Method for testing performance of airbag inflator based on acceleration sensor

Abstract

The application discloses a kind of based on acceleration sensor's automobile safety air bag gas generator performance test method, utilize rigid container, piston, high-speed camera, refrigeration type infrared thermal imager, pressure sensor, acceleration sensor, data recording device;Through the linear motion of piston, indirectly measure the energy that air bag gas generator combustion converts into gas kinetic energy, through the temperature change of gas and air bag gas generator metal shell, indirectly measure the energy that air bag gas generator combustion converts into gas internal energy and converts into air bag gas generator metal shell internal energy, and obtain effective work ratio, and can monitor whether the test process produces flaming and the highest gas temperature around air bag gas generator inflation hole.The present application has reliable theoretical basis, convenient operation, accurate measurement result, provides the test and solution method of multiple-dimension air bag gas generator performance evaluation index, and provides certain technical support for actual research and production.

Description

Technical Field

[0001] This invention relates to the field of automotive passive safety, and in particular to a method for testing the performance of automotive airbag gas generators based on an acceleration sensor. Background Technology

[0002] With the rapid development of the automotive industry in various countries, the number of car models and vehicles on the market is increasing. Based on road safety and consumers' growing emphasis on safety, the China New Car Assessment Program (C-NCAP) and the China Insurance Automotive Safety Index (C-IASI) have been adjusting the passive crash test conditions for automobiles year by year, raising the evaluation standards for crash performance. For example, in recent years, frontal 50% overlap vehicle-to-vehicle collision (MPDB), right-side 25% overlap small offset collision (SORB), and side pole impact have been added, improving the quality of the collision barrier and the collision speed. This has placed increasingly higher demands on the area protected by car airbags and their performance.

[0003] Automotive airbags primarily consist of a gas generator and an airbag. The gas generator, a core component of the airbag, mainly comprises an ignition agent, a gas-generating agent, and a metal filter. The igniter ignites the ignition agent, which releases heat. The gas-generating agent undergoes a violent chemical reaction, producing gases such as nitrogen. The metal filter filters out any remaining agent residue, and the gas enters the airbag through the inflation port. The gas generator largely determines whether the airbag performance meets the requirements of protecting occupants from hard contact with the vehicle body structure after a collision. Therefore, the performance design and testing of the airbag gas generator are crucial during the component development stage.

[0004] Existing methods for testing and evaluating the performance of gas generators involve a closed combustion chamber test (Tank test) where the gas generator is detonated within a sealed, rigid container. A pressure-time (pt) curve is then obtained using a pressure sensor. This yields the maximum pressure of the gas released after ignition and the time required to reach that maximum pressure. However, this traditional Tank test only extracts pt curve information, which has limitations in meeting increasingly stringent automotive crash safety standards.

[0005] Patent application number 200520104200.8 discloses a performance testing device for an airbag gas generator, capable of testing the pressure-time curve, temperature, composition and concentration of the gas produced after ignition, as well as the composition and content of solid residue after combustion. This technical solution uses a temperature sensor to collect temperature data throughout the testing process; however, its sensitivity and sampling frequency are difficult to achieve at the millisecond level, resulting in significant errors in the test results. Furthermore, the measured performance parameters are limited, making it difficult to comprehensively evaluate the performance of the airbag gas generator.

[0006] Patent application number 201610586401.9 discloses a performance testing device for airbag gas generators, which can realize the rapid opening and closing of the canister lid of the testing device, improving the convenience of existing testing devices, but its essence is still based on existing testing and evaluation methods and devices.

[0007] Patent application number 202021296314.8 discloses a test pressure device for airbag gas generators, which solves the problems of existing airbag gas generator test devices being unable to effectively fix the tested product and the inconvenience of moving the airbag gas generator test device; however, it only improves the ease of operation of the existing test device. Summary of the Invention

[0008] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides a performance testing method for automotive airbag gas generators based on an acceleration sensor. This method can measure the kinetic energy, internal energy, total energy, gas pressure, and their dynamic changes after the airbag gas generator is ignited, derive the percentage of effective work, and record indicators such as whether an open flame is generated during the test and the highest gas temperature around the airbag gas generator's inflation port. This provides an evaluation method for the research and development and production of actual airbag gas generators.

[0009] Technical solution: The present invention provides a method for testing the performance of an automotive airbag gas generator based on an acceleration sensor, comprising the following steps:

[0010] Step S1: Set up the test device; the test device includes a rigid container, a piston, a high-speed camera, and a cooled infrared thermal imager; the rigid container is a hollow cylinder, and an airbag gas generator is fixed at the bottom of the rigid container. The piston is located inside the rigid container and is a hemispherical shell with the opening facing downwards. A pressure sensor and an acceleration sensor are set at the center of the top of the piston. The high-speed camera and the cooled infrared thermal imager are placed perpendicular to the central axis of the rigid container. A cantilever is fixed above the rigid container, and a positioning post is installed at the top of the piston. The positioning post is fitted and fixed to the square positioning hole of the cantilever so that the piston cannot rotate.

[0011] Step S2: Activate the ignition device inside the rigid container and simultaneously start the high-speed camera, cooled infrared thermal imager, and data recording device; after ignition, the piston moves vertically linearly inside the rigid container; the accelerometer records the dynamic information of the piston's linear acceleration; the high-speed camera collects the piston's trajectory in the rigid container and image information of whether an open flame is generated; the cooled infrared thermal imager collects the dynamic change of the temperature distribution cloud map over time and the highest gas temperature around the inflation port of the gas bladder gas generator throughout the entire test process; the pressure sensor records the dynamic information of the gas pressure value per unit area.

[0012] Step S3: Based on real-time data collected by the high-speed camera, cooled infrared thermal imager, accelerometer, and pressure sensor, perform performance analysis and testing on the airbag gas generator; the total energy E released by the airbag gas generator during ignition and violent combustion. Total Including gas kinetic energy E k Gas internal energy Q G and the internal energy Q of the gas generator metal shell of the airbag s Solve for the gas kinetic energy E respectively. k Its dynamic changes over time, and the internal energy Q of the gas G Its dynamic changes over time, and the internal energy Q of the gas generator metal shell. s Its dynamic changes over time, the gas pressure value per unit area P and its relationship with time, and the effective work ratio η of the gas generator doing work on the outside and its dynamic changes.

[0013] S3.1, Gas kinetic energy E′ k Let E′ be the kinetic energy of the piston's linear motion and E′ be the piston's potential energy. h The sum of

[0014]

[0015] Where m is the piston mass, and T is the time variable, T n For intermediate calculation variables; n = 0, 1, 2, 3, 4…n; b0…b n These are undetermined constants;

[0016] a k =b0+b1T 1 +b2T 2 +b3T 3 +…b n T n To extract the dynamic equation of acceleration versus time using an accelerometer, a k This refers to the linear acceleration of the piston.

[0017] S3.2, Gas internal energy Q G =C p ·M G ·(T G -t0)

[0018] Where t0 is the initial temperature, M G The mass M of the mixed gas produced by the combustion of the airbag gas generator G C p The specific heat capacity at constant pressure of the gas mixture produced by the combustion of the airbag gas generator, C p ;T G The average temperature of the mixed gas that dynamically changes with time T during combustion;

[0019] The internal energy Q of the gas generator metal shell of the airbag s =C s ·M s ·(T s -t0)

[0020] Among them, C s M is the specific heat capacity constant of the metal shell. s T represents the mass of the metal casing or airbag gas generator shell after combustion; s The average temperature of the gas generator metal shell of the gasbag dynamically changes with time T during the combustion process;

[0021] Step S4: After the piston stops moving, turn off all equipment, and record all data and image information by the data recording device.

[0022] Furthermore, in step S3.1, the gas kinetic energy E′ is analyzed and tested. k During the process, because the piston cannot rotate (due to the restriction of the square positioning post and positioning hole), after being impacted by the expansion of the gas released by combustion, the piston moves linearly from low to high along the central axis of the rigid container; the gas kinetic energy is only converted into the linear motion kinetic energy and potential energy of the piston.

[0023] In step S3.1, the gas kinetic energy E′ is analyzed and tested. k During the process, since the piston cannot rotate, it is impacted by the expansion of the gas released from combustion. The piston moves linearly from low to high along the central axis of the rigid container; the kinetic energy of the gas is only converted into the linear motion kinetic energy and potential energy of the piston.

[0024] Read the data from the accelerometer on the outer side of the piston top and extract the dynamic equation of acceleration versus time:

[0025] a k =b0+b1T 1 +b2T 2 +b3T 3 +…b n T n (1)

[0026] In equation (1), a k The linear acceleration of the piston, in mm / ms. 2 b0…b n is an undetermined constant; T is a time variable, in milliseconds; n = 0, 1, 2, 3, 4…n;

[0027] Integrating equation (1) over the time variable T, we can solve the polynomial equation for the linear velocity of the piston versus time:

[0028]

[0029] In equation (2), v′ k The linear velocity of the piston is expressed in mm / ms.

[0030] Equation (2) is integrated again with respect to the time variable T to solve the polynomial equation of the piston's linear motion displacement versus time:

[0031]

[0032] In equation (3), D′ k The linear displacement of the piston is expressed in mm.

[0033] Work-energy theorem:

[0034] Gravitational potential energy: E h =mgh (5)

[0035] The linear motion speed of the piston v′ k Substituting equation (2) into the kinetic energy theorem equation (4):

[0036]

[0037] Equation (6) is the dynamic change equation of the piston's linear motion kinetic energy E′ with time T, which is obtained by the accelerometer. In the equation, E′ is the piston's linear motion kinetic energy in J; m is the piston's mass in kg.

[0038] Substituting equation (3) into equation (5), the piston's potential energy E′ h The change is as follows:

[0039]

[0040] The kinetic energy E′ of the piston's linear motion and the piston's potential energy E′ h The sum of these is the kinetic energy of the gas, E′. k :

[0041]

[0042] Furthermore, in step S3.2, the internal energy Q of the gas is analyzed and tested. G and the internal energy Q of the gas generator metal shell of the airbag s During the process, the total change in internal energy is solved according to the heat absorption formula (8): Q=C·M·(t1-t0)(8);

[0043] In equation (8), Q is the heat absorbed, in J; C is the specific heat capacity, in J / (kg·℃); M is the mass, in kg; t1 is the temperature; and t0 is the initial temperature, in ℃.

[0044] (1) Method for obtaining temperature t1: The temperature distribution cloud map of the entire test process was collected using a cooled infrared thermal imager, and the following data was extracted:

[0045] Time = nΔt; Temperature = T Gn T sn (n = 0, 1, 2, 3, ... n)

[0046] Time represents the moment the temperature distribution cloud map was acquired, in milliseconds (ms); Δt represents the sampling time interval, in milliseconds (ms); Temperature represents the temperature, in degrees Celsius (°C), or T. Gn Let T be the average gas temperature at time nΔt. sn The average temperature of the metal shell of the gas generator in the airbag at time nΔt;

[0047] Then, the average gas temperature T is fitted separately. G The average temperature T of the metal casing of the airbag gas generator s The dynamic equations of T with respect to time are (9)(10), T G T s That is, t1 in equation (8):

[0048] T G =E0+E1T 1 +E2T 2 +E3T 3 +…E n T n (9)

[0049] T s =F0+F1T 1 +F2T 2 +F3T 3 +…F n T n (10)

[0050] E0…E n and F0…F n All are undetermined constants; T is the time variable, in milliseconds (ms).

[0051] (2) Mass of mixed gas M G The solution method is as shown in equation (11): M G =ρ T ·V G (11)

[0052] M G Units: kg; ρ T Density of the gas mixture, in kg·m³ -3 V G Volume, unit m3 Volume of mixed gas V G The sum of the volumes of the closed space formed by the piston hemispherical shell and the rigid container, combined with equation (1), represents the linear displacement D of the piston. k Then the volume of the mixed gas V G Equation of dynamic change over time:

[0053]

[0054] In equation (12), V G Unit m 3 r is the inner radius of the piston hemispherical shell, in mm; R is the inner radius of the hollow cylindrical rigid container, in mm.

[0055] Mixed gas density ρ T The solution method is as follows: Based on the chemical ratio of the ignition agent and the gas-generating agent, the N gas components produced by the gas generator combustion can be obtained through agent experiments or by consulting relevant physicochemical handbooks. The molar ratio of the corresponding N gas components is denoted as:

[0056] N1∶N2∶…N N Where N1+N2+…N N =1; the molar mass of the corresponding N gases is denoted as M. G1 M G2 , ...M GN Unit: kg / mol.

[0057] From the ideal gas law: PV=nR(T+273.15) (13)

[0058] In equation (13), P is pressure, in Pa; V is volume, in m³. 3 n is the number of moles, in mol; R is the proportionality constant, taken as 8.31 J / (mol·K); T is the temperature in Celsius, in °C; 273.15 is the conversion factor for converting Celsius to absolute temperature in K.

[0059] Given n = m / M m Substituting ρ=m / V into equation (13), we get:

[0060] ρ = PM m / [R(T+273.15)] (14)

[0061] In the formula, m is the mass, in kg, M m ρ is the molar mass, in kg / mol, and ρ is the density, in kg·m³. -3 ;;

[0062] In equation (14), the mixed gas pressure is obtained by extracting the dynamic relationship between the gas pressure per unit area and time from the pressure sensor on the inner side of the piston top:

[0063] P = J0 + J1T 1 +J2T 2 +…J n T n (15)

[0064] In equation (15), P is the pressure per unit area, in Pa, J0…J n These are undetermined constants;

[0065] At high temperatures, gas molecules move violently, and the molar mass of a gas mixture is the weighted sum of the molar masses of the N gases:

[0066] M mol =M G1 N1+M G2 N2…+M GN N N (16)

[0067] In equation (16), M mol The value represents the molar mass of the gas mixture, expressed in kg / mol.

[0068] Substituting equations (15), (16), and (9) and R = 8.31 J / (mol·K) into equation (14), we can obtain the density ρ of the mixed gas produced by the combustion of the airbag gas generator. T Polynomial equations that vary with time:

[0069] ρ T =(J0+J1T) 1 +··J n T n (M) G1 N1+··M GN N N ) / [8.31(E0+E1T 1 ··E n T n +273.15)] (17)

[0070] Substituting equations (17), (12), and (1) into equation (11), we obtain the mass M of the mixed gas produced by the combustion of the airbag gas generator. G Polynomial equations that vary with time:

[0071]

[0072] (3) Specific heat capacity of the mixed gas C p The solution method is as follows:

[0073] Since the specific heat capacity of a gas changes with temperature, we first look up the isobaric specific heat capacity of a single gas component at different temperatures; then we fit the isobaric specific heat capacity C of each of the N single gas components. p1 C p2 C p3 …C pN The dynamic equation of temperature t, combined with equation (9) for the average gas temperature T G The functional relationship between time T and the isobaric specific heat capacity C of N single gas components. pN The relationship with temperature t can be transformed into a functional relationship with time T:

[0074] First gas: C p1 =G0+G1T 1 +G2T 2 +…G n T n

[0075] The second gas: C p2 =H0+H1T 1 +H2T 2 +…H n T n

[0076] And so on to the Nth gas: C pN =I0+I1T 1 +I2T 2 +…I n T n

[0077] The above specific heat capacity C p1 C p2 …C pN Units: J / (kg·℃); G0…G n H0…H n ,I0…I n All are undetermined constants;

[0078] The specific heat capacity of the gas mixture at constant pressure, C p The relationship with time T is the weighted sum of the specific heat capacity functions of the N single gas components mentioned above:

[0079] C p =C p1 N1+C p2 N2…+C pN N N (19)

[0080] Let the initial system temperature be t0℃. Substituting (19)(18)(9) into equation (8), we can obtain the energy Q that the gas internal energy increases due to absorption. G for:

[0081] Q G =C p ·M G ·(T G -t0) (20)

[0082] (4) The process for solving the internal energy of the metal shell of the airbag gas generator is the same as above. The specific heat capacity constant C of the metal shell material is found. s The mass M of the gas generator shell after combustion or the empty gas generator shell is obtained by measuring its mass. s Substituting the above parameters and temperature dynamic change equation (10) into equation (8), the energy that can be absorbed by the metal shell of the airbag gas generator is:

[0083] Q s =C s ·M s ·(T s -t0) (21)

[0084] The sum of the gas's kinetic energy and internal energy is the total energy E of the ignition and combustion process of the gas generator in the airbag. Total From equations (7)(20)(21), we can obtain:

[0085] E Total =E′ k +Q G +Q s (twenty two).

[0086] Furthermore, the average gas temperature T at time nΔt Gn The average temperature T of the metal casing of the airbag gas generator sn The data extraction method is as follows:

[0087] 1) Use image processing software to read the temperature distribution cloud map and high-speed camera image acquired by the infrared thermal imager at time nΔt;

[0088] 2) Read the piston movement distance L at time 3Δt using high-speed camera images;

[0089] 3) Based on the temperature distribution cloud map, divide the hollow cylindrical rigid container into regions along the central axis from the inflation port to the piston position according to different temperatures, and record the temperature and the length of each corresponding temperature region:

[0090] t1, L1; t2, L2…t n L n ;

[0091] 4) Using the length ratio of different temperature regions as a weighting factor, calculate the weighted average temperature of the gas at time nΔt:

[0092] in Unit: °C;

[0093] 5) The metal shell of the gas generator has good thermal conductivity and small temperature distribution differences. The temperature at time nΔt can be directly extracted from the temperature distribution cloud map, which is T. s3 , in °C.

[0094] 6) Similarly, extract data T G1 T s1 ;T G2 T s2 ;T G4 T s4 …T Gn T sn Polynomial fitting was performed respectively to obtain equations (9) and (10).

[0095] Furthermore, when a car airbag deploys, it inflates to expand the airbag, and the purpose of this inflation is to expand the airbag. Therefore, only the energy converted into kinetic energy of the gas is effective. From equations (7) and (22), the effective work percentage η is derived as follows:

[0096] η=E′ k / E Total ·100% (23)

[0097] The energy E′ released by the violent combustion of the gas generator during ignition of the airbag is converted into the kinetic energy of the gas according to equation (7). k And its dynamic changes over time; according to equations (20) and (21), the energy Q converted into the internal energy of the gas is solved respectively. G And the energy Q converted into the internal energy of the gas generator metal shell of the airbag s And its dynamic changes over time; the sum of the three parts of energy in equation (22) is the total energy E released by the airbag gas generator. Total And its dynamic change with combustion time T. According to equation (15), the gas pressure value P per unit area and its change with time can be obtained. According to equation (23), the effective work ratio η of the gas generator doing work on the outside can be solved and its dynamic change.

[0098] Furthermore, both the rigid container and the piston are made of a smooth, rigid material, and the portion where the piston contacts the rigid container is coated with a lubricating layer.

[0099] Furthermore, a base is fixed to the bottom of the rigid container, and the gas generator is fixed to the base by bolts. The detonation harness of the gas generator passes through the harness hole on the base and is connected to the ignition device. A cantilever is fixed above the rigid container, and a positioning post is installed on the top of the piston. The positioning post is adapted to the positioning hole of the cantilever.

[0100] Furthermore, the outer wall of the rigid container is provided with vertical scale lines; when not ignited, the piston is located at the starting position of the scale line at the bottom of the rigid container, and the central axis of the pressure sensor and the central axis of the acceleration sensor coincide with the central axis of the hollow cylindrical rigid container; after the ignition device is activated, the igniter of the ignition device detonates the ignition agent, the ignition agent ignites the gas-producing agent, and a large amount of gas is rapidly released, which pushes the piston to move vertically inside the rigid container.

[0101] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0102] (1) The hollow cylindrical rigid container of the present invention is made of transparent material, which makes it easy for a high-speed camera to record whether an open flame is generated during the entire test process; the cross-section of the positioning column matches the shape and size of the positioning hole, which effectively restricts the rotation of the piston, so that the gas kinetic energy of the gas generator during the ignition and violent combustion process is converted only into the linear motion kinetic energy and potential energy of the piston; the part of the piston that contacts the expanding gas is a hemispherical shell structure, which makes the contact position with the column of the hollow cylindrical rigid container smooth, preventing stress concentration, making the piston uniformly stressed, and making the linear motion process more stable.

[0103] (2) This invention can indirectly measure the energy converted from combustion of the airbag gas generator into gas kinetic energy by measuring the linear motion process of the piston; and indirectly measure the energy converted from combustion of the airbag gas generator into gas internal energy and the energy converted into the internal energy of the airbag gas generator metal shell by measuring the temperature changes of the gas and the airbag gas generator metal shell, and derive the proportion of effective work. The gas kinetic energy, gas internal energy, internal energy of the airbag gas generator metal shell, gas pressure per unit area, proportion of effective work and their changes over time, whether an open flame is generated during the test, and the highest gas temperature around the airbag gas generator inflation port can all be included as indicators for evaluating the performance of the airbag gas generator.

[0104] (3) This invention has a reliable theoretical basis, is easy to operate, and provides accurate measurement results. It provides a method for testing and solving multi-dimensional performance evaluation indicators of airbag gas generators, and provides certain technical support for actual research and development and production. Attached Figure Description

[0105] Figure 1 This is a schematic diagram of a rigid container structure in one embodiment of the present invention;

[0106] Figure 2 This is a schematic diagram of a piston structure in one embodiment of the present invention;

[0107] Figure 3 This is a schematic diagram of a rigid container and piston assembly in one embodiment of the present invention;

[0108] Figure 4This is a test schematic diagram of the present invention. Detailed Implementation

[0109] The technical solution of the present invention will be described in detail below, but the scope of protection of the present invention is not limited to the embodiments described.

[0110] As the energy released after the airbag gas generator 8 is ignited and combusted violently, part of it is converted into the kinetic energy of the gas and part of it is converted into the internal energy of the gas and the metal shell of the airbag gas generator 8, causing the temperature of the gas, the metal shell of the airbag gas generator 8 and the surrounding parts to rise.

[0111] To accurately test the performance of the airbag gas generator 8, the technical solution adopted in this invention is as follows: a vertically placed transparent hollow cylindrical rigid container 1 is set up under normal pressure, in which a piston 4 is set up to contact the airbag gas generator 8, and the rotation of the piston 4 is restricted; by recording the vertical movement trajectory of the piston 4 in the rigid container 1 during the intense combustion process of the airbag gas generator 8, a simplified physical model is formed, and the energy of the linear motion of the piston 4 is measured and calculated.

[0112] Since the rotation of piston 4 is restricted by the square positioning hole and positioning pin 5, no rotational energy is generated during the entire process; the linear motion kinetic energy and increased potential energy of piston 4 are the energy converted into gas kinetic energy by the combustion of airbag gas generator 8. The internal energy includes: the portion converted into gas internal energy, the portion converted into the internal energy of the metal shell of airbag gas generator 8, and the portion converted into the internal energy of peripheral components. This portion of energy causes the temperature of the gas, the metal shell of airbag gas generator 8, and peripheral components to rise.

[0113] The peripheral components of the testing device in this invention are all made of materials with very low thermal conductivity. Furthermore, the entire process of the airbag gas generator 8 igniting and releasing heat is generally within 100ms, which can be simplified into a physical model. The heat conduction and internal energy increase of the peripheral components are ignored; only the portion converted into gas internal energy and the portion converted into the internal energy of the metal shell of the airbag gas generator 8 are considered. The increase in gas internal energy mainly occurs through intermolecular thermal convection and thermal conduction; the increase in the internal energy of the metal shell of the airbag gas generator 8 mainly occurs through inter-solid thermal conduction. Since the entire testing process is in the millisecond range, and based on the rates of thermal conduction and convection, commonly used resistance temperature detectors (RTDs) and thermocouples are insufficient to achieve the required sampling frequency and sensitivity. Therefore, a high-sampling-frequency infrared thermometer is needed to measure the gas temperature between the airbag gas generator 8 and the gas between the airbag gas generator 8's inflation port and the piston 4, and to determine the portions converted into gas internal energy and the portions converted into the internal energy of the metal shell of the airbag gas generator 8. The sum of the gas kinetic energy and internal energy is the total energy of the gas generator 8 during the ignition and combustion process; a pressure sensor 6 is provided on the top of the piston 4, and the gas pressure can be measured by the pressure sensor 6.

[0114] like Figure 1As shown, the performance testing method for the automotive airbag gas generator 8 based on the accelerometer sensor 7 of the present invention includes the following steps:

[0115] Step S1: Set up the test device; the test device includes a rigid container 1, a piston 4, a high-speed camera 9, and a cooled infrared thermal imager 10; the rigid container 1 is a transparent hollow cylinder, and an airbag gas generator 8 is fixed at the bottom of the rigid container 1. The piston 4 is located inside the rigid container 1. The piston 4 is a hemispherical shell with the opening facing downward. A pressure sensor 6 and an acceleration sensor 7 are set at the center of the top of the piston 4. The high-speed camera 9 and the cooled infrared thermal imager 10 are respectively placed perpendicular to the central axis of the rigid container 1.

[0116] Step S2: Activate the ignition device inside the rigid container 1, and simultaneously start the high-speed camera 9, the cooled infrared thermal imager 10, and the data recording device; after ignition, the piston 4 moves vertically linearly inside the rigid container 1; the accelerometer 7 records the dynamic information of the acceleration of the linear movement of the piston 4; the high-speed camera 9 collects the image information of the movement trajectory of the piston 4 in the rigid container 1 and whether an open flame is generated; the cooled infrared thermal imager 10 collects the dynamic change process of the temperature distribution cloud map over time and the highest gas temperature around the inflation port of the gas generator 8; the pressure sensor 6 records the dynamic information of the gas pressure value per unit area.

[0117] Step S3: Based on the real-time data collected by the high-speed camera 9, the cooled infrared thermal imager 10, the accelerometer 7, and the pressure sensor 6, perform performance analysis and testing on the airbag gas generator 8; during the performance analysis and testing, first ignite the airbag gas generator 8 and violently combust to release the total energy E. Total Converted into gas kinetic energy E′ k Gas internal energy Q G And the internal energy Q of the airbag gas generator 8 metal shell s Then, we studied its dynamic changes with combustion time T; then we analyzed the gas pressure value P per unit area and its relationship with time, as well as the effective work ratio η of the gas generator 8 doing external work and its dynamic changes.

[0118] S3.1, Gas kinetic energy E′ k Let E′ be the kinetic energy of the linear motion of piston 4 and E′ be the potential energy of piston 4. h The sum of

[0119]

[0120] Where m is the mass of piston 4, and T is the time variable, T n The derivative of the time variable T;

[0121] n=1, 2, 3, 4...n; b0...bn These are undetermined constants;

[0122] a k =b0+b1T 1 +b2T 2 +b3T 3 +…b n T n To extract the dynamic equation of acceleration versus time using accelerometer 7, a k The linear motion acceleration of piston 4;

[0123] S3.2, Gas internal energy Q G =C p ·M G ·(T G -t0)

[0124] Where t0 is the initial temperature, T G M is the average combustion temperature of the gas mixture. G The mass M of the mixed gas produced by the combustion of the airbag gas generator 8 G C p The specific heat capacity C of the mixture produced by the combustion of the airbag gas generator 8 at constant pressure p ;

[0125] The gas generator of the airbag has an internal energy Q in its metal shell. s =C s ·M s ·(T s -t0)

[0126] Among them, C s M is the specific heat capacity constant of the metal shell. s T represents the mass of the metal casing or airbag gas generator 8 shell after combustion. s The average temperature of the metal casing of the airbag gas generator 8;

[0127] Step S4: After piston 4 stops moving, turn off all equipment, and record all data and image information by the data recording device.

[0128] Example 1

[0129] like Figures 1 to 4 As shown, the testing device, connecting parts between devices, and sealing positions involved in this embodiment can withstand a design pressure of over 500 kPa. The high-speed camera 9 used in this embodiment has a sampling frequency of 1000 Hz, and the cooled infrared thermal imager 10 has a sampling frequency of 240 Hz. During testing, the device is arranged as follows:

[0130] The hollow cylindrical rigid container 1 is made of transparent material, with equally spaced graduations on its outer wall. The inner diameter of the rigid container 1 is 2R, and its wall thickness is h. The piston 4 is a hemispherical shell with a mass of m, an inner diameter of 2r, and a wall thickness of h. Both the rigid container 1 and the piston 4 are made of smooth, rigid material, with a lubricating coating on the contact parts. The effect of friction is negligible. The mass unit is kilogram (kg), and the dimension unit is millimeter (mm). A pressure sensor 6 and an acceleration sensor 7 are installed at the center of the top of the hemispherical shell of the piston 4. The central axes of both sensors coincide with the central axis of the hollow cylindrical rigid container 1.

[0131] First, the detonation harness of the gas generator 8 is passed through the harness hole of the base 2 of the hollow cylindrical rigid container 1, and the harness hole of the base 2 is sealed. The gas generator 88 is fixed to the base 22 by bolts. A pressure sensor 66 is set at the center of the top of the hemispherical shell of the piston 4. The piston 4 is placed inside the cylinder of the rigid container 1, and the positioning pin 55 passes through the positioning hole 33 of the cantilever structure. The contact part is coated with a lubricating coating. The piston 4 is placed at the starting position of the scale line on the outside of the cylinder of the rigid container 1, and the base 22 is sealed to the rigid container 1. The fixing bolt holes on the outer ring of the base 22 are connected to the fixing base to fix the entire test system. The high-speed camera 9 and the cooled infrared thermal imager 10 are placed perpendicular to the central axis of the hollow cylindrical rigid container 1. The detonation harness of the gas generator 8 is connected to the ignition device, and the high-speed camera 9, the cooled infrared thermal imager 10, and the pressure sensor 66 are connected to the data recording device. The ignition device is connected to the data recording device.

[0132] The ignition device, high-speed camera 9, cooled infrared thermal imager 10, and data recording device are activated simultaneously. The igniter detonates the ignition agent, which ignites the gas-generating agent, rapidly releasing a large amount of gas. This gas propels piston 4 to move linearly inside the rigid container 1. High-speed camera 9 captures the trajectory of piston 4 and image information indicating whether an open flame is produced. Cooled infrared thermal imager 10 captures the dynamic changes in temperature distribution cloud map over time and the highest gas temperature around the inflation port of the gas generator 8 throughout the test. Pressure sensor 66 on the inner side of the top of piston 4 records the dynamic information of gas pressure per unit area. After piston 4 stops, all equipment is shut down, and all data and image information are recorded by the data recording device.

[0133] Based on the above theoretical derivation, the energy converted from combustion of the gas generator 8 into gas kinetic energy is obtained by measuring the linear motion of piston 4; the energy converted from combustion of the gas generator 8 into gas internal energy and the energy converted into the internal energy of the gas generator 8's metal shell are obtained by measuring the temperature changes of the gas and the gas generator 8's metal shell, and the proportion of effective work is derived. Images recorded by high-speed camera 9 are used to determine whether an open flame is generated during the test; the highest gas temperature around the inflation port of the gas generator 8 during the entire test is obtained by cooled infrared thermal imager 10.

[0134] like Figure 1 As shown, in this embodiment, the rigid container 1, its base 22, and the cantilever are all made of transparent tempered glass with a tempering degree of 2-4 N / cm. It can withstand a stress of 95 MPa, has a smooth surface, a low coefficient of friction, and a thermal conductivity of 1.0 W / m·K, which is only 1 / 400 that of metallic copper, indicating poor thermal conductivity. The rigid container 1 is 450 mm long, has an inner diameter of 26 mm, and a wall thickness of 3 mm. It is designed to measure a gas capacity of approximately 200 liters (L). It has a scale line with a range of 400 mm, with adjacent scale values ​​of 1 mm. The base 2 is detachably and sealingly connected to the hollow cylindrical rigid container 1. The cantilever has a square positioning hole 33 with a side length of 1 mm at the position corresponding to the central axis of the rigid container 1.

[0135] like Figure 2 As shown, in this embodiment, the piston 41 has a hemispherical shell as its main body, with an outer surface diameter of 26 mm and a wall thickness of 2 mm. A positioning post 5, 460 mm long, with a square cross-section of 1 mm sides, is set on the outer side of its top. A pressure sensor 6 is installed at the center of the top of the hemispherical piston. The piston 4 is made entirely of dark tempered glass with a tempering degree of 2–4 N / cm, capable of withstanding a stress of 95 MPa, and has a smooth surface, low coefficient of friction, and a thermal conductivity of 1.0 W / m·K. An acceleration sensor 7 is located on the outer surface of the hemispherical shell of the piston 4.

[0136] Example 2

[0137] The testing apparatus in this embodiment is the same as that in Embodiment 1.

[0138] Since all peripheral components of the testing device are made of materials with very low thermal conductivity, and the entire process of the airbag gas generator 8 igniting and releasing heat is generally within 100ms, it can be simplified into a physical model. The heat conduction and internal energy increase of the peripheral components can be ignored; only the portion converted into gas internal energy and the portion converted into the internal energy of the airbag gas generator 8's metal shell are considered. The increase in gas internal energy mainly occurs through intermolecular thermal convection and thermal conduction; the increase in the internal energy of the airbag gas generator 8's metal shell is mainly through inter-solid thermal conduction. The entire testing process is in the millisecond range. Based on the rates of thermal conduction and convection, commonly used resistance temperature detectors (RTDs) and thermocouples are insufficient to achieve the required sampling frequency and sensitivity. Therefore, a high-sampling-frequency infrared thermometer is needed to measure the gas temperature of the airbag gas generator 8 and the gas temperature between the airbag gas generator 8's inflation port and the piston 4, respectively, to determine the portions converted into gas internal energy and the portions converted into the internal energy of the airbag gas generator 8's metal shell. The sum of the gas kinetic energy and internal energy represents the total energy measured during the ignition and combustion process of the airbag gas generator 8.

[0139] (a) Gas kinetic energy E′ k

[0140] Since the rotation of piston 4 is restricted, during the test, piston 4 is impacted by the expansion of the released gas and moves linearly from a lower to a higher position along the central axis of the rigid container 1; the gas kinetic energy is only converted into the linear motion kinetic energy and potential energy of piston 4. The kinetic energy E′ of the tested gas is analyzed. k During the process, since piston 4 cannot rotate, after being impacted by the expansion of the gas released by combustion, piston 4 moves linearly from low to high along the central axis of rigid container 1; the gas kinetic energy is only converted into the linear motion kinetic energy and potential energy of piston 4.

[0141] Read the data from the accelerometer 7 on the outer side of the top of piston 4, and extract the dynamic equation of acceleration versus time:

[0142] a k =b0+b1T 1 +b2T 2 +b3T 3 +…b n T n (1)

[0143] In equation (1), a k The linear acceleration of piston 4 is expressed in mm / ms. 2 b0…b n is an undetermined constant; T is a time variable, in milliseconds; n = 1, 2, 3, 4…n;

[0144] Integrating equation (1) over the time variable T, we can solve the polynomial equation for the linear motion velocity of piston 4 with respect to time:

[0145]

[0146] In equation (2), v′ k The linear motion speed of piston 4 is expressed in mm / ms.

[0147] Equation (2) is integrated again with respect to the time variable T to solve the polynomial equation of the linear motion displacement of piston 4 with respect to time:

[0148]

[0149] In equation (3), D′ k The linear displacement of piston 4 is expressed in mm.

[0150] Work-energy theorem:

[0151] Gravitational potential energy: E h =mgh (5)

[0152] The linear motion speed v′ of piston 4 k Substituting equation (2) into the kinetic energy theorem equation (4):

[0153]

[0154] Equation (6) is the dynamic change equation of the linear motion kinetic energy E′ of piston 4 with time T, which is obtained by accelerometer 7. In the equation, E′ is the linear motion kinetic energy of piston 4, in J; m is the mass of piston 4, in kg.

[0155] Substituting equation (3) into equation (5), the potential energy E′ of piston 4 is... h The change is as follows:

[0156]

[0157] The linear motion kinetic energy E′ and potential energy E′ of piston 4 h The sum of these is the kinetic energy of the gas, E′. k :

[0158]

[0159] (2) Internal energy Q G Q s :

[0160] Since the piston 4, the hollow cylindrical rigid container 1, and the peripheral components in this embodiment are all made of materials with poor thermal conductivity, and the entire process of the airbag gas generator 88 igniting and releasing heat is generally within 100ms, it can be simplified into a physical model. The heat conduction and internal energy increase of the peripheral components are ignored; only the portion converted into gas internal energy and the portion converted into the internal energy of the metal shell of the airbag gas generator 88 are considered. The increase in gas internal energy is mainly through two methods: thermal convection and thermal conduction between gas molecules; the increase in internal energy of the metal shell of the airbag gas generator 88 is mainly through inter-solid thermal conduction. The gas temperature is highest at the inflation port of the airbag gas generator 88. As the amount of gas released increases and it expands, the temperature decreases with increasing distance; the closer to the piston 4, the lower the gas temperature.

[0161] The change in internal energy is calculated using the heat absorption formula: Q=C·M·(t1-t0) (8)

[0162] (1) Method for obtaining temperature t1: The temperature distribution cloud map of the entire test process was collected using a cooled infrared thermal imager 10, and the following data was extracted:

[0163] Time = nΔt; Temperature = T Gn T sn

[0164] Based on the above data, the average gas temperature T is fitted. G The average temperature of the metal casing of the airbag gas generator is T. s The dynamic equations of T with respect to time are (9)(10), T G T s That is, t1 in equation (8):

[0165] T G =E0+E1T 1 +E2T 2 +E3T 3 +…E n T n (9)

[0166] T s =F0+F1T 1 +F2T 2 +F3T 3 +…F n T n (10)

[0167] (2) The average gas temperature T at time nΔt above Gn The average temperature of the metal casing of the airbag gas generator is T. sn The data extraction method is as follows, with Time = 3Δt and Temperature = T G3T s3 For example:

[0168] 1) Use image processing software to read the temperature distribution cloud map and high-speed camera image acquired by the infrared thermal imager 10 at time 3Δt;

[0169] 2) Read the piston 4 movement distance L at time 3Δt using high-speed camera images;

[0170] 3) Based on the temperature distribution cloud map, divide the hollow cylindrical rigid container 1 into regions along the central axis from the inflation port to the piston 4 according to different temperatures, and record the temperature and the length of each temperature region:

[0171] t1, L1; t2, L2…t n L n ;

[0172] 4) Using the length ratio of different temperature regions as a weighting factor, calculate the weighted average temperature of the gas at time 3Δt:

[0173] in Unit: °C.

[0174] 5) The metal shell of the gas generator 8 has good thermal conductivity and small temperature distribution differences. The temperature at time 3Δt can be directly extracted from the temperature distribution cloud map, which is T. s3 , in °C.

[0175] 6) Similarly, extract data T G1 T s1 ;T G2 T s2 ;T G4 T s4 …T Gn T sn Polynomial fitting was performed respectively to obtain equations (9) and (10).

[0176] (3) Mass of mixed gas M G Solution:

[0177] M G =ρ T ·V G (11)

[0178] In equation (11), M G Units: kg; ρ T Density of mixed gas, unit: kg·m³ -3 V G Volume, unit m 3 .

[0179] Mixed gas volume V GThe sum of the volumes of the closed space formed by the hemispherical shell of piston 4 and the hollow cylindrical rigid container 1, combined with equation (1), represents the linear displacement D of piston 4. k Then the volume of the mixed gas V G Equation of dynamic change over time:

[0180] Mixed gas density ρ T Solution: Based on the chemical ratio of the ignition and gas-generating agents, the N gas components produced by the gas generator 8 can be obtained through agent experiments or by consulting relevant physicochemical handbooks. The molar ratio of the corresponding N gas components is denoted as: N1∶N2∶…N N Where N1+N2+…N N =1;

[0181] The molar mass of the corresponding N gases is denoted as M. G1 M G2 , ...M GN

[0182] From the ideal gas law: PV=nR(T+273.15) (13)

[0183] Given n = m / M m Substituting ρ=m / V into equation (13), we get:

[0184] ρ = PM m / [R(T+273.15)] (14)

[0185] In the formula, m: mass, unit kg, M m Molar mass, in kg / mol; ρ: density, in kg·m³. -3 The remaining parameters are the same as in equation (13).

[0186] The mixed gas pressure P is obtained by extracting the dynamic relationship between the gas pressure per unit area and time from the pressure sensor 6 on the inner side of the top of piston 4:

[0187] P = J0 + J1T 1 +J2T 2 +…J n T n (15)

[0188] At high temperatures, gas molecules move violently, and the molar mass of the gas mixture is the weighted sum of the molar masses of the N gases: M mol =M G1 N1+M G2 N2…+M GN N N (16)

[0189] In equation (16), Mmol Molar mass of the gas mixture, in kg / mol.

[0190] Substituting equations (15), (16), and (9) and R = 8.31 J / (mol·K) into equation (14), we can obtain the density ρ of the mixed gas produced by the combustion of the airbag gas generator 8. T Polynomial equations that vary with time:

[0191] ρ T =(J0+J1T) 1 +··J n T n (M) G1 N1+··M GN N N ) / [8.31(E0+E1T 1 ··E n T n +273.15)] (17)

[0192] Substituting equations (17), (12), and (1) into equation (11), we obtain the mass M of the mixed gas produced by the combustion of the airbag gas generator 8. G Polynomial equations that vary with time:

[0193]

[0194] (4) Specific heat capacity of the mixed gas C p Solution method:

[0195] The specific heat capacity of a gas changes with temperature. Consulting relevant physicochemical parameter handbooks, one can obtain the isobaric specific heat capacity of a single gas component at different temperatures. From the above data, the isobaric specific heat capacity C of N single gas components can be fitted. p1 C p2 C p3 …C pN The dynamic equation of temperature t, combined with equation (9) for the average gas temperature T G The functional relationship between time T and the isobaric specific heat capacity C of N single gas components. pN The relationship with temperature t can be transformed into a functional relationship with time T:

[0196] The first gas: C p1 =G0+G1T 1 +G2T 2 +…G n T n

[0197] The second gas: C p2 =H0+H1T 1 +H2T 2 +…Hn T n

[0198] And so on to the Nth gas: C pN =I0+I1T 1 +I2T 2 +…I n T n

[0199] The specific heat capacity of the gas mixture at constant pressure, C p The relationship with time T is the weighted sum of the specific heat capacity functions of the above N single gas components:

[0200] C p =C p1 N1+C p2 N2…+C pN N N (19)

[0201] Let the initial system temperature be t0℃. Substituting (19)(18)(9) into equation (8), we can obtain the energy Q that the gas internal energy increases due to absorption. G for:

[0202] Q G =C p ·M G ·(T G -t0) (20)

[0203] (5) Similarly, to calculate the internal energy of the metal shell of the gas generator 8, first find the specific heat capacity constant C of the metal shell material. s The mass M of the gas generator 8 after combustion, either the metal casing or the empty casing, is obtained by measuring its mass. s Substituting the above parameters and temperature dynamic change equation (10) into equation (8), the energy that can be absorbed by the metal shell of the airbag gas generator 8 is:

[0204] Q s =C s ·M s ·(T s -t0) (21)

[0205] (6) The sum of the gas kinetic energy and internal energy is finally obtained as the total energy E of the ignition and combustion process of the gas generator 8 in the airbag. Total E Total =E′+Q G +Q s (twenty two).

Claims

1. A method for testing the performance of an automotive airbag gas generator based on an acceleration sensor, characterized in that: Includes the following steps: Step S1: Set up the test device, which includes a rigid container, a piston, a high-speed camera, and a cooled infrared thermal imager. The rigid container is a transparent hollow cylinder. An airbag gas generator is fixed at the bottom of the rigid container. The piston is located inside the rigid container and is a hemispherical shell with its opening facing downwards. A pressure sensor and an acceleration sensor are set at the center of the top of the piston. The high-speed camera and the cooled infrared thermal imager are placed perpendicular to the central axis of the rigid container. A cantilever is fixed above the rigid container. A positioning post is installed on the top of the piston. The positioning post is fitted and fixed to the square positioning hole of the cantilever so that the piston cannot rotate. Step S2: Activate the ignition device inside the rigid container and simultaneously start the high-speed camera, cooled infrared thermal imager, and data recording device; after ignition, the piston moves vertically linearly inside the rigid container; the accelerometer records the dynamic information of the piston's linear acceleration; the high-speed camera collects the piston's trajectory in the rigid container and image information of whether an open flame is generated; the cooled infrared thermal imager collects the dynamic change of the temperature distribution cloud map over time and the highest gas temperature around the inflation port of the gas bladder gas generator throughout the entire test process; the pressure sensor records the dynamic information of the gas pressure value per unit area. Step S3: Based on real-time data collected by the high-speed camera, cooled infrared thermal imager, accelerometer, and pressure sensor, perform performance analysis and testing on the airbag gas generator; the total energy released by the airbag gas generator upon ignition and violent combustion... Including gas kinetic energy Gas internal energy and the internal energy of the metal shell of the airbag gas generator Solve for the kinetic energy of the gas respectively. and its dynamic changes over time, gas internal energy Its dynamic changes over time, and the internal energy of the gas generator metal shell Its dynamic changes over time and the gas pressure per unit area Its relationship with time, and the proportion of effective work done by the airbag gas generator. and its dynamic changes; S3.1, Gas Kinetic Energy The linear motion kinetic energy of the piston and the potential energy of the piston The sum of ； in, For piston mass, For time variables, For intermediate calculation variables; ; These are undetermined constants; To extract the dynamic equation of acceleration versus time using an accelerometer, This refers to the linear acceleration of the piston. S3.2, Internal Energy of Gas ), in, The initial temperature, The mass of the mixed gas produced by the combustion of the airbag gas generator ; The specific heat capacity at constant pressure of the gas mixture produced by the combustion of the airbag gas generator ; For the combustion process over time The average temperature of the dynamically changing mixed gas; Internal energy of the metal shell of the airbag gas generator , in, Let be the specific heat capacity constant of the metal shell. The mass of the metal casing or airbag gas generator shell after combustion. For the combustion process over time The average temperature of the metal casing of the airbag gas generator changes dynamically. The calculation was obtained Subsequently, the total energy of the airbag gas generator during ignition and combustion was measured. : (22) Analysis and Testing and hour, The average gas temperature at time 10:00 Average temperature of the metal casing of the airbag gas generator The data extraction method is as follows: 1) Use image processing software to read the time of acquisition by the infrared thermal imager. Temperature distribution cloud maps and high-speed camera images; 2) Reading images via high-speed camera The piston movement distance L at any given moment; 3) Based on the temperature distribution cloud map, divide the hollow cylindrical rigid container into regions along the central axis from the inflation port to the piston position according to different temperatures, and record the temperature and the length of each temperature region: ; 4) Using the length ratio of different temperature regions as a weighting factor, calculate... The average gas temperature at that time: , in ; 5) The metal shell of the gas generator for the airbag has good thermal conductivity and small temperature distribution differences, allowing for direct extraction of its temperature from the temperature distribution cloud map. Average temperature of the metal casing of the airbag gas generator at any given time ; 6) Finally, polynomial fitting is performed to obtain the average gas temperature. Average temperature of the metal casing of the airbag gas generator Over time The dynamic change equation; Step S4: After the piston stops moving, turn off all equipment, and record all data and image information by the data recording device.

2. The method for testing the performance of an automotive airbag gas generator based on an acceleration sensor according to claim 1, characterized in that: In step S3.1, the gas kinetic energy is analyzed and tested. During the process, since the piston cannot rotate, it is impacted by the expansion of the gas released from combustion. The piston moves linearly from low to high along the central axis of the rigid container; the kinetic energy of the gas is only converted into the linear motion kinetic energy and potential energy of the piston. Read the data from the accelerometer on the outer side of the piston top and extract the dynamic equation of acceleration versus time: (1) Equation (1) for time variables Integrate and solve the polynomial equations for the linear velocity and time of the piston: (2) In equation (2), The linear velocity of the piston; Equation (2) for time variables Integrate again to solve the polynomial equations for the linear motion of the piston versus time: (3) In equation (3), The displacement is the linear motion displacement of the piston; Work-energy theorem: (4) Gravitational potential energy: (5) linear speed of piston movement Substituting equation (2) into the kinetic energy theorem equation (4): (6) Equation (6) is the kinetic energy of the piston's linear motion obtained by the accelerometer. Over time The dynamic change equation; Substituting equation (3) into equation (5), the potential energy of the piston is... The change is as follows: (7) The linear motion kinetic energy of the piston and the potential energy of the piston The sum of these is the kinetic energy of the gas. : 。 3. The method for testing the performance of an automotive airbag gas generator based on an acceleration sensor according to claim 2, characterized in that: In step S3.2, the internal energy of the gas is analyzed and tested. and the internal energy of the metal shell of the airbag gas generator During the process, the total change in internal energy is calculated according to the heat absorption formula (8): (8)； For the heat absorbed, For specific heat capacity, For quality, For temperature, The initial temperature; (1) Temperature Acquisition method: A cooled infrared thermal imager was used to acquire temperature distribution cloud maps over time throughout the entire testing process. The dynamic change process was observed, and the following data was extracted: Time= ; Temperature = , Time represents the moment the temperature distribution cloud map was collected. The sampling time interval is represented by Temperature. for The average gas temperature at that time. for The average temperature of the metal casing of the airbag gas generator at the corresponding moment; Then, the average gas temperature was fitted separately. Average temperature of the metal casing of the airbag gas generator Over time The dynamic change equations (9)(10) That is, in equation (8) : (9) (10) and All are undetermined constants; It is a time variable; (2) Mass of mixed gas The solution method is shown in equation (11): (11) The density of the mixed gas; The volume of the mixed gas; (2.1) Volume of mixed gas The sum of the volumes of the closed space formed by the piston hemispherical shell and the rigid container, combined with equation (1), represents the linear displacement of the piston. The volume of the mixed gas Equation of dynamic change over time: (12) In the above formula The inner radius of the piston hemispherical shell; The inner radius of the rigid container; (2.2) Density of mixed gas The solution method is as follows: based on the combustion of the airbag gas generator... gas components , obtain the corresponding molar ratio of gas components ; in, ; From the ideal gas law: (13) In the above formula For pressure, For volume, The number of moles. It is a proportionality constant. 273.15 is in Celsius. Convert 273.15 degrees Celsius to absolute temperature. Conversion factor; Known , Substituting into equation (13), we get: (14) For quality, molar mass Density; The pressure of the mixed gas; Based on the dynamic relationship between the gas pressure value per unit area and time extracted by the pressure sensor, the following is obtained: : (15) In the above formula For undetermined constants, It is a time variable; At high temperatures, gas molecules move violently, and the molar mass of the gas mixture is... The weighted sum of the molar masses of the gases, i.e., the molar mass of the gas mixture. : (16) Formulas (15)(16)(9) and =8.31 Substituting into equation (14), the density of the mixed gas produced by the combustion of the airbag gas generator can be obtained. Polynomial equations that vary with time: (17) Substituting equations (17), (12), and (1) into equation (11), we obtain the mass of the mixed gas produced by the combustion of the airbag gas generator. Polynomial equations that vary with time: { }·[ ]· (18) (3) Specific heat capacity of the mixed gas The solution method is as follows: First, fit the results separately. Specific heat capacity at constant pressure of a single gas component The dynamic change equation with temperature, combined with equation (9) for the average gas temperature. With time The functional relationship will Specific heat capacity at constant pressure of a single gas component The relationship with temperature is transformed into the relationship with time. Functional relationship: The first gas: , The second gas: , And so on up to the 1st Gases: , The above specific heat capacity ; , , All are undetermined constants; The specific heat capacity of the gas mixture at constant pressure With time The relationship is as described above. Weighted sum of the isobaric specific heat capacities of a single gas component: (19) The initial system temperature is denoted as Substituting (19)(18)(9) into equation (8), we can obtain the internal energy of the gas. for: (20) (4) The internal energy of the metal shell of the airbag gas generator was calculated. as follows: (21)。 4. The method for testing the performance of an automotive airbag gas generator based on an acceleration sensor according to claim 2 or 3, characterized in that: In step S3, only the energy converted into gas kinetic energy is effective during the entire process of the airbag inflating and doing work after its explosion. The effective work percentage can be derived from equations (7) and (22). for: (23) The energy released by the violent combustion of the gas generator during ignition of the airbag is converted into the kinetic energy of the gas according to equation (7). and its dynamic changes over time; The energy converted into gas internal energy can be obtained by solving equations (20) and (21) respectively. And the energy converted into the internal energy of the metal shell of the airbag gas generator. And its dynamic changes over time; the sum of the three parts of energy in equation (22) is the total energy released by the airbag gas generator. and its duration of combustion Dynamic changes; The gas pressure per unit area is obtained according to equation (15). and its relationship with time; According to equation (23), the effective work ratio of the gas generator in the airbag can be calculated. And its dynamic changes.

5. The method for testing the performance of an automotive airbag gas generator based on an acceleration sensor according to claim 1, characterized in that: Both the rigid container and the piston are made of a smooth, rigid material, and the part where the piston contacts the rigid container is coated with a lubricating layer.

6. The method for testing the performance of an automotive airbag gas generator based on an acceleration sensor according to claim 1, characterized in that: The rigid container is fixed to a base at the bottom. The gas generator is fixed to the base by bolts. The detonation harness of the gas generator passes through the harness hole on the base and is connected to the ignition device.

7. The method for testing the performance of an automotive airbag gas generator based on an acceleration sensor according to claim 1, characterized in that: The rigid container has vertical scale lines on its outer wall. When not ignited, the piston is located at the starting position of the scale line at the bottom of the rigid container. The central axis of the pressure sensor and the central axis of the acceleration sensor coincide with the central axis of the hollow cylindrical rigid container. After the ignition device is activated, the igniter of the ignition device detonates the ignition agent, which ignites the gas-producing agent and rapidly releases a large amount of gas. The gas pushes the piston to move vertically inside the rigid container.

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