Passive ventilation system of roadbed and construction method of passive ventilation system

Abstract

The invention relates to the technical field of roadbed engineering, and provides a passive ventilation system of a roadbed and a construction method thereof.The system comprises a first pipeline used for being communicated with one end of a ventilation channel in the roadbed, and the first pipeline is provided with an exhaust outlet; the blades are connected to the rotating shaft; and the centrifugal impeller is arranged in the first pipeline and corresponds to the air outlet, and the blades rotate so that the rotating shaft can drive the centrifugal impeller to rotate. According to the system, rich wind energy resources in the plateau area can be effectively utilized, the functions of in-service and newly-built ventilation roadbed structures are systematically improved, extra power is not needed, and interference and damage to the environment can be reduced; refreezing time of a newly-built ventilation roadbed can be shortened, working efficiency of an in-service ventilation roadbed can be improved, ventilation and temperature control efficiency of the ventilation roadbed can be enhanced, the design vehicle speed of a road can be improved, the convection effect is good, ventilation pipeline blockage can be avoided, the ventilation and cooling effect is further guaranteed, and good popularization prospects are achieved.

Description

Technical Field

[0002] The invention relates to the technical field of roadbed engineering, in particular to a passive ventilation system of a roadbed and a construction method thereof. Background Art

[0003] Frozen soil refers to various rocks and soils below zero degrees Celsius that contain ice. Frozen soil has rheological properties and is extremely sensitive to temperature. Its long-term strength is much lower than its instantaneous strength characteristics. Frozen soil freezes like ice in cold seasons, and its volume expands as the temperature drops. Engineering structures built in frozen soil areas will be lifted and squeezed by the "fat" frozen soil; in summer, the volume of the melted frozen soil shrinks, and the engineering structures will become loose and tilted.

[0004] When designing highways in permafrost areas, it is necessary to formulate a reasonable roadbed design plan based on geological conditions such as ice content and frozen soil grade classification. Ventilated roadbeds are mainly used in permafrost areas with high ice content. Ventilation pipes and ventilation plates of certain sizes are set at certain intervals in the roadbed to reduce the temperature in the roadbed. The purpose is to use the air flowing through the ventilation pipes (usually concrete pipes) placed inside the roadbed to exchange heat with the pipe wall through strong forced convection, thereby taking away the heat in the roadbed soil. After the ventilated roadbed is built, it can reach a new thermal equilibrium state with the underlying frozen soil, and the roadbed temperature field is relatively smooth.

[0005] At present, the ventilation roadbed in permafrost areas has the following problems: the pressure difference on both sides of the inlet and outlet of the ventilation roadbed air duct is small, it is not easy to generate convection in the pipe under natural conditions, it is greatly restricted by natural conditions, and the abundant wind resources are not fully utilized. Summary of the invention

[0006] The purpose of the present invention is to solve the problems in the prior art that the pressure difference on both sides of the inlet and outlet of the ventilation roadbed air duct is small, convection in the pipe is not easy to occur under natural conditions, it is greatly restricted by natural conditions, and the abundant wind resources are not fully utilized. A passive ventilation system for the roadbed and a construction method thereof are provided.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: In a first aspect, the present invention provides a passive ventilation system for a roadbed, comprising: A first pipe, used to communicate with one end of the ventilation channel in the roadbed, wherein the first pipe is provided with an exhaust port; A blade connected to the rotating shaft; A centrifugal impeller is arranged in the first pipe corresponding to the air outlet, and the rotation of the blades can enable the rotating shaft to drive the centrifugal impeller to rotate.

[0008] The structural form, quantity, size and other parameters of the blades can be designed according to local wind direction, wind speed and other wind parameters. Compared with existing vents, they can make better use of wind resources.

[0009] Using the passive ventilation system of the roadbed described in the present invention, the blades can rotate under the action of wind, thereby driving the centrifugal impeller located in the first pipe to rotate, and the first pipe is connected to the ventilation channel, so that the air in the ventilation channel can be pumped to the exhaust port for discharge. As the ventilation proceeds, the ventilation channel can be effectively cooled. This system uses blades to drive ventilation under the action of wind, which can effectively utilize the rich wind energy resources in the plateau area, systematically improve the structural functions of existing and newly built ventilation roadbeds, and does not require additional power, with a higher cost-effectiveness ratio, reducing interference and damage to the environment, and helping to meet environmental protection requirements; for newly built ventilation roadbeds, the refrost time can be shortened, and for existing ventilation roadbeds, especially those with ventilation channel deformation caused by thawing and uneven settlement, the work efficiency can be significantly improved, and the ventilation roadbed ventilation and temperature control efficiency can be enhanced, which has a good promotion prospect.

[0010] Preferably, the blades are located above the air outlet, and the air outlet is arranged at a height higher than the road surface.

[0011] That is, the installation positions of the exhaust port and the blades are higher than the road surface, which can prevent the exhausted air from affecting the roadbed height layer. The blades can also obtain the wind force generated by driving, make up for the lack of natural wind force, and effectively improve the ventilation effect. In the prior art, the lower end ports of the ventilation ducts in the transverse slope or curved roadbed are buried under the ground or blocked by the surface environment. The corresponding road sections cannot be effectively ventilated and cooled, and melting and sinking are very likely to occur. The present application can effectively improve the problem that the ventilation channels are blocked due to road conditions and cannot be ventilated.

[0012] Preferably, the rotating shaft is arranged along the height direction of the road, the blades are connected to the rotating shaft via a connecting rod, and the connecting rod is arranged along the radial direction of the rotating shaft.

[0013] With the above arrangement, the rotating shaft of the device after installation is arranged vertically, which is more suitable for receiving the wind force of the vehicle.

[0014] Further preferably, the blade is S-shaped.

[0015] Further preferably, the blade is a lift blade.

[0016] Further preferably, the blades are rectangular plates, the plate surfaces of the blades are arranged parallel to the rotating shaft, there are 3 to 8 blades, and the blades are evenly distributed along the circumference of the rotating shaft.

[0017] Further preferably, the plate surface of the blades is replaced to be arranged along the radial direction of the rotating shaft.

[0018] Preferably, the rotating shaft is connected to the centrifugal impeller via a speed increasing gear box.

[0019] Further preferably, a bell mouth is provided at the other end of the ventilation channel, and the larger end of the bell mouth is used for air intake.

[0020] That is, the small opening faces the inside of the air inlet of the ventilation channel. When the natural wind flows from the large opening to the small opening, the pressure remains unchanged. However, due to the narrowing of the channel, a narrow tube effect is produced, which increases the wind speed of the natural wind entering the ventilation channel through the small opening, thereby improving the convective heat exchange efficiency with the wall of the ventilation channel and further improving the cooling efficiency.

[0021] Further preferably, it also includes a second pipe, the first pipe is connected to the ventilation channel through the second pipe, and 2-3 second pipes are connected to the same first pipe.

[0022] It is helpful to reduce the layout of blades and reduce maintenance costs.

[0023] Further preferably, the air outlet faces adjacent blades of the passive ventilation system.

[0024] Avoid ventilation dead spots in individual ventilation channels.

[0025] In a second aspect, the present invention provides a construction method of a passive ventilation system for a roadbed, which is applied to any of the passive ventilation systems for a roadbed as described above, and comprises the following steps: S1. Determine the connection position of the first pipeline according to the wind direction, and determine the arrangement position of the exhaust port according to the roadbed height, wind direction and the position of the ventilation channel; S2, assembling the first pipe, blades and centrifugal impeller; S3. Connect the passive ventilation system to the corresponding end of the ventilation channel.

[0026] The construction method of the passive ventilation system of the roadbed described in the present invention can be effectively applied to existing and newly built ventilated roadbed structures in permafrost areas due to its passive design and the installation on the exposed part of the roadbed, thereby increasing the ventilation volume of the ventilated roadbed, reducing the influence of the highway in the permafrost area on the heat balance of the underlying frozen soil, and increasing the service life of the ventilated roadbed; the basic system of the existing ventilation road is easy to install, with a short construction period, does not affect normal traffic, and does not require construction processes such as excavation and backfilling.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The passive ventilation system of the roadbed described in the present invention uses blades to drive exhaust under the action of wind, which can effectively utilize the abundant wind energy resources in the plateau area, and systematically improve the structural functions of existing and newly built ventilated roadbeds without the need for additional power, with a higher cost-effectiveness ratio, reducing interference and damage to the environment, and helping to meet environmental protection requirements. For newly built ventilated roadbeds, the refrost time can be shortened, and for existing ventilated roadbeds, the work efficiency can be improved, the ventilation and temperature control efficiency of the ventilated roadbed can be enhanced, which is conducive to increasing the design speed of the road, and the good convection effect can also avoid blockage of the ventilation ducts, further ensuring the ventilation and cooling effect, and has a good promotion prospect.

[0028] 2. The construction method of the passive ventilation system of the roadbed described in the present invention can be effectively applied to existing and newly built ventilated roadbed structures in permafrost areas, increase the ventilation volume of the ventilated roadbed, reduce the impact of the highway in permafrost areas on the heat balance of the underlying frozen soil, and increase the service life of the ventilated roadbed; the basic system of the existing ventilation road is easy to install, with a short construction period, does not affect normal traffic, and does not require construction processes such as excavation and backfilling. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of a passive ventilation system for a roadbed in Example 1; Figure 2 is a schematic diagram of the connection structure of the blade and the centrifugal impeller of Example 1; Figure 3 yes Figure 2 A partial schematic diagram of the Figure 4 This is a schematic diagram of the installation of a passive ventilation system for a roadbed in Example 1. Figure 1 ; Figure 5 yes Figure 4 Schematic elevation diagram of Figure 6 is a schematic diagram of the structure of the bell mouth in Example 1; Figure 7 is another structural schematic diagram of the blade in Example 1; Figure 8 This is a schematic diagram of the installation of a passive ventilation system for a roadbed in Example 1. Figure 2 ; Fig. 9 yes Figure 8 Schematic elevation diagram of .

[0030] Figure numerals: 0-roadbed; 11-first pipeline; 12-second pipeline; 13-exhaust port; 2-blade; 21-rotating shaft; 22-connecting rod; 3-centrifugal impeller; 4-bell mouth; 5-speed increasing gear box. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0032] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above-mentioned subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0033] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating the orientation or position relationship such as "up", "down", "left", "right", "center", "inside", "outside", etc. are all expressions based on the orientation or position relationship shown in the drawings, or are the orientation or position relationship when the invented product / equipment / device is usually used. These terms of orientation or position relationship are only for the convenience of describing the scheme of the present invention or simplifying the description in the specific embodiments, so as to facilitate the technicians to quickly understand the scheme, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific position relationship, and therefore cannot be understood as a limitation on the present invention.

[0034] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simplified to mean that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the scheme of the present invention.

[0035] In addition, the expressions “first”, “second”, “third”, etc., which appear in the terms, are merely used to distinguish the description of the same or similar components and should not be understood as emphasizing or implying the relative importance of specific components.

[0036] In addition, in the description of the embodiments of the present invention, "several", "plurality" and "a number" represent at least 2. It can be any number such as 2, 3, 4, 5, 6, 7, 8, 9, and even more than 9.

[0037] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, the terms "set", "install", "connect", "connected", "provided with", "laid", and "arranged" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, and can be welding, riveting, bolting, threading, and other commonly used connection means in the field. This connection can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal connection of two elements.

[0038] Example 1 like Figure 1-Figure 6 As shown, a passive ventilation system for a roadbed adopted in this embodiment includes: A first pipe 11, used to connect one end of the ventilation channel in the roadbed 0, wherein the first pipe 11 is provided with an exhaust port 13; A blade 2, wherein the blade 2 is connected to a rotating shaft 21; The centrifugal impeller 3 is disposed in the first pipe 11 corresponding to the air outlet 13 , and the rotation of the blades 2 can enable the rotating shaft 21 to drive the centrifugal impeller 3 to rotate.

[0039] In some embodiments, the first pipe 11 can be directly connected to the ventilation duct or through other connecting structures, such as using the second pipe 12. The second pipe 12 and the first pipe 11 can be directly connected or connected through a bend pipe.

[0040] In some embodiments, in order to reduce the arrangement of blades 2, 2-3 second pipes 12 can be connected to the same first pipe 11 through a tee. Figure 1 , Figure 4 , Figure 5 shown.

[0041] In some embodiments, the second pipe 12 and the ventilation channel may be connected by plugging, threading, flange connection, welding, etc. The detachable connection facilitates cleaning, replacement and on-site adaptive installation of the pipe.

[0042] In some embodiments, the rotating shaft 21 of the blade 2 is used to drive the centrifugal impeller 3 to rotate, and can be directly connected or connected through various existing transmission components. For example, the rotating shaft 21 is connected to the input shaft of the speed increasing gearbox 5, and the output shaft of the speed increasing gearbox 5 is connected to the centrifugal impeller 3. Figure 3 shown.

[0043] In some embodiments, the relative arrangement positions of the blades 2 and the exhaust port 13 are not limited, as long as the blades 2 can be exposed to the wind in the natural environment. The number of the exhaust ports 13 can also be set as needed, and is not limited to only one.

[0044] In some embodiments, the blade 2 may be located above the air outlet 13, that is, above the centrifugal impeller 3. Figure 1-4 As shown, after the system is installed, the blades 2 are located above the exhaust port 13, and the exhaust port 13 is arranged at a height higher than the road surface, so that the blades 2 and the exhaust port 13 are both higher than the road surface.

[0045] In some embodiments, the shape, size, arrangement and other parameters of the blades 2 are not limited, as long as they can be rotated by wind, and the structural parameters are suitable for improving the efficiency of wind utilization. The blades 2 can be arranged in the manner of an axial flow fan, a centrifugal fan, etc. Exemplarily, the shaft 21 is arranged along the height direction of the road, that is, the shaft 21 is arranged vertically after being installed in place, so as to better receive the wind force of the vehicle. The blades 2 are connected to the shaft 21 through a connecting rod 22, and the connecting rod 22 can be arranged along the radial direction of the shaft 21. The number and position of the connecting rod 22 can be determined according to the shape, size and number of the blades 2.

[0046] In some embodiments, the connection between the connecting rod 22, the rotating shaft 21 and the blade 2 can be a detachable connection to facilitate maintenance and replacement.

[0047] In some embodiments, the shape of the blade 2 may be S-shaped, such as Figure 7 As shown. It can also be a rectangular plate, there are several rectangular plates, and the rectangular plates can be arranged with the plate surface parallel to the rotating shaft 21, such as Figure 1-3 As shown, the blades 2 may be arranged along the radial direction of the rotating shaft 21, or may be arranged at an angle to the rotating shaft 21. The blades 2 may also be lift blades, that is, in the shape of an airfoil.

[0048] In some embodiments, the number of blades 2 can be determined based on factors such as the space at the arrangement location. For example, 3-8 blades 2 can be selected, and the blades 2 are evenly distributed circumferentially along the rotating shaft 21 to facilitate the blades 2 to rotate under the action of wind force from any wind direction.

[0049] In some embodiments, the other end of the ventilation channel is provided with a bell mouth 4, such as Figure 4 and Figure 6 As shown, the larger end of the bell mouth 4 is used for air intake, and the bell mouth 4 can be externally connected to the ventilation channel or connected to the inner wall of the ventilation channel. The bell mouth 4 is preferably set in the main windward direction, that is, the line of the bell mouth 4 pointing to the second pipeline 12 is the downwind direction, so as to make full use of wind resources. If the angle between the wind direction and the roadbed in the area is not obvious or is parallel to the direction of the roadbed, the installation end of the system can be arbitrarily selected according to the terrain and construction conditions.

[0050] In some embodiments, the system can be arranged along the entire length of the line, and the devices can be all arranged on the same side of the roadbed 0 based on the windward direction, such as Figure 4-5 As shown, in sections where wind resources are insufficient, the wind turbines can be staggered on both sides of the roadbed 0 to facilitate ventilation and cooling by utilizing the wind generated by driving on the lanes.

[0051] In some embodiments, the same ventilation channel can also be connected to more than two passive ventilation systems. For example, the second pipe 12 is connected to two first pipes 11 arranged at intervals, and the two first pipes 11 are arranged horizontally along the road to further improve the convection efficiency.

[0052] In some embodiments, the exhaust ports 13 of the passive ventilation systems adjacent to each other in the longitudinal direction of the line can be arranged in a height step, such as the height and direction of the exhaust port 13 of each passive ventilation system are adapted to the blades 2 of the passive ventilation system on the adjacent side. Figure 8-9 As shown, the extracted wind can be further utilized, and the continuous arrangement along the longitudinal direction can ensure ventilation efficiency in some locations where wind force is limited (such as with obstructions, etc.), avoid ventilation dead corners in individual ventilation ducts, and prevent local locations from melting and sinking due to poor ventilation and cooling effects. The stepped arrangement can be arranged in local sections, and does not require a stepped arrangement along the entire line. Of course, the exhaust ports 13 of two passive ventilation systems adjacent to each other in the horizontal direction can also be arranged in height steps. Of course, the height of the exhaust port 13 can also remain unchanged, while the arrangement height of the blades 2 can be adjusted.

[0053] The passive ventilation system for the roadbed described in the present invention uses blades 2 to drive exhaust under the action of wind, which can effectively utilize the abundant wind energy resources in the plateau area, and systematically improve the structural functions of existing and newly built ventilated roadbeds without the need for additional power, with a higher cost-effectiveness ratio, reducing interference and damage to the environment, and helping to meet environmental protection requirements; for newly built ventilated roadbeds, the refrost time can be shortened, and for existing ventilated roadbeds, the work efficiency can be improved, and the ventilation and temperature control efficiency of the ventilated roadbed can be enhanced, which has a good promotion prospect.

[0054] Example 2 A construction method of a passive ventilation system for a roadbed, applied to a passive ventilation system for a roadbed as in Example 1, comprises the following steps: S1. Determine the connection position of the first pipeline 11 according to the wind direction, and determine the arrangement position of the exhaust port 13 according to the height of the roadbed 0, the wind direction and the position of the ventilation channel; S2, assembling the first pipe 11, the blades 2 and the centrifugal impeller 3; S3. Connect the passive ventilation system to the corresponding end of the ventilation channel.

[0055] First, determine the main wind direction in the area where the roadbed 0 is located. If there is an obvious angle between the wind direction and the direction of the roadbed 0, such as an angle greater than 30°, it can be considered that there is a main windward wind direction, that is, the windward wind direction is set as the air inlet, which is used to set the bell mouth 4, and the other end of the ventilation channel is used to set this system.

[0056] The arrangement height of the exhaust outlet 13 is determined according to the height of the roadbed 0 and the position of the ventilation channel. The position of the exhaust outlet 13 can be higher than the height of the roadbed 0. The direction of the exhaust outlet 13 can be determined according to the wind direction, that is, avoid setting it against the wind, which will cause wind to enter the exhaust outlet 13. A one-way valve can also be set to avoid wind entering. The corresponding direction can also be set according to needs. The part below the exhaust outlet 13 can be buried underground according to actual conditions. If a cross slope or a curve is encountered, the ventilation roadbed will face a situation where one side is higher and the other side is lower. However, the ventilation layer is in a horizontal state during the construction process. Therefore, it is inevitable that the ventilation layer on the higher side is unobstructed, and the lower side will block the ventilation layer, resulting in poor exhaust and reduced efficiency and intensity of frozen soil control. By using this device, it is only necessary to ensure that the exhaust outlet 13 and the part above it are located above the ground, which can effectively solve the problem of poor exhaust on cross slopes and curves.

[0057] The first pipe 11, the second pipe 12, the blades 2, the centrifugal impeller 3 and the speed increasing gearbox 5 are assembled according to the preset arrangement height and orientation of the air outlet 13, and then installed at the corresponding end of the ventilation pipe.

[0058] The installation of the bell mouth 4 can be carried out after the air inlet is determined.

[0059] The construction method of the passive ventilation system of the roadbed described in the present invention has a passive design, a simple structure, less on-site assembly workload, and is installed on the exposed part of the roadbed. It can be effectively applied to existing and newly built ventilated roadbed structures in permafrost areas, increase the ventilation volume of the ventilated roadbed, reduce the impact of the highway in the permafrost area on the heat balance of the underlying frozen soil, and increase the service life of the ventilated roadbed; the basic system of the existing ventilation road is easy to install, the construction period is short, it does not affect normal traffic, and does not require construction processes such as excavation and backfilling.

[0060] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A passive ventilation system for roadbed, characterized in that: include: A first pipe (11) is used to connect one end of a ventilation channel in the roadbed (0), wherein the first pipe (11) is provided with an exhaust port (13); A blade (2), wherein the blade (2) is connected to a rotating shaft (21); A centrifugal impeller (3) is arranged in the first pipe (11) corresponding to the air outlet (13), and the rotation of the blades (2) can cause the rotating shaft (21) to drive the centrifugal impeller (3) to rotate.

2. A passive ventilation system for roadbed according to claim 1, characterized in that: The blades (2) are located above the air outlet (13), and the air outlet (13) is arranged at a height higher than the road surface.

3. A passive ventilation system for roadbed according to claim 2, characterized in that: The rotating shaft (21) is arranged along the height direction of the road, the blades (2) are connected to the rotating shaft (21) via connecting rods (22), and the connecting rods (22) are arranged along the radial direction of the rotating shaft (21).

4. A passive ventilation system for roadbed according to claim 3, characterized in that: The blade (2) is an S-shaped or lift blade.

5. A passive ventilation system for roadbed according to claim 3, characterized in that: The blades (2) are rectangular plates, the plate surfaces of the blades (2) are arranged along the radial direction of the rotating shaft (21), there are 3 to 8 blades (2), and the blades (2) are evenly distributed along the circumference of the rotating shaft (21).

6. A passive ventilation system for roadbed according to any one of claims 1 to 5, characterized in that: The rotating shaft (21) is connected to the centrifugal impeller (3) via a speed increasing gear box (5).

7. A passive ventilation system for roadbed according to claim 6, characterized in that: A bell mouth (4) is provided at the other end of the ventilation channel, and the larger end of the bell mouth (4) is used for air intake.

8. A passive ventilation system for roadbed according to claim 6, characterized in that: It also comprises a second pipe (12), wherein the first pipe (11) is connected to the ventilation channel via the second pipe (12), and 2 to 3 second pipes (12) are connected to the same first pipe (11).

9. A passive ventilation system for roadbed according to claim 6, characterized in that: The air outlet (13) faces the adjacent blades (2) of the passive ventilation system.

10. A construction method for a passive ventilation system of a roadbed, characterized in that: A passive ventilation system for a roadbed as claimed in any one of claims 1 to 9 comprises the following steps: S1. Determine the connection position of the first pipeline (11) according to the wind direction, and determine the arrangement position of the exhaust port (13) according to the height of the roadbed (0), the wind direction and the position of the ventilation channel; S2, assembling the first pipe (11), the blades (2) and the centrifugal impeller (3); S3. Connect the passive ventilation system to the corresponding end of the ventilation channel.

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