Thrust and mixing ratio control method for gas generator circulating liquid oxygen methane engine

Abstract

The invention provides a thrust and mixing ratio control method for a gas generator circulating liquid oxygen methane engine, which comprises the following steps of: determining the control quantity of the thrust and the mixing ratio of the engine according to the system scheme of the gas generator circulating liquid oxygen methane engine; formulating an interpolation table of thrust and mixing ratio of the control quantity and the controlled quantity based on test run data; thrust and mixing ratio control instructions are determined according to flight requirements, interpolation is carried out in the obtained interpolation table, the control quantity is adjusted, and variable thrust control and stable mixing ratio control are achieved. According to the method, an interpolation table of thrust under different gear mixing ratios and the opening degrees of the four adjusting valves is formulated based on the test run data, manual decoupling is achieved, and the defect that in the prior art, thrust and the mixing ratios influence each other during control is overcome; continuous large-range variable thrust control of the engine is achieved, and the mixing ratio of the engine is adjusted according to requirements.

Description

Technical Field

[0001] The invention relates to liquid rocket engine technology, and in particular to a control system of a gas generator cycle liquid oxygen-methane engine. Background Art

[0002] Liquid oxygen-methane engines have become an important development direction for reusable rocket propulsion due to their low cost, high performance and easy maintenance. Among them, the engine's continuously variable thrust regulation and stable mixture ratio control are key links in realizing the vertical recovery technology of launch vehicles.

[0003] A lot of research has been carried out abroad on liquid oxygen-methane engines. The Raptor liquid oxygen-methane engine in the United States adopts a full-flow regenerative combustion cycle, and the thrust can be adjusted within the range of 40%-100%; the BE-4 engine adopts an oxygen-rich staged combustion cycle, and the thrust can be adjusted within the range of 40%-100%; Russia has also successively carried out research on liquid oxygen-methane engines with different thrusts, covering thrusts of 10N-2000kN; at the same time, European countries have also carried out a lot of liquid oxygen-methane engine program demonstration work under the guidance of the "Future Space Vehicle Pre-Development Plan". China has carried out preliminary research on liquid oxygen-methane engines since the 1980s, and has accumulated certain experience so far. However, due to the strong coupling between the thrust and the mixture ratio of liquid oxygen-methane engines, adjusting a single variable will cause fluctuations in another variable, making it impossible to guarantee the control accuracy of the thrust and mixture ratio of liquid oxygen-methane engines. Summary of the invention

[0004] The technical problem solved by the present invention is: a method for controlling the thrust and mixture ratio of a gas generator cycle liquid oxygen-methane engine is proposed, aiming to achieve precise control of the variable thrust and mixture ratio of the gas generator cycle liquid oxygen-methane engine through artificial decoupling.

[0005] The technical solution of the present invention is: a method for controlling thrust and mixing ratio of a gas generator cycle liquid oxygen-methane engine, comprising:

[0006] Determine the control amount of engine thrust and mixture ratio according to the gas generator cycle liquid oxygen-methane engine system scheme;

[0007] Formulate interpolation tables of control and controlled thrust and mixture ratio based on test data;

[0008] The thrust and mixture ratio control instructions are determined according to the flight requirements, and interpolation is performed in the obtained interpolation table to adjust the control quantity to achieve variable thrust control and stable mixture ratio control.

[0009] Preferably, the adjustable valve opening in the engine system is used as a control variable for the engine thrust and the mixture ratio; wherein the adjustable valves include a thrust chamber oxygen valve, a thrust chamber methane valve, a generator oxygen valve and a generator methane valve, the generator oxygen valve opening is adjusted to control the thrust of the liquid oxygen-methane engine, the generator methane valve and the generator oxygen valve are coordinated and adjusted to maintain the generator mixture ratio, and the thrust chamber oxygen valve and the thrust chamber methane valve are coordinated and adjusted to control the mixture ratio of the liquid oxygen-methane engine.

[0010] Preferably, the interpolation table is determined in the following manner:

[0011] Determine the control target, that is, the thrust is adjustable from 50% to 100% in any working condition, and the mixing ratio is adjustable in three levels: -5%, 0%, and 5%;

[0012] The following processing is performed for the 0 level, -5% level and 5% level respectively:

[0013] First, an engine calibration test is carried out at a thrust level of 100% and a current gear mixture ratio to obtain the engine characteristics under this working condition; then, the engine simulation model is modified to make its engine characteristics under this working condition consistent with the real engine characteristics; based on the modified engine simulation model, the valve openings at the remaining thrust levels at the current gear mixture ratio, i.e., every 10% thrust level, are obtained through simulation, and the valve openings are used as a reference value to carry out calibration tests at the remaining thrust levels at the current gear mixture ratio to obtain the engine characteristics at different valve openings; similarly, the engine simulation model is modified to make its characteristics consistent with the real characteristics at the same valve opening; thus, the engine characteristics correction of a wide range of thrust levels at the current gear mixture ratio of the engine simulation model is completed;

[0014] Using the revised engine simulation model, the openings of the four regulating valves corresponding to different thrusts under the current gear mixing ratio are obtained, and an interpolation table of the control quantity and the controlled quantity is formulated;

[0015] The control quantity is the opening of four adjustable valves, and the controlled quantity is the thrust and the mixing ratio.

[0016] Preferably, there are three interpolation tables, which respectively represent the openings of four adjustable valves corresponding to different thrusts under three mixing ratios.

[0017] Preferably, the mixing ratio is -5%, corresponding to 95% of the rated mixing ratio;

[0018] Mixing ratio 0 corresponds to the rated mixing ratio;

[0019] The mixing ratio of 5% corresponds to 105% of the rated mixing ratio.

[0020] Preferably, determining the thrust and mixture ratio control instructions according to the flight requirements specifically includes:

[0021] Determine the mixture ratio control command, i.e., the mixture ratio gear, according to the tank liquid level data; determine the thrust control command in real time according to the trajectory data and thrust condition requirements during flight;

[0022] During engine operation, the openings of the four regulating valves are determined from the interpolation table according to the mixture ratio gear and thrust control instructions. The thrust of the liquid oxygen-methane engine is controlled by adjusting the opening of the generator oxygen valve. The mixture ratio of the liquid oxygen-methane engine is controlled by controlling the thrust chamber oxygen valve and the thrust chamber methane valve to be coordinated and adjusted. The generator mixture ratio is controlled to be constant by cooperatively adjusting the generator methane valve opening and the generator oxygen valve opening.

[0023] Preferably, the interpolation adopts linear interpolation.

[0024] Preferably, the mixing ratio is determined as needed in the following manner: the tank liquid level data is tracked in real time, and if the content of the methane tank is lower than the current standard line, the mixing ratio control command is adjusted to -5% to increase the amount of methane entering the engine so that the actual mixing ratio of the engine is still maintained at the rated value; if the content of the oxygen tank is lower than the current standard line, the mixing ratio control command is adjusted to 5% to increase the amount of oxygen entering the engine so that the actual mixing ratio of the engine is maintained at the rated value.

[0025] The beneficial effects of the present invention compared with the prior art are:

[0026] The thrust and mixing ratio control method of a gas generator cycle liquid oxygen-methane engine provided by the present invention has the following technical effects compared with the prior art by adopting the above technical solution:

[0027] (1) In the present invention, an interpolation table of thrust and opening of four regulating valves under different gear mixture ratios is formulated based on test data and engine simulation, so as to realize artificial decoupling and make up for the deficiency of the prior art in that thrust and mixture ratio affect each other when controlling thrust and mixture ratio; realize continuous large-range variable thrust control of the engine and adjust the engine mixture ratio according to the actual operation requirements of the engine; at the same time, in the process of obtaining the interpolation table, engine simulation is used to reduce the number of test runs and reduce the development cost.

[0028] (2) During the operation of the engine, the thrust and the mixture ratio are precisely controlled by real-time interpolation of the interpolation table formulated by the present invention. The control system is simple and easy to implement, and has engineering application value;

[0029] (3) The present invention realizes variable thrust control of the gas generator cycle liquid oxygen-methane engine by adjusting the opening of the generator oxygen valve, and realizes engine mixture ratio control by coordinated adjustment of the thrust chamber oxygen valve opening and the thrust chamber methane valve opening;

[0030] (4) The present invention controls the generator mixing ratio to be constant by synergistically adjusting the generator methane valve opening and the generator oxygen valve opening, thereby preventing the generator mixing ratio from being too high to cause safety hazards and the mixing ratio from being too low to reduce combustion efficiency, thereby ensuring the safety and high performance of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the schematic diagram of the thrust and mixture ratio open-loop control method. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the embodiments.

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It is also necessary to explain that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0034] In order to accurately control the thrust and mixing ratio of a gas generator cycle liquid oxygen-methane engine, the present invention proposes a thrust and mixing ratio control method for a gas generator cycle liquid oxygen-methane engine. The thrust and mixing ratio of the liquid oxygen-methane engine are strongly coupled, and the control difficulty is high. The control system proposed by the present invention has a simple structure and is easy to implement. By formulating an interpolation table and manually decoupling, the purpose of accurately controlling the thrust and mixing ratio can be achieved.

[0035] The specific implementation of the present invention takes a certain type of gas generator cycle liquid oxygen-methane engine as an example, and the thrust and mixing ratio control method of the generator cycle liquid oxygen-methane engine includes the following steps:

[0036] Step 1: Design the generator cycle liquid oxygen-methane engine system scheme and determine the control quantities of the engine thrust and mixture ratio control systems;

[0037] Step 1-1: Design a gas generator cycle liquid oxygen-methane engine system scheme, wherein the adjustable valves include a thrust chamber oxygen valve, a thrust chamber methane valve, a generator oxygen valve, and a generator methane valve;

[0038] Step 1-2: The four adjustable valve openings in step 1-1 are used as control quantities of the engine thrust and mixture ratio control system, wherein the generator oxygen valve opening is adjusted to control the thrust of the liquid oxygen-methane engine, the generator methane valve and the generator oxygen valve are coordinated to maintain the generator mixture ratio to ensure the safety and performance of the engine operation, and the thrust chamber oxygen valve and the thrust chamber methane valve are coordinated to control the mixture ratio of the liquid oxygen-methane engine.

[0039] Step 2: Obtain an interpolation table of the control variable, the controlled variable thrust and the mixture ratio based on the test data;

[0040] Step 2-1: Determine the control target of the control system, that is, the thrust is adjustable from 50% to 100% in any working condition, and the mixing ratio is adjustable in three gears: -5%, 0%, and 5%;

[0041] Mixing ratio level 0 corresponds to the rated mixing ratio, specifically the ratio of oxygen to methane is 3;

[0042] The mixing ratio is -5%, corresponding to 95% of the rated mixing ratio;

[0043] The mixing ratio is 5%, corresponding to the rated mixing ratio of 105%.

[0044] Step 2-2: First, an engine calibration test is performed at 100% thrust level and rated mixture ratio, i.e., 0 gear, to obtain the engine characteristics under this working condition; then, the engine simulation model is modified so that the engine characteristics under this working condition are consistent with the real engine characteristics; based on the modified engine simulation model, the valve openings of the remaining thrust levels (every 10% thrust level) at 0 gear can be obtained through simulation, and the valve opening is used as a reference value to perform calibration tests at the remaining thrust levels at 0 gear, so that the engine characteristics under different valve openings can be obtained; similarly, the engine simulation model is modified so that its characteristics are consistent with the real characteristics under the same valve opening; thus, the engine characteristics correction of a wide range of thrust levels at the rated mixture ratio of the engine simulation model is completed;

[0045] Step 2-3: Repeat the above steps at -5% and 5% mixing ratio positions;

[0046] Step 2-4: Using the modified engine simulation model, within the controlled quantity adjustment range described in step 2-1, obtain the four regulating valve angles corresponding to different thrusts and mixture ratios, and formulate an interpolation table of the controlled quantity and the controlled quantity. Specifically, formulate a corresponding interpolation table according to the three adjustment gears of the mixture ratio to achieve the purpose of artificial decoupling. The present invention has 3 interpolation tables, which are the openings of the four adjustable valves corresponding to different thrusts under the three-gear mixture ratio. Taking the -5% opening as an example, the interpolation table is shown in Table 1.

[0047] Table 1 -0.5% mixing ratio interpolation table

[0048]

[0049]

[0050] Step 3: Determine the thrust and mixture ratio control instructions according to the flight requirements, and interpolate in the interpolation table obtained in step 2 to adjust the control quantity to achieve variable thrust control and stable mixture ratio control.

[0051] Step 3-1: The steps for implementing the thrust and mixture ratio open-loop control of the gas generator cycle liquid oxygen-methane engine are as follows: Figure 1 As shown, the mixture ratio control command is determined according to the tank liquid level data, and the thrust control command is determined according to the trajectory data and thrust condition requirements.

[0052] The purpose of engine control is to maintain the mixture ratio at the rated value, i.e., 0 gear. However, due to factors such as tank leakage, if the control is still carried out according to the 0 gear mixture ratio requirement, the actual mixture ratio cannot be maintained at the rated value, thus affecting the engine performance. Therefore, the tank level data is tracked in real time. If the content of the methane tank is lower than the current standard line, it means that the tank may leak and the methane entering the engine is reduced. At this time, the mixture ratio control command is adjusted to -5% gear to increase the amount of methane entering the engine so that the actual mixture ratio of the engine is still maintained at the rated value; if the content of the oxygen tank is low, the mixture ratio control command is adjusted to 5% gear to increase the amount of oxygen entering the engine so that the actual mixture ratio of the engine is maintained at the rated value. During the operation of the engine, the mixture ratio gear command should be adjusted as needed according to the changes in engine performance caused by the problem.

[0053] The thrust control command is obtained by the rocket as a whole based on the ballistic data and given to the engine.

[0054] Step 3-2: During the operation of the engine, real-time interpolation is performed based on the interpolation table prepared in step 2-2 to obtain the four regulating valve angles, i.e., openings, corresponding to the current thrust and mixture ratio instructions;

[0055] Step 3-3: Adjust the angles of the four control valves according to the interpolation results of step 3-2 to achieve variable thrust control and open-loop precise control of the mixture ratio.

[0056] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

[0057] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for controlling thrust and mixing ratio of a gas generator cycle liquid oxygen-methane engine, characterized in that include: Determine the control amount of engine thrust and mixture ratio according to the gas generator cycle liquid oxygen-methane engine system scheme; Formulate interpolation tables of control and controlled thrust and mixture ratio based on test data; The thrust and mixture ratio control instructions are determined according to the flight requirements, and interpolation is performed in the obtained interpolation table to adjust the control quantity to achieve variable thrust control and stable mixture ratio control.

2. The method according to claim 1, characterized in that: The adjustable valve opening in the engine system is used as the control variable of the engine thrust and the mixture ratio; wherein the adjustable valves include a thrust chamber oxygen valve, a thrust chamber methane valve, a generator oxygen valve and a generator methane valve; the generator oxygen valve opening is adjusted to control the thrust of the liquid oxygen-methane engine; the generator methane valve and the generator oxygen valve are coordinated to maintain the generator mixture ratio; the thrust chamber oxygen valve and the thrust chamber methane valve are coordinated to control the mixture ratio of the liquid oxygen-methane engine.

3. The method according to claim 2, characterized in that: The interpolation table is determined in the following manner: Determine the control target, that is, the thrust is adjustable from 50% to 100% in any working condition, and the mixing ratio is adjustable in three levels: -5%, 0%, and 5%; The following processing is performed for the 0 level, -5% level and 5% level respectively: First, an engine calibration test is carried out at a thrust level of 100% and a current gear mixture ratio to obtain the engine characteristics under this working condition; then, the engine simulation model is modified to make the engine characteristics under this working condition consistent with the real engine characteristics; based on the modified engine simulation model, the valve openings at the remaining thrust levels at the current gear mixture ratio, i.e., every 10% thrust level, are obtained through simulation, and the valve openings are used as a reference value to carry out calibration tests at the remaining thrust levels at the current gear mixture ratio to obtain the engine characteristics under different valve openings; similarly, the engine simulation model is modified to make its characteristics consistent with the real characteristics under the same valve opening; At this point, the engine characteristics correction of a wide range of thrust levels under the current gear mixture ratio of the engine simulation model is completed; Using the revised engine simulation model, the openings of the four regulating valves corresponding to different thrusts under the current gear mixing ratio are obtained, and an interpolation table of the control quantity and the controlled quantity is formulated; The control quantity is the opening of four adjustable valves, and the controlled quantity is the thrust and the mixing ratio.

4. The method according to claim 3, characterized in that: There are three interpolation tables, which respectively represent the openings of four adjustable valves corresponding to different thrusts under three mixing ratios.

5. The method according to claim 3, characterized in that: The mixing ratio is -5%, corresponding to 95% of the rated mixing ratio; Mixing ratio 0 corresponds to the rated mixing ratio; The mixing ratio of 5% corresponds to 105% of the rated mixing ratio.

6. The method according to claim 4, characterized in that: Determine thrust and mixture ratio control instructions based on flight requirements, including: Determine the mixture ratio control command, i.e., the mixture ratio gear, according to the tank liquid level data; determine the thrust control command in real time according to the trajectory data and thrust condition requirements during flight; During engine operation, the openings of the four regulating valves are determined from the interpolation table according to the mixture ratio gear and thrust control instructions. The thrust of the liquid oxygen-methane engine is controlled by adjusting the opening of the generator oxygen valve. The mixture ratio of the liquid oxygen-methane engine is controlled by controlling the thrust chamber oxygen valve and the thrust chamber methane valve to be coordinated and adjusted. The generator mixture ratio is controlled to be constant by cooperatively adjusting the generator methane valve opening and the generator oxygen valve opening.

7. The method according to claim 1 or 6, characterized in that: The interpolation is performed by linear interpolation.

8. The method according to claim 6, characterized in that: The mixing ratio is determined on demand by: real-time tracking of tank level data, if the volume of the methane tank is lower than the current standard line, the mixing ratio control command is adjusted to -5% to increase the amount of methane entering the engine so that the actual mixing ratio of the engine is still maintained at the rated value; If the volume in the oxygen tank is lower than the current standard line, the mixture ratio control command will be adjusted to 5% to increase the amount of oxygen entering the engine so that the actual mixture ratio of the engine is maintained at the rated value.

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