A method for restarting a flying-stinger coupled micro turbojet engine

Abstract

This invention discloses a method for restarting a flight-engine coupled micro turbojet engine. The turbojet engine performs fault diagnosis and emergency handling based on collected parameters. If a rapid restart is not possible, the aircraft determines a restart threshold, plans an optimal trajectory, and adjusts ballistic parameters such as altitude, speed, and attitude angle to create favorable conditions for engine restart, thus achieving in-flight restart. This method is low-cost, easy to implement, and can achieve rapid engine restart by combining aircraft state control. It has significant reference value and potential for widespread application in related fields.

Description

Technical Field

[0001] This invention belongs to the field of aircraft technology, specifically relating to a restart method for a micro turbojet engine coupled with a flight engine. Background Technology

[0002] A turbojet engine is a type of turbine engine that compresses air through a centrifugal impeller, mixes it with atomized fuel, and generates thrust through combustion and expansion. Turbojet engines are primarily started using two methods: pyrotechnic starting and electric starting. Pyrotechnic starting requires a pyrotechnic igniter and a propellant starter mounted on the engine fuselage and is for single use only. Electric starting is cheaper and can be repeated after in-flight engine failure, but its success rate is affected by the starting envelope. The low temperature, oxygen-deficient environment, and high airflow velocity encountered after in-flight engine failure make ignition difficult, and engine is prone to failure during preheating and acceleration, resulting in a much lower restart success rate than on the ground. Traditional turbojet engine restart procedures do not simultaneously consider flight status control and start-up control. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a method for restarting a flight-engine coupled micro turbojet engine. The turbojet engine performs fault diagnosis and emergency handling based on collected parameters. If a rapid restart is not possible, the aircraft determines a restart threshold, plans an optimal trajectory, and adjusts ballistic parameters such as altitude, speed, and attitude angle to create favorable conditions for the turbojet engine's restart, thus achieving in-flight restart. This invention is low-cost, easy to implement, and can achieve rapid restart of the turbojet engine by combining it with aircraft state control. It has significant reference value and potential for widespread application in related fields.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows: Step 1: Fault diagnosis and emergency handling; Step 2: Restart the coupled turbojet engine; Step 3: Restart threshold calculation.

[0005] Preferably, step 1 specifically comprises: The information collected for the turbojet engine includes exhaust temperature, engine speed, starter motor speed, communication status between the turbojet controller and the host computer, communication status between the turbojet controller and the turbine sensor, fuel pump voltage, starter motor voltage and current, fuel pressure, and solenoid valve status. Based on the collected information, a fault database and corresponding emergency handling methods are constructed, as follows: 1) The turbojet controller failed to communicate with the turbine sensor, and the oil pump maintained the current power. 2) The turbojet controller failed to communicate with the host computer, maintaining the control state of the engine's last valid frame; 3) If the current exceeds the set value, the oil pump voltage will be limited; 4) If the speed command is abnormal and exceeds the designed operating speed range, the speed command will be limited; 5) If the exhaust temperature is abnormal, report the corresponding fault and maintain the current status; 6) If the fuel pressure is abnormal, report the corresponding fault and maintain the current status; 7) If the engine speed is abnormal, if the speed is too high and exceeds the maximum speed threshold, the fuel supply will be reduced and the speed will be lowered to a safe range; if the speed is too low and falls below the minimum speed threshold, the turbojet engine will be determined to have stalled and proceed to step 2.

[0006] Preferably, step 2 specifically comprises: When a turbojet engine exhibits a decrease in combustion chamber temperature and a decrease in engine speed, and the current engine speed is lower than the minimum engine speed threshold, the turbojet engine is determined to shut down. If the turbojet engine stalls in mid-air, an immediate restart attempt is made. If the restart attempt fails N times consecutively, or the restart time exceeds the time threshold, it indicates that the current ballistic parameters do not meet the restart threshold, and the relevant ballistic parameters of the aircraft need to be adjusted. The turbojet controller sends a shutdown command, the turbojet engine stops, the turbojet engine restart threshold is calculated, the optimal trajectory is planned, and the altitude, speed, and pitch angle ballistic parameters are adjusted until the turbojet engine threshold meets the conditions for restart.

[0007] Preferably, step 3 specifically comprises: The factors affecting the restart of a turbojet engine are incoming flow velocity, altitude, and pitch angle. Incoming flow velocity affects the mass flow rate entering the engine, altitude affects air density, and pitch angle affects intake efficiency. The formula for calculating the restart conditions of a turbojet engine is as follows: (1) (2) (3) (4) (5) (6) in: Altitude; : Incoming flow velocity; Pitch angle; :high Minimum restart speed at the location; :speed Maximum lifting height at that time; , Height boundary parameters, obtained through experimental calibration; Minimum restart speed at sea level; Maximum pitch angle; High influence coefficient, obtained through experimental calibration; Threshold factor; : Natural constant; The threshold condition is that Simultaneously positive; if not, adjustments need to be made to altitude, incoming flow velocity, and pitch angle, with the following control commands: Define control variables ,in: Vertical speed command; Acceleration command; Pitch rate command; (7) (8) (9) in Vertical speed command limit; : Upper limit of acceleration commands: : Upper limit of pitch rate command; : Symbolic function; Using numerical optimal control methods, the nonlinear programming solution is solved in discrete time to obtain the optimal solution of the control quantity corresponding to the shortest time.

[0008] Preferably, N=2.

[0009] Preferably, the time threshold is 180s.

[0010] The beneficial effects of this invention are as follows: The advantages of this invention are low cost, easy implementation, and the ability to achieve rapid restart of turbojet engines by combining with aircraft status control. It has high reference value and potential for promotion in related fields. Attached Figure Description

[0011] Figure 1 This is a flowchart of the method of the present invention.

[0012] Figure 2 This is a schematic diagram of the restart process of a turbojet engine after it has been shut down.

[0013] Figure 3 This is a diagram illustrating the process of a turbojet engine failing to restart after shutting down, and waiting for the aircraft to descend before restarting. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] This invention proposes a method for restarting a flight-engine coupled turbojet engine. When the turbojet engine fails to start, the aircraft performs a restart margin assessment, plans the optimal trajectory, and adjusts ballistic parameters such as altitude, speed, and pitch angle to create favorable conditions for the turbojet engine to restart, thereby achieving in-flight restart of the turbojet engine.

[0016] 1. Fault diagnosis and emergency handling methods; The turbojet engine collects information including exhaust temperature, engine speed, starter motor speed, communication status between the turbojet controller and the host computer, communication status between the turbojet controller and the turbine sensor, fuel pump voltage, starter motor voltage, current, fuel pressure, and solenoid valve status. Based on the above information, this invention establishes a fault database and corresponding emergency handling methods, as detailed below: 1) The turbojet controller failed to communicate with the turbine sensor, and the oil pump maintained the current power. 2) The turbojet controller failed to communicate with the host computer, maintaining the control state of the last valid frame of the engine. 3) If the current is too high, the oil pump voltage will be limited. The specific value will be obtained based on the statistical data of the engine's normal operating current. 4) When the speed command is abnormal and exceeds the design operating speed range, the speed command will be limited. The specific limit value depends on the engine design parameters. 5) If the exhaust temperature is abnormal, report the corresponding fault and maintain the current status; 6) If the fuel pressure is abnormal, report the corresponding fault and maintain the current status; 7) If the engine speed is abnormal, if the speed is too high and exceeds the maximum speed threshold, the fuel supply will be reduced to lower the speed to a safe range; if the speed is too low and falls below the minimum speed threshold, the turbojet engine will be determined to have stalled and the engine will be restarted. 2. Restart method for a coupled turbojet engine; Turbojet engines exhibit a decrease in combustion chamber temperature and engine speed. If the current engine speed falls below a minimum speed threshold, the engine is considered to have shut down. This minimum speed threshold represents the lowest possible speed at which the engine can operate stably, and it increases with altitude, as shown in Table 1 below. This speed varies depending on the engine type.

[0017] Table 1 Minimum Speed ​​(Example)

[0018] If the turbojet engine shuts down in mid-air, an immediate restart attempt will be made. If restart attempts fail repeatedly, or the restart time exceeds a threshold, it indicates that the current ballistic parameters do not meet the restart threshold, and the relevant ballistic parameters of the aircraft need to be adjusted. The turbojet controller sends a shutdown command, the turbojet engine shuts down, the turbojet engine restart threshold is calculated, the optimal trajectory is planned, and ballistic parameters such as altitude, speed, and pitch angle are adjusted until the turbojet engine threshold is met, at which point it can be restarted.

[0019] 3. Restart threshold calculation; The main factors affecting turbojet engine restart are incoming air velocity, altitude, and pitch angle. Incoming air velocity affects the mass flow rate into the engine, altitude affects air density, and pitch angle affects intake efficiency.

[0020] The formula for calculating the restart conditions of a turbojet engine is as follows. (1) (2) (3) (4) (5) (6) Engine start failure is usually due to not meeting the restart threshold, and the corresponding calculation result is: <0; The restart threshold needs to be adjusted via flight path to reach the target value as quickly as possible. The threshold must meet the following conditions: Both are positive.

[0021] Defineable control variables ,in: Vertical speed command (m / s); Acceleration command (m / s²); Pitch rate command (rad / s); (8) (9) (10) Using numerical optimal control methods, the nonlinear programming solution can be solved in discrete time to obtain the optimal solution of the control quantity corresponding to the shortest time.

[0022] Example: See the method for restarting the coupling of the fly-starter. Figure 1 The turbojet controller immediately restarts the engine upon detecting engine shutdown or receiving a start command. If the engine fails to start, a counter is incremented by 1. If the number of start attempts exceeds two or the starting time exceeds 180 seconds, the turbojet controller issues a stop command, and the engine stops. A restart threshold is then calculated. When the value is less than 0, the trajectory is adaptively planned based on the current initial parameters, and the ballistic parameters are adjusted.

[0023] Restarting the engine during normal operation Figure 2 .like Figure 2 As shown, at time "1", the turbojet engine speed suddenly begins to drop. After 1.8 seconds, the speed drops below the minimum speed, and the turbojet controller determines that the turbojet engine is shut down and stops supplying fuel. The fuel pump voltage becomes 0. After 10 seconds, the turbojet engine speed meets the conditions and begins to restart. The engine restart is completed in about 55 seconds and enters the running state.

[0024] After the engine shut down, the restart failed. The aircraft successfully restarted after parameter adjustments. Figure 3 As shown in the figure, at time "1", the turbojet engine shut down due to low speed. Approximately 5 seconds later, the engine attempted to start for the first time. After 48 seconds, the engine failed to start and immediately began a second attempt. After 60 seconds, the engine stopped. The aircraft rapidly descended, reduced speed, and adjusted its attitude. After 218 seconds, the turbojet engine restarted and successfully entered operational status.

[0025] The initial parameters for calculating the restart threshold of the turbojet engine are shown in Table 2: Table 2 Initial Parameters for Turbojet Engine Restart Threshold Calculation

[0026] The calculation process is as follows:

[0027]

[0028]

[0029] <0, the restart threshold is not met. The calculated control commands are as follows:

[0030]

[0031] .

Claims

1. A restart method for a micro turbojet engine with engine-driven coupling, characterized in that, Includes the following steps: Step 1: Fault diagnosis and emergency handling; Step 2: Restart the coupled turbojet engine; Step 3: Restart threshold calculation.

2. The restart method for a micro turbojet engine coupled with a flight engine according to claim 1, characterized in that, Step 1 specifically involves: The information collected for the turbojet engine includes exhaust temperature, engine speed, starter motor speed, communication status between the turbojet controller and the host computer, communication status between the turbojet controller and the turbine sensor, fuel pump voltage, starter motor voltage and current, fuel pressure, and solenoid valve status. Based on the collected information, a fault database and corresponding emergency handling methods are constructed, as follows: 1) The turbojet controller failed to communicate with the turbine sensor, and the oil pump maintained the current power. 2) The turbojet controller failed to communicate with the host computer, maintaining the control state of the engine's last valid frame; 3) If the current exceeds the set value, the oil pump voltage will be limited; 4) If the speed command is abnormal and exceeds the designed operating speed range, the speed command will be limited; 5) If the exhaust temperature is abnormal, report the corresponding fault and maintain the current status; 6) If the fuel pressure is abnormal, report the corresponding fault and maintain the current status; 7) If the engine speed is abnormal, if the speed is too high and exceeds the maximum speed threshold, the fuel supply will be reduced and the speed will be lowered to a safe range; if the speed is too low and falls below the minimum speed threshold, the turbojet engine will be determined to have stalled and proceed to step 2.

3. The restart method for a micro turbojet engine coupled with a flight engine according to claim 2, characterized in that, Step 2 specifically involves: When a turbojet engine exhibits a decrease in combustion chamber temperature and a decrease in engine speed, and the current engine speed is lower than the minimum engine speed threshold, the turbojet engine is determined to shut down. If the turbojet engine stalls in mid-air, immediately attempt to restart. If the restart attempt fails N times in a row, or the restart time exceeds the time threshold, it indicates that the current ballistic parameters do not meet the restart threshold and the relevant ballistic parameters of the aircraft need to be adjusted. The turbojet controller sends a shutdown command, the turbojet engine stops, the turbojet engine restart threshold is calculated, the optimal trajectory is planned, and the altitude, speed, pitch angle and ballistic parameters are adjusted until the turbojet engine restarts when the threshold is met.

4. The restart method for a micro turbojet engine coupled with a flight engine according to claim 3, characterized in that, Step 3 specifically involves: The factors affecting the restart of a turbojet engine are incoming flow velocity, altitude, and pitch angle. Incoming flow velocity affects the mass flow rate entering the engine, altitude affects air density, and pitch angle affects intake efficiency. The formula for calculating the restart conditions of a turbojet engine is as follows: （1） （2） （3） （4） （5） （6） in: Altitude; : Incoming flow velocity; Pitch angle; :high Minimum restart speed at the location; :speed Maximum lifting height at that time; , Height boundary parameters, obtained through experimental calibration; Minimum restart speed at sea level; Maximum pitch angle; High influence coefficient, obtained through experimental calibration; Threshold factor; : Natural constant; The threshold condition is that Simultaneously positive; if not, adjustments need to be made to altitude, incoming flow velocity, and pitch angle, with the following control commands: Define control variables ,in: Vertical speed command; Acceleration command; Pitch rate command; （7） （8） （9） in Vertical speed command limit; : Upper limit of acceleration commands: : Upper limit of pitch rate command; : Symbolic function; Using numerical optimal control methods, the nonlinear programming solution is solved in discrete time to obtain the optimal solution of the control quantity corresponding to the shortest time.

5. The restart method for a micro turbojet engine coupled with a flight engine according to claim 4, characterized in that, The value of N is 2.

6. The restart method for a micro turbojet engine coupled with a flight engine according to claim 5, characterized in that, The time threshold is 180s.

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