A method for monitoring the condition of a liquid rocket engine based on a temperature sensor during the precooling process.

Abstract

This invention discloses a method for monitoring the state of a temperature sensor in a liquid rocket engine based on the precooling process. It addresses the problems in traditional liquid rocket engine precooling methods, where numerous cable connections and the thermocouple sensor's sensing point located at the junction of two metals increase the number of transition points, leading to short circuits at cable junctions and the inability to obtain actual temperature values ​​at the engine's measuring points. In this invention, due to the high sensitivity of the inlet temperature, the precooling time is determined based on the inlet temperature, improving monitoring accuracy. Furthermore, this invention enables trend analysis of engine temperature changes during the precooling stage. Based on the precooling time, curve fitting is performed on the measuring point temperatures before and after precooling to complete the precooling state diagnosis of the liquid rocket engine, ensuring the reliability of temperature measurements during test runs.

Description

Technical Field

[0001] This invention relates to a method for monitoring the condition of liquid rocket engines, specifically a method for monitoring the condition of liquid rocket engines based on a temperature sensor during the precooling process. Background Technology

[0002] Liquid rocket engine testing is a crucial step in engine development and delivery. Firing tests are the primary means of engine assembly inspection and acquisition of core performance parameters. The firing process is characterized by high cost, high risk, and irreversibility.

[0003] Due to the high risks involved in rocket engine testing, and to ensure the normal operation of the data acquisition equipment, the temperature sensor is installed at a considerable distance from the acquisition equipment. Therefore, a cable connection is required to remotely acquire and analyze the temperature sensor signal. A typical cable connection diagram for a thermocouple temperature sensor is shown below. Figure 1 As shown, since the temperature sensing point of the thermocouple temperature sensor is located at the junction of the two metals, when the number of connecting links increases, it is easy to cause a short circuit at the cable adapter. When a short circuit occurs at the adapter, the temperature measured by the acquisition card is located at the short circuit point, and the actual temperature value of the measuring point on the engine cannot be obtained.

[0004] For actual temperature measurement systems, due to the large number of temperature measurement points during the test run, the temperature sensor status is only simply verified during the temperature sensor installation phase based on manual heating tests and the continuity of the temperature sensor cables. In reality, for temperature sensors with multiple adapters, subsequent thermal protection of the temperature sensor may destroy the above verification results, making it difficult to achieve real-time monitoring of the temperature sensor status after installation. Summary of the Invention

[0005] The purpose of this invention is to address the problem that in liquid rocket engine precooling state monitoring methods, the temperature sensor status is only verified during the installation phase based on manual heating tests and the continuity of temperature sensor cables. However, in actual practice, subsequent thermal protection of the temperature sensor may destroy the above verification results, making it difficult to achieve real-time monitoring of the temperature sensor status after installation. Therefore, this invention provides a liquid rocket engine temperature sensor status monitoring method based on the precooling process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for monitoring the condition of a liquid rocket engine based on a temperature sensor during the precooling process, characterized by the following steps:

[0008] Step 1: Use temperature sensors to collect the temperature at the oxygen system inlet and measuring point of the rocket engine to obtain the inlet temperature and measuring point temperature.

[0009] Step 2: Set the low temperature threshold. By comparing the inlet temperature with the low temperature threshold in real time, determine the pre-cooling time for inputting cryogenic liquid oxygen into the oxygen system.

[0010] Step 3: Perform curve fitting on the temperature of the measuring point before and after the pre-cooling moment, respectively, and calculate 2M fitting curve coefficients, M≥2, as the pre-cooling data for one test run.

[0011] Step 4: Conduct multiple test runs. For each test run, obtain the pre-cooling data of each test run using the methods in Steps 1-3, and construct a feature matrix for each pre-cooling data of each test run.

[0012] Step 5: Collect the oxygen system inlet and measuring point temperatures of the rocket engine to be monitored. Execute steps 1-3 to obtain the pre-cooling data of the test vehicle to be monitored. Construct a feature matrix of the test vehicle to be monitored based on the pre-cooling data. Perform statistical characteristic analysis on the feature matrix of the test vehicle to be monitored and the feature matrix constructed from the pre-cooling data of each test in step 4 to determine whether the temperature during the pre-cooling process is abnormal. If it is abnormal, the temperature sensor at that measuring point is in an abnormal state; otherwise, the temperature sensor at that measuring point is normal.

[0013] Furthermore, in step 5, the statistical characteristic analysis of the pre-cooling data of the test vehicle to be monitored and the pre-cooling data of multiple test runs in step 4 specifically involves performing a statistical characteristic analysis of the pre-cooling data of the test vehicle to be monitored and the pre-cooling data of multiple test runs in step 4 according to 3σ.

[0014] Furthermore, step 5 specifically includes:

[0015] Step 5.1: Collect the oxygen system inlet and measuring point temperatures of the rocket engine to be monitored, and execute steps 1-3 to obtain the pre-cooling data of the test vehicle to be monitored;

[0016] Step 5.2: Construct the feature matrix of the test vehicle based on the pre-cooling data of the test vehicle;

[0017] Step 5.3: Combine the feature matrix of the test vehicle to be monitored with the feature matrix constructed from the pre-cooling data of each test in Step 4, and perform statistical characteristic analysis according to 3σ. If the pre-cooling data of the test vehicle to be monitored is normal within the 3σ range, then the temperature sensor at that measuring point is normal; otherwise, the temperature sensor at that measuring point is abnormal.

[0018] Furthermore, in step 2, the low temperature threshold is -160℃.

[0019] Furthermore, in step 3, the method for calculating the coefficients of the 2M fitted curves is the least squares method.

[0020] Furthermore, in step 3, the value of M is 4;

[0021] The 2M fitting curve coefficients include 4 coefficients for fitting the temperature curve of the measuring point before the precooling moment and 4 coefficients for fitting the temperature curve of the measuring point after the precooling moment.

[0022] Furthermore, in step 4, the feature matrix is ​​constructed for each test run precooling data as follows: a 2×4 matrix is ​​constructed for each test run precooling data, where the first row is the fitting curve coefficients before precooling and the second row is the fitting curve coefficients after precooling.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention provides a method for monitoring the status of a temperature sensor in a liquid rocket engine based on a precooling process. Since the inlet temperature is highly sensitive, determining the precooling time based on the inlet temperature can improve the accuracy of monitoring the temperature sensor at the measuring point.

[0025] 2. This invention provides a method for monitoring the state of a liquid rocket engine temperature sensor based on the precooling process. It can analyze the trend of engine temperature changes during the precooling stage, and perform curve fitting on the temperature of the measuring points before and after precooling according to the precooling time to complete the precooling state diagnosis of the liquid rocket engine and ensure the reliability of temperature measurement during the test. Attached Figure Description

[0026] Figure 1 This is a typical cable connection diagram of a thermocouple temperature sensor in the background technology.

[0027] Figure 2 This is a graph showing the trend of ambient temperature change in an embodiment of a liquid rocket engine temperature sensor status monitoring method based on a precooling process according to the present invention.

[0028] Figure 3 This is a graph showing the trend of inlet temperature change in an embodiment of a liquid rocket engine temperature sensor status monitoring method based on a precooling process according to the present invention.

[0029] Figure 4 This is a fitting graph of the temperature change trend of measuring point 1 before precooling in the first test run of an embodiment of the liquid rocket engine temperature sensor state monitoring method based on the precooling process of the present invention.

[0030] Figure 5 This is a fitting graph of the temperature change trend after precooling at measuring point 1# in the first test run of the embodiment of the liquid rocket engine temperature sensor state monitoring method based on the precooling process of the present invention.

[0031] Figure 6 This is a fitting graph of the temperature change trend of measuring point 1 before precooling in the second test of the embodiment of the liquid rocket engine temperature sensor state monitoring method based on the precooling process of the present invention.

[0032] Figure 7 This is a fitting graph of the temperature change trend after precooling at measuring point 1 in the second test of the embodiment of the liquid rocket engine temperature sensor state monitoring method based on the precooling process of the present invention. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This invention provides a method for monitoring the status of a temperature sensor in a liquid rocket engine based on a precooling process, comprising the following steps:

[0035] Step 1: Use temperature sensors to collect the temperature at the oxygen system inlet of the rocket engine and at measuring point 1, respectively, to obtain the inlet temperature and the temperature at measuring point 1, where 1# represents measuring point number 1.

[0036] For ease of comparison, an ambient temperature sensor was connected to the test bench to detect the ambient temperature of the test vehicle. Figure 2 The figure shows the ambient temperature. According to the changing trend Figure 2 It can be seen that the ambient temperature gradually increases over time.

[0037] Step 2: Since the inlet temperature is highly sensitive, determining the pre-cooling time based on the inlet temperature can improve the accuracy of monitoring. Set the low temperature threshold to -160℃, and determine the pre-cooling time of the input cryogenic liquid oxygen in the oxygen system by comparing the inlet temperature with the low temperature threshold in real time.

[0038] In this embodiment, the precooling time needs to be calculated. This process can be based on the actual operation of the control valves for liquid oxygen input or the inlet temperature of the rocket engine's oxygen system. The purpose of the analysis to determine the pre-cooling time is to clean the temperature data of measuring point 1 before pre-cooling, so as to enable subsequent analysis based on the data after pre-cooling.

[0039] Rocket engine oxygen system inlet temperature The trend of change is as follows Figure 3 As shown; combined with Figure 2 and Figure 3It can be seen that from the moment of precooling, the ambient temperature maintains an upward trend, and this trend is related to the weather conditions on the day of the test. However, the temperature at measuring point #1 is directly related to whether liquid oxygen enters the engine's oxygen system inlet. When liquid oxygen enters, precooling begins, and the temperature at measuring point #1 begins to show a downward trend. By performing curve fitting (trend modeling) on ​​the temperature data after precooling, the precooling state monitoring of the liquid rocket engine can be completed.

[0040] For measuring point #1, two test runs were conducted at different time periods. The temperature change trend before and after pre-cooling in the first test run is as follows: Figure 4 , Figure 5 As shown, the temperature change trend before and after pre-cooling in the second test run is as follows: Figure 6 , Figure 7 As shown; according to Figure 4 , Figure 5 The temperature change trend can be seen at approximately the 1000th data point, Figure 6 , Figure 7 At approximately the 4000th data point, the temperature at this measuring point begins to gradually decrease, showing a clear downward trend. In fact, engine pre-cooling begins at this sampling moment. Since this measuring point is close to the oxygen system, liquid oxygen flows into the engine, causing the engine structure temperature to decrease. Even if no liquid oxygen flows through this measuring point, the temperature at this measuring point still shows a certain downward trend. This shows that the temperature sensor is consistent with the actual physical process, and the temperature sensor at this measuring point can be considered to be in normal condition.

[0041] Firstly, based on the inlet temperature Determine the timing of pre-cooling:

[0042] when , ;

[0043] in, Indicates the inlet temperature. This indicates the sampling time when the inlet temperature is less than -160℃. The value indicates the pre-cooling time, and n represents the number of temperature samples taken at measuring point 1, where n = [0, 1, 2, ..., N] and N represents the total length of the sampled data.

[0044] Step 3: Perform curve fitting on the temperature of the measuring point before and after the pre-cooling time, respectively, and calculate 2M fitting curve coefficients, M≥2, as the pre-cooling data for one test run.

[0045] Based on inlet temperature Determine the pre-cooling time The set of temperatures at measuring point #1 before precooling is represented as follows: Where m represents the sampling time before pre-cooling of measuring point #1, The value range is 0~ .

[0046] The waveform corresponding to the temperature before pre-cooling during the first test run is as follows: Figure 4 As shown in the rising segment. Based on Perform curve fitting (trend modeling) to obtain the fitted curve, expressed as:

[0047] ;

[0048] in, , The coefficients of the four fitting curves before precooling at measuring point #1 are given. The superscript 1 indicates the data from the first test run. The four fitting curve coefficients can be obtained by performing least squares calculation on the above formula.

[0049] When expressing the temperature at measuring point #1 after precooling, the precooling time is used. At time 0, the set of temperatures at measuring point #1 after precooling is represented as: ,in, , Indicates the pre-cooling time Temperature at measuring point #1 Indicates the moment when pre-cooling begins. The sampling time after that.

[0050] The process of curve fitting for the pre-cooled temperature is as follows:

[0051] ;

[0052] in, These are the four fitting curve coefficients for the temperature after precooling at measuring point #1. The superscript 1 indicates the data from the first test run. The four fitting curve coefficients can be obtained by performing least squares calculation on the above formula.

[0053] Step 4: Perform two test runs following steps 1-3 to obtain pre-cooling data from both runs; determine the fitted curve based on the fitted curve coefficients before and after pre-cooling, such as... Figures 4 to 7 The black line in the middle; considering that multiple test runs were conducted at the same temperature measurement point, the fitting curve coefficients of different tests before and after pre-cooling are shown in Table 1:

[0054] Table 1

[0055]

[0056] The curve coefficients 1, 2, 3, and 4 mentioned above are all fitted curve coefficients.

[0057] The pre-cooling data for the first test run includes: the fitting curve coefficients before pre-cooling for the first test run. , The coefficients of the fitting curve after precooling .

[0058] The pre-cooling data for the second test run includes: coefficients before pre-cooling for the second test run. , The coefficient after pre-cooling in the second test run .

[0059] The feature matrix constructed based on the pre-cooling data from the first and second test runs can be represented as follows:

[0060] ;

[0061] ;

[0062] in, This represents the feature matrix constructed from the pre-cooling data of the first test run at measuring point #1. This represents the feature matrix constructed from the pre-cooling data of the second test run at measuring point #1, used for numerical analysis based on the feature matrix.

[0063] Step 5: Collect the oxygen system inlet and measuring point temperatures of the rocket engine during the monitoring period, execute steps 1-3 to obtain the pre-cooling data of the test vehicle under monitoring, and construct the feature matrix of the test vehicle under monitoring based on the pre-cooling data. The feature matrix of the vehicle to be monitored In step 4, the feature matrix of the precooling data from each test run is constructed and statistically analyzed according to 3σ. If the precooling data of the test vehicle under monitoring is within the 3σ range, then the temperature sensor at that measuring point is normal; otherwise, the precooling data of the test vehicle under monitoring is abnormal, and the temperature sensor at that measuring point is abnormal.

[0064] In this embodiment, data from two test runs are used for analysis. Figure 4 , Figure 5 These are the temperature signals before and after the first test run's pre-cooling. Figure 6 , Figure 7 These are the temperature signals before and after the second actual measurement of pre-cooling. Analysis is performed using a feature matrix instead of directly analyzing the temperature values. This is primarily to avoid discrepancies in the absolute values ​​of the temperature signals due to changes in ambient temperature, as well as differences in the original signal values ​​and lengths caused by human intervention during the pre-cooling process.

[0065] In this embodiment, if the pre-cooling data of the test vehicle under monitoring is abnormal, it is determined that there may be an abnormality in the temperature acquisition system or in the temperature sensor measurement process.

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for monitoring the condition of a temperature sensor in a liquid rocket engine based on a precooling process, characterized in that, Includes the following steps: Step 1: Use temperature sensors to collect the temperature at the oxygen system inlet and measuring point of the rocket engine to obtain the inlet temperature and measuring point temperature. Step 2: Set the low temperature threshold. By comparing the inlet temperature with the low temperature threshold in real time, determine the pre-cooling time for inputting cryogenic liquid oxygen into the oxygen system. Step 3: Perform curve fitting on the temperature of the measuring point before and after the pre-cooling moment, respectively, and calculate 2M fitting curve coefficients, M≥2, as the pre-cooling data for one test run. Step 4: Conduct multiple test runs. For each test run, obtain the pre-cooling data of each test run using the methods in Steps 1-3, and construct a feature matrix for each pre-cooling data of each test run. Step 5: Collect the oxygen system inlet and measuring point temperatures of the rocket engine to be monitored. Execute steps 1-3 to obtain the pre-cooling data of the test vehicle to be monitored. Construct a feature matrix of the test vehicle to be monitored based on the pre-cooling data. Perform statistical characteristic analysis on the feature matrix of the test vehicle to be monitored and the feature matrix constructed from the pre-cooling data of each test in step 4 to determine whether the temperature of the pre-cooling process to be monitored is abnormal. If it is abnormal, the temperature sensor at that measuring point is in an abnormal state; otherwise, the temperature sensor at that measuring point is normal. Step 5 specifically involves: Step 5.1: Collect the oxygen system inlet and measuring point temperatures of the rocket engine to be monitored, and execute steps 1-3 to obtain the pre-cooling data of the test vehicle to be monitored; Step 5.2: Construct the feature matrix of the test vehicle based on the pre-cooling data of the test vehicle; Step 5.3: Combine the feature matrix of the test vehicle to be monitored with the feature matrix constructed from the pre-cooling data of each test in Step 4, and perform statistical characteristic analysis according to 3σ. If the pre-cooling data of the test vehicle to be monitored is normal within the 3σ range, then the temperature sensor at that measuring point is normal; otherwise, the temperature sensor at that measuring point is abnormal.

2. The method for monitoring the condition of a liquid rocket engine temperature sensor based on a precooling process according to claim 1, characterized in that, In step 2, the low temperature threshold is -160℃.

3. The method for monitoring the condition of a liquid rocket engine temperature sensor based on a precooling process according to claim 1, characterized in that, In step 3, the method for calculating the coefficients of the 2M fitted curves is the least squares method.

4. The method for monitoring the condition of a liquid rocket engine temperature sensor based on a precooling process according to claim 1, characterized in that, In step 3, the value of M is 4; The 2M fitting curve coefficients include 4 coefficients for fitting the temperature curve of the measuring point before the precooling moment and 4 coefficients for fitting the temperature curve of the measuring point after the precooling moment.

5. The method for monitoring the condition of a liquid rocket engine temperature sensor based on a pre-cooling process according to claim 4, characterized in that, In step 4, the feature matrix is ​​constructed from the pre-cooling data of each test run as follows: a 2×4 matrix is ​​constructed from the pre-cooling data of each test run, where the first row is the fitting curve coefficients before pre-cooling and the second row is the fitting curve coefficients after pre-cooling.

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