Vertical centrifugal pump having improved hydraulic stability in hump region

Abstract

A vertical centrifugal pump having improved hydraulic stability in a hump region, comprising a volute casing (4) and a centrifugal impeller (2), wherein the centrifugal impeller (2) is located in the volute casing (4); hydrofoil-profile radial guide vanes (3) are provided between an outlet of the centrifugal impeller (2) and an inlet of the volute casing (4), the number of the vanes being coprime to the number of blades of the centrifugal impeller (2); the chord lengths, the cross-sectional areas and the maximum thicknesses of the plurality of radial guide vanes (3) each gradually increase along the increase of the cross-sectional area of the volute casing (4); the radial guide vane (3) having the minimum chord length, the minimum cross-sectional area, and the minimum maximum thickness is located at a position corresponding to the minimum cross-sectional area of the volute casing (4); the plurality of radial guide vanes (3) have the same inlet diameter and the same inlet installation angle. In this way, the hump characteristics of the pump at low flow rates can be suppressed, and the magnitudes and fluctuations of the axial and radial forces on the impeller and the guide vanes in the hump region can be reduced, thereby comprehensively improving the hydraulic stability of the vertical centrifugal pump having the guide vanes in the hump region in many aspects.

Description

A vertical centrifugal pump for improving the hydraulic stability of a hump region TECHNICAL FIELD

[0001] The present application relates to the technical field of water pump design, and particularly relates to a vertical centrifugal pump for improving the hydraulic stability of a hump region. BACKGROUND

[0002] Centrifugal pumps are widely used in many fields such as industry, energy and agriculture. The vertical centrifugal pump has the advantages of simple structure, guide bearing and thrust bearing structure, which is widely used in water turbines, pumped storage pump water turbines, and mature design and manufacturing process. The vertical centrifugal pump device has become the core power equipment in major water conservancy projects such as water resource allocation due to its outstanding advantages. The vertical centrifugal pump in major water conservancy projects mainly has the characteristics of large size, large flow, high head and large power, and is mainly composed of elbow-shaped inlet pipe, centrifugal impeller, radial guide vane and spiral volute. The radial guide vane structure is arranged between the impeller outlet and the volute inlet, and plays a key role in connecting the upper and lower parts. The radial guide vane has functions such as flow straightening, pressure recovery and balancing the stress of the unit.

[0003] At present, in addition to performance requirements, the running stability has become the primary problem of the vertical centrifugal pump unit with guide vanes. In order to meet the operation requirements, especially in the transition process such as starting and stopping, the unit often operates under the condition deviating from the design condition, and it is inevitable to pass through the hump region. The flow instability phenomena such as stall and secondary flow in the guide vane during the hump region operation easily lead to the increase of pressure pulsation, the increase of axial force and radial force, and other hydraulic instabilities, which further leads to the vibration of the entire pump system, and seriously affects the safe and stable operation of the unit. At present, the fixed guide vane structure used in the traditional vertical centrifugal pump is generally composed of multiple hydrofoil structures symmetrically distributed in the circumferential direction between the impeller and the volute, and the hydraulic stability problem of the hump region is not considered. In order to improve the hydraulic stability of the hump region of the vertical centrifugal pump, the present application proposes a gradually changing guide vane structure, which not only improves the hump characteristics of the vertical centrifugal pump, but also improves the unsteady stress characteristics of the hydraulic components. The present application has important significance for improving the hydraulic stability of the vertical centrifugal pump in the hump region 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 the volute type centrifugal pump, and proposes a structure of combination of large and small guide vanes to slow down the hump phenomenon under the small flow condition of the centrifugal pump. However, the invention only considers how to slow down the hump, and does not consider that the guide vane structures of different sizes will increase and unevenly distribute the radial force and axial force of the hydraulic components, thereby causing greater threat to the running stability of the rotor system of the unit.

[0005] SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a vertical centrifugal pump for improving the hydraulic stability in the hump area, which can not only inhibit the hump characteristics of the pump at a small flow rate, but also reduce the axial force and radial force acting on the impeller and guide vane in the hump area, thereby comprehensively improving the hydraulic stability of the vertical centrifugal pump with guide vane in the hump area from multiple aspects.

[0007] The present application achieves the above technical object through the following technical means.

[0008] A vertical centrifugal pump for improving the hydraulic stability in the hump area, comprising a spiral volute and a centrifugal impeller, wherein the centrifugal impeller is located in the spiral volute, a radial guide vane with a water wing type having a number of blades that is a prime number of the number of blades of the centrifugal impeller is arranged between the outlet of the centrifugal impeller and the inlet of the spiral volute; the chord length, cross-sectional area and maximum thickness of each radial guide vane increase along the cross-sectional area of the spiral volute, and the radial guide vane with the minimum chord length, cross-sectional area and maximum thickness is located at the position with the minimum cross-sectional area of the spiral volute; the inlet diameter and inlet angle of each radial guide vane are consistent.

[0009] Further, the radial guide vanes are divided into standard guide vanes and incremental 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 incremental guide vane assemblies increase linearly along the circumferential direction of the spiral volute, the cross-sectional area of the radial guide vanes in the incremental guide vane assemblies increases nonlinearly along the circumferential direction of the spiral volute, and the growth trend of the chord length, maximum thickness and cross-sectional area of the radial guide vanes in the incremental guide vane assemblies corresponds to the growth trend of the cross-sectional area of the spiral volute; the radial guide vane with the minimum chord length, cross-sectional area and maximum thickness in the incremental guide vane assemblies is arranged at the position with the minimum cross-sectional area of the spiral volute adjacent to the standard guide vanes.

[0010] Further, the chord length of the radial guide vane with the minimum value is 0.5 times the chord length of the standard guide vane, the cross-sectional area of the radial guide vane with the minimum value is 0.25 times the cross-sectional area of the standard guide vane, and the maximum thickness of the radial guide vane with the minimum value is 0.5 times the maximum thickness of the standard guide vane.

[0011] Further, the radial guide vanes in the incremental guide vane assemblies are uniformly arranged at intervals of 360 / N° along the circumferential direction of the spiral volute starting from the radial guide vane with the minimum value; the chord length L x increases linearly according to the following formula:

[0012] wherein: L xL is the chord length of the xth radial vane, x∈[2, ……, N-1], N is the total number of vane blades, L N L is the chord length of the standard vane.

[0013] Further, the radial vanes in the incremental vane assembly are uniformly arranged at an interval of 360 / N° along the circumferential direction of the increasing cross-sectional area of the spiral volute, starting from the minimum radial vane; the maximum thickness δ x linearly increases according to the following formula:

[0014] wherein: δ x is the maximum thickness of the xth radial vane, x∈[2, ……, N-1], N is the total number of vane blades, δ N is the maximum thickness of the standard vane.

[0015] Further, the radial vanes in the incremental vane assembly are uniformly arranged at an interval of 360 / N° along the circumferential direction of the increasing cross-sectional area of the spiral volute, starting from the minimum radial vane; the cross-sectional area A x of the xth radial vane in the incremental vane assembly non-linearly increases according to the following formula: 2

[0016] wherein: A x is the cross-sectional area of the xth radial vane, x∈[2, ……, N-1], N is the total number of vane blades, a, b and c are coefficients and are obtained from the following equation set:

[0017] wherein: A N is the cross-sectional area of the standard vane.

[0018] Further, the chord length, cross-sectional area and maximum thickness of the standard vane are obtained according to the outlet diameter, outlet setting angle of the centrifugal impeller and the inlet diameter, cross-sectional area of the spiral volute.

[0019] The present application has the following advantages:

[0020] ​1. The vertical centrifugal pump for improving the hydraulic stability in the hump region, wherein the chord length, cross-sectional area and maximum thickness of the plurality of radial vanes are increased along the cross-sectional area of the spiral volute, so as to improve the comprehensive hydraulic stability of the vertical centrifugal pump with vanes in the hump region.

[0021] 2. The vertical centrifugal pump for improving the hydraulic stability in the hump region, wherein the incremental vane assembly improves the hydraulic matching between the vanes, impeller and volute, and solves the problem that the traditional vane structure is prone to unstable flow at low flow rate, thereby suppressing the hump characteristics of the vertical centrifugal pump at low flow rate, improving the hydraulic efficiency of the pump at low flow rate and saving energy consumption.

[0022] 3. The vertical centrifugal pump for improving the hydraulic stability in the hump region, wherein the growth trend of the chord length, cross-sectional area and maximum thickness of the vanes in the incremental vane assembly corresponds to the growth trend of the cross-sectional area of the volute, so as to greatly improve the matching between the vanes and the volute, thereby effectively improving the unsteady characteristics of the axial force and radial force of the impeller and vanes in the hump region while suppressing the hump characteristics, mainly reflected in that the amplitude of the axial force and radial force of the impeller and vanes changes with time is significantly reduced, and the force distribution with time is more uniform, that is, the axial force and radial force are better balanced, so as to ensure the safe and stable operation of the rotor system and improve the comprehensive hydraulic stability of the vertical centrifugal pump unit in the hump region.

[0023] 4. The vertical centrifugal pump for improving the hydraulic stability in the hump region, wherein the incremental vane assembly improves the hydraulic matching between the vanes, impeller and volute, and can significantly improve the flow separation and flow passage blockage in the vanes, thereby reducing the range of the hump region, suppressing the hump characteristics curve and improving the efficiency, so that the centrifugal pump unit can realize high-efficiency and stable operation in a larger flow range.

[0024] 5. The vertical centrifugal pump for improving the hydraulic stability of the hump region in the application, the incremental guide vane assembly can effectively improve the unsteady characteristics of the axial force and radial force on the impeller and guide vane in the hump region while suppressing the hump characteristics, mainly reflected in the fact that the amplitude of the axial force and radial force on the impeller and guide vane changes significantly over time, wherein the maximum amplitude of the axial force on the incremental guide vane assembly is reduced by 24% compared with the size guide vane structure in the prior art, and reduced by 41% compared with the standard guide vane; the maximum amplitude of the radial force on the incremental guide vane assembly is reduced by 10% compared with the standard guide vane and the size guide vane structure; the maximum amplitude of the radial force on the impeller when the incremental guide vane assembly is used is reduced by 32% compared with the standard guide vane, and reduced by 19% compared with the size guide vane structure; the maximum amplitude of the axial force on the impeller when the incremental guide vane assembly is used is reduced by 25% compared with the standard guide vane, and reduced by 4% compared with the size guide vane structure. Therefore, when the incremental guide vane assembly is used, the fluctuations of the axial force and radial force on the impeller and guide vane are significantly reduced, thereby significantly improving the hydraulic stability of the vertical centrifugal pump unit in the hump region. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. The drawings in the following description are some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Fig. 1 is a structural schematic diagram of the vertical centrifugal pump for improving the hydraulic stability of the hump region in the application.

[0027] Fig. 2 is an installation schematic diagram of the radial guide vane in the application.

[0028] Fig. 3 is a position schematic diagram of the standard guide vane and the incremental guide vane assembly in the application.

[0029] Fig. 4 is a parameter schematic diagram of the radial guide vane airfoil in the application.

[0030] Fig. 5 is a curve of the incremental law of the chord length of the guide vane in the incremental guide vane assembly in the application.

[0031] Fig. 6 is a curve of the incremental law of the cross-sectional area of the guide vane in the incremental guide vane assembly in the application.

[0032] Fig. 7 is a curve of the incremental law of the maximum thickness of the guide vane in the incremental guide vane assembly in the application.

[0033] Fig. 8 is a flow-head curve of the vertical centrifugal pump with the standard guide vane, the combined guide vane and the guide vane in the application under different working conditions in the hump region.

[0034] Fig. 9 is a flow rate-efficiency curve of the vertical centrifugal pump with the standard guide vanes, the combined guide vanes and the guide vanes of the present application under different working conditions of the hump region.

[0035] Fig. 10 is a schematic diagram of the streamline distribution in the standard guide vanes, the combined guide vanes and the guide vanes of the present application under the hump condition.

[0036] Fig. 11 is a schematic diagram of the radial force distribution of the standard guide vanes, the combined guide vanes and the guide vanes of the present application under the hump condition.

[0037] Fig. 12 is a schematic diagram of the axial force distribution of the standard guide vanes, the combined guide vanes and the guide vanes of the present application under the hump condition.

[0038] Fig. 13 is a comparison diagram of the stress amplitude of the impeller and the guide vanes of the standard guide vanes, the combined guide vanes and the guide vanes of the present application under the hump condition.

[0039] In the drawings:

[0040] 1 - elbow-shaped inlet pipe, 2 - centrifugal impeller, 3 - radial guide vanes; 3-1 - standard guide vanes; 4 - spiral volute. DETAILED DESCRIPTION

[0041] Embodiments of the present application are described in detail below with reference to the attached drawings, wherein like or similar elements are denoted by the same or similar reference signs throughout the drawings. The embodiments described below are examples for explaining the present application and are not intended to be limiting of the present application.

[0042] In the description of the present application, it is to be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, and are merely for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0043] In this application, unless otherwise clearly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and other terms should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] As shown in FIG. 1 and FIG. 2, the vertical centrifugal pump for improving the stability of the hump area of the present application comprises 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 in communication with the inlet of the spiral volute 4, the centrifugal impeller 2 is located in the spiral volute 4, and the outlet of the centrifugal impeller 2 is provided with a radial guide vane 3 of hydrofoil type with the number of blades being a prime number of the number of blades of the centrifugal impeller 2 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 a plurality of radial guide vanes 3 are all increasing along the cross-sectional area of the spiral volute 4, and the chord length, cross-sectional area and maximum thickness of the radial guide vane 3 with the smallest value are located at the smallest cross-sectional area of the spiral volute 4, and the inlet diameter and inlet installation angle of a plurality of radial guide vanes 3 are consistent.

[0045] As shown in FIG. 3 and FIG. 4, the several radial vanes 3 are divided into a standard vane 3-1 and an incremental vane assembly, the standard vane 3-1 is located at the tongue of the spiral volute 4, the chord length and the maximum thickness of the radial vanes 3 in the incremental vane assembly increase linearly along the circumferential direction of the spiral volute 4, the cross-sectional area of the radial vanes 3 in the incremental vane assembly increases nonlinearly along the circumferential direction of the spiral volute 4, the growth trend of the chord length, the maximum thickness and the cross-sectional area of the radial vanes 3 in the incremental vane assembly corresponds to the growth trend of the sectional area of the spiral volute 4; the radial vane 3 with the minimum chord length, cross-sectional area and maximum thickness in the incremental vane assembly is arranged at the position with the minimum sectional area of the spiral volute 4 adjacent to the standard vane 3-1. The implementation is as shown in FIG. 2, in which the number of radial vanes 3 is 13, the radial vane 3 with the serial number 1' is the radial vane 3 with the minimum value, the radial vane 3 with the serial number 13' is the standard vane 3-1, and the radial vanes 3 with the serial numbers 1' to 12' form the incremental vane assembly. The incremental vane assembly of the present application improves the hydraulic matching between the vanes and the impeller and the volute, improves the problem that the traditional vane structure is prone to unstable flow at low flow, thereby inhibiting the hump characteristics of the vertical centrifugal pump at low flow, improving the hydraulic efficiency of the pump at low flow and saving energy consumption. The growth trend of the chord length, the cross-sectional area and the maximum thickness of the vanes in the incremental vane assembly corresponds to the growth trend of the sectional area of the volute, which greatly improves the matching between the vanes and the volute, the amplitude of the axial force and the radial force of the impeller and the vanes changes with time, and the force size is more evenly distributed with time, that is, the axial force and the 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.

[0046] The chord length of the radial vane 3 with the minimum value is 0.5 times the chord length of the standard vane 3-1, the cross-sectional area of the radial vane 3 with the minimum value is 0.25 times the cross-sectional area of the standard vane 3-1, and the maximum thickness of the radial vane 3 with the minimum value is 0.5 times the maximum thickness of the standard vane 3-1.

[0047] The radial vanes 3 in the incremental vane assembly are uniformly arranged at intervals of 360 / N° along the circumferential direction of the spiral volute 4 starting from the radial vane 3 with the minimum value; the chord length L x increases linearly according to the following formula:

[0048] wherein: L x is the chord length of the xth radial vane 3, x∈[2,……,N-1], N is the total number of vane blades, L N is the chord length of the standard vane 3-1.

[0049] the maximum thickness δ of the xth radial guide vane 3 in the incremental guide vane assembly x is linearly increased according to the following formula:

[0050] wherein δ x is the maximum thickness of the xth radial guide vane 3, x ∈ [2, …, N-1], N is the total number of guide vane blades, δ N is the maximum thickness of the standard guide vane 3-1.

[0051] the cross-sectional area A of the xth radial guide vane 3 in the incremental guide vane assembly is non-linearly increased according to the following formula: x = ax 2 + bx + c

[0052] wherein A x is the cross-sectional area of the xth radial guide vane 3, x ∈ [2, …, N-1], N is the total number of guide vane blades, a, b and c are all coefficients and are obtained from the following equation set:

[0053] wherein A N is the cross-sectional area of the standard guide vane 3-1.

[0054] Embodiment 1

[0055] The outer diameter of the centrifugal impeller 2 in the embodiment is 360 mm, the rotating speed is 1150 r / min, the design working condition 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 pieces of water wing-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 is 13, which is a prime number with the number of impeller blades 7, as shown in FIG. 2. Fluids enter the radial guide vanes 3 under the acceleration of centrifugal force of the centrifugal impeller 2. The radial guide vanes 3 play a key role in connecting the upper and lower parts. The radial guide vanes can make the flow pattern of the fluid entering the volute more smooth, reduce the flow rate, convert kinetic energy into pressure energy, and balance the radial force on the unit at the same time.

[0056] As shown in FIGS. 2 and 3, a plurality of radial guide vanes 3 are divided into standard guide vanes 3-1 and an incremental guide vane assembly. The standard guide vanes 3-1 are located at the tongue of the spiral volute 4. According to the design parameters of the outlet of the centrifugal impeller 3 and the inlet of the spiral volute 4, the parameters of the standard guide vanes 3-1 (i.e. the radial guide vanes 3 with serial number 13’ in FIG. 2) can be obtained by using the existing design method. For example, the guide vane inlet diameter of the standard guide vanes 3-1 is 372 mm, the axial width of the standard guide vanes 3-1 is 75 mm, the inlet setting angle of the standard guide vanes 3-1 is 30°, the airfoil chord length L N of the standard guide vanes 3-1 is 66.33 mm, and the airfoil cross-sectional area AN = 487.53 mm 2 , the maximum thickness δ of the standard guide vane 3-1 N = 9.57 mm.

[0057] Referring to FIG. 3, a radial guide vane 3 (i.e., the radial guide vane 3 with reference number 1' in FIG. 2) with the minimum chord length, cross-sectional area and maximum thickness is arranged at a position adjacent to the standard guide vane 3-1 where the volute cross-sectional area is small. The inlet diameter, inlet setting angle and axial width of the radial guide vane 3 with reference number 1' are the same as those of the standard guide vane 3-1. The radial guide vane 3 with reference number 1' is arranged at an interval of 360 / 13 = 27.69° in the circumferential direction from the standard guide vane 3-1.

[0058] As shown in FIG. 2, the chord length of the radial guide vane 3 with the minimum value is 0.5 times the chord length of the standard guide vane 3-1, i.e., 33.165 mm; the cross-sectional area of the radial guide vane 3 with the minimum value is 0.25 times the cross-sectional area of the standard guide vane 3-1, i.e., 121.91 mm 2 ; and the maximum thickness of the radial guide vane 3 with the minimum value is 0.5 times the maximum thickness of the standard guide vane 3-1, i.e., 4.785 mm. Finally, the radial guide vane 3 with the minimum value (i.e., the radial guide vane 3 with reference number 1' in FIG. 2) can be obtained according to the above specific design parameters.

[0059] As shown in FIG. 2, starting from the radial guide vane 3 with the minimum value, the radial guide vanes 3 with the similar structure as the standard guide vane 3-1 are arranged at an interval of 360 / 13 = 27.69° in the circumferential direction from the radial guide vane 3 with the minimum value, and the chord length, cross-sectional area and maximum thickness of the radial guide vanes 3 gradually increase until the radial guide vane 3 with reference number 12', which is adjacent to the standard guide vane 3-1 and has a size close to or the same as that of the standard guide vane 3-1, because the volute cross-sectional area at the radial guide vane 3 with reference number 12' is almost the same as the volute cross-sectional area at the radial guide vane 3 with reference number 13'.

[0060] As shown in FIG. 3 and FIG. 5, the chord length L x of the radial guide vane 3 with reference number x in the incremental guide vane assembly increases linearly according to the following formula:

[0061] wherein L x is the chord length of the radial guide vane 3 with reference number x, x ∈ [2, …, N-1], and N is the total number of guide vanes, i.e., N = 13.

[0062] As shown in FIG. 3 and FIG. 6, the cross-sectional area of the radial guide vane 3 with reference number x in the incremental guide vane assembly increases non-linearly according to the following formula:

[0063] A x = ax 2 + bx + c

[0064] In the above formula, a, b and c can be obtained from the following equation group:

[0065] According to the above formula, A x = 0.886x 2 + 21.722x + 99.272;

[0066] As shown in FIG. 3 and FIG. 7, the maximum thickness δ x increases linearly according to the following formula:

[0067] In the embodiments provided by the present application, the design parameters of the radial vanes 3 with serial numbers from 2 to 12 are calculated by the above formula of the increasing rules of chord length, cross-sectional area and maximum thickness, wherein the chord length L and the maximum thickness δ of each vane profile increase linearly, and the cross-sectional area A of each vane profile increases in a non-linear mode. The growth trend of the chord length L, the cross-sectional area A and the maximum thickness δ of the increasing vane assembly corresponds to the growth trend of the area of the volute cross section.

[0068] For the convenience of description, the uniform standard vanes 3-1 in the prior art are referred to as standard vanes, and another prior art structure of combined vanes is referred to as combined vanes, as shown in FIG. 8. In the range of different flow rates Q / Q des = 0.6-0.8, the head variation curves of the standard vanes, the combined vanes and the vanes of the present application with respect to the flow rate are simulated based on the computational fluid dynamics (CFD) method. As shown in FIG. 8, when the flow rate of the standard vanes decreases from 0.75Q / Q des to 0.74Q / Q des , the head suddenly decreases and causes the positive slope of the flow rate-head curve, i.e. the hump phenomenon, when the flow rate decreases to 0.72Q / Q des and further to 0.71Q / Q des , the head slightly decreases for the second time, and when the flow rate further decreases to 0.66Q / Q des and further to 0.65Q / Q des , the head obviously decreases for the third time, so the vertical centrifugal pump with the standard vanes has multiple hump phenomena; the head of the vertical centrifugal pump with the combined vanes in the hump region is obviously higher than that of the standard vanes, and the first decrease condition is delayed to 0.71Q / Q des , but the head of the vertical centrifugal pump with the combined vanes decreases to 0.68Q / Q des ~0.65Q / Q desStill, the secondary hump phenomenon is observed, and the hump area range of the combined guide vane is reduced and the head is improved compared with the standard guide vane; when the guide vane structure of the application is adopted, the head of the hump area is further improved, and the hump phenomenon with a smaller positive slope is observed only in the flow range of 0.74Q / Q des ~0.72Q / Q des Therefore, the gradually-changing guide vane structure of the application can obviously reduce the range of the hump area, suppress the hump characteristic curve and improve the head, so that the centrifugal pump unit can realize stable operation in a larger flow range. In the figure, Q des is the flow rate at the design working condition.

[0069] As shown in FIG. 9, in the flow range of 0.6~0.8Q / Q des , the efficiency curves of the standard guide vane, the combined guide vane and the guide vane of the application with the flow rate are simulated based on the computational fluid dynamics (CFD) method. In the figure, the efficiency of the vertical centrifugal pump with the standard guide vane does not change much compared with the vertical centrifugal pump with the combined guide vane, but the efficiency of the vertical centrifugal pump with the guide vane structure of the application is obviously improved and uniformly rises, especially in the flow range of 0.73Q / Q des ~0.8Q / Q des , the efficiency is obviously improved, that is, the gradually-changing guide vane of the application improves the efficiency of the vertical centrifugal pump under the small flow working condition and reduces the fluctuation of the efficiency.

[0070] As shown in FIG. 10, the streamline distribution on the middle section of the guide vane of the standard guide vane, the combined guide vane and the guide vane of the application under the hump working condition is simulated based on the computational fluid dynamics (CFD) method, and it is seen from the figure that the flow blockage phenomenon exists at the mark A of the standard guide vane, and obvious flow separation and flow blockage are generated at the mark B; the flow blockage phenomenon at the mark A disappears in the combined guide vane structure, but the flow separation and blockage phenomenon still exist at the mark B; the streamline distribution at the marks A and B of the guide vane of the application is relatively smooth, and the flow blockage and flow separation phenomena disappear, which is because the matching of the hydraulic components is obviously improved, so the hump characteristic curve is obviously suppressed and the efficiency is improved.

[0071] As shown in FIG. 11, the distribution of the radial force vector points of the standard guide vane, the combined guide vane and the guide vane of the present application under the hump operating condition is simulated based on the computational fluid dynamics (CFD) method. It can be seen from the figure that the radial force vector points of the standard guide vane are very dispersed at different times, and the vector points at most times are far away from the origin, so the radial force fluctuation is large. The radial force vector points of the combined guide vane structure are more concentrated than those of the standard guide vane, but the vector points are basically concentrated in the region where the X and Y directions are both negative, so the fluctuation of the radial force of the combined guide vane structure is reduced, but the radial force is still unevenly distributed in the circumferential direction. The radial force vector points of the guide vane structure of the present application are more concentrated and closer to the origin than those of the standard guide vane and the combined guide vane structure, so the guide vane structure of the present application can effectively improve the unsteady characteristics of the radial force of the guide vane, i.e. the radial force is better balanced.

[0072] As shown in FIG. 12, the fluctuation of the axial force of the standard guide vane, the combined guide vane and the guide vane of the present application under the hump operating condition is simulated based on the computational fluid dynamics (CFD) method. It can be seen from the figure that the axial force of the standard guide vane and the combined guide vane structure fluctuates greatly with time and is not obviously periodic, and the fluctuation of the axial force of the guide vane structure of the present application with time is obviously reduced and is periodic, i.e. the unsteady characteristics of the axial force of the guide vane of the present application are obviously improved. The maximum amplitude of the axial force of the standard guide vane is ΔF N = 64.23 N, the maximum amplitude of the axial force of the combined guide vane structure is reduced to ΔF C = 49.54 N, 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 of the guide vane structure of the present application is further reduced to ΔF G = 37.72 N, which is reduced by 24% compared with the combined guide vane structure and by 41% compared with the standard guide vane, so the guide vane structure of the present application can greatly reduce the axial force.

[0073] As shown in Figure 13, the amplitude of the axial force and the radial force of the impeller and the guide vane under the camel hump working condition of the standard guide vane, the combined guide vane and the guide vane of the present application are counted and compared. It can be seen from the figure that the maximum amplitude of the radial force of the standard guide vane and the combined guide vane is basically the same, and the guide vane of the present application is significantly reduced, which is 10% lower than the combined guide vane structure; the maximum amplitude of the axial force of the guide vane of the present application is also significantly reduced compared with the standard guide vane and the combined guide vane, which is 26% lower than the standard guide vane structure and 13% lower than the combined guide vane structure; when the guide vane structure of the present application is used, the maximum amplitude of the radial force and the axial force of the impeller are significantly lower than those of the standard guide vane and the combined guide vane, wherein the maximum amplitude of the radial force of the impeller is 32% lower than that of the standard guide vane and 19% lower than that of the combined guide vane; the maximum amplitude of the axial force of the impeller is 25% lower than that of the standard guide vane and 4% lower than that of the combined guide vane. Therefore, the guide vane structure of the present application in the embodiment can effectively reduce the size and fluctuation of the axial force and the radial force of the impeller and the guide vane while suppressing the camel hump characteristics of the vertical centrifugal pump.

[0074] It should be understood that although the present specification is described according to various embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, and the skilled person should consider the specification as a whole, and the technical solutions in each embodiment can also be combined to form other embodiments which can be understood by the skilled person.

[0075] The above series of detailed descriptions are only specific descriptions of the feasible embodiments of the present application, and are not used to limit the protection scope of the present application, and any equivalent embodiments or changes made without departing from the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A vertical centrifugal pump for improving the hydraulic stability of the hump region, comprising a spiral volute (4) and a centrifugal impeller (2) located inside the spiral volute (4), characterized in that, The radial guide vanes (3) between the outlet of the centrifugal impeller (2) and the inlet of the spiral volute (4) are water wing type with the number of blades being prime to the number of blades of the centrifugal impeller (2); the chord length, cross-sectional area and maximum thickness of the radial guide vanes (3) increase along the cross-sectional area of the spiral volute (4), and the radial guide vane (3) with the minimum chord length, cross-sectional area and maximum thickness is located at the position with the minimum cross-sectional area of the spiral volute (4), and the inlet diameter and inlet setting angle of the radial guide vanes (3) are consistent.

2. The vertical centrifugal pump for improving the hydraulic stability of the hump region according to claim 1, characterized by, 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), the chord length and maximum thickness of the radial guide vanes (3) in the incremental guide vane assemblies 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 assemblies 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 assemblies corresponds to the growth trend of the cross-sectional area of the spiral volute (4), and the radial guide vane (3) with the minimum chord length, cross-sectional area and maximum thickness in the incremental guide vane assemblies is arranged at the position with the minimum cross-sectional area of the spiral volute (4) adjacent to the standard guide vanes (3-1).

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

4. The vertical centrifugal pump for improving the hydraulic stability of the hump region according to claim 2, characterized by, The radial vanes (3) in the incremental vane assembly are arranged uniformly at intervals of 360 / N° along the circumferential direction of the spiral volute (4) cross-sectional area increasing, starting from the minimum radial vane (3); the chord length L of the xth radial vane (3) in the incremental vane assembly is x Linearly increased according to the following formula: wherein: L x is the chord length of the xth radial vane (3), x ∈ [2, …, N-1], N being the total number of vane blades, L N is the chord length of the standard vane (3-1).

5. The vertical centrifugal pump for improving the hydraulic stability of the hump region according to claim 2, characterized by, The radial vanes (3) in the incremental vane assembly are arranged uniformly at intervals of 360 / N° along the circumferential direction of the spiral volute (4) cross-sectional area increasing, starting from the minimum radial vane (3); the maximum thickness δ of the xth radial vane (3) in the incremental vane assembly is x Linearly increased according to the following formula: wherein: δ x is the maximum thickness of the x-th radial vane (3), x ∈ [2, …, N-1], N being the total number of vane blades, δ N is the maximum thickness of the standard vane (3-1).

6. The vertical centrifugal pump for improving the hydraulic stability of the hump region according to claim 2, wherein The radial vanes (3) in the incremental vane assembly are arranged uniformly at intervals of 360 / N° along the circumferential direction of the spiral volute (4) cross-sectional area increasing, starting from the minimum radial vane (3); the cross-sectional area of the xth radial vane (3) in the incremental vane assembly is increased non-linearly according to the following formula: A x = ax 2 + bx + c wherein A x is the cross-sectional area of the xth radial vane (3), x e [2,..., N-1], N being the total number of vane blades, a, b and c being coefficients and obtained from the following system of equations: wherein A N is the cross-sectional area of the standard vanes (3-1).

7. The vertical centrifugal pump for improving the hydraulic stability of the hump region according to claim 2, characterized by, The inlet diameter, inlet setting angle, chord length, cross-sectional area and maximum thickness of the standard guide vanes (3-1) are derived according to the outlet diameter, outlet setting angle of the centrifugal impeller (2) and the inlet diameter and cross-sectional area of the spiral volute (4).

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