A vertical centrifugal pump for improving the hydraulic stability of the hump area

Abstract

The present invention provides a vertical centrifugal pump for improving the hydraulic stability of a hump region, comprising a spiral volute and a centrifugal impeller. The centrifugal impeller is located within the spiral volute. Hydrofoil-shaped radial guide vanes having a blade number that is a prime number to the blade number of the centrifugal impeller are provided between the centrifugal impeller outlet and the spiral volute inlet. The chord length, cross-sectional area, and maximum thickness of several of the radial guide vanes increase as the cross-sectional area of ​​the spiral volute increases. A radial guide vane having a minimum chord length, cross-sectional area, and maximum thickness is located at the point where the cross-sectional area of ​​the spiral volute is the smallest. The inlet diameters and inlet placement angles of the several radial guide vanes are consistent. The present invention not only suppresses the hump characteristic of the pump at low flow rates, but also reduces the magnitude and fluctuation of the axial and radial forces acting on the impeller and guide vanes in the hump region, thereby comprehensively improving the hydraulic stability of a vertical centrifugal pump with guide vanes in the hump region from multiple aspects.

Description

Technical Field

[0001] The present invention relates to the technical field of water pump design, and in particular to a vertical centrifugal pump capable of improving the hydraulic stability of a hump area. Background Art

[0002] Centrifugal pumps are widely used in many fields, including industry, energy, and agriculture. Vertical centrifugal pumps have the advantages of a simple structure, with guide bearings and thrust bearings widely used in turbines and pumped-storage water turbines, and mature design and manufacturing processes. Due to their outstanding advantages, vertical centrifugal pump devices have become the core power equipment in major water conservancy projects such as water resource allocation. Vertical centrifugal pumps in major water conservancy projects are mainly characterized by large size, large flow, high head, and high power. They are mainly composed of key hydraulic components such as elbow-shaped inlet pipes, centrifugal impellers, radial guide vanes, and spiral volutes. The radial guide vane structure is arranged between the impeller outlet and the volute inlet, playing a key role in connecting the upper and lower parts. The radial guide vanes have multiple functions such as rectification, pressure expansion, and balancing the forces on the unit.

[0003] At present, in addition to performance requirements, operational stability has become the primary concern of vertical centrifugal pump units with guide vanes. In order to meet operational requirements, especially during transition processes such as startup and shutdown, the unit often operates under conditions that deviate from the design, and it is inevitable to cross the hump area. When operating in the hump area, flow instabilities such as stall and secondary flow in the guide vanes can easily lead to increased pressure pulsation, increased axial and radial forces, and other hydraulic instabilities, which in turn cause the entire pump system to oscillate, seriously affecting the safe and stable operation of the unit. At present, the fixed guide vane structure used in traditional vertical centrifugal pumps is generally composed of multiple hydrofoil structures symmetrically distributed along the circumferential direction between the impeller and the volute, and the hydraulic stability problem of the hump area is not considered. In order to improve the hydraulic stability of the hump area of ​​the vertical centrifugal pump, the present invention proposes a gradient guide vane structure, which is not only used to improve the hump characteristics of the vertical centrifugal pump, but also to improve the unsteady force characteristics of the hydraulic components. The present invention is of great significance for improving the hydraulic stability of the vertical centrifugal pump with guide vanes under hump area operating conditions and the safe and stable operation of the device.

[0004] The patent document discloses a guide vane combination structure for improving the hump instability phenomenon of a volute centrifugal pump, and proposes a structure of a combination of large and small guide vanes to alleviate the hump phenomenon under low flow conditions of the centrifugal pump. However, the invention only considers how to alleviate the hump but does not take into account that the guide vane structure of different sizes will lead to an increase and unevenness in the radial and axial forces on the hydraulic components, thereby posing a greater threat to the operating stability of the unit's rotor system. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present invention provides a vertical centrifugal pump that improves the hydraulic stability of the hump area. By improving the matching between the impeller, guide vanes and volute, it can not only suppress the hump characteristics of the pump at small flow rates, but also reduce the size and fluctuation of the axial and radial forces exerted on the impeller and guide vanes in the hump area, thereby comprehensively improving the hydraulic stability of the vertical centrifugal pump with guide vanes in the hump area from multiple aspects.

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

[0007] A vertical centrifugal pump for improving the hydraulic stability of a hump area includes a spiral volute and a centrifugal impeller, wherein the centrifugal impeller is located in the spiral volute, and a hydrofoil-shaped radial guide vane having a blade number that is a prime number to the blade number of the centrifugal impeller is provided between the centrifugal impeller outlet and the spiral volute inlet; the chord length, cross-sectional area and maximum thickness of several of the radial guide vanes increase as the cross-sectional area of ​​the spiral volute increases, and a radial guide vane having the smallest chord length, cross-sectional area and maximum thickness is located at the point where the cross-sectional area of ​​the spiral volute is the smallest, and the inlet diameters and inlet placement angles of several of the radial guide vanes are kept consistent.

[0008] Furthermore, the radial guide vanes are divided into standard guide vanes and progressive guide vane assemblies. The standard guide vanes are located at the tongue of the spiral volute. The chord length and maximum thickness of the radial guide vanes in the progressive guide vane assembly increase linearly along the circumference of the spiral volute, while the cross-sectional area of ​​the radial guide vanes in the progressive guide vane assembly increases nonlinearly along the circumference of the spiral volute. The increasing trend of the chord length, maximum thickness, and cross-sectional area of ​​the radial guide vanes in the progressive guide vane assembly corresponds to the increasing trend of the cross-sectional area of ​​the spiral volute. A radial guide vane in the progressive guide vane assembly with the minimum chord length, cross-sectional area, and maximum thickness is arranged at the point of the spiral volute with the minimum cross-sectional area, adjacent to the standard guide vane.

[0009] Furthermore, the chord length of the minimum radial guide vane is 0.5 times the chord length of the standard guide vane, the cross-sectional area of ​​the minimum radial guide vane is 0.25 times the cross-sectional area of ​​the standard guide vane, and the maximum thickness of the minimum radial guide vane is 0.5 times the maximum thickness of the standard guide vane.

[0010] Furthermore, the radial guide vanes in the incremental guide vane assembly are uniformly arranged at intervals of 360 / N° along the circumferential direction of the spiral volute where the cross-sectional area increases, starting from the radial guide vane with the minimum value; the chord length L of the xth radial guide vane in the incremental guide vane assembly is x Increase linearly according to the following formula:

[0011]

[0012] Where: L xis the chord length of the xth radial guide vane, x∈[2,……,N-1], N is the total number of guide vanes, L N is the chord length of the standard guide vane.

[0013] Furthermore, the radial guide vanes in the incremental guide vane assembly are uniformly arranged at intervals of 360 / N° along the circumferential direction of the spiral volute where the cross-sectional area increases, starting from the radial guide vane with the minimum value; the maximum thickness δ of the xth radial guide vane in the incremental guide vane assembly is x Increase linearly according to the following formula:

[0014]

[0015] Where: x is the maximum thickness of the x-th radial guide vane, x∈[2,……,N-1], N is the total number of guide vanes, δ N It is the maximum thickness of standard guide vanes.

[0016] Furthermore, the radial guide vanes in the incremental guide vane assembly are uniformly arranged at intervals of 360 / N° along the circumferential direction in which the cross-sectional area of ​​the spiral volute increases, starting from the radial guide vane with the minimum value; and the cross-sectional area of ​​the x-th radial guide vane in the incremental guide vane assembly increases nonlinearly according to the following formula:

[0017] A x =ax 2 +bx+c

[0018] Among them, A x is the cross-sectional area of ​​the x-th radial guide vane, x∈[2,…,N-1], N is the total number of guide vane blades, a, b and c are coefficients and are obtained by the following equations:

[0019]

[0020] Among them, A N is the cross-sectional area of ​​a standard guide vane.

[0021] Furthermore, the chord length, cross-sectional area and maximum thickness of the standard guide vane are all derived based on the centrifugal impeller outlet diameter, outlet placement angle and the spiral volute inlet diameter and cross-sectional area.

[0022] The beneficial effects of the present invention are:

[0023] 1. The vertical centrifugal pump for improving the hydraulic stability in the hump region described in the present invention has a plurality of radial guide vanes whose chord length, cross-sectional area, and maximum thickness all increase as the cross-sectional area of ​​the spiral volute increases, thereby improving the comprehensive hydraulic stability of the vertical centrifugal pump with guide vanes in the hump region. The incremental guide vane assembly of the present invention can further improve the matching of the guide vanes with the impeller and volute, reduce internal flow losses of the centrifugal pump, improve the flow pattern within the hydraulic components in the hump region and the pressure expansion effect of the guide vanes, and better balance the axial and radial forces acting on the guide vanes and impeller while suppressing the hump characteristics of the performance curve under low flow rates. The present invention is of great significance for improving the safety and stability of the unit of a vertical centrifugal pump with guide vanes when operating under non-design conditions.

[0024] 2. The vertical centrifugal pump for improving the hydraulic stability of the hump area described in the present invention, the incremental guide vane assembly improves the hydraulic matching between the guide vane and the impeller and volute, improves the problem that the traditional guide vane structure is prone to unstable flow at low flow rates, thereby suppressing the hump characteristics of the vertical centrifugal pump at low flow rates, improving the hydraulic efficiency of the pump at low flow rates and saving energy consumption.

[0025] 3. The vertical centrifugal pump for improving the hydraulic stability of the hump area described in the present invention has an increasing trend in the chord length, cross-sectional area and maximum thickness of the guide vanes in the progressive guide vane assembly that corresponds to the increasing trend of the cross-sectional area of ​​the volute, greatly improving the matching of the guide vanes and the volute. Therefore, while suppressing the hump characteristics, it can also effectively improve the unsteady characteristics of the axial and radial forces acting on the impeller and guide vanes in the hump area, which is mainly reflected in the fact that the amplitudes of the axial and radial forces of the impeller and guide vanes changing with time are significantly reduced, and the force distribution with time is more uniform, that is, the axial and radial forces are better balanced, thereby ensuring the safe and stable operation of the rotor system and improving the comprehensive hydraulic stability of the vertical centrifugal pump unit in the hump area.

[0026] 4. The vertical centrifugal pump for improving the hydraulic stability of the hump area described in the present invention has an incremental guide vane assembly that improves the hydraulic matching between the guide vanes, the impeller, and the volute, and can significantly improve flow separation and flow channel blockage within the guide vanes, thereby narrowing the range of the hump area, suppressing the hump characteristic curve and improving efficiency, so that the centrifugal pump unit can achieve efficient and stable operation within a larger flow range.

[0027] 5. The vertical centrifugal pump for improving the hydraulic stability of the hump area described in the present invention, the incremental guide vane assembly can effectively improve the unsteady characteristics of the axial and radial forces on the impeller and guide vanes in the hump area while suppressing the hump characteristics, which is mainly reflected in the significant reduction in the amplitude of the axial and radial forces of the impeller and guide vanes changing with time. The maximum amplitude of the axial force on the incremental guide vane assembly is reduced by 24% compared with the large and small guide vane structures in the prior art, and is reduced by 41% compared with all standard guide vanes; the maximum amplitude of the radial force on the incremental guide vane assembly is reduced by 10% compared with both the all-standard guide vanes and the large and small guide vane structures; when the incremental guide vane assembly is used, the maximum amplitude of the radial force on the impeller is reduced by 32% compared with all-standard guide vanes, and is further reduced by 19% compared with the large and small guide vane structure; when the incremental guide vane assembly is used, the maximum amplitude of the axial force on the impeller is reduced by 25% compared with all-standard guide vanes, and is further reduced by 4% compared with the large and small guide vane structure. Therefore, when the progressive guide vane assembly is used, the fluctuations in the axial and radial forces acting on the impeller and guide vanes are significantly reduced, thereby significantly improving the hydraulic stability of the vertical centrifugal pump unit in the hump area. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a schematic structural diagram of the vertical centrifugal pump for improving the hydraulic stability of the hump area according to the present invention.

[0030] Figure 2 This is a schematic diagram of the installation of the radial guide vanes described in the present invention.

[0031] Figure 3 This is a schematic diagram of the positions of the standard guide vane and incremental guide vane assemblies described in the present invention.

[0032] Figure 4 Schematic diagram of parameters of the radial guide vane wing shape described in the present invention.

[0033] Figure 5 This is a curve showing the increasing regularity of the guide vane chord length in the incremental guide vane assembly described in the present invention.

[0034] Figure 6 This is a curve showing the increasing regularity of the cross-sectional area of ​​the guide vanes in the incremental guide vane assembly described in the present invention.

[0035] Figure 7 This is a curve showing the increasing rule of the maximum thickness of the guide vanes in the incremental guide vane assembly of the present invention.

[0036] Figure 8 The flow-head curves of the vertical centrifugal pump with standard guide vanes, combined guide vanes and the guide vanes of the present invention under different working conditions in the hump area.

[0037] Figure 9 Flow-efficiency curves of a vertical centrifugal pump with standard guide vanes, combined guide vanes, and the guide vanes of the present invention under different working conditions in the hump region.

[0038] Figure 10 Schematic diagram of streamline distribution within standard guide vanes, combined guide vanes and the guide vanes of the present invention under hump conditions.

[0039] Figure 11 Schematic diagram of radial force distribution of standard guide vanes, combined guide vanes and guide vanes of the present invention under hump conditions.

[0040] Figure 12 Schematic diagram of the axial force distribution of the standard guide vane, the combined guide vane and the guide vane of the present invention under hump conditions.

[0041] Figure 13 The figure is a comparison of the force amplitudes of the impeller and guide vanes of the standard guide vanes, the combined guide vanes and the guide vanes of the present invention under hump conditions.

[0042] In the picture:

[0043] 1-Elbow inlet pipe, 2-Centrifugal impeller, 3-Radial guide vane; 3-1-Standard guide vane; 4-Spiral volute. DETAILED DESCRIPTION

[0044] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "axial", "radial", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0046] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0047] like Figure 1 and Figure 2 As shown, the vertical centrifugal pump for improving the hydraulic stability of the hump area described in the present invention includes an elbow-shaped water inlet pipe 1, a centrifugal impeller 2, a radial guide vane 3 and a spiral volute 4, the elbow-shaped water inlet pipe 1 is connected to the inlet of the spiral volute 4, the centrifugal impeller 2 is located in the spiral volute 4, and a hydrofoil-shaped radial guide vane 3 with a blade number that is a prime number to the blade number of the centrifugal impeller 2 is provided between the outlet of the centrifugal impeller 2 and the inlet of the spiral volute 4; the chord length, cross-sectional area and maximum thickness of several of the radial guide vanes 3 increase as the cross-sectional area of ​​the spiral volute 4 increases, and a radial guide vane 3 with the minimum chord length, cross-sectional area and maximum thickness is located at the point where the cross-sectional area of ​​the spiral volute 4 is the smallest, and the inlet diameter and inlet placement angle of several of the radial guide vanes 3 are kept consistent.

[0048] like Figure 3 and Figure 4As shown, several radial guide vanes 3 are divided into standard guide vanes 3-1 and incremental guide vane assemblies. The standard guide vane 3-1 is located at the tongue of the spiral volute 4. The chord length and maximum thickness of the radial guide vanes 3 in the incremental guide vane assembly increase linearly along the circumferential direction of the spiral volute 4. The cross-sectional area of ​​the radial guide vanes 3 in the incremental guide vane assembly increases nonlinearly along the circumferential direction of the spiral volute 4. The growth trend of the chord length, maximum thickness and cross-sectional area of ​​the radial guide vanes 3 in the incremental guide vane assembly corresponds to the growth trend of the cross-sectional area of ​​the spiral volute 4. A radial guide vane 3 with the minimum chord length, cross-sectional area and maximum thickness in the incremental guide vane assembly is arranged at the place with the minimum cross-sectional area of ​​the spiral volute 4 adjacent to the standard guide vane 3-1. For example, Figure 2 As shown in the figure, there are 13 radial guide vanes 3. The radial guide vane 3 numbered 1' in the figure is the minimum radial guide vane 3, the radial guide vane 3 numbered 13' in the figure is the standard guide vane 3-1, and the incremental guide vane assembly is the radial guide vanes 3 numbered 1' to 12'. The incremental guide vane assembly of the present invention improves the hydraulic matching between the guide vanes, the impeller, and the volute, and improves the problem of unstable flow caused by traditional guide vane structures at low flow rates. This suppresses the hump characteristic of the vertical centrifugal pump at low flow rates, improves the hydraulic efficiency of the pump at low flow rates, and saves energy. The growth trend of the chord length, cross-sectional area and maximum thickness of the guide vanes in the progressive guide vane assembly corresponds to the growth trend of the cross-sectional area of ​​the volute, which greatly improves the matching of the guide vanes and the volute. The amplitude of the axial force and radial force of the impeller and guide vanes changing with time is significantly reduced, and the force distribution over time is more uniform, that is, the axial force and radial force are better balanced, thereby ensuring the safe and stable operation of the rotor system and improving the comprehensive hydraulic stability of the vertical centrifugal pump unit in the hump area.

[0049] The chord length of the minimum radial guide vane 3 is 0.5 times the chord length of the standard guide vane 3-1, the cross-sectional area of ​​the minimum radial guide vane 3 is 0.25 times the cross-sectional area of ​​the standard guide vane 3-1, and the maximum thickness of the minimum radial guide vane 3 is 0.5 times the maximum thickness of the standard guide vane 3-1.

[0050] The radial guide vanes 3 in the incremental guide vane assembly are arranged uniformly at intervals of 360 / N° along the circumferential direction of the spiral volute 4, starting from the radial guide vane 3 with the minimum value; the chord length L of the xth radial guide vane 3 in the incremental guide vane assembly is x Increase linearly according to the following formula:

[0051]

[0052] Where: L x is the chord length of the x-th radial guide vane 3, x∈[2,……,N-1], N is the total number of guide vane blades, L NIt is the chord length of the standard guide vane 3-1.

[0053] The maximum thickness δ of the xth radial guide vane 3 in the incremental guide vane assembly x Increase linearly according to the following formula:

[0054]

[0055] Where: x is the maximum thickness of the x-th radial guide vane 3, x∈[2,……,N-1], N is the total number of guide vanes, δ N The maximum thickness of the standard guide vane 3-1.

[0056] The cross-sectional area of ​​the xth radial guide vane 3 in the incremental guide vane assembly increases nonlinearly according to the following formula:

[0057] A x =ax 2 +bx+c

[0058] Among them, A x is the cross-sectional area of ​​the x-th radial guide vane 3, x∈[2,…,N-1], N is the total number of guide vane blades, a, b and c are coefficients and are obtained by the following equations:

[0059]

[0060] Among them, A N is the cross-sectional area of ​​the standard guide vane 3-1.

[0061] Example 1

[0062] In the embodiment, the outer diameter of the centrifugal impeller 2 is 360 mm, the rotation speed is 1150 r / min, the design operating flow rate is 214 kg / s, and the design head is 18.74 m. The number of blades of the centrifugal impeller 2 is 7, and 13 hydrofoil-shaped radial guide vanes 3 are arranged between the outlet of the centrifugal impeller 2 and the inlet of the spiral volute 4. The number of blades of the radial guide vanes 3, 13, and the number of impeller blades, 7, are prime numbers to each other. Figure 2 As shown; the fluid enters the radial guide vane 3 under the acceleration of the centrifugal force of the centrifugal impeller 2. The radial guide vane 3 plays a key role in connecting the upper and lower parts. The radial guide vane can make the flow pattern of the fluid before entering the volute smoother, reduce the flow velocity and convert kinetic energy into pressure energy, and at the same time balance the radial force on the unit;

[0063] like Figure 2 and Figure 3 As shown, the radial guide vanes 3 are divided into standard guide vanes 3-1 and incremental guide vane assemblies. The standard guide vanes 3-1 are located at the tongue of the spiral volute 4. According to the design parameters of the centrifugal impeller 3 outlet and the spiral volute 4 inlet, the standard guide vanes 3-1 (i.e. Figure 2 Parameters of radial guide vane 3) of serial number 13', such as the guide vane inlet diameter of standard guide vane 3-1 is 372mm, the axial width of standard guide vane 3-1 is 75mm, the inlet placement angle of standard guide vane 3-1 is 30°, the airfoil chord length L of standard guide vane 3-1 N =66.33mm, the airfoil cross-sectional area A of the standard guide vane 3-1 N =487.53mm 2 , the maximum thickness of the airfoil of the standard guide vane 3-1 is δ N =9.57mm.

[0064] See attached Figure 3 , a radial guide vane 3 (i.e. Figure 2 The radial guide vane 3 of serial number 1' has the same inlet diameter, inlet placement angle and axial width as the standard guide vane 3-1. The radial guide vane 3 of serial number 1' is spaced apart from the standard guide vane 3-1 at an angle of 360 / 13=27.69° in the circumferential direction.

[0065] like Figure 2 As shown, the chord length of the minimum radial guide vane 3 is 0.5 times the chord length of the standard guide vane 3-1, that is, 33.165 mm; the cross-sectional area of ​​the minimum radial guide vane 3 is 0.25 times the cross-sectional area of ​​the standard guide vane 3-1, that is, 121.91 mm 2 The maximum thickness of the minimum radial guide vane 3 is 0.5 times the maximum thickness of the standard guide vane 3-1, that is, 4.785 mm. Finally, according to the above specific design parameters, the minimum radial guide vane 3 (i.e. Figure 2 Radial guide vane 3 of sequence number 1').

[0066] like Figure 2 As shown, starting from the radial guide vane 3 with the minimum value, radial guide vanes 3 with airfoils similar to those of the standard guide vane 3-1 are evenly arranged at intervals of 360 / 13=27.69° along the circumferential direction where the cross-sectional area of ​​the volute increases, with airfoils having gradually increasing chord lengths, cross-sectional areas, and maximum thicknesses, until the radial guide vane 3 with number 12'. The radial guide vane 3 with number 12' is adjacent to the standard guide vane 3-1 and has a similar or identical size. This is because the cross-sectional area of ​​the volute at the radial guide vane 3 with number 12' is almost the same as the cross-sectional area of ​​the volute at the radial guide vane 3 with number 13'.

[0067] like Figure 3 and Figure 5 As shown, the chord length L of the xth radial guide vane 3 in the incremental guide vane assembly is x Increase linearly according to the following formula:

[0068]

[0069] Where: L x is the chord length of the x-th radial guide vane 3, x∈[2,……,N-1], N is the total number of guide vane blades, that is, N=13.

[0070] like Figure 3 and Figure 6 As shown, the cross-sectional area of ​​the x-th radial guide vane 3 in the incremental guide vane assembly increases nonlinearly according to the following formula:

[0071] A x =ax 2 +bx+c

[0072] In the above formula, a, b, and c can be obtained from the following equations:

[0073]

[0074] According to the above formula, A x =0.886x 2 +21.722x+99.272;

[0075] like Figure 3 and Figure 7 As shown, the maximum thickness δ of the xth radial guide vane 3 in the incremental guide vane assembly is x Increase linearly according to the following formula:

[0076]

[0077] In the embodiment provided herein, the design parameters of radial guide vanes 3, numbered 2 through 12, are calculated using the aforementioned formula for increasing chord length, cross-sectional area, and maximum thickness. The chord length L and maximum thickness δ of each guide vane airfoil exhibit a linear growth pattern, while the cross-sectional area A of each guide vane airfoil exhibits a nonlinear growth pattern. The increasing trends in chord length L, cross-sectional area A, and maximum thickness δ of the progressive guide vane assembly correspond to the increasing trends in the volute cross-sectional area.

[0078] For the convenience of description, the uniformly distributed standard guide vane 3-1 in the prior art is recorded as the standard guide vane, and the structure of the large and small combined guide vanes in the other prior art is recorded as the combined guide vane, such as Figure 8 As shown, the different flow rates Q / Q in the hump area des = 0.6 to 0.8, the curves of head variation with flow rate of standard guide vanes, combined guide vanes and guide vanes of the present invention were obtained based on the computational fluid dynamics (CFD) method. Figure 8 As shown, the vertical centrifugal pump with standard guide vanes has a flow rate of 0.75Q / Q des Down to 0.74Q / Q desWhen the flow rate decreases to 0.72Q / Q, the head suddenly drops and causes a positive slope of the flow-head curve, that is, the hump phenomenon. des And dropped 0.71Q / Q des When the flow rate further decreased to 0.66Q / Q des And dropped to 0.65Q / Q des When the head drops significantly for the third time, the vertical centrifugal pump with standard guide vanes has multiple humps. The head of the vertical centrifugal pump with combined guide vanes in the hump area is significantly higher than that of the standard guide vanes, and the first drop condition is delayed to 0.71Q / Q. des , but at a flow rate of 0.68Q / Q des ~0.65Q / Q des The secondary hump phenomenon is still observed. Overall, compared with the standard guide vane, the hump area of ​​the combined guide vane is reduced and the lift is improved. When the guide vane structure of the present invention is adopted, the lift in the hump area is further improved, and only when the flow rate is 0.74Q / Q des ~0.72Q / Q des A hump phenomenon with a small positive slope is observed within the range; therefore, the gradient guide vane structure of the present invention can significantly reduce the range of the hump area, suppress the hump characteristic curve and increase the head, so that the centrifugal pump unit can achieve stable operation within a larger flow range. des is the flow rate under design conditions.

[0079] like Figure 9 As shown, the different flow rates Q / Q in the hump area des = 0.6 to 0.8, the efficiency curves of the standard guide vanes, combined guide vanes, and the guide vanes of the present invention as a function of flow rate were obtained based on the computational fluid dynamics (CFD) method. The vertical centrifugal pump with standard guide vanes has little change in efficiency compared to the vertical centrifugal pump with combined guide vanes. However, the efficiency of the vertical centrifugal pump with the guide vane structure of the present invention is significantly improved, and the increase is even, especially at 0.73Q / Q des ~0.8Q / Q des The efficiency is significantly improved within the range, that is, the gradient guide vane of the present invention improves the efficiency of the vertical centrifugal pump under small flow conditions and reduces the fluctuation of the efficiency.

[0080] like Figure 10As shown, based on the computational fluid dynamics (CFD) method, the streamline distribution of the standard guide vane, the combined guide vane and the guide vane of the present invention on the middle section of the guide vane under the hump condition is simulated. As can be seen from the figure, the standard guide vane has a flow blockage phenomenon at mark A, and produces obvious flow separation and flow blockage at mark B; the flow blockage phenomenon of the combined guide vane structure at mark A disappears, but there are still flow separation and blockage phenomena at mark B; the streamline distribution of the guide vane of the present invention at marks A and B is relatively smooth, and the flow blockage and flow separation phenomena disappear. This is because the matching of the hydraulic components has been significantly improved, so the hump characteristic curve is significantly suppressed and the efficiency is improved.

[0081] like Figure 11 As shown in the figure, the distribution of the radial force vector points of the standard guide vane, the combined guide vane and the guide vane of the present invention under the hump condition is simulated based on the computational fluid dynamics (CFD) method. It can be seen from the figure that the vector points of the radial force on the standard guide vane are very scattered at different times, and the vector points at most times are far away from the origin, so the radial force fluctuates greatly; the vector points of the radial force on the combined guide vane structure are more concentrated than those on the standard guide vane, but the vector points are basically concentrated in the area where both the X and Y directions are negative. Therefore, although the fluctuation of the radial force on the combined guide vane structure is reduced, it is still unevenly distributed in the circumferential direction; the vector points of the radial force on the guide vane structure of the present invention are more concentrated and closer to the origin than those on the standard guide vane and the combined guide vane structure. Therefore, the guide vane structure of the present invention can effectively improve the unsteady characteristics of the radial force on the guide vane, that is, the radial force is better balanced.

[0082] like Figure 12 As shown in the figure, the fluctuation of the axial force on the standard guide vane, the combined guide vane and the guide vane of the present invention under hump conditions is simulated based on the computational fluid dynamics (CFD) method. As can be seen from the figure, the axial force on the standard guide vane and the combined guide vane structure fluctuates greatly over time and the periodicity is not obvious. The fluctuation of the axial force on the guide vane structure of the present invention over time is significantly reduced and shows periodicity, that is, the unsteady characteristics of the axial force of the guide vane of the present invention are significantly improved, and the maximum amplitude ΔF of the axial force on the standard guide vane is N =64.23N, the maximum amplitude of the axial force on the combined guide vane structure is reduced by ΔF C =49.54N, the maximum amplitude of the combined guide vane is reduced by 23% compared with the standard guide vane, and the maximum amplitude of the axial force on the guide vane structure of the present invention is further reduced to ΔF G =37.72N, which is 24% lower than that of the combined guide vane structure and 41% lower than that of the standard guide vane. Therefore, the guide vane structure of the present invention can greatly reduce the axial force it is subjected to.

[0083] like Figure 13As shown in the figure, a comparison of the amplitudes of the axial and radial forces on the impeller and guide vanes of the standard guide vanes, combined guide vanes and guide vanes of the present invention under hump conditions is statistically analyzed. As can be seen from the figure, the maximum amplitudes of the radial forces on the standard guide vanes and combined guide vanes are basically the same, while the guide vanes of the present invention are significantly reduced, with the radial force amplitude decreasing by 10% compared to the combined guide vane structure; the maximum amplitude of the axial force on the guide vanes of the present invention is also significantly reduced compared to the standard guide vanes and combined guide vanes, decreasing by 26% compared to the standard guide vane structure and by 13% compared to the combined guide vane structure; when the guide vane structure of the present invention is used, the maximum amplitudes of the radial and axial forces on the impeller are significantly lower than those of the standard guide vanes and combined guide vanes, among which the maximum amplitude of the impeller radial force decreases by 32% compared to the standard guide vanes and by another 19% compared to the combined guide vanes; the maximum amplitude of the impeller axial force decreases by 25% compared to the standard guide vanes and by another 4% compared to the combined guide vanes. Therefore, the guide vane structure of the present invention in the embodiment can effectively reduce the magnitude and fluctuation of the axial and radial forces acting on the impeller and the guide vane while suppressing the hump characteristic of the vertical centrifugal pump.

[0084] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of 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.

[0085] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A vertical centrifugal pump for improving the hydraulic stability of a hump region, comprising a spiral volute (4) and a centrifugal impeller (2), wherein the centrifugal impeller (2) is located in the spiral volute (4), and is characterized in that: A hydrofoil-shaped radial guide vane (3) is provided between the outlet of the centrifugal impeller (2) and the inlet of the spiral volute (4), the number of blades of which is a prime number to the number of blades of the centrifugal impeller (2); the chord length, cross-sectional area and maximum thickness of a plurality of the radial guide vanes (3) increase as the cross-sectional area of ​​the spiral volute (4) increases, a radial guide vane (3) having the minimum chord length, cross-sectional area and maximum thickness is located at the point where the cross-sectional area of ​​the spiral volute (4) is the smallest, and the inlet diameter and inlet placement angle of the plurality of the radial guide vanes (3) remain consistent; The plurality of radial guide vanes (3) are divided into standard guide vanes (3-1) and progressive guide vane assemblies, wherein the standard guide vane (3-1) is located at the tongue of the spiral volute (4), the chord length and maximum thickness of the radial guide vane (3) in the progressive guide vane assembly increase linearly along the circumferential direction of the spiral volute (4), the cross-sectional area of ​​the radial guide vane (3) in the progressive guide vane assembly increases nonlinearly along the circumferential direction of the spiral volute (4), and the growth trend of the chord length, maximum thickness and cross-sectional area of ​​the radial guide vane (3) in the progressive guide vane assembly corresponds to the growth trend of the cross-sectional area of ​​the spiral volute (4); a radial guide vane (3) in the progressive guide vane assembly whose chord length, cross-sectional area and maximum thickness are all minimum values ​​is arranged at the point of the spiral volute (4) with the smallest cross-sectional area adjacent to the standard guide vane (3-1).

2. The vertical centrifugal pump for improving the hydraulic stability of the hump area according to claim 1, characterized in that: The chord length of the minimum radial guide vane (3) is 0.5 times the chord length of the standard guide vane (3-1), the cross-sectional area of ​​the minimum radial guide vane (3) is 0.25 times the cross-sectional area of ​​the standard guide vane (3-1), and the maximum thickness of the minimum radial guide vane (3) is 0.5 times the maximum thickness of the standard guide vane (3-1).

3. The vertical centrifugal pump for improving the hydraulic stability of the hump area according to claim 1, characterized in that: The radial guide vanes (3) in the incremental guide vane assembly are uniformly arranged at intervals of (360 / N) degrees along the circumferential direction of the spiral volute (4) in which the cross-sectional area increases, starting from the radial guide vane (3) with the minimum value; the chord length L of the xth radial guide vane (3) in the incremental guide vane assembly is x Increase linearly according to the following formula: ， Where: L x is the chord length of the xth radial guide vane (3), , N is the total number of guide vanes, L N is the chord length of the standard guide vane (3-1).

4. The vertical centrifugal pump for improving the hydraulic stability of the hump area according to claim 1, characterized in that: The radial guide vanes (3) in the incremental guide vane assembly are arranged uniformly at intervals of (360 / N) degrees along the circumferential direction of the spiral volute (4) in which the cross-sectional area increases, starting from the radial guide vane (3) with the minimum value; the maximum thickness δ of the xth radial guide vane (3) in the incremental guide vane assembly is x Increase linearly according to the following formula: ， Where: x is the maximum thickness of the xth radial guide vane (3), , N is the total number of guide vanes, δ N The maximum thickness of the standard guide vane (3-1).

5. The vertical centrifugal pump for improving the hydraulic stability of the hump area according to claim 1, characterized in that: The radial guide vanes (3) in the incremental guide vane assembly are uniformly arranged at intervals of (360 / N) degrees along the circumferential direction of the spiral volute (4) in which the cross-sectional area increases, starting from the radial guide vane (3) with the minimum value; the cross-sectional area of ​​the x-th radial guide vane (3) in the incremental guide vane assembly increases nonlinearly according to the following formula: ， Among them, A x is the cross-sectional area of ​​the xth radial guide vane (3), , N is the total number of guide vanes, a, b and c are coefficients and are obtained by the following equations: ， Among them, A N is the cross-sectional area of ​​the standard guide vane (3-1).

6. The vertical centrifugal pump for improving the hydraulic stability of the hump area according to claim 1, characterized in that: The inlet diameter, inlet placement angle, chord length, cross-sectional area and maximum thickness of the standard guide vane (3-1) are all obtained based on the outlet diameter and outlet placement angle of the centrifugal impeller (2) and the inlet diameter and cross-sectional area of ​​the spiral volute (4).

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