高速泵结构比较文章图Word文件下载.docx

1、Wu Jian-boChemical Machinery Research Institute, Hefei University of Technology, Hefei, China, 23009gmriwjb2000He Yu-jieHeyujie301Li QianghfliqiangABSTRACTIn order to study the effect of the structural style of high-speed pump on internal flow, 4 types high-speed pump of different structural style a

2、re selected for comprehensive analysis，S-A turbulence model and SIMPLIEC algorithm are adopted for numerical simulation of internal flow. By comprehensively comparing the static pressure, total pressure, sectional velocity vector and flow path line, two types of high-speed pumps with cylindrical-bla

3、de impeller matching nozzle type pump casing have relatively ideal pressure field and flow condition, can reduce hydraulic loss. The comprehensive performance of 4 types of high-speed pump is predicted through computational simulation, the high-speed pump with open cylindrical-blade impeller matchin

4、g nozzle type pump casing has most excellent performance, indicating the structural style of high-speed pump has effect on its internal flow and performance. Keywords: high-speed pump, structural style, numerical simulation, flow analysis, performance. NOMENCLATURE Impeller diameter，m Impeller width

5、 at outlet ，m Number of long/short blades Basic circle of volute casing，m Throat diameter of diffuser，m Length of diffusion section of diffuser，m Diffusion angle，0C； Total pressure Static pressure Absolute speed Total pressure at impeller inlet Total pressure at outlet of pump casing Sum of moments

6、about Z-axisINTRODUCTION High-speed partial emission pump is the one with special construction and low or ultra-low specific speed （501）, it has the features of small flow, high head, high speed, simple construction, high reliability, convenient manufacture and repair, etc.2, it is widely applied in

7、 the field of aviation, spray irrigation, fire fighting, petrochemical engineering etc. The medium enters the suction chamber of the pump and is discharged after passing through open impeller, annular volute casing and nozzle type diffuser, the internal flow of the pump is very complex and belongs t

8、o unsteady flow3. Internal flow differs for different structural style of high-speed pump and the hydraulic performance differs somewhat; in literature 46 only single-item numerical simulation is carried out on impeller, internal flow passage and volute, thus cannot truly reflects the overall flow c

9、ondition of high-speed pump, whereas literature 7 conducted fully 3D unsteady computational simulation on the entire constant-speed centrifugal pump, in this paper focus is placed on analysis and comparison of internal flow characteristics of 4 different structures of high-speed pump, and internal f

10、low analysis and numeric simulation study are carried out on different structures of high-speed pump for the common 4 combinations of impeller and nozzle style casing with the turbulence models of Navier-Stokes and Realizable equations for 3D turbulent flow using Fluent software, wall-function metho

11、d and mesh technique for sliding between impeller and pump casing and S-A turbulence model and implicit correction SIMPLIEC algorithm of second-order central difference scheme. STRUCTURAL STYLE OF IMPELLER AND NOZZLE STYLE PUMP CASING4 different structural styles are formed by matching 4 types of im

12、peller with nozzle style pump casing, among them the assembly of straight-blade impeller and nozzle style pump casing has more application in practice. Structural style of impellerThe common structural styles of impeller 8-9 at home and abroad are shown as in Fig. 1, these four types of impeller hav

13、e the same geometric dimensions, see Table 1 and 2. Table 1: Performance parameters of high-speed pumpDescription ValueFlow（m3/h） 15Head（m） 400NPSH（m） 3.5Speed（r/min） 8500Power（kW） 75Table 2: hydraulic dimensions of high-speed pumpImpeller diameter （m） 0.17Impeller width at outlet （m） 0.012Number of

14、 long/short blades 8/8Basic circle of volute casing（m） 0.186Throat diameter of diffuser（m） 0.0095Length of diffusion section of diffuser（m） 0.067Diffusion angle（0C） 8（a） Semi-open straight-blade composite impeller（b） Open straight-blade impeller（c） Open cylindrical-blade impeller（d） Semi-open cylind

15、rical-blade composite impellerFigure 1. Structural diagram of impellerStructural style of pump casingThe pump casing is composed of annular volute and nozzle style diffuser, as shown in Fig. 2.Figure 2. Structural diagram of pump casingNUMERIC COMPUTATION Grid divisionPro/E is applied to build 3D hy

16、draulic model diagram of pump, and in order to obtain better computational results, a length of leading pipe whose length is 3 times of pipe diameter is added at impeller inlet and outlet of volute casing. The hydraulic dimensions of high-speed pump are generally relatively small, and the gap betwee

17、n impeller and pump chamber is very small, in order to obtain better computational results, the locations of small dimensions are locally encrypted in grid division, the size of grid division should not be too big. ANSYS-Fluent pre-processing software Gambit is used for grid division, and non-struct

18、ured hybrid grid TGird is adopted to divide the entire model, this grid is mainly composed of tetrahedrons, and hexahedrons, cones and wedges at local locations, it can well process grid division of complex model; the max. division size of impeller and annular volute is 1, the number of division ele

19、ments of impeller is 1307994 and that of annular volute is 380929. Selection of turbulence modelDr. Basque pointed out that the flow pattern varies significantly on the wall area of high-speed partial emission pump, the flow in the flow passage of impeller can almost be deemed to be a state of rigid

20、 motion with impeller, the rotating flow in annular volute also does not have motion relative to impeller, therefore, the stress of turbulent flow acts hardly; model of low Reynolds number is selected in the analysis of high-speed pump.In ANSYS-Fluent, the Spalart-Allmaras model is proven to be very

21、 effective for building low Re-number model, especially it has shown very effect for wall restraining flow, and has more extensive application in rotary machinery; by reference to selection of turbulence model for numeric analysis of partial emission pump with specific speed in the range of 50130, t

22、his model is selected as the turbulence model for numeric simulation of high-speed pump with low specific speed.Setting of boundary conditionsThe inlet boundary condition is set to be an inlet of uniform and continuous velocity without rotation, and the outlet is set to be the one of free outflow; t

23、he front and rear cover, wall of annular volute, wall of water piloting section at inlet and outlet and water body are set to be stationary; the impeller wall and water body of impeller are set to be rotary with the rotary speed of 8500 rpm, MRF model is selected and impeller wall, front and rear sh

24、roud and wall of volute housing are all set to be slipless adiabatic wall 6. ANALYSIS OF SIMULATION RESULTSAnalysis of pressure fieldTake the axial middle section of annular volute to calculate the static pressure inside the annular volute and impeller and use ANSYS-CFD-Post program to analyze the c

25、omputational results. NomenclatureType a high-speed pump of combined construction of semi-open straight-blade composite impeller and nozzle style pump casing.Type b high-speed pump of combined construction of open straight-blade composite impeller and nozzle style pump casing.Type c high-speed pump

26、of combined construction of open cylindrical-blade composite impeller and nozzle style pump casing.Type d high-speed pump of combined construction of semi-open cylindrical-blade composite impeller and nozzle style pump casing.（a） High-speed pump of type a（b） High-speed pump of type b（c） High-speed p

27、ump of type c（d） High-speed pump of type dFigure 3Static pressure diagrams of the four types of high-speed pumpCavitation tends to take place at the inlets of the four types of high-speed pump, the pressure presents a tendency of annular outward increment, yet the pressure gradually increases from i

28、nlet to outlet and from hub to rim, indicating the work done by blade profile increases radially. Take the tangential position of nozzle to excircle of annular volute as 0 position, in the area which is swept across the nozzle to volute shroud by the impeller from 0 position in the direction of impe

29、ller rotation, the pressure in impeller and annular flow passage has somewhat drop compared to other areas and the pressure gradient increases slowly; in the area from 0 to 90, larger negative pressure area appears at impeller inlet and blade inlet, which extremely tends to cause cavitation. In the

30、annular flow passage of annular volute, the static pressure distribution is rather uniform in the range from 90 to 360 in the rotational direction of impeller;, especially in front of inlet of straight pipe section, the static pressure drops significantly; in the area from straight pipe section to dif