A range hood

Abstract

The application discloses an oil fume extractor, which comprises a fan system and an air outlet cover arranged at an air outlet of the fan system, the fan system comprises a volute and an impeller arranged in the volute, the volute comprises a volute tongue, and the air outlet cover comprises an outlet, and the outlet throat area of the volute is smaller than the area of the outlet of the air outlet cover, wherein the outlet throat area of the volute is the cross-sectional area of the volute passing through the starting end of the volute tongue, and the cross section is parallel to the axis of the impeller. Compared with the prior art, the outlet throat area of the volute is small, the reverse airflow is less, and the noise reduction of the user working condition is facilitated.

Description

Technical Field

[0001] This invention relates to oil fume purification devices, and more particularly to range hoods. Background Technology

[0002] Multi-blade centrifugal fans are characterized by high pressure and low noise, making them a common power source for many systems. They utilize a high-speed rotating impeller within a volute to perform both work and filtration. For example, they are frequently used in range hoods. A multi-blade centrifugal fan installed inside the hood draws in and exhausts cooking fumes. The fan consists of a volute, an impeller housed within the volute, and a motor that drives the impeller. As the impeller rotates, a negative pressure suction is generated at the center of the fan, drawing the cooking fumes from below into the fan. After being accelerated by the fan, the volute collects the fumes and guides them outdoors.

[0003] With technological advancements and intensified industry competition, consumers are increasingly demanding higher noise levels. The national standard defines the noise level of a range hood as the noise within a semi-anechoic chamber when the hood is venting without resistance. Consumers often use this as a noise reference when purchasing products. However, range hoods are used in homes. In high-rise buildings, when fumes are exhausted, they pass through exhaust pipes and shared flues. Due to the kitchen structure and the nature of high-rise buildings, there is significant resistance at the rear of the exhaust pipe. Therefore, the operating conditions differ from those of a semi-anechoic chamber, resulting in different noise levels.

[0004] As a key component of the fan system, the volute's function is to guide the gas leaving the impeller to its outlet and convert some of the dynamic pressure into static pressure. Static pressure is closely related to the exhaust air under high resistance. The flow within the volute is highly complex; while gas flows along it, gas continuously enters from the impeller. Therefore, the design of the volute profile directly affects not only the flow losses within the volute but also the aerodynamics of the impeller upstream. When designing the volute, it is necessary to comprehensively consider the noise requirements under both operating conditions to reduce noise levels in both scenarios.

[0005] Existing textbooks design volute profiles based on the following assumptions: ① the airflow is steady within the volute; ② the viscosity of the gas is ignored; ③ the gas flows uniformly out along the entire impeller outlet, i.e., the flow rate across different cross-sections of the volute is considered. The angle formed between this section and the initial section of the volute. Proportional to the design of the equiangular logarithmic spiral curve using the equal circulation method and the eccentric four-point method for designing the volute profile, which is similar to the curve.

[0006] Currently, most volute designs follow this design method to design their profiles. However, due to the influence of the air inlet and volute outlet, the internal flow field of an actual volute is not uniform, especially under high-resistance conditions where the internal flow becomes more turbulent. Based on this principle, patents have been published specifically addressing this issue with volute profile designs. For example, Chinese invention patent application number 201721352626.4, "Centrifugal Fan Volute Structure," uses a combination of logarithmic spiral curves, straight segments, Archimedes' lines, and circular arc segments to make the internal flow of the fan more closely resemble actual gas flow, thereby reducing noise. Another example is Chinese invention patent application number 201821369078.0, "A Centrifugal Fan with a Volute," which uses a combination of equal-angle logarithmic spiral curves, Bezier curves, and variable-angle logarithmic spiral curves to further increase the smoothness of the fluid inside the volute.

[0007] The above patented technologies are designed specifically for gas flow under unobstructed laboratory conditions. There is limited research on high-resistance operating conditions in the usage environment. Due to the high resistance in the usage environment, the air intake and internal flow of the fan are very different. The design methods of the above patents may achieve lower noise in the usage environment. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a range hood that can reduce noise during use, in order to address the shortcomings of the prior art.

[0009] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a range hood, including a fan system and an air outlet mask disposed at the air outlet of the fan system, the fan system including a volute and an impeller disposed within the volute, the volute including a volute tongue, and the air outlet mask including an outlet, characterized in that: the area of ​​the outlet throat of the volute is smaller than the area of ​​the outlet of the air outlet mask, and the area of ​​the outlet throat of the volute is the cross-sectional area of ​​the volute passing through the starting end of the volute tongue, the cross-section being parallel to the axis of the impeller.

[0010] Preferably, in order to make the air outlet speed of the volute throat fast and the reverse airflow less, which is beneficial to noise reduction in the user's working conditions, the ratio of the outlet throat area of ​​the volute to the outlet area of ​​the air outlet mask is 0.6 to 0.95.

[0011] Preferably, to ensure a positive amplification of the volute expansion, the volute profile includes a line segment corresponding to the volute tongue and an expanding spiral curve starting from the end of the line segment.

[0012] Preferably, the volute-shaped line further includes a first straight segment and a second straight segment, the end point of the first straight segment is the start point of the line segment, the start point of the second straight segment is the end point of the spiral curve, and the part between the start point of the first straight segment and the end point of the second straight segment corresponds to the air outlet.

[0013] When the fan system is placed vertically, a coordinate system is formed by taking the horizontal line passing through the common center of the volute and the impeller as the X-axis and the vertical line passing through the center as the Y-axis. Both the X-axis and the Y-axis are perpendicular to the axis of the impeller. The part between the starting point of the first straight line segment and the ending point of the second straight line segment is located in the second quadrant of the coordinate system.

[0014] The line segment is an arc with center L. The starting point of the first straight line segment and the ending point of the second straight line segment form a first connecting line. A straight line parallel to the first connecting line is drawn through point L, intersecting the second straight line segment at point m and the first straight line segment at point n. The distance |mn| between points m and n is defined as the width of the volute's outlet throat. The connecting line between points m and n lies within the aforementioned cross-section. The area of ​​the volute's outlet throat = the width of the outlet throat × the thickness of the volute's inner cavity. The thickness of the volute's inner cavity is the dimension of the volute along the axis of the impeller.

[0015] Preferably, in combination with the air intake characteristics of the fan system, the airflow turbulence in each area is reduced and the noise of the user's operating conditions is reduced. When the fan system is placed vertically, a coordinate system is formed with the horizontal straight line passing through the common center of the volute and the impeller as the X-axis and the vertical straight line passing through the center as the Y-axis. The X-axis and Y-axis are both perpendicular to the axis of the impeller. The part between the starting point of the first straight line segment and the ending point of the second straight line segment is located in the second quadrant of the coordinate system.

[0016] The spiral curve includes a first curve starting from the end of the line segment, a second curve starting from the end of the first curve, a third curve starting from the end of the second curve, a fourth curve starting from the end of the third curve, and a fifth curve starting from the end of the fourth curve. The expansion angles of the first, second, and third curves increase sequentially, while the expansion angles of the third, fourth, and fifth curves decrease sequentially.

[0017] Preferably, to prevent gas separation upon entering the volute through the volute tongue, which could cause airflow turbulence and reduce noise, the expansion angle of the first curve is α1, the line connecting the starting point and the center of the first curve is the second connecting line, and the angle between the line connecting each point on the first curve to the center and the second connecting line is α1. And it satisfies 0°≤α1≤2°;

[0018] Preferably, to avoid amplifying noise by creating a flared airflow, the expansion angle of the fifth curve is α2, the line connecting the starting point and the center of the first curve is the second line, and the angle between the line connecting each point on the fifth curve to the center and the second line is α2. And it satisfies 0°≤α5≤2°,

[0019] Preferably, considering the air intake characteristics of the fan system, to reduce airflow turbulence in each area and lower noise levels during user operation, the line connecting the starting point and center of the first curve is the second line, and the angle between the line connecting each point on the first curve to the center and the second line is [value missing]. The angle between the line connecting each point on the second curve to the center and the second connecting line is . The angle between the line connecting each point on the third curve to the center and the second line is... The angle between the lines connecting each point on the fourth curve to the center and the second connecting line is... The angle between the lines connecting each point on the fifth curve to the center and the second connecting line is... And satisfy

[0020] Preferably, in order to reduce the air outlet resistance and facilitate the increase of flow rate under laboratory conditions, the angle between the second straight line segment and the X-axis is the air outlet angle β of the volute, and satisfies 70°≤β≤90°.

[0021] Preferably, in order to control the small air outlet area in the volute flow channel, reduce reverse airflow, and facilitate noise reduction in user operating conditions, the line connecting the starting point and center of the first curve is the second line, the angle between the second line and the Y-axis is γ, and satisfies 10°≤γ≤50°.

[0022] Preferably, in order to reduce the impact and disturbance on the volute tongue when the impeller speed is too high under user operating conditions and reduce noise, the outer diameter of the impeller is D, the shortest distance between the outer edge of the impeller and the starting point of the first curve is the volute tongue clearance t, and satisfies t / D = 0.11~0.18.

[0023] Preferably, in order to prevent the reverse airflow at the air outlet from impacting the impeller and causing it to be squeezed out in the opposite direction, thereby reducing noise, the profile of the volute tongue is an arc with a radius of r, and the outer diameter of the impeller is D, satisfying 2r / D = 0.1 to 0.25.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] 1. This results in a smaller outlet throat area in the volute, faster airflow, and less reverse airflow, which is beneficial for noise reduction in user operating conditions.

[0026] 2. The logarithmic spiral curve design with variable expansion angle takes into account the flow characteristics of two working conditions, reduces flow turbulence under high resistance conditions, and reduces noise in the operating environment;

[0027] 3. A larger outlet angle reduces outlet resistance, which is beneficial for increasing airflow under laboratory conditions;

[0028] 4. The design incorporates a larger radial tongue clearance to reduce the impact and disturbance on the worm tongue when the impeller speed is too high under user operating conditions, thereby reducing noise. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the volute and air outlet shroud according to an embodiment of the present invention;

[0030] Figure 2 for Figure 1 A sectional view;

[0031] Figure 3 This is a schematic diagram of the profile of the volute casing according to an embodiment of the present invention;

[0032] Figure 4 This is a flow field simulation diagram of the fan system according to an embodiment of the present invention. Detailed Implementation

[0033] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Since the embodiments disclosed in this invention can be arranged in different directions, these terms indicating direction are only for illustration and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity. In addition, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0035] See Figure 1 and Figure 3 A fan system includes a volute 1 and may further include an impeller 3 disposed within the volute 1. Figure 3 (shown in the image) and a motor (not shown) for driving the impeller 3 to rotate. When used in a range hood, an exhaust mask 2 can also be installed at the air outlet of the fan system. The fan system can also be used in other applications requiring such a power unit.

[0036] The volute (or volute 1) is a core component of the range hood's power unit, and it plays a crucial role in the range hood's performance and noise levels. Range hoods are categorized into laboratory operating conditions and user operating conditions based on their exhaust resistance. In user operating conditions, the range hood exhausts fumes outdoors through the exhaust pipe, check valve, and shared flue. During exhaust, the fumes encounter significant resistance, which can easily lead to reverse secondary flow into the fan system, causing airflow turbulence and increased noise.

[0037] As mentioned above, due to greater external resistance, the internal flow field is more turbulent and noise is higher during user operation. With increasing consumer demands, higher requirements are being placed on noise levels during operation. Currently, most volute profile design methods are effective in reducing noise under laboratory conditions, but they pay less attention to user operating conditions, resulting in high noise levels during user operation. This invention, combining the structural characteristics of the volute 1, takes user operating conditions as the primary reference point and optimizes the design based on the air intake characteristics of the fan system. This allows the fan system to maintain low noise levels under laboratory conditions while also reducing noise during user operation. Testing shows that using the volute 1 of this invention and the fan system using it can reduce noise by at least 1.5 dB.

[0038] The volute 1 includes a front cover plate 11, a rear cover plate 12, and an annular wall 13 disposed between the front cover plate 11 and the rear cover plate 12. The edge projection of the front cover plate 11 is the profile spline of the volute 1. The rear cover plate 12 has the same profile as the front cover plate 11. The lower side of the front cover plate 11 adopts an inward chamfer design (optional, as it is required for placement within the overall housing). The volute 1 also includes a volute tongue 14 and an air outlet 15. The two circumferential ends of the annular wall 13 near the air outlet 15 respectively form a first air guide plate 131 and a second air guide plate 132, wherein the first air guide plate 131 is located between the volute tongue 14 and the air outlet 15. The structure of the volute 1 described above is the same as that of the prior art.

[0039] This invention primarily reduces noise in both laboratory and ambient environments by optimizing the volute profile. By studying the different effects of volute 1 parameters on flow rate and noise under two operating conditions, and ensuring a certain volute 1 width, the invention guarantees low noise levels in the laboratory operating conditions (a reduction of 5 dB), while simultaneously reducing ambient noise by 2 dB. Through a rational profile design, the flow field at the fan system inlet and inside the volute 1 is improved, reducing turbulence and thus lowering noise levels under both operating conditions.

[0040] Based on the structural characteristics of fan systems, especially those used in side-suction range hoods, and the air intake characteristics of fan systems in laboratory and user operating conditions, the air intake zones of fan systems are divided into Zone 1 (Q1) to Zone 4 (Q4). See [reference needed]. Figure 3 The area enclosed by an ellipse.

[0041] Among them, region 1 Q1: starts from cochlear tongue 14 ( Figure 3 The area shown is a section following the clockwise direction. The main function of this area is to guide the gas diverted by the volute tongue 14 back into the volute housing 1 (entering the volute housing 1 means entering from the impeller 3) to perform work. When the airflow is diverted by the volute tongue 14, a portion of the airflow enters the volute housing 1. This airflow is characterized by its high speed and adherence to the wall surface. Due to the overall air intake characteristics and the influence of the volute tongue 14, the amount of gas entering the volute housing 1 via the impeller 3 in area Q1 is relatively small. When a large expansion angle is set in the corresponding part of the volute profile in this area, the gas entering the volute housing 1 through the volute tongue 14 is easily separated, causing airflow turbulence. If the expansion angle is too large, it forms a funnel shape with the volute tongue 14, and the noise at the volute tongue 14 (which is relatively high for a fan system) is easily amplified through this funnel shape, causing increased sound. When the expansion angle in this section is greater than 4°, the sound becomes significantly louder.

[0042] Region 2 Q2: The volute flow channel at this location serves both rectification and diffusion functions. Under high-resistance conditions, there will be reverse flow at the outlet 15 of the volute 1, which will be forced out from the inner edge of the impeller 3 through the outer edge of the impeller 3. The direction of this reverse flow is mainly from the upper part of Region 4 Q4 and Region 1 Q1 to Region 2 Q2. When the volute flow channel in Region 2 Q2 is too narrow, it will weaken the suction capacity of this region or make it easy for the reverse airflow in Region 2 Q2 to be forced out and collide with the reverse flow in Region 1 Q1, causing airflow turbulence and increased noise.

[0043] Region 3 (Q3): This region has a large diffusion degree in the volute flow channel. The volute flow channel at this location can effectively convert some of the kinetic energy of the airflow into pressure energy, providing sufficient pressure for the outlet airflow to ensure its normal outflow. Therefore, the curve in this region adopts a larger expansion angle design. On the one hand, this increases the pressure energy of the fan system; on the other hand, the rapid increase in the opening degree of this flow channel can continue to the volute flow channel corresponding to Region 4, ensuring the size of the volute opening A and guaranteeing the width requirements of the impeller 3's main working area.

[0044] Region 4 Q4: This region is an important working area for impeller 3, so a certain volute opening A is required at this location. However, since this region is close to the air outlet 15 of the fan system, it is a relatively noisy area. When the expansion angle of this region is large, it is equivalent to the air outlet of a horn, so the noise will be amplified through this region. Therefore, a design scheme with a smaller air outlet angle is adopted for this region.

[0045] Based on the division of the above four regions and their respective characteristics, the volute profile is divided into five segments. By designing five different expansion angles, controlling the radial tongue clearance t, the outlet angle β, and the outlet area at the throat of the volute, the volute profile is made more compatible with the flow characteristics of the two operating conditions, thereby reducing noise. Specifically, this is achieved through the following structure.

[0046] See Figure 3 The volute profile of this invention includes line segment na corresponding to the volute tongue 14, and sequentially connected curves ab, bc, cd, de, and ef. Line segment na is tangent to the first curve ab at point a, where a is the starting point of the first curve ab, b is the ending point of the first curve ab, b is the starting point of the second curve bc, and so on. c, d, and e are the ending points of the second curve bc, the third curve cd, and the fourth curve de, and simultaneously the starting points of the third curve cd, the fourth curve de, and the fifth curve ef. f is the ending point of the fifth curve ef. Each curve adopts an expanding spiral curve to ensure a positive amplification of the volute 1's expansion. In this embodiment, line segment na is an arc shape.

[0047] The volute profile also includes a first straight segment hn and a second straight segment fg, where h is the starting point of the first straight segment hn, and hn is tangent to line segment na at n. The second straight segment fg is the ending point of the second straight segment fg, and fg is tangent to the fifth curve ef at f. The first straight segment hn corresponds to the first air guide plate 131 on the annular wall 13 of the volute 1, and the second straight segment fg corresponds to the second air guide plate 132 on the annular wall 13 of the volute 1. The portion between the first connecting line gh corresponds to the air outlet 15 of the volute 1, so that the air guide plates corresponding to the two straight segments can guide the airflow out of the air outlet 15.

[0048] In this definition, taking the vertical placement of the fan system as an example, the horizontal line passing through the common center O of the volute 1 and impeller 3 is the X-axis (horizontal axis), and the vertical line passing through the center O of the volute 1 is the Y-axis (vertical axis). Both the X-axis and Y-axis are perpendicular to the axis of the impeller 3. The line segment corresponding to the air outlet 15 of the volute 1 is located in the second quadrant of the XY coordinate system (the quadrant definition of the coordinate system is the same as in the prior art), and the oil fume airflow is discharged vertically upward from the air outlet 15. The starting radius of the first curve ab is R0 (i.e., the distance between the starting point a of the first curve ab and the center O of the volute 1, and the length of the second connecting line aO), the starting radius of the second curve bc is Rb, the starting radius of the third curve cd is Rc, the starting radius of the fourth curve de is Rd, the starting radius of the fifth curve ef is Re, and the ending radius of the fifth curve ef is Rf. The outer diameter of the impeller 3 is D, and the shortest distance between the outer edge of the impeller 3 and the starting point a of the first curve ab is the radial tongue clearance t. The angle between the second line aO and the vertical axis Y is γ, which is the starting position angle. The first quadrant starts at 0° vertically (the intersection of the Y-axis and the volute type 1 line), with clockwise as positive. For any radius of curvature R on each curve, the angle between the line connecting each point to the center O within the corresponding curve segment and the second line aO is γ. (Different curves are distinguished by subscripts 1 to 5). The angle between the tangent at any point on each curve with radius of curvature R and the tangent at that point to the concentric circle (the circle passing through the center O of the volute 1) is the expansion angle (this definition is the same as in the prior art), denoted by α (different curves are distinguished by subscripts 1 to 5). The angle between the second straight line segment fg and the X-axis is the air outlet angle of the volute 1, denoted by β; L is the center of the arc-shaped volute tongue 14.

[0049] Draw a straight line parallel to gh through point L, intersecting the second line segment fg at point m and the first line segment hn at point n. The distance |mn| between points m and n is defined as the throat width of the volute 1. The throat is the cross-section of the volute 1 passing through the starting end of the volute tongue 14, and this cross-section is perpendicular to the axis of the impeller 3 (in...). Figure 3 In the diagram, the axis of impeller 3 is perpendicular to the paper surface, and mn is located within this cross-section. When the outlet throat area of ​​volute 1 (outlet throat area = volute outlet throat width × volute inner cavity thickness, where the inner cavity thickness is the dimension of volute 1 along the axis of impeller 3, and is approximately equal to the distance between the front cover plate 11 and the rear cover plate 12 of volute 1) is small, the air outlet velocity at that location is high, and the reverse airflow is low, which is beneficial for noise reduction in user operating conditions. Preferably, in this embodiment, the outlet throat area of ​​volute 1 is smaller than the outlet 21 area of ​​exhaust mask 2. Preferably, the ratio of volute outlet throat area to exhaust mask 2 outlet area is 0.6 to 0.95. Here, the outlet of exhaust mask 2 is defined as the circular outlet area at the connection to the smoke exhaust duct.

[0050] Draw a straight line perpendicular to mn through point n, intersecting the X-axis at point P. Define the amount of impeller 3 exposed relative to volute tongue 14 under the current volute profile as D-|OP|. The smaller this value, the more the volute tongue 14 blocks the impeller 3. Under user operating conditions, the reverse airflow is less likely to impact the impeller solid wall, which is beneficial for noise reduction. However, R-|OP|≥0 should be controlled to avoid excessive airflow impacting the volute tongue under laboratory operating conditions, which would increase laboratory noise.

[0051] The formula for the logarithmic curves of the above five curves is: Where R0 = D + t. The expansion angles of each curve follow a small-large-small pattern. Combined with... Figure 4Specifically, the expansion angle of the first curve ab is designed based on the air intake characteristics and noise patterns of region Q1. Since the first curve ab is connected to the volute tongue 14, which acts as a diverter and guide, when the airflow passes through the volute tongue 14, a portion of the airflow collides with the volute tongue 14 and enters the volute housing 1. This airflow is characterized by high speed and adherence to the wall surface. Due to the overall air intake characteristics and the influence of the volute tongue 14, the amount of gas entering the volute housing 1 in region Q1 is relatively small. When a larger expansion angle is set in this region, the gas entering the volute housing 1 through the volute tongue 14 is easily separated, causing airflow turbulence. Furthermore, it forms a funnel shape with the volute tongue 14, and the noise at the volute tongue 14 is easily amplified through this funnel, resulting in a louder sound. At the same time, a larger diameter tongue clearance t is required to reduce the impact of excessively high impeller speed on the volute tongue under user operating conditions and reduce noise. Therefore, preferably, 0°≤α1≤2°. In this embodiment, α1 is 1.8°. The angle is 45°; 20mm ≤ t ≤ 40mm.

[0052] The design of the second curve bc is based on the intake characteristics under high resistance conditions in region 2 Q2. Under high resistance conditions, there will be a reverse flow at the outlet 15 of the volute 1, which will be forced out from the inner diameter of the impeller 3 through the outer diameter of the impeller 3. The reverse flow direction is mainly from the upper part of region 4 Q4 and region 1 Q1 to region 2 Q2. When the volute flow channel in region 2 Q2 is too narrow, the internal pressure of the volute is also high, which will weaken the suction capacity of this region or make it easy for the reverse airflow in region 2 Q2 to be forced out and collide with the reverse flow in region 1 Q1, causing airflow turbulence and increased noise. Therefore, the volute flow channel in region 2 Q2 is enlarged by increasing the diameter tongue clearance t and increasing the expansion angle of the logarithmic curve to prevent the directional flow from the inner diameter of the impeller in region 2 Q2. Therefore, preferably, 4°≤α2≤6°. In this embodiment, α2 is 5.2°. It is 135°.

[0053] The third curve, cd, is located at the inward tangent angle of volute 1. When volute 1 is tangent inward, the channel volume decreases, easily causing airflow turbulence. Therefore, this curve adopts a large expansion angle design. On the one hand, this reduces the impact of the tangent angle on the channel volume; on the other hand, the increased opening of this flow channel can extend to the volute flow channel corresponding to the fourth region, thereby reducing noise under laboratory operating conditions. Therefore, preferably, 6°≤α3≤8°. In this embodiment, α3 is 6.2°. It is 55°.

[0054] The fourth curve 'de' and the fifth curve 'ef' correspond to the impeller inlet, which is region Q4. This region is the main air intake area of ​​the fan system. The width of the volute flow channel in this region is beneficial for increasing airflow and reducing noise. However, since this region is adjacent to the air outlet 15 of the volute 1, when the expansion angle in this region is large, it is equivalent to the air outlet of a funnel, so the noise will be amplified through this region. Therefore, a design scheme with a smaller volute outlet angle is adopted in this region. Therefore, preferably, the fourth curve 'de' is: 3°≤α4≤5°. In this embodiment, α4 is 3°. The angle is 30°, serving as a transition to avoid a large change in the expansion angle between the third curve cd and the fifth curve ef; for the fifth curve ef: 0°≤α5≤2°. In this embodiment, α5 is 1.5°. It is 50°.

[0055] In the outlet section of the volute profile, the volute opening A is denoted as the distance between the outer edge of impeller 3 and the intersection of the volute profile on the X-axis (at 270°). A should be controlled to ≤|mn| to ensure the airflow in the outlet section is in a deceleration and pressurization state, which is beneficial for overcoming user operating resistance and reducing noise. With a fixed |mn|, a smaller A value is more beneficial for noise reduction in user operating conditions, but an excessively small A value is detrimental to increasing the flow rate in the fan laboratory. In this embodiment, A is 111 mm, and |mn| is 125 mm.

[0056] The second air guide plate 132 has a certain guiding effect on the airflow direction from the volute 1. When the air outlet angle β is large (<90°), the airflow direction is more vertical and the air outlet resistance is smaller, which is conducive to the flow rate increase under laboratory conditions. The initial position angle γ controls the minimum air outlet area in the volute flow channel. When the γ angle is large, the flow channel area is small and there is less reverse airflow, which is conducive to noise reduction under user conditions. Therefore, the preferred values ​​are 70°≤β≤90°; 10°≤γ≤50°.

[0057] Preferably, in this embodiment, the radius r of the volute tongue 14 is in the range of 20mm to 40mm, or 2r / D = 0.1 to 0.25. When r is larger, the area where the airflow blown out by the impeller 3 impacts the volute tongue 14 is larger, and a larger static pressure will be formed in this area, which can prevent the reverse airflow at the air outlet 15 from impacting the impeller and being squeezed out in the opposite direction, thereby reducing noise.

[0058] The ratio t / D of the worm tongue clearance t to the outer diameter D of the impeller 3 is preferably 0.11 to 0.18. The purpose of designing this larger worm tongue clearance t is to reduce the impact and disturbance on the worm tongue when the impeller speed is too high under the user's operating conditions, and to reduce noise.

Claims

1. An extractor hood comprising a fan system and an outlet grille (2) arranged at an outlet opening (15) of the fan system, the fan system comprising a volute (1) and an impeller (3) arranged within the volute (1), the volute (1) comprising a volute tongue (14), the outlet grille (2) comprising an outlet opening (21), characterized in that: The outlet throat area of the volute (1) is smaller than the area of the outlet (21) of the air outlet cover (2), the outlet throat area of the volute (1) is the cross-sectional area of the volute (1) passing through the starting end of the volute tongue (14), and the cross-section is parallel to the axis of the impeller (3); The volute profile of the volute (1) comprises a line segment (na) corresponding to the volute tongue (14) and an expanding spiral curve starting from the end point of the line segment (na); When the fan system is vertically placed, a straight line horizontally passing through the center (O) common to the volute (1) and the impeller (3) is taken as the X-axis, and a straight line vertically passing through the center (O) is taken as the Y-axis, thereby forming a coordinate system, the X-axis and the Y-axis are both perpendicular to the axis of the impeller (3), and the part between the starting point of the first straight line segment (hn) and the end point of the second straight line segment (fg) is located in the second quadrant of the coordinate system; The spiral curve comprises a first curve (ab) starting from the end point of the line segment (na), a second curve (bc) starting from the end point of the first curve (ab), a third curve (cd) starting from the end point of the second curve (bc), a fourth curve (de) starting from the end point of the third curve (cd), and a fifth curve (ef) starting from the end point of the fourth curve (de), the expansion angles of the first curve (ab), the second curve (bc) and the third curve (cd) increase in turn, and the expansion angles of the third curve (cd), the fourth curve (de) and the fifth curve (ef) decrease in turn; The angle between the connecting line between the starting point of the first curve (ab) and the center (O) and the second connecting line (aO) is φ1, the angle between the connecting line between each point on the second curve (bc) and the center (O) and the second connecting line (aO) is φ2, the angle between the connecting line between each point on the third curve (cd) and the center (O) and the second connecting line (aO) is φ3, the angle between the connecting line between each point on the fourth curve (de) and the center (O) and the second connecting line (aO) is φ4, the angle between the connecting line between each point on the fifth curve (ef) and the center (O) and the second connecting line (aO) is φ5, and 30°≤φ1≤50°, 90°≤φ2≤150°, 40°≤φ3≤70°, 20°≤φ4≤40°, 30°≤φ5≤60°.

2. The hood according to claim 1, characterized in that: The outlet throat area of the volute (1) / the area of the outlet (21) of the air outlet cover (2) = 0.6-0.

95.

3. The hood according to claim 1 or 2, characterized in that: The volute profile further comprises a first straight line segment (hn) and a second straight line segment (fg), the end point of the first straight line segment (hn) is the starting point of the line segment (na), the starting point of the second straight line segment (fg) is the end point of the spiral curve, and the part between the starting point of the first straight line segment (hn) and the end point of the second straight line segment (fg) corresponds to the air outlet (15). When the fan system is vertically placed, a straight line passing through the common center (O) of the volute (1) and the impeller (3) is taken as the X axis, and a vertical line passing through the center (O) is taken as the Y axis, thereby forming a coordinate system, the X axis and the Y axis are both perpendicular to the axis of the impeller (3), and the part between the starting point of the first straight line segment (hn) and the ending point of the second straight line segment (fg) is located in the second quadrant of the coordinate system; The line segment (na) is a circular arc, the center of the circular arc is L, the first straight line segment (hn) and the second straight line segment (fg) form a first connecting line (gh), a straight line parallel to the first connecting line (gh) passes through the point L and intersects the second straight line segment (fg) at the point m and intersects the first straight line segment (hn) at the point n, the distance |mn| between the point m and the point n is defined as the outlet throat width of the volute (1), the connecting line between the point m and the point n is located in the above-mentioned cross section, the outlet throat area of the volute (1) = outlet throat width × volute inner cavity thickness, and the volute inner cavity thickness is the dimension of the volute (1) in the axial direction of the impeller (3).

4. The hood according to claim 1 or 2, characterized in that: The expansion angle of the first curve (ab) is α1, the connecting line between the starting point of the first curve (ab) and the center (O) is a second connecting line (aO), the angle between the connecting line between each point on the first curve (ab) and the center (O) and the second connecting line (aO) is φ1, and 0°≤α1≤2° and 30°≤φ1≤50° are satisfied.

5. The hood according to claim 1 or 2, characterized in that: The expansion angle of the fifth curve (ef) is α2, the connecting line between the starting point of the first curve (ab) and the center (O) is a second connecting line (aO), the angle between the connecting line between each point on the fifth curve (ef) and the center (O) and the second connecting line (aO) is φ5, and 0°≤α5≤2° and 30°≤φ5≤60° are satisfied.

6. The hood according to claim 3, characterized in that: The angle between the second straight line segment (fg) and the X axis is the outlet angle β of the volute (1), and 70°≤β≤90° is satisfied.

7. The hood according to claim 1 or 2, characterized in that: The connecting line between the starting point of the first curve (ab) and the center (O) is a second connecting line (aO), the angle between the second connecting line (aO) and the Y axis is γ, and 10°≤γ≤50° is satisfied.

8. The hood according to claim 1 or 2, characterized in that: The outer diameter of the impeller (3) is D, the shortest distance between the outer edge of the impeller (3) and the starting point of the first curve (ab) is the radial tongue gap t, and t / D = 0.11-0.18 is satisfied.

9. The hood according to claim 1, characterized in that: The profile of the volute tongue (14) is a circular arc with a radius r, the outer diameter of the impeller (3) is D, and 2r / D = 0.1-0.25 is satisfied.

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