FFU unit airflow uniform structure

Abstract

This invention discloses an airflow equalization structure for an FFU (Fan Filter Unit), including a housing and a fan. The fan is fixedly installed on the housing. A perforated plate flow equalizer is also provided, fixedly installed on the fan's outlet, completely covering the outlet. The perforated plate flow equalizer has several outlet holes. The airflow discharged from the fan outlet passes through these holes. This invention, by adding perforated plate flow equalizers to the outlets on both sides of the internal airflow channel of the fan, ensures that the fan's airflow is evenly distributed across the filter's inlet surface. This makes the fan unit more versatile in system applications, increases the effective filtration area of ​​the high-efficiency filter, and makes the airflow distribution more uniform and stable, achieving better filtration and energy saving. It also reduces noise and is very convenient for unit modification.

Description

Technical Field

[0001] This invention relates to a rotating system, and more particularly to an airflow equalization structure for an FFU (Fan Filter Unit). Background Technology

[0002] A fan-filter unit (FFU), hereinafter referred to as an FFU unit, is a unit that combines a blower and a high-efficiency filter into one unit. Multiple units can be modularly connected for use, and multiple modular terminal air supply and filtration devices can be installed. The blower draws air in from the top of the FFU unit and blows it out through the high-efficiency filter. The filtered clean air is evenly delivered across the entire air outlet surface at a wind speed of approximately (0.45±0.1) m / s to meet the cleanliness requirements of cleanrooms. As a result, FFU fan-filter units are widely used in various levels of cleanrooms, clean benches, clean production lines, modular cleanrooms, laminar flow hoods, clean booths, and mini-environment clean areas, etc., and have a very wide range of applications.

[0003] In terms of airflow performance, FFU units primarily consist of parameters such as air volume, static pressure, and efficiency. These parameters are interrelated and mutually restrictive; a change in one parameter will affect the others. Currently, the problems with FFU units on the market include unreasonable selection of fan type and configuration of internal airflow channels. The fan and filter units often have small inlet areas and large outlet areas, resulting in long, winding, and convoluted internal airflow channels with significant airflow velocity variations and turbulence. This instability leads to substantial energy loss. Furthermore, the unreasonable design of the internal airflow guiding device causes uneven outlet airflow, preventing the high-efficiency filter from fully utilizing its effective filtration area and severely impacting the purification efficiency of cleanrooms.

[0004] Due to the limited internal space, the FFU (Fan Filter Unit) has a long, winding airflow channel, which easily leads to unstable airflow, resulting in uneven distribution of turbulence, eddies, and backflow. Furthermore, the airflow velocity is high and unevenly distributed at the channel and outlet. In the FFU unit, excessive airflow velocity at the fan outlet can affect the filter efficiency, and the localized high-speed airflow directly impacts the filter, easily damaging high-efficiency filters. Uneven airflow through the high-efficiency filters also reduces their effective filtration area, thus affecting the overall cleanliness of the cleanroom.

[0005] If the airflow channel undergoes a sudden change or a turn at too large an angle, the airflow will generate eddies, backflow, or turbulence. Furthermore, the frictional resistance of the airflow channel will lead to an increase in static pressure loss (Ps). In addition, the sudden contraction of the fan outlet and the bellows will also increase the airflow velocity, thereby increasing the velocity pressure loss (Pv).

[0006] Based on the pressure loss characteristics of the fan and ductwork, total pressure loss (Pt) = static pressure loss (Ps) + velocity pressure loss (Pv). Therefore, increasing the total pressure loss will increase the fan's kW rating and thus increase energy consumption. The pressure losses caused by these system effects can all be collectively referred to as fan system effect losses. Summary of the Invention

[0007] To overcome the above deficiencies, the present invention provides an airflow equalization structure for FFU units, which can achieve better filtration effect and save energy.

[0008] The technical solution adopted by the present invention to solve its technical problem is: an airflow equalization structure for an FFU unit, including a housing and a fan, wherein the fan is fixedly installed on the housing, and a perforated plate equalizer is also provided, wherein the perforated plate equalizer is fixedly installed on the air outlet of the fan, the perforated plate equalizer completely covers the air outlet of the fan, and a plurality of air outlet holes are formed on the perforated plate equalizer, wherein the airflow discharged from the air outlet of the fan is discharged outward through the various air outlet holes on the perforated plate equalizer.

[0009] As a further improvement of the present invention, the structure of the perforated plate flow equalizer fixedly installed on the air outlet of the fan is as follows: a connecting flange is fixedly installed on the edge of the air outlet of the fan, and the perforated plate flow equalizer is fixedly installed on the connecting flange through a connector.

[0010] As a further improvement of the present invention, at least two connecting bolts are fixedly installed on the connecting flange, and at least two mounting holes are provided on the perforated plate flow equalizer. The connecting bolts can be inserted into the mounting holes on the perforated plate flow equalizer one by one. Two mounting nuts are movably screwed onto each connecting bolt, and the perforated plate flow equalizer is tightly clamped between the two mounting nuts.

[0011] As a further improvement of the present invention, there is a set gap between the mounting hole on the perforated plate flow equalizer and the outer circumferential surface of the connecting screw, and the connecting screw can be moved or oscillated through the mounting hole.

[0012] As a further improvement of the present invention, an elastic washer is also provided. The elastic washer is tightly clamped between the perforated plate flow equalizer and the mounting nut, and there is a set gap between the inner hole of the elastic washer and the connecting screw.

[0013] As a further improvement of the present invention, the mounting hole and the inner hole of the elastic washer are any one of the following: an elongated elliptical hole, a large circular hole with a diameter larger than that of the connecting screw, or a cross hole.

[0014] As a further improvement of the present invention, the side wall of the perforated plate flow equalizer is also provided with a positioning screw hole, in which a positioning screw is movably screwed, and the tip of the positioning screw can be tightly pressed against the side wall of the connecting stud.

[0015] As a further improvement of the present invention, there are four connecting screws, which are distributed at the four corners of the perforated plate flow equalizer.

[0016] As a further improvement of the present invention, the structure in which at least two connecting screws are fixedly installed on the connecting flange is as follows: the connecting flange is provided with at least two connecting holes, and two connecting nuts are movably screwed onto each connecting screw. The connecting screws pass through the connecting holes of the connecting flange, and the connecting flange is tightly clamped between the two connecting nuts.

[0017] As a further improvement of the present invention, the perforated plate flow equalizer is a perforated plate, and the edge of the perforated plate is bent to form a fixed frame for connection with the air outlet of the fan.

[0018] The beneficial technical effects of this invention are as follows: By installing perforated plate-type flow equalizers at the air outlets on both sides of the airflow channel inside the fan, the airflow from the fan is evenly distributed onto the inlet surface of the filter, making the fan unit more versatile in system applications. Furthermore, it increases the effective filtration area of ​​the high-efficiency filter, resulting in a more uniform and stable airflow distribution. Because the airflow is more uniform and stable, its performance is effectively improved, achieving better filtration and energy savings. Moreover, adding perforated plate-type flow equalizers to the fan increases the overall manufacturing cost almost without any increase, but significantly improves airflow distribution, leading to a relative improvement in the cleanliness, temperature, and humidity of the entire cleanroom. In addition, the stable airflow distribution naturally reduces the operating noise of the unit, achieving a noise reduction effect. This invention can be used not only for manufacturing new units but also for retrofitting existing units with perforated plate-type flow equalizers, with extremely low retrofit costs and great convenience. Attached Figure Description

[0019] Figure 1 This is a front view of the traditional FFU unit structure.

[0020] Figure 2 for Figure 1 Sectional view along line AA;

[0021] Figure 3 for Figure 2 Enlarged view of section C;

[0022] Figure 4 for Figure 1 Sectional view along the BB direction;

[0023] Figure 5 This is a front view illustrating the structural principle of the present invention;

[0024] Figure 6 for Figure 5 Sectional view along the DD direction;

[0025] Figure 7 for Figure 6 Enlarged view of section F in the middle;

[0026] Figure 8 for Figure 6 Enlarged view of section G in the middle;

[0027] Figure 9 for Figure 5 EE-directed sectional view;

[0028] Figure 10 This is a front view of the perforated plate flow equalizer of the present invention;

[0029] Figure 11 This is a top view of the perforated plate flow equalizer of the present invention;

[0030] Figure 12 This is a right view of the perforated plate flow equalizer of the present invention;

[0031] Figure 13 This is a perspective view of the installation structure of the perforated plate flow equalizer of the present invention;

[0032] Figure 14 This is a schematic diagram of the flow equalization principle of the perforated plate flow equalizer on the left side of the fan outlet.

[0033] Figure 15 This is a schematic diagram of the flow equalization principle of the perforated plate flow equalizer on the right side of the air outlet of the fan.

[0034] Figure 16 This diagram shows the correspondence between the air outlet and the blow-out port of a traditional FFU unit's airflow channel.

[0035] Figure 17 This is a boundary X-axis section view of the physical model of a traditional standard FFU unit;

[0036] Figure 18 This is a boundary Y-axis section view of the physical model of a traditional standard FFU unit;

[0037] Figure 19 This is a cross-sectional view of the boundary X-axis of the physical model of the FFU unit of the present invention;

[0038] Figure 20This is a cross-sectional view of the boundary Y-axis of the physical model of the FFU unit of the present invention;

[0039] Figure 21 This is a boundary diagram of the physical model of the airflow channel inside the FFU unit.

[0040] Figure 22 The X-axis section of the simulated airflow distribution diagram for a conventional standard FFU unit;

[0041] Figure 23 Y-axis section of a simulated airflow distribution diagram for a conventional standard FFU unit;

[0042] Figure 24 This is the X-axis section of the simulated airflow distribution diagram of the FFU unit of the present invention;

[0043] Figure 25 This is the Y-axis section of the simulated airflow distribution diagram of the FFU unit according to the present invention;

[0044] Figure 26 This is a diagram showing the airflow distribution within the internal airflow channels of the present invention and a traditional FFU unit.

[0045] Casing---1 Fan---2 Perforated Plate Flow Uniformer---3

[0046] Air outlet---4 Connecting flange---5 Connecting screw---6

[0047] Mounting hole---7 Mounting nut---8 Elastic washer---9

[0048] Connecting hole---10 Connecting nut---11 Fixing frame---12

[0049] Primary filter---13 Airflow channel guide plate---14

[0050] Fan power cord and junction box---15 High-efficiency filter---16

[0051] Airflow channel---17 Positioning screw hole---18 Positioning screw---19 Detailed Implementation

[0052] Example:

[0053] A fan is a mechanical device consisting of a set of airflow power devices that are directly or indirectly driven by a set of two or more blades. It drives the impeller to rotate through a rotating shaft, thereby causing airflow. Its performance parameters can be selected according to the principle of airflow movement.

[0054] An FFU (Fan-Filter Unit) is a type of unit that mainly consists of a fan, a high-efficiency filter, a primary filter, and an airflow channel. The basic performance parameters for selecting the fan are air volume, static pressure, and fan efficiency, which are crucial factors in determining the performance of the FFU unit. Therefore, the selection of the fan, high-efficiency filter, and airflow channel is extremely important. The main performance parameters of the fan are as follows;

[0055] Air volume: Calculated from the outlet air velocity and the surface area passing through the HEPA filter. Static pressure: The sum of the pressure loss generated by the HEPA filter itself and the pressure loss in the airflow channel.

[0056] Efficiency: The efficiency of the fan is selected based on factors such as fan type and fan effect.

[0057] Shaft power: The shaft power of the fan is selected based on parameters such as the system's air volume, static pressure, and efficiency.

[0058] From the perspective of wind turbine energy, the analysis is as follows:

[0059] Based on the principles of airflow and from an energy perspective, a fan is a mechanical device that converts electrical energy into mechanical energy, thereby altering the energy of gas flow. The electrical energy component is typically expressed as output power, or the fan's shaft power. The mechanical energy component involves the rotation of the blades to create airflow. This flow is related to the gas flow rate and overcoming the pressure loss generated during the flow process. This pressure loss is called static pressure loss, or simply pressure loss. This pressure loss can be divided into two main parts.

[0060] (1). Pressure loss on the pipe wall when gaseous fluid flows in the pipe.

[0061] (2). Pressure loss generated by passing through a high-efficiency filter in the gas flow path.

[0062] The sum of the above two is also known as the static pressure loss of the wind turbine.

[0063] The relationship between the fan's shaft power, air volume, and static pressure is explained below;

[0064] The commonly used units for shaft power are W or kW, while total pressure (Pt) is equal to static pressure (Ps) + dynamic pressure (Pv).

[0065] Definition: Shaft power is directly proportional to the fluid flow rate and total pressure, while the shaft power of a fan is inversely proportional to the characteristics of the fan's motor and the efficiency of its mechanical transmission. Therefore, the equation relating the fan's shaft power to the fluid flow rate and total pressure can be established as follows:

[0066]

[0067] In the formula: η t This includes motor efficiency and mechanical transmission efficiency;

[0068] In aerodynamics, the watt number (W) is defined as: W = N·m / s, and the pressure unit Pa = N / m. 2 ;

[0069] According to the above definition, when represented by W: the unit of air volume is m. 3 / s, total pressure unit Pa = N / m 2 ;

[0070] Substituting the units into the above definition equation; that is:

[0071]

[0072] When the unit of air volume is m 3 / min (which can also be represented by CMM), and the full pressure is expressed as mmAq;

[0073] 1 mmAq = 9.8 Pa (In the engineering industry, when using this unit for conversion, the integer 10 is often used directly for calculation).

[0074] If the power of the fan is expressed in kW, then the formula for calculating the fan shaft power can be obtained after conversion using a unit coefficient; 1kW = 1000W, 1m 3 / s=60 m 3 / min, 1mmAq=9.8Pa;

[0075] Substituting into the formula, it can be expressed as:

[0076]

[0077] Formula consolidation results:

[0078] Based on the above formulas, the calculation equations for the fan's shaft power, air volume, and total pressure reveal that the parameters of the FFU unit's fan and high-efficiency filter are closely related. Furthermore, because the airflow channels of the internal guide plates in currently available FFU units are extremely narrow and the ducts are tortuous, the airflow is difficult to achieve a stable flow pattern over short distances at a certain wind speed. Therefore, the impact of system effects on the internal airflow channels and fan type of the FFU must be fully calculated to meet the initial design requirements for air volume and outlet air velocity.

[0079] During the process of a fan propelling airflow, there will be local obstructions to the airflow, increasing the airflow resistance. To meet the required air volume, this will also increase the total pressure demand of the fan. Consequently, the fan's shaft power will increase. These are all factors influenced by the fan system effect.

[0080] Therefore, the technical solution of this application is obtained by making technical improvements to the overall structure of the FFU unit. An air distribution uniform structure for an FFU unit includes a housing 1 and a fan 2. The fan 2 is fixedly installed on the housing 1. A perforated plate uniformizer 3 is also provided. The perforated plate uniformizer 3 is fixedly installed on the air outlet of the fan 2 and completely covers the air outlet of the fan 2. A plurality of air outlet holes 4 are formed on the perforated plate uniformizer 3. The airflow discharged from the air outlet of the fan 2 is discharged outward through the various air outlet holes 4 on the perforated plate uniformizer 3.

[0081] This invention installs a perforated plate flow equalizer at the air outlet of the FFU unit's fan 2. Due to the symmetrical structure of the FFU unit's air outlet, the perforated plate flow equalizer is symmetrically arranged on the air outlets on both sides of the fan 2 along the central axis of the fan 2. The perforated plate flow equalizer buffers and equalizes the airflow, allowing the high-speed airflow at the FFU unit's air outlet to be appropriately buffered and equalized. According to the principles of fluid dynamics and airflow motion, the velocity pressure of the airflow is mainly converted into static pressure by the equalization effect of the perforated plate flow equalizer. After the airflow passes through the equalization effect of the flow equalizer, the distribution of the airflow at the air outlet is improved, making the airflow distribution at the outlet more uniform and stable.

[0082] This invention achieves flow equalization and diffusion by adding a perforated plate flow equalizer to the air outlet of the airflow channel of the blower 2, making the airflow distribution more uniform and increasing the effective filtration area of ​​the high-efficiency filter. Through computational fluid dynamics (CFD) numerical simulation, it has been confirmed that this invention can improve the operating performance of the FFU unit and make the airflow distribution more uniform, effectively reducing the impact of uneven airflow distribution on the system effect.

[0083] The perforated plate flow equalizer 3 is fixedly installed on the air outlet of the fan 2 as follows: a connecting flange 5 is fixedly installed on the edge of the air outlet of the fan 2, and the perforated plate flow equalizer 3 is fixedly installed on the connecting flange 5 through a connector. A flange is added to the airflow channel outlet of the fan 2 to facilitate the fixing of the perforated plate flow equalizer at the airflow channel outlet.

[0084] At least two connecting bolts 6 are fixedly installed on the connecting flange 5. The perforated plate flow equalizer 3 has at least two mounting holes 7. The connecting bolts can be inserted one-to-one into the mounting holes 7 on the perforated plate flow equalizer 3. Two mounting nuts 8 are movably screwed onto each connecting bolt. The perforated plate flow equalizer 3 is tightly clamped between the two mounting nuts 8. The connecting bolts 6 are preferably high-tension stainless steel screws. The perforated plate flow equalizer is installed on the connecting flange 5 of the internal channel of the FFU unit by the long connecting bolts 6. The position of the perforated plate flow equalizer 3 can also be changed by adjusting the position of the two mounting nuts 8 on the connecting bolts 6, thereby adjusting the airflow direction and speed.

[0085] There is a set gap between the mounting hole 7 on the perforated plate flow equalizer 3 and the outer circumferential surface of the connecting screw 6, allowing the connecting screw 6 to move or swing through the mounting hole 7. By creating a gap between the mounting hole 7 and the connecting screw 6, the position of the mounting nut 8 on each connecting screw 6 can be adjusted, thereby changing the distance between different positions of the perforated plate flow equalizer 3 and the flange end face. This, in turn, adjusts the angle between the perforated plate flow equalizer 3 and the flange end face, thereby changing the air outlet direction and velocity of the perforated plate flow equalizer 3, making the air outlet direction and velocity more in line with actual needs.

[0086] An elastic washer 9 is also provided. The elastic washer is tightly clamped between the perforated plate flow equalizer 3 and the mounting nut 8, and there is a set gap between the inner hole of the elastic washer 9 and the connecting screw 6. The elastic washer 9 is installed on the connecting screw 6. In addition to stabilizing and preventing the threads and nut from slipping, the elastic washer 9 can also make the angle of the perforated plate flow equalizer up and down, so that its airflow direction is more in line with actual needs. After adjustment, the perforated plate flow equalizer 3 always remains tightly clamped and will not deform or loosen. The elastic washer 9 is preferably a 6mm thick flexible rubber washer, which can adjust the angle of the flow equalizer up and down, thereby finely adjusting the airflow direction and making the airflow distribution more in line with actual needs.

[0087] The mounting hole 7 and the inner hole of the elastic washer 9 can be any one of the following: an elongated elliptical hole, a large circular hole with a diameter larger than that of the connecting screw 6, or a cross-shaped hole. These various holes allow for the avoidance of the deflection angle of the connecting screw 6, enabling the perforated plate flow equalizer 3 to be finely adjusted within a certain angle range.

[0088] The perforated plate flow equalizer 3 also has positioning screw holes 18 on its side wall. Positioning screws 19 are movably screwed into these holes 18, and the tips of the positioning screws 19 can be tightly pressed against the side wall of the connecting stud. By embedding the tips of the positioning screws 19 into the side wall of the connecting screw 6, the connecting screw 6 and the perforated plate flow equalizer 3 are fixedly positioned, thereby fixing the tilt angle of the perforated plate connector and preventing changes after angle adjustment.

[0089] Four connecting screws 6 are distributed at the four corners of the perforated plate flow equalizer 3. In use, the position of the mounting nuts 8 on the four connecting screws 6 is adjusted to adjust the uniformity between the four corners of the perforated plate flow equalizer 3 and the end face of the connecting flange 5, thereby adjusting the pitch angle and left and right tilt angle of the perforated plate flow equalizer 3, so that the airflow is blown evenly and stably on the surface of the high-efficiency filter.

[0090] The structure of the connecting flange 5 having at least two connecting screws 6 fixedly installed is as follows: the connecting flange 5 has at least two connecting holes 10, and each connecting screw 6 is movably screwed with two connecting nuts 11. The connecting screw 6 passes through the connecting hole 10 of the connecting flange 5, and the connecting flange 5 is tightly clamped between the two connecting nuts 11.

[0091] The connecting screw 6 and the connecting flange 5 are fixedly positioned by two connecting nuts 11. This structure is convenient for positioning, does not require machining threaded holes on the connecting flange 5, and the connection is firm and stable. The length of the connecting screw 6 can also be adjusted. In addition, the connecting screw 6 can also be welded to the edge of the connecting flange 5 or the air outlet frame of the fan 2. This is an equivalent replacement structure that can be easily conceived by those skilled in the art based on this patent and is within the scope of protection of this patent.

[0092] The perforated plate flow equalizer 3 is a perforated plate, and the edge of the perforated plate is bent to form a fixed frame 12 for connection with the air outlet of the fan 2. The size of the perforations and the perforation rate on the plate surface can be finely adjusted according to the air volume performance and specifications of the FFU unit to meet the needs of various types of FFU units. The mounting holes 7 are located on the fixed frame 12. The holes on the perforated plate can be round, square, oval, or diamond-shaped. The plate thickness can be changed according to the air volume and air pressure. The material is mainly non-dust-generating plastic or metal plate, such as stainless steel plate, aluminum plate, galvanized steel plate, etc., such as 1mm thick stainless steel perforated plate. Specific parameters can be designed and selected according to needs.

[0093] The technical solution of this invention is obtained by optimizing the overall structure of traditional FFU units. This invention adds a perforated plate-type flow equalizer to the fan outlet, effectively improving the overall performance and energy utilization rate of the unit. This achieves energy-saving design and performance improvement of the FFU fan filter unit, and the results are verified and analyzed through simulation experiments as follows:

[0094] (I) Main Specifications of FFU Model in Numerical Simulation:

[0095] Two FFU units with similar specifications, dimensions, and air volume are selected. One of them is equipped with a perforated plate flow equalizer at the air outlet of the airflow channel, and is referred to as the FFU unit of this invention. The other unit has the same structure, except that the perforated plate flow equalizer is not installed at the airflow channel, and is referred to as the standard FFU unit.

[0096] The two FFU units were simulated using CFD numerical simulations, and the simulation results were compared to observe the airflow distribution.

[0097] (1) The FFU unit of the present invention:

[0098] Housing dimensions: 1200x600x350mm including HEPA filter (height);

[0099] HEPA filter dimensions: 1175x575x70mm; HEPA filter filtration efficiency (DOP): 99.97%@0.3μm.

[0100] High-efficiency filter outlet air velocity: 0.45m / s±20%;

[0101] Rated air volume: 1200 m³ / h;

[0102] Fan power consumption: 120W;

[0103] Flow equalizer specifications: can be selected according to air volume and size.

[0104] (2) Traditional standard FFU unit (currently the most commonly used type on the market)

[0105] Housing dimensions: 1200x600x350mm including HEPA filter (height);

[0106] HEPA filter dimensions: 1175x575x70mm; HEPA filter filtration efficiency (DOP): 99.97%@0.3μm.

[0107] High-efficiency filter outlet air velocity: 0.45m / s±20%;

[0108] Rated air volume: 1200 m³ / h;

[0109] Power consumption: 120W;

[0110] Current equalizer specifications: None.

[0111] (II) Airflow Simulation Verification:

[0112] This invention utilizes computational fluid dynamics (CFD) numerical simulation methods. Due to the fast instruction cycle of computers and the maturity of numerical analysis methods, an increasing number of numerical analysis software programs use computers for numerical analysis, simulating phenomena such as fluid motion, heat transfer, mass transfer, and chemical reactions. The numerical simulation portion of this invention primarily utilizes a software package developed by FLUENT. This software employs the basic principles of discretization and the finite volume method to solve various physical phenomena of fluids. The fields of physical quantities (such as velocity and temperature fields) that were originally continuous in space and time are replaced by a set of values ​​at a finite number of discrete points. Algebraic equations relating the values ​​of these discrete points are established according to certain principles (this is called the discretization method). Solving these algebraic equations yields approximate values ​​for the desired variables. The simulation results reflect the airflow motion inside the equipment and the airflow state at the outlet. This airflow numerical simulation selects fan-filter units with similar external dimensions and fan specifications, using fans with similar airflow, static pressure, and power consumption parameters, and combining them with high-efficiency filters of similar specifications to form a unit. Standard FFU units with the same dimensions and performance parameters, and the FFU unit of this invention + perforated plate flow equalizer, are used respectively. Airflow numerical simulations are performed under the same boundary conditions to observe the internal airflow field and the direction and stability of the outlet airflow.

[0113] Two FFU units with similar specifications, dimensions, and air volume were selected. One of them was equipped with a perforated plate flow equalizer at the air outlet of the internal airflow channel, and was referred to as the "FFU unit of this invention". The other unit had the same structure, except that it did not have a perforated plate flow equalizer at the airflow channel outlet, and was referred to as the "standard FFU unit".

[0114] (III) Numerical Simulation Physical Model and Boundary Conditions:

[0115] (1) Physical model:

[0116] A similar FFU (Fan Filter Unit) with similar airflow and external dimensions was selected, along with a similarly sized high-efficiency filter. Based on the fan structure and performance characteristics, a model measuring 1200mm in length, 600mm in width, and 350mm in height was chosen, which is also the most commonly used size on the market. The airflow inlet passes through the internal airflow duct of the unit, then through the high-efficiency filter, and finally exits from the unit's outlet. The simulated airflow channel uses the effective internal cross-sectional area as the boundary condition for the physical model in the numerical simulation.

[0117] (2) Spatial grid and visualization:

[0118] During the numerical simulation process, it was found through multiple settings that the size and number of spatial grid points affect the accuracy of the numerical simulation results. In order to balance the timeliness of the simulation and the visualization of the simulation results, it is necessary to conduct independent tests on the spatial grid points to find the most appropriate number of grid points so as to successfully observe the changes in airflow velocity and flow field.

[0119] The numerical simulation of airflow follows the actual direction of airflow, with air entering through the upper intake of the unit, passing through the airflow channel, and then exiting through the lower outlet. The entire unit's interior is separated by partitions to form an airflow space, such as... Figure 17 , Figure 18 The physical model boundary diagram is shown.

[0120] (3) Simulation of thermodynamic parameter boundary conditions:

[0121] The boundary conditions for the working fluid in the airflow simulation are set as follows: standard atmospheric pressure 101325 Pa, dry-bulb temperature 20°C, altitude 0 m, and other physical parameters under standard air conditions. The inlet air velocity is calculated based on the inlet area and air volume, while the outlet air velocity is calculated using the air volume and the outlet surface area of ​​the HEPA filter. The surface air velocity through the HEPA filter is set to 0.45 m / s for both the "conventional standard FFU unit" and the "FFU unit of this invention," serving as the boundary conditions for the working fluid. This simulation neglects the effects of air viscosity and thermal buoyancy on the convection flow.

[0122] (4) Numerical simulation airflow distribution diagram:

[0123] Numerical simulation of airflow was performed, and cross-sections (X section and Y section) were taken for both aircraft models to observe the airflow distribution.

[0124] (A). Simulated airflow distribution diagram of a traditional standard FFU unit, such as Figure 22 , Figure 23 As shown, the airflow distribution is relatively uneven, with excessively high airflow speed in the central part and relatively low airflow speed on the left and right sides.

[0125] (B) The simulated airflow distribution diagram of the FFU unit of the present invention, as shown in the figure. Figure 24 , Figure 25 As shown, the airflow distribution is very stable and uniform.

[0126] (C) Simulated airflow distribution diagrams of the internal airflow channels for the two models above, as shown. Figure 26 As shown, the air inlet and internal airflow channels of the unit are almost identical without the use of a perforated plate-type flow equalizer.

[0127] (IV) Numerical simulation analysis and comparison:

[0128] The accuracy of the simulation results is the foundation for subsequent optimization and improvement. Therefore, it is necessary to first analyze the results of numerical simulation. In order to verify the effectiveness of numerical simulation, the simulation results were compared with the flow field analysis. The changes in airflow distribution and flow field at the internal airflow channel and air outlet were compared between the traditional standard FFU unit and the FFU unit of this invention.

[0129] To improve the technical performance of the FFU and achieve a more uniform airflow distribution, the installation positions of various perforated plate flow equalizers were optimized and adjusted in the physical model of the FFU. The effect of the optimization was then evaluated through numerical simulation results, and this process was repeated. After multiple simulation analyses, it was found that the airflow distribution was most stable and uniform when the distance from the airflow channel outlet was approximately 50 mm.

[0130] The following is a simplified description of the airflow channels for comparing the two types of units;

[0131] Distribution of narrow, winding airflow channels:

[0132] Depending on the centrifugal fan impeller and outlet configuration, when installed in an FFU (Fan Filter Unit), the extremely narrow and irregular S-shaped airflow channel generates significant unstable flow at abrupt expansion or contraction points, referred to here as turbulence, backflow, or vortices. Extensive and in-depth research has been conducted on these parameters, and it is generally accepted that the main factors contributing to airflow instability include: flow state (laminar, turbulent), initial velocity distribution, turbulent velocity of the free flow, abrupt contraction ratio, and abrupt expansion ratio, etc. Due to the sudden expansion or contraction of the airflow channel area, unstable flow phenomena such as backflow and vortices occur after the cross-section of the area change, leading to pressure reduction and a decrease in energy and other performance characteristics.

[0133] Install orifice plate flow equalizer distribution:

[0134] This invention focuses on improving the lack of S-shaped airflow channels in traditional standard FFU units by installing perforated plate flow equalizers. By utilizing the uniform diffusion principle of perforated plate flow equalizers, the airflow distribution becomes more stable, resulting in a more uniform distribution of airflow at the outlet of the entire FFU unit and a more stable airflow.

[0135] To compensate for this problem, the cross-sectional area of ​​the perforated plate flow equals that of the airflow channel. Under a constant flow rate, the flow velocities at the inlet of the perforated plate flow equalize with those at the outlet of the airflow channel. Through the diffusion and rectification functions of the perforated plate flow equalizer, the airflow is gradually diffused and rectified.

[0136] By adding a perforated plate flow equalizer, the airflow pressure at various points becomes more balanced and stable, and there will be no significant pressure gradient changes. Turbulence, eddies, and backflow can be greatly reduced, and the airflow becomes very smooth. Effectively reducing the airflow channel resistance will reduce turbulence, backflow, and eddies.

[0137] (V) Analysis of airflow simulation results:

[0138] CFD numerical simulation can effectively simulate and observe the internal flow field of an FFU unit, revealing the causes and specific locations of turbulence, eddies, and backflow within the FFU. Through the above simulation analysis and comparison, it is evident that the airflow inside a standard FFU unit is relatively unstable, generating significant turbulence, eddies, and backflow phenomena. Furthermore, the surface velocity at the high-efficiency filter outlet is uneven, with higher velocity in the center and lower velocity around the perimeter. In contrast, the FFU unit of this invention exhibits relatively stable airflow with uniform distribution, demonstrating significant improvement.

[0139] The main reason is the installation of a perforated plate air distributor. Utilizing the air distributor's functions of equalizing and stabilizing the airflow, it rapidly and stably diffuses the airflow, quickly achieving a uniform and stable distribution. This results in a more uniform exhaust airflow, significantly improving the purification effect of the cleanroom.

[0140] Numerical simulation was employed, and CFD software was used to analyze the internal flow field and airflow distribution at the outlet of both the standard FFU unit and the FFU unit of this invention. The simulation results were compared, and the internal flow field of the FFU unit was analyzed based on the principles of energy saving and uniform air supply. It was found that the addition of a perforated plate flow equalizer, along with numerical simulation results, significantly reduced unstable flow and improved airflow. This solved the problem that the velocity in the circular tangential direction at the outlet of the traditional guide channel was much higher than in other areas, achieving stable and uniform air supply. This confirms that the perforated plate flow equalizer can greatly improve the airflow distribution of the standard FFU unit.

[0141] (VI) Specific conclusions drawn from this simulation:

[0142] (1) The uniformity of airflow distribution is closely related to the cleanliness of the cleanroom. The more stable the airflow, the better the cleaning effect. The numerical simulation results above confirm that the FFU unit of the present invention with the addition of a perforated plate flow equalizer can indeed greatly improve the airflow distribution of the unit.

[0143] (2) Under the same baseline cleanliness requirements, if the system uses the same circulating air volume and the airflow is stable and uniformly distributed, the cleanliness can be relatively improved. Conversely, if the airflow is stable and uniform, the circulating air volume of the cleanroom can be relatively reduced, which can also reduce the kW of the fan and save energy.

[0144] (3) In addition, under the same air volume conditions, if the pressure loss increases, the kW of the blower motor will increase, which will relatively increase the energy consumption.

[0145] The numerical simulations above demonstrate that using an FFU unit equipped with a perforated plate flow equalizer can not only improve the cleanliness of the cleanroom but also save a significant amount of energy.

[0146] FFU (Fan Filter Unit) systems are primarily used in high-cleanliness environments covering entire areas. To meet diverse system requirements, a wide variety of FFU units with different specifications, sizes, and functions have emerged. The dimensions of the casing, especially its length and width, are interconnected with the size of the HEPA filter. The purpose is to ensure a certain airflow velocity to meet the cleanliness requirements of the cleanroom. The height of the casing is closely related to the internal structure of the unit and the height of the HEPA filter. Furthermore, the unit requires sufficient space and airflow ductwork to ensure stable and uniform airflow distribution. Therefore, careful selection is essential for the internal structure and the combination of the fan.

[0147] In addition, after installing the perforated plate flow equalizer, this invention can not only improve the uniform distribution of airflow in the airflow channel inside the FFU unit, but also reduce operating noise when the airflow distribution is stable.

Claims

1. A FFU unit air outlet uniform flow structure, comprising a machine body shell (1) and a fan (2), the fan is fixedly installed on the machine body shell, characterized in that: A perforated plate flow equalizer (3) is also provided. The perforated plate flow equalizer is fixedly installed on the air outlet of the fan. The perforated plate flow equalizer completely covers the air outlet of the fan. Several air outlet holes are formed on the perforated plate flow equalizer. The airflow discharged from the air outlet of the fan is discharged outward through each air outlet hole (4) on the perforated plate flow equalizer. The structure of the perforated plate flow equalizer fixedly installed on the air outlet of the fan is as follows: a connecting flange (5) is fixedly installed on the edge of the air outlet of the fan. The perforated plate flow equalizer is fixedly installed on the connecting flange through a connector. At least two connecting screws (6) are fixedly installed on the connecting flange. The specific structure is as follows: at least two connecting holes (10) are provided on the connecting flange. Two connecting nuts (11) are movably screwed onto each connecting screw. The connecting screws pass through the connecting holes of the connecting flange. The connecting flange is tightly clamped between two connecting nuts. The perforated plate flow equalizer has at least two mounting holes (7). The connecting screws can be inserted into the mounting holes on the perforated plate flow equalizer one by one. Each connecting screw has two mounting nuts (8) movably screwed on it. The perforated plate flow equalizer is tightly clamped between the two mounting nuts. There is a set gap between the mounting holes on the perforated plate flow equalizer and the outer circumferential surface of the connecting screw. The connecting screw can be moved or swing through the mounting holes. By forming a gap between the mounting holes and the connecting screw, the distance between different positions of the perforated plate flow equalizer and the flange end face can be changed by adjusting the position of the mounting nuts on each connecting screw. This can then adjust the angle between the perforated plate flow equalizer and the flange end face, thereby changing the air outlet direction and air outlet speed of the perforated plate flow equalizer.

2. The FFU unit air outlet flow uniformity structure according to claim 1, characterized in that: An elastic washer (9) is also provided, which is tightly clamped between the perforated plate flow equalizer and the mounting nut, and there is a set gap between the inner hole of the elastic washer and the connecting screw.

3. The FFU unit air outlet flow uniformity structure according to claim 2, characterized in that: The mounting hole and the inner hole of the elastic washer are any one of the following: an elongated elliptical hole, a large round hole with a diameter larger than that of the connecting screw, or a cross hole.

4. The FFU unit air outlet flow uniformity structure according to claim 1, characterized in that: The perforated plate flow equalizer is also provided with a positioning screw hole (18) on its side wall. A positioning screw (19) is movably screwed into the positioning screw hole. The tip of the positioning screw can be tightly pressed against the side wall of the connecting screw.

5. The FFU unit air outlet flow uniformity structure according to claim 1, characterized in that: There are four connecting screws, distributed at the four corners of the perforated plate flow equalizer.

6. The FFU unit air outlet uniform flow structure according to claim 1, characterized in that: The perforated plate flow equalizer is a perforated plate, and the edge of the perforated plate is bent to form a fixed frame (12) for connection with the air outlet of the fan.

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