Method and system for improving wind speed uniformity of biosafety cabinet

Abstract

The invention relates to the technical field of biosafety cabinets, in particular to a method and system for improving the wind speed uniformity of a biosafety cabinet, and the system comprises a gas flow monitoring module which comprises a flow sensor arranged in a gas inlet channel and is used for monitoring the instantaneous flow value of external gas entering a front grid in real time, and the flow sensor is used for monitoring the flow value of the external gas; and the backflow area dynamic adjusting mechanism is arranged in the gas inlet channel and can adjust the backflow area, allowing gas to pass through, of the rear grille according to the instantaneous flow value change entering the front grille. The air inflow of the front grille is monitored in real time, and the backflow area of the rear grille is dynamically adjusted according to the change of the air inflow, so that abnormal fluctuation of negative pressure of the rear grille caused by sudden drop of the air inflow of the front grille is effectively avoided, and distortion caused by breaking of a vertical laminar flow path is prevented. Therefore, the biological safety cabinet can maintain a stable airflow barrier all the time under various dynamic operation scenes of experimenters, and pollutants such as biological aerosol can be physically blocked continuously and efficiently.

Description

Technical Field

[0001] The present invention relates to the technical field of biosafety cabinets, and in particular to a method and system for improving wind speed uniformity of a biosafety cabinet. Background Art

[0002] The biosafety cabinet utilizes a specific structural coupling between the front grille and the front window access port to create an airflow barrier based on a negative pressure gradient, thereby forming a physical barrier to contaminants such as bioaerosols. Its core mechanism relies on the synergy between the natural air intake from the front grille, typically located at the bottom of the front window access port, and the negative pressure return air from the rear grille. External air enters through the front grille and is driven by a fan to the HEPA filter for purification. It is then split into approximately 30% external exhaust flow and approximately 70% internal recirculating laminar flow. The recirculating laminar flow flows vertically downward through the operating area, ultimately returning to the HEPA filter through the rear grille, forming a closed airflow loop.

[0003] The front window operation port is the main interaction area for experimenters. During the operation, the experimenters may block part of the air intake holes of the front grille with their limbs or equipment, resulting in a sudden drop in the air intake of the front grille, which in turn causes abnormal fluctuations in the negative pressure of the rear grille, breaking the preset path stability of the vertical laminar flow, causing laminar flow distortion, and thus affecting the protective effect of the biological safety cabinet.

[0004] Therefore, there is an urgent need to develop a new control system with dynamic perception, precise compensation and multi-parameter coordination to solve the problem of airflow stability in biological safety cabinets under dynamic operation scenarios. Summary of the Invention

[0005] The object of the present invention is to provide a method and system for improving the wind speed uniformity of a biosafety cabinet, so as to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A system for improving the wind speed uniformity of a biological safety cabinet includes a safety cabinet body, wherein the safety cabinet body is provided with an electrical chamber and an operating chamber, an L-shaped plate is provided in the operating chamber, an air intake channel is formed between the L-shaped plate and the inner wall of the operating chamber, a front grille is provided on the horizontal surface of the L-shaped plate, and a rear grille is provided on the vertical surface of the L-shaped plate.

[0008] It also includes a gas flow monitoring module, which includes a flow sensor arranged in the air intake channel, and is used to monitor the instantaneous flow value of external gas entering the front grille in real time.

[0009] The reflow area dynamic adjustment mechanism is arranged in the air intake channel, and can adjust the reflow area of the rear grille that allows gas to pass through according to the change of the instantaneous flow value entering the front grille.

[0010] Principle of normal airflow circulation: When the biosafety cabinet is operating, external air enters the air intake duct through the front grille located at the bottom of the front window operating port under the action of natural pressure. The incoming air is driven by the fan and transported to the HEPA filter for purification. The purified air is then split, with approximately 30% discharged as external exhaust flow and approximately 70% forming an internal circulation laminar flow. The internal circulation laminar flow flows vertically downward through the operating area of the operating chamber, providing a clean airflow environment for the operating area, and then returns to the HEPA filter through the rear grille, thus forming a closed airflow loop. Based on the negative pressure gradient, an airflow barrier is constructed to physically block pollutants such as bioaerosols.

[0011] The flow sensor in the gas flow monitoring module monitors in real time the instantaneous flow value of the internal and external gases entering the front grille through the air intake channel. When the experimenter's limbs or equipment block part of the air intake holes of the front grille during operation, causing the air intake of the front grille to drop sharply, the flow sensor captures the change in the instantaneous flow value and transmits the information to the dynamic adjustment mechanism of the reflow area. The dynamic adjustment mechanism of the reflow area adjusts the reflow area of the rear grille that allows gas to pass according to the change in the received instantaneous flow value. For example, when it is detected that the air intake of the front grille has decreased, the dynamic adjustment mechanism increases the reflow area of the rear grille to balance the abnormal fluctuation of the negative pressure of the rear grille caused by the reduction in the air intake of the front grille, maintain the stability of the preset path of the vertical laminar flow, and ensure the normal circulation of the airflow in the biosafety cabinet.

[0012] By monitoring the air intake of the front grille in real time and dynamically adjusting the recirculation area of the rear grille based on changes, we effectively avoid abnormal fluctuations in the rear grille's negative pressure caused by sudden drops in the air intake, preventing the vertical laminar flow path from being disrupted and distorted. This ensures that the biosafety cabinet can maintain a stable airflow barrier under various dynamic operating scenarios, continuously and efficiently physically blocking pollutants such as bioaerosols, and greatly improving the stability of the biosafety cabinet's protective effects.

[0013] Preferably, the dynamic adjustment mechanism of the reflow area includes an adjustment plate arranged in the air intake channel, the side wall of the adjustment plate is in contact with the side wall of the L-shaped plate, and an electric push rod is fixed in the air intake channel, which can push the adjustment plate up and down, thereby changing the blocking area of the rear grille by the adjustment plate.

[0014] Within the biosafety cabinet's air intake duct, the side walls of the adjustment plate fit tightly against the side walls of the L-shaped plate, forming an adjustable airflow channel structure. An electric actuator is fixed within the air intake duct, one end of which is connected to the adjustment plate. When the gas flow monitoring module detects a change in the instantaneous flow rate of the front grille, it triggers a corresponding control signal. Upon receiving the control signal, the electric actuator operates according to the signal's instructions. When a decrease in air intake is detected on the front grille, the electric actuator pushes the adjustment plate upward to balance the abnormal fluctuation in negative pressure on the rear grille. This reduces the area blocked by the adjustment plate from the rear grille, increases the recirculation area through the rear grille, maintains relatively stable negative pressure at the rear grille, and maintains airflow balance. Conversely, when air intake on the front grille increases, the electric actuator pulls the adjustment plate downward, increasing the area blocked from the rear grille and reducing the recirculation area. This avoids airflow turbulence caused by excessive air intake. This dynamically adjusts the gas recirculation area of the rear grille to ensure stable airflow circulation within the biosafety cabinet.

[0015] Preferably, the rear grille includes a plurality of guide components, the guide components include horizontally arranged guide plates, and the guide plates are provided with rotating rods. The guide plates can rotate along the axis of the corresponding rotating rods under the drive of the rotating rods, thereby changing the air intake angle of the rear grille.

[0016] When the airflow pattern within the biosafety cabinet changes due to factors such as changes in the air intake through the front grille, the deflector plate can be rotated along the axis of the rotating rod to optimize the airflow. For example, if the air intake through the front grille decreases, causing abnormal airflow velocity and direction, the deflector plate can be rotated a certain angle by the rotating rod, changing the air intake angle of the rear grille. This adjusts the direction and velocity distribution of the airflow entering the rear grille to better align with the ideal airflow circulation pattern within the biosafety cabinet, thereby improving problems such as vertical laminar flow distortion caused by airflow changes and maintaining optimal airflow within the biosafety cabinet.

[0017] Preferably, the side walls of the L-shaped plate are provided with adjustment slots on both sides of the rear grille, and both ends of the rotating rod extend into the adjustment slots. A driven gear is provided at the end of the rotating rod extending into the adjustment slot, and a rack meshing with the driven gear is provided on the adjustment plate. When the adjustment plate moves up and down, the rack can drive the driven gear to rotate.

[0018] This design integrates reflow area and intake angle adjustment into a single mechanical structure. When the adjustment plate adjusts the rear grille's reflow area based on the front grille's intake volume, it simultaneously drives the rear grille's deflector plate to change the intake angle, achieving coordinated operation of these two key airflow adjustment methods. Compared to independently controlling the reflow area and intake angle, this significantly simplifies the control logic. No complex sensors and control systems are required for intake angle adjustment; both the reflow area and intake angle can be adjusted simultaneously simply by the movement of the adjustment plate. This not only reduces system design and manufacturing costs, but also mitigates the risk of failures associated with complex control logic, improving system reliability and stability.

[0019] Preferably, the initial position of the adjustment plate covers 65%±5% of the effective ventilation area of the rear grille, and the angle between the guide plate and the horizontal plane is 0°; when the electric push rod pushes the adjustment plate to move upward, the exposed area of the rear grille increases by 20% compared to the initial area, the driven gear rotates by 10°, and the corresponding downward inclination angle of the guide plate on the operating chamber side is 10°.

[0020] In its initial position, the damper covers 65% ± 5% of the rear grille's effective ventilation area, with the deflector at a 0° angle to the horizontal. This initial position establishes a baseline condition for airflow within the biosafety cabinet, where air flows through the cabinet according to the designed, normal pattern.

[0021] When the electric push rod pushes the adjustment plate upward, the exposed area of the rear grille changes. For every 20% increase in the exposed area of the rear grille compared to the initial area, the driven gear connected to the rotating rod rotates 10°. Because the deflector is mounted on the rotating rod, the downward inclination angle of the deflector on the operating chamber side also changes to 10°. This means that as the adjustment plate moves upward, not only does the ventilation area of the rear grille increase, but the angle of the deflector is also adjusted synchronously. In this way, the air intake volume and intake angle of the rear grille can be adjusted accordingly based on the changes in the air intake volume of the front grille, thereby maintaining stable and uniform airflow within the biosafety cabinet.

[0022] Preferably, the maximum inclination angle of the guide plate 1502 on the side of the operating chamber 1102 is limited to 25°.

[0023] The tilt angle is related to the maximum distance the adjustment plate rises. Setting the maximum tilt angle prevents the airflow from becoming uncontrollable due to an excessive tilt angle, ensuring the rationality and safety of the adjustment process and enabling the biosafety cabinet to operate stably under various working conditions.

[0024] Preferably, a drainage box located inside the air intake channel is provided on the side wall of the L-shaped plate, the drainage box covers the entire rear grille, the upper end of the drainage box is open, and the gas entering the rear grille can enter the air intake channel from the upper end opening of the drainage box.

[0025] During operation of a biosafety cabinet, air entering through the front grille is driven by the fan and continues upward upon reaching the rear grille of the air inlet duct. However, air entering from the operating area through the rear grille follows a different, vertical, upward direction than the air entering through the front grille. This directional difference can easily cause the two airflows to interfere with each other, creating turbulence that disrupts the stability and uniformity of the airflow within the biosafety cabinet, thereby affecting the barrier to contaminants such as bioaerosols.

[0026] To address this issue, a drainage box is installed on the side wall of the L-shaped panel, within the air intake duct. The drainage box covers the entire rear grille and is open at the top. Air passing through the rear grille from the operating area is collected and guided by the drainage box, following a specific path and entering the air intake duct through the top opening of the drainage box. This separates the air entering from the rear grille from the air entering from the front grille and flowing vertically upward, preventing the two from directly intersecting and causing turbulence. This ensures that airflow within the biosafety cabinet flows in an orderly manner, maintaining optimal airflow conditions.

[0027] A method for adjusting the wind speed uniformity of a biosafety cabinet comprises the following steps:

[0028] Step 1: Get the initial air volume Q1m from the front grille through the flow sensor at startup 3 / h

[0029] The initial effective reflow area of the rear grille is S1 = 0.65 × Stotal. Stotal is the total ventilation area of the rear grille.

[0030] Step 2: Dynamic adjustment process:

[0031] Monitor the current air intake volume Q2 in real time and calculate the relative change Q3 = (Q1-Q2) / Q1×100%

[0032] Every 1% increase in the relative change Q3 corresponds to a 1.2% increase in the rear grille recirculation area.

[0033] This method precisely adjusts the rear grille's return flow area based on real-time changes in the front grille's air volume. By accurately calculating the relative change and adjusting the area based on a fixed proportional relationship, precise adjustments are ensured. This precise dynamic adjustment effectively addresses changes in air volume caused by various factors during experiments, such as operator obstruction of the front grille. This ensures consistent airflow within the biosafety cabinet, improving the cabinet's adaptability to complex operating scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram of the internal structure of the biosafety cabinet in Example 1;

[0035] Figure 2Schematic diagram of the structure of the flow plate in Example 1;

[0036] Figure 3 Schematic diagram of the structure of the L-shaped plate and the electric push rod in Example 2;

[0037] Figure 4 This is a schematic structural diagram of the flow guide assembly in Example 2.

[0038] In the figure: 110, safety cabinet body; 1101, electrical chamber; 1102, operating chamber; 1103, L-shaped plate; 1104, air intake channel; 120, front grille; 1301, flow plate; 1302, notch; 1401, adjustment plate; 1402, electric push rod; 1403, rack; 150, rear grille; 1501, guide assembly; 1502, guide plate; 1503, rotating rod; 1504, driven gear; 160, adjustment slot; 170, drainage box. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0040] Example 1

[0041] like Figure 1 and Figure 2 As shown, this embodiment provides a biosafety cabinet, wherein in order to make the picture more intuitive, the glass window, fan and HEPA filter and other existing technical structures of the biosafety cabinet are not shown in the figure, and their settings are consistent with those of the existing technology.

[0042] In this embodiment, the biosafety cabinet is equipped with a system for improving the uniformity of the wind speed in the biosafety cabinet. The interior of the safety cabinet body 110 includes an electrical chamber 1101 and an operating chamber 1102 arranged upper and lower. The electrical chamber 1101 is provided with a fan and a HEPA filter; the L-shaped plate 1103 in the operating chamber 1102 and the inner wall of the operating chamber 1102 form an air intake channel 1104. The front grille 120 is provided on the horizontal surface of the L-shaped plate 1103, and the rear grille 150 is provided on the vertical surface.

[0043] Under the action of the fan, the outside air enters the air intake channel 1104 through the front grille 120, and then enters the electrical cavity 1101 from the air intake channel 1104. After entering the electrical cavity 1101, the outside air is filtered and processed by the HEPA filter. Part of the processed air is directly discharged out of the biological cabinet, and the other part of the processed air enters the operating cavity 1102 vertically downward. The vertically downward air forms a laminar flow. When it reaches the bottom of the operating cavity 1102, the laminar flow passes through the rear grille 150 and re-enters the air intake channel 1104, thereby forming a complete airflow cycle.

[0044] A gas flow monitoring module is provided in the air intake channel 1104, which includes a flow sensor for real-time monitoring of the instantaneous flow value of external gas entering the front grille 120. The flow monitoring module includes a flow plate 1301 located below the horizontal plane of the L-shaped plate 1103. The flow plate 1301 divides the air intake channel 1104 located on the horizontal plane of the L-shaped plate 1103 into two relatively independent areas. A notch 1302 is provided on the flow plate 1301 for gas to flow through. In this embodiment, the flow sensor adopts an ultrasonic flow sensor, which is installed in the notch 1302. It is used to monitor the gas flow in the notch 1302. In order to make the data monitored by the ultrasonic flow sensor more accurate, the thickness of the flow plate 1301 should be increased as much as possible, and its minimum thickness should not be less than 5 times the diameter of the notch 1302, so as to form a stable flow field, ensure that the airflow is fully developed in the notch 1302 pipe section, and reduce the impact of turbulence and uneven velocity distribution on the propagation of ultrasonic signals.

[0045] This embodiment is also provided with a dynamic adjustment mechanism for the reflow area, which consists of an adjustment plate 1401 that is attached to the side wall of the L-shaped plate 1103 and an electric push rod 1402 fixed in the air intake channel 1104. The electric push rod 1402 can push the adjustment plate 1401 up and down to change the blocking area of the rear grille 150; the flow sensor of the gas flow monitoring module monitors the total gas flow entering the front grille 120 in real time, and converts the data into an electrical signal, and sends it to the control system of the electric push rod 1402, thereby controlling the adjustment plate 1401 to change with the incoming gas flow rate for the purpose of real-time movement.

[0046] Furthermore, a drainage box 170, covering the entire rear grille 150 and open at its upper end, is located within the L-shaped sidewall air inlet passage 1104. Air passing through the rear grille 150 from the operating area is collected and directed by drainage box 170, following a specific path and entering air inlet passage 1104 through the upper opening of drainage box 170. This separates air entering through the rear grille 150 from air flowing vertically upward through the front grille 120, preventing the air from directly intersecting and causing turbulence. This ensures orderly airflow within the biosafety cabinet and maintains a good airflow state.

[0047] The specific working principle of the above system is as follows: When the biological safety cabinet is working, external air enters the air inlet channel 1104 through the front grille 120, and is sent to the HEPA filter for purification by the fan. About 30% of the air is discharged as external exhaust flow, and the remaining 70% forms an internal circulation laminar flow that flows vertically downward through the operating area, and then enters the drainage box 170 through the rear grille 150, and then enters the air inlet channel 1104, and returns to the electrical installation cavity through the fan. The previous process is repeated to form a closed loop, and an airflow barrier is constructed based on the negative pressure gradient to block pollutants.

[0048] The gas flow monitoring module monitors the instantaneous flow rate of air entering the front grille 120 in real time. If the air intake to the front grille 120 drops suddenly due to experimental operations, the flow sensor transmits a signal to the dynamic recirculation area adjustment mechanism. Electric actuator 1402 moves adjustment plate 1401 in response to the signal, changing the recirculation area of the rear grille 150. If the air intake to the front grille 120 decreases, adjustment plate 1401 moves upward to increase the recirculation area, and guide plate 1502 tilts downward to adjust the airflow direction and velocity distribution, maintaining stable vertical laminar flow. The induction box 170 separates the air entering the rear grille 150 from the air exiting vertically from the front grille 120, preventing turbulence and ensuring orderly airflow.

[0049] The regulating plate 1401 changes the recirculation area of the rear grille 150 and the gas flow rate of the front grille 120 to satisfy the following relationship:

[0050] After the biosafety cabinet is opened, the initial air intake volume Q1m is at the front grille 120 without any obstruction. 3 / h, the initial effective recirculation area of the rear grille 150 is S1=0.65×S 总 S 总 The total ventilation area of the rear grille is 150.

[0051] During operation, the current air intake volume Q2 is monitored in real time, and the relative change Q3 = (Q1-Q2) / Q1×100% is calculated. For every 1% increase in Q3, the recirculation area of the rear grille 150 is increased by 1.2%, thereby dynamically adjusting to maintain airflow stability.

[0052] Example 2

[0053] like Figure 3 and Figure 4As shown, compared to Example 1, this embodiment further refines the structure of the rear grille 150. The rear grille 150 in this embodiment is composed of multiple air guide assemblies 1501, each of which includes a horizontal air guide plate 1502 and a rotating rod 1503. The air guide plate 1502 can rotate about the axis of the rotating rod 1503 to change the air intake angle. Adjustment slots 160 are defined on both sides of the L-shaped sidewalls of the rear grille 150. The rotating rod 1503 extends into each end of the rotating rod and is equipped with a driven gear 1504 at its end. The adjustment plate 1401 has a rack 1403 meshing with the rack. When the adjustment plate 1401 moves up and down, the rack 1403 drives the driven gear 1504 to rotate the air guide plate 1502, changing the air intake angle.

[0054] In this embodiment, the adjustment plate 1401 initially covers 65% ± 5% of the effective ventilation area of the rear grille 150. At this point, the angle between the deflector plate 1502 and the horizontal plane is 0°. When the electric actuator 1402 pushes the adjustment plate 1401 upward, the driven gear 1504 rotates 10° for every 20% increase in the exposed area of the rear grille 150 compared to the initial area. Correspondingly, the deflector plate 1502 tilts downwards by 10° on the operating chamber 1102 side. The maximum tilt angle of the deflector plate 1502 on the operating chamber 1102 side is limited to 25°. Compared to independently controlling the recirculation area and intake angle, this significantly simplifies the control logic. Complex sensors and control systems are no longer required for intake angle adjustment; both the recirculation area and intake angle can be adjusted simultaneously solely through the movement of the adjustment plate 1401. This not only reduces system design and manufacturing costs but also mitigates the risk of failures associated with complex control logic, improving system reliability and stability.

Claims

1. A system for improving the wind speed uniformity of a biological safety cabinet, comprising a safety cabinet body (110), wherein the safety cabinet body (110) is provided with an electrical chamber (1101) and an operating chamber (1102), wherein an L-shaped plate (1103) is provided in the operating chamber (1102), an air intake channel (1104) is formed between the L-shaped plate (1103) and the inner wall of the operating chamber (1102), a front grille (120) is provided on the horizontal surface of the L-shaped plate (1103), and a rear grille (150) is provided on the vertical surface of the L-shaped plate (1103), characterized in that: The gas flow monitoring module includes a flow sensor arranged in the air inlet channel (1104), which is used to monitor the instantaneous flow value of external gas entering the front grille (120) in real time. The reflow area dynamic adjustment mechanism is arranged in the air inlet channel (1104), and can adjust the reflow area of the rear grille (150) that allows gas to pass through according to the change of the instantaneous flow value entering the front grille (120).

2. The system for improving air velocity uniformity in a biological safety cabinet according to claim 1, characterized in that: The reflow area dynamic adjustment mechanism comprises an adjustment plate (1401) arranged in the air intake channel (1104), the side wall of the adjustment plate (1401) is in contact with the side wall of the L-shaped plate (1103), and an electric push rod (1402) is fixed in the air intake channel (1104). The electric push rod (1402) can push the adjustment plate (1401) to move up and down, thereby changing the shielding area of the adjustment plate (1401) on the rear grille (150).

3. The system for improving air velocity uniformity in a biological safety cabinet according to claim 2, characterized in that: The rear grille (150) includes a plurality of air guide components (1501), each air guide component (1501) including a horizontally arranged air guide plate (1502), a rotating rod (1503) being provided on the air guide plate (1502), and the air guide plate (1502) can be driven by the rotating rod (1503) to rotate along the axis of the corresponding rotating rod (1503), thereby changing the air intake angle of the rear grille (150).

4. The system for improving air velocity uniformity in a biosafety cabinet according to claim 3, characterized in that: The side walls of the L-shaped plate (1103) are provided with adjustment slots (160) located on both sides of the rear grille (150), and both ends of the rotating rod (1503) extend into the adjustment slots (160). The ends of the rotating rod (1503) extending into the adjustment slots (160) are provided with driven gears (1504). The adjustment plate (1401) is provided with a rack (1403) meshing with the driven gear (1504). When the adjustment plate (1401) moves up and down, the rack (1403) can drive the driven gear (1504) to rotate.

5. A biosafety cabinet wind speed adjustment system according to claim 4, characterized in that: The adjustment plate (1401) initially covers 65%±5% of the effective ventilation area of the rear grille (150), and at this time, the angle between the guide plate (1502) and the horizontal plane is 0°; when the electric push rod (1402) pushes the adjustment plate (1401) to move upward, for every 20% increase in the exposed area of the rear grille (150) compared to the initial area, the driven gear (1504) rotates by 10°, and the corresponding downward tilt angle of the guide plate (1502) on the operating chamber (1102) side is 10°.

6. The system for improving air velocity uniformity in a biological safety cabinet according to claim 5, characterized in that: The maximum inclination angle of the guide plate (1502) on the operating chamber (1102) side is limited to 25°.

7. The system for improving air velocity uniformity in a biological safety cabinet according to claim 2, characterized in that: A drainage box (170) located inside the air intake channel (1104) is provided on the side wall of the L-shaped plate (1103). The drainage box (170) covers the entire rear grille (150). The upper end of the drainage box (170) is open, and the gas entering the rear grille (150) can enter the air intake channel (1104) through the upper end opening of the drainage box (170).

8. A method for adjusting wind speed uniformity of a biosafety cabinet based on the system according to any one of claims 1 to 7, characterized in that: The following steps are included Step 1: When starting, obtain the initial air flow Q1 (m 3 / h) The initial effective recirculation area of the rear grille (150) S1=0.65×S 总 (S 总 is the total ventilation area of the rear grille (150) Step 2: Dynamic adjustment process: Monitor the current air intake volume Q2 in real time and calculate the relative change Q3 = (Q1-Q2) / Q1×100% Every 1% increase in the relative change amount Q3 corresponds to a 1.2% increase in the backflow area of the rear grille (150).

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