Subway Passenger Compartment Air Purification System and Method

Abstract

The present invention discloses a subway passenger compartment air purification system and method. The system includes at least one wind speed sensor installed at the end section of each carriage, an environmental tester installed in each carriage, multiple purification devices spaced and movably installed on the top of the carriage along the length of the carriage, and a data processing controller. The data processing controller calculates an empirical wind speed value based on the position information of the wind speed sensor, calculates an empirical wind speed value of a characteristic point based on the position information of a characteristic point, corrects the empirical wind speed value of the characteristic point based on the wind speed data and the empirical wind speed value to obtain a corrected characteristic point wind speed. The system also controls the activation or movement and activation of multiple purification devices in the corresponding carriage based on the empirical wind speed value of the characteristic point, the corrected characteristic point wind speed, and environmental information. The present invention improves the purification range and purification effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of air purification, and in particular relates to a subway passenger compartment air purification system and method utilizing through-drafts. Background Art

[0002] Studies have shown that droplet aerosols released by the human body are important carriers of infectious diseases, and aerosols suspended for a long time in a relatively closed environment have the potential to spread viruses.

[0003] Subway trains, as a crucial form of public transportation for urban rail transit, feature high passenger density, a closed, poorly ventilated environment, and insufficient fresh air supply. This leads to an increase in harmful substances in the microclimate within the train compartments, making them highly susceptible to the widespread spread of infectious diseases. Furthermore, due to the imperfect airtightness of subway trains, when the train-tunnel connection is established, fluctuating pressure waves within the tunnel can enter the interior of the train compartments through the fresh air valves of the air conditioning units and the connections between the train compartments, causing pressure fluctuations within the compartments. The resulting pressure differential between the front and rear creates a draft from front to back, creating a particularly strong drafty sensation at the connections. Studies have shown that longitudinal airflow increases the spread of droplets, further increasing the risk of cross-infection. Numerous cases of close-contact infection have been reported in aircraft cabins and high-speed trains. Therefore, there is an urgent need to explore efficient, large-scale disinfection and purification technologies for the coexistence of humans and machines.

[0004] Common air pollutants in subway cars include aromatic compounds such as formaldehyde, total volatile organic compounds (TVOCs), bacteria, viruses, and odors (inorganic pollutants such as NH3, H2S, and CH3SH). Low-temperature plasma is a commonly used air purification technology in subways, characterized by a high dynamic removal rate and a wide range of pollutant removal. It is generally embedded in the air conditioning unit above the train, ionizing the air around the air outlet through high voltage and purifying the air along the air flow in the duct. However, plasma exhibits a highly excited and unstable state, and its activity decays rapidly, so it cannot effectively purify the air inside subway passenger rooms, and its disinfection range is limited. Summary of the Invention

[0005] The purpose of the present invention is to provide a subway passenger compartment air purification system and method, which controls the spatial layout of purification equipment according to the characteristics of through-drafts, so as to solve the problem that existing air purification technology cannot effectively purify subway passenger compartments and has a limited purification range.

[0006] The present invention solves the above technical problems through the following technical solutions: a subway passenger compartment air purification system, comprising:

[0007] At least one wind speed sensor is provided at the end section of each carriage, the wind speed sensor being used to collect wind speed data at the front end of the corresponding carriage; the front end of the carriage refers to the end of the carriage in the same direction of travel;

[0008] An environmental tester is installed in each carriage, and is used to collect environmental information in the corresponding carriage;

[0009] A plurality of purification devices are installed on the top of each carriage, and the plurality of purification devices are arranged movably and spaced apart along the length of the carriage;

[0010] A data processing controller is provided in each carriage, and is used to:

[0011] Obtain wind speed data at the front end of the corresponding carriage collected by a wind speed sensor, obtain environmental information in the corresponding carriage, obtain position information of the wind speed sensor in a coordinate system, and obtain position information of a feature point on an XY plane of the coordinate system, wherein the coordinate system has a length direction of the corresponding carriage as a Z axis and a cross section of the front end of the carriage as an XY plane; calculate a wind speed empirical value based on the position information of the wind speed sensor, calculate a feature point wind speed empirical value based on the position information of the feature point, correct the feature point wind speed empirical value based on the wind speed data and the wind speed empirical value to obtain a corrected feature point wind speed; and perform startup control or movement and startup control on multiple purification devices in the corresponding carriage based on the feature point wind speed empirical value, the corrected feature point wind speed, and the environmental information;

[0012] The characteristic point reflects the maximum wind speed on the XY plane.

[0013] Furthermore, the wind speed sensor is arranged on one side of the end section of the carriage, 1.1m away from the carriage floor.

[0014] Furthermore, a plurality of the purification devices are arranged at equal intervals on the top of the corresponding carriage.

[0015] Furthermore, the purification equipment is a plasma-activated water purification device, which includes an atomizer, electrodes arranged in the atomizer, atomizing nozzles arranged on both sides of the atomizer, an electric pulley arranged on the atomizer, and a control module connected to the electrodes, the electric pulley and the electric control valve arranged on the atomizing nozzle; the atomizer is filled with dielectric; and the plasma-activated water purification device is movably arranged on the slide rail on the top of the carriage via the electric pulley.

[0016] Preferably, radar modules connected to the control module are provided at both ends of the atomizer and the slide rail.

[0017] Based on the same inventive concept, the present invention also provides a method for purifying air in a subway passenger compartment, comprising the following steps:

[0018] Obtain wind speed data collected by a wind speed sensor at the front end of each carriage, where the front end of the carriage refers to the end of the carriage in the same direction of travel; and obtain environmental information within each carriage;

[0019] Obtaining position information of the wind speed sensor in a coordinate system, and calculating an empirical wind speed value based on the position information of the wind speed sensor; the coordinate system has the Z axis corresponding to the length direction of the carriage and the front section of the carriage as the XY plane;

[0020] Obtaining the position information of the feature point on the XY plane, and calculating the wind speed empirical value of the feature point based on the position information of the feature point; the feature point reflects the maximum wind speed value on the XY plane;

[0021] Correct the wind speed experience value of the feature point according to the wind speed data and the wind speed experience value to obtain the corrected wind speed of the feature point;

[0022] Based on the characteristic point wind speed experience value, the corrected characteristic point wind speed and the environmental information, multiple purification devices in the corresponding compartment are started and controlled or moved and started, wherein the multiple purification devices are spaced along the length direction of the compartment and movably arranged on the top of the compartment.

[0023] Furthermore, when the coordinate system takes the carriage floor corresponding to the front section of the carriage as the X-axis and the longitudinal perpendicular bisector of the front section of the carriage as the Y-axis, the calculation formula of the wind speed empirical value of the wind speed sensor is:

[0024]

[0025]

[0026]

[0027] in, Indicates the wind speed empirical value corresponding to the coordinates of the wind speed sensor in the coordinate system (x, y);

[0028] It represents the average value of the maximum wind speed at any point on the horizontal line at y = 1.1m in the coordinate system;

[0029] It represents the average value of the maximum wind speed at any point on the vertical perpendicular bisector at x=0 in the coordinate system; C1, C2, C3, and C4 are all coefficients, which are determined by nonlinear curve fitting from the known points in the coordinate system; C5 and C6 are both coefficients, which are calculated by the Lagrange interpolation formula from the known points in the coordinate system; C0 is the normalization processing coefficient.

[0030] Furthermore, when the coordinate system takes the carriage floor corresponding to the front section of the carriage as the X-axis, the longitudinal perpendicular bisector of the front section of the carriage as the Y-axis, and the X-coordinate value of the feature point in the coordinate system is 0 (that is, the feature point is on the Y-axis of the coordinate system), the calculation formula of the wind speed empirical value of the feature point is:

[0031]

[0032] in, It represents the empirical wind speed value of the feature point when the X coordinate value of the feature point in the coordinate system is 0. y is the Y coordinate value of the feature point in the coordinate system. C1, C2, C3, and C4 are all coefficients, which are obtained by nonlinear curve fitting based on the known points in the coordinate system.

[0033] Preferably, the Y coordinate value of the feature point in the coordinate system is 1.5.

[0034] Furthermore, when the coordinate system takes the carriage floor corresponding to the front section of the carriage as the X-axis and the longitudinal perpendicular bisector of the front section of the carriage as the Y-axis, the corrected characteristic point wind speed is:

[0035]

[0036]

[0037] in, is the corrected wind speed of the feature point when the X coordinate value of the feature point in the coordinate system is 0, V is the wind speed experience value of the feature point before correction when the X coordinate value of the feature point in the coordinate system is 0. wind实 (t0) is the wind speed data collected by the wind speed sensor at the front end of the carriage at time t0, t0 is the sampling time of the wind speed sensor, is the empirical wind speed value corresponding to the coordinate of the wind speed sensor in the coordinate system is (x, y).

[0038] Furthermore, the start-up or movement and start-up control process of multiple purification devices in each carriage is as follows:

[0039] When the corrected characteristic point wind speed is greater than or equal to the characteristic point wind speed experience value, multiple purification devices are controlled to move sequentially in the direction opposite to the running direction, and the devices are started when the movement stops; sequentially means that the purification devices are moved in the order opposite to the running direction;

[0040] When the corrected characteristic point wind speed is less than the characteristic point wind speed experience value, and the measured value of the carbon dioxide concentration is greater than or equal to the set value of the carbon dioxide concentration, only multiple purification devices are controlled to start;

[0041] When the corrected characteristic point wind speed is less than the characteristic point wind speed experience value, and the measured temperature value is greater than or equal to the temperature setting value, only multiple purification devices are controlled to start.

[0042] Preferably, the specific implementation process of controlling multiple purification devices to move in a direction opposite to the running direction in sequence and starting the device when the movement stops is:

[0043] Assume that in the opposite direction of operation, multiple purification devices are numbered as the first purification device, the second purification device, ..., the Nth purification device, where N is the number of purification devices in each carriage; the first purification device refers to the purification device located at the front end of the carriage, and the curve of the change of real-time wind speed data over time is defined as

[0044] When the corrected characteristic point wind speed is greater than or equal to the characteristic point wind speed experience value, at time 0, the first purification device at a set distance from the end is started; during the time period of 0 to Δt, the second purification device moves in the opposite direction to the running direction, and the moving distance of the second purification device is At time Δt, the second purification device stops moving and starts; the time corresponding to the corrected characteristic point wind speed ≥ the characteristic point wind speed empirical value is time 0, and Δt is the interval between the starts of adjacent purification devices;

[0045] During the time period of Δt to 2Δt, the third purification device moves in the opposite direction to the running direction, and the moving distance of the third purification device is At time 2Δt, the third purification device stops moving and starts;

[0046] Similarly, during the time period of (N-2)Δt to (N-1)Δt, the Nth purification device moves in the direction opposite to the running direction, and the moving distance of the Nth purification device is At time (N-1)Δt, the Nth purification device stops moving and starts.

[0047] Preferably, when the distance between adjacent purification devices is less than a set distance value, the adjacent purification devices move in the same direction at the same speed.

[0048] Beneficial effects

[0049] Compared with the prior art, the advantages of the present invention are:

[0050] The present invention provides a subway passenger compartment air purification system and method, which adaptively moves and time-controlledly starts multiple purification devices in the compartment based on characteristic point wind speed experience values, corrected characteristic point wind speeds, and environmental information. The spatial positions of multiple devices are controlled by utilizing the wind speed characteristics of the subway compartment through-draft. The natural wind force of the through-draft is utilized to achieve long-distance transmission of purified substances from the devices, thereby achieving comprehensive coverage of the compartment purification range, greatly improving the purification range and purification effect, and also achieving energy-saving effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 Schematic diagram of the position of the wind speed sensor in the coordinate system in the first embodiment of the present invention;

[0053] Figure 2 This is a side view of the arrangement of the subway passenger compartment air purification system in Example 1 of the present invention;

[0054] Figure 3 1. It is a top view of the arrangement of the subway passenger compartment air purification system in the first embodiment of the present invention;

[0055] Figure 4 Schematic diagram of the structure of the plasma activated water purification device in Example 1 of the present invention;

[0056] Figure 5 This is a schematic diagram of a Type B subway in Example 1 of the present invention;

[0057] Figure 6 This is a diagram showing the results of a ribbon experiment during subway acceleration in Example 1 of the present invention;

[0058] Figure 7 This is a cross-sectional view of a test unit in a certain running direction of a subway in the first embodiment of the present invention;

[0059] Figure 8 is a position diagram of six measuring points in the coordinate system in the first embodiment of the present invention;

[0060] Figure 9 This is a statistical diagram of the maximum values of 6 measuring points in 9 intervals in Example 1 of the present invention;

[0061] Figure 10 This is a schematic diagram of a real vehicle test for determining the Δt value in the first embodiment of the present invention;

[0062] Figure 11 is a curve showing the change of real-time wind speed data over time in the first embodiment of the present invention;

[0063] Figure 12 This is a flow chart of the subway passenger compartment air purification method in Example 2 of the present invention. DETAILED DESCRIPTION

[0064] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0065] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0066] Example 1:

[0067] The present embodiment provides a subway passenger compartment air purification system, comprising at least one wind speed sensor arranged at the end section of each carriage, an environmental tester arranged in each carriage, a plurality of purification devices spaced and movably arranged on the top of the carriage along the length direction of the carriage, and a data processing controller.

[0068] Each passenger car has two front and rear connections with its adjacent cars, meaning it has two end sections. Each car end section is equipped with at least one wind speed sensor. During air purification, only wind speed data collected by the wind speed sensor at the front end of the car is collected. The front end of the car refers to the end of the car that is in the same direction of subway travel. The installation of a wind speed sensor at each car end section facilitates the collection of wind speed data during reciprocating subway operation. That is, when the subway travels in the reverse direction, the front end of the car becomes the rear end of the car, and the rear end of the car becomes the front end of the car. When multiple wind speed sensors are installed in each car end section, the wind speed data is averaged from the wind speed data collected by these sensors.

[0069] In this embodiment, in order not to affect the normal passage of passengers and reduce the probability of passengers damaging the wind speed sensor, the wind speed sensor in the end section of each carriage is installed on one side of the carriage end section, 1.1m away from the carriage floor. Figure 1 As shown, P0 is the position of the wind speed sensor in the coordinate system or the front section of the carriage or the test section.

[0070] The environmental tester in each carriage includes a carbon dioxide sensor and a temperature and humidity sensor. The environmental information collected by the environmental tester includes the carbon dioxide and temperature and humidity in the corresponding carriage. In this embodiment, the environmental tester is located in the middle of the carriage, such as Figure 2 and 3As shown in the figure, 1 is the data processing controller, 2 is the environmental tester, 21 is the carbon dioxide sensor, 22 is the temperature and humidity sensor, 3 is the radar module, 4 is the slide rail, and 5 is the purification equipment. The number on the side of the purification equipment indicates the purification equipment number, that is, 1 corresponds to the first purification equipment, 2 corresponds to the second purification equipment, 3 corresponds to the third purification equipment, 4 corresponds to the fourth purification equipment, 6 is the rear end connection of the carriage, and 7 is the seat. The gas exhaled by people in a relatively closed space has a certain temperature, and CO2 and water vapor also have a certain proportion. Therefore, environmental information can indirectly reflect the local droplet concentration generated by human respiratory activities (breathing, talking, coughing, sneezing, etc.), and also serves as one of the judgment conditions for controlling the purification equipment.

[0071] Each carriage has multiple purification devices, such as Figure 3 As shown, multiple purification devices 5 are movably arranged on the top of the carriage at intervals along the length of the carriage. In this embodiment, multiple purification devices 5 are evenly spaced on the top of the corresponding carriages through slide rails 4, and the purification devices 5 are plasma activated water purification devices.

[0072] The plasma-activated water purification device includes a plasma-activated water generator and an atomizer. The generator is built into the atomizer and activates the liquid through underwater discharge using dielectric barrier discharge (DBD) technology, which is then spread through the atomizer. The entire device is installed on a slide rail on the top of the subway car, 2m above the ground.

[0073] In this embodiment, the plasma activated water generator is an electrode. Figure 4 As shown, the plasma-activated water purification device includes an atomizer 51, an electrode 52 disposed in the atomizer, atomizing nozzles 53 disposed at both ends of the atomizer 51, an electric pulley 54 disposed on the atomizer 51, and a control module connected to the electrode 52, the electric pulley 54, and the electric control valve disposed on the atomizing nozzle 53; the atomizer 51 is filled with a dielectric 55; and the plasma-activated water purification device is movably mounted on a slide rail 4 on the top of the carriage via the electric pulley 54.

[0074] When the device is turned on, the electrode 52 uses DBD (dielectric barrier discharge) technology to discharge in the dielectric 55 to activate the liquid dielectric 55 and generate plasma-active water atomized particles, and then controls the electric control valve to open and spray the plasma-active water atomized particles through the atomizing nozzle to achieve air purification.

[0075] Plasma-activated water (PAM) is a water solution rich in various active substances produced by low-temperature plasma treatment. The RONS contained in PAM is considered a key component in destroying bacteria. It includes both long-lived acidic substances (H2O2, NO2-, NO3-) and short-lived oxygen atoms or radicals (OH, HOO, O2-). By leveraging the periodic real-time wind speed of subway through-drafts and combining it with empirical formulas derived from experiments, and by using atomizing nozzles to adaptively and timedly apply PAM at variable distances, it is possible to achieve large-scale purification of subway passenger compartments within the limited activity of the plasma-activated water, achieving both high efficiency and energy conservation.

[0076] In this embodiment, a radar module 3 connected to the control module is provided on the atomizer 51 and at both ends of the slide rail 4. The radar module 3 is used to obtain the position information of the purification equipment 5 to prevent collisions between adjacent devices and movement of the equipment to extreme positions.

[0077] The data processing controller 1 of each carriage is located at the lower end of the carriage. Figure 2 As shown. The data processing controller 1 is used to: obtain the wind speed data at the front end of the car collected by the wind speed sensor, obtain the environmental information in the car collected by the environmental tester 2, obtain the position information of the wind speed sensor in the coordinate system, and obtain the position information of the feature point in the XY plane of the coordinate system; calculate the wind speed experience value according to the position information of the wind speed sensor using formula (3), calculate the feature point wind speed experience value according to formula (1) according to the position information of the feature point, correct the feature point wind speed experience value according to the wind speed data of the wind speed sensor and the wind speed experience value to obtain the corrected feature point wind speed; and perform startup control or movement and startup control on multiple purification devices 5 in the corresponding car according to the feature point wind speed experience value, the corrected feature point wind speed and the environmental information.

[0078] The coordinate system takes the length direction of the car as the Z axis, the front section of the car as the XY plane, and the characteristic point reflects the maximum wind speed on the XY plane. In this embodiment, the coordinate system takes the car floor corresponding to the front section of the car as the X axis, and the vertical bisector of the front section of the car as the Y axis, such as Figure 1 shown.

[0079] like Figure 3 As shown, in the opposite direction of operation, multiple purification devices 5 are sequentially numbered as the first purification device, the second purification device, ..., the Nth purification device, where N is the number of purification devices in each carriage, and the first purification device refers to the purification device located at the front end of the carriage. The startup or movement and startup control process of multiple purification devices in each carriage is as follows:

[0080] (1) When the corrected characteristic point wind speed is greater than or equal to the characteristic point wind speed experience value, at time 0, the first purification device at a set distance from the end is directly started and does not move; during the time period from 0 to Δt, the second purification device moves in the direction opposite to the running direction, and the moving distance of the second purification device is The second purification device stops moving and starts at time Δt, which is the same as the wind flow distance. The time corresponding to the corrected characteristic point wind speed ≥ the characteristic point wind speed empirical value is time 0, and Δt is the interval between the startups of adjacent purification devices.

[0081] During the time period of Δt to 2Δt, the third purification device moves in the opposite direction to the running direction, and the moving distance of the third purification device is The third purification device stops moving and starts at 2Δt, which is the same as the wind flow distance;

[0082] Similarly, during the time period of (N-2)Δt to (N-1)Δt, the Nth purification device moves in the direction opposite to the running direction, and the moving distance of the Nth purification device is The same as the flow distance of the wind, at time (N-1)Δt, the Nth purification device stops moving and starts.

[0083] In this embodiment, the curve of real-time wind speed data changing over time is defined as like Figure 11 The curve shown in the figure is a wind speed data collected every 1s, and the change curve is analyzed in each Δt time period. Make points This determines the movement speed or distance of the purification equipment, ensuring it remains consistent with the wind speed or distance of the through-draft. Here, i = 1, 2, …, (N-1). The activation interval Δt is determined by the duration of the through-draft flow within the vehicle and the number of purification devices.

[0084] (2) When the corrected characteristic point wind speed is less than the characteristic point wind speed experience value, and the measured value of the carbon dioxide concentration is greater than or equal to the set value of the carbon dioxide concentration, only the plurality of purification devices are controlled to start, and the purification devices do not move.

[0085] In this embodiment, the set value of carbon dioxide concentration is 2000 ppm.

[0086] (3) When the corrected characteristic point wind speed is less than the characteristic point wind speed empirical value, and the measured temperature value is greater than or equal to the temperature setting value, only the plurality of purification devices are controlled to start, and the purification devices do not move. In this embodiment, the temperature setting value is 28°C.

[0087] This embodiment takes the B-type subway M2 car as an example. Through the subway through-draft actual vehicle test, the position information and empirical formula of the characteristic point of the through-draft wind speed in the coordinate system are determined. The wind speed empirical value of the wind speed sensor and the characteristic point wind speed empirical value are calculated based on the empirical formula.

[0088] Type B subway Figure 5 As shown, the test system includes a subway train entity unit, a subway tunnel entity unit, a test unit, a test point arrangement unit and a data processing controller.

[0089] Among them, the subway train entity unit runs in the subway tunnel entity unit; the test unit consists of multiple test sections (i.e., the car end section, where the wind speed sensor is located), and the test section is set at the connection between the two ends of the M2 car; the measurement point arrangement unit includes multiple experimental measurement points, environmental testers and fastening devices, etc. Multiple experimental measurement points are arranged in the test unit (i.e., arranged on the test section), each experimental measurement point mainly includes a wind speed sensor, and the environmental tester is set in the car (such as Figure 3 The fastening device is used to fix the wind speed sensor and the environmental detector, and the fastening device includes a clamp, a spherical metal cage, screws, etc. The data processing controller is used to obtain the relevant data collected by the wind speed sensor and the environmental detector and process them. The data processing controller mainly includes an integrated controller, a data cable, and equipment supporting operating software.

[0090] In the actual vehicle test, ribbons 9 were added and hung on the handrails 8 around the doors of the M2 carriage and on the top wall. The direction of the through-draft was determined by the inclination of the ribbons 9. Along the train's running direction, as the train started to accelerate, the inclination of the ribbons 9 deviated from the train's running direction, indicating that when the train accelerated, a through-draft would be generated along the train's running direction from front to back. Figure 6 As shown, 7 is a seat, 8 is a handrail, 9 is a ribbon, 10 is a door, and 11 is a car wall. At the same time, it was found that the inclination angle of the ribbon 9 at the door 10 near the front end of the car (referring to the end of the car in the same direction as the train's running direction) is larger than that in the middle of the car. In addition to being affected by the through-draft caused by the gap at the connection, the ribbon 9 in the middle of the car is also affected by the air supply from the air duct in the car, the door gap, etc., and the airflow direction is relatively disordered. Therefore, the test unit is set at the connection between the two ends of the car. In order to take into account the reciprocating operation of the subway train, a test section is arranged at each connection at both ends of the car, and the wind speed data at the front end of the car is input into the integrated controller as the basis for judgment. The section layout of the test unit under a certain running direction of the subway is as follows Figure 7 As shown, 12 is the front section of the carriage, which is also the wind speed inlet, and 13 is the wind speed outlet.

[0091] In this embodiment, six experimental measurement points (P1 to P6) were arranged on the test section at the front end of the M2 carriage. Referring to the requirements for airflow velocity testing and thermal comfort measurement point arrangement in the EN standard BSEN14750-2:2006 "Railway applications - Air conditioning for urban and suburban rolling stock - Part 2: Type tests" and GB / T 33193.2-2016 "Railway vehicle air conditioning: Part 2: Type tests," and taking into account the actual dimensions of the B-type subway car and the human body dimensions of Chinese adults in GB / T 10000-1988, this experiment adjusted the 0.1m height from the ground to 0.3m, considering that the height is low and uncontrollable, and is affected by factors such as rod turbulence. In addition, to better simulate the longitudinal distribution of wind speed, the number of measurement points in the longitudinal direction was considered to be increased. Based on this, four experimental measuring points are arranged on the vertical bisector of the test section at heights of 0.3m (P4), 0.7m (P3), 1.1m (P2), and 1.7m (P1) above the ground, and three measuring points (P6, P2, and P5) are evenly arranged at the four equal points at the horizontal position of 1.1m. Six measuring points are arranged on the entire section, as shown in the following figure. Figure 8 These measurement points cover the head, shoulders, and legs of an adult standing, and the head and calves of a seated person. The cross-shaped arrangement of the six measurement points on the plane can collect more wind speed information on the section, so as to find the location of the plane distribution feature points of the through-draft.

[0092] Taking the Changsha Metro Line 5 section between Wanjiali Square and Maozhutang as an example, wind speed test data from various test points show that through-draft wind speed exhibits a certain periodicity as the train starts and stops. Wind speed increases as the train accelerates, decreases as the train decelerates, and remains turbulent during stops, repeating a repetitive cycle. Preliminary data analysis revealed that the maximum through-draft wind speed occurs during the train's acceleration period.

[0093] The data collected continuously (including stops) between the 10 stations (9 sections in total) between Wanjiali Square and Maozhutang are processed, and the maximum value of each measuring point in these 9 sections is statistically calculated, and the following is drawn: Figure 9 The line chart shown, Figure 9 The horizontal axis represents the 9 sections from Wanjiali Square to Maozhutang, and the vertical axis represents the maximum wind speed at different measuring points.

[0094] right Figure 9A longitudinal analysis reveals significant differences in the maximum wind speed values at different measuring points within the same section. Vertically, from high to low (P1 to P4), the maximum values first increase and then decrease. This suggests that the vertical wind speed at points P1-P3 increases, while that at points P3-P4 decreases. Furthermore, the wind speed values at points P3 and P4, which are close to the ground, are higher. Horizontally, it's clear from sections 2 to 5 that the maximum values at points P5 and P6 are essentially the same and smaller than the value at the midpoint, P2. This suggests that the horizontal distribution of the wind speed across this section is symmetrical, with a high value in the middle and low values at both ends.

[0095] Therefore, the present invention uses the wind speed data of the points on the vertical bisector of the test section as the basis for threshold judgment. According to the size data in "Chinese Adult Human Body Dimensions" of "GB_T10000-1988", the height of the human mouth y = 1.5m is defined as the characteristic point reflecting the wind speed. On the one hand, the wind speed of the characteristic point covers most of the maximum wind speed values. On the other hand, the wind speed of the characteristic point can effectively purify the concentration of pollutants in the human head area as the judgment condition for the control of the purification equipment. When the coordinate system takes the floor of the car where the wind speed sensor is located as the X-axis and the vertical bisector of the section where the wind speed sensor is located as the Y-axis (such as Figure 1 and 8 As shown), the coordinate position of the feature point in the coordinate system is (0,1.5).

[0096] In order to comprehensively consider the influence of various factors, the calculation Figure 9 The average value of the maximum wind speed (Vwind_max) of the six measuring points (P1 to P6) in the nine intervals is recorded as (i=1, 2, 3, 4, 5, 6, indicating the measurement point number), the unit is m / s, and the calculation is

[0097] Along the direction of train movement, take the ground of the test section as the x-axis direction, with the right direction as positive, the vertical perpendicular bisector as the y-axis direction, with the upward direction as positive, and use the right-hand rule to determine the z-axis (i.e. the length direction of the carriage is the z-axis). The xy plane represents the location information of the measuring point, and the z-axis abstractly represents the wind speed of the hallway, such as Figure 8 shown.

[0098] The four points P1, P2, P3, and P4 on the vertical bisector of the test section are measured using spatial coordinates (x (i) ,y (i) ,z (i) ) represents (i=1, 2, 3, 4), where z (i) Equivalent to the maximum wind speed at this point The coordinates of point P1 are The coordinates of point P2 are The coordinates of point P3 are The coordinates of point P4 are Constructor form:

[0099]

[0100] Among them, C1, C2, C3, and C4 are unknown coefficients; y is the corresponding Y coordinate value in the established coordinate system.

[0101] In MATLAB, use lsqcurvefit() to perform nonlinear curve fitting. The values of the coefficients to be determined are: C1 = 0.4870, C2 = -1.0152, C3 = 1.1995, C4 = 1.7618. The curve equation is As the first empirical formula, the specific expression is:

[0102]

[0103] Where: It represents the average value of the maximum wind speed at x=0, that is, at any point on the vertical bisector of the test section (y-axis). This value is an empirical value of wind speed, not an accurate value. The size of this value depends on the experimental measured data, and the unit is m / s; y represents the y-coordinate value corresponding to any point on the y-axis, and the unit is m.

[0104] According to formula (1), the wind speed empirical value of the characteristic point (0,1.5) is 1.89m / s, which is recorded as This value serves as one of the threshold conditions for purification equipment control.

[0105] The spatial coordinates of the three points P5, P2, and P6 arranged horizontally at 1.1m are also expressed as (i=5, 2, 6), the coordinates of point P5 are The coordinates of point P2 are The coordinates of point P6 are Based on the coordinate system of this embodiment, let y=1.1 at points P5, P2, and P6. Use the Lagrange interpolation formula to fit The equation of the curve that changes with the x-axis is expressed as As the second empirical formula, the three-point difference formula is expressed as:

[0106]

[0107] Calculate and simplify to get:

[0108]

[0109] Where: It represents the average value of the maximum wind speed at any point on the horizontal line at y = 1.1m in the test section. Similarly, this value is only used as an empirical value of wind speed, and the unit is m / s; x represents the x-coordinate value corresponding to any point on the horizontal line at y = 1.1m, and the unit is m. C5 is -0.0083 and C6 is 2.17.

[0110] The plane distribution curve of wind speed on the test section is defined as According to the above two empirical formulas (1) and (2), the curve expression is constructed:

[0111]

[0112] Among them, C0 is the normalization coefficient, calculated as

[0113] Substituting into formulas (1) and (2) we get:

[0114]

[0115] Calculate the wind speed experience value of the wind speed sensor according to formula (3).

[0116] There are multiple purification devices installed on the top of each subway car, and the multiple purification devices in each car are turned on in sequence (the sequence here refers to the flow direction of the through-air, which is opposite to the running direction). Figure 3 As shown in Figure 1, the opening interval time Δt is closely related to the speed of the through-wind in the car. At the same time, the through-wind speed at the two ends of the same direction of the M2 car of a certain line was tested. The front connection was recorded as Section 1 and the rear connection was recorded as Section 2. The test sections are as follows: Figure 10 (a), from Figure 10 The direction of the human eye indicated in (a) is looking towards the test section, and the side view of the corresponding measurement point arrangement is as follows Figure 10 (b).

[0117] The data of the 1#~5# measuring points in the two test sections 1 and 2 of a certain test are statistically analyzed and plotted. Figure 11 Line graph, where the solid line corresponds to the data of the measuring point in section 1, and the dashed line corresponds to the data of the measuring point in section 2. The five graphs from top to bottom correspond to measuring points 1#, 2#, 3#, 4#, and 5#, respectively. The y values of points 1#, 2#, and 3# in the coordinate system are 1.7m, 1.1m, and 0.3m, respectively. Figure 11 The horizontal axis of each graph represents the serial number value of the time within the test period. The test period is 15 minutes, and each second corresponds to a time serial number (15 minutes corresponds to 900 time serial numbers). The sampling frequency is 1 Hz, so the horizontal axis corresponds to 0 to 900 and is a dimensionless quantity. The vertical axis represents the wind speed in m / s.

[0118] from Figure 11 It is clear that there is a certain lag between the time when the two curves reach their maximum values. The wind speed in Section 1 reaches its maximum value earlier than that in Section 2, which also reflects that the through-draft flows from front to back at a certain speed. Statistical calculation of the time difference between the maximum values shows that the lag time ranges from 34s to 42s. Considering that four purification devices will be installed in each carriage in the future, the lag time is divided into four equal parts, with Δt being ≈ 9-11s.

[0119] Example 2:

[0120] like Figure 12 As shown, this embodiment also provides a method for purifying air in a subway passenger compartment, comprising the following steps:

[0121] Step 1: Obtain wind speed data at the front end of each carriage collected by the wind speed sensor

[0122] Each passenger car has two front and rear connections with its adjacent cars, meaning it has two end sections. Each car end section is equipped with at least one wind speed sensor. During air purification, only wind speed data collected by the wind speed sensor at the front end of the car is collected. The front end of the car refers to the end of the car that is in the same direction of subway travel. The installation of a wind speed sensor at each car end section facilitates the collection of wind speed data during reciprocating subway operation. That is, when the subway travels in the reverse direction, the front end of the car becomes the rear end of the car, and the rear end of the car becomes the front end of the car. When multiple wind speed sensors are installed in each car end section, the wind speed data is averaged from the wind speed data collected by these sensors.

[0123] Step 2: Obtain the environmental information in each carriage.

[0124] The environmental tester in each carriage includes a carbon dioxide sensor and a temperature and humidity sensor. The environmental information collected by the environmental tester includes the carbon dioxide and temperature and humidity in the corresponding carriage. In this embodiment, the environmental tester is located in the middle of the carriage, such as Figure 2 and 3 shown.

[0125] Step 3: Obtain the position information of the wind speed sensor in the coordinate system, and calculate the wind speed experience value based on the position information of the wind speed sensor.

[0126] In this embodiment, the coordinate system is based on the Z axis corresponding to the length of the carriage, the X axis corresponding to the carriage floor at the front end section of the carriage, and the Y axis with the vertical bisector of the longitudinal direction of the front end section of the carriage. Figure 1 and 8In order to not affect the normal passage of passengers and reduce the probability of passengers damaging the wind speed sensors, the wind speed sensors at both ends of each carriage are installed on one side of the front section of the carriage and 1.1m away from the carriage floor. That is, the position coordinates of the wind speed sensors in the coordinate system are (x,1.1).

[0127] The size of the connection of the M2 carriage of the B-type subway is 1320*1900mm, so the position coordinates of the wind speed sensor in the coordinate system are (-6.6, 1.1), and the unit is m. According to the position coordinates of the wind speed sensor (-6.6, 1.1), the wind speed empirical value of the wind speed sensor calculated by formula (3) in Example 1 is It is 1.01m / s.

[0128] Step 4: Obtain the position information of the feature point on the XY plane, and calculate the wind speed experience value of the feature point based on the position information of the feature point.

[0129] According to the experiment in Example 1, the position coordinates of the feature point are (0, y) and specifically (0, 1.5). According to the position coordinates (0, 1.5) of the feature point in the coordinate system, the wind speed empirical value of the feature point calculated by formula (1) in Example 1 is It is 1.89m / s.

[0130] Step 5: Correct the characteristic point wind speed empirical value according to the wind speed data of the wind speed sensor and the wind speed empirical value to obtain the corrected characteristic point wind speed.

[0131] Since the characteristic point reflecting the wind speed is defined at a position of 1.5 m on the vertical perpendicular bisector, the coordinates of the intersection point of the two empirical formulas (1) and (2) obtained in Example 1 are (0, 1.1). Therefore, if the real-time wind speed data of the wind speed sensor is to be extrapolated to the wind speed of the characteristic point, the wind speed difference is calculated based on the wind speed data and the wind speed empirical value, specifically:

[0132]

[0133] Where Δv is the wind speed difference, V wind_实 (t0) is the wind speed data collected by the wind speed sensor at the front end of the carriage at time t0, t0 is the sampling time of the wind speed sensor, is the wind speed empirical value calculated by the wind speed sensor using formula (3).

[0134] The corrected wind speed of the characteristic point is:

[0135]

[0136] in, is the corrected wind speed of the characteristic point, is the empirical value of wind speed at the feature point, and the Y value corresponding to the feature point is 1.5.

[0137] Step 6: Based on the characteristic point wind speed experience value, the corrected characteristic point wind speed and the environmental information, multiple purification devices in the corresponding compartment are started or moved and started, wherein the multiple purification devices are spaced along the length direction of the compartment and movably arranged on the top of the compartment.

[0138] like Figure 3 As shown, in the opposite direction of travel, multiple purification devices are sequentially numbered as the first purification device, the second purification device, ..., the Nth purification device, where N is the number of purification devices in each carriage. In this embodiment, N = 4. The basic dimensions of a Type B carriage are length * width * height: 19 * 2.8 * 3.8 meters, and the quarter-sections are spaced 4.75 meters apart.

[0139] The start-up or movement and start-up control process of multiple purification equipment in each carriage is as follows:

[0140] (1) When the corrected characteristic point wind speed is greater than or equal to the characteristic point wind speed experience value, at time 0, the first purification device at a set distance from the end is started; during the time period from 0 to Δt, the second purification device moves in the direction opposite to the running direction, and the moving distance of the second purification device is The second purification device stops moving and starts at time Δt, which is the same as the wind flow distance. The time corresponding to the corrected characteristic point wind speed ≥ the characteristic point wind speed empirical value is time 0, and Δt is the interval between the startups of adjacent purification devices.

[0141] During the time period of Δt to 2Δt, the third purification device moves in the direction opposite to the running direction, and the moving distance of the third purification device is The third purification device stops moving and starts at 2Δt, which is the same as the wind flow distance;

[0142] Similarly, during the time period of (N-2)Δt to (N-1)Δt, the Nth purification device moves in the direction opposite to the running direction, and the moving distance of the Nth purification device is The same as the flow distance of the wind, at time (N-1)Δt, the Nth purification device stops moving and starts.

[0143] In this embodiment, the curve of real-time wind speed data changing over time is defined as like Figure 11 The curve shown in the figure is a wind speed data collected every 1s, and the change curve is analyzed in each Δt time period. Make points This determines the movement speed or distance of the purification equipment, ensuring it remains consistent with the wind speed or distance of the through-draft. Here, i = 1, 2, …, (N-1). The activation interval Δt is determined by the duration of the through-draft flow within the vehicle and the number of purification devices.

[0144] (2) When the corrected characteristic point wind speed is less than the characteristic point wind speed experience value, and the measured value of the carbon dioxide concentration is greater than or equal to the set value of the carbon dioxide concentration, only the plurality of purification devices are controlled to start, and the purification devices do not move.

[0145] In this embodiment, the set value of carbon dioxide concentration is 2000 ppm.

[0146] (3) When the corrected characteristic point wind speed is less than the characteristic point wind speed empirical value, and the measured temperature value is greater than or equal to the temperature setting value, only the plurality of purification devices are controlled to start, and the purification devices do not move. In this embodiment, the temperature setting value is 28°C.

[0147] When the distance between adjacent purification devices is less than the set distance value Δx1, the two purification devices move at the same speed and in the same direction, preventing collisions between the two adjacent purification devices. For example, when the second purification device moves and the third purification device does not move, and the distance between the second and third purification devices is less than the set distance value Δx1, the first and second purification devices move at the same speed and in the same direction.

[0148] When the distance between the Nth purification device and the vehicle wall is less than the set distance value Δx2, the Nth purification device stops moving, preventing the last purification device from colliding with the vehicle wall. For example, if N = 4, when the distance between the fourth purification device and the vehicle wall is less than the set distance value Δx2, the third purification device stops moving.

[0149] Assume that the distance between the first purification device and the end of the car is Δx3, which is a safe distance to avoid collision with the radar module. For example, when the subway begins to move in a certain direction, the first purification device at the front end of the car moves to a position Δx3 away from the front end. In subsequent control, it does not move and is directly turned on.

[0150] The present invention first finds the position information of the maximum wind speed point of the through-draft in the section (XY plane) where the wind speed sensor is located using a function fitting method based on the through-draft wind speed data collected by the wind speed sensor, and uses the maximum wind speed point of the through-draft as a feature point; at the same time, an empirical formula is derived using the Lagrange interpolation formula, and the wind speed empirical value of the wind speed sensor and the wind speed empirical value of the feature point are calculated according to the empirical formula, and then the corrected feature point wind speed is calculated. The corrected feature point wind speed, the feature point wind speed empirical value and environmental information are used as control conditions for the purification equipment in the carriage, and the real-time wind speed data curve collected by the wind speed sensor is integrated in sequence at a time interval of Δt to control the adaptive movement of the purification equipment, and the purification equipment is turned on in sequence to achieve air purification of the entire carriage under the coexistence of humans and machines, with high efficiency and energy saving.

[0151] The above disclosure is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or modifications within the technical scope disclosed in the present invention, and they should all be covered by the scope of protection of the present invention.

Claims

1. A subway passenger compartment air purification system, characterized in that: include: At least one wind speed sensor is provided at the end section of each carriage, and the wind speed sensor is used to collect wind speed data at the front end of the corresponding carriage; The front end of the carriage refers to the end of the carriage in the same direction of travel; An environmental tester is installed in each carriage, and is used to collect environmental information in the corresponding carriage; A plurality of purification devices are installed on the top of each carriage, and the plurality of purification devices are arranged movably and spaced apart along the length of the carriage; A data processing controller is provided in each carriage, and is used to: Obtain wind speed data at the front end of the corresponding carriage collected by a wind speed sensor, obtain environmental information within the corresponding carriage, obtain position information of the wind speed sensor in a coordinate system, and obtain position information of a feature point on an XY plane of the coordinate system, wherein the coordinate system has a length direction of the corresponding carriage as a Z axis and a cross section of the front end of the carriage as an XY plane; calculate a wind speed empirical value based on the position information of the wind speed sensor, calculate a wind speed empirical value of the feature point based on the position information of the feature point, and correct the wind speed empirical value of the feature point based on the wind speed data and the wind speed empirical value to obtain a corrected wind speed of the feature point; Performing startup control or movement and startup control on multiple purification devices in the corresponding compartment according to the characteristic point wind speed experience value, the corrected characteristic point wind speed, and the environmental information; The characteristic point reflects the maximum wind speed on the XY plane.

2. The subway passenger compartment air purification system according to claim 1, characterized in that: The wind speed sensor is arranged on one side of the end section of the carriage, 1.1m away from the carriage floor.

3. The subway passenger compartment air purification system according to claim 1, characterized in that: A plurality of the purification devices are arranged at equal intervals on the top of the corresponding carriages.

4. The subway passenger compartment air purification system according to claim 1 or 3, characterized in that: The purification equipment is a plasma-activated water purification device, which includes an atomizer, electrodes arranged in the atomizer, atomizing nozzles arranged on both sides of the atomizer, an electric pulley arranged on the atomizer, and a control module connected to the electrodes, the electric pulley and the electric control valve arranged on the atomizing nozzle; the atomizer is filled with dielectric; and the plasma-activated water purification device is movably arranged on the slide rail on the top of the carriage via the electric pulley.

5. The subway passenger compartment air purification system according to claim 4, characterized in that: Radar modules connected to the control module are also provided at both ends of the atomizer and the slide rail.

6. A method for purifying air in a subway passenger compartment, characterized in that: The following steps are involved: Obtain wind speed data collected by a wind speed sensor at the front end of each carriage, where the front end of the carriage refers to the end of the carriage in the same direction of travel; and obtain environmental information within each carriage; Obtaining position information of the wind speed sensor in a coordinate system, and calculating an empirical wind speed value based on the position information of the wind speed sensor; the coordinate system has the Z axis corresponding to the length direction of the carriage and the front section of the carriage as the XY plane; Obtaining the position information of the feature point on the XY plane, and calculating the wind speed empirical value of the feature point based on the position information of the feature point; the feature point reflects the maximum wind speed value on the XY plane; Correct the wind speed experience value of the feature point according to the wind speed data and the wind speed experience value to obtain the corrected wind speed of the feature point; Based on the characteristic point wind speed experience value, the corrected characteristic point wind speed and the environmental information, multiple purification devices in the corresponding compartment are started and controlled or moved and started, wherein the multiple purification devices are spaced along the length direction of the compartment and movably arranged on the top of the compartment.

7. The method for purifying subway passenger compartment air according to claim 6, characterized in that: When the coordinate system takes the carriage floor corresponding to the front section of the carriage as the X-axis and the longitudinal perpendicular bisector of the front section of the carriage as the Y-axis, the calculation formula of the wind speed empirical value of the wind speed sensor is: in, Indicates the wind speed empirical value corresponding to the coordinates of the wind speed sensor in the coordinate system (x, y); It represents the average value of the maximum wind speed at any point on the horizontal line at y = 1.1m in the coordinate system; It represents the average value of the maximum wind speed at any point on the vertical perpendicular bisector at x=0 in the coordinate system; C1, C2, C3, and C4 are all coefficients, which are determined by nonlinear curve fitting from the known points in the coordinate system; C5 and C6 are both coefficients, which are calculated by the Lagrange interpolation formula from the known points in the coordinate system; C0 is the normalization processing coefficient.

8. The method for purifying subway passenger compartment air according to claim 6, characterized in that: When the coordinate system takes the carriage floor corresponding to the front section of the carriage as the X-axis, the longitudinal perpendicular bisector of the front section of the carriage as the Y-axis, and the X-coordinate value of the feature point in the coordinate system is 0, the calculation formula of the wind speed empirical value of the feature point is: in, It represents the empirical wind speed value of the feature point when the X coordinate value of the feature point in the coordinate system is 0, and y is the Y coordinate value of the feature point in the coordinate system; C1, C2, C3, and C4 are all coefficients, which are obtained by nonlinear curve fitting based on the known points in the coordinate system; The Y coordinate value of the feature point in the coordinate system is 1.

5.

9. The subway passenger compartment air purification method according to claim 6, characterized in that: When the coordinate system takes the carriage floor corresponding to the front section of the carriage as the X-axis and the longitudinal perpendicular bisector of the front section of the carriage as the Y-axis, the corrected characteristic point wind speed is: in, is the corrected wind speed of the feature point when the X coordinate value of the feature point in the coordinate system is 0, The wind speed experience value of the feature point before correction when the X coordinate value of the feature point in the coordinate system is 0. The wind speed data at the front of the carriage at time t0 collected by the wind speed sensor, t0 is the sampling time of the wind speed sensor, is the empirical wind speed value corresponding to the coordinate of the wind speed sensor in the coordinate system is (x, y).

10. The subway passenger compartment air purification method according to claim 6, characterized in that: The start-up or movement and start-up control process of multiple purification equipment in each carriage is as follows: When the corrected characteristic point wind speed is greater than or equal to the characteristic point wind speed experience value, multiple purification devices are controlled to move sequentially in the direction opposite to the running direction, and the devices are started when the movement stops; sequentially means that the purification devices are moved in the order opposite to the running direction; When the corrected characteristic point wind speed is less than the characteristic point wind speed experience value, and the measured value of the carbon dioxide concentration is greater than or equal to the set value of the carbon dioxide concentration, only multiple purification devices are controlled to start; When the corrected characteristic point wind speed is less than the characteristic point wind speed experience value, and the measured temperature value is greater than or equal to the temperature setting value, only multiple purification devices are controlled to start.

11. The method for purifying subway passenger compartment air according to claim 10, characterized in that: The specific implementation process of controlling multiple purification devices to move in the direction opposite to the running direction in sequence and starting the device when the movement stops is as follows: Assume that in the opposite direction of operation, multiple purification devices are numbered as the first purification device, the second purification device, ..., the Nth purification device, where N is the number of purification devices in each carriage; the first purification device refers to the purification device located at the front end of the carriage, and the curve of the change of real-time wind speed data over time is defined as When the corrected characteristic point wind speed is greater than or equal to the characteristic point wind speed experience value, at time 0, the first purification device at a set distance from the end is started; during the time period of 0 to Δt, the second purification device moves in the opposite direction to the running direction, and the moving distance of the second purification device is At time Δt, the second purification device stops moving and starts; the time corresponding to the corrected characteristic point wind speed ≥ the characteristic point wind speed empirical value is time 0, and Δt is the interval between the starts of adjacent purification devices; During the time period of Δt to 2Δt, the third purification device moves in the opposite direction to the running direction, and the moving distance of the third purification device is At time 2Δt, the third purification device stops moving and starts; Similarly, during the time period of (N-2)Δt to (N-1)Δt, the Nth purification device moves in the direction opposite to the running direction, and the moving distance of the Nth purification device is At time (N-1)Δt, the Nth purification device stops moving and starts.

12. The subway passenger compartment air purification method according to claim 11, characterized in that: When the distance between adjacent purification devices is less than the set distance value, the adjacent purification devices move in the same direction at the same speed.

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