Engine cooling control system based on fuzzy control pid

Abstract

The invention discloses an engine cooling control system based on fuzzy control pid, which is characterized in that an oxidant storage tank, a cooling liquid storage tank and a fuel storage tank are respectively converged to an injector through an oxidant pipeline, a cooling liquid pipeline and a fuel pipeline and then enter an engine combustion chamber to generate high-temperature and high-pressure fuel gas, and the fuel gas enables the temperature of a thrust chamber to rise; when the cooling system controller detects that the temperature of the thrust chamber rises to exceed the safe temperature, the cooling system controller outputs PWM waves with different duty ratios through a fuzzy pid control strategy to control an electromagnetic valve switch on a cooling liquid pipeline to control the flow of cooling liquid. High-temperature steam generated by heat absorption and evaporation of cooling liquid in the cooling liquid pipeline flows through the heat exchanger to preheat fuel, stable operation of the cooling system can be guaranteed to the maximum extent through the double-system design, and the fault rate can be greatly reduced through the simple design of the auxiliary system. The system controls the cooling temperature within a set range, so that the fuel can be heated through the regeneration channel by using the residual temperature, and the use amount of the cooling liquid can be saved.

Description

Technical Field

[0001] The invention relates to the technical field of aerospace engine cooling control, and in particular to an engine cooling control system based on fuzzy control PID. Background Art

[0002] When a liquid rocket engine is ignited, the combustion chamber temperature can reach over 3800K, such as a high-pressure regenerative liquid oxygen / kerosene engine; the pressure can reach over 30MPa. It is precisely because of the high temperature and high pressure thermal conditions generated by the combustion of liquid rocket engine propellants that the heat flux density of the combustion gas to the outside of the thrust chamber can be as high as 10-160MW / m2, which makes the structural materials of the engine thrust chamber unable to withstand such a special working environment. Therefore, the cooling of the rocket engine becomes an indispensable means to ensure its normal operation and service life.

[0003] There are many ways to cool modern rocket engines, mainly divided into external cooling, internal cooling, heat capacity cooling, ablation cooling, thermal insulation protection, etc. Internal cooling refers to the use of propellant to form a relatively low temperature liquid or gas protective layer on the inner wall of the engine, increasing the thermal resistance of the heat transfer from the fuel gas to the outer wall of the engine, thereby reducing the heat flux density of the fuel gas to the chamber wall, and achieving the purpose of reducing the engine wall temperature; according to the different ways in which the coolant enters the engine combustion chamber, there are mainly three methods: shielding cooling, film cooling and sweating cooling. Ablation cooling refers to a cooling method in which the surface of the engine wall is formed with special materials, and the evaporation, melting or chemical reaction of the special materials absorbs the heat transferred from the fuel gas to the engine chamber wall, and at the same time produces decomposition gas densely covering the wall, forming a low-temperature gas protective layer to isolate the high-temperature fuel gas. Thermal insulation protection refers to a thermal protection method in which a special material with low thermal conductivity and high surface allowable temperature is used to form a thermal insulation coating on the inner wall of the engine, thereby reducing the temperature of the engine wall by increasing the thermal resistance of the fuel gas to the engine wall. Capacitive cooling is a means of achieving thermal protection through the absorption of heat by the thrust chamber wall material. Generally, it is hoped that the wall material has a high thermal conductivity and a low thermal resistance. There are two main types of external cooling: convection cooling and radiation cooling. Radiation cooling refers to the radiation heat dissipation of the propellant combustion products to the engine chamber wall and the surrounding space of the engine to cool the engine itself; convection cooling is a cooling method that absorbs the heat transferred from the engine through the convection heat exchange of the cooling fluid in the engine's external cooling channel to reduce the engine wall temperature and achieve the cooling purpose. There are mainly two types of cooling: regenerative cooling and emission cooling. Regenerative cooling is a cooling method that uses a fluid with better cooling performance in the propellant component to enter the cooling channel between the inner and outer walls of the engine to absorb the heat transferred from the wall and finally enter the combustion chamber of the engine for combustion, so as to recycle the heat of the fuel gas and "regenerate" the energy; emission cooling also belongs to convection cooling, but the coolant does not enter the combustion chamber to continue burning after absorbing the heat of the engine outer wall in the cooling channel, but is directly discharged to the external environment.

[0004] The existing exhaust cooling does not control the flow of the coolant, but simply turns on the coolant to cool the engine, which will inevitably cause energy waste of the propellant and specific impulse loss of the engine. And this method will also cause waste of coolant. In view of the above problems, the present invention uses a control algorithm to control the flow of the coolant in the cooling channel to control the engine temperature within a suitable range. Within this temperature range, the engine will not be ablated due to excessive temperature, and a certain amount of gas heat can be recovered through regenerative cooling to improve combustion efficiency. The coolant absorbs heat and evaporates in the cooling channel, and the high-temperature steam generated flows through the heat exchanger to preheat the fuel and further recover the gas heat. Summary of the invention

[0005] The present invention provides an engine cooling control system based on fuzzy control PID, which is used to control the temperature of the thrust chamber of the aerospace engine to be kept within a certain range during the ignition process, so as to ensure the engine safety while using as little coolant as possible and to retain the heat of the fuel gas that can be recovered by regenerative cooling.

[0006] The technical solution adopted by the present invention is an engine cooling control system based on fuzzy control pid. The oxidant tank, the coolant tank and the fuel tank are respectively collected to the injector through the oxidant pipeline, the coolant pipeline and the fuel pipeline and then enter the engine combustion chamber to generate high-temperature and high-pressure combustion gas. The combustion gas causes the thrust chamber temperature to rise. The cooling system controller detects that the thrust chamber temperature rises to exceed the safe temperature. The cooling system controller outputs PWM waves with different duty cycles through the fuzzy pid control strategy to control the solenoid valve switch on the coolant pipeline to control the flow of the coolant. The coolant in the coolant pipeline absorbs heat and evaporates to generate high-temperature steam that flows through the heat exchanger to preheat the fuel.

[0007] The cooling control system controller includes a main system controller and an auxiliary system controller, and uses FPGA as the control core of the main system. The control signals sent by the main system controller and the auxiliary system controller drive the solenoid valve through the PWM control circuit. The external temperature is converted into an analog signal through a temperature sensor and a temperature transmitter and input to the main system controller and the auxiliary system controller. The main system controller has an embedded fuzzy pid control algorithm, and the auxiliary system controller outputs a forced reset signal to the main system controller for restarting the main system controller.

[0008] The main system controller is connected to the host computer via Ethernet. The host computer inputs the preset temperature range into the main system controller via Ethernet, and the main system controller returns the real-time temperature signal to the host computer for display.

[0009] The PWM control circuit inputs a PWM control signal into a control port of a solid-state relay, and controls the opening of the solenoid valve through an output port of the solid-state relay.

[0010] The PWM control circuit is also provided with a release circuit for releasing the freewheeling current of the solenoid valve and accelerating the closing of the solenoid valve.

[0011] The beneficial effects of the present invention are as follows: the present invention adopts FPGA as the control core of the main system to realize the functions of fuzzy PID controller and analog signal conversion to PWM signal. The auxiliary system will adopt a relatively simple feedback control. When the engine temperature is higher than the upper limit of the temperature range, the solenoid valve is normally opened to maximize the flow of the coolant. When the engine temperature is lower than the lower limit of the temperature range, the solenoid valve is closed to save coolant. The dual system design can ensure the stable operation of the cooling system to the greatest extent possible, and the simple design of the auxiliary system can greatly reduce the failure rate. The system controls the cooling temperature within a set range, which can not only use the residual temperature to heat the fuel through the regeneration channel, but also save the amount of coolant. The dual system design can ensure the stable operation of the system and greatly reduce the probability of engine ablation. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of aerospace engine cooling control.

[0013] Figure 2 This is the structural block diagram of the cooling control system controller.

[0014] Figure 3 This is a schematic diagram of the PWM control circuit.

[0015] Markings in the figure: 1-oxidizer tank, 2-coolant tank, 3-fuel tank, 4-oxidizer pipeline, 5-coolant pipeline, 6-fuel pipeline, 7-injector, 8-engine body, 9-cooling system controller, 10-heat exchanger. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0017] The general method for exhaust cooling during aerospace engine ignition is to open the cooling channel valve during the ignition process, and then close the valve after a period of time after the ignition is completed. This control method not only causes energy waste of propellant and specific impulse loss of the engine, but also has a problem with the consumption of coolant. In order to solve the above problems and improve the safety of aerospace engine ignition, a set of engine cooling control system based on fuzzy PID control is designed. The system uses FPGA as the control core, has the functions of multi-channel temperature acquisition and output PWM wave to control the switch of the solenoid valve. The designed auxiliary system can take effect when the main system fails and the cooling effect is poor. When the auxiliary system takes over the control of the cooling channel solenoid valve, it outputs a large flow of coolant for rapid cooling control when the temperature exceeds the ideal range. This method does not require complex control logic and greatly reduces the probability of failure, but this method consumes a lot of coolant. Therefore, under normal circumstances, the main system control strategy is used for cooling control.

[0018] The present invention aims at the problem that the thrust chamber of aerospace engines is prone to local ablation or even burning under high chamber pressure. In order to ensure that the aerospace engine can work normally, a set of engine cooling control system based on fuzzy PID control algorithm is designed. The whole system is divided into a main system and an auxiliary system, wherein the main system uses the acquired thrust chamber temperature through the built-in fuzzy PID algorithm to output a PWM signal to control the cooling component. The principle of the cooling component is to use different PWM signal duty ratios to control the different switching durations of the solenoid valve within a unit cycle, thereby controlling the flow of coolant flowing through the solenoid valve. The auxiliary system is a backup for the main system. When the main system fails, causing the engine temperature to continue to rise, the auxiliary system starts to work and uses a large flow of coolant to reduce the engine temperature in a short time.

[0019] The aerospace engine cooling control of the present invention is as follows Figure 1 As shown, the oxidant and fuel enter the engine combustion chamber through the injector 7 to burn and generate high-temperature and high-pressure combustion gas. The heat transfer of the combustion gas to the outside of the thrust chamber causes the thrust chamber temperature to rise. The cooling system controller 9 has a multi-channel temperature acquisition function. When it is detected that the thrust chamber temperature rises to a temperature exceeding the safe temperature, in order to protect the thrust chamber from being ablated, the controller outputs PWM waves with different duty ratios through the fuzzy pid control strategy to control the solenoid valve switch on the coolant pipeline, thereby controlling the flow of coolant in the coolant pipeline 5. When the temperature is lower than the safe temperature, the solenoid valve can be closed to keep the thrust chamber temperature within the safe range. The high-temperature vapor generated by the heat-absorbing evaporation of the coolant in the cooling channel flows through the heat exchanger 10, and the fuel is preheated in the heat exchanger 10 to further recover the heat of the combustion gas.

[0020] The control system structure diagram is as follows Figure 2As shown in the figure, the system is divided into a main system and an auxiliary system. The external temperature is converted into an analog signal that can be recognized by the controller pin through the temperature sensor and the temperature transmitter. The main system controller is embedded with a fuzzy pid control algorithm, which can output the corresponding control signal after calculating the input temperature analog signal. Since the control signal power output by the main system controller is not enough to directly drive the solenoid valve, a PWM control circuit must be added in the middle. The power supply of the control circuit and the controller is supplied by the power module. The main controller and the host computer are connected through Ethernet. The host computer inputs the preset temperature range into the main controller through Ethernet, and the main controller returns the real-time temperature signal to the host computer for display. In addition to the main system controller, there is also an auxiliary system controller. When the main system controller fails, the auxiliary system can take over the control of the PWM control circuit. There is no complex control algorithm in the auxiliary system, only a simple negative feedback circuit. When the temperature exceeds the preset range, the solenoid valve is opened, and when the temperature is lower than the preset range, the solenoid valve is closed. At the same time, the auxiliary system will output a forced reset signal to the main system to restart the main system.

[0021] PWM control circuit such as Figure 3 The PWM control signal output by the system shown is input to the control port of the solid-state relay. When the control port is at a high level, 24V DC power controls the solenoid valve to open through the solid-state relay output port. When the control port is at a low level, 24V DC power cannot pass through the solid-state relay output port. At the same time, the freewheeling current of the solenoid valve will be released as soon as possible through the release circuit to accelerate the closing of the solenoid valve.

[0022] The present invention adopts FPGA as the control core of the main system to realize the functions of fuzzy PID controller and analog signal to PWM signal conversion. The auxiliary system will adopt a relatively simple feedback control. When the engine temperature is higher than the upper limit of the temperature range, the solenoid valve is normally opened to maximize the flow of the coolant. When the engine temperature is lower than the lower limit of the temperature range, the solenoid valve is closed to save coolant. The dual system design can ensure the stable operation of the cooling system to the greatest extent possible, and the simple design of the auxiliary system can greatly reduce the failure rate. The system controls the cooling temperature within a set range, which can not only use the residual temperature to heat the fuel through the regeneration channel, but also save the amount of coolant. The dual system design can ensure the stable operation of the system and greatly reduce the probability of engine ablation.

[0023] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An engine cooling control system based on fuzzy control PID, characterized in that: The oxidant tank (1), the coolant tank (2) and the fuel tank (3) are respectively collected at the injector (7) through the oxidant pipeline (4), the coolant pipeline (5) and the fuel pipeline (6) and then enter the engine combustion chamber to generate high-temperature and high-pressure combustion gas. The combustion gas causes the thrust chamber temperature to rise. The cooling system controller (9) detects that the thrust chamber temperature rises to exceed the safe temperature. The cooling system controller (9) outputs PWM waves with different duty ratios through the fuzzy pid control strategy to control the electromagnetic valve switch on the coolant pipeline (5) to control the flow of the coolant. The coolant in the coolant pipeline (5) absorbs heat and evaporates to generate high-temperature steam that flows through the heat exchanger (10) to preheat the fuel.

2. The engine cooling control system based on fuzzy control PID according to claim 1 is characterized by: The cooling control system controller (9) comprises a main system controller and an auxiliary system controller, and adopts FPGA as the control core of the main system. The control signals sent by the main system controller and the auxiliary system controller drive the solenoid valve through the PWM control circuit. The external temperature is converted into an analog signal through a temperature sensor and a temperature transmitter and input to the main system controller and the auxiliary system controller. The main system controller has a built-in fuzzy pid control algorithm, and the auxiliary system controller outputs a forced reset signal to the main system controller for restarting the main system controller.

3. The engine cooling control system based on fuzzy control PID according to claim 1, characterized in that: The main system controller is connected to the host computer via Ethernet. The host computer inputs the preset temperature range into the main system controller via Ethernet, and the main system controller returns the real-time temperature signal to the host computer for display.

4. The engine cooling control system based on fuzzy control PID according to claim 1, characterized in that: The PWM control circuit inputs a PWM control signal into a control port of a solid-state relay, and controls the opening of the solenoid valve through an output port of the solid-state relay.

5. The engine cooling control system based on fuzzy control PID according to claim 4 is characterized in that: The PWM control circuit is also provided with a release circuit for releasing the freewheeling current of the solenoid valve and accelerating the closing of the solenoid valve.

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