Noise reduction centrifugal fan

Abstract

The invention relates to the technical field of fluid machinery, in particular to a noise reduction centrifugal fan which comprises a cylindrical machine shell, an air inlet is formed in the side wall of the machine shell, a motor is connected to the side wall, away from the air inlet, of the machine shell, and the output end of the motor penetrates through the machine shell to be fixedly provided with an impeller. An air outlet is formed in the machine shell in the circumferential tangential direction, and a filter screen is fixedly installed at the air outlet. The cleaning device is installed at the air outlet of the noise reduction centrifugal fan and can automatically detect whether the filter screen is blocked or not, and when it is detected that the filter screen is blocked, the filter screen is cleaned under the conditions that the machine is not stopped and operation of the machine is not affected; the problems that flow is reduced due to blockage of a filter screen of the noise-reduction centrifugal fan, and the service life of the noise-reduction centrifugal fan is shortened and noise is increased due to vibration increase of the noise-reduction centrifugal fan are solved.

Description

Technical Field

[0001] This invention relates to the field of fluid machinery technology, specifically to a noise-reducing centrifugal fan. Background Technology

[0002] Existing noise-reducing centrifugal fans consist of a casing, main shaft, impeller, bearing transmission mechanism, and motor. The noise-reducing centrifugal fan uses the impeller to convert the axial movement of the inhaled gas into rotation around the impeller axis. Then, by gradually increasing the cross-sectional area of ​​the pipe, the gas is decelerated and pressurized. Finally, the compressed gas is discharged. It is commonly used for ventilation, dust removal, and cooling in areas such as factories, tunnels, and mines.

[0003] Noise-reducing centrifugal fans typically have filters installed at the outlet to reduce dust content in the exhaust gas. However, with prolonged use, dust accumulates on the filters. Clogged filters not only reduce airflow and cooling efficiency but also increase vibration and shorten the fan's lifespan. Current solutions involve operators periodically inspecting and cleaning the filters. However, this method is not timely if the fan needs to operate continuously for extended periods, such as in mine ventilation. Furthermore, if problems are discovered during operation, the fan must be shut down for cleaning, posing a serious safety hazard to miners.

[0004] To address this, a noise-reducing centrifugal fan is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a noise-reducing centrifugal fan. By installing a cleaning device at the air outlet of the noise-reducing centrifugal fan, the cleaning device can automatically detect whether the filter screen is clogged, and clean the filter screen without stopping the machine or affecting its operation when the filter screen is detected to be clogged, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A noise-reducing centrifugal fan, comprising:

[0008] The housing is cylindrical, with an air inlet on the side wall of the housing, a motor connected to the side wall of the housing away from the air inlet, an impeller fixedly installed through the output end of the motor, and an air outlet opened along the circumferential tangent of the housing, with a filter screen fixedly installed at the air outlet.

[0009] Also includes:

[0010] A cleaning device is installed at the air outlet. The cleaning device is used to clean the filter screen without stopping the machine when the filter screen is clogged with dust, causing the flow rate of the noise-reducing centrifugal fan to decrease.

[0011] When the noise-reducing centrifugal fan is working, the motor drives the impeller to rotate. The impeller can draw in air from the air inlet, and then use centrifugal force to convert the axially moving air into air rotating along the axis. Since the impeller is eccentrically installed in the casing, and in combination with the shape of the casing, the air speed decreases while the pressure increases when rotating in the casing, and finally it is output from the exhaust port on the casing.

[0012] Since the air intake of a noise-reducing centrifugal fan comes entirely from its surrounding environment, it may contain a large or small amount of dust and impurities. To prevent these impurities from clogging the air supply pipes, a filter is typically installed at the outlet. However, after a period of use, the filter becomes clogged with dust and impurities, reducing the fan's output flow and increasing its vibration. This vibration not only increases noise but also accelerates wear and tear on internal components, reducing the fan's lifespan. Current solutions involve manual periodic inspection and cleaning of the filter, but this method lacks the ability to detect problems promptly, leading to frequent filter clogging. Furthermore, when a clogged filter is discovered, the fan must be shut down before the filter can be removed for cleaning, and then reinstalled at the outlet before the fan can resume operation. This inevitably impacts the fan's efficiency.

[0013] Therefore, this invention installs a cleaning device at the air outlet of the noise-reducing centrifugal fan. The cleaning device can automatically detect whether the filter screen is clogged with dust and impurities. When the filter screen is clogged, the cleaning device will remove the dust and impurities on the filter screen without shutting down the noise-reducing centrifugal fan or affecting the air delivery quality of the noise-reducing centrifugal fan. This allows the output flow of the noise-reducing centrifugal fan to return to normal and stops vibrating. This ensures that the noise of the noise-reducing centrifugal fan can be stabilized within a reasonable range, and also guarantees the working efficiency and service life of the noise-reducing centrifugal fan.

[0014] Preferably, the cleaning device includes a detection unit, a replacement unit, and a cleaning unit. A detection unit for detecting whether the filter is clogged is installed on the side wall of the housing near the air outlet. A replacement unit for replacing the clogged filter with a clear filter is installed at the air outlet. A cleaning unit for cleaning the replaced clogged filter is installed on the side wall of the replacement unit.

[0015] The cleaning device of this invention consists of three parts: a detection unit, a replacement unit, and a cleaning unit. When the detection unit detects a clogged filter, it activates the replacement unit. To ensure the continuous operation of the noise-reducing centrifugal fan without affecting its efficiency, and to prevent water from entering the air supply pipe during filter cleaning, multiple filter screens are installed at the exhaust port of the noise-reducing centrifugal fan. These filter screens are used alternately. The replacement unit replaces the filter screens after the detection unit is triggered. Once the replacement unit stops operating, the cleaning unit cleans the clogged filter screens, preparing them for the next use. The seamless connection between the filter screens allows the cleaning device to clean the filter screens without stopping the noise-reducing centrifugal fan, while maintaining a stable output flow rate.

[0016] Preferably, the detection unit includes a protective shell installed near the air outlet of the housing. A through hole is provided on the side wall of the housing corresponding to the protective shell. A piston is slidably installed inside the protective shell. A push rod is installed at the end of the piston away from the through hole. Multiple springs are evenly connected on the inner side wall of the protective shell away from the through hole. The other end of the springs is connected to the piston. A contact switch for triggering the contact unit is installed at the end of the protective shell away from the through hole.

[0017] When the filter is clogged, the gas inside the casing cannot escape, causing an increase in internal pressure. As the internal pressure gradually increases, it pushes the piston to compress the spring and move closer to the contact switch. A sealing ring is installed on the side wall where the piston contacts the protective casing, preventing gas from entering the casing during piston movement and stillness. When the pressure reaches a set value, the piston continues to move closer to the contact switch until the push rod touches it. Once the contact switch is activated, the replacement unit is started. When the replacement unit replaces the clogged filter with a clear one, the gas inside the noise-reducing centrifugal fan is released, reducing the internal pressure. The spring then pushes the piston away from the contact switch until the spring force balances the air pressure. The spring constant is positively correlated with the set air pressure; the higher the set pressure, the higher the spring constant. The protective casing can be made of transparent material for easy inspection of the seal between the piston and the inner wall of the casing.

[0018] Furthermore, the detection unit of the present invention can replace pressure detection with speed detection. When filtering gas, the filter screen only has one side for air intake and the other side for air exhaust. A fan blade is rotatably installed on the inner wall of the noise reduction centrifugal fan near the air exhaust side of the filter screen. The fan blade will continuously rotate under the action of the output gas. A sensor for detecting the fan blade speed is installed near the fan blade. When the filter screen is clogged, the gas flow through the filter screen decreases and the fan blade speed decreases. When the fan blade speed is less than the set value, the replacement device will be activated.

[0019] Furthermore, both the inner cavity of the protective shell and the piston are non-rotating bodies.

[0020] To prevent the piston from rotating during movement and thus accelerating the wear of the piston seals, the protective shell and piston can be machined into non-rotational shapes, such as squares, rectangles, and hexagons. This prevents the piston from rotating during movement and increases the service life of the piston seals.

[0021] Preferably, the replacement unit includes a short pipe installed at the air outlet, the bottom of the short pipe having multiple through holes II, each through hole II having a filter screen slidably installed in it, a housing being installed on the outer bottom wall of the short pipe, each filter screen being located inside the housing, a drain outlet being provided at the center of the bottom wall of the housing, and multiple moving parts for pushing the filter screens being symmetrically installed on the outer bottom wall of the housing, the output end of each moving part being connected to the filter screen;

[0022] The moving part includes any one of a pneumatic cylinder, a hydraulic cylinder, and an electric push rod.

[0023] When the contact switch is triggered, the output end of one of the moving parts extends, driving the permeable filter screen through the second through-hole into the short pipe, eventually contacting the top of the inner wall of the short pipe. At this point, the moving part stops, but part of the filter screen remains inside the second through-hole, securing the filter screen and blocking the through-hole to prevent gas from entering the housing and wasting the output flow of the noise-reducing centrifugal fan. When the moving part that pushes the clean filter screen stops, the moving part that blocks the filter screen starts moving, its output end retracting to completely insert the filter screen into the housing before stopping. At this point, part of the filter screen remains inside the second through-hole, but not higher than the bottom inner wall of the short pipe, blocking the through-hole to prevent gas from entering the housing and wasting the output flow of the noise-reducing centrifugal fan. Because the width of the second through-hole is equal to the width of the filter screen and the width of the filter screen's housing support, while the width of the filter part is smaller than the width of the second through-hole, dust and impurities on the filter screen are not scraped off by the second through-hole when the filter screen moves downwards. The filter replacement sequence of this invention prevents unfiltered gas from entering the gas delivery pipeline during filter replacement, ensuring the quality of the output gas even when the noise-reducing centrifugal fan is continuously running and the filter is replaced. Furthermore, the short pipe and shell of this invention can be made of transparent material for easy subsequent maintenance.

[0024] The moving part of this invention refers to a mechanism capable of reciprocating movement, such as a cylinder, hydraulic cylinder, and electric push rod. Furthermore, this invention can install a magnet and a spring at the bottom of the filter screen and an electromagnet at the bottom of the housing. When the electromagnet is activated, the repulsive force between the magnets drives the filter screen to move away from the electromagnet. When the electromagnet is deactivated, the spring returns the filter screen to its initial position. However, this method has poor stability and is not as stable as a reciprocating movement mechanism.

[0025] For ease of understanding, the drawings of this invention show two filter screens, but the number can be adjusted according to the actual situation in actual production.

[0026] Furthermore, the filter screen is fixedly installed with a fixing plate at both ends to further seal the through hole two, and the width of the fixing plate is greater than the width of the through hole two.

[0027] Because the width of the fixing plate is greater than that of through hole two, the fixing plates at both ends of the filter screen can completely cover through hole two when the filter screen stops moving. A layer of sealing material is fixedly applied to both sides of the fixing plate to further increase the seal between the short pipe and the housing, preventing gas from the short pipe from entering the housing and causing waste. It also prevents water from splashing into the short pipe during filter cleaning, thus preventing contamination of the output gas. Simultaneously, it reduces the required clearance between the filter screen and through hole two, lowering production difficulty.

[0028] Furthermore, the short tube has multiple grooves symmetrically formed on its inner top and bottom walls to mate with the fixing plate, and the depth of the grooves is greater than or equal to the thickness of the fixing plate.

[0029] To increase the stability of the filter screen and reduce the obstruction of gas by useless parts of the filter screen, thus affecting the gas delivery efficiency, grooves are made on the inner sidewalls of the short pipe near and away from the second through hole. The length and width of the grooves are equal to the length and width of the fixed plate, and the depth of the grooves is greater than the depth of the fixed plate, so that the fixed plate can be completely nested in the grooves. This reduces the obstruction of the fixed plate to the output airflow and also reduces the volume of gas passing through the gap between the filter screen and the short pipe, allowing the gas to be effectively filtered.

[0030] Furthermore, the filter screen and the fixing plate are provided with sliding grooves on the outer walls of the vertical direction where they contact the short pipe, and a guide rail that cooperates with the sliding groove is fixedly installed on the inner wall of the short pipe.

[0031] Because the filter screen is subjected to the impact of the output gas when it is raised and lowered, in order to increase the stability of the filter screen during movement and prevent the filter screen from deforming, sliding grooves are opened on the outer side wall of the filter screen support shell parallel to the direction of movement. Guide rails that cooperate with the sliding grooves are fixedly installed on the inner side wall of the short pipe. When the filter screen moves, the sliding grooves are nested on the guide rails and move. The cooperation between the sliding grooves and the guide rails provides support for the filter screen. At the same time, the cooperation between the sliding grooves and the guide rails can also reduce the volume of gas passing through the gap between the filter screen and the short pipe, so that the gas can be effectively filtered.

[0032] Preferably, the cleaning unit includes multiple nozzles symmetrically installed on the inner sidewall of the housing parallel to the filter screen, and the other end of each nozzle is connected to a water pipe, and the nozzles are arranged in multiple horizontal layers.

[0033] Since the filter screen only has one side for air intake and one side for air exhaust when filtering gas, most of the dust and impurities filtered by the screen will accumulate on the air intake side. Therefore, installing a spray nozzle on the side of the housing near the air exhaust side of the filter screen can better clean the mesh of the filter screen, while installing a spray nozzle on the side of the housing near the air intake side of the filter screen can better clean the surface of the filter screen. Together, they can effectively restore the filter screen to its original clarity. To clean every part of the filter screen thoroughly, multiple nozzles need to be installed on the side wall of the housing, forming a multi-layered horizontal arrangement. The nozzles can be funnel-shaped to increase the coverage area of ​​each nozzle, reduce the number of nozzles, and lower costs. Generally, the filter screen needs to be replaced at relatively long intervals. The water remaining on the filter screen after cleaning can evaporate in a T-shape. However, if used in harsh environments with heavy dust, the filter screen needs to be replaced and cleaned more frequently. In this case, an air supply pipe can be installed on the side wall of the housing to supply air into the housing, and the air will be discharged from the drain pipe, increasing airflow and the rate of water evaporation.

[0034] Once both moving parts in the replacement unit have stopped operating, the control system activates the water supply system. Water flows through the pipes into the nozzles, is pressurized at the nozzles, and then sprays out. After a set time, the control system shuts off the water supply system, and the nozzles stop spraying water. At this point, most of the filter screen has been cleaned and is ready for the next replacement. The cleaning water and the removed dust and impurities are drained away from the drain outlet at the center of the bottom of the housing.

[0035] It should be noted that each set of nozzles can only be used to clean two filter screens. More than two will create a blockage. If a large number of filter screens are actually needed, the filter screens need to be separated into pairs and surrounded by the housing.

[0036] Furthermore, the inner bottom wall of the shell is an inverted cone shape.

[0037] To prevent the water and dust from accumulating at the bottom of the housing, increasing the weight of the cleaning device, or causing a large amount of dust and impurities to enter the drain at once and clog it, the bottom wall of the housing can be made into an inverted cone shape, so that the drain is located at the lowest point inside the housing, facilitating water flow.

[0038] Furthermore, the upper sidewall near the drain outlet fixing plate is provided with an inclined surface for easy drainage, and a conical groove that matches the inclined surface is provided on the outer bottom wall of the short pipe.

[0039] Water and dust residue from cleaning the filter screen remain on the upper surface of the fixing plate near the drain outlet, causing gaps between the fixing plate and the short pipe during subsequent use, resulting in an inadequate seal. Therefore, this invention features an inclined surface on the fixing plate near the drain outlet to facilitate water flow, and a tapered groove on the outer wall of the short pipe to allow for better engagement between the fixing plate and the outer wall of the short pipe, ensuring a tight seal.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. The detection unit automatically monitors the filter for blockages at all times. When the filter is clogged, the air pressure inside the casing increases, pushing the piston towards the contact switch and ultimately triggering it. Once the contact switch is activated, the replacement device is started to replace the clogged filter with a clear one. Compared to manual periodic inspections, this method allows for timely detection and resolution of problems, ensuring the stability of the output gas flow from the noise-reducing centrifugal fan. It also avoids increased vibration in the centrifugal fan caused by filter blockage, which could lead to increased noise and accelerated wear of components.

[0042] 2. Multiple filters are used alternately. Only after a clear filter is fully in place will a clogged filter move into the housing for cleaning. Therefore, this invention allows for filter replacement and cleaning without shutting down the machine, ensuring the working efficiency of the noise-reducing centrifugal fan. Furthermore, during filter replacement, unfiltered gas will not enter the gas delivery pipe, guaranteeing the quality of the gas output from the noise-reducing centrifugal fan.

[0043] 3. Install fixing plates at both ends of the filter screen to further increase the seal between the short pipe and the housing, preventing the gas output from the noise-reducing centrifugal fan from entering the housing and causing waste. At the same time, set an inclined surface on the fixing plate to facilitate the flow of water droplets after cleaning the filter screen, preventing water droplets and impurities from remaining on the fixing plate and affecting the sealing of the fixing plate through hole two. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0045] Figure 2 for Figure 1 Partial sectional view of AA;

[0046] Figure 3 This is a top view of the present invention;

[0047] Figure 4 for Figure 3 Enlarged view of a section at point B in the middle;

[0048] Figure 5 for Figure 3 Enlarged view of a section at point C;

[0049] Figure 6 for Figure 2 Enlarged view of a section at point D;

[0050] Figure 7 This is a schematic diagram of the filter screen structure of the present invention;

[0051] Figure 8 This is a schematic diagram of the housing structure of the present invention.

[0052] In the diagram: 1. Housing; 2. Motor; 3. Air outlet; 4. Filter screen; 401. Slide groove; 5. Protective shell; 601. Through hole one; 602. Through hole two; 7. Piston; 8. Push rod; 9. Spring; 10. Contact switch; 11. Short pipe; 1101. Groove; 1102. Guide rail; 12. Housing; 1201. Drain outlet; 13. Moving part; 14. Fixing plate; 15. Nozzle; 16. Water pipe; 17. Slide groove. Detailed Implementation

[0053] The following will be combined with the appendix of the present invention. Figures 1 to 8The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the embodiments of the present invention include, but are not limited to, the embodiments described below. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] The terms "first" and "second" appearing in this application are used only to describe the order of objects and not to indicate relative importance or the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the stated features. The term "multiple" appearing in this application means at least two.

[0055] Example 1: When the air pressure is used to detect whether the filter screen 4 is clogged.

[0056] When the filter screen 4 is clogged with dust and impurities, the gas inside the casing 1 cannot be discharged from the casing 1, resulting in an increase in the air pressure inside the casing 1. As the air pressure inside the housing 1 gradually increases, the air pressure will push the piston 7 to squeeze the spring 9 and move it closer to the contact switch 10. When the air pressure reaches the set value, the piston 7 will continue to move closer to the contact switch 10 and eventually make the push rod 8 touch the contact switch 10. When the contact switch 10 is touched, the moving part 13 of the transparent filter screen 4 will be activated. The output end of the moving part 13 will extend and drive the transparent filter screen 4 from the housing 12 through the through hole 602 into the short tube 11, and finally make the fixing plate 14 nested in the groove 1101 of the inner side wall of the short tube 11. At this time, the moving part 13 stops, and part of the filter screen 4 is still located in the through hole 602. When the moving part 13 connected to the transparent filter screen 4 stops running, the moving part 13 connected to the blocked filter screen 4 starts, and its output end retracts and drives the filter screen 4 to completely enter the housing 12 before stopping. At this time, part of the filter screen 4 is still located in the through hole 602 but not higher than the inner bottom wall of the short tube 11. After replacing the clogged filter screen 4 with a clear filter screen 4, the gas inside the noise-reducing centrifugal fan can be discharged, reducing the air pressure inside the fan. Spring 9 will push piston 7 away from contact switch 10 until the spring force of spring 9 balances with the air pressure. Once both moving parts 13 have completely stopped operating, the control system activates the water supply system. Water flows through water pipe 16 into nozzle 15, and is finally pressurized and sprayed out at nozzle 15. Under the action of the water flow, the dust and impurities on filter screen 4 become loose and are eventually washed away. After a set time, the control system shuts off the water supply system, and nozzle 15 stops spraying water. At this point, most of filter screen 4 has been cleaned and is clear again, ready for the next replacement. The cleaning water and the washed-off dust and impurities are discharged from the drain port 1201 at the center of the bottom of housing 12.

[0057] Example 2: When the rotation speed is used to detect whether the filter screen 4 is clogged.

[0058] When filtering gas, filter 4 has only one side for air intake and the other side for air outlet. A fan blade is rotatably installed on the inner wall of the noise-reducing centrifugal fan near the air outlet side of filter 4. The fan blade will continuously rotate under the action of the output gas. A sensor for detecting the fan blade speed is installed near the fan blade. When filter 4 is clogged, the gas flow through filter 4 decreases and the fan blade speed decreases. When the fan blade speed is less than the set value, the replacement device will be activated. The remaining steps are the same as in Embodiment 1, and will not be described in detail here.

[0059] Compared to Embodiment 1, using rotational speed to detect whether filter 4 is clogged takes up more space, resulting in a larger overall size of the noise-reducing centrifugal fan. Additionally, the fan blades somewhat obstruct the outward flow of gas. However, since the gas acting on the fan blades is filtered, their rotation is not affected by other factors, such as dust increasing friction between the fan blades and the shaft. Since piston 7 directly contacts the gas inside housing 1, dust accumulation in through-hole 601 may affect the movement of piston 7 or increase friction, reducing the lifespan of the sealing ring on piston 7. Therefore, compared to Embodiment 1, Embodiment 2 has a longer service life and lower maintenance costs.

[0060] Working principle:

[0061] When the filter screen 4 becomes clogged, the air pressure pushes the piston 7 towards the contact switch 10, eventually causing the push rod 8 to trigger the contact switch 10. Once the contact switch 10 is triggered, the moving part 13 is activated, moving the clear filter screen 4 into the short pipe 11 and the clogged filter screen 4 into the housing 12. After the moving part 13 stops operating, the control system controls the nozzle 15 to spray water to clean the clogged filter screen 4, ready for the next use.

[0062] Although various embodiments of the present invention have been listed and described, it will be understood by those skilled in the art that many changes, modifications, substitutions and alterations can be made to the state and components of these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A noise-reducing centrifugal fan, comprising: The housing (1) is cylindrical. An air inlet is provided on the side wall of the housing (1). A motor (2) is connected to the side wall of the housing (1) away from the air inlet. An impeller is fixedly installed through the housing (1) at the output end of the motor (2). An air outlet (3) is provided along the circumferential tangent direction of the housing (1). A filter screen (4) is installed at the air outlet (3). Its characteristic is that it further includes: A cleaning device is installed at the air outlet (3). The cleaning device is used to clean the filter screen (4) without stopping the machine when the filter screen (4) is blocked by dust, which reduces the flow rate of the noise reduction centrifugal fan.

2. A noise reducing centrifugal fan as claimed in claim 1, wherein: The cleaning device includes a detection unit, a replacement unit and a cleaning unit. A detection unit for detecting whether the filter screen (4) is clogged is installed on the side wall of the housing (1) near the air outlet (3). A replacement unit for replacing the clogged filter screen (4) with a clear filter screen (4) is installed at the air outlet (3). A cleaning unit for cleaning the replaced clogged filter screen (4) is installed on the side wall of the replacement unit. The detection unit includes a protective shell (5) installed on the housing (1) near the air outlet (3). A through hole (601) is provided on the side wall of the housing (1) corresponding to the protective shell (5). A piston (7) is slidably installed inside the protective shell (5). A push rod (8) is installed on the end of the piston (7) away from the through hole (601). A plurality of springs (9) are evenly connected on the inner side wall of the protective shell (5) away from the through hole (601). The other end of the springs (9) is connected to the piston (7). A contact switch (10) for triggering the replacement unit is installed on the inner wall of the end of the protective shell (5) away from the through hole (601).

3. A noise reducing centrifugal fan as claimed in claim 2, wherein: The inner cavity of the protective shell (5) and the piston (7) are both non-rotating bodies.

4. A noise reducing centrifugal fan as claimed in claim 2, wherein: The replacement unit includes a short pipe (11) installed at the air outlet (3). The bottom of the short pipe (11) has multiple through holes (602). A filter screen (4) is slidably installed in each of the through holes (602). A housing (12) is installed on the outer bottom wall of the short pipe (11). Each filter screen (4) is located inside the housing (12). A drain outlet (1201) is opened at the center of the bottom wall of the housing (12). Multiple moving parts (13) for pushing the filter screen (4) are symmetrically installed on the outer bottom wall of the housing (12). The output end of the moving part (13) is connected to the filter screen (4). The moving part (13) includes any one of a cylinder, a hydraulic cylinder, and an electric push rod.

5. A noise reducing centrifugal fan as claimed in claim 4, wherein: The filter screen (4) is fixedly installed at both ends with a fixing plate (14) for further sealing the through hole two (602), and the width of the fixing plate (14) is greater than the width of the through hole two (602).

6. A noise reducing centrifugal fan as defined in claim 4, wherein: The filter screen (4) and the fixing plate (14) are provided with grooves (17) on the outer side wall in the vertical direction where they contact the short pipe (11), and a guide rail (1102) that cooperates with the groove (17) is fixedly installed on the inner side wall of the short pipe (11).

7. A noise reducing centrifugal fan as claimed in claim 5, wherein: The short tube (11) has a plurality of grooves (1101) symmetrically formed on its inner top and bottom walls to cooperate with the fixing plate (14), and the depth of the grooves (1101) is greater than or equal to the thickness of the fixing plate (14).

8. A noise reducing centrifugal fan as defined in claim 2 wherein: The cleaning unit includes multiple nozzles (15) symmetrically installed on the inner sidewalls of the housing (12) and the filter screen (4), with the other end of each nozzle (15) connected to a water pipe (16). The nozzles (15) are arranged in multiple horizontal layers.

9. A noise reducing centrifugal fan as claimed in claim 8, wherein: The inner bottom wall of the shell (12) is inverted conical.

10. A noise-reducing centrifugal fan according to claim 8, characterized in that: The upper side wall of the fixing plate (14) near the drain outlet (1201) is provided with an inclined surface that facilitates drainage, and a conical groove that matches the inclined surface is provided on the bottom outer wall of the short pipe (11).

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