Low noise large air volume centrifugal fan volute

Abstract

A low-noise, high-volume centrifugal fan casing includes an annular wall with a center point O. An XY plane rectangular coordinate system is established with the center point O as the origin, where the X-axis is horizontal and the Y-axis is vertical. The annular wall is formed by a continuously unfolding annular wall profile around the center point O. The annular wall profile is formed by connecting multiple feature points located at different positions through a fitted curve. The fitted curve is selected from at least one of spline curves, piecewise cubic Bezier curves, and combinations of circular and straight segments. The beneficial effects of this invention are: by setting multiple feature points in the XY coordinate system and using spline curves, piecewise cubic Bezier curves, or combinations of circular and straight segments for fitting and connection, the configuration of the annular wall profile is transformed from an "empirical spiral law" to a "measurable parameterized boundary." This reduces performance fluctuations caused by differences in empirical parameters.

Description

Technical Field

[0001] This invention relates to the field of range hood technology, specifically to a low-noise, high-volume centrifugal fan casing. Background Technology

[0002] As a primary household appliance for controlling kitchen fumes, the core function of a range hood is to promptly draw in and expel the oily fumes generated during cooking, or to purify them before expelling them outdoors. To achieve the intake, collection, and exhaust of these fumes, range hoods typically use a centrifugal fan as their power component. A centrifugal fan generally consists of an impeller and a volute: the high-speed rotation of the impeller gives the gas kinetic energy and generates centrifugal force; the volute collects and guides the high-speed airflow ejected from the outer periphery of the impeller, converting some of the airflow's kinetic energy into static pressure, ultimately allowing the gas to be smoothly discharged through the exhaust duct, check valve, and smoke extraction pipe.

[0003] In centrifugal fans, the structural morphology of the volute significantly affects airflow, static pressure efficiency, and noise level. Specifically, the volute's annular wall profile (also known as the volute outer wall profile or annular wall contour) directly determines the geometry of the flow channel between the impeller's outer circumference and the annular wall, as well as the diffusion process, influencing the circumferential velocity distribution, pressure recovery capability, and local flow separation. Particularly in the volute tongue region and the upstream region of the outlet channel, variations in the curvature, clearance, and connection method of the profile affect the intensity of the interaction between the unsteady flow at the impeller outlet and the volute tongue, thus impacting aerodynamic noise characteristics such as pressure pulsation, broadband noise, and discrete whistling noise.

[0004] In existing technologies, the design of the volute annular wall profile often adopts a logarithmic spiral proportional expansion law or an empirical profile based on principles such as equal area / equal velocity. A typical approach is to use the impeller outer circle as a reference, determining the radial dimension of the annular wall as a function of the circumferential angle according to a fixed proportional relationship or a predetermined spiral expansion law, and setting transition fillets or arcs near the volute tongue to avoid sharp corners. This type of design method usually takes the "maximum airflow condition" or a high airflow condition close to the maximum speed as the main design objective, determining the profile dimensions through empirical parameters, proportional coefficients, or formula derivation, thereby maximizing the maximum airflow and static pressure output within the constraints of the rated shape.

[0005] However, as range hood products develop towards lower noise and higher comfort, using maximum airflow as the design basis alone is no longer sufficient to meet actual usage needs, so it is necessary to make further improvements. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and, in view of the deficiencies of existing technologies, to provide a low-noise, high-volume centrifugal fan casing that has a large air volume, low noise, and strong static pressure recovery capability.

[0007] To achieve the above objectives, the present invention provides a low-noise, high-volume centrifugal fan casing. The casing includes an annular wall with a center point O. An XY plane rectangular coordinate system is established with the center point O as the origin, wherein the X-axis is set along the horizontal direction and the Y-axis is set along the vertical direction. The annular wall is formed by an annular wall profile continuously unfolding around the center point O. The annular wall profile is formed by connecting multiple feature points located in different directions through a fitting curve. The fitting curve is selected from at least one of spline curves, piecewise cubic Bezier curves, and a combination curve of circular arc segments and straight line segments, and adjacent curve segments satisfy tangential continuity at the connection point. The feature points include at least the main feature points located in the positive X-axis, negative X-axis, positive Y-axis, and negative Y-axis directions, as well as the transition feature points located between adjacent main feature points, and the total number of the transition feature points is not less than two. Based on the outer radius R of the fitted impeller, the radial distance from each of the aforementioned feature points to the center point O is greater than R, and increases sequentially along the impeller rotation direction; The radial distances between the feature points satisfy the following range relationship: The minimum radial distance is 1.05 to 1.30 times R; The maximum radial distance is 1.30 to 1.80 times the minimum radial distance; The radial increment Δri between adjacent feature points accounts for 5% to 40% of the total radial increment Δr, where Δri is the difference in radial distance between two adjacent feature points, and Δr is the difference between the maximum radial distance and the minimum radial distance. The annular wall profile has an arc or rounded corner transition section in the volute tongue region to make the annular wall profile continuous and smooth in the volute tongue region.

[0008] Furthermore: the minimum radial distance is 1.10 to 1.25 times R; The maximum radial distance is 1.40 to 1.65 times the minimum radial distance; The radial increment Δri between adjacent feature points accounts for 10% to 35% of the total radial increment Δr.

[0009] Furthermore: the annular wall profile passes through at least the following feature points: feature point A located on the positive half-axis of the Y-axis, feature point B located in the first quadrant, feature point C located on the positive half-axis of the X-axis, feature point D located in the fourth quadrant, feature point E located on the negative half-axis of the Y-axis, feature point F located in the third quadrant, and feature point G located on the negative half-axis of the X-axis; The radial distances from each feature point to the center point O are as follows: OC = 152 ± 3 mm; OD = 185 ± 3 mm; OE = 200 ± 5 mm; OF = 227 ± 5 mm; OG=237±5mm; Furthermore, the feature point G is the feature point with the largest radial distance from the center point O in the annular wall profile.

[0010] Furthermore: near the feature point A, the annular wall profile is provided with a volute transition arc, and the volute transition arc is continuously and smoothly connected to the adjacent main body segment; The radius RB of the transition arc of the volute tongue is 8±2mm; The main body segment 3 includes a control arc with center point O as the center, and the radius RA of the control arc is 132.5±5mm.

[0011] Furthermore: along the impeller rotation direction, the lines connecting the corresponding feature points and the center point O satisfy the following angular relationship, and all of these angles are interior angles less than 180°: At point I, the angle A between the straight line HI and the tangent of the volute transition arc at point I is 77°±3°. ∠BOD is 120°±3°; ∠DOF is 85.7°±5°; ∠GOB is 128°±3°.

[0012] Furthermore: An upper control point H and an intermediate control point I are set in the upstream area of ​​the air outlet duct, wherein point H is located on the positive side of the Y-axis and on the negative side of the X-axis, and point I is located on the positive side of the Y-axis; in: The perpendicular distance between point H and the X-axis is 175±3mm; The horizontal distance between point H and the Y-axis is 207±3mm; The horizontal distance between point H and point I is 168±3mm; The horizontal distance between point I and the Y-axis is 38±2mm; Point H and point I define the upper boundary straight line segment HI of the upstream area of ​​the air outlet channel, and the straight line segment HI is connected and tangent to the volute tongue transition arc at point I. Point H and point I are used to define the outer contour shape of the upstream area of ​​the air outlet channel.

[0013] Furthermore, the fitted curve is a spline curve, and the annular wall profile is a curve obtained by spline interpolation or spline fitting through the multiple feature points.

[0014] Furthermore: the fitted curve is a piecewise cubic Bezier curve, and the annular wall profile is formed by connecting at least two cubic Bezier curve segments end to end, and adjacent Bezier curve segments satisfy tangential continuity at the connection point.

[0015] Furthermore: the fitted curve is a combination curve of a circular arc segment and a straight line segment, and the annular wall profile includes at least a circular arc segment and a straight line segment, wherein the circular arc segment and the straight line segment are tangent at the connection point.

[0016] The beneficial effects of this invention are: 1. This application sets multiple feature points in the XY coordinate system and uses spline curves, piecewise cubic Bezier curves, or combinations of circular arc segments and straight line segments for fitting and connection. Simultaneously, it requires adjacent curve segments to satisfy tangential continuity at the connection point, thereby transforming the configuration of the annular wall profile from an "empirical spiral law" to a "measurable parameterized boundary." This reduces performance fluctuations caused by differences in empirical parameters.

[0017] 2. This application stipulates that the radial distance between each feature point is greater than the outer radius R of the impeller, and increases sequentially along the impeller rotation direction. Furthermore, it specifies that the minimum radial distance is 1.05 to 1.30 times R, and the maximum radial distance is 1.30 to 1.80 times the minimum radial distance. It also limits the proportion of the radial increment of adjacent feature points to the total radial increment to 5% to 40%. These constraints allow the "expansion rhythm" of the annular wall flow channel in the circumferential direction to be controlled in segments, avoiding excessively strong or weak diffusion in local areas of traditional proportional / logarithmic spiral profiles. This reduces the probability of boundary layer separation, backflow, and vortex generation caused by unfavorable pressure gradients, thereby improving flow stability under common operating conditions.

[0018] 3. This application sets a volute tongue transition arc in the volute tongue region and limits its radius RB, while requiring the annular wall profile to be continuous and smooth in the volute tongue region. The continuous profile and gentle curvature change at the volute tongue are beneficial to reducing the impact / stripping effect between the impeller exit wake and the volute tongue structure, reducing the amplitude of local strong vortices and pressure pulsations, thereby suppressing discrete noise, broadband noise, and aerodynamic whistling under specific operating conditions.

[0019] 4. A control arc centered at point O is introduced into the main body section, with its radius RA (significantly larger than RB) constrained. This controls the expansion trend of the main body section and prevents local blockage or pressure loss caused by excessive inward or outward expansion of the profile. By combining RB for smooth transition of the volute tongue and RA for controlling the expansion trend of the main body, the stability of the static pressure recovery process can be improved while ensuring maximum airflow discharge capacity.

[0020] 6. By limiting the central angle relationships of ∠BOD, ∠DOF, ∠GOB, the development relationship of the annular wall profile in different quadrants is more controllable. Combined with the radial increment ratio constraint, a more reasonable flow channel geometry change can be formed in the entire circumferential range, reducing local geometric abrupt changes and flow mismatch, thereby improving efficiency and reducing noise under common operating conditions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the volute ring wall structure in this invention.

[0022] Figure 2 This is a schematic diagram of various points on the profile line of the volute ring wall in this invention. Detailed Implementation

[0023] The objective of this invention is achieved in the following manner: a low-noise, high-volume centrifugal fan casing, the casing comprising an annular wall having a center point O, an XY plane rectangular coordinate system established with the center point O as the origin, wherein the X-axis is set along the horizontal direction and the Y-axis is set along the vertical direction, the annular wall is formed by an annular wall profile continuously unfolding around the center point O, the annular wall profile being formed by connecting multiple feature points located in different directions through a fitting curve, the fitting curve being selected from at least one of spline curves, piecewise cubic Bezier curves, and a combination curve of circular arc segments and straight line segments, and adjacent curve segments satisfy tangential continuity at the connection point; The feature points include at least the main feature points located in the positive X-axis, negative X-axis, positive Y-axis, and negative Y-axis directions, as well as the transition feature points located between adjacent main feature points, and the total number of the transition feature points is not less than two. Based on the outer radius R of the fitted impeller, the radial distance from each of the aforementioned feature points to the center point O is greater than R, and increases sequentially along the impeller rotation direction; The radial distances between the feature points satisfy the following range relationship: —The minimum radial distance is 1.05 to 1.30 times R; —The maximum radial distance is 1.30 to 1.80 times the minimum radial distance; —The radial increment Δri between adjacent feature points accounts for 5% to 40% of the total radial increment Δr, where Δri is the difference in radial distance between two adjacent feature points, and Δr is the difference between the maximum radial distance and the minimum radial distance; The annular wall profile has an arc or rounded corner transition section in the volute tongue region to make the annular wall profile continuous and smooth in the volute tongue region.

[0024] In this embodiment, the impeller draws in gas from the center and throws it outwards. The gas at the impeller outlet exhibits both circumferential and radial velocity components. The volute annular wall acts as a gradually expanding circumferential converging and diffuser channel: on the one hand, it "catches" the high-speed airflow from the impeller outlet and guides it to converge along the volute towards the outlet; on the other hand, it converts some kinetic energy into static pressure during the diffuser process.

[0025] In this application, the geometric boundary of the annular wall profile is defined by multiple feature points, and then connected by a combination of splines / Bezier curves / circular arcs and straight lines, requiring tangential continuity at the connection points. Essentially, this geometrically eliminates abrupt changes in the profile and tangent direction. This reduces boundary layer separation, backflow, and boundary layer thickening caused by local geometrical abrupt changes, thereby reducing turbulence enhancement and pressure pulsation.

[0026] The design incorporates radial distances greater than R, increasing sequentially along the rotation direction to ensure a basic gap exists between the impeller's outer circumference and the annular wall, which gradually expands circumferentially. This gradual increase in circumferential area accommodates the continuously converging flow along the circumference, preventing blockages and secondary flows caused by localized "too narrow" areas, while also avoiding sudden localized expansion that could lead to separation.

[0027] The design of the minimum / maximum radial distance range plus the overall proportion of Δri / Δr, compared to traditional proportional or logarithmic spirals which often only have a single pattern and make it difficult to specifically control the local expansion rhythm, not only limits the overall range of the minimum and maximum radial distances in this application, but also further limits the radial increment ratio of adjacent feature points in each segment to 5%–40%, which is equivalent to discretizing the circumferential expansion process into several "expansion steps" and giving boundaries to each step: Insufficient step size: Insufficient diffusion, inadequate static pressure recovery; Excessive step size: It is detrimental to the steep increase of pressure gradient, easy separation and backflow, and increased noise; By controlling the extremes of "too small / too large" by adjusting the proportion range, the expansion becomes more controllable and better matches the flow stability under air volume + back pressure in common operating conditions.

[0028] Among them, the volute tongue region is the area where the interference between the impeller outlet wake and the fixed structure is strongest. Setting a rounded arc / rounded corner and ensuring continuous smoothness can reduce the impact and stripping of the high-speed jet at this point, reduce the pressure fluctuation amplitude, and reduce discrete noise and howling trigger conditions from the source.

[0029] Therefore, by using "quantifiable feature points + achievable curve types + tangential continuity," the profile becomes measurable, reproducible, and manufactureably consistent. By using "overall range + local incremental ratio," the expansion rhythm is controlled to balance maximum airflow with stability under common operating conditions, which helps reduce separation / recirculation / eddies, thereby reducing noise and maintaining airflow output.

[0030] In one embodiment: the minimum radial distance is 1.10 to 1.25 times R; The maximum radial distance is 1.40 to 1.65 times the minimum radial distance; The radial increment Δri between adjacent feature points accounts for 10% to 35% of the total radial increment Δr.

[0031] In this embodiment: a slightly larger minimum radial distance of 1.10 to 1.25R is generally more conducive to reducing strong shear and local interference between the impeller outer circumference and the ring wall; the preferred multiple and incremental ratio of the maximum radial distance make the expansion more inclined to a balanced state of "both expanding pressure and not over-expanding pressure".

[0032] Under common back pressure conditions, the preferred range is more likely to achieve more stable diffusion and lower separation risk, thus achieving a better compromise between "static pressure recovery / noise / air volume".

[0033] In one embodiment: the annular wall profile passes through at least the following feature points: feature point A located on the positive half-axis of the Y-axis, feature point B located in the first quadrant, feature point C located on the positive half-axis of the X-axis, feature point D located in the fourth quadrant, feature point E located on the negative half-axis of the Y-axis, feature point F located in the third quadrant, and feature point G located on the negative half-axis of the X-axis. The radial distances from each feature point to the center point O are as follows: OC = 152 ± 3 mm; OD = 185 ± 3 mm; OE = 200 ± 5 mm; OF = 227 ± 5 mm; OG=237±5mm; Furthermore, the feature point G is the feature point with the largest radial distance from the center point O in the annular wall profile.

[0034] In this embodiment, by specifying clear radial boundary points in different circumferential directions, it is equivalent to defining the minimum / intermediate / maximum expansion degree of the volute flow channel in multiple key directions. Designating G as the maximum radial distance point essentially fixes the maximum expansion position at a certain circumferential direction, which is beneficial for controlling the peak location of the collected flow rate, thereby affecting the flow distribution and pressure field distribution before the outlet. Multi-point constraints can reduce the risk of "local mismatch caused by relying on a single rule," making the expansion process more consistent with the non-uniform characteristics of the actual flow field.

[0035] In one embodiment: near the feature point A, the annular wall profile is provided with a volute transition arc 2, and the volute transition arc 2 is continuously and smoothly connected to the adjacent main body segment 3; The radius RB of the volute tongue transition arc 2 is 8±2mm; The main body segment 3 includes a control arc 4 with center point O as the center, and the radius RA of the control arc 4 is 132.5±5mm.

[0036] In this embodiment: the volute tongue is the position where the impeller exit wake periodically sweeps. If the profile is too sharp or the curvature changes abruptly, it will lead to strong local separation, enhanced vortex shedding, and intensified pressure pulsation. Setting a transition arc with radius RB and smoothly connecting it to the main body section is equivalent to geometrically "mitigating the interaction between the impeller exit jet and the fixed boundary," reducing impact and stripping.

[0037] By controlling the arc with O as the center, it is equivalent to providing an "overall trend boundary" for the main body segment, preventing abnormal inward / outward concavity in certain directions during the outward expansion of the main body segment. It plays the role of "steady-state shape constraint" during diffusion and convergence, which helps to maintain the continuity and predictability of the flow channel cross-section changes.

[0038] RA primarily focuses on stabilizing the expansion trend and restoring static pressure. The combination of these two approaches helps achieve a balance between noise suppression and airflow / static pressure.

[0039] In one embodiment: along the impeller rotation direction, the lines connecting the corresponding feature points and the center point O satisfy the following angular relationship, and all of the angles are interior angles less than 180°: At point I, the angle A between the straight line HI and the tangent of the volute transition arc 2 at point I is 77°±3°. ∠BOD is 120°±3°; ∠DOF is 85.7°±5°; ∠GOB is 128°±3°.

[0040] These central angles essentially define the relative expansion positions of key feature points in the circumferential direction, equivalent to specifying the "distribution length" of different expansion stages in the circumferential direction. When combined with radial increment ratio constraints, this can solidify the "which circumferential ranges expand faster / slower," thereby matching the circumferential non-uniformity of the impeller outlet flow field and reducing separation and secondary flow caused by local expansion mismatch.

[0041] Among them, the straight line segment HI at the upper boundary of the upstream air outlet channel determines the guiding trend of the airflow before it enters the air outlet; the tangent of the volute transition arc at point I represents the "instantaneous guiding direction" of the airflow by the wall at that point. The included angle A limits the range of the included angle between the two, which is equivalent to controlling the turning intensity of the guidance at that point: Both excessively small and excessively large angles can lead to an enhancement of the local velocity gradient and the unfavorable pressure gradient; A proper angle can make the streamlines turn more smoothly, reduce local vortices and separation, thereby reducing noise and improving static pressure recovery.

[0042] In one embodiment: an upper control point H and an intermediate control point I are set in the upstream area of ​​the air outlet duct, wherein point H is located on the positive side of the Y-axis and on the negative side of the X-axis, and point I is located on the positive side of the Y-axis; in: The perpendicular distance between point H and the X-axis is 175±3mm; The horizontal distance between point H and the Y-axis is 207±3mm; The horizontal distance between point H and point I is 168±3mm; The horizontal distance between point I and the Y-axis is 38±2mm; Point H and point I define the upper boundary straight line segment HI of the upstream area of ​​the air outlet channel, and the straight line segment HI is connected and tangent to the volute tongue transition arc 2 at point I. Point H and point I are used to define the outer contour shape of the upstream area of ​​the air outlet channel.

[0043] In this embodiment: the position and direction of the upper boundary straight line segment HI are fixed by the coordinate distance relationship between H and I, so that the diffusion morphology of this region has a clear geometric boundary; and it is stipulated that HI and the transition arc of the volute tongue are tangent at point I to ensure the direction of the geometric connection is continuous, thereby avoiding the occurrence of "geometric bend" in front of the air outlet and causing local detached vortices.

[0044] Therefore, effectively constraining the morphology of key areas through a small number of point parameters is beneficial for obtaining more stable static pressure recovery under back pressure conditions, while reducing separation and pressure pulsation in the area before the air outlet and near the volute in noise-sensitive areas.

[0045] In one embodiment, the fitted curve is a spline curve, and the annular wall profile is a curve obtained by spline interpolation or spline fitting through the multiple feature points. Spline curves are commonly used in engineering for fitting complex contours. Their core advantage is that they can obtain a smooth curve overall under multi-point constraints and easily satisfy continuity of a certain order, such as tangential continuity or even curvature continuity.

[0046] For volutes, spline fitting helps to form a continuously varying flow channel boundary, making streamlines turn and expand more smoothly and reducing local turbulence enhancement.

[0047] In one embodiment: the fitted curve is a piecewise cubic Bezier curve, the annular wall profile is formed by connecting at least two cubic Bezier curve segments end to end, and adjacent Bezier curve segments satisfy tangential continuity at the connection point.

[0048] Among them, the cubic Bezier curve segment adjusts the curve shape through control points, while the segmented Bezier curve can make more controllable adjustments to the local shape; tangential continuity ensures that the direction does not change abruptly at the connection point.

[0049] In localized sensitive areas of the volute, such as near the volute tongue or upstream of the air outlet, segmented Bezier technology facilitates precise control of local curvature and expansion rhythm, thereby suppressing unfavorable local pressure gradients and separation. It combines "local adjustability" with "smooth connectivity," enabling refined optimization of noise hotspots while maintaining overall contour continuity.

[0050] In one embodiment, the fitted curve is a combination of an arc segment and a straight line segment, and the annular wall profile includes at least one arc segment and one straight line segment, with the arc segment and the straight line segment being tangent at the connection point. The combination of arc and straight line facilitates manufacturing. The "tangency" ensures the continuity of the tangent direction at the connection point, avoiding sharp angles. The arc segment can be used to achieve stable steering and mitigate curvature changes; the straight line segment can be used to achieve controllable expansion or guidance. The combination of the two can control the guidance and expansion of critical areas while ensuring processing feasibility. It is more conducive to batch manufacturing consistency and quality inspection. The arc radius and straight line length / angle are easy to measure, and good flow smoothness is maintained, balancing cost and performance stability.

[0051] In summary, the working principle of this case is as follows: When a centrifugal fan is working, the impeller rotates, drawing in and accelerating the gas. The airflow at the impeller outlet has high kinetic energy and exhibits a non-uniform circumferential distribution, resulting in a wake and pressure pulsations. The volute's function is to gradually gather this high-speed airflow circumferentially to the outlet, while simultaneously converting kinetic energy into static pressure during diffusion to overcome system back pressure and output a stable airflow.

[0052] This scheme establishes a coordinate system with the center point O, discretizes the ring wall profile into multiple feature points, and connects them through spline / segmented Bezier / circular arc-straight line combination curve fitting, requiring tangential continuity between adjacent curve segments.

[0053] The combination of "feature points + fitted curves" enables the precise construction of the ring wall boundary; "Tangential continuity" avoids abrupt changes in boundary direction and reduces geometrically induced separation; The principle that "radial distances at all points are greater than R and increase along the direction of rotation" ensures that the cross-section of the flow channel gradually increases with the flow rate, thus avoiding blockage. The "minimum / maximum radial distance range" ensures that the gap and overall expansion are within a reasonable range; The “Δri / Δr total proportion range” segments the expansion process to prevent excessive or slow local expansion, thereby reducing backflow, separation and eddies under airflow + back pressure in common operating conditions, reducing broadband noise and maintaining static pressure recovery capability.

[0054] Application 3 further uses AG points and key radial dimensions to solidify the expansion channel in multiple circumferential orientations, making the design reproducible, manufacturable and with higher performance consistency.

[0055] The volute tongue region is the most sensitive area for unsteady interference. The proposed solution uses a rounded / rounded transition at the volute tongue and defines the local geometry through RB and continuous smooth connections to reduce the impact and stripping of sharp boundaries by high-speed jets, reduce vortex shedding and pressure pulsation amplitude, thereby suppressing discrete noise peaks and the risk of howling.

[0056] Meanwhile, the main body segment is equipped with a control arc RA centered at O, which provides a stable constraint on the overall expansion trend and avoids increased local losses caused by abnormal deformation of the main body segment.

[0057] Furthermore, with back pressure present in the exhaust duct, diffusion and reversal in the upstream area of ​​the air outlet channel are more likely to induce separation. The solution clarifies the position and direction of the straight line segment HI at the upper boundary of this area by controlling the distance relationship between points H and I, and stipulates that HI and the transition arc of the volute tongue connect and are tangent at point I to avoid geometric bends.

[0058] Based on this, the angle between HI and the tangent of the arc is further defined by the included angle A, so that the transition intensity of "upstream guide - volute tongue transition" can be quantitatively controlled, reducing the probability of the formation of local unfavorable pressure gradient and detached vortex, thereby improving static pressure recovery and reducing noise.

[0059] Among them, when using spline curves, the overall smoothness is strong, making it suitable for global continuous optimization; When using segmented Bezier, there is strong local adjustability, which is suitable for fine-tuning the sensitive areas of the volute / air outlet. When using a combination of circular arcs and straight lines, manufacturing and inspection are friendly, and stable guidance and controllable diffusion can be achieved while maintaining tangential continuity.

[0060] All three implementation methods, under the overall framework of "feature point constraint + tangential continuity at the connection + radial range / increment ratio + volute tongue transition + upstream control", can achieve controllable expansion and smooth guidance of the flow channel geometry. This reduces separation and eddies and pressure pulsation under normal operating conditions, and maintains sufficient flow collection and output capacity under maximum air volume conditions, achieving a synergy between low noise and high air volume.

[0061] In summary, this implementation method, through a structural system of "multi-feature point parameterization, optional curve fitting, tangential continuity, expansion rhythm constraint, and geometric quantitative control of the volute tongue and upstream guide," makes the volute flow channel smoother and more stable during circumferential convergence and diffusion. This reduces backflow and eddies and suppresses noise under normal operating conditions, while maintaining a high airflow output capacity under maximum airflow conditions, thus achieving synergistic optimization of low noise and high airflow.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A low-noise, high-volume centrifugal fan casing, the casing comprising an annular wall (1), the annular wall having a center point O, an XY plane rectangular coordinate system established with the center point O as the origin, wherein the X-axis is set along the horizontal direction and the Y-axis is set along the vertical direction, characterized in that: The annular wall is formed by an annular wall profile that is continuously extended around the center point O. The annular wall profile is formed by connecting multiple feature points located in different directions through a fitting curve. The fitting curve is selected from at least one of spline curves, piecewise cubic Bezier curves, and combined curves of circular arc segments and straight line segments, and adjacent curve segments satisfy tangential continuity at the connection point. The feature points include at least the main feature points located in the positive X-axis, negative X-axis, positive Y-axis, and negative Y-axis directions, as well as the transition feature points located between adjacent main feature points, and the total number of the transition feature points is not less than two. Based on the outer radius R of the fitted impeller, the radial distance from each of the aforementioned feature points to the center point O is greater than R, and increases sequentially along the impeller rotation direction; The radial distances between the feature points satisfy the following range relationship: The minimum radial distance is 1.05 to 1.30 times R; The maximum radial distance is 1.30 to 1.80 times the minimum radial distance; The radial increment Δri between adjacent feature points accounts for 5% to 40% of the total radial increment Δr, where Δri is the difference in radial distance between two adjacent feature points, and Δr is the difference between the maximum radial distance and the minimum radial distance. The annular wall profile has an arc or rounded corner transition section in the volute tongue region to make the annular wall profile continuous and smooth in the volute tongue region.

2. The volute casing of a low-noise, high-volume centrifugal fan according to claim 1, characterized in that: The minimum radial distance is 1.10 to 1.25 times R; The maximum radial distance is 1.40 to 1.65 times the minimum radial distance; The radial increment Δri between adjacent feature points accounts for 10% to 35% of the total radial increment Δr.

3. The volute casing of a low-noise, high-volume centrifugal fan according to claim 1 or 2, characterized in that: The annular wall profile passes through at least the following feature points: feature point A on the positive half-axis of the Y-axis, feature point B in the first quadrant, feature point C on the positive half-axis of the X-axis, feature point D in the fourth quadrant, feature point E on the negative half-axis of the Y-axis, feature point F in the third quadrant, and feature point G on the negative half-axis of the X-axis. The radial distances from each feature point to the center point O are as follows: OC = 152 ± 3 mm; OD = 185 ± 3 mm; OE=200±5mm; OF = 227 ± 5 mm; OG=237±5mm; Furthermore, the feature point G is the feature point with the largest radial distance from the center point O in the annular wall profile.

4. The volute casing of a low-noise, high-volume centrifugal fan according to claim 3, characterized in that: Near the feature point A, the annular wall profile is provided with a volute transition arc (2), and the volute transition arc (2) is continuously and smoothly connected to the adjacent main body segment (3); The radius RB of the volute tongue transition arc (2) is 8±2mm; The main body segment (3) includes a control arc (4) with center point O as the center, and the radius RA of the control arc (4) is 132.5±5mm.

5. A low-noise, high-volume centrifugal fan casing according to any one of claims 4 and 6, characterized in that: Along the impeller rotation direction, the lines connecting the corresponding feature points to the center point O satisfy the following angular relationship, and all of these angles are interior angles less than 180°: At point I, the angle A between the straight line HI and the tangent of the volute transition arc (2) at point I is 77°±3°; ∠BOD is 120°±3°; ∠DOF is 85.7°±5°; ∠GOB is 128°±3°.

6. A low-noise, high-volume centrifugal fan casing according to any one of claims 1 or 2, characterized in that: An upper control point H and an intermediate control point I are set in the upstream area of ​​the air outlet duct, with point H located on the positive side of the Y-axis and on the negative side of the X-axis, and point I located on the positive side of the Y-axis. in: The perpendicular distance between point H and the X-axis is 175±3mm; The horizontal distance between point H and the Y-axis is 207±3mm; The horizontal distance between point H and point I is 168±3mm; The horizontal distance between point I and the Y-axis is 38±2mm; Among them, point H and point I define the upper boundary straight line segment HI of the upstream area of ​​the air outlet channel, and the straight line segment HI is connected and tangent to the volute tongue transition arc (2) at point I; Point H and point I are used to define the outer contour shape of the upstream area of ​​the air outlet channel.

7. The volute casing of a low-noise, high-volume centrifugal fan according to claim 1, characterized in that: The fitted curve is a spline curve, and the annular wall profile is a curve obtained by spline interpolation or spline fitting through the multiple feature points.

8. The volute casing of a low-noise, high-volume centrifugal fan according to claim 1, characterized in that: The fitted curve is a piecewise cubic Bezier curve, and the annular wall profile is formed by connecting at least two cubic Bezier curve segments end to end, and adjacent Bezier curve segments satisfy tangential continuity at the connection point.

9. The volute casing of a low-noise, high-volume centrifugal fan according to claim 1, characterized in that: The fitted curve is a combination of a circular arc segment and a straight line segment, and the annular wall profile includes at least a circular arc segment and a straight line segment, wherein the circular arc segment and the straight line segment are tangent at the connection point.

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