Air tightness test scaled vehicle body and air tightness test method

Abstract

The invention discloses an air tightness test scaling vehicle body which comprises a plurality of carriages, each carriage is provided with a sealed cabin, the sealed cabins of the adjacent carriages are communicated with each other, and partition structures for separating the interiors of the sealed cabins of the carriages are arranged at the joints of the carriages; and each carriage is provided with a pressure sensor. The invention discloses an air tightness test method. According to the air tightness test scaled vehicle body and the air tightness test method provided by the invention, the multi-vehicle marshalling is formed by the plurality of carriages, each carriage is provided with the pressure sensor, the plurality of carriages are provided with the integral sealed cabin, and the separation structures for separating the interiors of the sealed cabins of the carriages are arranged at the joints of the carriages; according to the utility model, two states of communication and separation of a plurality of carriages can be simulated, so that the static sealing index relationship between a single carriage and the plurality of carriages, the dynamic sealing index relationship between the single carriage and the plurality of carriages, and the relationship between the static sealing indexes and the dynamic sealing indexes of the single carriage and the plurality of carriages can be researched.

Description

Technical Field

[0001] The present application relates to the field of traffic technology, and in particular to an airtightness test scaled vehicle body and an airtightness test method. Background Art

[0002] At present, the research on the air tightness of the vehicle body is mainly obtained through real vehicle test, but the real vehicle test is limited by the on-site test conditions, and it is difficult to obtain accurate results of the dynamic air tightness of the vehicle body. In addition, the dynamic test of the real vehicle test is not carried out immediately after the static test, and the air tightness of the vehicle body in the on-site test changes after running for a period of time. Therefore, the dynamic air tightness test results under the same working conditions are difficult to correspond to the static air tightness test results.

[0003] Some studies have also adopted dynamic model testing methods, but the current dynamic model test research on the train sealing index is only a static sealing test and a dynamic sealing test of a single carriage, and it is impossible to obtain the degradation law of the dynamic sealing index of a train with multiple carriages; secondly, the sealing performance of the model car body is poor, which makes it difficult to effectively control the variable of equivalent leakage area. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide an airtightness test scaled car body and an airtightness test method, which can study the static sealing index relationship between a single section and multiple sections of the car, the dynamic sealing index relationship between a single section and multiple sections of the car, and the relationship between the static and dynamic sealing indexes of a single section and multiple sections of the car.

[0005] The technical solution provided by the present invention is as follows: A scaled car body for airtightness test comprises a plurality of carriages, each of which is provided with a sealed cabin, the sealed cabins of adjacent carriages are interconnected, and a partition structure is provided at the connection between the carriages to separate the interiors of the sealed cabins of the carriages from each other; each carriage is equipped with a pressure sensor.

[0006] Preferably, the head and tail carriages are each equipped with 6 pressure sensors, and the middle carriage is equipped with 4 pressure sensors, so as to form multiple measuring points to analyze the changing pattern of the sealing index inside the carriage.

[0007] Preferably, each carriage includes an outer shell, which is fixed to the sealed cabin. The outer shell of each carriage is provided with a door, which is fixed to the outer shell by screws. Different sealing performances can be obtained by adjusting the pre-tightening force of the screws. The door is detachably fixed to the outer shell and is provided with a leakage hole. Different equivalent leakage areas can be simulated by replacing doors with different leakage holes.

[0008] Preferably, the pressure collection port of each pressure sensor forms a measuring point on the carriage, the measuring points inside and outside the carriage correspond to each other, and are arranged on the right side of the train running direction. The outside pressure collection port extends from the inside of the car body shell to the outside, and the inside pressure collection port extends from the outside of the sealed cabin to the inside.

[0009] Preferably, it also includes a data acquisition device and a power supply device. The pressure sensor body, data acquisition device and power supply device are installed in an internal equipment installation area arranged on the left side of the vehicle body's running direction. The internal equipment installation area is located in the avoidance space arranged at the bottom of the sealed cabin, so that all test devices are installed inside the outer shell.

[0010] Preferably, a groove is provided between the shell and the sealed cabin for placing the wiring of the sensor. The data transmission line of each sensor passes through the hollow beam at the bottom of the vehicle body, and is collected and stored in the data acquisition device at the rear of the vehicle.

[0011] Preferably, the data acquisition device operates independently, is installed inside the vehicle body shell, and is fixed to the steel beam at the bottom of the vehicle body without contacting the sealed cabin.

[0012] An air tightness test method, using the air tightness test scaled vehicle body as described above, the method comprising: Step 1: Connect an air pump to each carriage; turn on the air pump to pressurize the sealed cabin. When the air pressure rises to a certain value, immediately close the air inlet valve. At this time, the air pressure inside the sealed cabin drops rapidly. Record the time t when the pressure difference between the inside and outside of the sealed cabin drops from Δp1 to Δp2, and then calculate the static sealing index according to the formula: , get the static sealing index, where is the static sealing index, Δp1 is the initial pressure difference between the inside and outside of the car, and Δp2 is the pressure difference between the inside and outside of the car after the pressure drops. Replace the car door and repeat the above operation to obtain the corresponding static sealing index under different equivalent leakage areas.

[0013] Preferably, after obtaining the static sealing index corresponding to different equivalent leakage areas, the method further includes step 2: taking the static pressure relief time at different leakage holes as a reference, a static pressure relief test of door pressure relief is performed. The specific operation is to change the gap size at the edge of the door by adjusting the pre-tightening force of the screws on the door, and equating the pressure relief time of the door with the pressure relief time of the leakage hole. When the pressure relief time is greater than the target time, the pre-tightening force of the screws is increased; when the pressure relief time is less than the target time, the pre-tightening force of the screws is reduced. Then, the above pressurization steps are repeated, and the time t when the pressure in the sealed cabin drops from p1 to p2 is recorded, so that a variety of door pressure relief working conditions can be obtained; Step 3: Provide a semi-cylindrical space at the rear to simulate a tunnel; fix the scaled car body on the power trailer; launch the power trailer to perform dynamic air tightness test on the scaled car body, including measuring the dynamic air tightness of the car at different speeds, changing the gap size at the edge of the car door by adjusting the pre-tightening force of the screws on the car door to simulate the influence of the car door under actual running conditions, and obtaining the dynamic sealing index at the measuring point under different working conditions; Step 4: Compare the dynamic sealing index obtained in step 3 with the static sealing index obtained from the corresponding static air tightness test to obtain the ratio of the dynamic and static sealing indexes during the operation of the train and the change pattern of the ratio of the dynamic and static sealing indexes from the tail car to the head car.

[0014] Preferably, the method further includes step five: partitioning each carriage, and then performing a dynamic air tightness test according to step three to obtain a dynamic sealing index under the condition of compartment partition, and then comparing the dynamic sealing index under the condition of compartment partition with the dynamic sealing index under the condition of compartment penetration obtained in step three to analyze the influence of compartment penetration and carriage partition on the sealing index of the train.

[0015] Compared with the prior art, the airtightness test scaled car body and airtightness test method of the present invention, by including multiple carriages to form a multi-car formation, each carriage is equipped with a pressure sensor, the multiple carriages are provided with an integral sealed cabin, and a partition structure is provided at the connection between each carriage to separate the inside of the sealed cabin of each carriage from each other, which can simulate the two states of multi-carriage connection and partition. In this way, the static sealing index relationship between a single section and multiple carriages, the dynamic sealing index relationship between a single section and multiple carriages, and the relationship between the static and dynamic sealing indexes of a single section and multiple carriages can be studied. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a side view schematic diagram of the internal structure of the leading car compartment and the trailing car compartment in the air tightness test scale car body of an embodiment of the present invention; Figure 2 for Figure 1 The schematic side view of the internal structure of the head car compartment in the air tightness test scale car body shown; Figure 3 for Figure 1 The schematic front view of the scaled-down vehicle body for the airtightness test is shown; Figure 4 for Figure 1 The schematic diagram of the measuring point positions of the sealed cabin of the leading vehicle in the airtightness test scale vehicle body is shown; Figure 5 for Figure 1 The schematic diagram of the measuring point position of the middle sealed cabin in the airtightness test scale vehicle body is shown; Figure 6 for Figure 1 The schematic diagram of the measuring point positions of the tail car sealed cabin in the airtightness test scale car body is shown; Figure 7 for Figure 1 The schematic diagram of the first structure of the door in the scaled vehicle body for the airtightness test is shown; Figure 8 for Figure 1 The schematic diagram of the second structure of the door in the scaled-down vehicle body for the airtightness test is shown; Fig. 9 for Figure 1 The schematic diagram of the third structure of the door in the scaled-down vehicle body for airtightness test is shown; Fig.10 for Figure 1 The schematic diagram of the fourth structure of the door in the scaled vehicle body for air tightness test is shown. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] It should be noted that when an element is referred to as being "fixed on" or "set on" another element, it can be directly on the other element or indirectly set on the other element; when an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0020] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" and "several" mean two or more, unless otherwise clearly and specifically defined.

[0022] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

[0023] like Figures 1 to 10 As shown, an embodiment of the present invention provides a scaled-down car body for air tightness test, comprising three carriages (in other embodiments, the number of carriages may be other numbers) forming a three-car formation. The scale ratio of the scaled-down car body to the actual car body is 1:20.

[0024] The three carriages are defined as the head carriage, the middle carriage, and the tail carriage. Each body is divided into two parts: a sealed cabin 2 and a car body shell (not shown). Each carriage is provided with a sealed cabin 2, and the sealed cabins 2 of adjacent carriages are interconnected, and a partition structure 5 is provided at the connection of each carriage to separate the inside of the sealed cabins 2 of each carriage from each other (in this embodiment, a card slot is provided at the connection of the carriages, and a baffle is inserted into the card slot when partition is required. Of course, other embodiments can also adopt other different structures). A trailer hook 1 for installation with a power trailer is provided at the lower end of the head of the tail car, and a track hook 6 is provided at the bottom of each carriage for fixing the car body on the track of the dynamic model test platform. A car door 3 is provided on the shell of each carriage, and the car door 3 is located on the right side of the running direction of each carriage. Six screw holes are provided on the car door 3, and different sealing performances can be obtained by adjusting the screw preload, and leakage holes can also be provided on the car door 3 to obtain different equivalent leakage areas. The car door 3 can be disassembled for easy replacement. On the left side of the running direction of the scaled vehicle body, an internal equipment installation area 4 is provided (the internal equipment installation area is located in the avoidance space provided at the bottom of the sealed cabin 2) for installing pressure sensors, data acquisition devices and power supply equipment, and a vehicle body shell mounting hole 7 is provided for fixing the sealed cabin 2 and the scaled vehicle body shell together by bolts.

[0025] Each carriage is equipped with a pressure sensor. In this embodiment, the head and tail carriages are each equipped with 6 pressure sensors, and the middle carriage is equipped with 4 pressure sensors, so as to form 16 measuring points (the positions of the measuring points are as follows Figures 4 to 6As shown in the figure, the changing law of the sealing index inside the carriage is analyzed. Setting multiple measuring points in a single carriage is conducive to analyzing the changing law of the sealing index inside the carriage. In order to improve the stability of the scaled car body, the sealed cabin 2 is provided with grids of reinforcing ribs, and the in-car pressure measuring points are set at the center of these grids to reduce the influence of the raised reinforcing ribs on the pressure data collection. The sensor body is installed in the internal equipment installation area 4, and the pressure monitoring points inside and outside the carriage correspond to each other (such as measuring points 1 and 2, 3 and 4), and are placed on the right side of the train running direction. The car body shell is separated from the sealed cabin 2, and the external pressure collection port extends from the inside of the car body shell to the outside, and the internal pressure collection port extends from the outside of the sealed cabin 2 to the inside. A 2mm groove is provided between the car body shell and the sealed cabin 2 for placing the sensor wiring. The data transmission lines of each sensor pass through the hollow beam at the bottom of the car body, and are collected and stored in the data acquisition device at the rear of the car.

[0026] In this embodiment, the door is provided with leakage holes, and different equivalent leakage areas are simulated by replacing the door with different leakage holes. The different leakage holes can be of different areas, or of different numbers, or a combination of different areas and different numbers. In this embodiment, different numbers are used. Figures 7 to 10 The four punching methods shown (i.e., forming 1, 2, 3, and 4 holes respectively) are used to obtain four different static pressure relief times. In this embodiment, the volume of the sealed cabins of the front and rear cars of the scaled car body is 0.0095 cubic meters, and the volume of the sealed cabin of the middle car is 0.0115 cubic meters. According to the equivalent leakage area formula: , the diameter of the leak hole is determined to be 1.80 mm and the area is 2.54 square millimeters. Where V is the volume of the sealed cabin, a is the local sound speed (assumed to be 340m / s), t is the proposed static pressure relief time, ρ is the air density (usually, 1.205kg / m3), is the pressure difference between the inside and outside of the sealed cabin before leakage, It is the pressure difference between inside and outside of the sealed cabin after leakage.

[0027] The scaled car body has three doors in total, so the four equivalent leakage areas corresponding to the scaled car body are 7.63 square millimeters, 15.27 square millimeters, 22.90 square millimeters and 30.54 square millimeters (respectively Figures 7 to 10 As shown in the figure). The car door is detachable. By replacing different car doors with different numbers of leakage holes, different equivalent leakage areas can be simulated, so that simulation tests of different leakage areas can be completed through a scaled car body, which not only improves the test efficiency but also saves costs.

[0028] This embodiment also provides an air tightness test method, using the air tightness test scaled vehicle body as described above, the method comprises: Step 1: Get the static sealing index.

[0029] At present, static leakage model or constant pressure leakage model is generally used for static sealing test. The selection of the model is mainly based on the cavity size and leakage degree of the research object. This test uses the static leakage model to measure the static sealing index of the train. First, two holes with a diameter of 6 mm are opened at the lower end of each carriage. One is used to connect the air pump to pressurize the sealed cabin, and the other is connected to the pressure sensor to monitor the real-time changes in the pressure inside the car during the static air tightness test. The static air tightness test is divided into two parts. The first is to exchange gas between the sealed cabin and the outside world through the equivalent leakage hole on the door, and the second is to exchange gas between the sealed cabin and the outside world through the gap on the edge of the door.

[0030] After the test equipment is installed, start the static pressure relief test under the corresponding working conditions. Turn on the air pump, observe the real-time changes of the pressure curve on the computer terminal and store the pressure data, control the valve of the air pump, so that the air pressure curve in the sealed cabin rises at a relatively stable speed. When the air pressure rises to 3000Pa, close the air intake valve immediately. At this time, the air pressure inside the sealed cabin drops rapidly. As the pressure difference between the inside and outside of the cabin decreases, the rate of decrease of the air pressure in the sealed cabin gradually decreases. When the air pressure in the sealed cabin drops to about 0Pa, save the pressure change data on the computer terminal. The static pressure relief test uses a 1000Hz pressure sensor to record the time t when the pressure difference between the inside and outside of the sealed cabin drops from 2100Pa (Δp1) to 1000Pa (Δp2). According to the calculation formula of the static sealing index: , and repeat the operation by replacing the car door to obtain the static sealing index corresponding to different equivalent leakage areas.

[0031] Step 2: Conduct a static pressure relief test on the door.

[0032] The static pressure relief time of four different numbers of leakage holes under the above-mentioned hole pressure relief is obtained, and the static pressure relief test of door pressure relief is carried out based on these four times t. The specific operation is to change the size of the gap at the edge of the door by adjusting the preload of the screws on the door, and to equate the pressure relief time of the leakage hole with the pressure relief time of the door. When the pressure relief time is greater than the target time, increase the preload of the screw; when the pressure relief time is less than the target time, reduce the preload of the screw. Then repeat the above-mentioned pressurization steps, and record the time t when the pressure in the sealed cabin drops from 2100Pa to 1000Pa, thereby obtaining four door pressure relief working conditions. The time t of the door pressure relief is controlled to correspond one-to-one with the time of the hole pressure relief in order to better compare the dynamic sealing index obtained in the dynamic test under the two pressure relief methods.

[0033] Step three: perform a dynamic air tightness test.

[0034] After completing the static pressure relief test, the dynamic model ejection test is immediately carried out. First, the scaled vehicle body is fixed on the power trailer. The bottom of the scaled vehicle body is provided with a power trailer fixing hole to match the pins and the power trailer for fixing. There are six power trailer fixing holes, and three matching pins are set on each side to fasten and fix the power trailer to reduce the relative vibration between the power trailer and the scaled vehicle body. Turn on the switch of the data acquisition device at the rear of the vehicle. The device can store the pressure data obtained by all sensors on the scaled vehicle body during the dynamic air tightness test, and read the pressure data by connecting to the computer through the data transmission line after the ejection. The data acquisition device operates independently and can be charged during the static air tightness test of the scaled vehicle body. It is installed inside the vehicle body shell and fixed on the steel beam at the bottom of the vehicle body. It does not contact the sealed cabin, and the entire data acquisition device is packaged, which will not affect the changes in the pressure inside and outside the scaled vehicle body during operation. The setting of the vehicle body structure allows all test devices to be installed inside the vehicle body, so that the vehicle body maintains the appearance of the actual vehicle body, making the final dynamic air tightness index more real and effective.

[0035] When conducting a dynamic air tightness test on a scaled car body, a semi-cylindrical space can be set up to simulate a tunnel. According to a scale ratio of 1:20, the length of the test tunnel is 40 meters. After the power trailer is connected to the scaled car body, the dynamic air tightness test of the scaled car body is realized by launching the power trailer. The dynamic test includes three speed levels (120km / h, 140km / h and 160km / h). The dynamic air tightness of the train at different speeds is measured to study the influence of speed on the dynamic sealing index. In the past, the dynamic model test on air tightness research was mainly based on equivalent leakage holes, and the invention creatively designed a sealed cabin to ensure the air tightness of the train. There are many doors on subway trains. In the actual operation process, the gaps of the train doors will change all the time due to the impact of tunnel pressure waves, car body vibration and running speed, which will also lead to changes in the dynamic sealing index of the train. Therefore, the present invention is provided with doors in each carriage to simulate the influence of the doors under actual operation.

[0036] Step 4: Analysis.

[0037] By analyzing the dynamic air tightness test pressure data, the dynamic sealing index at a total of eight measuring points of the train under this operating condition was obtained, and compared with the static sealing index obtained from the corresponding static air tightness test, the ratio of the dynamic and static sealing indexes during the operation of the train and the change pattern of the ratio of the dynamic and static sealing indexes from the tail car to the head car were obtained.

[0038] Step 5: Separate each car (insert baffles into the slots at the car connection and seal them well). At this time, the pressure inside the head car, middle car and tail car is no longer the same, and they will not affect each other. Then perform a dynamic air tightness test according to step 3 to obtain the dynamic sealing index under the condition of car partition, and then compare the dynamic sealing index under the condition of car partition with the dynamic sealing index under the condition of car connection obtained in step 3 to analyze the impact of car connection and car partition on the train sealing index.

[0039] Through the above tests and analyses, we can study the relationship between the dynamic sealing index and the static sealing index of the train, and analyze the effects of carriage penetration and carriage partition, hole pressure relief and door pressure relief, and different speeds on the train sealing index.

[0040] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A scaled vehicle body for air tightness test, characterized in that: The invention comprises a plurality of carriages, each of which is provided with a sealed cabin, the sealed cabins of adjacent carriages are interconnected, and a partition structure is provided at the connection between the carriages to separate the inside of the sealed cabins of the carriages from each other; and each carriage is equipped with a pressure sensor.

2. The airtightness test scale vehicle body according to claim 1, characterized in that: The head and tail carriages are each equipped with 6 pressure sensors, and the middle carriage is equipped with 4 pressure sensors, forming multiple measuring points to analyze the changing pattern of the sealing index inside the carriage.

3. The airtightness test scale vehicle body according to claim 1 or 2, characterized in that: Each carriage includes an outer shell, which is fixed to the sealed cabin. A door is provided on the outer shell of each carriage. The door is fixed to the outer shell by screws. Different sealing performances can be obtained by adjusting the pre-tightening force of the screws. The door is detachably fixed to the outer shell and is provided with a leakage hole. Different equivalent leakage areas can be simulated by replacing doors with different leakage holes.

4. The airtightness test scale vehicle body according to claim 3, characterized in that: The pressure collection port of each pressure sensor forms a measuring point on the carriage. The measuring points inside and outside the carriage correspond to each other and are arranged on the right side of the train running direction. The outside pressure collection port extends from the inside of the car body shell to the outside, and the inside pressure collection port extends from the outside of the sealed cabin to the inside.

5. The airtightness test scale vehicle body according to claim 3, characterized in that: It also includes a data acquisition device and a power supply device. The pressure sensor body, the data acquisition device and the power supply device are installed in an internal equipment installation area arranged on the left side of the vehicle body's running direction. The internal equipment installation area is located in the avoidance space arranged at the bottom of the sealed cabin, so that all test devices are installed inside the outer shell.

6. The airtightness test scale vehicle body according to claim 5, characterized in that: A groove is provided between the shell and the sealed cabin for placing the wiring of the sensors. The data transmission lines of the sensors pass through the hollow beam at the bottom of the vehicle body, and are collected and stored in the data acquisition device at the rear of the vehicle.

7. The airtightness test scale vehicle body according to claim 5, characterized in that: The data acquisition device operates independently, is installed inside the vehicle body shell, and is fixed on the steel beam at the bottom of the vehicle body without contacting the sealed cabin.

8. An airtightness test method, characterized in that: Using the airtightness test scaled vehicle body as claimed in any one of claims 3 to 7, the method comprises: Step 1: Connect an air pump to each carriage; turn on the air pump to pressurize the sealed cabin. When the air pressure rises to a certain value, immediately close the air inlet valve. At this time, the air pressure inside the sealed cabin drops rapidly. Record the time t when the pressure difference between the inside and outside of the sealed cabin drops from Δp1 to Δp2, and then calculate the static sealing index according to the formula: , get the static sealing index, where is the static sealing index, Δp1 is the initial pressure difference between the inside and outside of the car, and Δp2 is the pressure difference between the inside and outside of the car after the pressure drops. Replace the car door and repeat the above operation to obtain the corresponding static sealing index under different equivalent leakage areas.

9. The airtightness test method according to claim 8, characterized in that: After obtaining the static sealing index corresponding to different equivalent leakage areas, the method also includes step 2: taking the static pressure relief time at different leakage holes as the benchmark, a static pressure relief test of door pressure relief is performed. The specific operation is to change the size of the gap at the edge of the door by adjusting the pre-tightening force of the screws on the door, and to use the door pressure relief time as the equivalent leakage hole pressure relief time. When the pressure relief time is greater than the target time, the pre-tightening force of the screws is increased; when the pressure relief time is less than the target time, the pre-tightening force of the screws is reduced. Then repeat the above pressurization steps, and record the time t when the pressure in the sealed cabin drops from p1 to p2, so that a variety of door pressure relief working conditions can be obtained; Step 3: Provide a semi-cylindrical space at the rear to simulate a tunnel; fix the scaled car body on the power trailer; launch the power trailer to perform dynamic air tightness test on the scaled car body, including measuring the dynamic air tightness of the car at different speeds, changing the gap size at the edge of the car door by adjusting the pre-tightening force of the screws on the car door to simulate the influence of the car door under actual running conditions, and obtaining the dynamic sealing index at the measuring point under different working conditions; Step 4: Compare the dynamic sealing index obtained in step 3 with the static sealing index obtained from the corresponding static air tightness test to obtain the ratio of the dynamic and static sealing indexes during the operation of the train and the change pattern of the ratio of the dynamic and static sealing indexes from the tail car to the head car.

10. The airtightness test method according to claim 9, characterized in that: The method also includes step five: partitioning each carriage, and then conducting a dynamic air tightness test according to step three to obtain a dynamic sealing index under the condition of partitioned carriages, and then comparing the dynamic sealing index under the condition of connected carriages obtained in step three to analyze the effects of connected carriages and carriage partitions on the sealing index of the train.

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