A liquid oxygen-methane engine and its method for multiple ignition

Abstract

The present invention relates to a liquid engine and its ignition method, specifically to a liquid oxygen-methane engine and its multi-ignition method, aiming to solve the deficiencies in the prior art that when using gunpowder for multi-ignition, it is necessary to replace the propellant column or install multiple sets of gunpowder igniters, which is not conducive to reuse, and the electric torch type ignition gas supply system is complex. A liquid oxygen-methane engine of the present invention includes a thrust chamber plasma igniter provided in the thrust chamber, a generator plasma igniter provided on the gas generator, and a power source; both the thrust chamber plasma igniter and the generator plasma igniter are provided with gas inlets for connecting to a high-pressure gas source; a multi-ignition method for a liquid oxygen-methane engine uses plasma ignition to ignite the thrust chamber and the gas generator, which can improve the combustion environment, increase the combustion speed, and play the functions of assisting combustion and maintaining the flame.

Description

Technical Field

[0001] The present invention relates to a liquid engine and its ignition method, and particularly to a liquid oxygen-methane engine and its multiple ignition method. Background Art

[0002] As the future reusable main power, liquid rocket engines have good application prospects. Liquid oxygen and liquid methane are the main oxidizer and fuel used in liquid engines. To meet the technical requirements such as reusable, state detection, and easy use and maintenance of liquid oxygen-methane liquid rocket engines (hereinafter referred to as liquid oxygen-methane engines), first of all, the liquid oxygen-methane engine must have the ability to be reused, and repeated ignition is the key to its quick reuse ability.

[0003] At present, multiple ignition of liquid oxygen-methane engines at home and abroad is mostly achieved by multiple powder ignition, electric torch ignition and other methods. When using powder for multiple ignition, it is necessary to replace the powder column or install multiple sets of powder igniters, which is not conducive to reuse; electric torch ignition can achieve multiple repeated ignition, but it requires the supply of oxidizer and fuel gas sources, and the gas supply system has a complex structure. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies in the prior art that when using powder for multiple ignition, it is necessary to replace the powder column or install multiple sets of powder igniters, which is not conducive to reuse, while electric torch ignition requires the supply of oxidizer and fuel gas sources, and the gas supply system has a complex structure, and to provide a liquid oxygen-methane engine and its multiple ignition method.

[0005] To achieve the above purpose, the technical solution provided by the present invention is as follows:

[0006] A liquid oxygen-methane engine, characterized in that: it includes a fuel pump, an oxygen pump, a turbine, a gas generator and a thrust chamber. The gas generator and the thrust chamber are both connected to the fuel pump and the oxygen pump for pumping fuel and liquid oxygen, and a fuel valve and an oxygen valve are respectively arranged on their corresponding pipelines. The turbine is coaxially connected to the fuel pump and the oxygen pump; a thrust chamber plasma igniter is arranged on the thrust chamber, and a generator plasma igniter is arranged on the gas generator. The thrust chamber plasma igniter and the generator plasma igniter are both connected to a power supply;

[0007] Both the thrust chamber plasma igniter and the generator plasma igniter are provided with gas inlets for connecting a high-pressure gas source. The high-pressure gas source is used to provide gas working medium, and a flow-limiting orifice plate is arranged at the gas inlet; the power supply provides electrical energy for the startup and maintenance of the thrust chamber plasma igniter and the generator plasma igniter, and is also used to detect the working state of the arc.

[0008] Further, the high-pressure gas source is the control purge gas source of the liquid engine.

[0009] At the same time, a multiple ignition method of the liquid oxygen-methane engine is also provided, which is special in that it includes the following steps:

[0010] S1. Turn on the thrust chamber plasma igniter to form a stable flame;

[0011] S2. Controls the flow of fuel and liquid oxygen into the thrust chamber combustion chamber, where they are ignited by the flame of the thrust chamber plasma igniter, generating high-temperature combustion gases that are ejected through the thrust chamber nozzle.

[0012] The gas inlet pressure of the thrust chamber plasma igniter is greater than or equal to the steady-state pressure of the thrust chamber combustion chamber;

[0013] S3. Turn on the plasma igniter of the generator to form a stable flame;

[0014] S4. Control the flow of fuel and liquid oxygen into the gas generator combustion chamber. The flame from the generator plasma igniter ignites them, generating high-temperature combustion gas that drives the turbine. The turbine drives the coaxially connected oxygen pump and fuel pump to rotate at high speed, pressurizing the fuel and liquid oxygen entering the thrust chamber combustion chamber and the gas generator combustion chamber. The pressure in the thrust chamber combustion chamber increases, generating high-temperature, high-pressure combustion gas that is ejected through the thrust chamber nozzle, completing a primary ignition.

[0015] The gas inlet pressure of the generator plasma igniter is greater than or equal to the steady-state pressure of the combustion chamber of the gas generator.

[0016] S5. Repeat S1-S4 and perform ignition multiple times until ignition is completed.

[0017] Furthermore, S1 is specifically:

[0018] S1.1. Control the flow of gas into the thrust chamber plasma igniter to form a stable cold air flow field between the two electrodes of the thrust chamber plasma igniter.

[0019] S1.2. Power is supplied to the two electrodes of the thrust chamber plasma igniter, and the voltage is increased to greater than 10,000 volts. The arc plasma utilizes the strong current discharge between the electrodes to ionize the cold flow of the gas working fluid, generating a plasma flame. Continuous discharge forms a stable flame at the outlet of the thrust chamber plasma igniter.

[0020] Furthermore, S3 is specifically:

[0021] S3.1. Control the gas working medium to enter the generator plasma igniter to form a stable cold air flow field between the two electrodes of the generator plasma igniter;

[0022] S3.2. Energize the two electrodes of the generator plasma igniter, raise the voltage to be greater than 10,000 volts, and use the strong current discharge between the electrodes in the arc plasma to ionize the cold flow of the gas working medium, generating a plasma flame. Continuous discharge causes a stable flame to form at the outlet of the generator plasma igniter.

[0023] Furthermore, the flow rates of the gas working medium entering the thrust chamber plasma igniter in S1.1 and the gas working medium entering the generator plasma igniter in S3.1 are obtained by calculation using the following formula:

[0024]

[0025] In the formula, q m is the flow rate of the gas working medium at the gas inlet, with the unit of kg / s; A is the flow area at the gas inlet, with the unit of mm 2 ; μ is the flow coefficient; P i is the pressure at the gas inlet, with the unit of MPa; R i is the gas constant of the gas working medium, with the unit of J / (kg·K); T i is the temperature of the gas working medium at the gas inlet, with the unit of K; k is the adiabatic index of the gas working medium.

[0026] Furthermore, the average temperatures of the flames at the outlets of the thrust chamber plasma igniter in S1.2 and the generator plasma igniter in S3.2 are both greater than twice the fuel ignition temperature.

[0027] Furthermore, the gas working medium in S1 and S3 is nitrogen.

[0028] Furthermore, the fuel is liquid methane.

[0029] Furthermore, before S1, there is also S0: Turn on the oxygen pump and the fuel pump, and respectively fill liquid oxygen and liquid methane in front of the oxygen valves and fuel valves of the gas generator and the thrust chamber. At the same time, pre-cool the pipelines for supplying liquid oxygen and liquid methane, the fuel pump, the oxygen pump, the oxygen valve, and the fuel valve.

[0030] In S5, before each repetition of S1 - S4, S0 needs to be executed.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention adds a thrust chamber plasma igniter and a generator plasma igniter in the liquid engine. As a new ignition system, the gas supply system of the gas working medium is simple and can achieve multiple ignitions.

[0033] 2. The high-pressure gas source of the present invention can use the engine control purge gas source, simplifying the supply system.

[0034] 3. In the present invention, plasma ignition is used, which has the advantages of high discharge intensity, high ionization degree, and strong chemical activity. Therefore, the ignition ability is stronger. Using a plasma igniter to continuously generate plasma in the combustion chamber can improve the combustion environment, increase the combustion speed, and play the functions of assisting combustion and maintaining the flame.

[0035] 4. In the present invention, after nitrogen is introduced to ignite the thrust chamber plasma igniter and the generator plasma igniter respectively, fuel and liquid oxygen are then introduced into the thrust chamber combustion chamber and the generator combustion chamber respectively for ignition, improving the safety of ignition.

[0036] 5. In the present invention, the gas inlet pressure of the thrust chamber plasma igniter ≥ the steady-state pressure of the thrust chamber combustion chamber, and the gas inlet pressure of the generator plasma igniter ≥ the steady-state pressure of the gas generator combustion chamber, avoiding the reverse flow of gas into the thrust chamber plasma igniter and the generator plasma igniter.

[0037] 6. In the present invention, the gas working medium flow rate is calculated through parameters such as the gas inlet pressure and the gas working medium temperature, making the gas working medium flow rate match the gas inlet pressure and the gas working medium temperature. At the same time, the plasma igniter power is matched according to the gas flow rate. Description of the Drawings

[0038] Figure 1 is a schematic structural principle diagram of an embodiment of a liquid oxygen-methane engine of the present invention;

[0039] Figure 2 is a schematic working principle diagram of the thrust chamber plasma igniter and the generator plasma igniter in the embodiment of the present invention;

[0040] Description of the Reference Numerals:

[0041] 1 - fuel pump, 2 - gas generator, 3 - thrust chamber, 4 - thrust chamber plasma igniter, 5 - oxygen pump, 6 - turbine, 7 - generator plasma igniter;

[0042] 8 - power supply, 9 - high-pressure gas source, 10 - anode, 11 - cathode. Detailed Embodiments

[0043] The following further describes the content of the present invention in detail in conjunction with the drawings and specific embodiments:

[0044] A liquid oxygen-methane engine of the present invention, as Figure 1As shown in the figure, the liquid engine includes a fuel pump 1, an oxygen pump 5, a turbine 6, a gas generator 2, and a thrust chamber 3. A thrust chamber plasma igniter 4 is provided on the thrust chamber 3, and a generator plasma igniter 7 is provided on the gas generator 2. The thrust chamber plasma igniter 4 and the generator plasma igniter 7 have the same structure and are both provided with a gas inlet for connecting to a high-pressure gas source 9. The high-pressure gas source is used to provide a gas working medium. The high-pressure gas source 9 can be set separately or directly use the control purge gas source of the liquid engine. A choke orifice plate is provided at the gas inlet. The gas generator 2 and the thrust chamber 3 are both connected to the fuel pump 1 and the oxygen pump 5 for pumping fuel and liquid oxygen, and fuel valves and oxygen valves are provided on the corresponding pipelines. The turbine 6 is coaxially connected to the fuel pump 1 and the oxygen pump 5.

[0045] A power supply 8 is connected to the thrust chamber plasma igniter 4 and the generator plasma igniter 7 to provide electrical energy for the startup and maintenance of the thrust chamber plasma igniter 4 and the generator plasma igniter 7, and to detect the working state of the arc. It is composed of a main circuit of the power supply 8, a trigger circuit, and a measurement and control circuit.

[0046] A method for multiple ignition of a liquid oxygen-methane engine includes the following steps:

[0047] S1. Open the oxygen pump 5 and the fuel pump 1, and respectively fill liquid oxygen and liquid methane in front of the oxygen valve and the fuel valve of the gas generator 2 and the thrust chamber 3. At the same time, pre-cool the pipelines for supplying liquid oxygen and liquid methane, the fuel pump 1, the oxygen pump 5, the oxygen valve, and the fuel valve.

[0048] S2. Open the thrust chamber plasma igniter 4 to form a stable flame

[0049] S2.1. Control nitrogen (N2) to enter the thrust chamber plasma igniter 4 to form a stable nitrogen cold gas flow field between the two electrodes of the thrust chamber plasma igniter 4.

[0050] S2.2. Energize the anode 10 and the cathode 11 of the thrust chamber plasma igniter 4, increase the voltage to be greater than 10,000 volts, and the arc plasma uses strong current discharge between the electrodes to ionize the nitrogen cold flow, generating a plasma flame with high temperature, high enthalpy, high ionization degree, and high chemical activity. Continuous discharge forms a stable flame at the outlet of the thrust chamber plasma igniter 4.

[0051] S3. Control the thrust chamber 3 to generate high-temperature gas

[0052] Open the oxygen valve and fuel valve of the thrust chamber 3. Liquid oxygen and liquid methane enter the combustion chamber of the thrust chamber 3 and vaporize. The initially vaporized oxygen and methane are ignited by the flame of the plasma igniter 4 of the thrust chamber. The vaporized liquid oxygen and liquid methane are continuously injected through the oxygen valve and fuel valve, forming a stable combustion zone in the combustion chamber of the thrust chamber 3, and generating high-temperature gas that is ejected through the nozzle of the thrust chamber 3 to produce thrust.

[0053] S4. Turn on the plasma igniter 7 of the generator to form a stable flame

[0054] S4.1. Control nitrogen to enter the plasma igniter 7 of the generator, forming a stable nitrogen cold gas flow field between the two electrodes of the plasma igniter 7 of the generator.

[0055] S4.2. Apply electricity to the anode 10 and cathode of the plasma igniter 7 of the generator, increase the voltage to be greater than 10,000 volts. The arc plasma uses strong current discharge between the electrodes to ionize the nitrogen cold flow, generating a plasma flame with high temperature, high enthalpy, high ionization degree, and high chemical activity. Continuous discharge forms a stable flame at the outlet of the plasma igniter 7 of the generator.

[0056] S5. Control the gas generator 2 to generate high-temperature gas to drive the turbine 6 to move, increasing the pressure in the combustion chamber of the thrust chamber 3 and the combustion chamber of the gas generator 2.

[0057] Open the oxygen valve and fuel valve of the gas generator 2. Liquid oxygen and liquid methane enter the combustion chamber of the gas generator 2 and vaporize. The initially vaporized oxygen and methane are ignited and rapidly burned under the flame of the plasma igniter 7 of the generator, igniting the large-flow liquid oxygen and liquid methane that enter the combustion chamber of the gas generator 2 and vaporize, forming a stable combustion zone. The combustion generates high-temperature gas to drive the turbine 6 to move. The turbine 6 drives the oxygen pump 5 and fuel pump 1 connected coaxially to rotate at high speed, increasing the pressure of the fuel and liquid oxygen entering the combustion chamber of the thrust chamber 3 and the combustion chamber of the gas generator 2. The thrust chamber 3 generates high-temperature and high-pressure gas that is ejected through the nozzle of the thrust chamber 3, completing one ignition.

[0058] S6. Repeat S1 - S5 for multiple ignitions until the ignition is completed.

[0059] The working principles of the plasma igniter 4 of the thrust chamber described in S2 and the plasma igniter 7 of the generator described in S4 are the same, as Figure 2 shown.

[0060] Among them, the average temperature of the generated plasma flame must be higher than the ignition point of methane. In the present invention, it is preferably that the average temperatures of the flames at the outlets of the plasma igniter 4 of the thrust chamber described in S2 and the plasma igniter 7 of the generator described in S5 are both greater than twice the ignition point temperature of methane.

[0061] The powers of the generator plasma igniter 7 and the thrust chamber plasma igniter 4 need to match the gas working medium flow rate. The gas working medium flow rate is related to parameters such as the gas inlet pressure, the equivalent flow area of the gas inlet, and the gas working medium temperature. A larger gas working medium flow rate is beneficial to the diffusion of the plasma flame, but it will reduce the plasma flame temperature. Therefore, the flow rates of the gas working medium entering the thrust chamber plasma igniter 4 as described in S1.1 and the gas working medium entering the generator plasma igniter 7 as described in S3.1 are obtained by the following formula:

[0062]

[0063] In the formula, q m is the gas working medium flow rate at the gas inlet, with the unit of kg / s; A is the flow area at the gas inlet, with the unit of mm 2 ; μ is the flow coefficient, and its value range is 0.7 - 0.95. It is related to the ratio of the pipeline diameter at the gas inlet and the orifice diameter of the flow restrictor plate. When this ratio is larger, the value of the flow coefficient is also larger; when the ratio is smaller, the flow coefficient is adjusted accordingly to be smaller; μA is the equivalent flow area at the gas inlet; P i is the pressure at the gas inlet, with the unit of MPa; R i is the gas constant of the gas working medium, with the unit of J / (kg·K); T i is the gas working medium temperature at the gas inlet, with the unit of K; k is the adiabatic index of the gas working medium.

[0064] In this embodiment, nitrogen is used as the gas working medium. The high-pressure gas source 9 providing nitrogen can be the control purge gas source originally equipped in the engine, without the need to set up other gas sources additionally; in other embodiments of the present invention, oxygen can also be selected as the gas working medium.

[0065] In this embodiment, the fuel is liquid methane. In other embodiments of the present invention, other liquid fuels can also be used, and only the plasma flame temperature needs to be adjusted to be greater than twice the ignition point of other liquid fuels.

[0066] Among them, in order to prevent the gas from flowing back into the thrust chamber plasma igniter 4 or the generator plasma igniter 7 during the pressure increase process in the combustion chamber of the thrust chamber 3 or the generator combustion chamber, resulting in the ignition interruption of the thrust chamber plasma igniter 4 or the generator plasma igniter 7, therefore, the gas inlet pressure of the thrust chamber plasma igniter 4 ≥ the steady-state pressure of the combustion chamber of the thrust chamber 3, and the gas inlet pressure of the generator plasma igniter 7 ≥ the steady-state pressure of the combustion chamber of the gas generator 2.

Claims

1. A method for multiple ignition of a liquid oxygen-methane engine, characterized in that, The liquid oxygen-methane engine includes a fuel pump (1), an oxygen pump (5), a turbine (6), a gas generator (2), and a thrust chamber (3). The gas generator (2) and the thrust chamber (3) are both connected to the fuel pump (1) and the oxygen pump (5) for pumping fuel and liquid oxygen, and a fuel valve and an oxygen valve are respectively arranged on the corresponding pipelines. The turbine (6) is coaxially connected to the fuel pump (1) and the oxygen pump (5); A thrust chamber plasma igniter (4) is arranged on the thrust chamber (3), and a generator plasma igniter (7) is arranged on the gas generator (2). Both the thrust chamber plasma igniter (4) and the generator plasma igniter (7) are connected to a power supply (8); Both the thrust chamber plasma igniter (4) and the generator plasma igniter (7) are provided with gas inlets for connecting to a high-pressure gas source (9). The high-pressure gas source is used to provide gas working medium, and a choke orifice plate is arranged at the gas inlet; The power supply (8) provides electrical energy for the startup and maintenance of the thrust chamber plasma igniter (4) and the generator plasma igniter (7), and is used to detect the working state of the arc; The multiple ignition method includes the following steps: S1. Turn on the thrust chamber plasma igniter (4) to form a stable flame; S2. Control the fuel and liquid oxygen to enter the combustion chamber of the thrust chamber (3), and ignite them through the flame of the thrust chamber plasma igniter (4) to generate high-temperature gas, which is ejected through the nozzle of the thrust chamber (3); The gas inlet pressure of the thrust chamber plasma igniter (4) ≥ the steady-state pressure of the combustion chamber of the thrust chamber (3); S3. Turn on the generator plasma igniter (7) to form a stable flame; S4. Control the fuel and liquid oxygen to enter the combustion chamber of the gas generator (2), and ignite them through the flame of the generator plasma igniter (7) to generate high-temperature gas to drive the turbine (6) to move. The turbine (6) drives the coaxially connected oxygen pump (5) and fuel pump (1) to rotate at high speed, pressurize the fuel and liquid oxygen entering the combustion chambers of the thrust chamber (3) and the gas generator (2). The pressure of the combustion chamber of the thrust chamber (3) increases, and high-temperature and high-pressure gas is ejected through the nozzle of the thrust chamber (3) to complete one ignition; The gas inlet pressure of the generator plasma igniter (7) ≥ the steady-state pressure of the combustion chamber of the gas generator (2); S5. Repeat S1-S4 for multiple ignitions until the ignition is completed.

2. The multiple ignition method of a liquid oxygen-methane engine according to claim 1, wherein: S1 is specifically: S1.

1. Control the gas working medium to enter the thrust chamber plasma igniter (4) to form a stable cold gas flow field between the two electrodes of the thrust chamber plasma igniter (4); S1.

2. Energize the two electrodes of the thrust chamber plasma igniter (4), increase the voltage to be greater than 10,000 volts, and the arc plasma uses strong current discharge between the electrodes to ionize the cold gas flow of the gas working medium to generate plasma flame. Continuous discharge makes a stable flame form at the outlet of the thrust chamber plasma igniter (4).

3. The multiple ignition method of a liquid oxygen-methane engine according to claim 2, wherein: Specifically, S3 is as follows: S3.

1. Control the gas working medium to enter the generator plasma igniter (7) to form a stable cold gas flow field between the two electrodes of the generator plasma igniter (7); S3.

2. Energize the two electrodes of the generator plasma igniter (7), increase the voltage to be greater than 10,000 volts, and use the strong current discharge between the electrodes of the arc plasma to ionize the cold gas flow of the gas working medium to generate a plasma flame. Continuous discharge forms a stable flame at the outlet of the generator plasma igniter (7).

4. A method for multiple ignition of a liquid oxygen-methane engine according to claim 3, characterized in that: The flow rate of the gas working medium entering the thrust chamber plasma igniter (4) in S1.1 and the flow rate of the gas working medium entering the generator plasma igniter (7) in S3.1 are obtained by the following formula: where q m is the gas working medium flow rate at the gas inlet, with the unit of kg / s; A is the flow area at the gas inlet, with the unit of mm 2 ; μ is the flow coefficient; P i is the pressure at the gas inlet, with the unit of MPa; R i is the gas constant of the gas working medium, with the unit of J / (kg·K); T i is the gas working medium temperature at the gas inlet, with the unit of K; k is the adiabatic index of the gas working medium.

5. A method for multiple ignition of a liquid oxygen-methane engine according to claim 4, characterized in that: The average temperatures of the flames at the outlets of the thrust chamber plasma igniter (4) in S1.2 and the generator plasma igniter (7) in S3.2 are both greater than twice the fuel ignition temperature.

6. A method for multiple ignition of a liquid oxygen-methane engine according to any one of claims 1-5, characterized in that: In S1 and S3, the gas working medium is nitrogen.

7. A method for multiple ignition of a liquid oxygen-methane engine according to claim 6, characterized in that: In S2 and S4, the fuel is liquid methane.

8. A method for multiple ignition of a liquid oxygen-methane engine according to claim 7, characterized in that: Before S1, S0 is further included: Open the oxygen pump (5) and the fuel pump (1), respectively fill liquid oxygen and liquid methane in front of the oxygen valve and the fuel valve of the gas generator (2) and the thrust chamber (3). At the same time, pre-cool the pipelines for supplying liquid oxygen and liquid methane, the fuel pump (1), the oxygen pump (5), the oxygen valve and the fuel valve; In S5, before each repetition of S1-S4, S0 needs to be executed.

9. A method for multiple ignition of a liquid oxygen-methane engine according to claim 1, characterized in that: The high-pressure gas source (9) is the control purge gas source of the liquid engine.

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