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Journal of Drainage and Irrigation Machinery Engin
 
2008 Vol.26 Issue.4
Published 2008-07-25

article
Article
1 Performance computations of centrifugal pump handling viscous oils
LI Wen-guang
By considering water and viscous oils respectively as transported fluids,the performance and internal flow field of a centrifugal pump was investigated numerically with CFD software FLUENT.The effect of liquid viscosity on the pump performance was paticularly addressed.The results were compared with the experimental data.The results showed that the influence of the relative position between the volute tongue tip and the blade trailing edge on the performance is not significant.The hydraulic efficiency decreases and loss of impeller increases with increasing viscosity.The impeller performance is improved at particular viscosity.A peak exists in the impeller theoretical head curves at low flow rates.The pump head estimated with CFD is close to the test data and the "sudden-rising head effect" exists.A high viscosity and a particular level of roughness are responsible for the "sudden-rising head effect".
2008 Vol. 26 (4): 1-7 [Abstract] ( 1202 ) [HTML 1KB] [ PDF 435KB] ( 838 )
8 Numerical simulation of flow field and performance prediction of eccentric ball valve
FENG Wei-min, XIAO Guang-yu, SONG Li
By applying the finite volume method by means of combination of structure and non-structure grids and the k-ε two equation model based on the theory of isotropic eddy viscosity,the flow field structure for the eccentric ball valve corresponding to different opening degree,the curves of discharge characteristics,the cavitation and the pressure recovery factor are obtained.The eddies at the section Y-Z and X-Z increase at the relative opening degree 0.75 of the eccentric ball valve.When the relative opening degree reaches to 0.5,the high velocity flow of the valve is ruptured,which is closely related with the macro performance.There are two symmetrical eddies which have the same intensity and opposite direction appeared in the section X-Y as the further reduction of the relative opening,which means that there is a large-scale 3D-flow in the valve body of the eccentric ball valve in the event of the small opening degrees.
2008 Vol. 26 (4): 8-13 [Abstract] ( 1373 ) [HTML 1KB] [ PDF 426KB] ( 787 )
14 Structural optimization design of balance disc in multistage pump for better sensitivity
ZHAO Wan-yong, ZHANG Liang, WANG Zhen, JING Ye
Based on the assumption of laminar flow in the gap of balance disc,simplified N-S equation was adopted to analyze the axial gap and radial gap flows,and to derive the functional relationship of leakage and balance force with the geometrical parameters of balance disc.The F-b2 curve was drawn based on some real instances.The concept of sensitivity of the balance disc was proposed and qualitatively analyzed by the geometrical parameters of the disc.The results show that the sensitivity can accurately reflect the relationship between the axial gap and balance force.At constant axial force and within the accuracy of the pump structure,the changes of r2 have little impact on sensitivity;greater l and r1 and smaller b1 can make the balance disc work in the more sensitive region.
2008 Vol. 26 (4): 14-17 [Abstract] ( 1441 ) [HTML 1KB] [ PDF 189KB] ( 1089 )
18 Design of double action roller rotary pump for electric sprayer with high efficiency and low noise
ZHANG Sheng-chang, FANG Hong-sheng, DENG Hong-ying, ZHENG Ying-chen, LIN Bin-bin
The advantages and disadvantages of manual and electric sprays,and the characteristic of foreign-made electric spray pump were discussed.A new type of double action roller rotary pump was developed which belongs to positive displacement rotary pump.The new pump uses rolling friction to replace sliding friction and thus has lower frictional loss.Meantime,it uses symmetric structure with double inlet and outlet,which improves the radial force balance.All the above increase the service life.Eighth-power curve was used for drawing the transitional curve of the stator.Compared with other products,this new pump shows high efficiency and low noise.
2008 Vol. 26 (4): 18-21 [Abstract] ( 1247 ) [HTML 1KB] [ PDF 209KB] ( 697 )
22 Design and experiment of slurry pump with dual "S" impeller
')" href="#"> SHI Wei-dong, SUN Xiang-chun, CHEN Pei-lun, WANG-Zhun, CAO Wei-dong
Through improved design for IC slurry pumps,a design method with the dual "S" impeller was presented.By analyzing the passing mode of sundries in the slurry pumps with the dual "S" impeller,it was found that the long fibre effuses along the rear of blade,and passes easily in the "S" blade by long and short blade.The effects of geometry parameters of the impeller and volute for passing perfor-mance and efficiency were analyzed and the hydraulic design method was introduced.The test result shows that the dual "S" impeller of slurry pump reduces effectively foul sundries at the inlet and resolves the problem that the flow channel is easily jammed.In addition,the capability and efficiency of the pump are better than others used in the industry.Compared with other pumps,the actual head is increased by 0.6~1.1 m,NPSH is decrease by 0.2~0.5 m,the electrical power is reduced by 0.42~1.03 kW,and the efficiency is increased by 3%~6%.
2008 Vol. 26 (4): 22-25 [Abstract] ( 1125 ) [HTML 1KB] [ PDF 214KB] ( 1201 )
26 Numerical simulation on cooling fluids channel of magnetic pump
LIU Jian-rui, WANG Hong-rui
Two types of cooling methods for magnetic pump were introduced.The cooling flux and the dimension of flow-guided bore were calculated.By adopting the SIMPLE arithmetic and k-ε turbulent model to solve the N-S equations and the energy equation,numerical simulation on cooling fluids channel of a magnetic pump was done based on Fluent.Boundary conditions were set based on the knowledge of heat transfer.Temperature field and velocity field distributions were analyzed.The results showed that steam generation phenomena happened due to viscous layer near the bottom surface of the can,cavitation phenomena could be avoided by augmenting flux of cooling fluid,and outlet flow velocity could be reduced by augmenting the diameter of the center hole.
2008 Vol. 26 (4): 26-29 [Abstract] ( 1160 ) [HTML 1KB] [ PDF 246KB] ( 894 )
30 Theoretical analysis and numerical simulation of valveless piezoelectric pump with V-shape tube
HE Xiu-hua, ZHANG Rui
Based on the flow characteristics in diffuser/nozzle,a new type of V-shape tube used in the valveless piezoelectric pump is proposed for micro total analysis systems.The structure and working principle of the valveless piezoelectric pump with V-shape tube are described.The average flow calculation formula and efficiency formula of the system are developed by analyzing the flow field theoretically.Finite Element Method is applied to the flow field in the V-shape tube to obtain pressure contours of positive and negative flows in it.By comparing the pressure loss coefficients in the V-shape tube,othe diffuser/ nozzle parallel connection and Y-shape tube,the first two curves of the ratios of pressure loss coefficient follow the same variation tendency.The reliability of numerical simulation is proved,which provides guidance for the design of piezoelectric pump.
2008 Vol. 26 (4): 30-34 [Abstract] ( 1051 ) [HTML 1KB] [ PDF 280KB] ( 685 )
35 Analysis on cavitation characteristic in centrifugal pump
PAN Zhong-yong, NI Yong-yan, LI Hong, CAO Ying-jie
According to the formula of net positive suction head of centrifugal pump,the main factors which affect pump cavitation are the design of pump casing and impeller inlet.The formula of cavitation specific speed is rewritten into a new form related with blade inlet angle,hub-tip ratio and the two factors mentioned above.A diagram is drawn to show the design variables that have effect on the cavitation specific speed.By the diagram,it can be deduced that the optimum blade inlet angle for maximum cavitation specific speed is in the range of 10 to 30 degres.The factor related with impeller has more effect on the cavitation specific speed than that with casing.The cavitation incipient criteria show that any pump works under the condition of cavitation.Therefore,a valid curve,which corresponds to the 0.5% head-drop curve,is recommended here to limit the running range for pump at cavitation condition.
2008 Vol. 26 (4): 35-38 [Abstract] ( 1493 ) [HTML 1KB] [ PDF 247KB] ( 1214 )
39 Numerical analysis on inner flow in low specific speed double-suction centrifugal pump with spiral suction chamber
ZHU Rong-sheng, OU Ming-xiong, FU Qiang, GUAN Rong-guo, LI Ji-zhong
With the use of RNG turbulent model in the CFD software Fluent,the inner flow of double suction centrifugal pump with semi-spiral suction chamber was calculated.It was found that the flow rate is increasing from inlet to outlet in the impeller at the first half of impeller channel;the velocity beside the pressure side of blade is larger than that beside the suction side.The flow field distribution of impeller is uniform.But in the semi-spiral suction chamber,swirls occur beside the tongue and sealed block at the designed flow rate,and the swirls become more obviously when the flow rate increases,which has effect on the inlet condition of the impeller.The above analysis provides references for the improvement of the double suction pump with semi-spiral suction chamber.
2008 Vol. 26 (4): 39-42 [Abstract] ( 1347 ) [HTML 1KB] [ PDF 257KB] ( 682 )
43 Optimum hydraulic design for siphon outlet in large pumping stations
LI Yan-jun, YAN Hong-qin, GE Qiang, YAN Deng-feng, HU De-yi
A mathematical model has been built for the geometric contours of siphon outlet conduit in pumping stations based on the principle of gradual rate,and the general software for hydraulic optimum design has been developed based on the geometrical parameters of outlet passage.The geometric contours of siphon outlet conduit can be drawn quickly.The hydraulic performance of siphon outlet conduit can be predicted through numerical simulation of the internal flow status of the conduit.The optimization models are established on the basis of the hydraulic loss of the conduit as the objective function and the location of the hump section of the conduit as the variable.The results indicate that the closer to the intake the hump sections of the conduit are,the less the hydraulic loss of the conduitis is.It is suggested that the location of the hump section should be close to the intake as much as possible in order to reduce the hydraulic loss.
2008 Vol. 26 (4): 43-47 [Abstract] ( 1689 ) [HTML 1KB] [ PDF 297KB] ( 886 )
48 Simulation of water supply system based on PID control
LI Hong, ZHENG Ying, QIN Wu-xuan
In order to implement water supply system experiments,the basic structure of water supply system and corresponding modules transfer functions were established to constitute dynamic block diagram.Output response in MATLAB simulation integrated environment Simulink was simulated.Stable boundary method,lead compensator based on root locus method and designing PID para-meters method were used to design the controller.Appropriate controller design method was found by observing system output characteristic.It was concluded that PID stable boundary method and lead compensator based on root locus method are not suitable to regulate water supply system;whereas the method of designing PID parameters can directly modify the parameters in Simulink to find a suitable set of PID parameters which give satisfying output response of the system.The simulation results provide theoretical basis for building experimental platform.
2008 Vol. 26 (4): 48-51 [Abstract] ( 1657 ) [HTML 1KB] [ PDF 225KB] ( 895 )
52 Characteristics of dual purpose sprinkling irrigation and hose irrigation machine
FAN Yong-shen, HUANG Xiu-qiao, WU Feng, LI Jin-shan, DUAN Fu-yi, YU Feng
A new type of light weight and small size machine with sprinkling irrigation and hose irrigation was introduced.The machine′s set of remotion and pressure water are provided by a capstan car,and sprinkling irrigation by a sprinkler car.The machine has sprinkling irrigation and hose irrigation system,and can satisfy different farm crops in different growth time at the request of water.The sprinkler car set can adjust the height of machine,which makes the sprinkler to always work in the best sprinkling height.The machine adopts lower press refraction type sprinkler and hose tube for lower press irrigation system,which makes the machine′s work press to drop 30%.By studying the machines water turbine characteristic,amovement characteristic,and insufflations characteristic,the machine′s technical parameters were determined.Test results show that the new machine may reduce the influence of sprinkling uniformity degree by wind,reduce the water loss,and irrigation uniformity degree can be increased by 90%.
2008 Vol. 26 (4): 52-56 [Abstract] ( 1227 ) [HTML 1KB] [ PDF 283KB] ( 758 )
57 Application of hydrocyclone separator to pollution control in storm runoff
CHU Jin-yu, LI Wei, LI Wei-bin
In order to control the non-point pollution and to improve the water quality environment of Zhenjiang,a hydrocyclone separator was installed in the underwater net to make spot experiment in the raining days.Water samples were taken in different time intervals and runoff yield.Five indexes,total nitrogen,total phosphorus,SS,turbidity,pH,and COD,were measured.By analysis,the peak of the concentration appeared later than that of the rainfall quantity.20 minutes after runoff yield,the ω(SS) rised from 56.8 mg/L to 203.9 mg/L,ω(COD) rised from 69.2 mg/L to 135.2 mg/L,and turbidity rised from 49 to 128.The water quality in the pipeline worsened rapidly within short time.But with the extension of time,water quality was basically stabilized and there was less pollutant.The SS at the outlet was 52.9 mg/L,ω(COD)was 63.2 mg/L,turbidity was 45 mg/L in average,and removal rate was up to 75% for these three indexes.TN droped in initial stage of the surface flow and then slightly rised.The change range of TP was relatively small.Though the removing rate of TN and TP was not high,they could meet the discharge standard.This kind of hydrocyclone separator performs well in controlling the pollution in storm runoff.
2008 Vol. 26 (4): 57-60 [Abstract] ( 1339 ) [HTML 1KB] [ PDF 221KB] ( 865 )
61 Influence of salt-out liquid-solid two phase flow on chemical pump performance
LIU Dong, YANG Min-guan, DONG Xiang, WANG Qun
In order to solve the salt-out problem which is common in the bittern transferring process,and reduce the clogging problem in the chemical pump which will deteriorate the daily production,sodium sulfate which commonly exists in bittern is used as solute,the delay times under different flow rates and temperatures are measured,and the relations among delay time,flow rates and temperature are studied.The results of the experiment indicate that the delay time becomes shorter as initial temperature decreases.For the flow rate below 1 m/s,the delay time increases with the increase of flow rate.However for the flow rate exceeding 1 m/s,the delay time does not change obviously.Performances of chemical pump under different salt-out processes are also studied;relations among time,head and power are analyzed.The results are proved by the theories of crystal growth kinetics and two-phase hydrodynamics.
2008 Vol. 26 (4): 61-64 [Abstract] ( 1368 ) [HTML 1KB] [ PDF 212KB] ( 1121 )
65 Mathematic model of evaporation and breakup for charged droplets
WANG Xiao-ying, WANG Jun-feng, WEN Jian-long, LUO Ti-qian
By theoretical analysis on charge decreasing,mass transfer and heat transfer processes during charged droplet evaporation,the discipline of charge decreasing and the mathematic model for charged droplet evaporation and breakup are obtained.Meanwhile,for a droplet falling freely under gravity with horizontal projection,the track model and the longest distance in both horizontal and vertical directions are obtained.The results show that charge decreases exponentially with time and the decrease gets quicker if the conductivity is greater or dielectric constant is smaller.The total time for droplet evaporation is in proportion to initial droplet radius,the critical charge gets smaller with increasing droplet temperature,and the droplet breaks when the droplet charge is greater than the critical charge.The model predicts the Coulombic fission time of the droplet.
2008 Vol. 26 (4): 65-68 [Abstract] ( 1411 ) [HTML 1KB] [ PDF 187KB] ( 707 )
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