A method for adjusting the mixing ratio of a two-component propulsion system over a wide range with high precision

Abstract

A method for adjusting the mixture ratio of a two-component propulsion system over a wide range with high precision. The oxygen combustion tank adopts two independent gas supply and pressurization systems, and the two sets of gas supply and pressurization systems are exactly the same. The pressure control valve assembly is used to reduce the pressure and supply the pressurized gas to the propellant tank. The gas supply pressure reduction system adopts the "Bang-Bang" control method. Based on the pressure signal feedback of the high-precision pressure sensor on the oxidizer / fuel inlet pipeline of the orbit transfer engine, the opening and closing of the pressure control valve assembly of the gas path pressure reduction system are controlled, so that the supply pressure of the oxidizer / fuel of the system is always maintained at the set value, thereby achieving the purpose of accurately controlling the mixture ratio of the system, making the inlet pressure condition of the orbit transfer engine ignition during in-orbit flight consistent with that during ground tests, and the orbit transfer engine can always operate under the rated working conditions. Since the oxidizer / fuel tank is independently pressurized, the oxygen combustion supply pressure of the engine is independent and adjustable, and the mixture ratio can be actively controlled.

Description

Technical Field

[0001] The present invention belongs to the technical field of space propulsion, and relates to a method for adjusting the mixing ratio of a bipropellant propulsion system for a space vehicle over a large range with high precision, so as to meet the different mixing ratio requirements of various engines and satisfy the on-orbit requirements of the orbit transfer engine to operate under rated conditions. Background Art

[0002] At present, a large number of spacecrafts applied in orbit adopt bipropellant propulsion systems. The space bipropellant propulsion system has the characteristics of high specific impulse, long-term on-orbit storage, low cost, etc. A common bipropellant unified mode propulsion system using MMH / NTO as the propellant is configured with a bipropellant orbit transfer engine and multiple small-thrust bipropellant attitude control engines, and shares a set of propellant supply systems. The oxygen / fuel storage tanks share a set of pressurization systems, and the pressurization of the oxygen / fuel storage tanks and the synchronous discharge of the propellants are realized during orbit transfer. In the traditional bipropellant unified mode propulsion system, a decompression system is composed of 1 mechanical pressure reducer and 2 one-way valves. The oxidizer / fuel storage tanks share a set of pressurization systems, realizing the equal-volume discharge of the oxidizer / fuel, with low technical difficulty and good economy of the system. However, there are some deficiencies:

[0003] (1) The decompression system composed of the mechanical pressure reducer and the one-way valve is the single-point failure source of the current propulsion system. Once a failure occurs, the failure of the pressure reducer will cause the gas path to be unable to supply gas to the storage tank normally, and the failure of the one-way valve may cause the oxidizer and the fuel to come into contact in the pressurization system, resulting in danger.

[0004] (2) Since the pressure reducer is debugged on the ground, the pressure is output according to the pressure characteristics set on the ground in orbit, and the storage tank can only be pressurized passively in orbit, unable to adjust the output pressure of the gas path according to the actual situation, lacking the ability to actively control the system pressure in orbit.

[0005] (3) The flow pressure drop characteristics and mixing ratio designed by the system rely on ground tests of the system for verification and guarantee. The propulsion system has weak ability to adapt to the diversity of research and development tasks and lacks the ability to actively control the mixing ratio of the system in orbit.

[0006] (4) The orbit transfer engine may operate under conditions deviating from the rated conditions, and there is no direct on-orbit adjustment means for the inlet pressure of the orbit transfer engine, so that the orbit transfer engine often operates under conditions deviating from the rated conditions, and the design efficiency of the engine is limited.

[0007] (5) After the orbit transfer engine finishes its mission, the attitude and orbit control thrusters work on orbit for a long time. The current bipropellant unified propulsion system cannot adjust the mixing ratio in orbit and cannot meet the precise change requirements of the mixing ratio of the attitude and orbit control thrusters in orbit. Summary of the Invention

[0008] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, providing a method for adjusting the mixing ratio of a bi-propellant propulsion system for a space vehicle over a wide range with high precision to meet the different mixing ratio requirements of various engines, solving engineering practical problems such as the single-point failure source of the on-orbit mechanical pressure reduction system in the current unified bi-propellant propulsion system, the possible contact between the oxidizer and the fuel in the pressurization system leading to danger, the passive pressurization of the storage tank according to the ground-set pressure on orbit, and the variable-orbit engine may operate under conditions deviating from the rated conditions, enabling the bi-propellant propulsion system of the space vehicle to achieve intelligent features and solving the problem of wide-range and high-precision adjustment of the mixing ratio of the bi-propellant propulsion system.

[0009] The technical solution of the present invention is: a method for adjusting the mixing ratio of a bi-propellant propulsion system over a wide range with high precision, including:

[0010] Constructing independent gas supply systems for the oxidizer storage tank and the fuel storage tank respectively, and configuring a set of pressure sensor groups on the oxidizer pipeline and the fuel pipeline before the propellant inlet of the variable-orbit engine.

[0011] Using the measured values of the pressure sensor groups as feedback quantities, forming a control closed-loop for the gas supply system based on the Bang-Bang control method, adjusting the pressure of the gas supply system, and further adjusting the inlet pressure of the variable-orbit engine to make the variable-orbit engine operate at the rated pressure point.

[0012] Further, the gas supply system includes two redundant gas supply branches, and each gas supply branch includes a self-locking valve, a throttle hole, and a pressure control valve assembly connected in sequence. The self-locking valve is used to connect to the high-pressure helium gas supply source and switch the gas supply pipeline branch; the throttle hole is used to limit the high-pressure helium gas flow within a certain range, and the pressure control valve assembly is used to reduce the pressure of the high-pressure helium gas.

[0013] Further, the pressure control valve assembly includes two solenoid valves connected in series, and the response time of the solenoid valve switch is less than 10 ms.

[0014] Further, the pressure sensor group includes three pressure sensors.

[0015] Further, the measured value P of the pressure sensor group is processed by the weighted average method using three pressure values P1, P2, and P3. The processing formula is:

[0016]

[0017] Further, when the measured value P of the pressure sensor group is not within the pressure set value P S in the range before the propellant inlet of the variable-orbit engine, the closed-loop control starts; the pressure set value P SMeet P _down ≤Ps≤P _up , where P _up = P CR +△P, P _down = P CR -△P, where P CR is the rated inlet pressure of the orbit transfer engine, and △P is the inlet pressure control accuracy.

[0018] Furthermore, the rated inlet pressure P of the engine CR = 1.5MPa, the inlet pressure control accuracy △P = ±0.002MPa, and the mixture ratio control accuracy is better than ±0.4%.

[0019] Furthermore, the range of the pressure sensor is 1.3~1.75MPa, and the measurement accuracy is ±0.1%Fs.

[0020] The advantages of the present invention compared with the prior art are as follows:

[0021] (1) The oxygen-fuel propellant tank adopts an independent high-pressure helium supply method, avoiding the single-point failure of the mechanical pressure reducer and one-way valve in the traditional bipropellant unified propulsion system, and improving the reliability and safety of the bipropellant propulsion system;

[0022] (2) The pressure of the oxygen-fuel tank can be independently adjusted according to the system requirements. At the same time, the two independent gas supply systems can also adjust the system mixture ratio in real time, ensuring that the system operates at the rated mixture ratio, accurately controlling the mixture ratio, enabling the orbit transfer engine to ignite and operate at the rated mixture ratio, ensuring the consumption ratio of the oxygen-fuel propellant, reducing the difficulty of determining the filling and loading amount, and improving the utilization rate of the propellant in the tank;

[0023] (3) The delivery pressure of the orbit transfer engine is controlled by the pressure feedback of the pressure sensor installed on the oxygen-fuel pipeline at the engine inlet, enabling the inlet pressure conditions of the orbit transfer engine during on-orbit ignition to be consistent with those during ground tests, clearly knowing the on-orbit working state of the engine, and verifying the comparability with ground test data;

[0024] (4) The configuration of the oxidizer and fuel inlet pressure sensors of the orbit transfer engine enables the inlet pressure conditions of the orbit transfer engine to be known. Based on the ground test data of the orbit transfer engine, the consumption of the propellant during orbit transfer can be relatively accurately estimated;

[0025] (5) The oxygen-fuel inlet pressure of the engine can be independently and automatically adjusted. This method does not require complex analysis of the flow pressure drop in the system pipeline by humans, nor does it require using throttle orifices to control the engine mixture ratio in the liquid path system, reducing the difficulty of propulsion system design and on-orbit operation;

[0026] (6) In the middle stage of the satellite's lifespan, the propellant tank can be repressurized as needed; the independent gas supply system enables the measurement of the remaining propellant quantity using the pressure excitation method, effectively improving the prediction accuracy of the remaining propellant quantity in the tank;

[0027] (7) The high-pressure pressure control valve assembly itself provides a mechanical switch to isolate the propellant tank from the high-pressure part of the system, enhancing system safety; the high-pressure pressure control valve assembly pressurizes the tank in a bang-bang working mode, and the expected value and amplitude of the tank pressurization are autonomously controllable;

[0028] (8) After the orbit transfer engine completes its mission, the attitude and orbit control thrusters work in orbit for a long time. This method can adjust the mixture ratio in orbit to meet the precise change requirements of the mixture ratio of the attitude and orbit control thrusters in orbit, maximizing the efficiency of the attitude and orbit control thrusters. Description of the Drawings

[0029] Figure 1 Schematic diagram of the bipropellant propulsion system applied to the method of the present invention;

[0030] Figure 2 Schematic diagram of the control logic of the method of the present invention;

[0031] Figure 3 For the method of the present invention, the set value of the oxygen-fuel rated inlet pressure of a certain orbit transfer engine is P oxi = 1.510 ± 0.002 MPa, P fui = 1.515 ± 0.002 MPa, the implementation effect diagram of the inlet pressure of the orbit transfer engine;

[0032] Figure 4 For the present invention, the set value of the oxygen-fuel rated inlet pressure of a certain orbit transfer engine is P oxi = 1.510 ± 0.002 MPa, P fui = 1.515 ± 0.002 MPa, the implementation effect diagram of the mixture ratio and thrust of the orbit transfer engine;

[0033] Figure 5 For the method of the present invention, the set value of the oxygen-fuel rated inlet pressure of a certain orbit transfer engine is P oxi = 1.517 ± 0.002 MPa, P fui = 1.520 ± 0.002 MPa, the implementation effect diagram of the inlet pressure of the orbit transfer engine;

[0034] Figure 6 For the present invention, the set value of the oxygen-fuel rated inlet pressure of a certain orbit transfer engine is P oxi = 1.517 ± 0.002 MPa, P fui = 1.520 ± 0.002 MPa, the implementation effect diagram of the mixture ratio and thrust of the orbit transfer engine. Detailed implementation mode

[0035] The method of the present invention has made improvements on the traditional dual-component unified mode propulsion system. The oxidizer and fuel tanks each adopt an independent high-pressure helium supply system. The high-pressure helium decompression function is realized on the gas supply system by opening and closing the electrically driven high-pressure pressure control valve assembly; pressure measurement points are configured on the oxidizer / fuel inlet pipeline of the orbit transfer engine. Using the weighted average of these pressures as feedback, a control closed-loop is formed with the high-pressure pressure control valve assembly based on the Bang-Bang control method. The high-pressure pressure control valve assembly performs switching actions to adjust the system pressure, so that the orbit transfer engine operates under rated conditions, the mixture ratio of the propulsion system is accurately adjustable, and the system can work according to the set mixture ratio. The present invention solves the difficulties of wide-range and high-precision adjustment of the mixture ratio of the propulsion system and the operation of the orbit transfer engine under rated conditions. At the same time, the tank can be actively and independently pressurized as needed, the system has good safety, high propellant utilization efficiency, and the working state of the system is measurable and controllable.

[0036] The system of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] The principle of the dual-component propulsion system for the method of high-precision adjustment of wide-range mixture ratio applied to a space vehicle is as Figure 1 shown and consists of the following important parts:

[0038] (1) Oxygen-end helium supply module and fuel-end helium supply module: respectively used for the storage and supply of high-pressure helium; oxidizer supply module and fuel supply module: respectively used for the storage and supply of propellants.

[0039] (2) Orbit transfer engine (Engine): provides the velocity increment during the orbit transfer of the space vehicle.

[0040] (3) Gas path on-off and throttling module (oxygen path end LV5 / LV7 and O1 / O3; fuel path end LV6 / LV8 and O2 / O4): The high-pressure self-locking valves (oxygen path end LV5 / LV7; fuel path end LV6 / LV8) switch and throttle the branch of the gas supply path according to the signal instruction. The throttle orifices (O1 / O3 and O2 / O4) limit the high-pressure helium flow within a certain range so as not to be too large or too small.

[0041] (4) High-pressure pressure control valve assembly (oxygen path PCV1A / PCV1B; fuel path PCV2A / PCV2B): used to realize the decompression function of the gas path system. Each gas supply path adopts two groups of high-pressure pressure control valve assemblies in parallel for redundant backup. Each group of high-pressure pressure control valve assemblies includes two solenoid valves connected in series; the switching actions are executed according to the signal instruction, and the switching time and timing are determined by the system feedback signal.

[0042] (5) High-precision pressure acquisition module (oxygen circuit LPT7 / 9 / 11; fuel circuit LPT8 / 10 / 12): During orbit transfer, it acquires the inlet pressures of the oxygen and fuel circuits of the orbit transfer engine in real time. In terms of system status monitoring and measurement means, each group has three pressure sensors, enabling backup functionality for pressure measurement at the inlet of the orbit transfer engine.

[0043] The implementation steps and control logic are as Figure 2 shown below.

[0044] (1) Select the gas supply branch in the gas path system.

[0045] Before the space vehicle performs an orbit transfer maneuver, select the high-pressure helium gas supply branch that will be in operation. Taking the oxygen end pressure reduction system as an example: If the PCV1A helium pressure reduction branch is selected, the high-pressure self-locking valve LV5 opens and the high-pressure self-locking valve LV7 closes; if the PCV1B helium pressure reduction branch is selected, the high-pressure self-locking valve LV7 opens and the high-pressure self-locking valve LV5 closes.

[0046] (2) Set the rated inlet pressure of the orbit transfer engine.

[0047] Before the space vehicle performs an orbit transfer maneuver, set the rated inlet pressure value of the orbit transfer engine (equivalent to setting the rated mixture ratio).

[0048] The rated inlet pressure should be given based on the actual ground hot calibration test data of this engine. The set pressure value of the engine inlet pressure can ensure that the engine operates under rated conditions and ensure its mixture ratio. The set value of the engine rated inlet pressure is: P _down ≤P≤P _up , where P in =P CR ±△P, P _up =P CR +△P, P _down =P CR -△P. The typical rated inlet pressure of the engine P CR =1.5MPa; the inlet pressure control accuracy △P depends on the minimum resolution of the system pressure control. Usually, the inlet pressure accuracy △P = ±0.002MPa, and the mixture ratio adjustment accuracy is better than ±0.4%.

[0049] (3) Acquisition and processing of the inlet pressure of the orbit transfer engine propellant pipeline.

[0050] Before orbit transfer, enable the function of collecting the inlet pressure of the engine propellant pipeline during orbit transfer. During orbit transfer, high-precision pressure sensors (oxygen line LPT7 / 9 / 11; fuel line LPT8 / 10 / 12) collect the inlet pressures of the oxygen line and fuel line of the orbit transfer engine (Engine) in real time. The measurement accuracy can reach ±0.1% (within the range of 1.3 - 1.75 MPa), which is used as the feedback signal for Bang-Bang control. The three collected pressure values P1, P2, and P3 are processed according to the weighted average method to obtain the unique inlet pressure P of the orbit transfer engine propellant supply for feedback. This processing method reduces the influence on the control loop due to the zero drift fault of the pressure sensor or other abnormal pressure sensor readings. Except for the requirements of measurement accuracy and real-time collection for the three pressure quantities, there are no other requirements.

[0051] The processing formula is:

[0052]

[0053] (4) Adjust the inlet pressure of the orbit transfer engine based on the Bang-Bang control algorithm, and then adjust the mixture ratio.

[0054] During the ignition of the orbit transfer engine, active pressurization of the propellant supply is performed. By evaluating the inlet pressure value of the orbit transfer engine and comparing its value with the upper and lower limits of the set value of the control computer, the solenoid valve of the high-pressure pressure control valve assembly is commanded to switch. During the active pressurization adjustment, the basic logic is not to change the pressure set value.

[0055] If the initial inlet pressure of the orbit transfer engine is higher than the upper limit of the set pressure value, the high-pressure pressure control valve assembly remains closed until the pressure reaches the lower limit of the set value; then the valve opens again until the inlet pressure of the orbit transfer engine reaches the upper limit of the set pressure value. There is a system pressure drop working stage at the beginning of each pressurization, and the duration depends on the initial pressure of the propellant tank.

[0056] If the initial inlet pressure of the orbit transfer engine is lower than the lower limit of the set pressure value, the high-pressure pressure control valve assembly remains open until its pressure reaches the upper limit of the set value; then the valve closes again until the inlet pressure of the orbit transfer engine reaches the lower limit of the set pressure value. This cycle is repeated so that the inlet pressure of the orbit transfer engine propellant supply always meets the set value requirements.

[0057] (5) Restore the state after orbit transfer.

[0058] After the orbital transfer engine ignition is completed, the system automatically closes the selected high-pressure pressure control valve assemblies (oxygen line PCV1A or PCV1B; fuel line PCV2A or PCV2B). To ensure the safety of the storage tank and prevent over-pressurization, the gas path system needs to be closed again. The oxygen end pressure reduction system closes the high-pressure self-locking valves LV5 and LV7, and the fuel end pressure reduction system closes the high-pressure self-locking valves LV6 and LV8. At the same time, to ensure system safety and conserve resources, the function of collecting the inlet pressure of the engine propellant pipeline can be closed.

[0059] (6) Performance evaluation of the orbital transfer engine and calculation of the propellant consumption.

[0060] The flow rate, thrust, and mixture ratio of the orbital transfer engine can be evaluated using the engine inlet pressure and its rated parameters (small deviation equation), and the propellant consumption of the orbital transfer engine can be calculated in combination with the ignition time.

[0061] Embodiment

[0062] Taking the Bang-Bang control of the inlet pressure of the propellant supply of the orbital transfer engine at the oxygen line end as an example for illustration.

[0063] 1. During the control period, the inlet pressures P1, P2, and P3 of the oxidizer of the orbital transfer engine are collected in real time through the high-precision pressure sensors LP7 / 9 / 11.

[0064] 2. The inlet pressures P1, P2, and P3 of the oxidizer of the orbital transfer engine are processed by the weighted average method to obtain the inlet pressure P of the oxidizer of the orbital transfer engine for feedback.

[0065] 3. Compare the inlet pressure P of the oxidizer of the orbital transfer engine with its set value P _up and P _down : If the inlet pressure of the oxidizer is less than the lower limit of its set value P < P _down , the solenoid valve of the high-pressure pressure control valve assembly (PCV1A or PCV1B) at the oxygen line end opens, and high-pressure helium continuously enters the oxidizer storage tank, and the propulsion system operates at a constant pressure; until the inlet pressure of the oxidizer of the orbital transfer engine is greater than the upper limit of its set value P > P _up , the solenoid valve of the high-pressure pressure control valve assembly (PCV1A or PCV1B) at the oxygen line end closes, and high-pressure helium stops entering the oxidizer storage tank, and the propulsion system operates at a decreasing pressure.

[0066] 4. Repeat the above steps until the ignition of the orbital transfer engine is completed.

[0067] Repeating this cycle, the inlet pressure of the propellant supply of the orbital transfer engine is always maintained between the upper and lower limits of the set value, and the engine operates under rated conditions to achieve high-precision control of the mixture ratio.

[0068] Figure 3 andFigure 4 The effect of adjusting the inlet pressure of a certain orbit-changing engine during ignition is given. The initial conditions are: the initial pressures of the helium supply modules at the oxygen end and the combustion end are 24.0MPa and 23.8MPa; the initial filling ratio of the propellant in the oxygen-fuel tank is 75%, the initial pressure of the oxygen-fuel tank is 1.502MPa and 1.510MPa, and the ignition time of the orbit-changing engine is 3735s. The setting value of the rated inlet pressure of the orbit-changing engine oxygen-fuel is P oxi =1.510±0.002MPa, P fui =1.515±0.002MPa. Figure 3 It can be seen that during the entire orbit-changing engine ignition period, the solenoid valve of the oxygen-combustion end high-pressure pressure control valve assembly switches 128 times and 133 times respectively, and the inlet pressure of the orbit-changing engine can always be maintained at the set value. Figure 4 It can be seen that the mixture ratio of the orbit change engine is controlled within the range of ±0.4% (1.646~1.656), and the thrust of the orbit change engine is maintained within the range of 489.5N~490.4N, achieving the predetermined adjustment target.

[0069] Figure 5 and Figure 6 The effect of adjusting the inlet pressure of another orbital change engine during ignition is given. The initial conditions are: the initial pressures of the helium supply modules at the oxygen end and the combustion end are 11.5MPa and 10.9MPa; the initial filling ratio of the propellant in the oxygen-fuel tank is 36%, the initial pressures of the oxygen-fuel tank are 1.505MPa and 1.512MPa, and the ignition time of the orbital change engine is 2930s. The setting value of the rated inlet pressure of the orbital change engine oxygen-fuel is P oxi =1.517±0.002MPa, P fui =1.520±0.002MPa. Figure 5 It can be seen that during the entire orbit-changing engine ignition period, the solenoid valve of the oxygen-combustion end high-pressure pressure control valve assembly switches 27 times and 23 times respectively, and the inlet pressure of the orbit-changing engine can always be maintained at the set value. Figure 6 It can be seen that the mixture ratio of the orbit change engine is controlled within the range of ±0.4% (1.645~1.655), and the thrust of the orbit change engine is maintained at 488.7N~489.5N, achieving the predetermined adjustment target.

[0070] Figures 3 to 6 Given are the mixing ratio adjustment results for different trajectory change engines under two sets of different initial conditions. From the implementation effect, the method of the present invention can effectively adapt to the scenarios with different initial conditions and achieve the purpose of high-precision control of the mixing ratio.

[0071] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for adjusting the mixture ratio of a bi - component propulsion system, characterized in that: Comprising: Constructing respective independent gas supply systems for the oxidizer storage tank and the fuel storage tank, and respectively configuring a set of pressure sensor groups on the oxidizer pipeline and the fuel pipeline before the propellant inlet of the orbit transfer engine; Using the measured values of the pressure sensor groups as feedback quantities, forming a control closed loop for the gas supply system based on the Bang-Bang control method, adjusting the pressure of the gas supply system, and further adjusting the inlet pressure of the orbit transfer engine so that the orbit transfer engine operates at the rated pressure point; The pressure sensor group includes three pressure sensors; The measured value P of the pressure sensor group is processed by using three pressure values P1, P2 and P3 according to the weighted average method, and the processing formula is: When the measured value P of the pressure sensor group is not within the pressure set value P before the propellant inlet of the orbit transfer engine, closed-loop control starts; the pressure set value P before the propellant inlet of the orbit transfer engine S satisfies P S ≤Ps≤P _down _up , where P _up =P CR +ΔP, P _down =P CR -ΔP, where P CR is the rated inlet pressure of the orbit transfer engine, and ΔP is the inlet pressure control accuracy.​ 2. A method for adjusting the mixing ratio of a two-component propulsion system according to claim 1, characterized in that: The gas supply system includes two redundant backup gas supply branches, and each gas supply branch includes a self-locking valve, a throttle hole and a pressure control valve assembly connected in sequence, wherein the self-locking valve is used to connect with the high-pressure helium gas supply source and switch the gas supply gas path branch; the throttle hole is used to limit the high-pressure helium gas flow within a certain range, and the pressure control valve assembly is used to reduce the pressure of the high-pressure helium gas.

3. A method for adjusting the mixture ratio of a two-component propulsion system according to claim 2, characterized in that: The pressure control valve assembly includes two solenoid valves connected in series, and the solenoid valve switching response time is less than 10 ms.

4. A method for adjusting the mixing ratio of a two-component propulsion system according to claim 1, characterized in that: The rated inlet pressure P of the engine CR = 1.5 MPa, the control accuracy of the inlet pressure ΔP = ±0.002 MPa, and the control accuracy of the mixture ratio is better than ±0.4%.

5. A method for adjusting the mixture ratio of a two-component propulsion system according to claim 4, characterized in that: The measuring range of the pressure sensor is 1.3 to 1.75 MPa, and the measuring accuracy is ±0.1% Fs.

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