Liquid oxygen methane electric pump supercharged engine system and thrust control method thereof

Abstract

The invention discloses a liquid oxygen methane electric pump supercharged engine system and a thrust control method thereof.The engine system is mainly composed of a propellant supply system and a thrust chamber, methane serves as fuel, liquid oxygen serves as an oxidizing agent, and the methane and the liquid oxygen are pumped out of a storage tank through a motor pump. Methane and liquid oxygen enter the combustion chamber after being pressurized by the motor pump, are mixed and ignited, and generate a violent chemical reaction in the combustion chamber to release a large amount of heat energy, and the heat energy is converted into kinetic energy to generate thrust. According to the control system, a liquid oxygen path propellant adjusting control controller and a methane path propellant adjusting control controller are connected in series, so that accurate adjustment of the chamber pressure and the mixing ratio of a combustion chamber is achieved, and then accurate adjustment of target thrust is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of rocket engines, and in particular to a liquid oxygen-methane electric pump supercharged engine system and a thrust control method thereof. Background Art

[0002] Rocket engines provide power for rocket flight. Traditional solid rocket engines are usually used for rocket boosters or certain types of missiles because of their simple structure. However, the fuel propellant of solid rocket engines has solidified before launch, which means that its combustion cannot be terminated. Therefore, once the engine is ignited, it can only continue to burn until the fuel is exhausted, and its flexibility is poor. With the continuous innovation and breakthroughs in battery and motor technology, electric pump liquid rocket engines are gradually emerging due to their unique advantages. Electric pump engines can quickly respond to various instructions in a short time, greatly improving the flexibility and efficiency of rocket launches. At the same time, its adjustment process is simple, and precise thrust adjustment can be achieved without complex operating procedures, allowing the rocket to better adapt to various changes during flight. In addition, the energy input of electric pump liquid rocket engines is controllable, and the energy supply can be adjusted according to actual needs to achieve more accurate energy management, providing a strong guarantee for the safe and stable flight of rockets.

[0003] In the field of rocket engine technology, the thrust regulation of reusable engines is mainly achieved by changing the fuel supply, oxidizer supply or combustion chamber pressure of the engine. Among them, the supply of fuel and oxidizer is the main factor affecting the engine thrust. By accurately controlling the mixing ratio and flow rate of fuel and oxidizer, the engine thrust can be continuously adjusted. In addition, the combustion chamber pressure also has an important influence on the engine thrust. By adjusting the combustion chamber pressure, the combustion speed and combustion efficiency can be changed, thereby achieving the adjustment of the engine thrust.

[0004] At present, the research on thrust regulation control of liquid oxygen-methane pump variable thrust engines is still insufficient, and the existing models are relatively preliminary and need further in-depth research and improvement. Summary of the invention

[0005] In response to the control requirements of rocket engines, the present invention provides a liquid oxygen-methane pump variable thrust engine system and a thrust control method, so as to improve the thrust response accuracy of the engine, make the system flow regulation more stable, and reduce overshoot. The reduction of overshoot prolongs the service life of the material and reduces the difficulty of reusing the material.

[0006] To achieve the above-mentioned purpose, the present invention provides a liquid oxygen-methane electric pump booster engine system solution, which is mainly composed of a propellant supply system and a thrust chamber.

[0007] The thrust chamber is composed of key components such as the pintle injector, combustion chamber, nozzle and regenerative cooling channel. The cooling channel adopts a tube bundle cooling channel to achieve effective thermal management and ensure that the thrust chamber wall temperature does not exceed the material temperature range.

[0008] The propellant supply system consists of a motor, inverter, battery, pump, fuel valve, and liquid oxygen valve.

[0009] Fuel and oxidant are provided to the combustion chamber through two channels. The fuel circuit uses methane as fuel, and the oxidant circuit uses liquid oxygen as oxidant. The two pipelines, methane circuit and liquid oxygen circuit, are used for transmission.

[0010] After being pressurized by the motor pump, methane enters the cooling channel along the pipeline. The cooling channel goes around the thrust chamber and then enters the combustion chamber through the pintle injector. After being pressurized by the motor pump, liquid oxygen directly enters the combustion chamber through the pintle injector along the pipeline.

[0011] After entering the combustion chamber, methane and liquid oxygen undergo a time-delayed mixing reaction, generate energy, and are ejected through the tail nozzle of the thrust chamber, generating huge kinetic energy as thrust. In order to effectively reduce the temperature of the thrust chamber wall, the thrust chamber wall is cooled by regenerative cooling.

[0012] The present invention selects the thrust value as the actual control target. However, it is difficult to directly measure the thrust value, so some key factors affecting the thrust value are first found, and the thrust is adjusted by controlling these key factors. In the process of rocket engine thrust adjustment, the propellant flow rate, the combustion chamber pressure and the throat nozzle area are the more critical influencing factors. These parameters work together to affect the rocket engine thrust adjustment, and there is an influence relationship between the parameters. The nozzle throat area is a fixed value, so the combustion chamber pressure and the propellant flow rate are selected as the key factors for adjusting the engine thrust.

[0013] To achieve the adjustment of thrust, the propellant mass flow rate and the combustion chamber pressure can be adjusted. Since the propellant mass flow rate can effectively control the mixing ratio, the present invention finally chooses to adjust the combustion chamber pressure and the mixing ratio to achieve the adjustment of the engine thrust.

[0014] The present invention also provides a method for controlling the thrust of a liquid oxygen-methane electric pump supercharged engine. The method comprises the following steps:

[0015] Step S1, the control system needs to achieve the goal of controlling the combustion chamber pressure and the mixing ratio. The entire control system is divided into two parts, one is the liquid oxygen circuit propellant adjustment control, and the other is the methane circuit propellant adjustment control. The two controllers are connected in series, and the output value of the liquid oxygen controller is combined with the mixing ratio conversion as the input value of the methane controller.

[0016] Step S1.1, first give the combustion chamber reference pressure value and the calculated value of the mixing ratio, calculate the required liquid oxygen flow reference value of the liquid oxygen circuit according to the combustion chamber pressure reference value, simulate to obtain the actual liquid oxygen flow value of the liquid oxygen circuit, design a liquid oxygen circuit controller with given parameters, adjust and control the liquid oxygen flow, input the actual value and reference value of the liquid oxygen flow into the liquid oxygen controller, calculate and output the liquid oxygen circuit electric pump voltage signal, and adjust the motor speed through the voltage signal until the given target value is achieved.

[0017] Step S1.2, after the liquid oxygen circuit is adjusted, the mixing ratio signal is input, and the reference value of the methane circuit flow is calculated by the actual value of the liquid oxygen flow obtained by the above calculation, and a methane circuit controller with given adjustment parameters is designed to adjust the methane flow. The actual value and reference value of the methane flow are input into the methane controller, and the voltage signal of the methane circuit electric pump is calculated and output. The speed of the methane circuit motor is adjusted by the voltage signal until the given target value is achieved, completing the entire control process.

[0018] The present invention has the following advantages:

[0019] (1) The present invention discloses a liquid oxygen-methane rocket variable thrust engine system with electric pump boosting, which adopts a variable thrust electric adjustment method to achieve rapid adjustment of the engine thrust, and has the advantages of fast response speed and high adjustment accuracy.

[0020] (2) The present invention discloses a cascade PI control thrust adjustment scheme for a liquid oxygen-methane rocket variable thrust engine, which can achieve target thrust ratio adjustment. After adding the controller, the system flow regulation is more stable, the overshoot phenomenon is alleviated, and the reduction of the overshoot phenomenon prolongs the service life of the material and reduces the difficulty of reusing the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The engine system scheme diagram of the present invention is

[0022] Figure 2 This is a flow chart of the engine thrust control method based on the cascade PI control strategy of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0024] In this embodiment, the liquid oxygen-methane electric pump booster engine system is mainly composed of two parts: a propellant supply system and a thrust chamber. The propellant supply system is composed of a fuel tank, an oxidant tank, a motor, an inverter, a battery, a pump, a fuel valve, and a liquid oxygen valve. The thrust chamber is composed of key components such as a pintle injector, a combustion chamber, a nozzle, and a regenerative cooling channel.

[0025] like Figure 1, using methane as fuel and liquid oxygen as oxidant, 1 is the methane line, 2 is the liquid oxygen line. 3 is the fuel valve, 4 is the liquid oxygen valve. 5 and 6 form the thrust chamber, 5 is the pintle injector, 6 is the rest of the thrust chamber, including the combustion chamber, nozzle and regenerative cooling channel. 7 is the fuel tank, 8 is the oxidant tank. Other components such as motors, inverters, batteries, and pumps are also marked in the figure.

[0026] like Figure 1 In this embodiment, the battery is the power source of the motor. It stores electrical energy and converts chemical energy into electrical energy through discharge for use by the motor. The inverter is a bridge between the battery and the motor. It converts the direct current (DC) provided by the battery into the alternating current (AC) required by the motor. The motor drives the centrifugal pump for adjustment. The controller outputs a signal to control the motor speed. The change in motor speed drives the change in pump speed. In the liquid rocket engine, the centrifugal pump is responsible for extracting fuel and oxidant from tanks 7 and 8. Methane is used as fuel and liquid oxygen is used as oxidant. 1 is the methane path and 2 is the liquid oxygen path. After being pressurized by the motor pump, methane enters the cooling channel along pipeline 1. After the cooling channel goes around the thrust chamber for one week, it enters the combustion chamber through the pintle injector 5. After being pressurized by the motor pump, liquid oxygen directly enters the combustion chamber through the pintle injector 5 along pipeline 2. The two propellants enter the combustion chamber at a certain proportion and flow rate. The two propellants are mixed and ignited, which will cause a violent chemical reaction in the combustion chamber and release a large amount of heat energy. The heat energy causes the products in the combustion chamber to expand and be discharged at the tail nozzle, converting the heat energy into kinetic energy and generating thrust.

[0027] The present invention selects the thrust value as the actual control target. However, it is difficult to directly measure the thrust value, so some key factors affecting the thrust value are first found, and the thrust is adjusted by controlling these key factors. The steps for finding the influencing factors are as follows:

[0028] Step S1, the engine system solution of the present invention uses an electric pump to increase the thrust pressure, and the motor controls the speed to achieve the purpose of pump pressure increase. Therefore, the motor speed is changed by changing the input voltage. The increase in motor speed will drive the centrifugal pump to increase work, thereby increasing the propellant flow rate and achieving the purpose of thrust regulation. Therefore, the present invention selects the motor speed as the control variable.

[0029] Step S1.1: For a variable thrust liquid rocket engine, the thrust of the rocket engine can be expressed as formula (1):

[0030]

[0031] Where, F represents thrust, m . n is the propellant flow rate, A ε is the nozzle outlet cross-sectional area, P εThe static pressure of the gas on the nozzle exit cross-sectional area, P a is the external atmospheric pressure. The engine outlet velocity of the gas is given by formula (2),

[0032]

[0033] Among them, K is the isentropic index, T c is the combustion chamber temperature, P c is the combustion chamber pressure. Substituting formula 2 into formula (1) yields thrust formula (3):

[0034]

[0035] Formula (3) gives the factors affecting the thrust regulation of rocket engines, among which the propellant flow rate, combustion chamber pressure and throat nozzle area are the key factors. These parameters work together to affect the thrust regulation of rocket engines, and there is an influencing relationship between the parameters. Here, the nozzle throat area is a fixed value, and the combustion chamber pressure and propellant flow rate can be selected as the key factors for regulating the engine thrust.

[0036] In the actual operation of the engine, it is difficult to directly measure the thrust value. Therefore, the engine thrust value is obtained by measuring the engine thrust combustion chamber pressure and further calculating. The engine chamber pressure is directly measured by the pressure sensor. The combustion chamber pressure is selected as the first control target.

[0037] Step S1.2: The relationship between propellant flow rate and thrust is shown in formula (4):

[0038]

[0039] By analyzing the formula, we know that the thrust value of the rocket engine is proportional to the propellant flow rate and the combustion chamber pressure. The nozzle throat cross-sectional area is a fixed value and is not considered. Therefore, to achieve thrust regulation, it can be done by adjusting the propellant mass flow rate and the combustion chamber pressure. Because controlling the propellant mass flow rate can effectively control the mixture ratio, the propellant mixture ratio can have a great impact on the engine specific impulse. The mixture ratio can also be used as another means to adjust the thrust value. Therefore, the second control target is finally selected as the propellant mixture ratio. The expression of the propellant mixture ratio MR in the combustion chamber is (5),

[0040]

[0041] in, is the mass flow rate of liquid oxygen, is the methane mass flow rate. The mixing ratio is generally calculated by measuring the propellant flow rates of the two routes, while the propellant flow rate is calculated by measuring the pre-injection pressure, temperature and chamber pressure of the methane and liquid oxygen injectors.

[0042] The present invention ultimately chooses to adjust the engine thrust by adjusting the combustion chamber pressure and the mixture ratio.

[0043] In this embodiment, taking a liquid oxygen-methane electric pump supercharged engine as an example, a flow chart of a thrust control method based on the engine is provided as follows: Figure 2 As shown, the specific steps are as follows:

[0044] Step S2: The entire control scheme includes two major parts: liquid oxygen circuit propellant regulation and methane circuit propellant regulation.

[0045] Step S2.1, given the combustion chamber pressure and the mixing ratio setting value, calculate the required liquid oxygen circuit liquid oxygen flow reference value according to the combustion chamber pressure reference value, and obtain the actual liquid oxygen circuit liquid oxygen flow value.

[0046] Step S2.2, design a PI controller for the liquid oxygen circuit according to the given adjustment parameters. The controller receives the actual value and reference value of the liquid oxygen flow rate as input, and outputs the voltage signal of the liquid oxygen circuit electric pump after internal calculation. By adjusting the voltage signal, the speed of the liquid oxygen circuit motor can be accurately controlled, thereby achieving the purpose of adjusting the liquid oxygen flow rate until the given target value is achieved.

[0047] Step S2.3: After the liquid oxygen line is regulated, a mixing ratio signal is inputted. According to the actual value of the liquid oxygen flow rate obtained, a reference value of the methane line flow rate is calculated.

[0048] Step S2.4, design a methane circuit PI controller according to the given adjustment parameters. The controller also receives the actual value and reference value of the methane flow as input, and outputs the voltage signal of the methane circuit electric pump after internal calculation. By adjusting the voltage signal, the methane circuit motor speed is accurately controlled, thereby adjusting the methane flow.

[0049] After the above steps, precise adjustment of the combustion chamber pressure and the mixture ratio setting value is achieved, thereby achieving precise adjustment of the methane flow rate and the liquid oxygen flow rate, thereby achieving the target thrust adjustment.

[0050] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A liquid oxygen-methane electric pump booster engine system, characterized in that: The engine system mainly consists of two parts: a propellant supply system and a thrust chamber. The propellant supply system consists of a fuel tank (1), an oxidizer tank (2), a motor (3), an inverter (4), a battery (5), a pump (6), a fuel valve (7), and a liquid oxygen valve (8). The thrust chamber consists of a pintle injector (9), a combustion chamber (10), a nozzle (11), and a regenerative cooling channel (12).

2. The closed cycle hydrogen-oxygen rocket engine system according to claim 1, characterized in that: During actual operation, the controller outputs a signal to control the speed of the motor (1). The change in the speed of the motor drives the change in the speed of the pump (4). In a liquid rocket engine, the centrifugal pump is responsible for extracting fuel and oxidant from a fuel tank (11) and an oxidant tank (12). Methane is used as the fuel and liquid oxygen is used as the oxidant. The methane and liquid oxygen pipelines are used for transmission. After being pressurized by the motor pump (4), the methane enters the cooling channel (10) along the methane path. The cooling channel (10) goes around the thrust chamber once and then enters the combustion chamber (8) through the pintle injector (7). After being pressurized by the motor pump (4), the liquid oxygen directly enters the combustion chamber (8) through the pintle injector (7) along the liquid oxygen path. The two propellants enter the combustion chamber (8) at a certain ratio and flow rate. The two propellants are mixed and ignited, which causes a violent chemical reaction in the combustion chamber (8) and releases a large amount of heat energy. The heat energy causes the products in the combustion chamber (8) to expand and are discharged from the tail nozzle (9), converting the heat energy into kinetic energy to generate thrust.

3. A method for controlling thrust of a liquid oxygen-methane electric pump supercharged engine, characterized in that: The steps include: Step S1, the entire control scheme includes two major parts: liquid oxygen circuit propellant regulation and methane circuit propellant regulation. Step S1.1, given the combustion chamber pressure and the mixing ratio setting value, calculate the required liquid oxygen flow reference value of the liquid oxygen circuit according to the combustion chamber pressure reference value, and obtain the actual liquid oxygen flow value of the liquid oxygen circuit. Step S1.2, design a PI controller for the liquid oxygen circuit according to the given adjustment parameters. The controller receives the actual value and reference value of the liquid oxygen flow rate as input, and outputs the voltage signal of the liquid oxygen circuit electric pump after internal calculation. By adjusting the voltage signal, the speed of the liquid oxygen circuit motor can be accurately controlled, thereby achieving the purpose of adjusting the liquid oxygen flow rate until the given target value is achieved. Step S1.3: After the liquid oxygen line is regulated, a mixing ratio signal is inputted. According to the actual value of the liquid oxygen flow rate obtained, a reference value of the methane line flow rate is calculated. According to the given adjustment parameters, a methane line PI controller is designed. The controller also receives the actual value and reference value of the methane flow as input, and outputs the voltage signal of the methane line electric pump after internal calculation. By adjusting the voltage signal, the methane line motor speed can be accurately controlled, thereby adjusting the methane flow. After the above steps, the target thrust adjustment is achieved by accurately adjusting the combustion chamber pressure and the mixture ratio setting value.

Images