A high-precision air leakage meter comparison system and method

Abstract

The present invention relates to the field of engine performance measurement and analysis, and specifically to a high-precision air leakage meter comparison system and method. The system includes a laminar flow device, an air leakage meter, a variable frequency fan, a temperature and pressure acquisition module, a frequency converter, a comparison system, an air path connecting pipe, an intake air temperature sensor, an atmospheric pressure sensor, and a pressure difference sensor. The method of the present invention has strong adaptability and large practical use requirements, and can meet the comparison of air leakage meters of various ranges. It is convenient to carry out comparison activities, the flow rate of the comparison test point is stable, and the measured value fluctuates little during the comparison process, avoiding the measurement dispersion caused by the flow fluctuation problem caused by using the engine as the gas power source; the comparison activity can be carried out at any time without any waiting. The flow rate of the variable frequency air pump is adjustable, which can cover the test requirements of the air leakage of different engine types.

Description

Technical Field

[0001] The present invention relates to the field of engine performance measurement and analysis, and in particular to a comparison system and method for instruments for measuring engine crankcase blowby. Background Art

[0002] When the engine is undergoing an air leakage performance test on a test bench, an air leakage meter test equipment is required. Long-term use of the instrument may result in inaccurate measurement values, and the accuracy of the air leakage meter needs to be checked regularly. The existing inspection method in the test bench is to connect a standard air leakage meter and the existing air leakage meter on the test bench to the same engine on the test bench. When the engine is running under the same working conditions, the measurement value deviation of the two air leakage meters is compared to see if it is within the required range.

[0003] The current comparison method suffers from the drawbacks of using an engine airflow source for comparison, which can lead to large measurement variations due to fluctuations in engine airflow. Furthermore, using a standard air leakage meter with the same accuracy results in limited accuracy. Furthermore, maximum air leakage values ​​vary between engine models, so a comparison using a single engine cannot cover the required measurement range for all models. Because the normal maximum air leakage of an engine is typically at its power point, the engine must be running at high speed and load for comparison. Therefore, the engine must be warmed up before each comparison, which is time-consuming. Summary of the Invention

[0004] The present invention provides a high-precision air leakage meter comparison system and method that can quickly and regularly verify the accuracy of the measuring instrument with high precision when used on an engine test bench, thereby reducing the annual cost of outsourcing air leakage meter calibration. The specific technical solution is as follows:

[0005] A high-precision air leakage meter comparison system includes a laminar flow device, an air leakage meter, a variable frequency fan, a temperature and pressure acquisition module, a frequency converter, a comparison system, an air path connecting pipe, an intake air temperature sensor, an atmospheric pressure sensor, and a pressure difference sensor; the comparison air leakage meter is connected and installed between the laminar flow device and the variable frequency fan via the air path connecting pipe; the variable frequency fan is arranged at the rear end of the system to generate suction, so that the air flow enters from the inlet of the laminar flow device, passes through the laminar flow device, the air leakage meter, and the variable frequency pump in sequence, and is discharged at the end of the pipeline; the comparison system is in signal communication with the air leakage meter, the temperature and pressure acquisition module, and the frequency converter respectively.

[0006] The intake air temperature sensor and the atmospheric pressure sensor are installed at the inlet of the laminar flow device, and the differential pressure sensor is installed at both ends of the laminar flow device, and both are connected to the temperature and pressure acquisition module; the frequency converter is connected to the variable frequency fan; the comparison system can adjust the speed of the variable frequency fan through the frequency converter.

[0007] Utilizing the comparison method of the aforementioned high-precision air leakage meter comparison system, the intake air temperature TL and pressure P of the laminar flow device are measured by an intake air temperature sensor and an atmospheric pressure sensor, and the pressure difference ΔP across the laminar flow device is measured by a differential pressure sensor. The pressure difference ΔP is input into the comparison system via a temperature and pressure acquisition module. The gas flow rate Q1 measured by the air leakage meter is input into the comparison system. The comparison system includes a signal output module and comparison software. The signal input module receives the TL, P, and ΔP outputs from the temperature and pressure acquisition module, and the flow rate Q1 output from the air leakage meter. The comparison software of the comparison system calculates the flow rate Q through the laminar flow device.

[0008] The comparison system calculates the gas flow Q using the following formula:

[0009] Q=ΔP*KTL*60*P / 101.3*293.16 / (273.16+TL)(L / min)......................①

[0010] Where: KTL = K20*(380+TL) / 400*(293.16 / (273.16+TL))^3 / 2(L / sec)

[0011] K20=A*(1-BΔP)

[0012] Where: K20 is the flow coefficient of the laminar flow device under standard conditions, which is calculated by comparing with the constant coefficients A and B obtained by standard flow meter and the pressure difference ΔP; KTL is the flow coefficient of the laminar flow device at the current temperature TL;

[0013] The comparison system compares Q and Q1 and calculates the deviation, determines whether the deviation between Q1 and Q is within the qualified range, and obtains the correction coefficient of the point.

[0014] Furthermore, the comparison system inputs the correction coefficient to the air leakage meter through the signal output module so that the air leakage meter can measure more accurately within the flow range.

[0015] Furthermore, the comparison system outputs different target frequencies to the frequency converter through the signal output module, so that the variable frequency fan produces different flow rates. The comparison software determines whether the comparison results of different flow points are qualified and obtains the correction coefficient of each point. The comparison system inputs the correction coefficient of different points to the leakage meter, making the flow test of the leakage meter more accurate in various measuring ranges.

[0016] The method of the present invention has strong adaptability and great practical use demand, and can meet the comparison of leakage meters of various ranges. It is convenient to carry out comparison activities, and can be moved to any test bench for comparison testing. The flow rate at the comparison test point is stable, and the measured value fluctuates little during the comparison process, avoiding the measurement dispersion caused by the flow fluctuation problem caused by using the engine as the gas power source. The comparison result of the leakage meter with the higher-precision LFE is more accurate. Comparison activities can be carried out at any time without any waiting. The flow rate of the variable frequency air pump is adjustable, which can cover the leakage test requirements of different engine types. The engine test laboratory can save the test costs caused by the engine operation during each comparison, as well as the equipment outsourcing appraisal costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 System device diagram of the present invention.

[0018] Figure numerals: 1, laminar flow device 2, air leakage meter 3, variable frequency fan 4, temperature and pressure acquisition module 5, frequency converter 6, comparison system 7, air path connecting pipe 8, intake air temperature sensor 9, atmospheric pressure sensor 10, differential pressure sensor. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0020] The system device of the present invention is as follows Figure 1 As shown:

[0021] A high-precision air leakage meter comparison system includes a laminar flow device 1, an air leakage meter 2, a variable frequency fan 3, a temperature and pressure acquisition module 4, a frequency converter 5, a comparison system 6, an air path connecting pipe 7, an intake air temperature sensor 8, an atmospheric pressure sensor 9, and a pressure differential sensor 10; the comparison air leakage meter 2 is connected and installed between the laminar flow device 1 and the variable frequency pump 3 via the air path connecting pipe 7; the variable frequency pump 3 is arranged at the rear end of the system to generate suction, so that the air flow enters from the inlet of the laminar flow device, passes through the laminar flow device 1, the air leakage meter 2, and the variable frequency pump 3 in sequence, and is discharged at the end of the pipeline; the comparison system 6 is in signal communication with the air leakage meter 2, the temperature and pressure acquisition module 4, and the frequency converter 5 respectively;

[0022] The intake air temperature sensor 8 and the atmospheric pressure sensor 9 are installed at the inlet of the laminar flow device 1, and the pressure difference sensor 10 is installed at both ends of the laminar flow device 1, and both are connected to the temperature and pressure acquisition module 4; the frequency converter 5 is connected to the variable frequency fan 3; the comparison system 6 can adjust the speed of the variable frequency fan 3 through the frequency converter 5.

[0023] The working principle is:

[0024] According to the laminar gas flow calculation formula:

[0025]

[0026] Where: r, L are the radius and length of the laminar flow element, is the dynamic viscosity coefficient of the fluid at the measurement temperature. Since π, r, and L are constants, ΔP is the pressure difference across the laminar flow device.

[0027] If K=1 / (8L)*πr^4, then This shows that the laminar flow rate is proportional to the pressure difference between the two ends of the fluid flowing into it. Because the radius inside the laminar flow device is difficult to measure, we can calibrate it with a standard flow meter to obtain the flow coefficient and calculation formula of this laminar flow device.

[0028] By comparing data with a standard flow meter at a temperature of 20 degrees Celsius and a standard atmospheric pressure for many times, a calculation formula for the air flow rate under standard conditions through the laminar flow device of this method is obtained by fitting and calculation.

[0029] Q=ΔP*KTL*60*P / 101.3*293.16 / (273.16+TL)(L / min)......................①

[0030] Where: KTL = K20*(380+TL) / 400*(293.16 / (273.16+TL))^3 / 2(L / sec)

[0031] K20=A*(1-BΔP)

[0032] Where: K20 is the flow coefficient of the laminar flow device under standard conditions, which is calculated by comparing the constant coefficients A and B obtained with the standard flow meter and the pressure difference ΔP.

[0033] KTL is the flow coefficient of the laminar flow device at the current temperature TL.

[0034] The comparison method is as follows: Utilize a variable-frequency blower 3 as an airflow source generator, generating stable airflows of varying flow rates. Variable-frequency blower 3 extracts air at the rear end of the entire device. The front end of variable-frequency blower 3 is connected via an air pipe to the leakage meter 2 to be compared. The front end of leakage meter 2 is then connected via a pipe to laminar flow device 1. Variable-frequency blower 3 is activated, and air flows in through the inlet of laminar flow device 1, passing through both laminar flow device 1 and leakage meter 2. The leakage meter's measured value, Q1, is compared with the value Q calculated by the laminar flow device using formula ① integrated into the comparison system to determine the comparison result. The comparison is performed to determine whether the deviation is within the acceptable range. Furthermore, the comparison software determines the correction factor for the leakage meter at the current flow rate.

[0035] The comparison system includes a signal input and output module and comparison software. A temperature sensor 8 and a pressure sensor 9 are installed at the front end of the laminar flow device 1, and differential pressure sensors 10 are installed at both ends. The temperature and pressure acquisition module 4 collects the pressure difference ΔP across the two ends of the laminar flow device, the temperature TL of the inlet gas, and the atmospheric pressure P. The temperature and pressure acquisition module inputs these signals to the comparison software through the analog input and output module. The comparison system combines the constant coefficients A and B of the laminar flow device and calculates the flow rate Q through the laminar flow device. Q and Q1 are compared and the deviation is calculated to determine whether the deviation between Q1 and Q is within the qualified range and the correction coefficient for that point.

[0036] The comparison system 6 inputs the correction coefficients to the leakage meter 2 via the signal output module, ensuring more accurate measurements within the specified flow range. The comparison system 6 outputs different target frequencies to the frequency converter 5 via the signal output module, causing the variable-frequency blower 3 to generate different flow rates. The comparison software determines the eligibility of the comparison results at different flow points and determines the correction coefficients for each point. The comparison system inputs the correction coefficients at each point to the leakage meter 2, ensuring more accurate flow measurements within each flow range.

[0037] The above describes in detail the preferred embodiments of this patent, but this patent is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of this patent.

Claims

1. A comparison method using a high-precision air leakage meter comparison system, characterized by: The high-precision air leakage meter comparison system comprises a laminar flow device (1), an air leakage meter (2), a variable frequency fan (3), a temperature and pressure acquisition module (4), a frequency converter (5), a comparison system (6), an air path connecting pipe (7), an air intake temperature sensor (8), an atmospheric pressure sensor (9), and a pressure difference sensor (10); the air leakage meter (2) is connected to and installed between the laminar flow device (1) and the variable frequency fan (3) through the air path connecting pipe (7); the variable frequency fan (3) is arranged at the rear end of the system to generate suction force, so that the air flow enters from the inlet of the laminar flow device, passes through the laminar flow device (1), the air leakage meter (2), and the variable frequency fan (3) in sequence, and then is discharged at the end of the pipeline; the comparison system (6) is in signal communication with the air leakage meter (2), the temperature and pressure acquisition module (4), and the frequency converter (5) respectively; The inlet air temperature sensor (8) and the atmospheric pressure sensor (9) are installed at the inlet of the laminar flow device (1), and the differential pressure sensor (10) is installed at both ends of the laminar flow device (1), and both are connected to the temperature and pressure acquisition module (4); the frequency converter (5) is connected to the variable frequency fan (3); the comparison system (6) can adjust the speed of the variable frequency fan (3) through the frequency converter (5); The intake air temperature TL and pressure P of the laminar flow device (1) are measured by an intake air temperature sensor (8) and an atmospheric pressure sensor (9); the pressure difference ΔP at both ends of the laminar flow device (1) is measured by a differential pressure sensor (10), and is input into a comparison system (6) through a temperature and pressure acquisition module (4); the gas flow rate Q1 measured by the leakage meter is input into the comparison system (6); the comparison system (6) includes a signal output module and comparison software, the signal input module receiving TL, P, ΔP output by the temperature and pressure acquisition module (4), and the flow rate Q1 output by the leakage meter; the comparison software of the comparison system (6) calculates the flow rate Q passing through the laminar flow device (1); The comparison system (6) calculates the gas flow rate Q using the following formula: Q=ΔP*KTL*60*P / 101.3*293.16 / (273.16+TL) (L / min).............① Where: KTL = K20*(380+TL) / 400*(293.16 / (273.16+TL))^3 / 2(L / sec) K20=A*(1-BΔP) Where: K20 is the flow coefficient of the laminar flow device under standard conditions, which is calculated by comparing with the constant coefficients A and B obtained by standard flow meter and the pressure difference ΔP; KTL is the flow coefficient of the laminar flow device at the current inlet temperature TL; The comparison system (6) compares Q and Q1 and calculates the deviation, determines whether the deviation between Q1 and Q is within the qualified range, and obtains the correction coefficient of the current flow rate down-leakage meter.

2. The method according to claim 1, wherein: The comparison system (6) inputs the correction coefficient to the air leakage meter (2) through the signal output module, so that the air leakage meter can measure more accurately within the flow range.

3. The method according to claim 1, wherein: The comparison system (6) outputs different target frequencies to the frequency converter (5) through the signal output module so that the variable frequency fan generates different flow rates. The comparison software determines whether the comparison results of different flow points are qualified and obtains the correction coefficient of each point. The comparison system inputs the correction coefficients of different points into the air leakage meter (2), so that the flow rate test of the air leakage meter (2) in each measuring range is more accurate.

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