,i (kΔt). Thus, the pressure ratio vector is obtained as shown in the following formula:

[0056]

[0057] Interpolation is performed based on the pressure ratio vector PR(kΔt), and a threshold is designed according to the actual flow field conditions. As Figure 3 Shown, when the pressure ratio vector reaches this threshold, an estimated value of the leading edge position of the shock train in the isolation section can be obtained.

[0058] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. The method for estimating the leading edge position of the shock train is summarized in the form of formula (3); where I is the interpolation method, x tr is the position of the measured pressure value, prdes = 1.5:

[0059] x sh,PR (kΔt) = I(PR(kΔt), x tr , pr des ) (3)

[0060] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. In step 4, based on the safety margin monitored in step 3, the closed-loop control of the inlet margin is specifically carried out as follows. The safety margin control of the hypersonic inlet - isolator is carried out as Figure 4 shown in the safety margin control loop;

[0061] Step 4.1: Select 10 equally spaced pressure measurement points on the cowl side and the forebody side in the inlet - isolator respectively;

[0062] Step 4.2: Process the pressure values obtained from the pressure measurement points in step 4.1.

[0063] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. In step 4.2, the processing of the obtained pressure values is specifically as follows,

[0064] Step 4.2.1: Use the pressure ratio method to estimate the leading edge position of the shock train at the current moment;

[0065] Step 4.2.2: Design a PI (Proportional integral) controller;

[0066] Step 4.2.3: Use the PID Tuner toolbox to adjust the parameters in the PI controller. The form of the PI controller is P + I(1 / s), and the equal - margin closed - loop control of the inlet is carried out.

[0067] A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet. In step 4.2.2, the design of the PI (Proportional integral) controller is specifically as follows. A back - pressure boundary condition is given at the outlet of the hypersonic inlet, and the change of the leading edge position of the shock train in the inlet - isolator is observed. Using the System identification toolbox, the back - pressure boundary condition is used as the input, and the corresponding change of the leading edge position of the shock train is used as the output, and a first - order transfer function is identified.

[0068] A computer - readable storage medium stores a computer program therein. When the computer program is executed by a processor, the above - mentioned method steps are implemented.

[0069] Based on the simulation platform, equal-margin closed-loop control is carried out for the hypersonic inlet-isolation section.

[0070] First, a step backpressure boundary condition is given at the outlet of the hypersonic inlet, and the change of the leading edge position of the shock train in the inlet-isolation section is observed, as Figure 5 shown. For the convenience of the subsequent model identification process, the backpressure value and the corresponding leading edge position of the shock train are normalized.

[0071] Then, based on the understanding of the flow field structure, the change of the leading edge position of the shock train corresponding to the backpressure boundary condition is analyzed. As Figure 5 (b) shows, from 10 ms to 20 ms, the shock train is in a critically stable state, and the leading edge position of the shock train oscillates. As Figure 6 (a) shows, at t = 11.3 ms, the leading edge position of the shock train on the cowl side just moves to the downstream of the reflection point of a background shock on the cowl wall. When the leading edge of the shock train passes through the shock / boundary layer interaction position, a jump phenomenon occurs. Therefore, at t = 11.7 ms, the leading edge of the shock train on the cowl side has jumped upstream to this reflection point. However, the backpressure at the inlet outlet does not rise accordingly, and it cannot support the shock train to remain at this position, so it turns back downstream. At t = 11.9 ms, the leading edge of the shock train on the cowl side returns to the downstream of the background shock reflection point again, and so on, which leads to the observed oscillation of the leading edge position of the shock train. During the process from 20 ms to 30 ms, the shock train quickly converges to a stable position. At this time, there is still a certain distance between the leading edge position of the shock train and the background shock reflection point, and the position of the shock train can be maintained stable, as Figure 6 (b) shows. From 30 ms to 40 ms, the leading edge position of the shock train is in an asymptotically stable state, and the oscillation amplitude of the position decreases continuously during the movement of the shock train and finally converges to a stable point, which is a state between critical stability and stability.

[0072] Next, using the System identification toolbox, the step backpressure is taken as the input, and the corresponding change of the leading edge position of the shock train is taken as the output. A first-order transfer function G(s) = -5249 / (s + 5311) is identified, as Figure 7 shown. The fitting accuracy of the transfer function is 83.41%.

[0073] Finally, after obtaining the transfer function, the parameters in the PI controller are adjusted using the PID Tuner toolbox. The form of the PI controller is P + I(1 / s). Among them, P = -0.293 and I = -3173.354. The result of closed-loop control using this PI controller in the full digital platform is as Figure 8 shown.

Claims

1. A protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet, characterized in that, The protection control method specifically includes the following steps: Step 1: Determine the safety margin characterization of the inlet; Step 2: Based on the safety margin characterization of the inlet in Step 1, select the target position of the shock train; Step 3: Based on the target position of the shock train selected in Step 2, monitor the safety margin of the inlet; Step 4: Based on the safety margin of the inlet monitored in Step 3, perform closed-loop control on the inlet margin; Specifically, Step 1 is to quantitatively characterize the safety margin as the distance between the leading edge of the shock train and the throat, and the definition formula of the safety margin is: （1） Among them L shock is the length of the shock wave train, L iso is the length of the inlet - isolator.

2. The protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet according to claim 1, characterized in that Specifically, Step 2 is to select a position far from the background shock reflection point as the target position of the shock train when performing equal margin control on the inlet; 3. The protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet according to claim 1, wherein, Specifically, Step 3 is to obtain the leading edge position of the shock train in the isolator by using the pressure ratio method; 4. The protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet according to claim 3, characterized in that, First, record the pressure values at several wall positions under the flow-through state as the reference pressure , and record the pressure at each moment at each position as ; thus, the pressure ratio vector is obtained as shown in the following formula: （2） Interpolate based on the pressure ratio vector and design a threshold according to the actual flow field situation; when the pressure ratio vector reaches this threshold, an estimated value of the leading edge position of the shock train in the isolator can be obtained.

5. The protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet according to claim 4, characterized in that, The method for estimating the leading edge position of the shock train is summarized in the form of Equation (3); where I is the interpolation method, x tr is the position of the measured pressure value, pr des = 1.5: （3）。 6. The protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet according to claim 1, wherein, Specifically, Step 4 includes the following steps: Step 4.1: Select 10 equally spaced pressure measurement points on the cowl side and the forebody side in the inlet-isolator; Step 4.2: Process the pressure values obtained from the pressure measurement points in Step 4.1; 7. The protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet according to claim 6, wherein, Specifically, the processing of the obtained pressure values in Step 4.2 is: Step 4.2.1: Use the pressure ratio method to estimate the leading edge position of the shock train at the current moment; Step 4.2.2: Design a PI controller; Step 4.2.3: Use the PID Tuner toolbox to adjust the parameters in the PI controller. The form of the PI controller is , and perform equal margin closed-loop control of the air inlet.

8. The protection control method for characterizing the safety margin of the leading edge position of the shock train in a hypersonic inlet according to claim 7, characterized in that, Specifically, in Step 4.2.2, designing the PI controller is to give a back pressure boundary condition to the outlet of the hypersonic inlet and observe the change of the leading edge position of the shock train in the inlet-isolator; Use the system identification toolbox to take the back pressure boundary condition as the input and the corresponding change of the leading edge position of the shock train as the output, and identify a first-order transfer function; 9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the method steps described in any one of claims 1-8.

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