Cleaning method for space orbit control engine after hot standard test run

Abstract

The invention provides a cleaning method for a space orbit control engine after hot standard test run. Comprising the following steps: S1, carrying out thermal calibration test run; s2, residual propellant is blown away; s3, cleaning with a cleaning solution; s4, cleaning liquid is blown away; s5, the throat part is blocked through a sealing tool; s6, soaking, cleaning and blowing off the fuel path; s7, oxidizing agent path soaking, cleaning and blow-off are conducted; s8, deionized water cleaning treatment is carried out; s9, nitrogen blowing is carried out; and S10, vacuum drying is carried out. The sealing tool is additionally arranged on the throat portion, the combustion chamber is soaked for a long time, and the problems that residues on the inner wall of the combustion chamber are stubborn and not easy to clean, and the top area is difficult to comprehensively clean during transverse installation are solved; the method comprises the following steps: washing with deionized water after cleaning with a cleaning solution, sampling the deionized water before and after washing, carrying out pH analysis and control, and adopting a normal-temperature nitrogen and hot nitrogen blow-off strategy to solve the problems of cleaning solution residue and cleaning quality quantitative control.

Description

Technical Field

[0001] The present invention relates to the technical field of spacecraft propulsion, and in particular, to a cleaning method for a space orbit control engine after hot calibration test runs. Background Art

[0002] Space orbit control engines are used to provide power for spacecraft orbital maneuvers. Their working performance is crucial for the in-orbit working life and use safety of spacecraft. Especially for high-performance space orbit control engines, the working temperature of the engine combustion chamber is greatly affected by the deviation of the mass flow ratio of oxidizer to fuel, that is, the mixing ratio. The working temperature of the combustion chamber directly affects the working life. At present, the working performance of the engine is usually calibrated by means of hot calibration test runs for space orbit control engines, and the calibrated products continue to participate in flight use. In this process, the cleaning of residual propellants and the detection after cleaning are particularly critical for the reuse of orbit control engine products.

[0003] Chinese Patent with publication number CN102513312B discloses a solenoid valve cleaning method after hot calibration of a bi-propellant thruster, and Chinese Patent with publication number CN103406312A discloses a thrust chamber cleaning method after hot calibration of a bi-propellant thruster. The above documents are applicable to the cleaning after hot calibration of small-thrust attitude control engines, but the cleaning effect on large-thrust space orbit control engines is average. The main reason is that the mass flow rate of the propellants participating in combustion in large-thrust space orbit control engines is large, the heat flux density in the combustion chamber increases significantly, and the continuous ignition working time is long. The combustion chamber is in a high-temperature and high-pressure state for a long time, resulting in a denser combination of residues and the wall surface. The conventional method of pulsed flushing has a poor cleaning effect on it, and the large-thrust engine is horizontally fixedly installed during test runs, and the combustion chamber diameter is large, and it is difficult to cover the top area of the combustion chamber during cleaning. The present invention provides a cleaning method for a space orbit control engine after hot calibration test runs, which solves the problems of stubborn combustion residues of large-thrust engines and comprehensive coverage of the cleaning area. Therefore, the methods described in these documents and the method of the present invention belong to different inventive concepts. Summary of the Invention

[0004] Aiming at the defects in the prior art, the purpose of the present invention is to provide a cleaning method for a space orbit control engine after hot calibration test runs.

[0005] According to the cleaning method for a space orbit control engine after hot calibration test runs provided by the present invention, it includes:

[0006] Step S1: Conduct a hot calibration test run on the engine on the test stand to obtain vacuum thrust, mixing ratio, lateral thrust, specific impulse performance, and working temperature parameters;

[0007] Step S2: After the hot calibration test run, conduct nitrogen purging on the residual propellant on the test stand. First, purge the fuel line, then the oxidizer line, then alternate purging of the two lines, and finally close the fuel control valve and the oxidizer control valve after the last purging;

[0008] Step S3: Let the fuel cleaning liquid enter the fuel control valve and the oxidizer cleaning liquid enter the oxidizer control valve. After cleaning, the oxidizer cleaning liquid and the fuel cleaning liquid are discharged through the engine outlet;

[0009] Step S4: Conduct alternate nitrogen purging on the fuel line and the oxidizer line, and finally purge the two lines simultaneously. After purging, close the fuel control valve and the oxidizer control valve;

[0010] Step S5: Use a sealing tooling to block the throat of the thrust chamber, move the fixed bracket to apply a certain pressure to form a seal with the throat of the thrust chamber prepared with a high-temperature oxidation-resistant coating on the surface;

[0011] Step S6: Open the fuel control valve, fill the fuel cleaning liquid into the throat of the thrust chamber, then close the downstream cut-off valve of the throat. After staying for a preset time, open the downstream cut-off valve of the throat for flushing, and maintain the propellant control valve at the preset pre-valve pressure until the fuel cleaning liquid is consumed. After cleaning, conduct nitrogen purging, and the fuel control valve is in the closed state after purging;

[0012] Step S7: Open the oxidizer control valve, fill the oxidizer cleaning liquid into the throat of the thrust chamber, then close the downstream cut-off valve of the throat. After staying for a preset time, open the downstream cut-off valve of the throat for flushing, and maintain the propellant control valve at the preset pre-valve pressure until the oxidizer cleaning liquid is consumed. After cleaning, conduct nitrogen purging, then alternate purging of the oxidizer line and the fuel line, and finally purge the two lines simultaneously. After purging, close the fuel control valve and the oxidizer control valve;

[0013] Step S8: Open the engine fuel control valve and the oxidizer control valve, fill deionized water into the throat of the thrust chamber, then close the downstream cut-off valve of the throat. After staying for a preset time, open the downstream cut-off valve of the throat for flushing, and maintain the fuel control valve and the oxidizer control valve at the preset pre-valve pressure. During the cleaning process, take samples of the cleaned deionized water from the engine outlet, and then conduct pH analysis on each sample until the pH difference between the deionized water flowing into and out of the engine is less than the preset value and then stop the deionized water rinsing;

[0014] Step S9: First, conduct nitrogen purging at room temperature, alternate purging of the fuel line and the oxidizer line, and finally purge the two lines simultaneously. After purging, close the fuel control valve and the oxidizer control valve, and then conduct nitrogen purging with hot nitrogen, alternate purging of the fuel line and the oxidizer line, and finally purge the two lines simultaneously. After purging, close the fuel control valve and the oxidizer control valve;

[0015] Step S10: Remove the engine from the test stand and perform vacuum drying.

[0016] Furthermore, in step S1, control the temperature of the oxidizer dinitrogen tetroxide to be 20 ± 2°C, the temperature of the fuel methylhydrazine to be 20 ± 2°C. Before the engine starts, the pressure in the high-altitude chamber is less than 150 Pa, and during operation, the pressure in the high-altitude chamber is less than 100 Pa. When the engine is working, the inlet pressure of the two-way propellant control valve is 1.5 MPa.

[0017] Furthermore, the nitrogen pressure for nitrogen purging is 0.5 MPa.

[0018] Furthermore, in step S3, after the oxidizer cleaning liquid enters the oxidizer control valve and stays for 20 min, open the fuel control valve for flushing. Keep the pressure in front of the propellant control valve at 0.2 MPa, and the flushing time is 120 s. During the flushing process, the valve opens and closes 4 - 6 times. After the flushing is completed, close the fuel control valve, and then open the oxidizer control valve for flushing. The pressure in front of the valve is 0.2 MPa, and the flushing time is 120 s. During the flushing process, the valve opens and closes 4 - 6 times. After the flushing is completed, close the oxidizer control valve.

[0019] Furthermore, in step S6, after closing the downstream throat stop valve and staying for 20 min, open the downstream throat stop valve for flushing. Keep the pressure in front of the propellant control valve at 0.2 MPa until the fuel cleaning liquid is consumed. During the flushing process, the fuel control valve opens and closes 8 - 10 times. After the flushing is completed, close the fuel control valve. The number of purging times after cleaning is 5 times, and each purging time is 3 s.

[0020] Furthermore, in step S7, after closing the downstream throat stop valve and staying for 20 min, open the downstream throat stop valve for flushing. Keep the pressure in front of the propellant control valve at 0.2 MPa until the oxidizer cleaning liquid is consumed. During the flushing process, the oxidizer control valve opens and closes 8 - 10 times. After the flushing is completed, close the oxidizer control valve. The number of purging times after cleaning is 5 times, and each purging time is 3 s. Then, the oxidizer path and the fuel path are alternately purged no less than 5 times, and each purging time is 3 s; finally, the two paths are purged simultaneously for 100 s.

[0021] Furthermore, in step S8, after closing the downstream throat stop valve and staying for 20 min, open the downstream throat stop valve for flushing. Keep the pressure in front of the fuel control valve and the oxidizer control valve at 0.2 MPa. First, clean for 120 s. During the flushing process, the fuel control valve and the oxidizer control valve open and close simultaneously 4 - 6 times. After the flushing is completed, close the fuel control valve and the oxidizer control valve;

[0022] Then continue with the flushing until the deionized water in both containers is consumed. During the cleaning process, take samples of the flushed deionized water from the engine outlet every 1 minute, and then perform pH analysis on each sample until the pH difference between the deionized water flowing into and out of the engine is less than 0.05, at which point the deionized water rinsing can end.

[0023] Further, in the step S9, the fuel path and the oxidizer path are alternately purged for not less than 10 times, each time for 5 s, and the simultaneous purging time is 30 s.

[0024] Further, in the step S9, the temperature of the normal-temperature nitrogen is 0 - 30 °C, and the temperature of the hot nitrogen is 80 - 100 °C.

[0025] Further, in the step S10, the pressure of the vacuum drying does not exceed 133 Pa, the temperature is 80 °C, and the time is 4 hours.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. By adding a sealing tooling at the throat in the present invention, the entire area of the inner wall of the high-temperature and high-pressure combustion chamber is soaked for a long time, solving the problems that the residues on the inner wall of the combustion chamber are stubborn and difficult to clean, and it is difficult to comprehensively clean the top area during the horizontal installation.

[0028] 2. After cleaning with the cleaning liquid in the present invention, continue to rinse with deionized water, and sample and analyze the pH of the deionized water before and after rinsing for control, solving the problems of cleaning liquid residue and quantitative control of cleaning quality.

[0029] 3. After cleaning, the present invention adopts a combined purging strategy of "normal-temperature nitrogen + hot nitrogen purging". The normal-temperature nitrogen is used to remove liquid residues and quickly strip the liquid residues attached to the inner surface of the cavity. The hot nitrogen ensures that the surface temperature is higher than the dew point temperature by continuously heating the cavity, ensuring that the liquid is completely evaporated, and at the same time forming a dry and inert environment to prevent the residual liquid from condensing on the low-temperature surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0031] Figure 1 is the working flow chart of the present invention;

[0032] Figure 2 is the schematic diagram of the throat blocked by the sealing tooling after the hot calibration test of the space attitude control engine of the present invention.

[0033] In the figure:

[0034] Oxidizer control valve 1; fuel control valve 2; combustion chamber 3; throat 4; sealing tooling 5; sealing ring 51; hollow ejector rod 52; stop valve 53; fixed bracket 54. Specific embodiments

[0035] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0036] As Figure 1 shown, the present invention provides a method for cleaning a space trajectory control engine after hot calibration test runs, including the following steps:

[0037] Step S1: Conduct a hot calibration test run on the engine on a high-altitude simulation hot test bench to obtain vacuum thrust, mixture ratio, lateral thrust, specific impulse performance, and working temperature parameters. Control the temperature of the oxidizer dinitrogen tetroxide to be 20 ± 2 °C, the temperature of the fuel methylhydrazine to be 20 ± 2 °C. Before the engine starts, the pressure in the high-altitude chamber is less than 150 Pa, and during operation, the pressure in the high-altitude chamber is less than 100 Pa. When the engine is operating, the inlet pressure of the two-way propellant control valve is 1.5 MPa.

[0038] Step S2: Blow out the residual propellant. After the engine test run, conduct a nitrogen purge treatment on the test bench. First, blow out the fuel path, then the oxidizer path, and then blow the two paths alternately for no less than 10 times. The nitrogen purge pressure is 0.5 MPa. After the last purge, close the fuel control valve and the oxidizer control valve.

[0039] Step S3: Clean with cleaning liquid. Connect the engine supply pipeline to the cleaning liquid system. The fuel cleaning liquid enters the fuel valve, and the oxidizer cleaning liquid enters the oxidizer valve. After staying for 20 min, open the fuel control valve for flushing, keep the pressure in front of the propellant control valve at 0.2 MPa, and the flushing time is 120 s. During the flushing process, the fuel control valve opens and closes 4 - 6 times. After the flushing is completed, the fuel control valve should be closed. Then open the oxidizer control valve for flushing, the pressure in front of the valve is 0.2 MPa, and the flushing time is 120 s. During the flushing process, the oxidizer control valve opens and closes 4 - 6 times. After the flushing is completed, the oxidizer control valve should be closed. The cleaned oxidizer cleaning liquid and fuel cleaning liquid are directly discharged through the engine outlet, and neither is allowed to be recycled.

[0040] Step S4: Blow out the cleaning liquid. Alternately purge the fuel path and the oxidizer path with nitrogen for no less than 10 times, and finally purge the two paths simultaneously. After purging, close the control valves of the two paths.

[0041] Step S5: Block the throat with a sealing tooling, move the fixed bracket to apply a certain pressure to form a good seal with the throat prepared with a high-temperature oxidation-resistant coating on the surface. As Figure 2 shown, the sealing tooling 5 blocks the throat 4. The sealing tooling 5 consists of a sealing ring 51, a hollow ejector rod 52, a stop valve 53, and a fixed bracket 54. The material of the sealing ring is ethylene propylene rubber, with a Rockwell hardness of 70, a rubber shrinkage rate of 1.8%, a surface roughness not less than 1.6, and no defects such as impurities, unevenness, and cracks are allowed. The stop valve is remotely controlled to open and close through a measurement and control system.

[0042] Step S6: Immerse, clean, and purge the fuel path. Open the fuel control valve 2 (at this time, the oxidizer control valve is in the closed state), fill the fuel cleaning liquid to the area near the throat 4 of the thrust chamber, then close the downstream stop valve of the throat to achieve the immersion of the entire combustion chamber 3. After staying for 20 min, open the downstream stop valve of the throat for flushing, maintain the pressure in front of the propellant control valve at 0.2 MPa until the fuel cleaning liquid is consumed. During the flushing process, the fuel control valve opens and closes 8 - 10 times. After the flushing is completed, close the fuel control valve. The cleaning liquid after cleaning is recovered using a container and is allowed to be used again when cleaning the fuel path. After cleaning, purge this path 5 times, with each purge time being 3 s and the purge nitrogen pressure being 0.5 MPa. After purging, the fuel control valve is in the closed state.

[0043] Step S7: Immerse, clean, and purge the oxidizer path. Open the oxidizer control valve 1 (at this time, the fuel control valve is in the closed state), fill the oxidizer cleaning liquid to the area near the throat 4 of the thrust chamber, then close the downstream stop valve of the throat to achieve the immersion of the entire combustion chamber 3. After staying for 20 min, open the downstream stop valve of the throat for flushing, maintain the pressure in front of the propellant control valve at 0.2 MPa until the oxidizer cleaning liquid is consumed. During the flushing process, the oxidizer control valve opens and closes 8 - 10 times. After the flushing is completed, close the oxidizer control valve. The cleaning liquid after cleaning is recovered using a container and is allowed to be used again when cleaning the oxidizer path. After cleaning, purge this path 5 times, with each purge time being 3 s. Then, alternately purge the oxidizer path and the fuel path not less than 5 times, with each purge time being 3 s; finally, purge both paths simultaneously for 100 s, and after purging, close the control valves of both paths. The purge nitrogen pressure is 0.5 MPa.

[0044] Step S8: Engine deionized water cleaning treatment. Connect the engine supply pipeline to the deionized water cleaning system. Open the fuel control valve and oxidizer control valve of the engine. After filling the deionized water to the area near the throat of the thrust chamber, close the downstream cut-off valve of the throat. After staying for 20 minutes, open the downstream cut-off valve of the throat for flushing, and maintain the pressure in front of the fuel control valve and oxidizer control valve at 0.2 MPa. First, clean for 120 seconds. During the flushing process, the two valves open and close simultaneously 4 - 6 times. After the flushing is completed, close the fuel control valve and oxidizer control valve. The cleaned deionized water is directly discharged through the engine outlet and is not allowed to be recycled. Then continue to flush until the deionized water in the two containers is consumed (at least rinsed more than 3 times). During the cleaning process, take samples of the cleaned deionized water from the engine outlet every 1 minute, and then conduct pH analysis on each sample. The deionized water rinsing process can only end when the pH difference between the deionized water flowing into and out of the engine is less than 0.05. The cleaned deionized water is recycled using a container and is not allowed to be used for the next cleaning.

[0045] Step S9: Engine nitrogen purging. First, purge with normal-temperature nitrogen. The fuel path and oxidizer path are alternately purged no less than 10 times, 5 seconds each time. Finally, the two paths are purged simultaneously for 30 seconds. After purging, the control valves of the two paths are closed. Then purge with hot nitrogen. The fuel path and oxidizer path are alternately purged no less than 10 times, 5 seconds each time. Finally, the two paths are purged simultaneously for 30 seconds. After purging, the control valves of the two paths are closed; the temperature of the normal-temperature nitrogen is 15 °C, and the temperature of the hot nitrogen is 85 °C.

[0046] Step S10: Engine vacuum drying. After the comprehensive engine cleaning treatment is completed, immediately remove the engine from the test stand. The engine is then subjected to vacuum drying, with the pressure not exceeding 133 Pa, the temperature being 80 °C, and the time being 4 hours.

[0047] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0048] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments. Those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined arbitrarily.

Claims

1. A method for cleaning a space orbit control engine after a thermal benchmark test, characterized in that: include: Step S1: performing a thermal calibration test on the engine on a test bench to obtain vacuum thrust, mixture ratio, lateral thrust, specific impulse performance and operating temperature parameters; Step S2: After the hot calibration test, the residual propellant is purged with nitrogen on the test bench. The fuel path is purged first, and then the oxidant path is purged. The two paths are purged alternately. After the last purging, the fuel control valve and the oxidant control valve are closed. Step S3: the fuel cleaning liquid enters the fuel control valve, the oxidant cleaning liquid enters the oxidant control valve, and after cleaning, the oxidant cleaning liquid and the fuel cleaning liquid are discharged through the engine outlet; Step S4: The fuel path and the oxidant path are alternately purged with nitrogen, and finally the two paths are purged simultaneously, and after the purging, the fuel control valve and the oxidant control valve are closed; Step S5: plugging the throat of the thrust chamber with a sealing tool, moving the fixed bracket to apply a certain pressure, and forming a seal between the throat of the thrust chamber with a high-temperature anti-oxidation coating on the surface; Step S6: Open the fuel control valve, fill the fuel cleaning liquid into the throat of the thrust chamber, close the stop valve downstream of the throat of the thrust chamber, stay for a preset time, open the stop valve downstream of the throat for flushing, and keep the propellant control valve at a preset valve front pressure until the fuel cleaning liquid is consumed. After flushing, nitrogen is blown off, and the fuel control valve is in a closed state after blowing off; Step S7: Open the oxidizer control valve, fill the oxidizer cleaning liquid into the throat of the thrust chamber, close the stop valve downstream of the throat, stay for a preset time, open the stop valve downstream of the throat for flushing, and keep the propellant control valve at a preset valve front pressure until the oxidizer cleaning liquid is consumed. After flushing, blow nitrogen, then blow the oxidizer path and the fuel path alternately, and finally blow the two paths at the same time. After blowing, close the fuel control valve and the oxidizer control valve; Step S8: Open the engine fuel control valve and oxidant control valve, fill the throat of the thrust chamber with deionized water, close the throat downstream stop valve, stay for a preset time, open the throat downstream stop valve for flushing, keep the fuel control valve and the oxidant control valve at a preset valve front pressure, and during the cleaning process, sample the cleaned deionized water from the engine outlet, and then perform pH analysis on each sample until the pH difference between the deionized water flowing into and out of the engine is less than a preset value, then stop the deionized water rinsing; Step S9: First, blow the fuel line and the oxidant line with nitrogen at room temperature, blow the fuel line and the oxidant line alternately, and finally blow the two lines simultaneously, after blowing, close the fuel control valve and the oxidant control valve, then blow the fuel line and the oxidant line with hot nitrogen, blow the fuel line and the oxidant line alternately, and finally blow the two lines simultaneously, after blowing, close the fuel control valve and the oxidant control valve; Step S10: remove the engine from the test bench and perform vacuum drying.

2. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In step S1, the temperature of the oxidant nitrogen tetroxide is controlled to be 20±2°C, the temperature of the fuel methylhydrazine is controlled to be 20±2°C, the high-altitude cabin pressure is less than 150Pa before the engine is started, and the high-altitude cabin pressure is less than 100Pa during operation. When the engine is working, the inlet pressure of the two-way propellant control valve is 1.5MPa.

3. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: The nitrogen pressure of nitrogen purge is 0.5 MPa.

4. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In the step S3, after the oxidant cleaning liquid enters the oxidant control valve and stays there for 20 minutes, the fuel control valve is opened for flushing, the pressure before the propellant control valve is maintained at 0.2 MPa, the flushing time is 120 seconds, and during the flushing process, the valve is opened and closed 4 to 6 times. After the flushing is completed, the fuel control valve is closed, and then the oxidant control valve is opened for flushing. The pressure before the valve is 0.2 MPa, the flushing time is 120 seconds, and during the flushing process, the valve is opened and closed 4 to 6 times. After the flushing is completed, the oxidant control valve is closed.

5. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In step S6, after closing the stop valve downstream of the throat and staying for 20 minutes, the stop valve downstream of the throat is opened for flushing, and the pressure before the propellant control valve is maintained at 0.2MPa until the fuel cleaning liquid is consumed. During the flushing process, the fuel control valve is opened and closed 8 to 10 times. After the flushing is completed, the fuel control valve is closed, and the post-cleaning blowdown is performed 5 times, and each blowdown time is 3s.

6. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In step S7, after closing the stop valve downstream of the throat and staying for 20 minutes, the stop valve downstream of the throat is opened for flushing, and the pressure before the propellant control valve is maintained at 0.2MPa until the oxidant cleaning liquid is consumed. During the flushing process, the oxidant control valve is opened and closed 8 to 10 times. After the flushing, the oxidant control valve is closed, and the post-cleaning blowdown is performed 5 times, each blowdown time is 3s, and then the oxidant line and the fuel line are blown alternately for no less than 5 times, each blowdown time is 3s; finally, the two lines are blown simultaneously for 100s.

7. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In the step S8, after closing the throat downstream stop valve and staying for 20 minutes, open the throat downstream stop valve for flushing, maintain the pressure before the fuel control valve and the oxidant control valve at 0.2MPa, and clean for 120s. During the flushing process, the fuel control valve and the oxidant control valve are opened and closed at the same time for 4 to 6 times. After the flushing is completed, the fuel control valve and the oxidant control valve are closed; Then continue rinsing until the deionized water in the two containers is consumed. During the cleaning process, sample the deionized water after cleaning from the engine outlet every 1 minute, and then perform pH analysis on each sample until the pH difference between the deionized water flowing into and out of the engine is less than 0.

05. The deionized water rinsing can then be completed.

8. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In step S9, the fuel path and the oxidant path are blown off alternately for no less than 10 times, each time for 5 seconds, and the blowing time is 30 seconds.

9. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In step S9, the temperature of the normal temperature nitrogen is 0-30°C, and the temperature of the hot nitrogen is 80-100°C.

10. The method for cleaning a space orbit control engine after thermal calibration test according to claim 1, characterized in that: In step S10, the vacuum drying pressure is no more than 133 Pa, the temperature is 80° C., and the time is 4 hours.

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