A method for designing the flow channel of a low specific speed centrifugal pump and the low specific speed centrifugal pump.

Abstract

This invention provides a flow channel design method for a low specific speed centrifugal pump and a low specific speed centrifugal pump, comprising the following steps: determining the inlet and outlet parameters of the flow channel based on the rated flow rate, rated head, and rated speed of the low specific speed centrifugal pump. These parameters include the impeller inlet and outlet diameters, the inner and outer fillets of the flow channel, the flow channel wrap angle, the inlet and outlet angles, and the inlet and outlet cross-sectional parameters. The two ends of a curve are determined using the inlet and outlet cross-sections of the flow channel. At least four transition cross-sections are set between the inlet and outlet of the flow channel. A circular arc curve connects the inlet cross-section, the transition cross-sections, and the outlet cross-section, thus determining the flow channel direction and shape. This invention can ensure that undesirable flow patterns in the flow channel are avoided as much as possible while reducing energy consumption. It guarantees the working efficiency and long-term safe and stable operation of the low specific speed centrifugal pump.

Description

Technical Field

[0001] This invention relates to the field of centrifugal pumps, and in particular to a flow channel design method for a low specific speed centrifugal pump and a low specific speed centrifugal pump. Background Technology

[0002] Specific speed n is usually referred to as s Centrifugal pumps with a specific speed of <30 are called low specific speed centrifugal pumps. Low specific speed centrifugal pumps are characterized by small flow rates and high heads, and are therefore widely used. However, their narrow flow channels and large impeller diameters lead to low operating efficiency and a tendency to generate undesirable flow patterns such as vortices within the flow channel. Therefore, solving these problems has become a key focus for the future development of low specific speed centrifugal pumps.

[0003] In recent years, scholars and technicians have proposed that the diffusion degree of the flow channel affects the working efficiency of centrifugal pumps. By designing impeller dimensions, such as changing the width of the outlet blades, the outlet area of ​​the flow channel is altered, and the ratio of the inlet and outlet areas of the flow channel can be calculated. It has been found that an inlet and outlet area ratio of 1.2 to 1.5 can reduce the energy consumption of low specific speed centrifugal pumps and improve their working efficiency.

[0004] However, this method of altering the flow channel diffusion by designing impeller dimensions cannot effectively mitigate undesirable flow conditions such as vortices in low specific speed flow channels. Furthermore, impeller design cannot directly and effectively control the flow channel, and the time and effort required to improve centrifugal pump efficiency through impeller design are also considerable. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a flow channel design method for a low specific speed centrifugal pump and a low specific speed centrifugal pump itself. This method ensures that undesirable flow patterns in the flow channel are avoided as much as possible while reducing energy consumption, thus guaranteeing the working efficiency and long-term safe and stable operation of the low specific speed centrifugal pump.

[0006] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0007] A method for designing the flow channel of a low specific speed centrifugal pump includes the following steps:

[0008] Based on the rated flow rate Q of the low specific speed centrifugal pump n Rated head H n Given the rated speed n, determine the inlet and outlet parameters of the flow channel, which include the impeller inlet and outlet diameters, the inner and outer fillets of the flow channel, the flow channel wrap angle, the inlet and outlet angles of the flow channel, and the inlet and outlet cross-sectional parameters of the flow channel;

[0009] The two ends of the curve are determined by the inlet and outlet sections of the flow channel. At least four transition sections are set between the inlet and outlet of the flow channel. The flow channel inlet section, transition section and outlet section are connected by a circular arc curve to determine the flow channel direction and shape.

[0010] Furthermore, by using a circular arc curve to connect the inlet section, transition section, and outlet section of the flow channel, the specific flow channel orientation is determined as follows:

[0011] By connecting the inlet and outlet sections of the flow channel with a circular arc curve, the flow channel orientation can be preliminarily determined.

[0012] Using the plane perpendicular to the inlet and outlet cross-sections of the flow channel and containing the center points of the inlet and outlet cross-sections as the reference plane, and with the hub as the center, the spacing between the inlet and outlet of the flow channel is... Draw at least 4 concentric circles, and mark the intersection points of the concentric circles and the arc curves. The intersection points are the centers of the transition sections; where: D2 is the impeller outlet diameter; r3 is the distance from the inlet edge of the flow channel to the axis;

[0013] Overlap the center of the inlet section of the flow channel with the center of the outlet section of the flow channel, and draw the diagonal of the inlet section of the flow channel to intersect the outlet section of the flow channel. At the same time, draw the major and minor axes of the outlet section of the flow channel to intersect the inlet section of the flow channel. Divide the eight intersection lines into four equal parts, and use a fitted curve to connect the corresponding equal parts to determine the shape of each transition section. Use a circular arc curve to connect the inlet section, transition section and outlet section of the flow channel to determine the flow channel direction and shape.

[0014] Furthermore, based on the rated flow rate Q of the low specific speed centrifugal pump... n Rated head H n Given the rated speed n, determine the impeller inlet and outlet diameters as follows:

[0015] Impeller inlet diameter D j Determined by the following formula:

[0016]

[0017] Where: D0 is the equivalent impeller inlet diameter, in meters;

[0018] k0 is a coefficient, k0 = 4.0 to 4.5;

[0019] Q n For the rated flow rate, m 3 / s;

[0020] n is the pump speed, in r / min;

[0021] d h Where is the hub diameter, in meters (m).

[0022] D jWhere is the impeller inlet diameter, in meters (m).

[0023] The impeller outlet diameter D2 is determined by the following formula:

[0024]

[0025] Where: μ d This is the correction factor for the impeller outlet diameter D2, when n s When ≤30, take μ d =1.175~1.247, when n s When n is large, take the smaller value. s Take the larger value when it is smaller;

[0026] n s For specific speed,

[0027] D2 is the impeller outlet diameter, in meters (m).

[0028] Furthermore, based on the impeller inlet diameter D of the low specific speed centrifugal pump... j Impeller outlet diameter D2 and hub diameter d n Determine the fillets on the inner and outer sides of the flow channel, specifically as follows:

[0029] The range of fillet radius r1 on the inner side of the flow channel can be determined by the following formula and then rounded down:

[0030]

[0031] Where: σ1 is the correction coefficient, taken as σ1 = 0.85 to 1.1;

[0032] D2 is the impeller outlet diameter, in meters;

[0033] D j Where is the impeller inlet diameter, in meters (m).

[0034] d h Where is the hub diameter, in meters (m).

[0035] The range of fillet radius r2 on the outer side of the flow channel can be determined by the following formula and then rounded down:

[0036] r2=σ2(D j -d n )≤r3

[0037] Where: σ2 is the correction coefficient, which is taken as σ2 = 0.9 to 1.5;

[0038] D j Where is the impeller inlet diameter, in meters (m).

[0039] d h Where is the hub diameter, in meters (m).

[0040] r3 is the distance from the inlet edge to the axis of the flow channel, in meters; it is determined by the following formula:

[0041] r3=k c (r1+D j )

[0042] Where: k c Let k be the r3 correction factor. c =1.05~1.25;

[0043] r1 is the inner fillet radius of the flow channel, m.

[0044] Furthermore, based on the impeller outlet diameter D2 and the distance r3 from the inlet edge to the shaft center of the low specific speed centrifugal pump, the flow channel wrap angle and the flow channel inlet / outlet angle are determined as follows:

[0045] The flow channel wrap angle α is calculated using the following formula:

[0046]

[0047] in:

[0048] D2 is the impeller outlet diameter, in meters;

[0049] r3 is the distance from the edge of the flow channel to the axis, in meters;

[0050] The flow channel outlet angle β2 ranges from 50° to 60°.

[0051] The inlet angle β1 of the flow channel is controlled by the flow channel wrap angle α and the outlet angle β2 of the flow channel, and the range is 75° to 85°.

[0052] Furthermore, the inlet and outlet cross-sectional parameters of the flow channels include the number of flow channels, the inlet area of ​​the flow channels, and the outlet area of ​​the flow channels, which are specifically determined as follows:

[0053] The number of flow channels Z0 is determined by the following formula:

[0054]

[0055] Where: K is a coefficient, taken as K = 6.0 to 8.5;

[0056] D2 is the impeller outlet diameter, in meters;

[0057] D j Where is the impeller inlet diameter, in meters (m).

[0058] α is the flow channel wrap angle;

[0059] Let the inlet area of ​​the flow channel be A1 and the outlet area be A2.

[0060] The inlet area A1 of the flow channel between the two blades is determined by the following formula:

[0061]

[0062] Where: r3 is the distance from the inlet edge to the axis of the flow channel, in meters;

[0063] b1 is the blade inlet width, in meters;

[0064] ψ1 represents the flow channel area utilization rate;

[0065] Z0 represents the number of flow channels;

[0066] Based on the ratio of the inlet and outlet areas of the flow channel The outlet area of ​​the flow channel is determined to be A2;

[0067] The outlet cross-section of the flow channel is elliptical, with the major semi-axis of the elliptical cross-section being a1 and the minor semi-axis being a2.

[0068] A2=a1a2π

[0069] The minor semi-axis a2 of the elliptical cross-section at the flow channel outlet should be approximately equal to the distance c2 between the front and rear shrouds of the impeller. The distance c2 between the front and rear shrouds of the impeller is determined by the following formula:

[0070]

[0071] Where: k b This is a correction factor, with a value range of k. b =1.09~1.152, when n s When k is large, b Take the smaller value; when n s When k is small b Take the larger value;

[0072] Q n For normal working flow, m 3 / s;

[0073] n is the pump speed, in r / min.

[0074] Furthermore, a horizontal straight line is introduced at the inlet of the flow channel, the length of which, d1, is determined by the following formula:

[0075] d1=(0.7~0.9)D j

[0076] Where: D j Let be the impeller inlet diameter, in meters (m).

[0077] A low specific speed centrifugal pump, wherein the flow channel is designed using the aforementioned low specific speed centrifugal pump flow channel design method.

[0078] The beneficial effects of this invention are as follows:

[0079] 1. The low specific speed centrifugal pump flow channel design method and low specific speed centrifugal pump described in this invention directly control the ratio of the flow channel inlet and outlet areas between the two blades by designing the flow channel inlet and outlet, thereby minimizing the loss between the flow channels and increasing the working efficiency of the centrifugal pump.

[0080] 2. The low specific speed centrifugal pump flow channel design method and low specific speed centrifugal pump described in this invention can effectively avoid the cumbersome design when designing blades by directly designing the flow channel, reduce the trial and error cost in the design process, and more easily avoid undesirable flow states in the flow channel of the low specific speed centrifugal pump, extend the service life of the centrifugal pump, and ensure that the pump can operate safely and efficiently for a longer period of time.

[0081] 3. The low specific speed centrifugal pump flow channel design method and low specific speed centrifugal pump described in this invention can enable such centrifugal pumps to achieve better working efficiency and operate more safely and effectively. Attached Figure Description

[0082] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, it is obvious that other drawings can be obtained from these drawings without creative effort.

[0083] Figure 1 This is a cross-sectional view of the flow channel of the low specific speed centrifugal pump described in this invention.

[0084] Figure 2 This is a cross-sectional view of the impeller flow channel described in this invention.

[0085] Figure 3 This is a flow channel transition surface diagram of the present invention.

[0086] Figure 4 This is a 3D schematic diagram of the present invention.

[0087] Figure 5 A schematic diagram showing the diagonal line drawn to indicate the overlap between the center of the inlet section and the center of the outlet section of the flow channel.

[0088] Figure 6 This is a simulation diagram of the impeller of a traditional low specific speed centrifugal pump.

[0089] Figure 7 This is a simulation diagram of the impeller of a low specific speed centrifugal pump according to an embodiment of the present invention.

[0090] In the picture:

[0091] 1-Impeller inlet; 2-Impeller outlet; 3-Flow channel. Detailed Implementation

[0092] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0093] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0094] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0095] like Figure 4 As shown in the embodiment, the ratio of the inlet and outlet cross-sectional areas of the flow channel between the two blades of the low specific speed centrifugal pump is controlled at 1.2, and the outlet cross-sectional shape is controlled to be an elliptical outlet cross-section. The flow channel design method of the low specific speed centrifugal pump specifically includes the following steps:

[0096] Based on the rated flow rate Q of the low specific speed centrifugal pump n Rated head H n Given the rated speed n, determine the inlet and outlet parameters of the flow channel. These parameters include the impeller inlet and outlet diameters, the inner and outer fillets of the flow channel, the flow channel wrap angle, the inlet and outlet angles of the flow channel, and the inlet and outlet cross-sectional parameters of the flow channel, such as... Figure 1 As shown, specifically:

[0097] Impeller inlet diameter D jDetermined by the following formula:

[0098]

[0099] Where: D0 is the equivalent impeller inlet diameter, in meters;

[0100] k0 is a coefficient, and based on statistical data, k0 = 4.0 to 4.5 is selected, taking into account both efficiency and cavitation.

[0101] Q n For the rated flow rate, m 3 / s;

[0102] n is the pump speed, in r / min;

[0103] d h Where is the hub diameter, in meters (m).

[0104] D j Where is the impeller inlet diameter, in meters (m).

[0105] The impeller outlet diameter D2 is determined by the following formula:

[0106]

[0107] Where: μ d This is the correction factor for the impeller outlet diameter D2, when n s When ≤30, take μ d =1.175~1.247, when n s When n is large, take the smaller value. s When n is small, take the larger value; that is, when n is small s When the value is close to 30, then μ d Take the lower limit value (such as a value near 1.175), and similarly, when n... s The further μ deviates from 30, the better. d Take the upper limit value.

[0108] n s For specific speed,

[0109] D2 is the impeller outlet diameter, in meters (m).

[0110] Determine the fillets on the inner and outer sides of the flow channel, specifically as follows:

[0111] The range of fillet radius r1 on the inner side of the flow channel can be determined by the following formula and then rounded down:

[0112]

[0113] Where: σ1 is the correction coefficient, taken as σ1 = 0.85 to 1.1;

[0114] D2 is the impeller outlet diameter, in meters;

[0115] D j Where is the impeller inlet diameter, in meters (m).

[0116] d h Where is the hub diameter, in meters (m).

[0117] The range of fillet radius r2 on the outer side of the flow channel can be determined by the following formula and then rounded down:

[0118] r2=σ2(D j -d n )≤r3

[0119] Where: σ2 is the correction coefficient, which is taken as σ2 = 0.9 to 1.5;

[0120] D j Where is the impeller inlet diameter, in meters (m).

[0121] d h Where is the hub diameter, in meters (m).

[0122] r3 is the distance from the inlet edge to the axis of the flow channel, in meters; it is determined by the following formula:

[0123] r3=k c (r1+D j )

[0124] Where: k c Let k be the r3 correction factor. c =1.05~1.25;

[0125] r1 is the inner fillet radius of the flow channel, m.

[0126] The flow channel wrap angle and the flow channel inlet and outlet angles are determined as follows:

[0127] The flow channel wrap angle α is calculated using the following formula:

[0128]

[0129] in:

[0130] D2 is the impeller outlet diameter, in meters;

[0131] r3 is the distance from the edge of the flow channel to the axis, in meters;

[0132] The flow channel outlet angle β2 ranges from 50° to 60°.

[0133] The inlet angle β1 of the flow channel is controlled by the flow channel wrap angle α and the outlet angle β2 of the flow channel, and the range is 75° to 85°.

[0134] The inlet and outlet cross-sectional parameters of the flow channels include the number of flow channels, the inlet area of ​​the flow channels, and the outlet area of ​​the flow channels, which are specifically determined as follows: The number of flow channels Z0 is determined by the following formula:

[0135]

[0136] Where: K is a coefficient, the value of which varies depending on the material, and K is taken as 6.0 to 8.5;

[0137] D2 is the impeller outlet diameter, in meters;

[0138] D j Where is the impeller inlet diameter, in meters (m).

[0139] α is the flow channel wrap angle;

[0140] Let the inlet area of ​​the flow channel be A1 and the outlet area be A2. The inlet area A1 of the flow channel between the two blades is determined by the following formula:

[0141]

[0142] Where: r3 is the distance from the inlet edge to the axis of the flow channel, in meters;

[0143] b1 is the blade inlet width, in meters;

[0144] ψ1 represents the flow channel area utilization rate;

[0145] Z0 represents the number of flow channels;

[0146] Based on the ratio of the inlet and outlet areas of the flow channel The outlet area of ​​the flow channel is determined to be A2;

[0147] The outlet cross-section of the flow channel is elliptical, with the major semi-axis of the elliptical cross-section being a1 and the minor semi-axis being a2.

[0148] A2=a1a2π

[0149] The minor semi-axis a2 of the elliptical cross-section at the flow channel outlet should be approximately equal to the distance c2 between the front and rear shrouds of the impeller. The distance c2 between the front and rear shrouds of the impeller is determined by the following formula:

[0150]

[0151] Where: k b This is a correction factor, with a value range of k. b =1.09~1.152, when n s When k is large, b Take the smaller value; when n s When k is small b Take the larger value; that is, when n s When the value is close to 30, then k bTake the lower limit value (such as a value near 1.09), and similarly, when n... s The further μ deviates from 30, the better. d Take the upper limit value.

[0152] Q n For normal working flow, m 3 / s;

[0153] n is the pump speed, in r / min.

[0154] A horizontal straight line is introduced at the inlet of the flow channel. The length of the straight line, d1, is determined by the following formula:

[0155] d1=(0.7~0.9)D j

[0156] Where: D j Let be the impeller inlet diameter, in meters (m).

[0157] In this embodiment, the two ends of the curve are determined by the inlet and outlet sections of the flow channel. Four transition sections are set between the inlet and outlet of the flow channel, and a circular arc curve is used to connect the inlet section, transition sections, and outlet section of the flow channel to determine the flow channel direction and shape. Figure 2 As shown in the figure, a, b, c, and d represent four cross sections.

[0158] The specific direction of the flow channel is determined as follows:

[0159] A circular arc curve is used to connect the inlet and outlet sections of the flow channel to initially determine the flow channel direction;

[0160] Using the plane perpendicular to the inlet and outlet cross-sections of the flow channel and containing the center points of the inlet and outlet cross-sections as the reference plane, and with the hub as the center, the spacing between the inlet and outlet of the flow channel is... Draw four concentric circles, and mark the intersection points of the concentric circles and the arc curves. These intersection points will be the centers of the transition sections. In the formula: D2 is the impeller outlet diameter; r3 is the distance from the inlet edge of the flow channel to the axis.

[0161] Overlap the center of the flow channel inlet section with the center of the flow channel outlet section, and draw the diagonal of the flow channel inlet section to intersect the flow channel outlet section. Simultaneously, draw the major and minor axes of the flow channel outlet section to intersect the flow channel inlet section. Figure 5 As shown; divide the eight intersection lines into four equal parts, and connect the corresponding points with a fitted curve to determine the shape of each transition section, as shown. Figure 3 As shown, circular arc curves are used to connect the inlet section, transition section, and outlet section of the flow channel to determine the flow channel direction and shape.

[0162] Figure 6 and Figure 7 This invention relates to the fluid distribution of the internal liquid in the impeller of the present invention and a conventional impeller of the same model under high flow conditions, such as... Figure 6 As shown, traditional impellers generate significant fluid turbulence and vortices after entering the space between the blades, resulting in a significant decrease in their flow capacity. For example... Figure 7 As shown, the impeller fluid distribution in this embodiment of the invention is smooth with no obvious vortices, resulting in better flow capacity, reduced occurrence of undesirable flow patterns, and increased working efficiency of the centrifugal pump.

[0163] A low specific speed centrifugal pump, wherein the flow channel is designed using the aforementioned low specific speed centrifugal pump flow channel design method.

[0164] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0165] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for designing the flow channel of a low specific speed centrifugal pump, characterized in that, Includes the following steps: Based on the rated flow rate of the low specific speed centrifugal pump Rated head Given the rated speed n, determine the inlet and outlet parameters of the flow channel, which include the impeller inlet and outlet diameters, the inner and outer fillets of the flow channel, the flow channel wrap angle, the inlet and outlet angles of the flow channel, and the inlet and outlet cross-sectional parameters of the flow channel; The two ends of the curve are determined by the inlet and outlet sections of the flow channel. At least four transition sections are set between the inlet and outlet of the flow channel. The flow channel direction and shape are determined by connecting the inlet section, transition section and outlet section with a circular arc curve, including the following steps: A circular arc curve is used to connect the inlet and outlet sections of the flow channel to initially determine the flow channel direction; Using the plane perpendicular to the inlet and outlet cross-sections of the flow channel and containing the center points of the inlet and outlet cross-sections as the reference plane, and with the hub as the center, the spacing between the inlet and outlet of the flow channel is... Draw at least four concentric circles, and mark the intersection points of each concentric circle and the arc curve. These intersection points will be the centers of the transition section. Where: The impeller outlet diameter; This is the distance from the edge of the flow channel to the axis. Overlap the center of the inlet section of the flow channel with the center of the outlet section of the flow channel, and draw the diagonal of the inlet section of the flow channel to intersect the outlet section of the flow channel. At the same time, draw the major and minor axes of the outlet section of the flow channel to intersect the inlet section of the flow channel. Divide the eight intersection lines into four equal parts, and use a fitted curve to connect the corresponding equal parts to determine the shape of each transition section. Use a circular arc curve to connect the inlet section, transition section and outlet section of the flow channel to determine the flow channel direction and shape.

2. The flow channel design method for a low specific speed centrifugal pump according to claim 1, characterized in that, Based on the rated flow rate of the low specific speed centrifugal pump Rated head Given the rated speed n, determine the impeller inlet and outlet diameters as follows: Impeller inlet diameter Determined by the following formula: , in: The equivalent diameter of the impeller inlet. ; ; For coefficients, ; For rated flow rate, ; For pump speed, ; The diameter of the wheel hub. ; Where is the impeller inlet diameter, in meters (m). Impeller outlet diameter Determine using the following formula: , in: Impeller outlet diameter Correction factor, when At that time, take ,when When the value is large, take the smaller value. Take the larger value when it is smaller; For specific speed, ; The impeller outlet diameter is .

3. The flow channel design method for a low specific speed centrifugal pump according to claim 2, characterized in that, Based on the impeller inlet diameter of the low specific speed centrifugal pump Impeller outlet diameter and hub diameter Determine the fillets on the inner and outer sides of the flow channel, specifically as follows: inner corner of the flow channel The range value can be determined by the following formula and then rounded down: , in: As the correction factor, take ; The impeller outlet diameter is ; The impeller inlet diameter is ; The diameter of the wheel hub. ; Rounded corners on the outer side of the flow channel The range value can be determined by the following formula and then rounded down: , in: As the correction factor, take ; The impeller inlet diameter is ; The diameter of the wheel hub. ; The distance from the inlet edge to the axis of the flow channel. Determine using the following formula: , in: for Correction factor, take ; The inner corner of the flow channel is rounded. .

4. The flow channel design method for a low specific speed centrifugal pump according to claim 2, characterized in that, Based on the impeller outlet diameter of the low specific speed centrifugal pump Distance between the inlet edge and the axis of the flow channel Determine the flow channel wrap angle and the flow channel inlet / outlet angle, specifically as follows: Flow channel corner Calculate using the following formula: , in: The impeller outlet diameter is ; The distance from the inlet edge to the axis of the flow channel. ; Flow channel outlet angle The range is ; Flow channel inlet angle By flow channel corner and flow channel outlet angle Control, range is .

5. The flow channel design method for a low specific speed centrifugal pump according to claim 2, characterized in that, The inlet and outlet cross-sectional parameters of the flow channel include the number of flow channels, the inlet area of ​​the flow channel, and the outlet area of ​​the flow channel, which are specifically determined as follows: The number of flow channels Z0 is determined by the following formula: , in: Let be the coefficient, and take . ; Where is the impeller outlet diameter, in meters (m). Where is the impeller inlet diameter, in meters (m). For the flow channel wrap angle; Let the inlet area of ​​the flow channel be A1 and the outlet area be A2. The inlet area A1 of the flow channel between the two blades is determined by the following formula: , in: The distance from the inlet edge to the axis of the flow channel is in meters (m). Where is the blade inlet width, in meters; For the utilization rate of the flow channel area; The number of flow channels; Based on the ratio of the inlet and outlet areas of the flow channel The outlet area of ​​the flow channel is determined to be A2; The outlet cross-section of the flow channel is an elliptical cross-section, and the major semi-axis of the elliptical cross-section is... The minor semi-axis of the elliptical cross-section is , , The short semi-axis of the elliptical cross-section at the outlet of the flow channel The distance between the front and rear cover plates of the impeller should meet the requirements. Approximately equal, the distance between the front and rear cover plates of the impeller Determined by the following formula: , in: This is a correction factor, and its value range is... ,when When it is large, Take the smaller value; when When smaller, Take the larger value; Normal working traffic, ; For pump speed, .

6. The flow channel design method for a low specific speed centrifugal pump according to claim 2, characterized in that, A horizontal straight line is introduced at the inlet of the flow channel, the length of which is... It is determined by the following formula: , in: The impeller inlet diameter is .

7. A low specific speed centrifugal pump, characterized in that, The flow channel is designed using the flow channel design method for low specific speed centrifugal pumps according to any one of claims 1-6.

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