Volute, centrifugal fan, range hood and volute design method

Abstract

The invention provides a volute, a centrifugal fan, a range hood and a volute design method. The volute design method comprises the steps that the angle of a first fold line and the angle of a first bending angle are determined; the diffusion section area, located at the outlet of the volute, of the upper cover plate is bent towards the inner side of the volute by the angle of the first bending angle with the first folding line as the boundary; and / or determining the angles of a second broken line and a second bending angle; the diffusion section area, located at the outlet of the volute, of the lower cover plate is bent towards the inner side of the volute by the angle of the second bending angle with the second folding line as the boundary, and the upper cover plate is connected with the lower cover plate through an annular wall; according to the volute, the upper cover plate and / or the lower cover plate of the volute are / is bent towards the inner side of the volute in the diffusion section area of the outlet of the volute to form an approximately trapezoidal section, so that the flowing state of airflow in the outlet area of the volute is improved, and eddy current loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of centrifugal fans, and more particularly to a volute, a centrifugal fan, a range hood, and a volute design method. Background Technology

[0002] The volute is one of the core components of a centrifugal fan, and its internal three-dimensional flow is relatively complex and accompanied by vortices. Centrifugal fans of different sizes exhibit different external characteristic patterns. As the volute opening increases, the fan's peak efficiency point shifts from low flow rate to high flow rate. Currently, the national standard for range hoods, GB / T 17713-2022, includes maximum airflow and working airflow conditions, corresponding to the fan's high and low flow rates, respectively. It is generally believed that smaller centrifugal fans, due to their relatively smaller volute opening, have higher efficiency and lower noise under the working airflow condition, while larger centrifugal fans, due to their larger opening, have higher efficiency and lower noise under the maximum airflow condition. How to effectively balance the fan's performance under both conditions is one of the important design challenges for multi-blade centrifugal fans used in range hoods.

[0003] Based on the flow characteristics of the centrifugal fan's rotating surface: the impeller rotation gives the gas kinetic energy, and the airflow inside the volute accelerates circumferentially. For example... Figure 1 As shown, under maximum airflow conditions, due to the low resistance of the fan duct network, the airflow continues to accelerate, reaching its maximum upstream of the volute tongue, thus increasing the dynamic pressure at the volute outlet. However, under normal operating airflow conditions, as... Figure 2 As shown, due to the large resistance of the pipeline network, the airflow begins to decelerate near the maximum opening of the volute, which increases the static pressure at the outlet of the volute.

[0004] Therefore, the flow field distribution in the diffuser section at the volute outlet differs between the two operating conditions due to variations in pipeline resistance. Furthermore, based on the flow characteristics of the centrifugal fan's meridional plane, the airflow at the impeller outlet impacts the volute annular wall, forming vortex pairs with opposite directions and alternating intensities on the volute cross-section, resulting in vortex losses. Figure 3 The flow field distribution diagram of the diffuser section at the volute outlet of the prototype machine under the maximum air volume condition; Figure 4 This is a flow field distribution diagram of the diffuser section at the volute outlet of the prototype machine under operating airflow conditions.

[0005] In existing technologies, the maximum airflow condition and at least one intermediate operating point are selected as independent design conditions on the centrifugal fan curve. Based on the selected impeller size, a new volute profile is formed by weighting and superimposing each condition according to its importance and probability of occurrence.

[0006] Existing technologies propose a volute profile design method that offers a wider efficient operating range and superior performance under user conditions. However, in practical designs, the upper limit of the volute profile opening adjustment is limited by the size of the fan frame, affecting the improvement of fan performance. Furthermore, existing technologies pay relatively little attention to the internal flow field of the fan and do not address structural improvements for optimizing flow field details. Particularly in the two operating conditions of a range hood, the different levels of duct resistance lead to differences in the internal flow field. Specifically, in the diffuser section at the volute outlet, under maximum airflow conditions, due to lower duct resistance, the airflow continues to flow, reaching its maximum upstream of the volute tongue, resulting in increased dynamic pressure at the volute outlet. Conversely, under normal airflow conditions, due to higher duct resistance, the airflow begins to decelerate near the maximum volute opening, leading to increased static pressure at the volute outlet.

[0007] Conventional volute profile design is based on the "equal circulation method." The structural parameters of the fan are calculated according to the preset requirements for airflow, pressure, and speed under certain operating conditions, and its cross-section is generally rectangular. Inappropriate design of the volute opening or flow area can lead to a significant increase in steady-flow force, affecting fan performance. For vortex convection characteristics, the ideal volute cross-section is circular, which offers the highest airflow efficiency. However, if the cross-section is designed as circular, the impeller height will be limited once the impeller diameter reaches a certain size. Summary of the Invention

[0008] The technical problem to be solved by this disclosure is to overcome the defects of low air outlet efficiency and unsatisfactory flow characteristics of rectangular cross-section volutes in the prior art, and to provide a volute, a centrifugal fan, a range hood, and a volute design method.

[0009] This disclosure solves the above-mentioned technical problems through the following technical solution:

[0010] In a first aspect, a method for designing the volute casing of a centrifugal fan is provided, the method comprising the following steps:

[0011] Determine the angles of the first fold line and the first bending angle; bend the upper cover plate in the diffuser section region at the volute outlet towards the inward side of the volute, using the first fold line as the boundary; and / or,

[0012] Determine the angles of the second fold line and the second bending angle; bend the lower cover plate in the diffuser section area of ​​the volute outlet towards the inside of the volute with the second fold line as the boundary;

[0013] The upper cover plate is connected to the lower cover plate via an annular wall.

[0014] Optionally, the volute design method further includes:

[0015] A plane rectangular coordinate system is established by selecting the impeller center of the centrifugal fan as the origin;

[0016] The first broken line is projected perpendicularly onto the Cartesian coordinate system. The perpendicular projection of one endpoint of the first broken line is located in the second quadrant of the Cartesian coordinate system, and the perpendicular projection of the other endpoint of the first broken line is located at the intersection of the profile of the volute and the negative half-axis of the transverse axis; and / or,

[0017] The second broken line is projected vertically onto the plane rectangular coordinate system. The vertical projection of one endpoint of the second broken line is located in the second quadrant of the plane rectangular coordinate system, and the vertical projection of the other endpoint of the second broken line is located at the intersection of the profile of the volute and the negative half-axis of the horizontal axis.

[0018] Optionally, the volute design method further includes:

[0019] The first bending angle is the angle between the intersection of the plane containing the first bending portion and the plane containing the outlet end of the volute, and the plane containing the first cover plate. The first bending portion is the part of the upper cover plate that bends inward toward the volute along the first bending line. The first cover plate is the part of the upper cover plate that is not bent. And / or,

[0020] The second bending angle is the angle between the intersection of the plane containing the second bending portion and the plane containing the exit end of the volute, and the plane containing the second cover plate. The second bending portion is the part of the lower cover plate that bends inward toward the volute along the second bending line. The second cover plate is the part of the lower cover plate that is not bent.

[0021] Optionally, the volute design method further includes:

[0022] An orthogonal experiment was conducted based on the working air volume, maximum air volume, total pressure efficiency under working air volume condition, and total pressure efficiency under maximum air volume condition of the range hood containing the volute to obtain the constraint range of the first bending angle and the second bending angle.

[0023] The weighted air volume is obtained by weighting the working air volume and the maximum air volume, and the weighted total pressure efficiency is obtained by weighting the total pressure efficiency under the working air volume condition and the total pressure efficiency under the maximum air volume condition.

[0024] Based on the constraints of the first bend angle and the second bend angle, the optimal solutions for the first bend angle and the second bend angle are solved with maximizing the weighted air volume as the first objective function and maximizing the weighted total pressure efficiency as the second objective function.

[0025] Optionally, the weighting coefficient of the working air volume is determined based on the initial outlet area of ​​the volute, the initial working air volume, and the outlet area and working air volume of the volute after bending.

[0026] The weighting coefficient for the maximum air volume is determined based on the initial outlet area, the initial maximum air volume, and the outlet area and maximum air volume after the volute is bent.

[0027] The weighting coefficient of the total pressure efficiency under the working air volume condition is determined based on the initial outlet area, the total pressure efficiency under the initial working air volume condition, and the outlet area and total pressure efficiency under the working air volume condition after the volute is bent.

[0028] The weighting coefficient of the total pressure efficiency under the maximum air volume condition is determined based on the initial outlet area, the total pressure efficiency under the initial maximum air volume condition, and the outlet area and total pressure efficiency under the maximum air volume condition after the volute is bent.

[0029] Optionally, the volute design method further includes:

[0030] The range of the fillet radius of the first bend and the fillet radius of the second bend is determined; wherein, the fillet radius of the first bend is less than or equal to the width of the first gap, the first gap being the axial gap between the first cover plate and the upper end ring of the impeller of the centrifugal fan; the fillet radius of the second bend is less than or equal to the width of the second gap, the second gap being the axial gap between the second cover plate and the lower end ring of the impeller;

[0031] The rounded corners of the first bend and the second bend are set according to the range.

[0032] In a second aspect, a volute for a centrifugal fan is provided, the volute comprising an annular wall, an upper cover plate, and a lower cover plate, the upper cover plate being connected to the lower cover plate via the annular wall; wherein the volute is determined according to the volute design method described in the first aspect;

[0033] The upper cover plate, located in the diffuser section region of the volute outlet, bends inward towards the volute at the angle of a first bend line, wherein the radius of the first bend is less than or equal to the width of the first gap; and / or,

[0034] The lower cover plate is located in the diffuser section region of the volute outlet, and bends towards the inside of the volute at the angle of the second bend line. The radius of the rounded corner of the second bend is less than or equal to the width of the second gap.

[0035] Thirdly, a centrifugal fan is provided, the centrifugal fan comprising the volute as described in the first aspect.

[0036] Optionally, the centrifugal fan includes an air outlet shroud, the inlet end of which is connected to the outlet end of the volute, and the inlet cross-section of the air outlet shroud matches the outlet cross-section of the volute.

[0037] Fourthly, a range hood is provided, the range hood including the centrifugal fan as described in the third aspect.

[0038] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this disclosure.

[0039] The positive and progressive effects of this disclosure are as follows: by bending the upper cover plate in the diffuser section region at the volute outlet with the first bend line as the boundary towards the inside of the volute, the angle of the first bend angle is improved; and / or by bending the lower cover plate in the diffuser section region at the volute outlet with the second bend line as the boundary towards the inside of the volute, an approximately trapezoidal cross section is formed, thereby improving the flow state of the airflow in the volute outlet region and reducing eddy current losses. Attached Figure Description

[0040] Figure 1 This is an airflow diagram inside the prototype's volute under maximum airflow conditions.

[0041] Figure 2 This is an airflow diagram inside the prototype machine's volute under operating airflow conditions.

[0042] Figure 3 The flow field distribution diagram of the diffuser section at the volute outlet of the prototype machine under the maximum air volume condition;

[0043] Figure 4 This is a flow field distribution diagram of the diffuser section at the volute outlet of the prototype machine under operating air volume conditions.

[0044] Figure 5 A flowchart illustrating a centrifugal fan volute design method provided in Embodiment 1 of this disclosure;

[0045] Figure 6 A method for establishing a plane rectangular coordinate system is provided in Embodiment 1 of this disclosure;

[0046] Figure 7 Another method for establishing a plane rectangular coordinate system provided in Embodiment 1 of this disclosure;

[0047] Figure 8 A schematic diagram of a first bending angle and a second bending angle provided in Embodiment 1 of this disclosure;

[0048] Figure 9 A partial flowchart of a centrifugal fan volute design method provided in Embodiment 1 of this disclosure;

[0049] Figure 10 The main effect diagram of the mean air volume of the centrifugal fan casing under different first bending angles α and second bending angles β provided in Embodiment 1 of this disclosure;

[0050] Figure 11The main effect diagram of the mean total pressure efficiency corresponding to different first bending angles α and second bending angles β for the volute of a centrifugal fan provided in Embodiment 1 of this disclosure under working air volume conditions;

[0051] Figure 12 The main effect diagram of the mean air volume of the centrifugal fan casing under the maximum air volume condition provided in Embodiment 1 of this disclosure, corresponding to different first bending angles α and second bending angles β;

[0052] Figure 13 The main effect diagram of the mean total pressure efficiency corresponding to different first bending angles α and second bending angles β for the volute of a centrifugal fan provided in Embodiment 1 of this disclosure under the maximum air volume condition;

[0053] Figure 14 This is a turbulent kinetic energy cloud map of the prototype machine at the volute outlet section under working air volume conditions, provided in Embodiment 1 of this disclosure.

[0054] Figure 15 This provides a turbulent kinetic energy cloud map of the volute outlet section of Scheme 6 under working airflow conditions, as shown in Embodiment 1 of this disclosure.

[0055] Figure 16 This provides a turbulent kinetic energy cloud map of the prototype machine at the volute outlet section under maximum airflow conditions, as shown in Embodiment 1 of this disclosure.

[0056] Figure 17 This provides a turbulent kinetic energy cloud map of the volute outlet section of Scheme 6 under maximum airflow conditions, as shown in Embodiment 1 of this disclosure.

[0057] Figure 18 A partial flowchart of a centrifugal fan volute design method provided in Embodiment 1 of this disclosure;

[0058] Figure 19 A schematic diagram showing the fillet radius of a first bend and a second bend, provided in Embodiment 1 of this disclosure;

[0059] Figure 20 This is a schematic diagram of the volute of a centrifugal fan provided in Embodiment 2 of this disclosure;

[0060] Figure 21 This is a schematic diagram of the structure of a centrifugal fan provided in Embodiment 3 of this disclosure. Detailed Implementation

[0061] The present disclosure is further illustrated below by way of embodiments, but the present disclosure is not limited to the scope of the embodiments described herein.

[0062] The prefixes such as "first" and "second" used in this disclosure are merely for distinguishing different descriptive objects and do not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes used to distinguish descriptive objects in this disclosure does not constitute a limitation on the described objects. The description of the described objects is given in the claims or the context of the embodiments, and should not be construed as an unnecessary limitation. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0063] The total pressure efficiency in this disclosure reflects the conversion efficiency of a range hood between airflow and air pressure at a specified air volume. Specifically, total pressure efficiency refers to the efficiency of a range hood in converting airflow and air pressure at a specified air volume (typically 7m³ / h). 3 The ratio of the total air pressure under standard conditions at that airflow rate ( / min) to the input power of the main motor. The larger this ratio, the higher the conversion efficiency of the centrifugal fan in terms of airflow and air pressure, that is, the better the performance of the equipment.

[0064] Example 1

[0065] Figure 5 This is a flowchart illustrating a centrifugal fan volute design method provided in this embodiment. The volute design method includes the following steps:

[0066] S101. Determine the angles of the first broken line and the first bend angle.

[0067] S102, bend the upper cover plate in the diffuser section area of ​​the volute outlet towards the inside of the volute at the angle of the first bending angle, with the first fold line as the boundary.

[0068] S103. Determine the angles of the second broken line and the second bend angle.

[0069] S104. The lower cover plate is bent towards the inside of the volute at the angle of the second bending angle, with the second fold line as the boundary, in the diffuser section area of ​​the volute outlet.

[0070] The upper cover plate is connected to the lower cover plate via an annular wall.

[0071] In one optional implementation, the volute can be designed using only steps S101 and S102; resulting in a volute in which the upper cover plate is located in the diffuser section region of the volute outlet, and the first bending angle is bent inwards from the first fold line as the boundary.

[0072] In an optional embodiment, the volute can be designed using only steps S103 and S104 to obtain a volute in which the lower cover plate is located in the diffuser section region of the volute outlet and bends towards the inside of the volute at the angle of the second bending angle, with the second fold line as the boundary.

[0073] In one optional embodiment, the volute can also be designed through steps S101, S102, S103, and S104; resulting in a volute in which the upper cover plate is located in the diffuser section region of the volute outlet and bends towards the inside of the volute along the first bend line, and the lower cover plate is located in the diffuser section region of the volute outlet and bends towards the inside of the volute along the second bend line.

[0074] In this embodiment, due to the axial dynamic-static interference gap between the volute and the impeller, circumferential vortex flow will cause leakage losses at this point; especially under operating airflow conditions, the leakage losses increase due to the increased pressure inside the volute. To address the aforementioned vortex flow losses and dynamic-static interference gap, the upper and lower cover plates are bent inwards towards the volute along a first and a second fold line, respectively.

[0075] In one optional implementation, the volute design method specifically includes the following steps:

[0076] A plane rectangular coordinate system is established by selecting the impeller center of the centrifugal fan as the origin.

[0077] The first broken line is projected vertically onto the plane rectangular coordinate system. The vertical projection of one endpoint of the first broken line is located in the second quadrant of the plane rectangular coordinate system, and the vertical projection of the other endpoint of the first broken line is located at the intersection of the profile of the volute and the negative half-axis of the horizontal axis.

[0078] The second broken line is projected vertically onto the plane rectangular coordinate system. The vertical projection of one endpoint of the second broken line is located in the second quadrant of the plane rectangular coordinate system, and the vertical projection of the other endpoint of the second broken line is located at the intersection of the profile of the volute and the negative half-axis of the horizontal axis.

[0079] The establishment of the Cartesian coordinate system is unrestricted. In a specific example, the Cartesian coordinate system is as follows: Figure 6 As shown, the vertical projection A1 of one endpoint of the first broken line is located in the second quadrant of the plane rectangular coordinate system, and the vertical projection A2 of the other endpoint of the first broken line is located at the intersection of the profile of the volute and the negative half-axis of the horizontal axis.

[0080] In another specific example, we can also establish such as Figure 7The diagram illustrates a Cartesian coordinate system. The vertical projection A1 of one endpoint of the first broken line is located in the first quadrant of the Cartesian coordinate system, and the vertical projection A2 of the other endpoint of the first broken line is located in the second quadrant of the Cartesian coordinate system. In an optional embodiment, the first bending angle is the angle between the intersection of the plane containing the first bent portion and the plane containing the outlet end of the volute, and the plane containing the first cover plate. The first bent portion is the part of the upper cover plate that bends inward toward the volute along the first broken line, and the first cover plate is the part of the upper cover plate that is not bent.

[0081] The second bending angle is the angle between the intersection of the plane where the second bending portion is located and the plane where the outlet end of the volute is located, and the plane where the second cover plate is located. The second bending portion is the part of the lower cover plate that bends inward toward the volute along the second bending line. The second cover plate is the part of the lower cover plate that is not bent.

[0082] In a specific example, such as Figure 8 As shown, the angle between the intersection of the plane where the first bend is located and the plane where the outlet end of the volute is located and the plane where the first cover plate is located is the first bend angle α, and the angle between the intersection of the plane where the second bend is located and the plane where the outlet end of the volute is located and the plane where the second cover plate is located is the second bend angle β.

[0083] In another specific example, the angle between the plane where the first bend is located and the plane where the first cover plate is located can be selected as the first bend angle, and the angle between the plane where the second bend is located and the plane where the first cover plate is located can be selected as the first bend angle.

[0084] In one alternative implementation, such as Figure 9 As shown, the volute design method specifically includes steps S105 to S107:

[0085] S105. An orthogonal test is conducted based on the working air volume, maximum air volume, total pressure efficiency under working air volume condition, and total pressure efficiency under maximum air volume condition of the range hood containing the volute to obtain the constraint range of the first bending angle and the second bending angle.

[0086] In this embodiment, to obtain the constraint range of the first bending angle α and the second bending angle β, a three-level orthogonal experiment is conducted using the first bending angle α and the second bending angle β as two factors. The relationship between the volute flow area and the fan performance is as follows: within a certain range, a smaller volute flow area can improve the fan's operating efficiency under normal airflow conditions, while a larger flow area can improve the fan's operating efficiency under maximum airflow conditions. However, a smaller bending angle cannot suppress the eddy currents in the volute outlet region, while a larger bending angle will reduce the volute outlet flow area, causing a decrease in the fan's efficiency under maximum airflow conditions. Based on the above principles, the three design levels of the first bending angle α and the second bending angle β are coded and explained respectively.

[0087] In a specific example, the original volute outlet rectangle is taken as the lower level of α, i.e., α = 0°; the maximum bending point of the first bend is located on the plane where the impeller upper plate is located, corresponding to the middle level of α, i.e., α = θ (in this embodiment, α = θ = 5°); and α = 2θ corresponds to the higher level of α. Furthermore, the air volume Q and total pressure efficiency η of the entire range hood under two operating conditions—working air volume condition and maximum air volume condition—are used as response parameters. Orthogonal experiments and analyses are conducted using orthogonal experimental tables and numerical simulations.

[0088] The relationships between the air volume Q and total pressure efficiency η under the operating air volume condition and the maximum air volume condition and the levels of various factors are as follows: Figure 10-13 As shown. Among them, Figure 10 The main effect diagram of the mean air volume corresponding to different first bending angles α and second bending angles β under the working air volume condition; Figure 11 The main effect diagram of the mean total pressure efficiency corresponding to different first bending angles α and second bending angles β under the working air volume condition;

[0089] Figure 12 This is the main effect plot of the mean air volume for different first bending angles α and second bending angles β under the maximum air volume condition; Figure 13 This is the main effect diagram of the mean total pressure efficiency corresponding to different first bending angles α and second bending angles β under the maximum air volume condition.

[0090] like Figure 10 and 11 As shown, under normal operating airflow conditions, the first bending angle α and the second bending angle β of the range hood exhibit a positive correlation with the airflow. However, when the first bending angle α = 2θ, the overall efficiency decreases compared to the prototype. Meanwhile, as... Figure 12 and 13As shown, under maximum airflow conditions, the first bending angle α and the second bending angle β of the range hood exhibit a negative correlation with both airflow and total pressure efficiency. Within a certain parameter range, the above method can improve the performance of the range hood under normal airflow conditions, but it will also affect its performance under maximum airflow conditions. Based on the above research and analysis, the constraint range for the first bending angle α is further obtained as: 0°≤α≤θ, and the constraint range for the second bending angle β is 0°≤β≤2θ.

[0091] S106. The weighted air volume is obtained by weighting the working air volume and the maximum air volume, and the weighted total pressure efficiency is obtained by weighting the total pressure efficiency under the working air volume condition and the total pressure efficiency under the maximum air volume condition.

[0092] In this embodiment, in order to take into account the performance of both the maximum air volume condition and the working air volume condition and obtain the preferred design scheme, the overall air volume and total pressure efficiency under the two conditions are weighted.

[0093] S107. Based on the constraints of the first bend angle and the second bend angle, with maximizing the weighted air volume as the first objective function and maximizing the weighted total pressure efficiency as the second objective function, solve for the optimal solutions of the first bend angle and the second bend angle.

[0094] In this embodiment, based on the above-mentioned influence of the first bending angle α and the second bending angle β on the performance of the fan under two operating conditions in the implementation plan, and combined with the results of orthogonal experiments, a parameter weighting method that takes into account both operating conditions is proposed to obtain the preferred scheme combination design.

[0095] In one optional implementation, the weighting coefficient of the working air volume is determined based on the initial outlet area of ​​the volute, the initial working air volume, and the outlet area and working air volume after the volute is bent.

[0096] The weighting coefficient for the maximum air volume is determined based on the initial outlet area, the initial maximum air volume, and the outlet area and maximum air volume after the volute is bent.

[0097] The weighting coefficient of the total pressure efficiency under the working air volume condition is determined based on the initial outlet area, the total pressure efficiency under the initial working air volume condition, and the outlet area and total pressure efficiency under the working air volume condition after the volute is bent.

[0098] The weighting coefficient of the total pressure efficiency under the maximum air volume condition is determined based on the initial outlet area, the total pressure efficiency under the initial maximum air volume condition, and the outlet area and total pressure efficiency under the maximum air volume condition after the volute is bent.

[0099] In this embodiment, the weighting coefficient is calculated based on the change in response value under two operating conditions, as well as the change in the volute outlet area. A larger s-value indicates a higher sensitivity of this factor to airflow and total pressure efficiency. The calculation formula is as follows:

[0100]

[0101] In the formula: n is the number of test samples; Δs i Δy represents the change in the volute exit area, i.e., the initial exit area minus the exit area after the volute is bent; s0 is the initial exit area, i.e., the exit area of ​​a conventional rectangular volute; Δy i y0 represents the change in air volume or total pressure efficiency, which is the initial air volume minus the air volume after the volute is bent, or the initial total pressure efficiency minus the total pressure efficiency after the volute is bent; y0 represents the initial air volume or initial total pressure efficiency.

[0102] Therefore, s is calculated using the above formula (1). Q1 At that time, Q1 is the working air volume; Δy i The change in air volume under the working air volume condition is the initial air volume under the working air volume condition minus the air volume under the working air volume condition after the volute is bent; y0 is the initial air volume under the working air volume condition.

[0103] Calculate s using the above formula (1) Q2 At that time, Q2 represents the maximum airflow; Δy i y0 represents the change in air volume under the maximum air volume condition, which is the initial air volume under the maximum air volume condition minus the air volume under the maximum air volume condition after the volute is bent; y0 represents the initial air volume under the maximum air volume condition.

[0104] Calculate s using the above formula (1) η1 When η1 is the total pressure efficiency under the working air volume condition; Δy i The change in total pressure efficiency under operating airflow conditions is the initial total pressure efficiency under operating airflow conditions minus the total pressure efficiency under operating airflow conditions after the volute is bent; y0 is the initial total pressure efficiency under operating airflow conditions.

[0105] Calculate s using the above formula (1) η2 At that time, η2 is the total pressure efficiency under the maximum air volume condition; Δy i The change in total pressure efficiency under maximum airflow conditions is the initial total pressure efficiency under maximum airflow conditions minus the total pressure efficiency under maximum airflow conditions after the volute is bent; y0 is the initial total pressure efficiency under maximum airflow conditions.

[0106] Therefore, the weighting factor for the working air volume is:

[0107] The weighting factor for maximum air volume is:

[0108] The weighting factor for the total pressure efficiency under operating air volume conditions is:

[0109] The weighting factor for the total pressure efficiency under maximum airflow conditions is:

[0110] Therefore, the weighted air volume is:

[0111] The weighted total pressure efficiency is:

[0112] In a specific example, we can calculate the following:

[0113] S Q1 =0.17, S Q2 =0.022, S η1 =0.3468, S η2 =0.4178.

[0114] Therefore, the weighted air volume is:

[0115] The weighted total pressure efficiency is:

[0116] The weighted air volume obtained by further weighting the two operating conditions and weighted efficiency To optimize the objective and obtain the optimal solution within the constraints, the mathematical model established is as follows:

[0117] Objective function:

[0118] Constraints:

[0119] In this embodiment, the weighted air volume is obtained by calculating the results of the above orthogonal experiment. and weighted efficiency As shown in Table 1:

[0120] Table 1

[0121]

[0122] Table 1 shows that, with the first bending angle α = 5° and the second bending angle β = 10°, the weighted air volume... and weighted efficiency Therefore, the optimal solution in this embodiment is α = 5° and β = 10°. Finally, scheme 6 was selected for prototyping and compared with the prototype machine. The test results are shown in Table 2, where the prototype machine refers to the range hood including the corresponding unbent volute in this embodiment.

[0123] Table 2

[0124]

[0125]

[0126] As shown in Table 2, the total pressure efficiency of the range hood under different operating conditions is higher than that of the prototype machine when the first bending angle α = 5° and the second bending angle β = 10° is lower than that of the prototype machine.

[0127] in, Figure 14 This embodiment provides a turbulent kinetic energy cloud map of the prototype machine at the volute outlet section under operating airflow conditions. Figure 15 This embodiment provides a turbulent kinetic energy cloud diagram of the volute outlet section of Scheme 6 under working air volume conditions; Figure 16 This embodiment provides a turbulent kinetic energy cloud map of the prototype machine at the volute outlet section under maximum airflow conditions. Figure 17 This embodiment provides a turbulent kinetic energy cloud map of the volute outlet section of Scheme 6 under the maximum airflow condition.

[0128] Because the airflow at the impeller outlet impacts the annular wall of the volute, vortex pairs with opposite directions and alternating intensities are formed on the cross-section of the volute, resulting in vortex losses. Figure 14-17 As can be seen from the turbulent kinetic energy cloud diagram, Scheme 6 in this embodiment reduces eddy current losses compared to the prototype.

[0129] In one alternative implementation, such as Figure 18 As shown, the design method further includes:

[0130] S108. Determine the range of the fillet radius of the first bend and the fillet radius of the second bend; wherein, the fillet radius of the first bend is less than or equal to the width of the first gap, the first gap being the axial gap between the first cover plate and the upper end ring of the impeller of the centrifugal fan; the fillet radius of the second bend is less than or equal to the width of the second gap, the second gap being the axial gap between the second cover plate and the lower end ring of the impeller.

[0131] S109. Set the fillet of the first bend and the fillet of the second bend according to the range.

[0132] In this embodiment, to reduce the turbulence intensity in the bending areas of the upper and lower cover plates, the bending portions of the upper and lower cover plates are designed with rounded corners. For example... Figure 19 As shown, the maximum radius R1 of the first bend is the same as the axial clearance B1 between the upper cover plate and the upper end ring of the impeller, and the maximum radius R2 of the second bend is the same as the axial clearance B2 between the lower cover plate and the lower end ring of the impeller.

[0133] Example 2

[0134] Figure 20 This is a schematic diagram of the structure of a centrifugal fan casing provided in this embodiment. The casing includes an annular wall 201, an upper cover plate 202, and a lower cover plate 203. The upper cover plate 202 is connected to the lower cover plate 203 through the annular wall 201.

[0135] In one alternative embodiment, the upper cover plate is bent inward toward the inside of the volute in the diffuser section region of the volute outlet.

[0136] In one alternative embodiment, the lower cover plate is bent inward toward the inside of the volute in the diffuser section region of the volute outlet.

[0137] In one optional embodiment, both the upper cover plate and the lower cover plate are bent inward toward the inside of the volute in the diffuser section region of the volute outlet.

[0138] In this embodiment, due to the axial dynamic-static interference gap between the volute and the impeller, circumferential vortex flow will cause leakage losses at this location; especially under operating airflow conditions, the leakage losses increase due to the increased pressure inside the volute. To address the aforementioned vortex flow losses and dynamic-static interference gap, the upper cover plate and / or the lower cover plate are bent inwards from the diffuser section region at the volute outlet, forming an approximately trapezoidal cross-section. This improves the airflow state in the volute outlet region and reduces vortex losses.

[0139] In one optional implementation, a plane rectangular coordinate system is established with the center of the centrifugal fan impeller as the origin.

[0140] The upper cover plate is located in the diffuser section region of the volute outlet, and bends inward towards the volute along a first bend line. The first bend line is projected vertically onto the Cartesian coordinate system, with one endpoint of the first bend line projected into the second quadrant of the Cartesian coordinate system, and the other endpoint projected into the intersection of the volute profile and the negative half-axis of the transverse axis. The first bend angle is the angle between the intersection of the plane containing the first bend and the plane containing the volute outlet, and the plane containing the first cover plate. The first bend is the portion of the upper cover plate that bends inward towards the volute along the first bend line, and the first cover plate is the portion of the upper cover plate that is not bent.

[0141] The lower cover plate is located in the diffuser section region of the volute outlet, and bends inward towards the volute along the second bend line. The second bend line is projected vertically onto the Cartesian coordinate system, with one endpoint of the second bend line projected into the second quadrant of the Cartesian coordinate system, and the other endpoint projected into the intersection of the volute profile and the negative half-axis of the transverse axis. The second bend angle is the angle between the intersection of the plane containing the second bend and the plane containing the volute outlet, and the plane containing the second cover plate. The second bend is the portion of the lower cover plate that bends inward towards the volute along the second bend line, and the second cover plate is the portion of the lower cover plate that is not bent.

[0142] In this embodiment, such as Figure 6 As shown, an XY plane rectangular coordinate system is established with the impeller center of the centrifugal fan as the origin. The vertical projection A1 of one endpoint of the first broken line is located in the second quadrant of the plane rectangular coordinate system, and the vertical projection A2 of the other endpoint of the first broken line is located at the intersection of the profile of the volute and the negative half-axis of the horizontal axis.

[0143] like Figure 8 As shown, the first bending angle α is the angle between the intersection of the plane where the first bending part is located and the plane where the outlet end of the volute is located and the plane where the first cover plate is located, and the second bending angle β is the angle between the intersection of the plane where the second bending part is located and the plane where the outlet end of the volute is located and the plane where the second cover plate is located.

[0144] In one optional embodiment, the radius of the fillet of the first bend is less than or equal to the width of the first gap; wherein, the first gap is the axial gap between the first cover plate and the upper end ring of the impeller of the centrifugal fan.

[0145] In one optional embodiment, the radius of the fillet of the second bend is less than or equal to the width of the second gap; wherein the second gap is the axial gap between the second cover plate and the lower end ring of the impeller.

[0146] In this embodiment, such as Figure 19 As shown, the radius of the rounded corner R1 of the first bend is less than or equal to the width B1 of the first gap; the radius of the rounded corner R2 of the second bend is less than or equal to the width B2 of the second gap. This embodiment further reduces the turbulence intensity in the bending areas of the upper and lower cover plates through the rounded corner design.

[0147] Example 3

[0148] Figure 21 This is a schematic diagram of the structure of a centrifugal fan provided in this embodiment. The centrifugal fan includes a volute 301 as described in Embodiment 2.

[0149] In this embodiment, by bending the upper cover plate and / or the lower cover plate in the diffuser section region of the volute outlet toward the inside of the volute, an approximately trapezoidal cross section is formed, which improves the flow state of the airflow in the volute outlet region and reduces eddy current losses.

[0150] In one alternative implementation, such as Figure 21 As shown, the centrifugal fan includes an air outlet shroud 302, the inlet end of which is connected to the outlet end of the volute, and the inlet cross-section of the air outlet shroud matches the outlet cross-section of the volute.

[0151] In this embodiment, the inlet cross-section of the air outlet shroud matches the outlet cross-section of the volute, which better matches the gas flow at the outlet of the volute, further improving the performance of the centrifugal fan and reducing noise.

[0152] Example 4

[0153] This embodiment provides a range hood, which includes a centrifugal fan as described in Embodiment 3. Due to the axial dynamic-static interference gap between the volute and the impeller, circumferential vortex flow will cause leakage losses at this point; especially under operating airflow conditions, the leakage losses increase due to the increased pressure inside the volute. However, in this embodiment, the centrifugal fan of the range hood uses a volute as described in Embodiment 2. To address the aforementioned vortex flow losses and dynamic-static interference gap, the upper and / or lower cover plates of the volute are bent inwards in the diffuser section region at the volute outlet, forming an approximately trapezoidal cross-section. This improves the airflow state in the volute outlet region and reduces vortex losses. Therefore, this range hood can balance performance and noise levels under both operating conditions: operating airflow and maximum airflow.

[0154] While specific embodiments of this disclosure have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this disclosure, but all such changes and modifications fall within the scope of protection of this disclosure.

Claims

1. A method of designing a volute for a centrifugal fan, characterized by, The volute design method comprises the following steps: determining a first fold line and an angle of a first fold angle; folding the upper cover plate in the first fold line at the outlet of the volute to the inside of the volute by the angle of the first fold angle; and / or, determining a second fold line and an angle of a second fold angle; folding the lower cover plate in the second fold line at the outlet of the volute to the inside of the volute by the angle of the second fold angle; wherein the upper cover plate is connected to the lower cover plate by a ring wall.

2. The volute design method as claimed in claim 1, wherein, The volute design method further comprises: selecting the center of the impeller of the centrifugal fan as the origin of the coordinate system to establish a plane rectangular coordinate system; the vertical projection of the first fold line onto the plane rectangular coordinate system, the vertical projection of one end point of the first fold line is located in the second quadrant of the plane rectangular coordinate system, and the vertical projection of the other end point of the first fold line is located at the intersection of the profile line of the volute and the negative half of the horizontal axis; and / or, the vertical projection of the second fold line onto the plane rectangular coordinate system, the vertical projection of one end point of the second fold line is located in the second quadrant of the plane rectangular coordinate system, and the vertical projection of the other end point of the second fold line is located at the intersection of the profile line of the volute and the negative half of the horizontal axis.

3. The volute design method as claimed in claim 1, wherein The volute design method further comprises: the first fold angle is the included angle between the intersection line of the plane of the first fold part and the plane of the outlet end of the volute and the plane of the first cover plate, the first fold part is the part of the upper cover plate folded to the inside of the volute in the first fold line, and the first cover plate is the part of the upper cover plate not folded; and / or, the second fold angle is the included angle between the intersection line of the plane of the second fold part and the plane of the outlet end of the volute and the plane of the second cover plate, the second fold part is the part of the lower cover plate folded to the inside of the volute in the second fold line, and the second cover plate is the part of the lower cover plate not folded.

4. The volute design method of claim 1, wherein The volute design method further comprises: According to the working air volume, the maximum air volume, the total pressure efficiency of the working air volume condition, and the total pressure efficiency of the maximum air volume condition of the range hood in which the volute is located, an orthogonal test is performed to obtain the constraint range of the first fold angle and the second fold angle; According to the working air volume and the maximum air volume, a weighted air volume is obtained, and according to the total pressure efficiency of the working air volume condition and the total pressure efficiency of the maximum air volume condition, a weighted total pressure efficiency is obtained; Based on the constraint range of the first fold angle and the second fold angle, the maximum weighted air volume is taken as the first objective function, and the maximum weighted total pressure efficiency is taken as the second objective function, and the optimal solution of the first fold angle and the second fold angle is solved.

5. The volute design method of claim 4, wherein: the weighting coefficient of the working air volume is determined according to the initial outlet area of the volute, the initial working air volume, and the outlet area and working air volume of the volute after folding; the weighting coefficient of the maximum air volume is determined according to the initial outlet area, the initial maximum air volume, and the outlet area and maximum air volume of the volute after folding. The weighted coefficient of the total pressure efficiency under the working air volume condition is determined according to the initial outlet area, the total pressure efficiency under the initial working air volume condition, and the outlet area and the total pressure efficiency under the working air volume condition after the volute is bent; The weighted coefficient of the total pressure efficiency under the maximum air volume condition is determined according to the initial outlet area, the total pressure efficiency under the initial maximum air volume condition, and the outlet area and the total pressure efficiency under the maximum air volume condition after the volute is bent.

6. The volute design method as claimed in claim 3, wherein, The volute design method further comprises: determining a range of a fillet radius of the first bending part and a fillet radius of the second bending part; wherein the fillet radius of the first bending part is less than or equal to a width of a first gap, the first gap being an axial gap between the first cover plate and an upper end ring of the impeller of the centrifugal fan; the fillet radius of the second bending part is less than or equal to a width of a second gap, the second gap being an axial gap between the second cover plate and a lower end ring of the impeller; setting a fillet of the first bending part and a fillet of the second bending part according to the range.

7. A volute for a centrifugal fan, characterized by The volute comprises a ring wall, an upper cover plate and a lower cover plate, the upper cover plate being connected to the lower cover plate through the ring wall; wherein the volute is determined according to the volute design method of any one of claims 1 to 6; the upper cover plate is bent inwards to the volute at a first bending angle at a first bending line as a boundary in a diffuser region of the volute outlet, and the fillet radius of the first bending part is less than or equal to a width of a first gap; and / or the lower cover plate is bent inwards to the volute at a second bending angle at a second bending line as a boundary in the diffuser region of the volute outlet, and the fillet radius of the second bending part is less than or equal to a width of a second gap.

8. A centrifugal fan characterized by The centrifugal fan comprises the volute of claim 7.

9. The centrifugal fan of claim 8, wherein The centrifugal fan comprises an air outlet cover, an inlet end of the air outlet cover being connected to an outlet end of the volute, and an inlet cross section of the air outlet cover matching an outlet cross section of the volute.

10. A range hood characterized by, The range hood comprises the centrifugal fan of claim 8 or 9.

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