An intelligent method for determining air tightness of aviation pipelines based on temperature monitoring

Abstract

The present invention discloses a temperature-monitored intelligent air tightness determination method for aviation pipelines, comprising the following steps: S1: the plant air source is filtered through an air source triplet, and the air source pressure is increased to an applicable pressure through a boost valve, the air source triplet is composed of a filter, a pressure reducing valve and a pressure gauge, S2: the reversing valve is responsible for controlling the on-off of the lower test circuit and the exhaust when the test is completed, and the pressure reducing valve adjusts the pressure to the test pressure, the pressure sensor at the interface monitors the pressure in the pipeline to be tested in real time, and the temperature sensor monitors the temperature in the pipeline to be tested. The present invention controls each solenoid valve group according to a predetermined program through a host computer and a PLC, performs an automated air tightness test under a safe pressure, relies on a boost pump to increase the plant air source pressure, realizes the test state from pressurization and pressure maintenance during the test to pressure relief after the test is completed, and monitors the pressure value and temperature value inside the pipeline in real time by setting a high-precision pressure sensor and a temperature sensor.

Description

Technical Field

[0001] The present invention relates to an intelligent air tightness determination method, in particular to an intelligent air tightness determination method for aviation pipelines using temperature monitoring, and belongs to the technical field of air tightness detection of aviation components. Background Art

[0002] Airtightness testing technology is a technology that uses a certain gas to test the sealing performance of the closed cavity to be tested. Due to manufacturing or assembly defects in the part of the closed container to be tested, leaks of different sizes are formed. Because detachable pipe joints have good pressure resistance, sealing properties, easy installation and high reliability, they are widely used in the connection between hydraulic and gas system pipelines in various aircraft. Therefore, as an important component for aviation pipeline connection, the failure of pipe joints will cause major accidents in the aircraft hydraulic and airtight systems, so the research on the sealing and reliability of pipe joints is crucial for aircraft air pressure and hydraulic systems. However, due to the tiny gaps caused by the installation errors at individual joints, the sealing of the entire pipeline system will be seriously damaged. There is an urgent need for high-precision airtightness testing technology to realize the sealing inspection of aviation system pipelines.

[0003] In addition, due to the special properties of the gas itself, the results of the airtight test are often affected by the external environment, among which the ambient temperature is the main factor affecting the accuracy and efficiency of the pipeline sealing test. During the pressurization stage, the test gas rubs against the inner wall of the pipeline, and the large number of aviation pipelines and the large inner wall area cause huge heat to be generated due to friction, which in turn causes the temperature of the gas in the tested container to rise. On the one hand, the pressure of the test gas rises due to the increase in temperature, resulting in a small amount of gas actually flushed into the pipeline; on the other hand, the test gas forms a temperature difference with the ambient temperature. During the pressure stabilization and pressure maintenance process, the gas in the tested container will exchange heat with the outside world, the gas temperature in the container changes, and the gas pressure also changes accordingly, affecting the test results. Specifically, the increase in ambient temperature causes the gas pressure inside the pipeline to increase, and the gas overflows at the leakage point at the joint, which will cause the pressure to drop. Therefore, when the pressure maintenance ends, the pressure value fluctuates within the allowable range, and the leakage obtained is completely opposite to the actual leakage situation, which ultimately affects the test process of the component. At present, due to the limitations of production rhythm and product quantity in the actual production process of the project, the voltage stabilization time cannot be too long. This leads to a constant temperature difference between the gas in the pipeline and the external environment, resulting in unreliable test results and the need for continuous rework, resulting in the aviation pipeline airtightness test efficiency and test accuracy not meeting production requirements.

[0004] Therefore, in view of the above problems, the present invention develops a fast and accurate intelligent airtightness determination method that takes temperature into consideration based on the temperature sensor that monitors the temperature of the pipeline to be tested in the automatic airtightness test system. In the case of fluctuations in the ambient temperature of the factory, the relationship between the leakage of qualified pipelines and the temperature difference is statistically analyzed to characterize the pressure fluctuation caused by temperature changes, and a qualified temperature compensation reference curve is obtained to determine the airtightness of the pipeline to be tested. Through this method, the interference of the external environment is reduced, the influence of temperature on the test results is basically eliminated, the test accuracy and test efficiency are improved, and the problem of poor accuracy and low efficiency of aviation pipeline sealing tests is fundamentally solved. Summary of the invention

[0005] The purpose of the present invention is to provide a temperature-monitored aviation pipeline airtightness intelligent determination method to solve the problems of poor accuracy and low efficiency of aviation pipeline sealing test proposed in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: comprising the following steps:

[0007] S1: The air source of the factory is filtered through the air source triplex, and the air source pressure is increased to the applicable pressure through the booster valve. The air source triplex consists of a filter, a pressure reducing valve and a pressure gauge;

[0008] S2: The reversing valve is responsible for controlling the on / off of the lower test circuit and the exhaust when the test is completed, while the pressure reducing valve adjusts the pressure to the test pressure. The pressure sensor at the interface monitors the pressure in the pipeline to be tested in real time, and the temperature sensor monitors the temperature in the pipeline to be tested.

[0009] S3: Conduct air tightness test, connect the pipeline to be tested and set the test pressure, start filling the pipeline with gas, and when the pressure in the pipeline reaches the pressure required by the test, stop charging and enter the pressure stabilization stage. When the pressure in the pipeline is stable, enter the pressure holding stage;

[0010] S4: At the end of the pressure holding stage, read the pressure difference before and after the pressure holding, calculate the leakage, and compare the qualified temperature compensation reference curve with the temperature difference before and after the pressure holding. If it fails, repair it again until the test passes.

[0011] As a preferred technical solution of the present invention, during the airtightness test in step S3, assuming that the temperature change is ignored, according to Boyle's law, the gas pressure and volume under ideal conditions are inversely proportional, while the relationship between the leakage and the pressure difference under atmospheric conditions is:

[0012] P0-P1=P a Qt / V

[0013] Where: P0 is the pressure in the pipeline at the beginning of pressure holding, in MPa, P1 is the pressure in the pipeline at the end of pressure holding, in MPa, Pa is the atmospheric pressure, in MPa, V is the volume occupied by the gas in the pipeline, in L, Q is the leakage, in L / min.

[0014] As a preferred technical solution of the present invention, when the pipeline volume V is constant, the leakage is proportional to the pressure difference, and in the gas in the closed container, under its equilibrium state, there is an inverse relationship between the pressure and the temperature. Considering the actual pressure difference when the temperature changes, it is:

[0015]

[0016] Where: ΔT is the temperature difference of the gas in the pipeline at the beginning and end of pressure maintenance. When the test pressure is constant, the leakage is proportional to the temperature difference:

[0017] Q∝ΔT

[0018] Therefore, for a pipeline with a stable leakage point, the greater the temperature difference, the greater the measured leakage amount.

[0019] As a preferred technical solution of the present invention, the principle of the intelligent airtightness judgment method is: collect data from multiple groups of qualified pipelines, fit the temperature difference-leakage curve, and shift the curve upward by a certain distance (called the threshold) as a test qualified temperature compensation reference curve, which is used as a benchmark for subsequent tests.

[0020] As a preferred technical solution of the present invention, the specific method of the air tightness test in step S3 is: through the test of a large number of qualified pipelines, the leakage amount and the corresponding temperature difference of the qualified pipelines to be tested in the same batch are collected to form a leakage amount-temperature difference scatter plot, and the trend of the curve is observed. According to the piecewise linear regression method, the relationship between the leakage amount and the temperature difference is set as follows:

[0021]

[0022] Where: Q t is the leakage volume, in L / min, T t is the temperature difference in K, T t0 is the inflection point of the fitting curve; D t is a step function, β0, β1 and β2 are the parameters to be determined. The coordinates of each scattered point are (T(i), Q(i)). The error function is set to the error of the least squares method.

[0023]

[0024] Through repeated iterations, the error function is minimized and the inflection point T is obtained. t0, and β0, β1 and β2 are waiting for parameter calculation to obtain the nonlinear relationship between leakage and temperature difference. At the same time, half of the error E of the least square method is used as the threshold in the qualified test temperature compensation reference curve, and the temperature difference-leakage curve is translated upward to obtain the qualified test temperature compensation reference curve. The current test result (temperature difference-leakage) is compared with the temperature compensation reference curve. If the result is below the threshold, the test is qualified, reducing the misjudgment caused by temperature changes;

[0025] If the test is qualified, the data of the pipeline (temperature difference-leakage) will be automatically added to the qualified pipeline database, and the qualified test temperature compensation reference curve will be updated in real time to provide a more accurate reference for the next test.

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

[0027] 1. The present invention provides a temperature-monitored intelligent air tightness determination method for aviation pipelines. The host computer and PLC control each solenoid valve group according to a predetermined program. The automatic air tightness test under a safe pressure relies on a booster pump to increase the air source pressure of the plant. In order to prevent sudden failures from causing excessive pressure in the pipeline, an overflow valve is provided to limit the pressure in the pipeline to below a safe value. A 2-position 3-way reversing valve is used to realize the transition of the test state from pressurization and pressure maintenance during the test to pressure relief after the test is completed. A secondary pressure regulation is performed through a pressure reducing valve to make the outlet pressure reach the test requirement pressure. A high-precision pressure sensor and a temperature sensor are provided to monitor the pressure and temperature values ​​inside the pipeline in real time.

[0028] 2. The present invention provides a temperature monitoring aviation pipeline air tightness intelligent judgment method, using the linear relationship between temperature difference and leakage

[0029] Q∝ΔT

[0030] According to the existing test data, through the piecewise linear regression analysis method of the temperature difference-leakage data of qualified pipelines, it is assumed that the relationship between temperature difference and leakage is

[0031]

[0032] Substitute the temperature difference and leakage data of the existing qualified pipeline into the relationship, and through repeated iterations, find the values ​​of each parameter with the smallest zero least squares error E, and you can get the temperature difference leakage fitting curve, which more accurately represents the relationship between temperature difference and leakage. Then use E / 2 as the threshold, and correct the temperature difference-leakage curve by moving the threshold to establish a qualified temperature compensation reference curve. The test results obtained from each test are compared with the reference curve to determine whether it is qualified or not, thereby reducing the misjudgment caused by temperature changes during the airtight test. This method does not need to calculate the leakage change value caused by temperature changes. Through rapid statistical analysis of existing qualified test data, an efficient and high-precision airtight determination method is proposed.

[0033] 3. The present invention provides a temperature-monitored aviation pipeline airtightness intelligent determination method. During the determination process, the temperature difference-leakage of the current qualified pipeline is added to the existing database (temperature difference-leakage), and the qualified temperature compensation reference curve of the test is corrected through an intelligent real-time iterative algorithm. In this way, the reference curve obtained through repeated iterations eliminates the inaccurate fitting caused by the real-time dynamic changes in the factory temperature, which is conducive to the intelligent airtightness determination of large quantities of pipelines, provides a more credible dynamic test standard for the subsequent test, enhances the reliability of the test results, and is more in line with the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the temperature compensation principle diagram of the present invention;

[0035] Figure 2 The gas circuit principle and automatic control diagram of the present invention;

[0036] Figure 3 It is the air tightness test flow chart of the present invention.

[0037] Figure 4 This is a real-time temperature compensation flow chart of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figure 1-4 The present invention provides a technical solution for an intelligent method for determining the air tightness of aviation pipelines by temperature monitoring:

[0040] according to Figure 1-4 As shown, the following steps are included:

[0041] S1: The air source of the factory is filtered through the air source triplex, and the air source pressure is increased to the applicable pressure through the booster valve. The air source triplex consists of a filter, a pressure reducing valve and a pressure gauge;

[0042] S2: The reversing valve is responsible for controlling the on / off of the lower test circuit and the exhaust when the test is completed, while the pressure reducing valve adjusts the pressure to the test pressure. The pressure sensor at the interface monitors the pressure in the pipeline to be tested in real time, and the temperature sensor monitors the temperature in the pipeline to be tested. The reversing valve is a 2-position 3-way reversing valve.

[0043] S3: Conduct air tightness test, connect the pipeline to be tested and set the test pressure, start filling the pipeline with gas, and when the pressure in the pipeline reaches the pressure required by the test, stop charging and enter the pressure stabilization stage. When the pressure in the pipeline is stable, enter the pressure holding stage;

[0044] S4: At the end of the pressure holding stage, read the pressure difference before and after the pressure holding, calculate the leakage, and compare the qualified temperature compensation reference curve with the temperature difference before and after the pressure holding. If it fails, repair it again until the test passes.

[0045] During the airtight test in step S3, assuming that the temperature change is ignored, according to Boyle's law, the gas pressure is inversely proportional to the volume under ideal conditions, while the relationship between the leakage and the pressure difference under atmospheric conditions is:

[0046] P0-P1=P a Qt / V

[0047] Where: P0 is the pressure in the pipeline at the beginning of pressure holding, in MPa, P1 is the pressure in the pipeline at the end of pressure holding, in MPa, Pa is the atmospheric pressure, in MPa, V is the volume occupied by the gas in the pipeline, in L, Q is the leakage, in L / min.

[0048] When the pipeline volume V is constant, the leakage is proportional to the pressure difference. In the gas in a closed container, under its equilibrium state, there is an inverse relationship between pressure and temperature. The actual pressure difference when considering temperature changes is:

[0049]

[0050] Where: ΔT is the temperature difference of the gas in the pipeline at the beginning and end of pressure maintenance. When the test pressure is constant, the leakage is proportional to the temperature difference:

[0051] Q∝ΔT

[0052] Therefore, for a pipeline with a stable leakage point, the greater the temperature difference, the greater the measured leakage amount.

[0053] The principle of the intelligent air tightness judgment method is to collect data from multiple groups of qualified pipelines, fit the temperature difference-leakage curve, and shift the curve upward by a certain distance (called the threshold) as a reference curve for test qualified temperature compensation, which will be used as the benchmark for subsequent tests.

[0054] The specific method of the air tightness test in step S3 is: through the test of a large number of qualified pipelines, the leakage amount and the corresponding temperature difference of the qualified pipelines to be tested in the same batch are collected to form a leakage amount-temperature difference scatter plot, and the trend of the curve is observed. According to the piecewise linear regression method, the relationship between the leakage amount and the temperature difference is set as follows:

[0055]

[0056] Where: Q t is the leakage volume, in L / min, T t is the temperature difference in K, T t0 is the inflection point of the fitting curve; D t is a step function, β0, β1 and β2 are the parameters to be determined. The coordinates of each scattered point are (T(i), Q(i)). The error function is set to the error of the least squares method.

[0057]

[0058] Through repeated iterations, the error function is minimized and the inflection point T is obtained. t0 , and β0, β1 and β2 are waiting for parameter calculation to obtain the nonlinear relationship between leakage and temperature difference. At the same time, half of the error E of the least square method is used as the threshold in the qualified test temperature compensation reference curve, and the temperature difference-leakage curve is translated upward to obtain the qualified test temperature compensation reference curve. The current test result (temperature difference-leakage) is compared with the temperature compensation reference curve. If the result is below the threshold, the test is qualified, reducing the misjudgment caused by temperature changes;

[0059] If the test is qualified, the data of the pipeline (temperature difference-leakage) will be automatically added to the qualified pipeline database, and the qualified test temperature compensation reference curve will be updated in real time to provide a more accurate reference for the next test.

[0060] The intelligent judgment method for air tightness of aviation pipelines based on temperature monitoring takes into account the influence of the temperature difference before and after pressure maintenance on the final leakage. By arranging the temperature sensor at the interface of the airtight test system, the temperature compensation reference curve of the qualified test is determined by the piecewise linear regression analysis of the temperature difference-leakage of the qualified pipeline, and the intelligent judgment of the test result is completed. The test data of the current pipeline is added to the linear regression database, and the curve is updated in real time.

[0061] The present invention is further described below with reference to the accompanying drawings and examples.

[0062] like Figure 2 As shown, the airtight test system is connected to the plant gas source. The gas source triplex consisting of a filter, a pressure reducing valve and a pressure gauge filters and reduces the gas pressure in the first stage. Then, the gas passes through the reversing valve 1 and is increased to a suitable pressure by a booster pump. The overflow valve is used to prevent sudden failures from causing excessive pressure in the pipeline and limit the pressure in the pipeline to below a safe value. Then, the gas passes through the reversing valve and is subjected to secondary pressure regulation by the pressure reducing valve so that the outlet pressure reaches the test requirement pressure. The high-precision pressure sensor and temperature sensor are responsible for monitoring the pressure and temperature values ​​inside the pipeline to be tested.

[0063] Taking a batch of aviation fuel pipelines as an example, the intelligent airtightness determination process of temperature monitoring is as follows: Figure 3 and Figure 4 As shown:

[0064] 1) First, connect the airtight test system to the aviation fuel pipeline through a quick-connect connector, then set the test working pressure and open the corresponding valve to charge with compressed air;

[0065] 2) When the pressure sensor 2 detects that the pressure in the pipeline reaches the test pressure, close the valve and stop charging. Perform pressure stabilization for 20 minutes. During the pressure stabilization process, the pressure may fluctuate within the allowable range due to the influence of external vibrations;

[0066] 3) After the pressure stabilization is completed, enter the pressure holding stage and record the pressure and temperature values ​​in the pipeline at the beginning of the pressure holding. After standing for 30 minutes, record the pressure and temperature values ​​at the end of the pressure holding and calculate the corresponding leakage.

[0067] 4) By performing a piecewise linear regression analysis on the database of relevant test results (temperature difference-leakage) of the batch of qualified aviation fuel system pipelines, the temperature difference-leakage fitting curve and the least squares error E0 are obtained. Taking E0 / 2 as the threshold, the temperature difference-leakage fitting curve is moved upward by E0 / 2 to obtain the qualified temperature compensation reference curve;

[0068] 5) The leakage amount calculated in 3) is compared with the corrected test qualified temperature compensation reference curve. If it is below the curve, the test is qualified; if it is above the curve, the test is unqualified.

[0069] 6) The temperature difference-leakage data obtained from the pipeline test is added to the database used for linear regression, and the qualified temperature compensation reference curve is tested in real time, waiting for the next round of testing.

[0070] 7) The test is completed.

[0071] In the description of the present invention, it is necessary to understand that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention 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 cannot be understood as a limitation on the present invention.

[0072] In the present invention, unless otherwise clearly stipulated and limited, for example, it can be a fixed connection, a detachable connection, or an integrated one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, for ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0073] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A temperature-monitored intelligent method for determining air tightness of aviation pipelines, characterized in that: The following steps are involved: S1: The air source of the factory is filtered through the air source triplex, and the air source pressure is increased to the applicable pressure through the booster valve. The air source triplex consists of a filter, a pressure reducing valve and a pressure gauge; S2: The reversing valve is responsible for controlling the on / off of the lower test circuit and the exhaust when the test is completed, while the pressure reducing valve adjusts the pressure to the test pressure. The pressure sensor at the interface monitors the pressure in the pipeline to be tested in real time, and the temperature sensor monitors the temperature in the pipeline to be tested. The reversing valve is a 2-position 3-way reversing valve. S3: Conduct air tightness test, connect the pipeline to be tested and set the test pressure, start filling the pipeline with gas, and when the pressure in the pipeline reaches the pressure required by the test, stop charging and enter the pressure stabilization stage. When the pressure in the pipeline is stable, enter the pressure holding stage; S4: At the end of the pressure holding stage, read the pressure difference before and after the pressure holding, calculate the leakage, and compare the qualified temperature compensation reference curve with the temperature difference before and after the pressure holding. If it fails, repair it again until the test is qualified; The specific method of the air tightness test in step S3 is: through the test of a large number of qualified pipelines, the leakage amount and the corresponding temperature difference of the same batch of qualified pipelines to be tested are collected to form a leakage amount-temperature difference scatter plot, and the trend of the curve is observed. According to the piecewise linear regression method, the relationship between the leakage amount and the temperature difference is set as follows: Where: Q t is the leakage volume, in L / min, T t is the temperature difference in K, T t0 is the inflection point of the fitting curve; D t is a step function, β0, β1 and β2 are the parameters to be determined. The scatter point coordinates of the leakage-temperature difference scatter plot are: (T(i), Q(i)), T(i) is the temperature at the i-th moment, Q(i) is the leakage at the i-th moment, and the calculated value Q(Ti) of the leakage at the i-th moment is compared with the measured value Qi of the leakage at the i-th moment to establish the least squares error function Through repeated iterations, the error function is minimized and the inflection point T is obtained. t0 , and β0, β1 and β2 are waiting for parameter calculation to obtain the nonlinear relationship between leakage and temperature difference. At the same time, half of the error E of the least square method is used as the threshold in the qualified test temperature compensation reference curve, and the temperature difference-leakage curve is translated upward to obtain the qualified test temperature compensation reference curve. The current test result is compared with the temperature compensation reference curve. If the result is below the threshold, the test is qualified, reducing the misjudgment caused by temperature changes; If the test is qualified, the data of the pipeline will be automatically added to the qualified pipeline database, and the qualified test temperature compensation reference curve will be updated in real time to provide a more accurate reference for the next test.

2. According to claim 1, the method for intelligently determining the air tightness of aviation pipelines by temperature monitoring is characterized in that: During the airtight test in step S3, assuming that the temperature change is ignored, according to Boyle's law, the gas pressure and volume under ideal conditions are inversely proportional, while the relationship between the leakage and the pressure difference under atmospheric conditions is: P0-P1=P a Qt / V Where: P0 is the pressure in the pipeline at the beginning of pressure holding, in MPa, P1 is the pressure in the pipeline at the end of pressure holding, in MPa, Pa is the atmospheric pressure, in MPa, V is the volume occupied by the gas in the pipeline, in L, Q is the leakage, in L / min.

3. The method for intelligently determining the air tightness of aviation pipelines by temperature monitoring according to claim 2 is characterized in that: When the pipeline volume V is constant, the leakage is proportional to the pressure difference. In the gas in the closed container, under the equilibrium state, there is an inverse relationship between the pressure and the temperature. The actual pressure difference when considering the temperature change is: Where: ΔT is the temperature difference of the gas in the pipeline at the beginning and end of pressure maintenance. When the test pressure is constant, the leakage is proportional to the temperature difference: Q∝ΔT Therefore, for a pipeline with a stable leakage point, the greater the temperature difference, the greater the measured leakage amount.

4. The method for intelligently determining the air tightness of aviation pipelines by temperature monitoring according to claim 1 is characterized in that: The principle of the intelligent air tightness determination method is: collect data from multiple groups of qualified pipelines, fit the temperature difference-leakage curve, shift the curve upward, and the shift distance is the threshold value, which is used as the test qualified temperature compensation reference curve, and the subsequent tests are based on it.

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