Hydraulic system oil leakage amount calculation method considering temperature compensation

Abstract

The invention provides a hydraulic system oil leakage amount calculation method considering temperature compensation. The hydraulic system oil leakage amount calculation method includes the following steps that firstly, the thermal expansion coefficient of turbine oil is calibrated; 2, calibrating an initial volume; 3, calculating a temperature compensation volume; step 4, real-time volume monitoring; 5, calculating the oil leakage amount; and step 6, data processing. According to the method, the problem caused by volume change due to neglect of the temperature in a traditional oil leakage amount calculation method is solved, the oil leakage amount negative value phenomenon is eliminated, the oil leakage amount calculation error is remarkably reduced, and the reliability and applicability of oil leakage amount monitoring of the hydraulic system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic systems, and in particular to a method for calculating oil leakage of a hydraulic system taking temperature compensation into account. Background Art

[0002] In a hydropower station, the hydraulic system consists of a return oil tank, pipelines, oil pump motor, oil pressure tank, valve group, cooler and other parts. Figure 1 As shown, the controller controls the oil pump's loading and unloading, pressurizing turbine oil from the return tank and transferring it to the pressure tank. This provides pressurized oil for the speed control system's guide vane opening and closing. Due to long-term operation or aging seals, hydraulic systems inevitably experience persistent oil leakage, leading to pressure drops and even equipment failure. Therefore, accurately calculating oil leakage is crucial for system maintenance and fault warning.

[0003] The existing method for calculating oil leakage is: 1) Initial volume calibration: After the hydraulic system is pressurized for the first time, the initial liquid level in the tank is collected. and the initial liquid level in the oil pressure tank .

[0004] 2) Real-time volume monitoring: The sensor collects the liquid level in the tank in real time and the liquid level in the oil tank .

[0005] 3) Calculation of oil leakage: The oil leakage is equal to the sum of the initial volumes of the return oil tank and the pressure oil tank minus the sum of their real-time volumes, that is, . is the length of the return tank, The width of the fuel tank, is the inner radius of the oil pressure tank.

[0006] The disadvantages of the above technical methods are: 1) The temperature of turbine oil in a hydraulic system varies from 20°C to 45°C, and the volume of turbine oil changes significantly with temperature. Existing methods ignore temperature compensation, causing the calculated results to deviate from the actual oil leakage volume.

[0007] 2) When the oil temperature is high, the volume expansion may cause the calculated oil leakage to be negative, which is inconsistent with the actual situation. Summary of the Invention

[0008] The present invention aims to provide a method for calculating the oil leakage of a hydraulic system taking temperature compensation into account, so as to solve the problem caused by ignoring the volume change caused by temperature in the traditional oil leakage calculation method, eliminate the phenomenon of negative oil leakage value, significantly reduce the error in oil leakage calculation, and improve the reliability and applicability of hydraulic system oil leakage monitoring.

[0009] In order to achieve the above technical features, the purpose of the present invention is achieved as follows: a method for calculating the oil leakage of a hydraulic system taking into account temperature compensation comprises the following steps: Step 1: Turbine oil thermal expansion coefficient Calibration; Step 2: Initial volume Calibration; Step 3: Calculate the temperature compensation volume ; Step 4: Real-time volume monitor; Step 5: Oil Leakage calculate; Step six: data processing.

[0010] Preferably, the step 1 specifically includes: Based on the linear relationship between the volume and temperature of turbine oil in the low temperature range of 20℃ to 50℃, the turbine oil sample was heated and the volume of the turbine oil was recorded every 5℃ starting from 20℃, for a total of 8 sets of data. Based on the recorded data, the temperature difference was used as the horizontal axis and the volume change rate as the vertical axis. The slope of the straight line was fitted using the least squares method. .

[0011] Preferably, the step 2 specifically includes: After the hydraulic system is boosted to the rated pressure for the first time, the initial liquid level in the oil tank is collected. and the initial liquid level in the oil pressure tank , the data sampling frequency is 1Hz, then the initial volume is: ; Where, is the length of the return tank, The width of the fuel tank, is the inner radius of the oil pressure tank.

[0012] Preferably, the initial volume can be recalibrated at any time when replacing the equipment or according to actual needs. .

[0013] Preferably, the step three specifically includes: Temperature compensation volume It is the sum of the volume change of turbine oil in the pressure tank and the volume change of the return tank. According to the principle of thermal expansion, the volume change of turbine oil in the return tank with temperature is: ; Changes in turbine oil volume in the oil pressure tank with temperature: ; Then the temperature compensation volume is: ; Where, It is the initial temperature of turbine oil after the hydraulic system is first pressurized. is the temperature of the turbine oil in the oil tank at the current moment, It is the temperature of the turbine oil in the return tank at the current moment.

[0014] Preferably, the step 4 specifically includes: The liquid level in the fuel tank is collected in real time by the sensor and the liquid level in the oil tank , the data sampling frequency is 1Hz, then the real-time volume is: .

[0015] Preferably, the step five specifically includes: The oil leakage volume is equal to the initial volume - real-time volume - temperature compensation volume, that is: .

[0016] Preferably, in step 6, when the sensor measurement value is disturbed or the oil level fluctuates due to the oil pump loading moment, the oil leakage There will be false alarms, and the calculated data needs to be eliminated for outliers and filled with missing values; Negative data are directly removed, and other data are processed using a sliding window. IQR The criterion is to eliminate outliers.

[0017] Preferably, the specific method for data processing in step six is: 1) Arrange the data in ascending order and calculate the first quartile and the third quartile ,in n is the number of data points, sampling frequency is 1Hz; 2) Use linear interpolation to calculate the value of the first quartile Q 1 and the third quartile value Q 3, then the interquartile range ; 3) Determine the upper and lower limits of normal values. Values ​​within the range of the lower and upper limits are marked as normal, and other values ​​are removed as abnormal. ,in k Take the value as 1.5, fill in missing values, after outliers are removed, the data point is missing, calculate the average value of the 5 nearest data points to fill in the data point; dynamically modify according to the comparison between the test results and the actual situation k value until the error meets the requirement.

[0018] Preferably, the number of data points in step 6 n=20.

[0019] The present invention has the following beneficial effects: 1. The present invention eliminates temperature interference through dynamic volume compensation, reduces the calculation error of oil leakage, and provides timely oil leakage warning, thus avoiding major risks such as major hydraulic system failure and unit shutdown caused by large amounts of oil leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and examples.

[0021] Figure 1 This is the hydraulic system structure diagram.

[0022] Figure 2 It is the flow chart of oil leakage calculation of the present invention.

[0023] Figure 3 This is a data processing flow chart of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0025] Example 1: See also Figure 1-3 A method for calculating oil leakage in a hydraulic system taking temperature compensation into account comprises the following steps: Step 1: Turbine oil thermal expansion coefficient Calibration; Based on the linear relationship between the volume and temperature of turbine oil in the low temperature range of 20℃ to 50℃, the turbine oil sample was heated and the volume of the turbine oil was recorded every 5℃ starting from 20℃, for a total of 8 sets of data. Based on the recorded data, the temperature difference was used as the horizontal axis and the volume change rate as the vertical axis. The slope of the straight line was fitted using the least squares method. .

[0026] Step 2: Initial volume Calibration; After the hydraulic system is boosted to the rated pressure for the first time, the initial liquid level in the oil tank is collected. and the initial liquid level in the oil pressure tank , the data sampling frequency is 1Hz, then the initial volume is: ; Where, is the length of the return tank, The width of the fuel tank, is the inner radius of the oil pressure tank.

[0027] The initial volume can be recalibrated at any time when replacing equipment or according to actual needs .

[0028] Step 3: Calculate the temperature compensation volume ; Temperature compensation volume It is the sum of the volume change of turbine oil in the pressure tank and the volume change of the return tank. According to the principle of thermal expansion, the volume change of turbine oil in the return tank with temperature is: ; Changes in turbine oil volume in the oil pressure tank with temperature: ; Then the temperature compensation volume is: ; Where, It is the initial temperature of turbine oil after the hydraulic system is first pressurized. is the temperature of the turbine oil in the oil tank at the current moment, It is the temperature of the turbine oil in the return tank at the current moment.

[0029] Step 4: Real-time volume monitor; The liquid level in the fuel tank is collected in real time by the sensor and the liquid level in the oil tank , the data sampling frequency is 1Hz, then the real-time volume is: .

[0030] Step 5: Oil leakage calculate; The oil leakage volume is equal to the initial volume - real-time volume - temperature compensation volume, that is: .

[0031] Step six, data processing; When the sensor measurement value is disturbed or the oil level fluctuates due to the instantaneous loading of the oil pump, the oil leakage There will be false alarms, and the calculated data needs to be eliminated for outliers and filled with missing values; Negative data are directly removed, and other data are processed using a sliding window. IQR The criterion is to eliminate outliers.

[0032] Preferably, the specific method for data processing in step six is: 1) Arrange the data in ascending order and calculate the first quartile and the third quartile ,in n is the number of data points, sampling frequency is 1Hz; 2) Use linear interpolation to calculate the value of the first quartile Q1 and the third quartile value Q 3, then the interquartile range ; 3) Determine the upper and lower limits of normal values. Values ​​within the range of the lower and upper limits are marked as normal, and other values ​​are removed as abnormal. ,in k Take the value as 1.5, fill in missing values, after outliers are removed, the data point is missing, calculate the average value of the 5 nearest data points to fill in the data point; dynamically modify according to the comparison between the test results and the actual situation k value until the error meets the requirement.

[0033] Preferably, the number of data points in step 6 n =20.

[0034] Example 2: The present invention aims to solve the problem caused by ignoring the volume change caused by temperature in the traditional oil leakage calculation method, eliminate the negative oil leakage phenomenon, significantly reduce the error in oil leakage calculation, and improve the reliability and applicability of hydraulic system oil leakage monitoring.

[0035] The technical solution of the present invention comprises the following steps: Step 1: Turbine oil thermal expansion coefficient Calibration. In the low temperature range of 20℃ to 50℃, the volume of turbine oil is linearly related to temperature. Heat the turbine oil sample and record the volume of the turbine oil every 5℃ starting from 20℃, for a total of 8 sets of data. Based on the recorded data, use the temperature difference as the horizontal axis and the volume change rate as the vertical axis to fit a straight line using the least squares method. The slope of the straight line is the thermal expansion coefficient of the turbine oil. .

[0036] Step 2: Initial volume Calibration. After the hydraulic system is boosted to the rated pressure for the first time, the initial liquid level in the oil tank is collected. and the initial liquid level in the oil pressure tank , the data sampling frequency is 1Hz, then the initial volume . is the length of the return tank, The width of the fuel tank, The initial volume can be recalibrated at any time when replacing equipment or according to actual needs. .

[0037] Step 2: Calculate the temperature compensation volume When the oil pump is idling, the oil in the return tank will be pumped out and sent back to the return tank through the cooler. When the oil temperature in the return tank is higher than the set value, the cooler will start cooling water to run; when the oil temperature in the return tank is lower than the set value, the cooler will stop cooling water and will not run. The turbine oil in the pressure tank is not cooled, and its temperature will be higher than that in the return tank. Due to the different temperatures, the volume change caused by the temperature needs to be calculated separately, so The sum of the volume change of the turbine oil in the pressure tank and the volume change of the return oil tank. According to the principle of thermal expansion, the volume change of the turbine oil in the return oil tank with temperature , the change of turbine oil volume in the oil pressure tank with temperature , then the temperature compensation volume ,in It is the initial temperature of turbine oil after the hydraulic system is first pressurized. is the temperature of the turbine oil in the oil tank at the current moment, It is the temperature of the turbine oil in the return tank at the current moment.

[0038] Step 3: Real-time volume Monitoring. The liquid level in the fuel tank is collected in real time by the sensor. and the liquid level in the oil tank , the data sampling frequency is 1Hz, then the real-time volume .

[0039] Step 4: Oil leakage Calculation. The oil leakage volume should be equal to the initial volume - real-time volume - temperature compensation volume, that is .

[0040] Step 5: Data processing. When the sensor measurement value is disturbed or the oil level fluctuates due to the instantaneous loading of the oil pump, the amount of oil leakage There may be false alarms, and the calculated data needs to be filtered out for outliers and filled with missing values. Data with negative values ​​are directly eliminated, and the other data are filtered out using the sliding window IQR criterion, with a sliding window size of 20s. 1) After sorting the data in ascending order, calculate the first quartile and the third quartile ,in n is the number of data points, the sampling frequency is 1Hz, that is n =20. 2) Use linear interpolation to calculate the value of the first quartile Q 1 and the third quartile value Q 3, then the interquartile range 3) Determine the upper and lower limits of normal values, and mark the values ​​within the range of the lower and upper limits as normal, and remove other values ​​as abnormal. ,in kThe value is 1.5. Missing value filling: after outliers are removed, if the data point is missing, the average value of the 5 nearest neighboring data points is calculated to fill the missing data point. Dynamic modification based on the comparison between the test results and the actual situation k value until the error meets the requirements. For the specific process, please see the attached Figure 2 and attached Figure 3 shown.

[0041] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for calculating oil leakage in a hydraulic system taking temperature compensation into account, characterized in that: The following steps are involved: Step 1: Turbine oil thermal expansion coefficient Calibration; Step 2: Initial volume Calibration; Step 3: Calculate the temperature compensation volume ; Step 4: Real-time volume monitor; Step 5: Oil Leakage calculate; Step six: data processing.

2. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 1, characterized in that: The step 1 specifically includes: Based on the linear relationship between the volume and temperature of turbine oil in the low temperature range of 20℃ to 50℃, the turbine oil sample was heated and the volume of the turbine oil was recorded every 5℃ starting from 20℃, for a total of 8 sets of data. Based on the recorded data, the temperature difference was used as the horizontal axis and the volume change rate as the vertical axis. The slope of the straight line was fitted using the least squares method. .

3. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 2, characterized in that: The second step specifically includes: After the hydraulic system is boosted to the rated pressure for the first time, the initial liquid level in the oil tank is collected. and the initial liquid level in the oil pressure tank , the data sampling frequency is 1Hz, then the initial volume is: ； Where, is the length of the return tank, The width of the fuel tank, is the inner radius of the oil pressure tank.

4. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 3, characterized in that: The initial volume can be recalibrated at any time when replacing equipment or according to actual needs .

5. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 3, characterized in that: The step three specifically includes: Temperature compensation volume It is the sum of the volume change of turbine oil in the pressure tank and the volume change of the return tank. According to the principle of thermal expansion, the volume change of turbine oil in the return tank with temperature is: ； Changes in turbine oil volume in the oil pressure tank with temperature: ； Then the temperature compensation volume is: ； Where, It is the initial temperature of turbine oil after the hydraulic system is first pressurized. is the temperature of the turbine oil in the oil tank at the current moment, It is the temperature of the turbine oil in the return tank at the current moment.

6. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 5, characterized in that: The step 4 specifically includes: The liquid level in the fuel tank is collected in real time by the sensor and the liquid level in the oil tank , the data sampling frequency is 1Hz, then the real-time volume is: 。 7. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 6, characterized in that: The step five specifically includes: The oil leakage volume is equal to the initial volume - real-time volume - temperature compensation volume, that is: 。 8. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 7, characterized in that: In step 6, when the sensor measurement value is disturbed or the oil level fluctuates due to the oil pump loading moment, the oil leakage There will be false alarms, and the calculated data needs to be eliminated for outliers and filled with missing values; Negative data are directly removed, and other data are processed using a sliding window. IQR The criterion is to eliminate outliers.

9. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 8, characterized in that: The specific method of data processing in step 6 is as follows: 1) Arrange the data in ascending order and calculate the first quartile and the third quartile ,in n is the number of data points, sampling frequency is 1Hz; 2) Use linear interpolation to calculate the value of the first quartile Q 1 and the third quartile value Q 3, then the interquartile range ; 3) Determine the upper and lower limits of normal values. Values ​​within the range of the lower and upper limits are marked as normal, and other values ​​are removed as abnormal. ,in k Take the value as 1.5, fill in missing values, after outliers are removed, the data point is missing, calculate the average value of the 5 nearest data points to fill in the data point; dynamically modify according to the comparison between the test results and the actual situation k value until the error meets the requirement.

10. The method for calculating oil leakage in a hydraulic system taking temperature compensation into account according to claim 9, characterized in that: The number of data points in step 6 n =20.

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