A design method for low-load backward-flowing fan impeller

Abstract

The present invention relates to the technical field of fans, and discloses a design method for a low-load backward-flowing fan impeller, wherein the low-load backward-flowing fan impeller comprises an impeller chassis, a blade connecting ring and blades; the impeller chassis and the blade connecting ring are coaxially spaced, and there is an impeller domain between the impeller chassis and the blade connecting ring; the blades are circumferentially distributed in the impeller domain along the rotating axis of the low-noise backward-flowing fan; the design method comprises the following steps: S1, determining the impeller meridian flow surface parameters; S2, designing the blade profile according to the meridian flow surface parameters; obtaining the angle parameters of each section in the blade profile design; drawing the corresponding profile according to the angle parameters of each section; S3, distributing the blade thickness according to the corresponding profile to form a plurality of blade sections; S4, stacking the blade sections of the plurality of blade sections; S5, performing blade array modulation on the stacked blades to obtain a low-load backward-flowing fan impeller. The present invention has the advantages of large air volume, low noise and high efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of fans, and in particular to a design method for a low-load backward-directed fan impeller. Background Art

[0002] At present, the ceiling air conditioner, also known as ceiling air conditioner or ceiling type, embedded air conditioner. Embedded installation, with four-sided air outlet design, strong and uniform wind force, is the main equipment for heat exchange and air supply of the indoor unit of the air conditioner, and often uses a backward centrifugal impeller as the working component. With the development of society, people's quality of life has improved, and they pay more attention to product performance and user experience. In addition to the performance of air volume, it also needs to be quiet and power-saving.

[0003] Most of the blades of the existing impellers of existing fans are single-arc straight blades, and the impeller diameter ratio and relative width of the fan with single-arc straight blades are large, resulting in uneven axial distribution of the airflow at the impeller inlet; because the blades of the single-arc straight blades are evenly distributed, when the single-arc straight blades are working, the entire single-arc straight blade will pass through the minimum gap between the impeller and the casing at the same moment, causing high-frequency vibration induced by pressure pulsation in the flow channel of the blades, resulting in a resonance peak caused by the superposition of noise components and frequency noise, so that the interference noise and load between the fan impeller and the volute tongue and volute are large. Summary of the invention

[0004] The invention provides a design method for a low-load backward-flowing fan impeller, aiming to solve the problems of noise and heavy load of existing fan impellers.

[0005] An embodiment of the present invention provides a design method for a low-load backward-flowing blower impeller, wherein the low-load backward-flowing blower impeller comprises an impeller chassis, a blade connecting ring and a plurality of blades; the impeller chassis and the blade connecting ring are coaxially spaced, and an impeller domain is provided between the impeller chassis and the blade connecting ring; the plurality of blades are circumferentially distributed in the impeller domain along the rotating axis of the low-noise backward-flowing blower;

[0006] The design method of the low-load backward-flowing blower impeller comprises the following steps:

[0007] S1. Determine the parameters of the impeller meridian flow surface;

[0008] S2. Designing a blade profile according to the meridian flow surface parameters, obtaining angle parameters of each section in the blade profile design, and drawing a corresponding profile according to the angle parameters of each section;

[0009] S3, distributing the blade thickness according to the corresponding profile lines to form a plurality of blade cross sections;

[0010] S4, performing blade cross-sectional stacking on a plurality of the blade cross-sections;

[0011] S5. Modulate the stacked blades into a blade array to obtain a low-load backward-moving fan impeller.

[0012] Preferably, the step S1 specifically includes the following steps:

[0013] Acquire the meridian flow channel parameters of the impeller fan; wherein the meridian flow channel parameters include the position information of the inlet, outlet, wheel cover, wheel disc and blade leading edge;

[0014] Determine a fan size parameter constraint relationship according to the meridian flow channel parameters, and obtain a meridian flow surface according to the fan size parameter constraint relationship;

[0015] Among them, three sections are divided into three sections at equal distances according to the inlet and the outlet, namely the first section, the second section and the third section; the specific definitions are as follows:

[0016] The inlet radius of the flow surface of the wheel cover is Rs;

[0017] The inlet radius of the flow surface of the first section is Rs1;

[0018] The inlet radius of the flow surface of the second section is Rs2;

[0019] The inlet radius of the flow surface of the third section is Rs3;

[0020] The inlet radius of the flow surface of the wheel is Rh;

[0021] The impeller radius is R2; and the following constraints exist:

[0022] Rs / R2=0.79;

[0023] Rs1 / R2=0.71;

[0024] Rs2 / R2=0.65;

[0025] Rs3 / R2=0.61;

[0026] Rh / R2=0.6;

[0027] B1 is the inlet height; B2 is the outlet height;

[0028] And the following constraints exist:

[0029] B2 / B1=0.74.

[0030] Preferably, in S2, the angle parameters of each cross section include an inlet angle, an outlet angle and a wrap angle;

[0031] The inlet angle is the angle between the tangent of the starting point of the profile and the tangent of the axis circle at the starting point of the profile; the outlet angle is the angle between the tangent of the end point of the profile and the tangent of the axis circle at the end point of the profile; the wrap angle is the angle formed by the axis circle and the starting point and the end point of the profile;

[0032] Wherein, the inlet angle is β1, the outlet angle is β2, and the wrap angle is w;

[0033] 31°>β1-1>β1-2>β1-3>β1-4>β1-5>10°, β1-1 corresponds to the inlet angle of the wheel cover, β1-2 corresponds to the inlet angle of the first section, β1-3 corresponds to the inlet angle of the second section, β1-4 corresponds to the inlet angle of the third section, and β1-5 corresponds to the inlet angle of the wheel disc;

[0034] 70°> w - 1> w -2> w -3> w -4> w -5>40°, w -1 corresponds to the wrap angle of the wheel cover, w -2 corresponds to the wrap angle of the first section, w -3 corresponds to the wrap angle of the second section, w -4 corresponds to the wrap angle of the third section, w -5 corresponds to the wrap angle of the wheel.

[0035] Preferably, the inlet angle is β1±5°, the outlet angle is β2±5°, and the wrap angle is w ±5°.

[0036] Preferably, in S2, drawing corresponding profiles according to angle parameters of each cross section specifically comprises the following steps:

[0037] Determine the starting point and end point on each radial surface according to the angle parameters of each cross section;

[0038] The starting point and the end point are transformed into a grid diagram through conformal transformation, l’ = f (D2-D h ); h = f (51°); where D2 is the outer diameter of the blade, D h is the inner diameter of the blade, l’ is the difference between the outer diameter of the blade and the inner diameter of the blade, h is the height of the blade, f is the conformal transformation function;

[0039] in, l’、hThe length can be selected as desired, and ensure l’、h The relative length increment is equal to the radial and circumferential increments;

[0040] The relative relationship between the starting point and the end point is:

[0041] The radial increment is R2-Rh; the circumferential angle increment is 51°;

[0042] The radial increment R2-Rh is transformed into a longitudinal increment m, and the circumferential angle increment 51° is transformed into a lateral increment n; wherein m and n are both positive integers;

[0043] That is: vertical axis unit length: R2-Rh / m; horizontal axis unit length 51° / n;

[0044] In a rectangular coordinate system, a ray AP1 is drawn, which forms an angle of 13° with the horizontal direction passing through the starting point, and intersects the horizontal direction passing through the end point at a first intersection point P1;

[0045] In a rectangular coordinate system, a ray BP2 forms an angle of 31° with a horizontal direction passing through the end point, and intersects with a horizontal direction passing through the starting point at a second intersection point P2;

[0046] The starting point and the end point are connected by a 4-control-point Bezier curve, and the head and the tail are fixed at the starting point and the end point respectively, wherein the control point close to the starting point moves on the ray AP1 to be the first moving point P1', and the control point close to the end point moves on the ray BP2 to be the second moving point P2'; by performing conformal transformation and constrained movement, the contour line on each flow surface is obtained.

[0047] Preferably, the step S3 specifically includes the following steps:

[0048] The thickness of the blade adopts an airfoil distribution; its thickness parameters include the current point position l , Chord Length lmax 、Height of the current point of the pressure surface Yp and the current point height of the back pressure surface Yss , establishing a profile table according to the thickness parameters;

[0049] According to the profile table, 16 points are made and circles are made at the corresponding points;

[0050] Connect the centers of all circles to form a first curve, connect the tangents of all circles to form a second curve, draw multiple normal lines between the first curve and the second curve, and obtain the pressure surface height distribution;

[0051] The two ends of the plurality of normal lines are connected by using a Bezier curve to obtain a pressure surface profile line, and the pressure surface profile line is rotated to obtain a plurality of blade cross sections.

[0052] Preferably, the step S4 specifically includes the following steps:

[0053] The distance relationship between the leading edge point and the center of the curve leading edge vertex of the flow surface of the wheel cover, the first section, the second section, the third section and the flow surface of the wheel disk is controlled, and the offset positions of different blade sections are controlled and stacked.

[0054] Preferably, the step S5 specifically includes the following steps:

[0055] For the impeller with Z blades, sinusoidal adjustment is adopted, and the functional relationship is:

[0056] θ'=θi+A*SIN(N*θi);

[0057] Wherein, Z represents the number of blades; θ' represents the sinusoidal modulation angle; θi represents the equally spaced distribution angle, and θi=360 / Z; A represents the modulation angle amplitude; and N represents the modulation frequency.

[0058] Preferably, the range of A is 0.1θi - 0.3θi.

[0059] Preferably, N=1.

[0060] Compared with the prior art, the beneficial effect of the present invention lies in that, by determining the parameters of the impeller meridian flow surface; designing the blade profile according to the meridian flow surface parameters; obtaining the angle parameters of each section in the blade profile design; drawing the corresponding profile according to the angle parameters of each section; distributing the blade thickness according to the corresponding profile to form multiple blade sections; stacking the blade sections of multiple blade sections; and modulating the stacked blades into a blade array to obtain a low-load backward-leaving fan impeller. In this way, based on the impeller fan design software and fluid simulation, the blade load is controlled by methods such as variable circulation, increasing and decreasing load, etc., to achieve the effect of reducing noise and improving efficiency. The pressure surface is used as the working surface, and controlling the blade pressure can improve the airflow and work efficiency. The uniform pressure part reduces the mixing between the flow surfaces of the main airflow and reduces the secondary flow loss. The pressure gradient changes, and the pressure pulsation is reduced, which makes the noise lower. The present invention has been verified through multiple simulation iterations and multi-dimensional experimental tests, and has extensive advantages in noise and aerodynamic efficiency under different experimental conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The present invention will be described in detail below in conjunction with the accompanying drawings. The above and other aspects of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings. In the accompanying drawings:

[0062] Figure 1 is a flow chart of a design method for a low-load backward-flowing blower impeller provided by an embodiment of the present invention;

[0063] Figure 2is a schematic structural diagram of a low-load backward-flowing blower impeller provided by an embodiment of the present invention;

[0064] Figure 3 is a schematic diagram of a meridional flow channel of a fan provided by an embodiment of the present invention;

[0065] Figure 4 It is a schematic diagram of the cross-section division of the meridional flow channel of a fan provided by an embodiment of the present invention;

[0066] Figure 5 is a schematic diagram of blade inlet and outlet angle parameters provided by an embodiment of the present invention;

[0067] Figure 6 It is a schematic diagram of the inlet and outlet angle parameters of the wheel disc cross section provided by an embodiment of the present invention;

[0068] Figure 7 is a schematic diagram of a roulette flow surface provided by an embodiment of the present invention;

[0069] Figure 8 is a schematic diagram of the conformal transformation of the start point and the end point provided by an embodiment of the present invention;

[0070] Fig. 9 is a schematic diagram of constrained movement of a starting point and an end point provided by an embodiment of the present invention;

[0071] Fig.10 Schematic diagram of various flow surface lines provided by embodiments of the present invention;

[0072] Fig.11 is a schematic diagram of the blade profile angle variation law provided by an embodiment of the present invention;

[0073] Fig.12 is a schematic diagram of the change of blade thickness provided by an embodiment of the present invention;

[0074] Fig.13 is a schematic diagram of the pressure surface height distribution provided by an embodiment of the present invention;

[0075] Fig.14 is a schematic diagram of a pressure surface profile provided by an embodiment of the present invention;

[0076] Fig.15 is a schematic diagram of a blade cross section provided by an embodiment of the present invention;

[0077] Fig.16 is a schematic diagram of blade offset provided by an embodiment of the present invention;

[0078] Fig.17 is a schematic diagram of the sinusoidal modulation distribution of the blade provided by an embodiment of the present invention;

[0079] Fig.18aThis is a test effect diagram of air volume-noise of the box 1 provided by an embodiment of the present invention;

[0080] Fig.18b This is a test effect diagram of air volume-power of the box 1 provided in an embodiment of the present invention;

[0081] Fig.19a This is a test effect diagram of the air volume-noise of the box 2 provided by an embodiment of the present invention;

[0082] Fig.19b This is a test effect diagram of air volume-power of box 2 provided by an embodiment of the present invention;

[0083] Fig.20a This is a test effect diagram of the air volume-noise of the box 3 provided in an embodiment of the present invention;

[0084] Fig.20b It is a test effect diagram of the air volume-power of the box 3 provided in an embodiment of the present invention.

[0085] In the figure, 1, impeller chassis, 2, blade connecting ring, 3, blade, 4, inlet, 5, outlet, 6, wheel cover, 7, wheel disc, 8, blade leading edge, 9, rotating shaft. DETAILED DESCRIPTION

[0086] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0087] Combined with Figure 1-20b As shown, an embodiment of the present invention provides a design method for a low-load backward-flowing blower impeller, wherein the low-load backward-flowing blower impeller comprises an impeller chassis 1, a blade connecting ring 2 and a plurality of blades 3; the impeller chassis 1 and the blade connecting ring 2 are coaxially spaced, and an impeller domain is provided between the impeller chassis 1 and the blade connecting ring 2; the plurality of blades 3 are circumferentially distributed in the impeller domain along a rotating axis 9 of the low-noise backward-flowing blower;

[0088] The design method of the low-load backward-flowing blower impeller comprises the following steps:

[0089] S1. Determine the parameters of the impeller meridian flow surface;

[0090] S2. Designing a blade profile according to the meridian flow surface parameters, obtaining angle parameters of each section in the blade profile design, and drawing a corresponding profile according to the angle parameters of each section;

[0091] S3, distributing the blade thickness according to the corresponding profile lines to form a plurality of blade cross sections;

[0092] S4, performing blade cross-sectional stacking on a plurality of the blade cross-sections;

[0093] S5. Modulate the stacked blades into a blade array to obtain a low-load backward-moving fan impeller.

[0094] Specifically, by determining the parameters of the impeller meridian flow surface; designing the blade profile according to the meridian flow surface parameters; obtaining the angle parameters of each section in the blade profile design; drawing the corresponding profile according to the angle parameters of each section; distributing the blade thickness according to the corresponding profile to form multiple blade sections; stacking the blade sections of multiple blade sections; modulating the stacked blades into a blade array to obtain a low-load backward-leaving fan impeller. In this way, based on the impeller fan design software and fluid simulation, the blade load is controlled by methods such as variable circulation, increasing and decreasing loads, etc., to achieve the effect of reducing noise and improving efficiency. The pressure surface is used as the working surface, and controlling the blade pressure can improve the airflow and work efficiency. The uniform pressure part reduces the mixing between the flow surfaces of the main airflow and reduces the secondary flow loss. The pressure gradient changes, and the pressure pulsation is reduced, which makes the noise lower. The present invention has been verified through multiple simulation iterations and multi-dimensional experimental tests. Compared with high-level competitors of the same size in the industry, it has extensive advantages in noise and aerodynamic efficiency under different experimental conditions.

[0095] In this embodiment, the S1 specifically includes the following steps:

[0096] The meridian flow channel parameters of the impeller fan are obtained; wherein the meridian flow channel parameters include the position information of the inlet 4, the outlet 5, the wheel cover 6, the wheel disc 7 and the blade leading edge 8. Figure 3 As shown, the inlet 4 is Inlet, the outlet 5 is Outlet, the wheel cover 6 is Shroud, the wheel disc 7 is Hub, and the blade leading edge 8 is Leading edge. Optionally, the outlet 5 is set to be consistent with the blade trailing edge, which is not described here.

[0097] Determine a fan size parameter constraint relationship according to the meridian flow channel parameters, and obtain a meridian flow surface according to the fan size parameter constraint relationship;

[0098] Among them, see Figure 4 , three sections are equally spaced according to the inlet 4 and the outlet 5, namely the first section, the second section and the third section; the first section is defined as span1, the second section is defined as span2 and the third section is defined as span3; the specific definitions are as follows:

[0099] The inlet radius of the flow surface of the wheel cover is Rs;

[0100] The inlet radius of the flow surface of the first section is Rs1;

[0101] The inlet radius of the flow surface of the second section is Rs2;

[0102] The inlet radius of the flow surface of the third section is Rs3;

[0103] The inlet radius of the flow surface of the wheel is Rh;

[0104] The impeller radius is R2; and the following constraints exist:

[0105] Rs / R2=0.79;

[0106] Rs1 / R2=0.71;

[0107] Rs2 / R2=0.65;

[0108] Rs3 / R2=0.61;

[0109] Rh / R2=0.6;

[0110] B1 is the height of the inlet 4; B2 is the height of the outlet 5;

[0111] And the following constraints exist:

[0112] B2 / B1=0.74.

[0113] In this embodiment, in S2, the angle parameters of each cross section include an inlet angle, an outlet angle, and a wrap angle;

[0114] Definition: The inlet angle is the angle between the tangent of the starting point A of the profile and the tangent of the axis circle at the starting point A of the profile; the outlet angle is the angle between the tangent of the end point B of the profile and the tangent of the axis circle at the end point B of the profile; the wrap angle is the angle formed by the axis circle, the starting point A of the profile and the end point B of the profile; wherein the wrap angle is ∠A0B.

[0115] Among them, the inlet angle is β1, the outlet angle is β2, and the wrap angle is w, where w is represented by wrap angel. The remaining cross sections are designed according to the same principle as shown in Table 1 below;

[0116] Table 1

[0117]

[0118] 31°>β1-1>β1-2>β1-3>β1-4>β1-5>10°, β1-1 corresponds to the inlet angle of the wheel cover 6, β1-2 corresponds to the inlet angle of the first section span1, β1-3 corresponds to the inlet angle of the second section span2, β1-4 corresponds to the inlet angle of the third section span3, and β1-5 corresponds to the inlet angle of the wheel disc 7;

[0119] 70°> w - 1> w -2>w -3> w -4> w -5>40°, w -1 corresponds to the wrap angle of wheel cover 6, w -2 corresponds to the wrap angle of the first section span1, w -3 corresponds to the wrap angle of the second cross section span2, w -4 corresponds to the wrap angle of the third section span3, w -5 corresponds to the wrap angle of wheel 7.

[0120] Preferably, the inlet angle of the above five flow surfaces is β1±5°, the outlet angle is β2±5°, and the wrap angle is w ±5°.

[0121] In this embodiment, in S2, drawing corresponding profile lines according to the angle parameters of each cross section specifically includes the following steps:

[0122] The starting point A and the end point B on each radial surface are determined according to the angle parameters of each section; the Hub flow surface Rh / R2=0.6, ∠AOB=51°, and the same applies to other flow surfaces.

[0123] The starting point A and the end point B are transformed into a grid diagram through conformal transformation, l’ = f (D2-D h ); h = f (51°); where D2 is the outer diameter of the blade, D h is the inner diameter of the blade, l’ is the difference between the outer diameter of the blade and the inner diameter of the blade, h is the height of the blade, f is a conformal transformation function. In this transformation, although the shape of the graph changes, the angle between the two corresponding curves remains unchanged.

[0124] in, l’、h The length can be selected as desired, and ensure l’、h The relative length increment is equal to the radial and circumferential increments;

[0125] Specifically, by defining the starting point A and the end point B of the profile, the two points are connected into a profile, which is the radial increment and the angular increment on the plane.

[0126] The relative relationship between the starting point A and the end point B is:

[0127] The radial increment is R2-Rh; the circumferential angle increment is 51°;

[0128] The radial increment R2-Rh is transformed into a longitudinal increment m, and the circumferential angle increment 51° is transformed into a lateral increment n; wherein m and n are both positive integers;

[0129] That is: the unit length of the vertical axis is R2-Rh / m; the unit length of the horizontal axis is 51° / n.

[0130] Preferably, m=500, n=720. Relatively speaking, it is easier to calculate the unit increment by selecting numbers that are relatively easy to divide. By converting the radial increment R2-Rh into a longitudinal increment of 500, the circumferential angle increment of 51° is converted into a lateral increment of 720;

[0131] That is: the unit length of the vertical axis is R2-Rh / 500; the unit length of the horizontal axis is 51° / 720.

[0132] Specifically, for example, the radial increment of the end point relative to the starting point is 120 mm, and the circumferential increment is 44°. The conformal transformation is performed so that 120 mm = 500 mm; and 44° = 720 mm, which are represented on the histogram.

[0133] Then, on the histogram, every 1mm on the horizontal axis (after transformation) = 120 / 500 = 0.24mm (before transformation); every 1mm on the vertical axis (after transformation) = 44 / 720 = 0.061° (before transformation); change the mapping value: the end point is relative to the starting point, the radial increment is 120mm, and the circumferential increment is 44°, and the angle-preserving transformation is performed so that 120mm = 1200mm; and 44° = 880mm, which is represented on the histogram. Then, on the histogram, every 1mm on the horizontal axis (after transformation) = 120 / 1200 = 0.1mm (before transformation), and every 1mm on the vertical axis (after transformation) = 44 / 880 = 0.05° (before transformation), so that the final results of the two methods are the same.

[0134] In the rectangular coordinate system, the ray AP1 forms an angle of 13° with the horizontal direction passing through the starting point A, and intersects with the horizontal direction passing through the end point B at a first intersection point P1.

[0135] In the rectangular coordinate system, the ray BP2 forms an angle of 31° with the horizontal direction passing through the end point B, and intersects with the horizontal direction passing through the starting point A at a second intersection point P2.

[0136] The starting point A and the end point B are connected by a 4-control point Bezier curve, and the head and the tail are fixed at the starting point A and the end point B respectively, wherein the control point close to the starting point A moves on the ray AP1 to be the first moving point P1', and the control point close to the end point B moves on the ray BP2 to be the second moving point P2'; by performing conformal transformation and constrained movement, the profile line on each flow surface is obtained.

[0137] Specifically, AB is connected by a 4-control-point Bezier curve, in which the head and the tail are fixed at point A and point B respectively; the control point close to the starting point A moves to P1' on the ray AP1; the control point close to the end point B moves to P2' on the ray BP2; through the above conformal transformation and constrained movement, no matter how the profile is adjusted next, it can be ensured that the inlet angle is 13°, the outlet angle is 31°, and the placement angle changes continuously and smoothly, so as to reduce the arbitrariness of manual adjustment given the profile design parameter characteristics.

[0138] The following are the constraints of each flow surface line as shown in Table 2:

[0139] Table 2

[0140]

[0141] As shown in Table 2 above, before and after the conformal transformation, each point has a unique mapping relationship. Then, the transformed curve is restored to the surface before the transformation, and the contour line on each flow surface can be obtained.

[0142] Preferably, the correlation between the blade profile and profile angle distribution R²≥0.9.

[0143] In this embodiment, S3 specifically includes the following steps:

[0144] The thickness of the blade adopts an airfoil distribution; its thickness parameters include the current point position l , Chord Length lmax 、Height of the current point of the pressure surface Yp and the current point height of the back pressure surface Yss , establish a profile table based on the thickness parameters. Fig.11 As shown, β° represents the change process of the current position between the inlet angle β1 and the outlet angle β2, and the current position / chord length represents the percentage position point of the current point in the total chord length.

[0145] The thickness of the blade adopts an airfoil distribution, with NACA0009 as the pressure surface PS and NACA0011 as the back pressure surface SS. NACA0009: indicates 0 camber, and the maximum thickness is 9% of the blade length; NACA0011: indicates 0 camber, and the maximum thickness is 11% of the blade length.

[0146] Definition, the current point position is l , the chord length is lmax , the height of the pressure surface at the current point is Yps, and the height of the back pressure surface at the current point is Yss; the above-mentioned profile is shown in Table 3:

[0147] Table 3

[0148]

[0149] According to the profile table, 16 points are drawn and circles are drawn at the corresponding points; the radius of the circle is equal to Yps. Optionally, the chord length = 190 mm.

[0150] Connect the centers of all circles to form a first curve, connect the tangents of all circles to form a second curve, draw multiple normal lines between the first curve and the second curve, and obtain the pressure surface height distribution;

[0151] The two ends of the plurality of normal lines are connected by using a Bezier curve to obtain a pressure surface profile line, and the pressure surface profile line is rotated to obtain a plurality of blade cross sections.

[0152] Preferably, the normal line of the center point of the profile line is drawn through all the circle centers to obtain the pressure surface height distribution; and the pressure surface profile line is obtained by connecting them using Bezier curves.

[0153] Specifically, the correlation of the profile thickness distribution R²≥0.9.

[0154] In this embodiment, the S4 specifically includes the following steps:

[0155] The distance relationship between the leading edge point and the center of the circle of the curved leading edge vertex of the flow surface of the wheel cover, the first section, the second section, the third section and the flow surface of the wheel disc is controlled to control the offset position of different blade sections and to stack them. In this way, the change of the blade flow channel area can be appropriately adjusted by the section deflection. The flow channel area should be changed monotonically as much as possible, either increasing or decreasing. It should be avoided that the flow channel area increases first and then decreases, or decreases first and then increases, so as to reduce momentum loss. Since the leading edge and the trailing edge are not aligned, when the impeller rotates periodically, the noise generated by the loss of wake velocity is difficult to be superimposed, which is beneficial to weaken the rotation noise. Fig.16 As shown: the vertices of the leaf shape curves on the 5 sections are A, B, C, D, and E (A is at the top of the leaf and E is at the bottom of the leaf).

[0156] Point O is the center of the wind wheel, and OA, OB, OC, OD, and OE are the lines connecting the center of the circle and the vertices of the blade curve respectively.

[0157] If the OE unit distance is taken as 1, the other curves meet the following requirements:

[0158] OD = 1.05 ~ 1.1OE;

[0159] OC = 1.1~1.15 OE;

[0160] OB = 1.15 ~ 1.16 OE;

[0161] OA=1.16-1.2 OE.

[0162] In this embodiment, S5 specifically includes the following steps:

[0163] For the impeller with Z blades, sinusoidal adjustment is adopted, and the functional relationship is:

[0164] θ'=θi+A*SIN(N*θi);

[0165] Where Z represents the number of blades; θ' represents the sinusoidal modulation angle; θi represents the equidistant distribution angle, and

[0166] θi=360 / Z; A represents the modulation angle amplitude; N represents the modulation frequency.

[0167] Preferably, the range of A is 0.1θi - 0.3θi.

[0168] Preferably, N=1. N is generally 1, and when it is not 1, Z / N=K is followed, where K is an integer greater than or equal to 3, otherwise the modulation angle will be distorted. The present invention is a 7-leaf design, A is 7°, N is 1, and the following array effect is obtained, as shown in Table 4:

[0169] Table 4

[0170]

[0171] In this embodiment, equidistant distribution means that the angles between two adjacent blades are equidistant, and sinusoidal distribution means that the angles between two adjacent blades are sinusoidal. In three different competing boxes (1#, 2#, 3#), a total of four impellers (SW, HS, DK1#, DK2#) were tested and compared. The test results show that Figures 18a to 20b , where the legend SW is the product designed by the present invention. Through testing, it can be seen that the impeller has a wide range of application scenarios, strong applicability, low noise and high efficiency, and improves the competitive advantage of product strength, thus improving the quality of life for consumers. This design method saves a lot of prototype R&D costs and has great application value.

[0172] In this embodiment, the impeller design method is applicable to the design conditions of flow coefficient of 0.12-0.25, and the applicable range of impeller size is that the impeller diameter D2 is 300-500 mm, and the height b1 is 100-200 mm. It is effective and can obtain an impeller with good noise and power performance.

[0173] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, article or device. In the absence of more restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other identical elements in the process, article or device including the element.

[0174] The embodiments of the present invention are described above in conjunction with the accompanying drawings. What is disclosed is only the preferred embodiment of the present invention. However, the present invention is not limited to the above-mentioned specific implementation manner. The above-mentioned specific implementation manner is only illustrative rather than restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms and equivalent changes without departing from the scope of protection of the purpose of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A design method for a low-load backward-flowing fan impeller, characterized in that: The low-load backward-flowing blower impeller comprises an impeller chassis, a blade connecting ring and a plurality of blades; the impeller chassis and the blade connecting ring are coaxially arranged with intervals, and an impeller domain is arranged between the impeller chassis and the blade connecting ring; the plurality of blades are circumferentially distributed in the impeller domain along the rotating axis of the backward-flowing blower; The design method of the low-load backward-flowing blower impeller comprises the following steps: S1. Determine the parameters of the impeller meridian flow surface; S2. Designing a blade profile according to the meridian flow surface parameters, obtaining angle parameters of each section in the blade profile design, and drawing a corresponding profile according to the angle parameters of each section; S3, distributing the blade thickness according to the corresponding profile lines to form a plurality of blade cross sections; S4, performing blade cross-sectional stacking on a plurality of the blade cross-sections; S5. Modulate the stacked blades into a blade array to obtain a low-load backward-moving fan impeller.

2. The design method of a low-load backward-flowing blower impeller according to claim 1, characterized in that: The S1 specifically includes the following steps: Acquire the meridian flow channel parameters of the impeller fan; wherein the meridian flow channel parameters include the position information of the inlet, outlet, wheel cover, wheel disc and blade leading edge; Determine a fan size parameter constraint relationship according to the meridian flow channel parameters, and obtain a meridian flow surface according to the fan size parameter constraint relationship; Among them, three sections are divided into three sections at equal distances according to the inlet and the outlet, namely the first section, the second section and the third section; the specific definitions are as follows: The inlet radius of the flow surface of the wheel cover is Rs; The inlet radius of the flow surface of the first section is Rs1; The inlet radius of the flow surface of the second section is Rs2; The inlet radius of the flow surface of the third section is Rs3; The inlet radius of the flow surface of the wheel is Rh; The impeller radius is R2; and the following constraints exist: Rs / R2=0.79; Rs1 / R2=0.71; Rs2 / R2=0.65; Rs3 / R2=0.61; Rh / R2=0.6; B1 is the height of the inlet; B2 is the height of the outlet; And the following constraints exist: B2 / B1=0.

74.

3. The design method of a low-load backward-flowing blower impeller according to claim 2, characterized in that: In S2, the angle parameters of each cross section include an inlet angle, an outlet angle and a wrap angle; The inlet angle is the angle between the tangent of the starting point of the profile and the tangent of the axis circle at the starting point of the profile; the outlet angle is the angle between the tangent of the end point of the profile and the tangent of the axis circle at the end point of the profile; the wrap angle is the angle formed by the axis circle and the starting point and the end point of the profile; Wherein, the inlet angle is β1, the outlet angle is β2, and the wrap angle is w; 31°>β1-1>β1-2>β1-3>β1-4>β1-5>10°, β1-1 corresponds to the inlet angle of the wheel cover, β1-2 corresponds to the inlet angle of the first section, β1-3 corresponds to the inlet angle of the second section, β1-4 corresponds to the inlet angle of the third section, and β1-5 corresponds to the inlet angle of the wheel disc; 70°> w -1> w -2> w -3> w -4> w -5>40°, w -1 corresponds to the wrap angle of the wheel cover, w -2 corresponds to the wrap angle of the first section, w -3 corresponds to the wrap angle of the second section, w -4 corresponds to the wrap angle of the third section, w -5 corresponds to the wrap angle of the wheel.

4. The design method of a low-load backward-flowing blower impeller according to claim 3, characterized in that: The inlet angle is β1±5°, the outlet angle is β2±5°, and the wrap angle is w ±5°.

5. The design method of a low-load backward-flowing blower impeller according to claim 3, characterized in that: In S2, drawing corresponding profile lines according to the angle parameters of each cross section specifically includes the following steps: Determine the starting point and end point on each radial surface according to the angle parameters of each cross section; The starting point and the end point are transformed into a grid diagram through conformal transformation, l’ = f (D2-D h ); h = f (51°); where D2 is the outer diameter of the blade, D h is the inner diameter of the blade, l’ is the difference between the outer diameter of the blade and the inner diameter of the blade, h is the height of the blade, f is the conformal transformation function; in, l’、h The length can be selected as desired, and ensure l’、h The relative length increment is equal to the radial and circumferential increments; The relative relationship between the starting point and the end point is: The radial increment is R2-Rh; the circumferential angle increment is 51°; The radial increment R2-Rh is transformed into a longitudinal increment m, and the circumferential angle increment 51° is transformed into a lateral increment n; wherein m and n are both positive integers; Unit length of vertical axis: R2-Rh / m; Unit length of horizontal axis: 51° / n; In a rectangular coordinate system, a ray AP1 is drawn, which forms an angle of 13° with the horizontal direction passing through the starting point, and intersects the horizontal direction passing through the end point at a first intersection point P1; In a rectangular coordinate system, a ray BP2 forms an angle of 31° with a horizontal direction passing through the end point, and intersects with a horizontal direction passing through the starting point at a second intersection point P2; The starting point and the end point are connected by a 4-control-point Bezier curve, and the head and the tail are fixed at the starting point and the end point respectively, wherein the control point close to the starting point moves on the ray AP1 to be the first moving point P1', and the control point close to the end point moves on the ray BP2 to be the second moving point P2'; by performing conformal transformation and constrained movement, the contour line on each flow surface is obtained.

6. The design method of a low-load backward-flowing blower impeller according to claim 1, characterized in that: The S3 specifically includes the following steps: The thickness of the blade adopts an airfoil distribution; its thickness parameters include the current point position l , Chord Length lmax 、Height of the current point of the pressure surface Yp and the current point height of the back pressure surface Yss , establishing a profile table according to the thickness parameters; According to the profile table, 16 points are made and circles are made at the corresponding points; Connect the centers of all circles to form a first curve, connect the tangents of all circles to form a second curve, draw multiple normal lines between the first curve and the second curve, and obtain the pressure surface height distribution; The two ends of the plurality of normal lines are connected by using a Bezier curve to obtain a pressure surface profile line, and the pressure surface profile line is rotated to obtain a plurality of blade cross sections.

7. The design method of a low-load backward-flowing blower impeller according to claim 2, characterized in that: The S4 specifically includes the following steps: The distance relationship between the leading edge point and the center of the curve leading edge vertex of the flow surface of the wheel cover, the first section, the second section, the third section and the flow surface of the wheel disk is controlled, and the offset positions of different blade sections are controlled and stacked.

8. The design method of a low-load backward-flowing blower impeller according to claim 1, characterized in that: The S5 specifically includes the following steps: For the impeller with Z blades, sinusoidal adjustment is adopted, and the functional relationship is: θ'=θi+A*SIN(N*θi); Wherein, Z represents the number of blades; θ' represents the sinusoidal modulation angle; θi represents the equally spaced distribution angle, and θi=360° / Z; A represents the modulation angle amplitude; and N represents the modulation frequency.

9. The design method of a low-load backward-flowing blower impeller according to claim 8, characterized in that: The range of A is 0.1θi - 0.3θi.

10. The design method of a low-load backward-flowing blower impeller according to claim 8, characterized in that: Said N=1.

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