Method for determining air leakage of a system within a specific flow range

Abstract

This application discloses a method for determining system air leakage within a specific flow range, comprising the following steps: Step S1: After assembling the experimental platform, seal all openings and measure the system air leakage under a preset experimental pressure difference; Step S2: Seal all test holes on the end face of the pressure stabilizing box; Step S3: According to the experimental design, adjust the various single factors in the experimental platform and conduct the experiment, measuring the pressure difference and flow rate Q under each single factor experimental condition. total Data; Step S4: Calculate the system leakage ratio r under different experimental conditions, with the relative measurement error δ of the specimen leakage as the horizontal axis; Step S5: Plot the error variation curve under each single-factor experimental condition, with the system leakage ratio r as the horizontal axis and the relative measurement error δ of the specimen leakage as the vertical axis, and fit the error curve. This method can quantitatively analyze the system leakage value and improve the accuracy of the actual leakage measurement results of the specimen.

Description

Technical Field

[0001] This application relates to the field of air leakage detection technology, and in particular to a method for determining the air leakage of a system within a specific flow range. Background Technology

[0002] The functionality of a building's smoke control and exhaust system relies on the air leakage performance of smoke control and exhaust products such as fire dampers and smoke curtains. Current industry standards impose mandatory constraints on the air leakage of building smoke control and exhaust systems: Currently, relevant national standards for fire protection and smoke control, as well as building airtightness testing, all set mandatory limits on the system's air leakage. The mainstream specifications require the following: 1. Fire dampers for building ventilation and smoke exhaust systems (GB 15930): System air leakage not exceeding 25m³. 3 / (m 2 •h) If the standard is exceeded, the sealing of all connection parts of the equipment needs to be rectified; 2. Fireproof Roller Shutters - Part 1: General Technical Requirements (GB14102.1-2024): Smoke leakage of the curtain system ≤ 5m³ 3 / h, if the value exceeds the standard, the equipment seal needs to be adjusted; 3. Smoke curtain (XF533): System smoke leakage ≤ 5m³ 3 / h, if the limit is not met, the sealing structure of the enclosure and pipeline needs to be optimized; However, existing standard limits lack systematic experimental support and theoretical basis. At the same time, existing research mostly focuses on the overall air tightness of buildings, the air leakage of large air ducts, the accuracy of flow meter components and the comparison of measurement methods, while there is little systematic research on the impact of the size of the system air leakage on the accuracy of actual air leakage measurement in product air leakage detection.

[0003] The existing basic formula for calculating air leakage is: Q test =Q total -Q sys ; ; In the formula: Q total To measure the total leakage air volume in the pressure stabilizing box, m 3 / h;Q sys The inherent air leakage of the system, measured under fully sealed conditions, is expressed in m. 3 / h;Q test To calculate the air leakage of the specimen, m 3 / h; S For the area of ​​the specimen, m 2 Q v To calculate the air leakage per unit area of ​​the specimen, m 3 / (m 2 h); Absolute pressure inside the P pipeline, ( ), Pa; Pn Standard atmospheric pressure, 101325 Pa; T represents the thermodynamic temperature of the gas inside the pipe (K, T = t + 273.15, where t is the measured medium temperature (°C)); T n (293.15K (20℃)); Q n The calculated air leakage rate per unit area of ​​the specimen under standard conditions is expressed in Nm³. 3 / (m 2 h).

[0004] The air leakage rate obtained from the above formula has the following problems: 1. The system's air leakage cannot be actively adjusted; only the Q value under a fixed, sealed state can be measured. sys It is impossible to obtain the test results of the adjustable system air leakage gradient, and it is impossible to conduct a system air leakage control test. 2. The structural parameters of the test system are not adjustable. The pressure measurement points, system air leakage points, and fan flow conditions cannot be changed individually, making it difficult to obtain the interference results of a single variable on the measurement accuracy. 3. There is no supporting accuracy analysis method. It can only output the raw flow rate value and cannot automatically calculate the system leakage ratio, absolute error, and relative uncertainty, so it cannot complete the quantitative evaluation of measurement accuracy.

[0005] The information disclosed in the background section is intended only to enhance understanding of the overall background of the invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This application addresses the aforementioned technical problem by providing a method for determining system air leakage within a specific flow range. This method can quantitatively analyze the accuracy of the system air leakage value relative to the actual air leakage measurement results of the test specimen. It is applicable to the verification and index optimization of fire protection and other air leakage detection standards for fire valves, fire-resistant roller shutters, smoke curtains, building exterior doors and windows, fire-resistant components of ventilation ducts, etc.

[0007] This application provides a method for determining system air leakage within a specific flow range, including the following steps: Step S1: After assembling the experimental platform, seal all openings and measure the system air leakage Q under the preset experimental pressure difference. sys_0 ; Step S2: Seal all test holes on the end face of the pressure stabilizing box, install ball valves on the side wall of the pressure stabilizing box, open and lock the operating frequency of the variable frequency fan to maintain the differential pressure gauge reading, and adjust the opening of the ball valve to obtain the system air leakage Q that meets the experimental requirements. sys Maintain the pressure stabilizing box at the system air leakage rate Q sys Then, start the first measurement of the aperture required for this experiment. iAfter the test well is completed and all readings on the platform have stabilized for 3 minutes, the reading of the air flow meter at this time is recorded as the first reading. i Measured air leakage at the test hole Q total_i ; Calculate the first i Simulated air leakage at the test orifice Q test_i =Q total_i - Q sys Simultaneously calculate the first i Air leakage per unit area Q of the test hole v_1 =Q test_i / S i ; Step S3: Based on the experimental design, adjust the various single factors in the experimental platform and conduct the experiment, measuring the pressure difference and flow rate Q under each single factor experimental condition. total data; Step S4: Calculate the air leakage Q of the test hole under different experiments using the following formula. test Q test =Q total -Q sys In the formula: Q total The total leakage air volume of pressure stabilizing box 9 was measured under different experimental conditions; Q sys This refers to the inherent air leakage of the system measured under fully sealed conditions. The absolute error of the actual air leakage was calculated. ∆Q Absolute error of air leakage per unit area ∆q The relative measurement error δ and the system leakage ratio r are expressed as follows: ∆Q=Q j −Q avg ∆q=q j −q avg ； ;

[0008] In the formula: Q avg The arithmetic mean of the air leakage per unit area measured under the same operating conditions represents the actual leakage level under that operating condition, in Nm³. 3 / h; ∆Q The absolute error of the actual air leakage is expressed in Nm. 3 / h; ∆q The absolute error of air leakage per unit area is expressed in Nm. 3 / (m 2 ·h); δ L Characterizing the measurement discrepancy caused by specific operating conditions; Q jq represents the simulated air leakage measured in the j-th measurement. j Let J be the air leakage per unit area measured in the j-th time. Step S5: Plot the error variation curve under each single-factor experimental condition with the system leakage ratio r as the horizontal axis and the relative measurement error δ of the specimen leakage as the vertical axis. Fit the error curve to obtain δ=ar b In the formula, a and b are fitting coefficients; let δ=5%, solve for the leakage ratio r of the critical system, and based on the leakage ratio r of the critical system, calculate the leakage amount Q' of the critical system. sys The relationship between r is: , In the formula, Q test The reference value is the true value, which is the average value of the measured air leakage under the test hole diameter; Calculate the air leakage rate Q' of the critical system sys， Based on the critical system air leakage threshold Q' sys The system air leakage Q of the experimental platform under the experimental conditions was adjusted. sys to below the critical system leakage threshold Q' sys Then, return to step S3 to conduct the experiment under this factor to improve the accuracy of the air leakage measurement results of the test holes obtained from each single-factor experiment.

[0009] Preferably, the components include an air flow meter, a differential pressure gauge, a pressure stabilizing box, a ball valve, and a test port. The air outlet of the variable frequency fan is sealed and connected to one end of the voltage regulator box through a straight flow stabilizing pipe section; Temperature transmitters, differential pressure transmitters, and air flow meters are installed at intervals on the straight pipe section for steady flow. Mounting holes for ball valves and differential pressure gauges are provided on each side of the pressure stabilizing box, and test holes are opened on the opposite end face of the pressure stabilizing box and the straight pipe section of the flow stabilizing system.

[0010] Preferably, the experimental platform includes: a variable diameter connector; the variable frequency fan and the steady flow straight pipe section are smoothly connected through the variable diameter connector.

[0011] Preferably, the experimental platform includes: a control data acquisition unit; the control data acquisition unit is connected to the variable frequency fan, temperature transmitter, differential pressure transmitter, air flow meter, and differential pressure gauge respectively.

[0012] Preferably, the steady-flow straight pipe section includes two interconnected sections: an upstream straight pipe section and a downstream straight pipe section; the upstream straight pipe section and the downstream straight pipe section are respectively connected to both ends of the air flow meter; the length of the upstream straight pipe section is ≥15D, and the length of the downstream straight pipe section is ≥5D, where D is the inner diameter of the steady-flow straight pipe section.

[0013] Preferably, step S1 includes the following steps: Step S11: After assembling the experimental platform, seal all mounting holes and experimental holes on the voltage regulator box; Step S12: Turn on the variable frequency fan and preset the test pressure difference in the pressure stabilizing box to ensure that the airflow in the steady flow straight pipe section and the pressure stabilizing box is fully stable. After maintaining the pressure difference unchanged for 3 minutes, collect the total leakage air volume of the pressure stabilizing box through the air flow meter as the system leakage air volume Q. sys_0 ; Step S13: Synchronously collect the temperature and static pressure parameters in the steady-flow straight pipe section under this condition, complete the standard flow conversion, and measure the total flow measurement error ∆T. In the formula: ∆A is the accuracy of the vortex flow meter; ∆B is the accuracy of the differential pressure transmitter; ∆C is the accuracy of the temperature transmitter.

[0014] Preferably, a test hole with a diameter d=0~8.46mm is opened on the end face of the voltage regulator box to simulate a small leakage. Test holes with a diameter d = 8.46~48.52mm are opened on the end face of the voltage stabilizer box to simulate leakage. Test holes with a diameter of d=48.52~61.9mm are opened on the end face of the voltage regulator box to simulate large leakage.

[0015] Preferably, after each adjustment of the opening of ball valve 10, wait for the system air leakage condition to remain stable for 2 minutes before simultaneously collecting various system parameters P. i ; Three parallel tests were repeated under each operating condition, and the system parameter P was recorded. i The arithmetic mean is then calculated and stored in the database of the control data acquisition unit.

[0016] Preferably, the single-factor experiments in step S3 include: pressure gauge parameter test, system air leakage location test, and fan operating condition test; The pressure measuring tube parameter test includes the following steps: Replace the pressure measuring tubes of the air flow meter with tubes of different lengths, and adjust the insertion depth of the pressure measuring tubes into the steady-flow straight pipe section as follows: 0mm from the wall surface, 125mm from the lower wall surface, 250mm from the center of the chamber, and 375mm from the lower wall surface. Then, collect the pressure difference and total air leakage Q of the experimental platform at each depth. total data; The system leakage location test includes the following steps: Ball valves used to simulate system leakage are installed on the remaining mounting holes of the pressure stabilizing box, and the total leakage Q of the experimental platform is collected at different positions and gradient openings of the ball valves. total Differential pressure data; The differential pressure test includes the following steps: Within a preset gradient range, the differential pressure in the pressure stabilizing box is adjusted to the preset gradient range by adjusting the operating frequency of the variable frequency fan, and the total air leakage Q is collected under each differential pressure. total Differential pressure data.

[0017] The beneficial effects that this application can produce include: 1) The method for determining system air leakage within a specific flow range provided in this application allows for gradient and controllable adjustment of the system air leakage value. It also supports multi-parameter adjustment of the pressure measurement structure, leakage location, and fan operating conditions, enabling rigorous single-variable control experiments. A complete error propagation and accurate quantification calculation system is established, quantitatively obtaining the correlation between system air leakage, system air leakage ratio, and specimen air leakage measurement error. Four major interference variables—pressure measuring tube length, pressure measuring depth, system air leakage installation location, and differential pressure range—are separated, and their impact on measurement accuracy is quantified individually. This provides standardized experimental verification basis for system air leakage limits in current national standards for fire protection and building airtightness testing, supporting standard revision and limit optimization. A repeatable and standardized system air leakage impact verification test operation procedure is formed, unifying the industry's airtightness testing equipment error verification test specifications. Attached Figure Description

[0018] Figure 1 A three-dimensional structural schematic diagram of the apparatus used in the method for determining system air leakage within a specific flow range in at least one embodiment of this application; Figure 2 A schematic photograph of the apparatus used in the method for determining system air leakage within a specific flow range in at least one embodiment of this application; a is an end-side photograph; b is a perspective photograph. Figure 3 The experimental results of the test hole of the specimen in at least one embodiment provided in this application are shown in Figure a; a is the curve of the actual air leakage and air leakage per unit area of ​​the specimen with the preset hole diameter under different system air leakage values; b is the curve of the absolute error of the actual air leakage and the absolute error of the air leakage per unit area of ​​the specimen. Figure 4 A schematic diagram of the module connection for measuring the influence of system air leakage on the accuracy of actual air leakage in at least one embodiment provided in this application; Figure 5 Grouped bar chart of relative error in unit area leakage measurement of specimens with different aperture sizes in at least one embodiment provided in this application under 4 levels of system leakage rate; Figure 6 A graph showing the relative error of different test hole diameters versus the percentage of system air leakage, obtained in at least one embodiment provided in this application. Legend: 1. Variable frequency fan; 2. Variable diameter connector; 3. Flow-stabilizing straight pipe section; 4. Temperature transmitter; 5. Differential pressure transmitter; 6. Air flow meter; 7. PLC control box; 8. Differential pressure gauge; 9. Pressure stabilizing box; 10. Ball valve; 11. Test hole; 31. Upstream straight pipe section; 32. Downstream straight pipe section; 111. Control data acquisition unit. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] Technical means not detailed in this application and not used to solve the technical problems of this application are all set according to common general knowledge in the field, and multiple common general knowledge setting methods can be implemented.

[0022] See Figures 1-6 This application provides a method for determining system air leakage within a specific flow range. The apparatus used in this method includes: a variable frequency fan 1, a variable diameter connector 2, a straight pipe section for steady flow 3, a temperature transmitter 4, a differential pressure transmitter 5, an air flow meter 6, a PLC control box 7, a differential pressure gauge 8, a pressure stabilizing box 9, a ball valve 10, and a test hole; in this application, the test hole 11 is a test hole on the end face, and the leakage of the test piece is adjusted by adjusting the hole diameter.

[0023] A variable diameter connector 2 is installed at the air inlet of the variable frequency fan 1; a steady flow straight pipe section 3 is installed at the air inlet end of the variable diameter connector 2; a temperature transmitter 4, a differential pressure transmitter 5, and an air flow meter 6 are installed sequentially on the steady flow straight pipe section 3; a pressure stabilizing box 9 is sealed and connected to the end of the steady flow straight pipe section 3; a differential pressure gauge 8 is installed on the pressure stabilizing box 9; a ball valve 10 is installed on one side wall of the pressure stabilizing box 9, which is used to simulate the system leakage; multiple test holes of different diameters are set on the opposite end face of the end face of the pressure stabilizing box 9 connected to the steady flow straight pipe section 3, which are used to simulate the leakage to be measured. The PLC control box 7 is equipped with a control data acquisition unit 111. The control data acquisition unit 111 is electrically connected to the variable frequency fan 1, temperature transmitter 4, differential pressure transmitter 5, air flow meter 6, and differential pressure gauge 8, respectively. It is used to collect various airflow data in the steady flow straight pipe section 3 during the experiment, as well as the data required by the variable frequency fan 1. At the same time, it realizes the functions of differential pressure closed-loop stable control of the pressure stabilizing box 9 and automatic acquisition and storage of multi-sensor data. The control data acquisition unit 111 has a built-in error quantification calculation program to obtain various error data in real time.

[0024] In one specific embodiment, the diameter d1 of the first cross-section of the variable diameter connector 2 connected to the variable frequency fan 1 is larger than the diameter d2 of the second cross-section connected to the stable flow straight pipe section 3; the first cross-section and the second cross-section are connected by a tapered structure with a gradually narrowing inner diameter, so as to achieve a smooth transition between the outlet of the variable frequency fan 1 and the stable flow straight pipe section 3 by using the variable diameter connector 2, thereby reducing the airflow turbulence disturbance in the stable flow straight pipe section 3 and ensuring that the internal flow field of the stable flow straight pipe section 3 is uniform and stable; In one specific embodiment, when the wind force of the variable frequency fan 1 is relatively small, the diameter d1 of the first section of the variable diameter connector 2 connected to the variable frequency fan 1 is smaller than the diameter d2 of the second section connected to the stable flow straight pipe section 3; the first section and the second section are connected by a tapered structure with a gradually narrowing inner diameter, so as to achieve a smooth transition between the outlet of the variable frequency fan 1 and the stable flow straight pipe section 3 by using the variable diameter connector 2, thereby reducing the airflow turbulence disturbance in the stable flow straight pipe section 3 and ensuring that the internal flow field of the stable flow straight pipe section 3 is uniform and stable.

[0025] The variable frequency fan 1 is used to provide a stable negative pressure air source, and the internal pressure difference of the pressure stabilizing box 9 is precisely controlled by adjusting the operating frequency; the steady flow straight pipe section 3 includes two interconnected sections: upstream straight pipe section 31 and downstream straight pipe section 32; the upstream straight pipe section 31 and downstream straight pipe section 32 are separated by the air flow meter 6; the length of the upstream straight pipe section 31 is ≥15D, and the length of the downstream straight pipe section 32 is ≥5D, where D is the inner diameter of the steady flow straight pipe section 3; this installation can eliminate the interference of airflow vortices on the measurement accuracy of the air flow meter 6 and improve the accuracy of the measurement results; Temperature transmitter 4 and differential pressure transmitter 5 are used to collect the temperature and static pressure parameters of the flowing gas in the steady-flow straight pipe section 3 in real time. The obtained parameters are used to convert the operating flow rate into the standard flow rate. Air flow meter 6 collects the total standard leakage air volume in the steady-flow straight pipe section 3. Differential pressure gauge 8 is used to monitor the pressure difference between the inside of the pressure stabilizing box 9 and the external environment in real time, so as to maintain the standard pressure difference set in the test, such as the standard pressure difference requirement of fire valve is (-300±15) Pa. The pressure stabilizing chamber 9 serves as a sealed pressure-bearing cavity, providing a unified pressure stabilizing environment for specimen leakage and system simulation leakage. The side walls and bottom surface of the pressure stabilizing chamber 9 (the specific opening positions are set according to experimental needs) are reserved with multiple sets of standardized threaded mounting holes, which are used to assemble ball valves 10 with different opening degrees required for the experiment. Multiple ball valves 10 can be installed on the side wall of the pressure stabilizing box 9. Each ball valve 10 can be individually adjusted in opening degree and replaced with different orifice end caps, thereby realizing the controllable generation gradient change of the inherent air leakage of the system in the laboratory. The ball valves 10 can be replaced and installed on different walls of the pressure stabilizing box 9 for carrying out system air leakage location comparison tests.

[0026] The test holes are holes of different diameters opened on the end face of the pressure stabilizing box to simulate the air leakage of different test pieces. In the initial stage of testing, each test hole can be sealed with the end cap, and test holes of additional diameters can be opened as needed in subsequent experiments.

[0027] The pressure stabilizing box 9 can be equipped with multiple test holes of different diameters according to experimental needs. The sealing of each installation hole can be achieved by opening a multi-specification standard opening plug end cap on the side wall of the pressure stabilizing box 9. When the experiment is required, test holes of different diameters can be quickly replaced to simulate test holes of three different leakage levels: large, medium and small, covering the leakage range of all types of products such as building doors and windows, fire dampers, roller shutters and smoke curtains.

[0028] In one specific embodiment, the selected temperature transmitter has a measurement accuracy of 1%, the differential pressure transmitter has a measurement accuracy of 0.5%, and the air flow meter 6 has a flow measurement accuracy of 1%.

[0029] The use of this application Q v To calculate the air leakage per unit area of ​​the specimen, m 3 / (m 2 h); P is the absolute pressure inside the pipe (P=P 表 +P 大气压 ), Pa; P n Standard atmospheric pressure, 101325 Pa; T is the thermodynamic temperature of the gas inside the pipe, K, T = t + 273.15, where t is the measured temperature of the medium (°C); T n =293.15K (20℃); Q n The calculated air leakage rate per unit area of ​​the specimen under standard conditions is expressed in Nm³. 3 / (m 2 h). All leakage per unit area used below are calculated using the above formula, where the actual leakage per unit area Q of the test specimen is used as the reference. v Converted to air leakage per unit area under standard conditions Q n Compare them.

[0030] The method includes the following steps: Step S1: After assembling the experimental platform, measure the system air leakage Q under fully sealed conditions. sys_0 : Assemble the test platform according to the aforementioned structure. Seal all openings (including ball valve mounting holes and test holes 11) of the pressure stabilizing box 9 with solid plugs to cut off the artificially simulated leakage channel. Control the data acquisition unit 111 to start the variable frequency fan 1 and adjust the frequency of the variable frequency fan 1 to draw the pressure stabilizing box 9 to the preset test pressure difference, specifically to draw it to negative pressure, so that the pressure difference measured in real time in the pressure stabilizing box 9 stabilizes to the standard test pressure difference (e.g., -300Pa), ensuring that the airflow in the steady flow straight pipe section 3 and the pressure stabilizing box 9 is fully stable. After maintaining the pressure difference unchanged for 3 minutes, collect the total leakage air volume of the pressure stabilizing box 9 through the air flow meter 6. This value is the system leakage air volume Q under the zero additional leakage state. sys_0 ; Simultaneously, temperature and static pressure parameters within the steady-flow straight pipe section 3 are collected under this condition. Standard flow rate conversion is completed, and the total flow measurement error ∆T is measured. Based on the uncertainty propagation law (i.e., the root sum of squares method), the formula for calculating the total flow measurement error ∆T of this measurement system is as follows: In the formula: ∆A is the accuracy of the vortex flow meter; ∆B is the accuracy of the differential pressure transmitter; ∆C is the accuracy of the temperature transmitter; substituting each component into the above formula, we get: ∆T = 1.12%, which is used as the error correction benchmark for subsequent tests.

[0031] Step S2: Core control test of air leakage rate of gradient system with fixed specimens Test holes 11 of various diameters are made on the end face of the sealed pressure stabilizing box 9. A ball valve 10 is installed at the first position of the ball valve mounting hole on the side wall of the pressure stabilizing box 9, that is, at the position closest to the end face of the pressure stabilizing box 9. The operating frequency of the variable frequency fan 1 is locked to maintain the reading of the differential pressure gauge 8. After adjusting the opening degree of the ball valve 10, the system air leakage Q that meets the experimental requirements is obtained. sys Maintain the pressure stabilizing box 9 at the system air leakage rate Q sys After opening the end cap of the experimental hole 11 (to be measured) according to experimental needs, and waiting for all readings to stabilize for 3 minutes, read the reading of the air flow meter 6 at this time, as the result. i Measured air leakage at test hole 11 Q total_i ;No. i Simulated air leakage at test hole 11 Q test_i =Q total_i - Q sys Simultaneously calculate the first i The air leakage per unit area Q of test hole 11 v_1 =Q test_i / S i .

[0032] In one specific embodiment, during the test, after each adjustment of the ball valve 10 opening degree or other parameters, the system air leakage condition is stabilized for 3 minutes, and various system parameters are collected synchronously. Each set of conditions is repeated 3 times in parallel, and the arithmetic mean of each system parameter is stored in the database of the control data acquisition unit 111.

[0033] In one specific embodiment, the aperture d of the test hole 11 is adjusted according to experimental needs to effectively simulate specimens with different leakage rates and obtain gradient system leakage parameters for test holes with different apertures. Test holes (11) with aperture d=0~8.46mm are opened on the end face of the pressure stabilizing box (9) to simulate small leakage; test holes (11) with aperture d=8.46~48.52mm are opened on the end face of the pressure stabilizing box (9) to simulate medium leakage; test holes (11) with aperture d=48.52~61.9mm are opened on the end face of the pressure stabilizing box (9) to simulate large leakage, thereby realizing gradient system leakage control test of full-scale specimens.

[0034] Step S3: Separation and Control Experiment with Multiple Confounding Variables By changing only a single variable each time while keeping all other experimental parameters constant, this method can be used to individually decompose the interference of each factor on measurement accuracy. Pressure measuring tube parameter test: Replace the pressure measuring tubes of air flow meters 6 with different lengths, and adjust the insertion depth of the pressure measuring tubes into the steady flow straight pipe section 3 as follows: 0mm from the wall surface, 125mm from the lower wall surface, 250mm from the center of the chamber, and 375mm from the lower wall surface. Then, collect the pressure difference and total air leakage Q of the experimental platform at each depth. total data; System air leakage location test: Ball valves 10, used to simulate system air leakage, were installed on the side wall and bottom of the pressure stabilizing box 9, respectively. The total air leakage Q of the experimental platform was collected at different positions and gradient openings of ball valves 10. total Differential pressure data; pre-set mounting holes for ball valve 10 at corresponding installation positions. Select ball valve 10 with an opening degree that meets the experimental requirements based on the experiment.

[0035] Differential pressure test: By adjusting the operating frequency of the variable frequency fan 1, the differential pressure in the pressure stabilizing box 9 is adjusted to a preset gradient range, and the total air leakage Q is collected under each differential pressure. total The results of the experiment are shown in the table below: When the diameter of the experimental hole 11 was measured to be 0 mm, 8.46 mm, and 48.52 mm, the total air leakage was measured after adjusting the operating frequency of the variable frequency fan 1 to control the pressure difference to the required gradient range for the experiment. Table 1

[0036] Step S4: Measurement accuracy quantitative analysis includes the following steps: Step S41: Calculate the air leakage Q of experimental hole 11 under different experiments using the following formula. test Q test =Q total -Q sys In the formula: Q total The total leakage air volume was measured for pressure stabilizing box 9 under different experimental conditions; Q sys This refers to the inherent air leakage of the system measured under fully sealed conditions. Step S42: Calculate the absolute error of the actual air leakage. ∆Q Absolute error of air leakage per unit area ∆q The relative measurement error δ and the system leakage ratio r are expressed as follows: ∆Q=Q j −Q avg ∆q=q j −q avg ； ; ; In the formula: Q avg The arithmetic mean of the air leakage per unit area measured under the same operating conditions represents the actual leakage level under that operating condition, in Nm³. 3 / h; ∆Q The absolute error of the actual air leakage is expressed in Nm. 3 / h; ∆q The absolute error of air leakage per unit area is expressed in Nm. 3 / (m 2 ·h); δ L Characterizing the measurement discrepancy caused by specific operating conditions; Q j q represents the simulated air leakage measured in the j-th measurement. j Let be the air leakage per unit area measured in the j-th measurement.

[0037] The system leakage ratio r under different experimental conditions indicates that the larger the value of r, the stronger the error amplification effect of system leakage fluctuation on the test specimen leakage measurement results under that experimental condition. The system leakage ratio r is the proportion of system leakage to total leakage.

[0038] Step S5: Summarize experimental data and output conclusions on standard application Step S51: Under each factor experiment, plot the error variation curve of the k-th experiment for the l-th factor, with the system leakage ratio r obtained from the experiment as the horizontal axis and the relative measurement error δ of the specimen leakage as the vertical axis; in one embodiment, the results obtained from the differential pressure test are as follows: Figure 6 As shown.

[0039] Step S52: Based on the obtained error variation curve, and after performing linear fitting on the error variation curve, δ=ar is obtained. b In the formula, a and b are fitting coefficients; let δ=5%, solve for the leakage ratio r of the critical system, and based on the leakage ratio r of the critical system, calculate the leakage amount Q' of the critical system. sys The relationship between r is: , In the formula, Q test The baseline value is the average value of the measured air leakage under the test orifice diameter; the critical system air leakage Q' is then calculated. sys Based on the critical system air leakage threshold Q' sys The system air leakage Q of the device under the experimental conditions was adjusted. sys to below the critical system leakage threshold Q' sys Then, experiments under this factor are conducted to avoid the results exceeding the industry's acceptable accuracy by 5% due to excessive system air leakage, thereby improving the accuracy of the air leakage measurement results of the specimens obtained from each single-factor experiment. In one specific embodiment, the results obtained in the experiment measuring experimental orifices 11 with different aperture sizes are as follows: Figure 6 As shown in the figure, when the diameter of experimental hole 11 is 8.46 mm, δ exceeds the industry-acceptable accuracy by 5%. This is confirmed by curve fitting. Let δ = 5%, then solve for the leakage ratio of the critical system. That is, the leakage rate r of the critical system is 68.2%. Based on the leakage rate r of the critical system, the leakage amount Q' of the critical system is calculated. sys Derivation: , Deformation: The reference true value of test hole 11 for a specimen with a hole diameter of 8.46 mm. The average value of the measured air leakage under this test hole diameter is substituted into the calculation: For detecting minor leaks in fire dampers, the inherent air leakage of the system must be adjusted to below 8.36 Nm. 3 Only by maintaining a value of / h can we ensure that r < 68.2%, and only then can we guarantee that the relative measurement error δ remains stable within the 5% acceptable range.

[0040] Step S53: Based on the curve pattern, provide requirements for the sealing rectification of testing equipment and suggestions for optimizing national standard limits, providing quantitative test data support for the revision of airtightness testing standards. Example

[0041] 1. Test platform assembly and overall calibration 1.1 Piping Assembly: Taking the circular ventilation valves specified in GB 15930-2024 as the object, with a nominal area range of 0.01131~3.14159 m², the true value of the product's air leakage is calculated according to the standard's judgment criterion of 300 Nm³ / (m²·h) per unit area at ambient temperature (pressure difference -300±15 Pa). The system air leakage is taken as the upper limit of the standard, 25 Nm³ / h. Therefore, the total air leakage range (including system air leakage) that the flow meter needs to measure is (3.39+25)~(942.48+25) Nm³ / h.

[0042] Connect the variable frequency fan 1, the reducing connection 2, and the flow stabilizing pipe section 3 in sequence according to the airflow direction. Install the temperature transmitter 4, the differential pressure transmitter 5, and the air flow meter 6 in sequence at the straight pipe section of the flow stabilizing pipe section 3. Strictly ensure that the length of the upstream straight pipe section 31 is ≥15D and the length of the downstream straight pipe section 32 is ≥5D. Seal the end of the flow stabilizing pipe section 3 and connect it to the pressure stabilizing box 9. Wrap all flange and threaded connection positions with sealing tape to reduce the air leakage Qsys of the equipment system. 1.2 Assemble the pressure stabilizing box 9: The box body has multiple wall surfaces with mounting holes for ball valves 10, test holes for specimens, and mounting interfaces for differential pressure gauges 8 measuring tubes. Various sizes of regulating ball valves 10, end caps for test holes with different diameters, and differential pressure gauges 8 measuring tubes with adjustable depth are assembled thereon. 1.3 Electrical System Assembly: The signal lines of temperature transmitter 4, differential pressure transmitter 5, air flow meter 6, and differential pressure gauge 8 are connected to the control data acquisition unit 111 in the PLC control box. The communication port of variable frequency fan 1 is interconnected with the control data acquisition unit 111 to complete the differential pressure and flow closed-loop control debugging of pressure stabilizing box 9; air flow meter 6 is a vortex flow meter. 1.4 Overall Accuracy Calculation: The accuracy of the vortex flowmeter in the measurement system is 1.0%, the accuracy of differential pressure transmitter 5 is 0.1%, and the accuracy of temperature transmitter 4 is 0.5%. Since the above three error components are independent and uncorrelated, based on the uncertainty propagation law (i.e., the root sum of squares method), the formula for calculating the total flow measurement error ∆T of this measurement system is as follows: In the formula: ∆A is the accuracy of the vortex flow meter; ∆B is the accuracy of the differential pressure transmitter; ∆C is the accuracy of the temperature transmitter; substituting each component into the above formula, we get: ∆T=1.12%. This result meets the requirement of "not exceeding ±2.5%" for flow measurement accuracy in GB15930-2024 standard, indicating that the combined expanded uncertainty of this measurement system is within an acceptable range.

[0043] 2. Complete test implementation example (GB 15930 Fireproof valves - 300Pa standard differential pressure condition) The experimental platform assembled above was used to study the impact of different system leakage values ​​on the accuracy of the actual product leakage. Based on the actual fan pressure, air volume capacity, and pressure loss of the measuring pipeline, four levels of system leakage Q were preset. sys =15.1, 43.9, 84.8, 117.9 Nm 3 / h, using 5 standard leakage orifice diameters (8.46, 27.8, 48.52, 55.4, 61.9 mm) to simulate different air leakage rates of fire damper specimens, the specific experimental procedure is as follows: Measuring system air leakage includes the following steps: 1. Seal all test holes 11 of the assembled experimental platform. Turn on the variable frequency fan 1. The differential pressure gauge 8 reading should be within (-300±15 Pa). At this time, the system air leakage Q should be measured by the air flow meter 6. sys_0 The reading was 5.2 Nm. 3 / h; 2. After shutting down the variable frequency fan 1, install ball valve 10 on the side wall hole of the pressure stabilizing box 9 near the end face of the test hole 11. Turn on the variable frequency fan 1. The differential pressure gauge 8 reading should be within (-300±15 Pa). Adjust the opening of ball valve 10 until the system leakage rate measured by air flow meter 6 is 15.1 Nm. 3 / h; The air leakage of the remaining systems is Q. sys =43.9, 84.8, 117.9 Nm 3 / h, obtain and maintain the above operation, and replace the ball valve according to the required system air leakage. For example, if the required system air leakage is large, replace it with a ball valve with a larger opening.

[0044] The simulated air leakage measurement process for each orifice diameter test hole 11 is as follows: 1. After maintaining the system air leakage, open the i-th test hole 11. Adjust the variable frequency fan 1 to keep the reading of the differential pressure gauge 8 within -300±15 Pa. After all values ​​have stabilized for 3 minutes, proceed to the next step. 2. Read the reading of air flow meter 6 at this time, as the first... i Measured air leakage at test hole 11 Q total_i ;No. i Simulated air leakage at test hole 11 Q test_i =Q total_i - Q sys The apertures of each test well (i=4) are shown in the table below. The actual experimental conditions are shown in the table below; simultaneously, the apertures of the first test well (i=4) are calculated. i The air leakage per unit area Q of test hole 11 v_1 =Qtest_i / S i .

[0045] Table 2 Experimental Conditions

[0046] After measuring 5-6 times at each setting, the arithmetic mean Q of the air leakage per unit area of ​​the i-th test hole 11 is calculated using the following formula. avg_i , , n=5~6; where S i_j Let be the area of ​​the i-th test hole 11; The simulated air leakage was measured for the j-th time for the i-th test hole 11, and the results of the measured data are listed in the table below.

[0047] Table 3

[0048] The absolute error of the actual air leakage was calculated. ∆Q Absolute error of air leakage per unit area ∆q The relative measurement error δ and the system leakage ratio r are expressed as follows: ∆Q=Q j −Q avg ; ∆q=q j −q avg ； ； ； In the formula: Q avg The arithmetic mean of the air leakage per unit area measured under the same operating conditions represents the actual leakage level under that operating condition, in Nm³. 3 / h; ∆Q The absolute error of the actual air leakage is expressed in Nm. 3 / h; ∆q The absolute error of air leakage per unit area is expressed in Nm. 3 / (m 2 ·h); δ L Characterizing the measurement discrepancy caused by specific operating conditions; Q j q represents the simulated air leakage measured in the j-th measurement. j Let be the air leakage per unit area measured in the j-th measurement.

[0049] Substituting the values ​​into the above formulas, we can calculate the system leakage ratio r and the relative measurement error δ. L The experimental results are shown in [reference]. Figure 3 a and b. Figure 3Figure 'a' shows the curves of actual air leakage and air leakage per unit area of ​​the specimen as a function of the preset orifice diameter under different system air leakage values. As can be seen from the curves, the measured air leakage of the specimen increases synchronously with the increase of the corresponding orifice diameter from 8.46 mm to 55.4 mm. Let Q... sys =15.1 Nm 3 Taking the / h operating condition as an example, the actual air leakage of the specimen is 3.6 Nm 3 / h increased to 108.3 Nm 3 / h; however, the air leakage per unit area generally decreases as the orifice diameter increases, with an 8.46 mm orifice diameter resulting in an air leakage of 64075.52 Nm³ per unit area. 3 / (m 2 The aperture size (·h) decreased from 55.4 mm to 44950.99 Nm. 3 / (m 2 (·h). Under the same orifice diameter, the measured leakage rates of the four systems showed dispersion. The dispersion was most significant for the 8.46 mm orifice diameter: the actual measured leakage rate ranged from 3.6 to 4.2 Nm. 3 / h; while the actual measured air leakage range for a 55.4mm orifice is 105.5~110.3 Nm. 3 / h, the data dispersion is significantly reduced.

[0050] Figure 3 b represents the absolute error of the actual air leakage of the specimen and the absolute error of the air leakage per unit area. The data shows that the absolute error of the actual air leakage for an 8.46mm orifice is only 0.20~0.30 Nm. 3 / h, the deviation between the maximum and minimum values ​​is 0.6 Nm 3 / h, relative deviation 12%; absolute error per unit area 3559.75~5339.63 Nm 3 / (m 2 (h), the difference between the maximum and minimum values ​​reaches 10679.25 Nm. 3 / (m 2 •h), relative deviation exceeds 15%; maximum absolute error of 55.4 mm aperture is 0.15~2.95 Nm 3 / h, absolute error per unit area 64.33~1218.2 Nm 3 / (m 2 It can be seen that as the specimen aperture increases, the absolute error of the measured air leakage increases while the absolute error per unit area decreases. However, the fire damper standard uses the air leakage per unit area as the criterion. Therefore, when the specimen size and area are small, the system air leakage has a significant impact on its deviation.

[0051] Figure 5 Grouped bar charts showing the relative error of unit area leakage rate measurement for specimens with different aperture sizes under four system leakage rate settings; through... Figure 5 It can be seen that with an 8.46 mm orifice diameter, the system leakage rate is 80.75%~96.56%, and the relative measurement error is higher than 5.13% for all cases, reaching a maximum of 7.69%. With an orifice diameter of 27.8 mm, the system leakage rate is 29.55%~75.67%, and the relative measurement error decreases to 0.34%~2.77%. For orifice diameters of 48.52 mm and 55.4 mm, the system leakage rate is as low as 12.24%, and the relative error for all operating conditions is lower than 2.71%. Among them, the relative error for an orifice diameter of 61.9 mm is only 0.06%. pass Figure 5 Data shows that under a standard pressure difference of (-300±15) Pa, the smaller the leakage orifice diameter of the specimen, the higher the proportion of system leakage to total leakage, and the greater the relative measurement error. The maximum relative error reaches 7.69% under the 8.46 mm micro-leakage condition, while the error can be controlled within 3% under the medium-to-large orifice diameter condition of 55.4 mm and above. An 80% system leakage rate is the critical threshold for abrupt error change; exceeding this value leads to a sharp increase in error, while falling below it results in a significant improvement in measurement accuracy. This threshold can serve as a key reference for designing testing schemes and setting limits. Figure 5 The data shows that when the system leakage rate r approaches 97%, the relative measurement error δ of the small-diameter specimen increases sharply, indicating that the measurement results are severely distorted under these conditions. 4. The above operations are controlled by the data acquisition unit 111.

[0052] The current national standard for collecting test data is 25m. 3 / (m 2 h) The system leakage limit can meet the testing accuracy requirements of most airtight products; if the system leakage rate r exceeds 90%, the measurement data of small leakage specimens will be completely distorted. It is necessary to strengthen the sealing structure of the testing equipment pipeline and housing to reduce the system leakage rate r to below 50% before relevant testing experiments can be carried out.

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining system air leakage within a specific flow range, characterized in that, Includes the following steps: Step S1: After assembling the experimental platform, seal all openings and measure the system air leakage Q under the preset experimental pressure difference. sys_0 ; Step S2: Seal all test holes (11) on the end face of the pressure stabilizing box (9), install ball valves (10) on the side wall of the pressure stabilizing box (9), turn on and lock the operating frequency of the variable frequency fan (1) to maintain the reading of the differential pressure gauge (8), and adjust the opening degree of the ball valve (10) to obtain the system leakage Q that meets the experimental requirements. sys Maintain the pressure stabilizing box (9) at the system air leakage rate Q sys Then, start the first measurement of the aperture required for this experiment. i After the test hole (11) and all readings of the platform have stabilized for 3 minutes, the reading of the air flow meter (6) at this time is taken as the first reading. i Measured air leakage at test hole (11) Q total_i ; Calculate the first i Simulated air leakage at test hole (11) Q test_i =Q total_i - Q sys Simultaneously calculate the first i The air leakage per unit area Q of the test hole (11) v_1 =Q test_i / S i ; Step S3: Based on the experimental design, adjust the various single factors in the experimental platform and conduct the experiment, measuring the pressure difference and flow rate Q under each single factor experimental condition. total data; Step S4: Calculate the air leakage Q of the experimental hole (11) under different experiments using the following formula. test Q test =Q total -Q sys In the formula: Q total The total leakage air volume was measured for pressure stabilizing box 9 under different experimental conditions; Q sys This refers to the inherent air leakage of the system measured under fully sealed conditions. The absolute error of the actual air leakage was calculated. ∆Q Absolute error of air leakage per unit area ∆q The relative measurement error δ and the system leakage ratio r are expressed as follows: ∆Q=Q j −Q avg ∆q=q j −q avg ； ; In the formula: Q avg The arithmetic mean of the air leakage per unit area measured under the same operating conditions represents the actual leakage level under that operating condition, in Nm³. 3 / h; ∆Q The absolute error of the actual air leakage is expressed in Nm. 3 / h; ∆q The absolute error of air leakage per unit area is expressed in Nm. 3 / (m 2 ·h); δ L Characterizing the measurement discrepancy caused by specific operating conditions; Q j q represents the simulated air leakage measured in the j-th measurement. j Let J be the air leakage per unit area measured in the j-th time. Step S5: Plot the error variation curve under each single-factor experimental condition with the system leakage ratio r as the horizontal axis and the relative measurement error δ of the specimen leakage as the vertical axis. Fit the error curve to obtain δ=ar b In the formula, a and b are fitting coefficients; let δ=5%, solve for the leakage ratio r of the critical system, and based on the leakage ratio r of the critical system, calculate the leakage amount Q' of the critical system. sys The relationship between r is: , In the formula, Q test The reference true value is the average value of the measured air leakage under the diameter of the test hole (11); Calculate the air leakage rate Q' of the critical system sys， Based on the critical system air leakage threshold Q' sys The system air leakage Q of the experimental platform under the experimental conditions was adjusted. sys to below the critical system leakage threshold Q' sys Then, return to step S3 to conduct the experiment under this factor to improve the accuracy of the air leakage measurement results of the test hole (11) obtained from each single factor experiment.

2. The method for determining system air leakage within a specific flow range according to claim 1, characterized in that, The experimental platform includes: a variable frequency fan (1), a steady flow straight pipe section (3), a temperature transmitter (4), a differential pressure transmitter (5), an air flow meter (6), a differential pressure gauge (8), a pressure stabilizing box (9), a ball valve (10), and a test port (11). The outlet of the variable frequency fan (1) is sealed and connected to one end of the voltage regulator box (9) through a straight flow stabilizing pipe section (3); Temperature transmitters (4), differential pressure transmitters (5), and air flow meters (6) are installed at intervals on the straight pipe section (3) for steady flow. The pressure stabilizing box (9) is provided with mounting holes for installing ball valve (10) and differential pressure gauge (8) on each side. The test hole (11) is opened on the opposite end face of the pressure stabilizing box (9) and the straight pipe section (3) of the flow stabilizing pipe.

3. The method for determining system air leakage within a specific flow range according to claim 2, characterized in that, The experimental platform includes: a variable diameter connector (2); a variable frequency fan (1); and a steady flow straight pipe section (3) which are smoothly connected through the variable diameter connector (2).

4. The method for determining system air leakage within a specific flow range according to claim 2, characterized in that, The experimental platform includes: a control data acquisition unit (11); the control data acquisition unit (11) is connected to the variable frequency fan (1), temperature transmitter (4), differential pressure transmitter (5), air flow meter (6), and differential pressure gauge (8), respectively.

5. The method for determining system air leakage within a specific flow range according to claim 2, characterized in that, The steady flow straight pipe section (3) includes the following interconnected sections: upstream straight pipe section (31) and downstream straight pipe section (32); the upstream straight pipe section (31) and downstream straight pipe section (32) are respectively connected to both ends of the air flow meter (6); The length of the upstream straight pipe section (31) is ≥15D, and the length of the downstream straight pipe section (32) is ≥5D, where D is the inner diameter of the steady flow straight pipe section (3).

6. The method for determining system air leakage within a specific flow range according to claim 2, characterized in that, Step S1 includes the following steps: Step S11: After assembling the experimental platform, seal all mounting holes and experimental holes (11) on the voltage regulator box (9). Step S12: Turn on the variable frequency fan (1) and preset the test pressure difference in the pressure stabilizing box (9) to ensure that the airflow in the steady flow straight pipe section (3) and the pressure stabilizing box (9) is sufficiently stable. After maintaining the pressure difference unchanged for 3 minutes, collect the total leakage air volume of the pressure stabilizing box (9) through the air flow meter (6) as the system leakage air volume Q. sys_0 ; Step S13: Synchronously collect the temperature and static pressure parameters in the steady-flow straight pipe section (3) under this condition, complete the standard flow conversion, and measure the total flow measurement error ∆T. In the formula: ∆A is the accuracy of the vortex flow meter; ∆B is the accuracy of the differential pressure transmitter; ∆C is the accuracy of the temperature transmitter.

7. The method for determining system air leakage within a specific flow range according to claim 2, characterized in that, Test holes (11) with a diameter d=0~8.46mm are opened on the end face of the voltage regulator (9) to simulate small leakage; Test holes (11) with a diameter d = 8.46~48.52 mm are opened on the end face of the pressure stabilizing box (9) to simulate the leakage amount; Test holes (11) with a diameter d = 48.52~61.9mm are opened on the end face of the voltage stabilizer (9) to simulate large leakage.

8. The method for determining system air leakage within a specific flow range according to claim 7, characterized in that, After each adjustment of the opening of ball valve 10 (10), wait for the system air leakage condition to remain stable for 2 minutes, and then simultaneously collect various system parameters P. i ; Three parallel tests were repeated under each operating condition, and the system parameter P was recorded. i After taking the arithmetic mean, it is stored in the database of the control data acquisition unit (111).

9. The method for determining system air leakage within a specific flow range according to claim 7, characterized in that, The single-factor experiments in step S3 include: pressure gauge parameter test, system air leakage location test, and fan operating condition test; The pressure measuring tube parameter test includes the following steps: Replace the pressure measuring tubes of the air flow meter (6) with different lengths, and adjust the insertion depth of the pressure measuring tubes into the steady flow straight pipe section (3) as follows: 0mm from the wall surface, 125mm from the lower wall surface, 250mm from the center of the box, and 375mm from the lower wall surface. Then, collect the pressure difference and total air leakage Q of the experimental platform at each depth. total data; The system leakage location test includes the following steps: ball valves (10) used to simulate system leakage are installed on the remaining mounting holes of the pressure stabilizing box (9), and the total leakage Q of the experimental platform is collected at different positions and gradient openings of the ball valves (10). total Differential pressure data; The differential pressure test includes the following steps: Within a preset gradient range, the operating frequency of the variable frequency fan (1) is adjusted to adjust the differential pressure inside the pressure stabilizing box (9) to the preset gradient range, and the total air leakage Q under each differential pressure is collected. total Differential pressure data.

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