CN113236607B - Design method of large-scale engineering pump volute and volute thereof - Google Patents

Design method of large-scale engineering pump volute and volute thereof Download PDF

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CN113236607B
CN113236607B CN202110658301.3A CN202110658301A CN113236607B CN 113236607 B CN113236607 B CN 113236607B CN 202110658301 A CN202110658301 A CN 202110658301A CN 113236607 B CN113236607 B CN 113236607B
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volute
section
pump
guide vane
outlet
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CN113236607A (en
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李晓俊
宁望辉
马建峰
林言丕
朱祖超
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Zhejiang Sci Tech University ZSTU
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/426—Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for liquid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/44—Fluid-guiding means, e.g. diffusers
    • F04D29/445—Fluid-guiding means, e.g. diffusers especially adapted for liquid pumps
    • F04D29/448—Fluid-guiding means, e.g. diffusers especially adapted for liquid pumps bladed diffusers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/44—Fluid-guiding means, e.g. diffusers
    • F04D29/46—Fluid-guiding means, e.g. diffusers adjustable
    • F04D29/466—Fluid-guiding means, e.g. diffusers adjustable especially adapted for liquid fluid pumps
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/17—Mechanical parametric or variational design

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Abstract

The invention discloses a design method of a large-scale engineering pump volute and the volute, which comprises a volute outlet, a diffusion section (2), a throat (3), a movable guide vane (5), a fixed guide vane (6), an outlet guide vane (7) and a partition tongue (8), wherein the periphery of the movable guide vane is provided with a plurality of fixed guide vanes, the outlet guide vane is generally tangent to a pumping chamber inlet base circle D3, the inlet end of the outlet guide vane is provided with a section I, the partition tongue is provided with a section II, the section II is from the section II to the section I in the flow direction, the volute is an annular volute, and the flow areas of the cross sections of flow passages of the volute are basically the same. An annular volute structure with fixed guide vanes and movable guide vanes is adopted, and according to given working conditions, the geometric parameters of the volute, including the basic circle diameter D of the inlet of the pressurized water chamber, are determined based on a volute speed coefficient method3Width of inlet of pumping water chamber B3Radius of outer contour line of volute, number of movable vanes Z1Number of guide vanes z fixed2’The spread angle θ. The pressure pulsation and the radial force in the operation process of the pump can be reduced, and the operation safety and the stability of the pump under various working conditions are enhanced.

Description

Design method of large-scale engineering pump volute and volute thereof
Technical Field
The invention relates to the technical field of hydraulic engineering pump volutes and centrifugal pump volutes, in particular to a design method of a large-scale engineering pump volute and the volute.
Background
In recent years, the water conservancy and hydropower engineering in China is developed greatly, and a solid foundation is laid for the implementation of the sustainable development strategy in China while the requirement of the supply and demand of electric power energy in China is met. The volute is an important flow passage component of the centrifugal pump and has great influence on the efficiency index of the pump. When fluid enters a volute from an impeller, strong interaction can occur due to small clearance between the impeller and a volute partition tongue/tongue part, and high-amplitude low-frequency pressure pulsation is caused in a conventional spiral volute partition tongue area; meanwhile, as the geometric structure of the spiral volute is in an asymmetric form, when the lift and the flow are high, large pressure pulsation and radial force can be generated, large vibration or noise is generated, and the operation stability of the large hydraulic engineering pump is influenced. To solve this problem, chinese patent application publication No. CN201218236Y discloses a high-speed water pump volute, which contains a flat volute circular bottom with involute or archimedean volute and continuous side wall to form a continuous volute, and the pump is provided with a volute with a pump water inlet and a pump water outlet, the center of the volute is a water inlet, the continuous side wall is a water baffle, the lift height and the water flow are enhanced, and the volute has the characteristics of light weight, corrosion resistance, easy manufacture and low cost; chinese patent application publication No. CN111894903A discloses a volute of a serial single-stage centrifugal pump and a design method thereof, when different pump flows and the outer diameter of an impeller are designed, the axial wall thickness of a pump body close to a pump cover side can be the same, and the pump cover can be designed into a general shape. The pumping chamber adopts an axially asymmetric section, the center line is taken as a reference, the section close to the pump cover side is rectangular, the other side is in a right trapezoid shape, the deflection of the rotating shaft is effectively reduced, the sealing reliability is improved, and the vibration of the pump is reduced. However, although the production efficiency is improved, the mechanical strength is improved, and the pressure pulsation is reduced to a certain extent, the pump head with the trapezoidal or rectangular section is adopted and the efficiency is low. Therefore, there is a need to design a volute structure of a large hydraulic engineering pump, which can be widely applied and can stably and efficiently operate with smaller pressure pulsation and radial force.
The structure of the traditional volute comprises a volute body, wherein a water flow channel is arranged in the volute body, and the water flow channel generally consists of a water pumping chamber and a diffusion section. The starting end of the water pressing chamber is a separation tongue, the joint of the water pressing chamber and the diffusion section is a throat part, and the outlet of the diffusion section is a pump body outlet; the traditional pumping chamber is formed by connecting a group of sections, wherein the sections of the sections are gradually increased from the positions of the partition tongues to the throat part of the inlet of the diffusion section of the pump along the rotation direction of the impeller, and the cross section of the pumping chamber is an eccentric ellipse, a trapezoid or a semi-arc section so as to improve the pumping head and the efficiency of the pump.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a design method of a volute of a large-scale engineering pump and the volute thereof, which can reduce pressure pulsation and radial force in the operation process of the pump and enhance the operation safety and stability of the pump under various working conditions.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides a spiral case of large-scale engineering pump, it includes spiral case export (1), diffuser section (2), throat (3), fixed multithread way (4), activity stator (5), stator (6), export stator (7), separate tongue/tongue portion (8), runner clearance (9), the exit end of pressurized-water chamber is equipped with the diffuser section, the exit end of diffuser section has the spiral case export, connecting portion between pressurized-water chamber and the diffuser section are the throat, the impeller periphery is equipped with the diffuser, the diffuser includes a plurality of movable stator that distribute along circumference, constitute between diffuser section and the spiral case wall and separate the tongue, its characterized in that: the periphery of the movable guide vane (5) is provided with a plurality of fixed guide vanes (6), the fixed guide vanes divide a volute flow passage into fixed multi-flow passages, the center line/axis of the outlet guide vane is collinear/parallel with the center line/axis of the diffusion section, the outlet guide vane is generally tangent to a pumping chamber inlet base circle D3, a flow passage gap (9) is formed between the outlet end of the fixed guide vane and the inlet end of the fixed guide vane or the pumping chamber inlet base circle D3 on the radial inner side adjacent to the outlet guide vane, the inlet end of the outlet guide vane is provided with a section I, the partition tongue is provided with a section II, the volute is an annular volute from the section II to the section I in the flow direction, and the flow passage cross section flow areas of the volute are basically the same.
Further, the volute adopts a substantially eccentric oval section annular volute, and the size of the oval eccentric long part is 2-4 times of that of the short part in the long axis direction of the oval.
Further, the fixed guide vanes (6) are arc-shaped guide vanes, have different central angles, and the central angles are gradually increased from the section II to the section I in the flow direction; from section II to section I in the direction of flow, the downstream central angle is 1.05 to 1.25 times the upstream central angle.
Further, the flow passage gap (9) gradually increases from the section II to the section I in the flow direction; and the downstream flow channel gap is 1.05-1.2 times of the upstream flow channel gap from the section II to the section I in the flow direction.
Further, the fixed guide vane (6) has a downstream end (61) which is tapered conical or arc-shaped, the downstream end has a first groove (62) and a second groove (63), the first grooves are arranged on the radial inner side of the downstream end, and the second grooves are arranged on the radial outer side of the downstream end; the first groove and the second groove are of semicircular structures.
Further, the number of the first grooves (62) is larger than that of the second grooves (63), and the number of the first grooves is 1.5-3.0 times that of the second grooves.
Furthermore, the diffusion section is a pump body outlet, the diffusion section is from the throat to the volute outlet, the area of a water flow channel is gradually increased, and the section of the diffusion section comprises a shape consisting of a rectangle and/or an arc; the shape of the cross section of the water pumping chamber at the throat part is the same as and superposed with the shape of the end face of the diffuser section, and the structure ensures the smooth transition of the water pumping chamber and the diffuser section.
A design method of a volute of a large-scale engineering pump is characterized in that an annular volute structure with fixed guide vanes and movable guide vanes is adopted, and geometric parameters of the volute are determined based on a volute speed coefficient method according to given working conditions, wherein the geometric parameters include a base circle diameter D of an inlet of a pumping chamber3Width of inlet of pumping water chamber B3Radius of outer contour line R of volute, number of movable vanes Z1Number of guide vanes Z fixed2Angle of divergence θ;
the method comprises the following design steps:
(1) Design of base diameter D of inlet of pumping chamber3：
D3＝D2+2b2
In the formula:
b2-movable guide vane radius, mm;
D2-pump impeller outer diameter, mm;
D3-pump water chamber inlet base circle diameter, mm;
(2) design pump pressure water chamber inlet width B3：
B3＝B2+0.05D3
In the formula:
B2-pump impeller outlet axial width, mm;
D3-pump water chamber inlet base circle diameter, mm;
B3-width of inlet of pumping water chamber, mm;
(3) designing the outer contour line radius R of the volute:
Figure BDA0003113146920000041
In the formula:
AI-area value of volute I cross-section, mm;
r-the radius of the outer contour line of the volute chamber, mm;
(4) design of number of movable guide vanes Z1：
Z1＝8～14
In the formula:
Z1-number of active guide vanes;
(5) design of fixed number of guide vanes Z2：
Z2＝3～5
In the formula:
Z2-a fixed number of guide vanes;
(6) designing a diffusion angle of a diffusion section:
Figure BDA0003113146920000042
in the formula:
AI-area value of volute I section, mm;
DS-volute exit diameter, mm;
l-the length of the volute diffusion section is mm;
theta-spread angle, °;
the theta is adopted to be 6-12 degrees.
The invention has the beneficial technical effects that:
(1) by adopting the structure of the annular volute, compared with a typical spiral volute, the annular volute has symmetrical overflowing flow channels, and a larger gap is formed between the partition tongue and the impeller outlet, so that the traditional volute is replaced by the annular volute, the pump pressure pulsation and the radial force can be reduced, and the operation stability is improved. The clearance between the periphery of the impeller and the volute partition tongue is increased, the volute partition tongue structure has the advantages that the collision of water flow on the volute partition tongue is reduced, and the increase of the clearance between the partition tongue and the impeller can reduce pressure pulsation and integral radial force.
(2) By further designing the stay vanes with different central angles and increasing the central angle from section II to section I in the flow direction. The flow channel gap gradually increases from section II to section I in the flow direction. The pressure pulsation and the radial force in the operation process of the pump can be further reduced, the corner vortex at the outlet of the fixed guide vane is reduced, the pressure fluctuation and the pressure loss of the annular volute are reduced, and the operation safety and the stability of the pump under various working conditions are enhanced. According to the invention, through the design of the first groove and the second groove, the corner vortex at the outlet of the fixed guide vane can be further reduced, and the pressure fluctuation and pressure loss of the annular volute are reduced, so that the operation safety and stability of the pump under various working conditions are enhanced.
(3) The double rows of guide vanes (movable guide vanes and fixed guide vanes) are arranged in the volute to collect high-speed liquid thrown out by the impeller, uniformly guide the high-speed liquid to the inlet or the extrusion chamber of the next-stage impeller, and can convert partial kinetic energy of the liquid into pressure energy in the guide vanes, thereby improving the efficiency of the pump. Compared with the fixed guide vane-free or single-row fixed guide vane, the hydraulic performance of the double-row guide vane is greatly improved. And the cross section of the volute is combined to adopt an eccentric oval cross section, the influence of the cross section shape on the hydraulic performance of the centrifugal pump is analyzed, and the oval cross section shape under the annular volute can provide a pump head higher than that of a trapezoid, a semicircle or a rectangle.
Drawings
FIG. 1 is a schematic diagram of the pump annular volute of the present invention;
FIG. 2 is a partial comparison of an annular volute and a spiral volute, (a) the annular volute and (b) the spiral volute;
FIG. 3 is a comparison of spiral volute and annular volute sections (A is spiral volute, B is annular volute);
FIG. 4 is a graph of annular volute versus spiral volute versus pump performance;
fig. 5 is a partial enlarged structural schematic view of another embodiment of the stay vane of the present invention.
In the figure: the volute comprises a volute outlet 1, a diffusion section 2, a throat 3, a fixed multi-channel 4, a movable guide vane 5, a fixed guide vane 6, an outlet guide vane 7, a partition tongue/tongue portion 8, a flow channel gap 9, a D2 impeller outer diameter, a D3 pumping chamber inlet base circle diameter, an R volute outer contour line radius, a downstream end/trailing edge end 61, a first groove 62 and a second groove 63.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1-2, a design method of a large-scale engineering pump volute and the volute thereof, which comprises a volute outlet 1, a diffuser 2, a throat 3, a fixed multi-channel 4, a movable guide vane 5, a fixed guide vane 6, an outlet guide vane 7, a tongue/tongue portion 8 and a channel gap 9, wherein the outlet end of a water pumping chamber is provided with the diffuser 2, the outlet end of the diffuser 2 is provided with the volute outlet 1, the connecting part between the water pumping chamber and the diffuser 2 is the throat 3, a diffuser is arranged on the periphery of an impeller, the diffuser comprises a plurality of movable guide vanes 5 distributed along the circumferential direction, and the tongue 8 is formed between the diffuser 2 and the volute wall, and is characterized in that: the periphery of the movable guide vane 5 is provided with a plurality of fixed guide vanes 6, the fixed guide vanes 6 divide a volute flow channel into fixed multi-flow channels 4, the center line/axis of the outlet guide vane 7 is collinear/parallel with the center line/axis of the diffusion section 2, the outlet guide vane 7 is generally tangent to a pumping chamber inlet base circle D3, a flow channel gap 9 is formed between the outlet end of the fixed guide vane 6 and the inlet end of the fixed guide vane 6 or the pumping chamber inlet base circle D3 which is adjacent to the outlet end of the fixed guide vane 6 and is arranged on the radial inner side, the inlet end of the outlet guide vane 7 is provided with a section I, a section II is arranged at the position of the partition tongue 8, the volute is an annular volute from the section II to the section I in the flow direction, and the flow areas of the flow channel cross sections of the volute are the same.
Further, as shown in fig. 3, the volute employs a substantially eccentric oval-section annular volute B, and the size of the oval eccentric long portion is 2 to 4 times, preferably 2.5 times, the size of the short portion in the oval long axis direction (X-axis direction).
Further, the stay vanes 6 are arc-shaped vanes, and the stay vanes 6 have the same or different central angles. Preferably, the stay vanes 6 have different central angles and the central angles increase progressively from section II to section I in the direction of flow. Specifically, from section II to section I in the flow direction, the downstream central angle is 1.05-1.25 times the upstream central angle.
Further, the flow passage gap 9 gradually increases from the section II to the section I in the flow direction. Specifically, the downstream flow channel gap 9 is 1.05-1.2 times the upstream flow channel gap 9 from section II to section I in the flow direction.
As shown in fig. 1, the volute has substantially the same cross-sectional flow area in the direction of flow from cross-section II to cross-section I, and then the clearance between the impeller outer circumference and the volute tongue 8 is increased, which has the advantage of reducing the impact of solid particles on the volute tongue, and the increased clearance between the tongue and the impeller reduces pressure pulsations and overall radial forces.
The diffusion section 2 is a pump body outlet, the diffusion section is from the throat 3 to the volute outlet 1, the area of a water flow channel is gradually increased, and the cross section of the diffusion section comprises a shape formed by a rectangle and/or an arc. The shape of the cross section of the water pumping chamber at the throat part 3 is the same as and superposed with the shape of the end surface of the diffuser section 2, and the structure ensures the smooth transition of the water pumping chamber and the diffuser section.
As shown in fig. 2, the annular volute has a larger, more uniform cross-sectional flow area than a conventional spiral volute. Too small a cross-sectional area of the volute can cause a hump in the pump head curve, thereby causing surge in the piping system. Under a rated working condition, the hydraulic performance is slightly reduced along with the increase of the overflowing area of the volute; when the operation of the pump deviates from the rated working condition, the hydraulic performance is improved under the condition that the flow area of the volute is larger; furthermore, as the volute flow area increases, the high efficiency zone will widen.
Instead of a conventional trapezoidal or semi-circular volute cross-section, the volute has a generally eccentric elliptical cross-section, which is advantageous for reducing pressure pulsations in the volute.
As shown in fig. 4 (a), by using the annular volute, the radial force can be reduced in the low flow rate range; also, these volutes produce more lift and efficiency when the pump is operating below the optimum efficiency point. The interaction between the impeller blades and the volute diaphragm is reduced in these volutes due to the larger tip clearance, and therefore the pressure distribution around the impeller becomes more uniform. At design time, the pressure distribution around the impeller is not uniform due to the constant cross-sectional area volute, which results in the point of minimum radial force being at low flow, not the design flow.
The radial force distribution is shown as a quadrilateral from (b) in fig. 4, coinciding with the impeller blade angle; in addition, along with the increase of the flow rate, the quadrangle rotates clockwise, the increase of the flow area of the volute can reduce the magnitude of radial force acting on the shaft, and particularly under the conditions of nominal flow rate and large flow rate, the vibration of the pump can be reduced, so that the operation stability of the pump is improved.
As shown in (c) of fig. 4, as can be seen from the broken line distribution of the fluctuation intensity coefficient in the center-of-annulus volute, the coefficient increases as a whole with an increase in flow rate; in addition, the polyline all shows four peaks, which correspond to the number of impeller blades, the equivalent deflection angle of the four peaks is 90 °, the maximum pressure pulsation occurs at about 30 ° behind the volute tongue, which means that the interaction between the impeller trailing edge and the volute tongue is the main cause of the pressure pulsation in the volute. Additionally, the increase in volute flow area will mitigate pressure pulsations in the volute regardless of the operating conditions of the pump.
Preferably, the stator vanes 6 are further designed to have different central angles, and the central angles gradually increase from section II to section I in the flow direction. The flow channel gap 9 gradually increases from section II to section I in the flow direction. The pressure pulsation and the radial force in the operation process of the pump can be further reduced, the corner vortex at the outlet of the fixed guide vane is reduced, the pressure fluctuation and the pressure loss of the annular volute are reduced, and the operation safety and the stability of the pump under various working conditions are enhanced.
As shown in fig. 5, in an embodiment, the stationary vane 6 has a downstream/trailing end 61, the downstream/trailing end 61 is tapered or curved, the downstream end 61 has a first groove 62 and a second groove 63, the first grooves 62 are disposed on a radially inner side of the downstream end 61, and the second grooves 63 are disposed on a radially outer side of the downstream end 61; the first groove 62 and the second groove 63 are semicircular structures. Through the design of the first groove 62 and the second groove 63, the corner vortex at the outlet of the fixed guide vane can be further reduced, and the pressure fluctuation and the pressure loss of the annular volute are reduced, so that the operation safety and the stability of the pump under various working conditions are enhanced.
Further, the number of the first grooves 62 is greater than the number of the second grooves 63, and preferably, the number of the first grooves 62 is 1.5 to 3.0 times the number of the second grooves 63.
A design method of a volute of a large-scale engineering pump adopts an annular volute structure with fixed guide vanes and movable guide vanes, and determines geometric parameters of the volute based on a volute speed coefficient method according to given working conditions, wherein the geometric parameters comprise a basic circle diameter D of an inlet of a pumping chamber3Width of inlet of pumping water chamber B3Radius of outer contour line of volute, number of movable vanes Z1Fixed number of guide vanes z 2Angle of divergence θ;
the method comprises the following design steps:
(1) design of base diameter D of inlet of pumping chamber3：
D3＝D2+2b2
In the formula:
b2-movable guide vane halvesDiameter, mm;
D2-pump impeller outer diameter, mm;
D3-pump water chamber inlet base circle diameter, mm;
(2) design pump pressure water chamber inlet width B3：
B3＝B2+0.05D3
In the formula:
B2-pump impeller outlet axial width, mm;
D3-pump water chamber inlet base circle diameter, mm;
B3-width of inlet of pumping water chamber, mm;
(3) designing the outer contour line radius R of the volute:
Figure BDA0003113146920000091
in the formula:
AI-area value of volute I section, mm;
r-the radius of the outer contour line of the volute chamber, mm;
(4) design of number of movable vanes Z1：
Z1＝8～14
In the formula:
Z1-number of active guide vanes;
(5) design of fixed number of guide vanes Z2：
Z2＝3～5
In the formula:
Z2-a fixed number of guide vanes;
(6) designing a diffusion angle of a diffusion section:
Figure BDA0003113146920000101
in the formula:
AI-area value of volute I section, mm;
DS-volute exit diameter, mm;
l-the length of the volute diffusion section is mm;
theta-spread angle, °;
the theta is adopted to be 6-12 degrees.
In order to reduce the volume of the pump, the diameter of a discharge pipeline and the loss of the pipeline, thereby reducing the lift of the pump, reducing the power of the pump, saving energy, reducing the operation cost, and taking the discharge caliber to be smaller than the suction caliber. The diameter of the outlet of the pump is preliminarily determined and then should be rounded according to the diameter series of the standard pipeline, and the height L of the diffusion pipe/diffusion section should be measured to a small value as much as possible under the condition of ensuring the diffusion angle, processing and bolt connection so as to reduce the size of the pump.
The invention has the beneficial technical effects that:
(1) compared with a typical spiral volute, the annular volute is provided with symmetrical overflowing flow passages, a larger gap is formed between the partition tongues and the impeller outlet, the annular volute is used for replacing the traditional volute, the pump pressure pulsation and the radial force can be reduced, and the operation stability is improved. The clearance between the periphery of the impeller and the volute partition tongue is increased, the volute partition tongue has the advantages that the collision of water flow on the volute partition tongue is reduced, and the increase of the clearance between the partition tongue and the impeller can reduce pressure pulsation and integral radial force.
(2) By further designing the stay vanes with different central angles and increasing the central angle in the flow direction from section II to section I. The flow passage gap gradually increases from section II to section I in the flow direction. Pressure pulsation and radial force in the operation process of the pump can be further reduced, corner vortex at the outlet of the fixed guide vane is reduced, pressure fluctuation and pressure loss of the annular volute are reduced, and operation safety and stability of the pump under various working conditions are enhanced. According to the invention, through the design of the first groove and the second groove, the corner vortex at the outlet of the fixed guide vane can be further reduced, and the pressure fluctuation and the pressure loss of the annular volute are reduced, so that the operation safety and the stability of the pump under various working conditions are enhanced.
(3) The double rows of guide vanes (movable guide vanes and fixed guide vanes) are arranged in the volute to collect high-speed liquid thrown out by the impeller, uniformly guide the high-speed liquid to the inlet or the extrusion chamber of the next-stage impeller, and can convert partial kinetic energy of the liquid into pressure energy in the guide vanes, thereby improving the efficiency of the pump. Compared with the fixed guide vane-free or single-row fixed guide vane, the hydraulic performance of the double-row guide vane is greatly improved. And the cross section of the volute is combined to adopt an eccentric oval cross section, the influence of the cross section shape on the hydraulic performance of the centrifugal pump is analyzed, and the oval cross section shape under the annular volute can provide a pump head higher than that of a trapezoid, a semicircle or a rectangle.
The above-described embodiments are illustrative of the present invention and not restrictive thereof, and it should be understood that various changes, modifications, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims (8)

1. The utility model provides a spiral case of large-scale engineering pump, it includes spiral case export (1), diffuser section (2), throat (3), fixed multithread way (4), movable guide vane (5), fixed guide vane (6), export guide vane (7), separate tongue/tongue portion (8), runner clearance (9), the exit end of pressurized-water chamber is equipped with the diffuser section, the exit end of diffuser section has the spiral case export, connecting portion between pressurized-water chamber and the diffuser section are the throat, the impeller periphery is equipped with the diffuser, the diffuser includes a plurality of movable guide vanes that distribute along circumference, constitute between diffuser section and the spiral case wall and separate the tongue, its characterized in that: the periphery of the movable guide vane (5) is provided with a plurality of fixed guide vanes (6), the fixed guide vanes divide a volute flow channel into fixed multi-flow channels, the center line/axis of the outlet guide vane is collinear/parallel with the center line/axis of the diffusion section, the outlet guide vane is generally tangent to a pumping chamber inlet base circle D3, a flow channel gap (9) is formed between the outlet end of the fixed guide vane and the inlet end of the fixed guide vane or the pumping chamber inlet base circle D3 of the radially inner side adjacent to the outlet guide vane, the inlet end of the outlet guide vane is provided with a section I, a section II is arranged at the position of the partition tongue, the volute is an annular volute from the section II to the section I in the flow direction, and the flow area of the flow channel cross section of the volute is basically the same.
2. The volute of a large-scale working pump according to claim 1, wherein the volute is a substantially eccentric oval-section annular volute, and the size of the oval eccentric long portion is 2-4 times that of the oval short portion in the long axis direction of the oval.
3. Volute for large industrial pumps according to claim 2, characterized in that the stay vanes (6) are arc-shaped stay vanes having different central angles and increasing in the direction of flow from section II to section I; and the central angle downstream is 1.05-1.25 times the central angle upstream from section II to section I in the flow direction.
4. Volute for large industrial pumps according to claim 3, characterized in that the flow gap (9) increases in the direction of flow from section II to section I; and the flow channel gap at the downstream is 1.05-1.2 times of the flow channel gap at the upstream from the section II to the section I in the flow direction.
5. Volute for large-scale process pumps according to claim 4, characterized in that the stator vane (6) has a downstream/trailing end (61) which is tapered or curved, the downstream end having a first groove (62) and a second groove (63), the first grooves being arranged on the radially inner side of the downstream end and the second grooves being arranged on the radially outer side of the downstream end; the first groove and the second groove are of semicircular structures.
6. Volute for large pumps according to claim 5, characterized in that the number of first grooves (62) is greater than the number of second grooves (63) and that the number of first grooves is 1.5-3.0 times the number of second grooves.
7. The volute of a large-scale engineering pump according to claim 5, wherein the diffuser section is a pump body outlet, the diffuser section is from a throat to the volute outlet, the area of the water flow passage is gradually increased, and the cross section of the diffuser section comprises a shape consisting of a rectangle and/or a circular arc; the shape of the cross section of the water pumping chamber at the throat part is the same as and superposed with the shape of the end face of the diffuser section, and the structure ensures the smooth transition of the water pumping chamber and the diffuser section.
8. The design method of the volute of the large-scale engineering pump according to claim 1, wherein the annular volute structure with the fixed guide vanes and the movable guide vanes is adopted, and the geometric parameters of the volute, including the inlet base circle diameter D of the pumping chamber, are determined based on a volute speed coefficient method according to given working conditions3Width of inlet of pumping water chamber B3Radius of outer contour line of volute, number of movable vanes Z1Fixed number of guide blades Z2The spread angle θ;
the method comprises the following design steps:
(1) design of the base diameter D of the inlet of the pumping chamber 3：
D3＝D2+2b2
In the formula:
b2-movable guide vane radius, mm;
D2-pump impeller outer diameter, mm;
D3-pump chamber inlet base circle diameter, mm;
(2) design pump press water chamber inlet width B3：
B3＝B2+0.05D3
In the formula:
B2-pump impeller outlet axial width, mm;
D3-pump chamber inlet base circle diameter, mm;
B3-width of inlet of pumping water chamber, mm;
(3) designing the outer contour line radius R of the volute:
Figure FDA0003113146910000031
in the formula:
AI-area value of volute I section, mm;
r-the radius of the outer contour line of the volute chamber, mm;
(4) design of number of movable vanes Z1：
Z1＝8～14
In the formula:
Z1-number of active guide vanes;
(5) design of fixed number of guide vanes Z2：
Z2＝3～5
In the formula:
Z2-a fixed number of guide vanes;
(6) designing a diffusion angle of a diffusion section:
Figure FDA0003113146910000032
in the formula:
AI-area value of volute I section, mm;
DS-volute exit diameter, mm;
l-the length of the volute diffusion section is mm;
theta-spread angle, °;
the theta is adopted to be 6-12 degrees.
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