An optimization design method of high specific speed vertical single-stage single-suction centrifugal pump

Abstract

The application relates to an optimization design method of a high-specific-speed vertical single-stage single-suction centrifugal pump, which comprises the following optimization steps: step 1, optimizing an elbow type suction chamber and an impeller inlet; step 2, optimizing a volute pressure outlet chamber; and step 3, optimizing an impeller outlet edge. When the lift is not affected, the overall efficiency of the pump is improved, the pump high-efficiency point is calibrated near the rated working condition, and the cavitation and hydraulic performance in the large-flow area are greatly improved, so that the high-efficiency area is widened, the pump power is overall reduced, and considerable economic benefits are achieved, which is more favorable for long-term stable operation of the water pump.

Description

Technical Field

[0001] This invention relates to a design method for a vertical single-stage single-suction centrifugal pump, specifically an optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump that can achieve higher efficiency, a wider high-efficiency range, better cavitation performance, more stable unit operation, and better overall performance. Background Technology

[0002] Vertical single-stage single-suction centrifugal pumps are compact in structure and low in cost, require little maintenance space, are easy to install in pipelines, and operate smoothly. However, they often lack advantages in efficiency and cavitation performance. Among them, those with higher specific speeds (n) are more commonly used. s High specific speed products (150-300) generally have average efficiency, and occasionally pump cavitation can cause abnormal noise and vibration.

[0003] Considering energy conservation, emission reduction, and improved stability to enhance product market competitiveness, optimizing the hydraulic and cavitation performance of current high specific speed vertical single-stage single-suction centrifugal pumps is of significant practical importance. This involves improving efficiency, expanding the high-efficiency range, and enhancing cavitation performance to ensure pump operation stability while improving economic benefits.

[0004] For a representative high specific speed vertical single-stage single-suction centrifugal pump, because the prototype was designed using traditional methods and excessively focused on parts commonality in pursuit of cost reduction, the internal flow channel of the impeller was not well-formed. Currently, the rated efficiency is average, and the efficiency is even lower at high flow rates. Abnormal vibration and noise caused by cavitation often occur, specifically: (1) The diameter of the impeller inlet is often too small at the outlet of the suction chamber, resulting in poor flow at the impeller inlet; the suction chamber adopts the traditional rectangular shape with large rounded corners to save casting costs, resulting in large friction loss; the axial flow line of the suction chamber is not smooth, and the local loss of the inlet and outlet bends is large; these factors affect the smoothness of the flow entering the impeller inlet, increase the energy loss in the flow channel before the blade inlet, and are not conducive to ensuring the hydraulic performance and cavitation performance of the pump.

[0005] (2) The flow cross section of the discharge chamber volute is trapezoidal, resulting in large friction loss. The important parameters affecting the matching relationship between the volute and the impeller are not properly controlled, resulting in poor matching between the impeller and the volute. The high efficiency point is too low for the pump operating condition, and the pump often experiences cavitation under high flow conditions, causing a sharp drop in performance in the high flow range.

[0006] (3) The impeller inlet diameter is too small and the inlet displacement is too large, which further reduces the energy loss in the flow channel before the blade inlet and affects the impeller cavitation performance; the impeller efficiency is mediocre and needs to be optimized.

[0007] We will use this as a basis to optimize and improve its hydraulic and cavitation performance in order to upgrade the product's performance. Summary of the Invention

[0008] The present invention solves the above-mentioned technical problems through the following technical solution: It proposes an optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump, wherein the optimized design method for the high specific speed vertical single-stage single-suction centrifugal pump includes: A. Optimize the elbow-type suction chamber and impeller inlet: First, optimize the high specific speed centrifugal pump coefficient K0, and then determine the impeller inlet diameter D. j The diameter of the inhalation chamber outlet, D s2 With D j Equal. The inlet diameter D of the inhalation chamber is... s1 The values ​​are the same as the design requirements for the pump inlet diameter. Determine the cross-sectional shape of the suction chamber, and select the suction chamber outlet contraction angle x and the equivalent outlet cross-sectional diameter D. x3 The preferred bending radius R of the intake chamber outlet s2 R s2 ' and the bending radius R of the inlet of the inhalation chamber s1 R s1 'Equivalent diameter D of the inlet elbow cross section x1 and the equivalent diameter D of the outlet elbow section x2 The contraction ratio P of the middle section of the inhalation chamber is obtained. The center distance Hx of the middle section is determined by controlling the equivalent contraction angle θs of the middle section, and the value of H1 is made to be an integer multiple of 5.

[0009] B. Optimize the volute discharge chamber: While maintaining a constant flow area, control the shape of the flow cross-section of the pump body to reduce the wetted perimeter. Adjust the matching degree between the pump body and impeller by controlling the ratio of the base circle diameter to the impeller outer diameter (D3 / D2) and the ratio of the volute inlet width to the blade width (b3 / b2). This aims to ensure the pump body and impeller are matched to achieve the highest efficiency point between 1.0 and 1.05Q. n (Q) n (for rated flow conditions), thus ensuring the widened high-efficiency range is maintained at 0.75Q. n ~1.2Q n between.

[0010] C. Optimize the impeller outlet edge: While keeping the impeller outer diameter D2, blade outlet width b2, number of blades Z, blade inlet angle β1, and blade outlet angle β2 constant, optimize the impeller axial surface shape by adjusting the impeller blade outlet edge angle α3, impeller inlet Dj, and the streamline shape of the front and rear shrouds, thereby increasing the minimum flow area F at the blade inlet. i This reduces the impeller flow channel diffusion ratio.

[0011] In a specific embodiment of the present invention, optimization point A is specifically as follows: 1. When optimizing the elbow-type suction chamber and impeller inlet, first select the high specific speed centrifugal pump coefficient K0, and then determine the impeller inlet diameter D. j Then D s2Values ​​and D j The same result is acceptable; the relevant calculations are as follows: (1) D s2 —Diameter of the inhalation chamber outlet, unit: mm; D j —Impeller inlet diameter, unit: mm; D0—Equivalent impeller inlet diameter, unit: mm; D h —Impeller hub diameter, unit: mm; K0—Optimal coefficient for impeller inlet diameter of high specific speed centrifugal pump, with a value range of 4.25 to 4.45; Q—Design flow rate of the water pump, unit: m³ / h 3 / s; n—Pump speed, unit: r / min; 2. Inlet diameter D of the inhalation chamber s1 The value is the same as the design requirement for the pump inlet diameter. To minimize the wetted perimeter, the suction cross-section is changed from a large rounded rectangle to a circle, effectively reducing friction loss.

[0012] 3. Determine the outlet edge position based on the vertical distance Hj from the outlet edge of the suction chamber to the center plane of the flow channel, and select the outlet contraction angle x of the suction chamber (x ranges from 10° to 14° for high specific speed centrifugal pumps). Based on D... s2 Take the equivalent diameter D of the outlet section with x. x3 (Rounded down and the value is slightly greater than D) s2 ).

[0013] 4. Optimize the internal streamline bending radius R of the outlet elbow on the axial surface of the suction chamber. s2 The value ranges from 25% to 35% D s1 And not less than 25mm; the bending radius R of the outer streamline of the outlet elbow s2 '= R s2 + D x3 Furthermore, the inner and outer streamlines are concentric at this point, and the vertical distances from the center of the circle to the center plane of the flow channel, Hs2 and Hj, are close, with a difference of less than 5%. The horizontal distances from the center of the circle to the edge of the suction chamber outlet, Js2 and R, are also close. s2 Close, with a difference within 2%. Equivalent diameter D of the outlet elbow cross-section. x2 =D x3 .

[0014] 5. The radius of curvature R of the streamline of the inlet elbow on the axial surface of the suction chamber s1 The value ranges from 45% to 65% D s1 And not less than 50mm; the bending radius R of the outer streamline of the imported elbow s1 '= Rs1 + D s1 Furthermore, the inner and outer streamlines are concentric at this point, with the center located on the inlet surface of the suction chamber. The equivalent diameter D of the inlet elbow cross-section... x1 = D s1 .

[0015] 6. Control θ s Determine H x And the center distance H1 from the inlet of the inhalation chamber is an integer multiple of 5. The specific calculations are as follows: (2) H x —Center-to-center distance of the intermediate section, unit: mm; θ s —Equivalent contraction angle of the middle section of the suction chamber of a high specific speed centrifugal pump, with a value range of 6.5 to 11.5°; In a specific embodiment of the present invention, optimization point B is as follows: 1. The pump body controls the shape of the flow cross section of the volute discharge chamber to reduce the wetted perimeter, optimizing the flow cross section of the volute from a trapezoid to a circle; 2. Control the theoretical base circle diameter D3 of the volute so that its ratio D3 / D2 to the impeller outer diameter is within the range of 1.05 to 1.07. Specifically, this is achieved by calculating the volute diameter D3 using the following formula: (3) n s —Specific speed of the water pump, ; H – Pump design head, unit: m.

[0016] D2—Impeller diameter, unit: mm; k D2 —The D2 correction factor for high specific speed centrifugal pumps is determined based on the specific speed, with a value range of 0.997 to 1.022; k D3 —Optimal coefficient for the theoretical base circle of the volute casing of a high specific speed centrifugal pump, with a value range of 10.06 to 10.25; 3. Control the inlet width b3 of the volute chamber so that its ratio b3 / b2 to the blade width is within the range of 1.6 to 2.0. Specifically, this is achieved by calculating b3 in the volute casing using the following formula: (4) K b2 — Correction factor b2 for high specific speed centrifugal pumps, which is determined based on the specific speed and ranges from 0.965 to 0.767; K b3 —Optimal coefficient for the inlet width of the volute of a high specific speed centrifugal pump, with a value range of 1.18 to 1.48; The pump body controls the shape of the flow cross-section of the volute discharge chamber, controls the theoretical base circle diameter D3 of the volute, and controls the inlet width b3 of the volute chamber. These factors together adjust the matching degree between the pump body and the impeller, ensuring that the pump body and impeller are matched to achieve the highest efficiency point between 1.0 and 1.05Q. n This ensures that the high-efficiency region is widened within 0.75Q. n ~1.2Q n between.

[0017] In a specific embodiment of the present invention, optimization point C is specifically as follows: With impeller outer diameter D2, blade outlet width b2, number of blades Z, blade inlet angle β1, and blade outlet angle β2 remaining constant, the impeller axial surface shape is optimized by adjusting the impeller blade outlet slope angle α3, impeller inlet Dj, and the streamline shape of the front and rear shrouds, thereby increasing the minimum flow area F at the blade inlet. j This also reduces the diffusion ratio between the inlet and outlet channels of the blades. Specifically: 1. Adjust the blade α3 to control the streamline of the front and rear cover plates of the impeller shaft, ensuring that the rear cover plate streamline is not excessively long relative to the front cover plate. This facilitates blade design and improves hydraulic efficiency. Simultaneously, the blade outlet edge is inclined, and the angle between it and the tongue edge on the same axial plane is also α3. This reduces dynamic and static interference between the blade and the tongue, thereby reducing pressure pulsation, improving hydraulic performance, and reducing vibration and noise. Specifically, α3 and n... s The correspondence is shown in Table 1.

[0018] Table 1 α3 and n s Correspondence table

[0019] 2. Combined with D obtained through calculation or optimization j And α3, optimize the streamlines of the front and rear cover plates of the impeller.

[0020] The inlet angle α1 of the impeller shaft surface streamline is controlled to be approximately 0° (i.e., horizontal), while the outlet angle α2 of the impeller shaft surface streamline is controlled to be approximately 86–90°, thereby controlling the radius of curvature R. q Greater than 25mm, radius of curvature R h Greater than 55mm, ultimately increasing the minimum flow area F at the blade inlet. i Simultaneously control the diffusion ratio P between the inlet and outlet channels of the blades. 叶 Between 1.2 and 1.3.

[0021] The positive and progressive effects of this invention are as follows: Compared with the design of traditional prototypes, the optimized design method for high specific speed vertical single-stage single-suction centrifugal pumps provided by this invention has the following advantages: (1) The coefficient K0 of the high specific speed centrifugal pump was optimized, and the impeller inlet diameter D was reasonably increased. jThe diameter of the inhalation chamber outlet, D s2 With D j The flow rate increases uniformly, reducing the outlet velocity of the suction chamber and improving the flow pattern at the impeller inlet; (2) The cross-section of the suction chamber was changed from a rectangular shape with large rounded corners to a circle, resulting in a smaller wetted perimeter and effectively reducing the friction loss along the flow path of the suction chamber; (3) The axial structure of the suction chamber was optimized, and a contraction section at the outlet of the suction chamber was designed. The outlet contraction angle made the outflow from the suction chamber more concentrated and stable into the impeller inlet, thus improving the inlet flow pattern. The two bends at the inlet and outlet of the suction chamber were designed with equal cross sections, and the linear contraction of the cross-sectional area of ​​the water passage was designed to occur in the middle straight cone section. The loss in the middle contraction section was controlled by controlling the equivalent contraction angle θs of the middle section, which effectively reduced the local loss of the suction chamber. The axial streamline of the suction chamber was optimized, and the streamline was smooth. These features made the cross-sectional area of ​​the water passage from the inlet to the outlet of the suction chamber increase gradually, and the flow into the impeller inlet was stable, reducing the energy loss in the flow channel before the blade inlet, which is conducive to improving hydraulic performance and cavitation performance.

[0022] (4) Under the premise that the flow area remains unchanged, the cross-sectional shape of the volute is changed from trapezoid to circle, which reduces the wetted perimeter and reduces the friction loss along the volute.

[0023] (5) D3 and b3 were optimized by calculation using optimization methods. The matching degree between the pump body and the impeller was adjusted by reasonably controlling D3 / D2 and b3 / b2 to correct the shift of the high efficiency point to the low flow rate condition, so that the pump's highest efficiency point is between 1.0 and 1.05Q. n Nearby, and the high-efficiency zone is widened at 0.75Q. n ~1.2Q n This improved the overall efficiency of the pump and solved the problem of sharp performance drop under high flow conditions.

[0024] (6) The new design method optimizes the impeller inlet D j Under the premise of [specific conditions], by adjusting the impeller blade outlet edge angle α3 and the streamline shape of the front and rear cover plates, the impeller axial surface shape is optimized, increasing the minimum flow area at the blade inlet and reducing the impeller channel diffusion ratio. This reduces blade inlet displacement, further reducing energy loss in the flow channel before the blade inlet and improving cavitation performance. Simultaneously, it reduces impeller channel diffusion, improves the flow pattern in the inter-blade channel, and enhances the impeller's hydraulic performance.

[0025] (7) The blade outlet edge is inclined, and the angle between it and the tongue edge on the same axial plane is also α3, so as to reduce the dynamic and static interference between the blade and the tongue, thereby reducing pressure pulsation, improving hydraulic performance, and reducing vibration and noise. In this way, the overall efficiency of the pump is improved while improving cavitation performance, and vibration and noise during pump operation are reduced, ultimately improving the overall quality of the pump.

[0026] (8) Under the same head, as the overall efficiency of the pump increases, the power can be reduced as a whole, which effectively saves energy and is more conducive to the long-term stable operation of the pump. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of an impeller designed using the method of the present invention.

[0028] Figure 2 This is an assembly drawing designed using the method of the present invention.

[0029] Figure 3-1 This is a schematic diagram of the volute's outline.

[0030] Figure 3-2 This is an axial view of the inhalation chamber.

[0031] Figure 3-3 This is one of the schematic diagrams of a volute cross-section.

[0032] Figure 3-4 This is the second schematic diagram of the volute cross-section.

[0033] Figure 4 This is a graph comparing prototype test data with the test data of this invention.

[0034] Figure 5 This is the assembly drawing of the product prototype. Detailed Implementation

[0035] The preferred embodiments of the present invention are given below with reference to the accompanying drawings to illustrate the technical solution of the present invention in detail.

[0036] Figure 1 This is a cross-sectional view of the impeller designed using the method of the present invention. Figure 2 The assembly drawing designed using the method of this invention is as follows. Figure 3-1 This is a schematic diagram of the volute's outline. Figure 3-2 This is an axial view of the inhalation chamber. Figure 3-3 This is one of the schematic diagrams of a volute cross-section. Figure 3-4 This is the second schematic diagram of the volute cross-section. Figure 4 The figure above shows a comparison curve between prototype test data and the test data of this invention. As shown in the figure, this invention proposes an optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump, which includes: A. Optimize the elbow-type suction chamber and impeller inlet: First, optimize the high specific speed centrifugal pump coefficient K0, and then determine the impeller inlet diameter D. j The diameter of the inhalation chamber outlet, D s2 With D j Equal. The inlet diameter D of the inhalation chamber is... s1 The values ​​are the same as the design requirements for the pump inlet diameter. Determine the cross-sectional shape of the suction chamber, and select the suction chamber outlet contraction angle x and the equivalent outlet cross-sectional diameter D.x3 The preferred bending radius R of the intake chamber outlet s2 R s2 ' and the bending radius R of the inlet of the inhalation chamber s1 R s1 'Equivalent diameter D of the inlet elbow cross section x1 and the equivalent diameter D of the outlet elbow section x2 The contraction ratio P of the middle section of the suction chamber is obtained. The center distance Hx of the middle section is determined by controlling the equivalent contraction angle θs of the middle section, and the value of H1 is taken as an integer multiple of 5. The water passage section of the suction chamber is designed as a circle, with a smaller wetted perimeter, which effectively reduces the friction loss along the flow channel. Moreover, the linear contraction of the water passage section area of ​​the suction chamber occurs in the straight pipe section, and the inlet and outlet elbows are of equal cross-section, which effectively reduces local losses. The outlet diameter of the suction chamber is optimized based on the impeller inlet diameter, and the streamline of the suction chamber axis is smoother after optimization, which improves the flow state at the impeller inlet and is conducive to the improvement of hydraulic performance and cavitation performance.

[0037] B. Optimize the volute discharge chamber: While maintaining a constant flow area, control the shape of the flow cross-section of the pump body to reduce the wetted perimeter. Adjust the matching degree between the pump body and impeller by controlling the ratio of the base circle diameter to the impeller outer diameter (D3 / D2) and the ratio of the volute inlet width to the blade width (b3 / b2). This aims to ensure the pump body and impeller are matched to achieve the highest efficiency point between 1.0 and 1.05Q. n (Q) n (for rated flow conditions), thus ensuring the widened high-efficiency range is maintained at 0.75Q. n ~1.2Q n Meanwhile, the discharge chamber has a circular cross-section, resulting in a smaller wetted perimeter, effectively reducing flow path losses and further improving the overall pump efficiency.

[0038] C. Optimize the impeller outlet edge: While keeping the impeller outer diameter D2, blade outlet width b2, number of blades Z, blade inlet angle β1, and blade outlet angle β2 constant, optimize the impeller axial surface shape by adjusting the impeller blade outlet edge angle α3, impeller inlet Dj, and the streamline shape of the front and rear shrouds, thereby increasing the minimum flow area F at the blade inlet. i This reduces the impeller channel diffusion ratio. Consequently, the blade outlet edge is tilted, and the angle between it and the tongue edge on the same axial plane is also α3, reducing dynamic and static interference between the blade and the tongue, thereby reducing pressure pulsation, improving hydraulic performance, and reducing vibration and noise. The minimum flow area F at the blade inlet is increased. i This reduces the impeller flow channel diffusion ratio, improving both cavitation performance and impeller efficiency, thereby enhancing the overall pump performance.

[0039] Specifically, the steps include the following: Step (1): 1. When optimizing the elbow-type suction chamber and impeller inlet, first select the high specific speed centrifugal pump coefficient K0, and then determine the impeller inlet diameter D. j Then D s2 Values ​​and D j The same result is acceptable; the relevant calculations are as follows: (1) D s2 —Diameter of the inhalation chamber outlet, unit: mm; D j —Impeller inlet diameter, unit: mm; D0—Equivalent impeller inlet diameter, unit: mm; D h —Impeller hub diameter, unit: mm; K0—Optimal coefficient for impeller inlet diameter of high specific speed centrifugal pump, with a value range of 4.25 to 4.45; Q—Design flow rate of the water pump, unit: m³ / h 3 / s; n—Pump speed, unit: r / min; 2. Inlet diameter D of the inhalation chamber s1 The value is the same as the design requirement for the pump inlet diameter. To minimize the wetted perimeter, the suction cross-section is changed from a large rounded rectangle to a circle, effectively reducing friction loss.

[0040] 3. Determine the outlet edge position based on the vertical distance Hj from the outlet edge of the suction chamber to the center plane of the flow channel, and select the outlet contraction angle x of the suction chamber (x ranges from 10° to 14° for high specific speed centrifugal pumps). Based on D... s2 Take the equivalent diameter D of the outlet section with x. x3 (Rounded down and the value is slightly greater than D) s2 ).

[0041] 4. Optimize the internal streamline bending radius R of the outlet elbow on the axial surface of the suction chamber. s2 The value ranges from 25% to 35% D s1 And not less than 25mm; the bending radius R of the outer streamline of the outlet elbow s2 '= R s2 + D x3 Furthermore, the inner and outer streamlines are concentric at this point, and the vertical distances from the center of the circle to the center plane of the flow channel, Hs2 and Hj, are close, with a difference of less than 5%. The horizontal distances from the center of the circle to the edge of the suction chamber outlet, Js2 and R, are also close. s2 Close, with a difference within 2%. Equivalent diameter D of the outlet elbow cross-section. x2 =D x3 .

[0042] 5. The radius of curvature R of the streamline of the inlet elbow on the axial surface of the suction chambers1 The value ranges from 45% to 65% D s1 And not less than 50mm; the bending radius R of the outer streamline of the imported elbow s1 '= R s1 + D s1 Furthermore, the inner and outer streamlines are concentric at this point, with the center located on the inlet surface of the suction chamber. The equivalent diameter D of the inlet elbow cross-section... x1 = D s1 .

[0043] 6. Control θ s Determine H x And the center distance H1 from the inlet of the inhalation chamber is an integer multiple of 5. The specific calculations are as follows: (2) H x —Center-to-center distance of the intermediate section, unit: mm; θ s —Equivalent contraction angle of the middle section of the suction chamber of a high specific speed centrifugal pump, with a value range of 6.5 to 11.5°; See impeller details Figure 1 (Cross-sectional view of the impeller designed using the method of this invention). See details of the suction chamber. Figure 3-2 Axial view of the inhalation chamber.

[0044] Step (2): 1. The pump body controls the shape of the flow cross section of the volute discharge chamber to reduce the wetted perimeter, optimizing the flow cross section of the volute from a trapezoid to a circle; 2. Control the theoretical base circle diameter D3 of the volute so that its ratio D3 / D2 to the impeller outer diameter is within the range of 1.05 to 1.07. Specifically, this is achieved by calculating the volute diameter D3 using the following formula: (3) n s —Specific speed of the water pump, ; H – Pump design head, unit: m.

[0045] D2—Impeller diameter, unit: mm; k D2 —The D2 correction factor for high specific speed centrifugal pumps is determined based on the specific speed, with a value range of 0.997 to 1.022; k D3 —Optimal coefficient for the theoretical base circle of the volute casing of a high specific speed centrifugal pump, with a value range of 10.06 to 10.25; 3. Control the inlet width b3 of the volute chamber so that its ratio b3 / b2 to the blade width is within the range of 1.6 to 2.0. Specifically, this is achieved by calculating b3 in the volute casing using the following formula: (4) K b2 — Correction factor b2 for high specific speed centrifugal pumps, which is determined based on the specific speed and ranges from 0.965 to 0.767; K b3 —Optimal coefficient for the inlet width of the volute of a high specific speed centrifugal pump, with a value range of 1.18 to 1.48; The pump body controls the shape of the flow cross-section of the volute discharge chamber, controls the theoretical base circle diameter D3 of the volute, and controls the inlet width b3 of the volute chamber. These factors together adjust the matching degree between the pump body and the impeller, ensuring that the pump body and impeller are matched to achieve the highest efficiency point between 1.0 and 1.05Q. n This ensures that the high-efficiency region is widened within 0.75Q. n ~1.2Q n between.

[0046] See details of the discharge chamber Figure 3-1 (Schematic diagram of the volute shell outline) Figure 3-3 (One of the schematic diagrams of the volute cross-section) Figure 3-4 (Second schematic diagram of the volute cross section).

[0047] Step (3): Under the premise that the impeller outer diameter D2, blade outlet width b2, number of blades Z, blade inlet installation angle β1, and blade outlet installation angle β2 remain unchanged, optimize the impeller axial surface shape by adjusting the impeller blade outlet side slope angle α3, impeller inlet Dj, and the streamline shape of the front and rear cover plates, and increase the minimum flow area F at the blade inlet. j This also reduces the diffusion ratio between the inlet and outlet channels of the blades. Specifically: 1. Adjust the blade α3 to control the streamline of the front and rear cover plates of the impeller shaft, ensuring that the rear cover plate streamline is not excessively long relative to the front cover plate. This facilitates blade design and improves hydraulic efficiency. Simultaneously, the blade outlet edge is inclined, and the angle between it and the tongue edge on the same axial plane is also α3. This reduces dynamic and static interference between the blade and the tongue, thereby reducing pressure pulsation, improving hydraulic performance, and reducing vibration and noise. Specifically, α3 and n... s The correspondence is shown in Table 1.

[0048] Table 1 α3 and n s Correspondence table

[0049] 2. Combined with D obtained through calculation or optimization j And α3, optimize the streamlines of the front and rear cover plates of the impeller.

[0050] The inlet angle α1 of the impeller shaft surface streamline is controlled to be approximately 0° (i.e., horizontal), while the outlet angle α2 of the impeller shaft surface streamline is controlled to be approximately 86–90°, thereby controlling the radius of curvature R. q Greater than 25mm, radius of curvature Rh Greater than 55mm, ultimately increasing the minimum flow area F at the blade inlet. i Simultaneously control the diffusion ratio P between the inlet and outlet channels of the blades. 叶 Between 1.2 and 1.3.

[0051] See impeller details Figure 1 (Cross-sectional view of the impeller designed using the method of the present invention).

[0052] The following is a specific embodiment of the optimization design method provided by the present invention: Taking an existing vertical single-stage single-suction centrifugal pump with a specific speed of 240.8 as the design object, the existing product is optimized and modified. The design flow rate of the existing product is Q=160m³ / h. 3 / h, design head H=20m (tolerance factor 0~+8%), speed n=2960r / min, power P=15kw, pump inlet and outlet diameter D s1 =D d =125mm, and proposed a wide and efficient range optimization design requirement: low flow rate condition (0.75Q) n Efficiency 76%, rated operating condition (1.0Q) n Efficiency 81% (η) Qn High flow rate conditions (1.2Q) n Efficiency: 76.4%.

[0053] 1. Determine the impeller inlet diameter D j and the diameter D of the inhalation chamber outlet s2 : First, select K0 = 4.355 (value range 4.25~4.45), D h =14mm, substituting into formula (1): =107.4mm; =108.3mm.

[0054] 2. Determine the inlet diameter D of the inhalation chamber. s1 And the cross-sectional shape of the water passage in the suction chamber: D s1 = D d =125mm, the water passage cross-section shape of the suction chamber was changed from a large rounded rectangle to a circle.

[0055] 3. Based on the vertical distance Hj = 52mm from the center plane of the flow channel at the outlet edge of the suction chamber, determine the position of the outlet edge and select the outlet contraction angle of the suction chamber x = 12° (the value of x for high specific speed centrifugal pumps is 10~14°). According to D s2 Take the equivalent diameter D of the outlet section with x. x3=110mm (rounded down and the value is slightly greater than D) s2 ).

[0056] 4. Optimize the internal streamline bending radius R of the outlet elbow on the axial surface of the suction chamber. s2 =32%*125=40(mm) (Values ​​range from 25% to 35%) s1 ); Outlet elbow external flow line bending radius R s2 '= R s2 + D x3 =40+110=150(mm); Furthermore, the inner and outer streamlines are concentric at this point. The vertical distance from the center of the circle to the center plane of the flow channel is Hs2 = 50.5 mm, which is close to Hj, with a difference within 5%. The horizontal distance from the center of the circle to the edge of the suction chamber outlet is Js2 = 40.1 mm, which is similar to R. s2 Close, with a difference of less than 2%.

[0057] Equivalent diameter D of the outlet elbow section x2 = D x3 =110mm.

[0058] 5. The radius of curvature R of the streamline inside the inlet elbow of the suction chamber axial surface s1 =52%*125=65(mm) (Values ​​range from 45% to 65%D) s1 ); The outer flow curve of the imported elbow has a bending radius R. s1 '= R s1 + D s1 =65+125=190(mm); Furthermore, the inner and outer streamlines are concentric, with the center located on the inlet surface of the suction chamber.

[0059] Equivalent diameter D of imported elbow cross section x1 =D s1 =125mm.

[0060] 6. Optimize θ s =6.95° (range 6.5~11.5°), substitute into formula (2) to calculate back and determine the center distance H of the intermediate section. x =123.4mm. The relevant calculations are as follows: This results in the center distance of the inlet of the inhalation chamber being H1 = 325 mm (the value is taken as an integer multiple of 5).

[0061] The dimensions of the high-performance suction chamber for the high-specific-speed vertical single-stage single-suction centrifugal pump have been determined above. Please refer to the following for details. Figure 3-2 Axial view of the inhalation chamber.

[0062] 7. The pump body controls the shape of the flow cross section of the volute discharge chamber to reduce the wetted perimeter, optimizing the flow cross section of the volute from a trapezoid to a circle; 8. To control the theoretical base circle diameter D3 of the volute, first optimize the specific speed k. D2 =1.012 (range 0.997~1.022), k D3 =10.13 (value range 10.06~10.25), substitute into formula (3): =163mm The ratio of the base circle diameter to the impeller outer diameter is obtained as D3 / D2 = 1.058 (ranging from 1.05 to 1.07).

[0063] 9. Control the inlet width b3 of the vortex chamber, first optimize k based on the specific speed. b2 =0.831 (range 0.965~0.767), k b3 =1.33 (range 1.18~1.48), substitute into formula (4): =63mm.

[0064] The ratio of the vortex inlet width to the blade width was obtained as b3 / b2 = 1.8 (ranging from 1.6 to 2.0).

[0065] The pump body controls the flow cross-sectional shape of the volute discharge chamber to be circular, with the theoretical base circle diameter of the volute controlled at D3 = 163 mm, and the inlet width of the volute chamber controlled at b3 = 63 mm. This, in conjunction with other factors, adjusts the matching degree between the pump body and the impeller, ensuring the highest efficiency point is between 1.0 and 1.05Q. n Nearby, thus ensuring the widening of the high-efficiency zone is within 0.75Q. n ~1.2Q n between.

[0066] See details of the discharge chamber Figure 3-1 (Schematic diagram of the volute shell outline) Figure 3-3 (One of the schematic diagrams of the volute cross-section) Figure 3-4 (Second schematic diagram of the volute cross section).

[0067] 10. Refer to α3 and n s The corresponding relationship is shown in Table 1. Adjust the blade α3=2°.

[0068] 11. Combined with D obtained through calculation or optimization. j And α3, optimize the streamlines of the front and rear cover plates of the impeller.

[0069] By controlling the inlet angle α1 of the impeller shaft surface rear cover streamline to 0° (i.e., horizontal) and simultaneously controlling the outlet angle α2 of the rear cover streamline to 88°, the radius of curvature R is controlled. q =25.7mm, radius of curvature Rh =56.9mm, ultimately increasing the minimum flow area F at the blade inlet. i Simultaneously control the diffusion ratio P between the inlet and outlet channels of the blades. 叶 =1.258 (between 1.2 and 1.3).

[0070] The above describes how, under the premise that the impeller outer diameter D2, blade outlet width b2, number of blades Z, blade inlet angle β1, and blade outlet angle β2 remain unchanged, the impeller axial surface shape is optimized by adjusting α3, Dj, and the streamline shape of the front and rear cover plates, thereby increasing the minimum flow area F at the blade inlet. j This also reduces the diffusion ratio between the inlet and outlet channels of the blades.

[0071] For details, please refer to the following: Figure 1 (Cross-sectional view of the impeller designed using the method of the present invention).

[0072] Table 2 shows the test data for examples of the present invention.

[0073] Table 2 Figure 4 The curve in Table 2 compares the experimental data of this invention with the experimental data of existing prototypes. Figure 4 As can be seen: 1. The pump rated point (Q=160m) optimized by the method of this invention 3 The head change is minimal ( / h), with ample margin.

[0074] 2. The pump 0.75Q designed by the method of this invention n Efficiency is approximately 2.6% higher than existing designs, 1.0Q n Efficiency is approximately 4.5% higher than existing designs, 1.2Q n The efficiency is about 22.3% higher than that of existing products. There is no cavitation phenomenon during the current test. It solves the problem of cavitation accompanied by a sharp drop in performance in the high flow rate area. Moreover, the efficiency of all three operating points meets the new design requirements for a wide and high efficiency range, reaching the industry-leading level. In contrast, the existing prototype pump does not meet the efficiency value requirements of the wide and high efficiency range design and has cavitation problems in the high flow rate area.

[0075] 3. The highest efficiency point of the pump designed in this invention was adjusted to 1.05Q during numerical simulation. n Nearby, the highest efficiency point during testing was at 1.0Q. n Nearby, the effective high-efficiency zone expands to 0.75Q. n ~1.2Q n However, the highest efficiency point of the existing impeller is too low under low flow conditions, and the measured efficiency is not high according to the new design requirements, and the effective high efficiency zone is too narrow and does not meet the standards.

[0076] 4. The pump designed by the method of the present invention reduces the overall shaft power while meeting the performance requirements, with a 5% reduction in rated shaft power, which can generate considerable economic benefits.

[0077] 5. The pump optimized by the method of this invention improves cavitation performance, solves the problems of cavitation vibration and noise and sharp decline in hydraulic performance under high flow conditions, and is more conducive to the long-term stable operation of the pump.

[0078] Figure 2 The assembly drawing designed using the method of this invention is as follows. Figure 5 For the final assembly drawing of the product prototype, compare Figure 2 and 5 . Figure 2 Point A in the design optimizes the axial shape of the suction chamber, point B optimizes the flow cross-section of the volute and its matching parameters with the impeller, and point C optimizes the outlet edge and axial shape of the impeller. (Comparison) Figure 2 and Figure 5 It can be seen that: (1) The prototype pump referred to here adopts the traditional theoretical design. The diameter of the impeller inlet is too small at the outlet of the suction chamber. In order to save casting costs, the cross-section of the suction chamber adopts the traditional rectangular shape with large rounded corners, which leads to poor flow at the impeller inlet and directly affects the hydraulic and cavitation performance of the pump. In the optimization, the high specific speed centrifugal pump coefficient K0 is preferred, and the impeller inlet diameter D is increased. j The diameter of the inhalation chamber outlet, D s2 With D j They increased consistently.

[0079] The cross-section of the suction chamber was changed from a rectangular shape with large rounded corners to a circle, resulting in a smaller wetted perimeter and effectively reducing friction loss along the suction chamber flow path. The suction chamber outlet contraction angle x and the equivalent diameter D of the outlet cross-section were selected accordingly. x3 This design allows the outflow from the suction chamber to flow more concentratedly and stably into the impeller inlet, improving the inlet flow pattern. The two bends at the inlet and outlet of the suction chamber are designed with equal cross-sections, and the linear contraction of the water flow cross-sectional area occurs in the middle straight cone section. By controlling the equivalent contraction angle θs of the middle cross-section, the loss in the middle contraction section is reduced, effectively reducing the local loss of the suction chamber.

[0080] After optimization, the cross-sectional area of ​​the elbow-type suction inlet to outlet gradually increases, the streamline is smooth, the flow into the impeller inlet is stable, the energy loss in the flow channel in front of the blade inlet is reduced, the flow state at the impeller inlet is improved, which is conducive to improving hydraulic performance and cavitation performance.

[0081] (2) The prototype pump adopted a traditional design with a trapezoidal volute cross-section, resulting in large friction losses. The design of D3 and b3 was also unreasonable, leading to poor matching between the impeller and volute. The high-efficiency point was biased towards low-flow pump conditions. Under the influence of the suction chamber and impeller, cavitation ultimately occurred under high-flow conditions, causing a sharp drop in performance. The new design method, without changing the flow area, changed the pump body cross-section shape to a circle to reduce wetted perimeter and friction losses. Simultaneously, D3 and b3 were optimized through calculation, and the matching degree between the pump body and impeller was adjusted by reasonably controlling D3 / D2 and b3 / b2. This ensured that the highest efficiency point of the pump body and impeller matching control was at 1.0Q during testing. n Nearby, and the high-efficiency zone is widened at 0.75Q. n ~1.2Q n This solved the problem of sharp performance drop under high flow conditions.

[0082] (3) Under the premise that the impeller outer diameter D2, blade outlet width b2, number of blades Z, blade inlet installation angle β1, and blade outlet installation angle β2 remain unchanged, the new design method optimizes the impeller axial surface shape and increases the minimum flow area F at the blade inlet by adjusting the impeller blade outlet side slope angle α3, impeller inlet Dj, and the streamline shape of the front and rear cover plates. i This reduces the impeller flow channel diffusion ratio, thereby decreasing blade inlet displacement and further reducing energy loss in the flow channel before the blade inlet, improving cavitation performance. Simultaneously, it reduces impeller flow channel diffusion, improves the flow pattern between blades, and enhances impeller hydraulic performance. In this way, while improving cavitation performance, it also improves the overall pump efficiency, solves vibration and noise problems during pump operation, and ultimately improves the overall quality of the pump.

[0083] (4) Under the same head, as the overall efficiency of the pump increases, the power can decrease as a whole, which effectively saves energy and is more conducive to the long-term stable operation of the pump.

[0084] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. An optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump, characterized in that: The optimized design method for the high specific speed vertical single-stage single-suction centrifugal pump includes: Step 1: Optimize the elbow-shaped suction chamber and impeller inlet; Step 2: Optimize the volute extrusion chamber; Step 3: Optimize the impeller outlet edge; Step 1, optimizing the elbow-type suction chamber and impeller inlet, specifically includes: selecting the high specific speed centrifugal pump coefficient K0, and determining the impeller inlet diameter D. j The diameter of the inhalation chamber outlet, D s2 With D j Equal; Inhalation chamber inlet diameter D s1 The value should be the same as the design requirement for the pump inlet diameter; Determine the cross-sectional shape of the intake chamber, and select the intake chamber outlet contraction angle x and the equivalent diameter D of the outlet cross-section. x3 Choose R s2 R s2 ' and R s1 R s1 'Equivalent diameter D of the inlet elbow cross section x1 and the equivalent diameter D of the outlet elbow section x2 The contraction ratio P of the middle section of the inhalation chamber is obtained. The center distance Hx of the middle section is determined by controlling the equivalent contraction angle θs of the middle section, and the value of H1 is made to be an integer multiple of 5. Among them, R s2 R s2 Specifically, 'represents the inner streamline bending radius of the outlet elbow on the axial surface of the intake chamber and the outer streamline bending radius of the outlet elbow on the axial surface of the intake chamber.' R s1 R s1 Specifically, 'represents the inner streamline bending radius of the inlet elbow on the axial surface of the intake chamber and the outer streamline bending radius of the inlet elbow on the axial surface of the intake chamber.' H1 represents the distance between the inlet of the inhalation chamber and the center of the shaft; Step 2, optimizing the volute discharge chamber, specifically involves: While maintaining a constant flow area, controlling the shape of the flow cross-section of the pump body to reduce the wetted perimeter; adjusting the matching degree between the pump body and impeller by controlling the ratio of the volute base circle diameter to the impeller outer diameter (D3 / D2) and the ratio of the volute inlet width to the blade width (b3 / b2); to ensure that the pump body and impeller are matched to achieve the highest efficiency point between 1.0 and 1.05Q. n Q n This is for the rated flow condition, thus ensuring the extended high-efficiency range is maintained at 0.75Q. n ~1.2Q n between; Step 3, optimizing the impeller outlet edge specifically involves: the angle α3 and n of the impeller blade outlet edge in the optimized design of high specific speed vertical single-stage single-suction centrifugal pumps. s The correspondence; The water passage section of the suction chamber was changed from a large rounded rectangle to a circle. The inlet and outlet bends were designed as bends of equal diameter. The change in the water passage area was controlled within the straight conical section between the two bends of equal diameter. The outlet of the suction chamber was designed as a straight conical contraction type. It was proposed that the contraction angle x of the outlet of the suction chamber of the high specific speed single-stage single-suction centrifugal pump should be in the range of 10 to 14°. The specific structure of the suction chamber is as follows: Considering a smaller wetted perimeter, the cross-section of the suction-type water passage is changed from a large rounded rectangle to a circle. The position of the outlet edge is determined based on the vertical distance Hj from the center plane of the flow channel to the outlet edge of the suction chamber. The outlet contraction angle x of the suction chamber is selected, based on D... s2 Take the equivalent diameter D of the outlet section with x. x3 D x3 Rounded down and the value is slightly greater than D s2 The radius of curvature R of the streamline at the outlet elbow of the intake chamber axial surface s2 The value ranges from 25% to 35% D s1 And not less than 25mm; the bending radius R of the outer streamline of the outlet elbow s2 '= R s2 + D x3 Furthermore, the inner and outer streamlines are concentric at this point, and the vertical distances from the center of the circle to the center plane of the flow channel, Hs2 and Hj, are close, with a difference of less than 5%. The horizontal distances from the center of the circle to the edge of the suction chamber outlet, Js2 and R, are also close. s2 The difference is within 2%; the equivalent diameter D of the outlet elbow cross-section is close to that of the outlet elbow. x2 = D x3 The radius of curvature R of the streamline inside the inlet elbow of the suction chamber axial surface s1 The value ranges from 45% to 65% D s1 And not less than 50mm; the bending radius R of the outer streamline of the imported elbow s1 '= R s1 + D s1 Furthermore, the inner and outer streamlines are concentric, with the center located on the inlet surface of the suction chamber; the equivalent diameter D of the inlet elbow cross-section. x1 = D s1； High specific speed single-stage single-suction centrifugal pump, equivalent contraction angle θ of the suction chamber mid-section s and its calculation formula, θ s By controlling the taper of the intermediate straight conical tube in the suction chamber, and thus controlling the mid-section shrinkage ratio P, the intermediate straight conical tube can be made shorter to control costs and reduce local losses. θ s The preferred value range is 6.5–11.5°; the relevant calculations are as follows: （2） H x —Center-to-center distance of the intermediate section, unit: mm; θ s —Equivalent contraction angle of the middle section of the suction chamber of a high specific speed centrifugal pump, with a value range of 6.5 to 11.5°.

2. The optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump according to claim 1, characterized in that: Determine the impeller inlet diameter D j Then the diameter D of the suction chamber outlet s2 Values ​​and D j The relevant calculations are as follows: （1） D s2 —Diameter of the inhalation chamber outlet, unit: mm; D j —Impeller inlet diameter, unit: mm; D0—Equivalent impeller inlet diameter, unit: mm; D h —Impeller hub diameter, unit: mm; K0—Impeller inlet diameter coefficient for high specific speed centrifugal pumps, with a value range of 4.25 to 4.45; Q—Design flow rate of the water pump, unit: m³ / h 3 / s; n—Pump speed, unit: r / min; Inhalation chamber inlet diameter D s1 The value should be the same as the design requirement for the pump inlet diameter.

3. The optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump according to claim 1, characterized in that: The theoretical base circle optimization coefficient k of a high specific speed vertical single-stage single-suction centrifugal pump D3 The value ranges from 10.06 to 10.25; the optimal design calculation formula for the theoretical base circle diameter D3 is as follows: （3） n s —Specific speed of the water pump, ; H—Pump design head, unit: m; D2—Impeller diameter, unit: mm; k D2 —The D2 correction factor for high specific speed centrifugal pumps is determined based on the specific speed, with a value range of 0.997 to 1.022; k D3 —Optimal coefficient for the theoretical base circle of the volute casing of a high specific speed centrifugal pump, with a value range of 10.06 to 10.25; By calculating the value of D3, its ratio to the impeller outer diameter, D3 / D2, is controlled within the range of 1.05 to 1.

07.

4. The optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump according to claim 1, characterized in that: vortex inlet width optimization coefficient k b3 The value ranges from 0.965 to 0.767; simultaneously, an optimized design calculation formula for the inlet width b3 of the vortex chamber of a high specific speed vertical single-stage single-suction centrifugal pump is proposed: （4） k b2 — Correction factor b2 for high specific speed centrifugal pumps, which is determined based on the specific speed and ranges from 0.965 to 0.767; k b3 —Optimal coefficient for the inlet width of the volute of a high specific speed centrifugal pump, with a value range of 1.18 to 1.48; By calculating and optimizing b3, the ratio of b3 to the blade width, b3 / b2, is controlled within the range of 1.6 to 2.

0. The pump body controls the shape of the flow cross-section of the volute discharge chamber, controls the theoretical base circle diameter D3 of the volute, and controls the inlet width b3 of the volute chamber, all of which together adjust the matching degree between the pump body and the impeller; so that the pump body and impeller matching control achieves the highest efficiency point between 1.0 and 1.05Q. n This ensures that the high-efficiency region is widened within 0.75Q. n ~1.2Q n between.

5. The optimized design method for a high specific speed vertical single-stage single-suction centrifugal pump according to claim 1, characterized in that: The optimal design method for high specific speed vertical single-stage single-suction centrifugal pumps yielded the following D: j And α3, a method to optimize the streamline of the impeller back cover; proposes a diffusion ratio P between the inlet and outlet channels of the blades that is beneficial to improving impeller efficiency. 叶 The range is 1.2 to 1.3; The inlet angle α1 of the impeller shaft surface streamline is controlled to be 0°, i.e., horizontal, while the outlet angle α2 of the impeller shaft surface streamline is controlled to be 86-90°, thereby controlling the radius of curvature R. q Greater than 25mm, radius of curvature R h Greater than 55mm, ultimately increasing the minimum flow area F at the blade inlet. i Simultaneously control the diffusion ratio P between the inlet and outlet channels of the blades. 叶 Between 1.2 and 1.3.

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