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Journal of Drainage and Irrigation Machinery Engin
 
2012 Vol.30 Issue.5
Published 2012-09-30
article
Article
497 Multioperatingcondition design of centrifugal pump with medium specific speed
YUAN Shou-Qi, HU Bo, LU Wei-Gang, LI Tong, HUANG Zhi-Pan
In order to allow the hydraulic performance of type TS65-40-125 centrifugal pump with a medium specific speed to satisfy multioperatingcondition simultaneously, its impeller was redesigned three times by means of the enlarged design flow rate method. A structure grid was generated in Ansys Workbench 12 and the grid sizeindependence was analyzed. The pressure, turbulence kinetic energy, velocity distributions in those impellers and the overall performance curves were obtained with the commercial software CFX. Finally, one optimal impeller was identified and experiments were made against it. It can be concluded that the properly selected geometry parameters of the impeller can effectively improve head and efficiency of the centrifugal pump with medium specific speed and expand the high efficiency zone by using the enlarge design flow rate method. The head of the redesigned pump was improved as high as 5 m compared with the original one at the design point and the efficiency at five operating points basically met the specifications in the related national pump standard of China.  Some references are provided for the multioperatingcondition design of centrifugal pump with medium specific speed.
2012 Vol. 30 (5): 497-502 [Abstract] ( 2282 ) [HTML 1KB] [ PDF 5064KB] ( 2290 )
503 Optimization of impeller back vanes in doublesuction centrifugal pump by CFD technique
QIAN Zhong-Dong, GAO Yuan-Yong, XIE Hua, WANG Zhi-Yuan
The water flow and sand particles motion in a prototype of doublesuction centrifugal pump were simulated using the RNG k-ε turbulence model and the Euler-Lagrange multiphase flow model. The influence of length and relative position of the back vanes on sand mass concentration around the wearrings and pump efficiency were analyzed. According to the predicted results, the flow models adopted in this paper can predict the water flow pattern and the sand concentration near the wearrings precisely. The velocity of water flow near the wearrings is so low that the flow carries less sand particles away from the entrance to wearrings, causing there exits a much high sand concentration near the rings compared with the bulk sand concentration in the flow. Eventually the two surfaces of the wearrings gap are damaged quite quickly.With decreasing length of back vanes the pump efficiency is degraded and there exits a minimum length for back vanes to prevent sediment erosion in the wearrings. When the number of backvanes is reduced to three from four, the ability for flow to carrying sand particles is retained and its protecting effect on the wearrings the impeller rings is significant. Further, the pump efficiency is kept in a reasonable level. The case 7 is the optimal design of the blade vanes.
2012 Vol. 30 (5): 503-507 [Abstract] ( 1846 ) [HTML 1KB] [ PDF 4757KB] ( 1742 )
508 Numerical simulation of solidliquid twophase turbulent flowin submersible axialflow pump
Shi-Wei-Dong- , LONG Fei, ZHANG De-Sheng, LENG Hong-Fei, WANG Guo-Tao
The solidliquid twophase turbulent flow in a submersible axialflow pump was simulated by using a softwareFluent with the mixture multiphase flow model，RNG k-ε turbulence model and SIMPLEC algorithm to study the characteristics of such a flow. The results of twophase flow have been compared with those of water flow. The flow patterns at several volume fractions, particle diameters and solid densities were revealed. It is concluded that solid particles mainly accumulate near the leading edge of pressure surface of blades but close to the hub in the flow channels of impeller. Solid particles tend to move to the suction side of blades as their diameter is increased at the same volume fraction. For the particles with the same diameter, as the solid volume fraction is increased, the solid particles on the pressure side tend to move to the blade leading edge and the hub, and those on the suction side tend to move to the outlet of impeller and the hub.
2012 Vol. 30 (5): 508-512 [Abstract] ( 2293 ) [HTML 1KB] [ PDF 10198KB] ( 1529 )
513 Study on control of multielement airfoil based on CFD
CHEN Hong-Xun- , HUO Cong-Cong, LIU Wen-Mei
To improve the performance of fluid machinery at offdesign conditions, a multielement airfoil with adjustable leading edge slats was designed inspired by the idea of improving liftdrag ratio of aircraft by adjusting the leading edge slats at takeoff stage. The numerical model of the inputs (deflection of the leading edge slats, overlap and gap) and output (the liftdrag ratio of aircraft) was established based on CFD numerical simulation of steady flows. Those three input variables were optimized through the genetic algorithm to get the maximum liftdrag ratios in different angles of attack. The relations between angle of attack and slats position for an optimal liftdrag ratio were established, providing a theoretical basis for active control of flow. The results show that using genetic algorithm to optimize the slat parameters can reduce timeconsuming as high as 40％. The aerodynamic performance of multielement airfoil was greatly improved through optimizing slats parameters. As a result, the liftdrag ratio at a large angle of attack was raised compared with the original airfoil. This work can provide a reference for designing fluid machinery with highefficiency under multiconditions.
2012 Vol. 30 (5): 513-516 [Abstract] ( 2202 ) [HTML 1KB] [ PDF 1042KB] ( 1863 )
517 Principle and control system design for bearingless permanentmagnet slice motor pump
ZHU Huang-Qiu, CHEN Jin-Hai, ZUO Wen-Quan
Since the bearingless permanent magnet slice motor (BPMSM) can be used to drive a centrifugal pump, a prototype of such a motor was designed based on slice rotor suspension principle, subsequently its operating principle was expounded, eventually the mathematical models for electromagnetic torque and radial suspension force were presented．The hardware of digital control system for the motor was designed by using the TMS320F2812 DSP and the software for the system was developed as well. Then, a humancomputer interaction interface was composed for the control system to make realtime control and online debugging more easily. The experiments on slice rotor suspension and operation were performed. The experimental results show that realtime online debugging through the humancomputer interaction interface can determine controlling parameters quickly and easily to allow the system to achieve the scheduled requirements on control. The speed of slice rotor varies from 0 to 2 000 r/min continuously and can attain a stable speed soon. The rotor center of mass vibrates near the equilibrium position (2 000, 2 000) and the vibration amplitude is less than 80 μm in the radical direction under noload conditions. Thus, the prototype of 4 kW BPMSM used to drive a centrifugal pump and its digital control system has an excellent static and dynamic performance．
2012 Vol. 30 (5): 517-521 [Abstract] ( 2028 ) [HTML 1KB] [ PDF 7324KB] ( 1367 )
522 Performance of liquidsolid twophase flow in jet pump by LES
ZHOU Ling-Jiu, YUAN Ling-Li
 To find out the flow characteristic of 3D liquidsolid twophase flow in a jet pump, the large eddy simulation (LES) was used to calculate the flow field in the jet pump. The mixture model was adopted to treat the liquidsolid twophase interaction. Influences of solidphase initial volume fraction and granular diameter as well as flow ratio on the jet pump characteristics were analyzed. The results show that the pressure ratio and efficiency of pumping solidliquid two phase fluids have a minor difference with those of delivering water at a small flow rate ratio. With increasing flow rate ratio, however, the pressure ratio and efficiency for solidliquid two phase fluids are decreased a lot compared with those for water when the granule density is increased. For a constant initial solid volume fraction and granular diameter, the solid volume fraction is increased with the flow ratio after a fully mixing takes place. The larger the granular diameter, the more easily the solid volume fraction distribution becomes concentrated. The results of the study lay a foundation for particular applications of engineering.
2012 Vol. 30 (5): 522-526 [Abstract] ( 6925 ) [HTML 1KB] [ PDF 1677KB] ( 1967 )
527 Numerical calculation and analysis on axial thrust in screw centrifugal pump
LI Ren-Nian-1, QUAN Hui-1, HAN Wei-1, LI Qi-Fei-1, SU Qing-Miao-2
When the axial thrust is estimated in a screw centrifugal pump under solidliquid twophase flow conditions by means of ordinary analytical methods, there exists problems, such as mathematic models establishment of flow and difficulties in closure of the models. Thus in order to predict the axial thrust precisely and to correlate it to the physical property parameters of the medium handled by the pump, the axial thrust in the screw centrifugal pump of type 150×100LN-32 was calculated when it transported a sandwater twophase fluid by using CFD codeFluent. The twophase flow in the pump was described by the timeaveraged Navier-Stokes equations in relative coordinate systems and the mixture model. The standard k-ε twoequation turbulence model and the SIMPLE algorithm were used in numerical simulations. An axial thrust was calculated after the pressure distributions in the pump were available. In this way, the problems and the difficulty aforementioned can be avoided. The relations of axial thrust to solid volume fraction, particle diameter and flow rate of the twophase flow were explored by using the computational results. The results showed that the axial thrust rises with increasing solid volume fraction, but reduces with increasing flow rate and particle diameter. The conclusion is of great significance for improving the stability of the pump and extending its lifespan.
2012 Vol. 30 (5): 527-531 [Abstract] ( 3011 ) [HTML 1KB] [ PDF 3729KB] ( 2371 )
532 Analysis on flow characteristic of flatwalled diffusers applied in valveless piezoelectric pumps
HE Xiu-Hua-1, ZHUO Hong-Cai-1, YANG Song-1, DENG Zhi-Dan-2, Li-Fu-1
The flow in a tube with the narrowest width 150 μm and the depth 150 μm was studied numerically, two flow resistance coefficient curves versus cone angle θ and lengthwidth ratio l/w were obtained when the tube was subject to convergent and divergent flows at a Reynolds numbers ranged in 100-2 000. The results show that the smaller the cone  angle θ, the more significantly dependent on θ and l/w the flow resistance coefficient λ, and a transition occurs in flow resistance feature. The relations of λ to θ and l/w are different at Re=100 and Re≥500 obviously. When Re=100, most of tubes present the typeⅠ tube characteristics that flow resistance coefficient in the divergent direction is less than in the convergent one, and λ reaches a maximum 1.22 at θ=20°and l/w=20. When Re≥500, most of tubes show the type Ⅱ tube characteristics which is contrary to typeⅠ, and λ reaches a minimum 0.63 at θ=20°and l/w=1. The results show that the flow resistance coefficient of flatwalled diffusers highly depends on Reynolds number. In order to improve performance of the valveless piezoelectric pump, appropriate geometrical parameters should be chosen in the pump design according to the actual working condition of the pump.
2012 Vol. 30 (5): 532-537 [Abstract] ( 1908 ) [HTML 1KB] [ PDF 5401KB] ( 1605 )
538 Effects of guide vanes parameters on water resistance coefficient and efficiency of mixedflow pump
YANG Cong-Xin, DU Yuan-Ying, LI Yi-Bin
The numerical simulations of the threedimensional flow inside a mixedflow pump were done by using unstructured tetrahedral mesh and the SIMPLEC algorithm, which was employed in Fluent. The timeaveraged continuity equation and the N-S equation as well as the RNG k-ε turbulence model in a relative coordinate system were used as the flow model in the pump. The static pressures and absolute velocity distribution on impeller blades and guide vanes were examined after the mesh sizeindependent was checked. The flow resistance coefficient across the pump was estimated with steady and unsteady head curves when the number of guide vanes and inlet angle of the guide vanes were subject to be changed.It was found that the lowest flow resistance coefficient was reached at three guide vanes, and the highest head and best efficiency were achieved at nine guide vanes while the rest geometrical parameter of the guide vanes remained unchanged. At a zero angle of attack the lowest flow resistance coefficient, highest head and best efficiency were obtained at the design condition when just the inlet angle of the guide vanes were altered. However, the coefficient, head and efficiency didn′t seem changed significantly. The results showed that the number of guide vanes should be as small as possible to meet the requirement on efficiency for a particular application. In addition the mixedflow pump performance has no significant change when the inlet angle of guide vanes is changed by less than 5° for a diffuser casing.
2012 Vol. 30 (5): 538-542 [Abstract] ( 2319 ) [HTML 1KB] [ PDF 3479KB] ( 1709 )
543 Design of initial volume of parallel doublechamber of piezoelectric pump
SUN Xiao-Feng-1, YANG Zhi-Gang-2, JIANG De-Long-1, HE Li-Hong-1, JIANG Bin-3
In order to explore influence of initial volume of the pumping chamber on performance of a piezoelectric pump, several piezoelectric pumps with parallel doublechamber and a checkvalve were manufactured, in which six different initial volumes were designed. The performance of those pumps was measured under different compression ratios (the ratio of stroke volume over the initial volume) when they were driven by a bimorph actuator at the 110 V driving voltage and frequency of less than 400 Hz, in the cases that water and air were handled, respectively. The results showed that a pump has the best output flow rate when its compression ratio was 1/18 for water, and the highest flow rate as high as 1 330 mL/min.A larger compression ratio could result into a higher output pressure and a better selfpriming capability.The maximum output pressure and the highest selfpriming water column height were 58.5 kPa and 69 cm, respectively. For air, however, the larger the compression ratio, the better the pump output performance. The maximum output flow rate and the highest output pressure were 850 mL/min and 6.5 kPa, respectively. When the compression ratio was less than 1/32, the pump performance would be breakdown.
2012 Vol. 30 (5): 543-547 [Abstract] ( 1812 ) [HTML 1KB] [ PDF 1240KB] ( 1708 )
548 Hydraulic control of super short vertical well entry/draft tube
CHENG Wei-Ping, ZHANG Jun-Jun, CHEN Yi-Min, GAO Yue
In order to improve the flow patterns in the vertical well entry / draft tube of pumped storage power stations, both numerical simulations and model experiment investigation were carried out to study the hydrodynamic characteristics. And a 3D RNG k-ε turbulence model was adopted in the numerical efforts. The flow characteristics of two kinds of diffusers, one is ellipse curve and the other one is cone expansion, were mainly compared under pump conditions. The results showed that the flow patterns in the tube with a coneshaped diffuser were better than that with an ellipse one. The flow rate allocation ratios in the tubes with a cone diffuser of 4.3°, 5°, and 7° diffusion angles were simulated and analyzed. The results indicated that  the diffusion angle of the cone diffuser installed behind an elbow pipe should be less than 4.5°. The hydraulic model experiments were conducted for the recommended vertical well entry / draft tube. The experimental results showed that there were uniform flow patterns in the models. The loss coefficient of the total head was 0.48 when two units were operated under pump condition while it was 0.33 under turbine condition.
2012 Vol. 30 (5): 548-552 [Abstract] ( 2074 ) [HTML 1KB] [ PDF 5362KB] ( 2033 )
553 Experimental study on composite insulating plastic board of preventing channel seepage and frost heave
HE Wu-Quan, ZHENG Shui-Rong, SHEN Chang-Yue
A composite insulating plastic board of polyurethane foam, in which the powders of broken corn stalks have been stuffed, was invented; its formula and preparation technology were primarily decided as well. Effects of the size and content of broken corn stalks power (0＜D≤0.45 mm,0.45＜D≤1.50 mm，1.50 mm＜D≤4.00 mm), on the density, compression strength and thermal conductivity of the polyurethane foam plastic were experimented. Meanwhile, their influences on the foaming time, foam molding of the plastic were observed too. The results showed that when the corn stalk broken powder size is fixed, the density of the foam plastic increase, its compression strength drops off with increasing content of the powders stuffed. When the broken corn stalks powder size and filled content are 0.45 mm＜D≤1.50 mm and 30%, the compression strength (compressed by 10%), heat conductivity (－40-＋70 ℃) and dimension change of the composite polyurethane foam plastic board are 85 kPa, 0.038 W/(m·K) and ±1%, respectively, suggesting the board can satisfy the requirements on the performance preventing seepage in channel lining applications and damage on channels caused from frost heave. According to estimates, using this composite insulating foam board in projects can reduce their cost by about 25%. Moreover, waste products of agriculture can be made full use, reducing pollution on the environment caused from disposal or incineration of those wastes.
2012 Vol. 30 (5): 553-557 [Abstract] ( 1964 ) [HTML 1KB] [ PDF 977KB] ( 1662 )
558 Numerical analysis on flow in pumpturbine in turbine mode at high flow rates
ZHANG Liang, GUO Lei, YIN Jun-Lian, WANG Le-Qin, WU Yu-Lin
To investigate the characteristics of flow in a pumpturbine in turbine mode at high flow rates, a geometrical model was established based on the prototype model of the pumpturbines for a pumped storage power station. The shear stress transport (SST) k-w  turbulence model and the pressurevelocity coupling scheme SIPLEC were used to simulate the internal flow fields in the model by means of two kinds of mesh, i.e. structured and unstructured, and the obtained results were compared with the measured data.It was shown that there were periodically distributed vortexes in flow passages of the runner at a high flow rate. The scale of the vortexes steadily became larger and extended to the blade trailing edges with increasing of flow rate, causing energy losses.Moreover, such vortexes occupied some crosssectional area of the passages, then the fluid velocity near the pressure sides of blade ascended. This vortex dominated flow has a high demand on quality of mesh in simulation, and it is the reason why the flow in high flow rates is difficult to be simulated.These conclusions can provide a theoretical basis for analysis and simulation of flow at a high flow rate.
2012 Vol. 30 (5): 558-562 [Abstract] ( 2664 ) [HTML 1KB] [ PDF 7846KB] ( 1569 )
563 Comparison of ventilating effect of indoor displacement and mixing ventilation
YUAN Jian-Ping, WANG Long-Yan, HE Zhi-Xia, LIU Xiao-Fan
The main objective of the article is to investigate the difference in indoor thermal comfort and air quality by means of numerical simulation based on a wellvalidated CFD(computational fluid dynamics) model when a commercial kitchen is subject to mixing and displacement ventilation. It was shown that using thermal displacement ventilation in the kitchen can reduce indoor temperature without increasing the airconditioning system capacity. Under the same indoor environmental conditions, the flow velocity of mixing ventilation (MV) is almost twice that of displacement ventilation (DV) in average, and the crossdrafts exists which leads to an uneven flow pattern. The temperature stratification is evident for DV, the temperature gradually gets higher upwards, and it has an appropriate value in the human breathing zone. Also, the air quality in the human breathing zone of DV is better than that of MV system which operates in the same air velocity. Moreover, the average air age of the former is less than 100 s in the kitchen. A properly designed displacement ventilation can maintain a thermally comfortable environment where the air velocity is lower than 0.3 m/s, the difference in temperature is below 2 °C between the head and ankle level, and the percentage dissatisfied people in breathing zone is smaller than 15%, and eventually can provide a better IAQ(indoor air quality) in the occupied zone.
2012 Vol. 30 (5): 563-566 [Abstract] ( 2448 ) [HTML 1KB] [ PDF 2190KB] ( 3460 )
567 Numerical simulation on unsteady flow field of straight bladed darrieus wind rotor
ZHAO Zhen-Zhou, YUAN Hong-Hong, ZHENG Yuan, HUANG Juan, ZHAO Zhen-Ning
In order to know more information about the complex turbulent field in vertical axis Darrieus rotors, the unsteady k-ω turbulence model and sliding mesh technique were used to model the aerodynamic characteristics and twodimensional flow field in this kind of wind rotor with straight blades of NACA0012 airfoil. The aerodynamic flow field around the blades and torque characteristics of rotor at different rotational speeds were investigated. The flow fields in the rotors at different time instances i.e. in different azimuth angles, were presented, the results revealed that the relation angle of attack with azimuth angle is not a sinusoid. The torque curves indicated that a maximum torque was generated when the blades were at the 90° azimuth angle, the blades at downstream of the rotor had a near zero or even a small negative torque, suggesting the angles of attack there were very small. At the same wind freestream velocity, the wind velocity in the rotor was reduced with increasing rotational speed. The torque curves of upstream blades showed a maximum torque at a rotational speed when the speed was increased, however, the torque on downstream blades decreased steadily and exhibited a considerable variation. The contrast of numerical results and test results prove that the turbulence model with slip grid technology can reflect the flow field in a vertical Darrieus wind turbine with straight blades.
2012 Vol. 30 (5): 567-572 [Abstract] ( 2464 ) [HTML 1KB] [ PDF 10457KB] ( 1430 )
573 Design and numerical simulation of highpressure nuclear power gate valves
LIU Jian-Rui, LI Chang, LIU Liang-Liang, HE Xiao-Ke, XIANG Hong-Jie
A highpressure electric actuated gate valve with 25 MPa nominal pressure and 150 mm nominal diameter was designed for the needs of nuclear power industry, the design and calculation method of its main structure was introduced. The reasons for pressure loss production and the locations where the loss happened as the valve was in open. The FSI (fluidstructureinteraction) in the valve was simulated to show the influence of fluid pressure and velocity on the valve structure. The threedimensional structure model and water fluid domain of the valve were established, the CFX software was used to mesh the models and define the boundary conditions, then the pressure and velocity distribution in the valve were calculated, and the locations where the major pressure loss was generated was clarified. The fluid pressure was applied to the gate valve in Ansys to carry out an FSI analysis. The results showed that there are vortices around the valve seat, and the fluid static pressure and velocity near the wall are decreased significantly in rear of the seat, but the pressure drop and velocity magnitude are very small in the upper of the valve central line. The flow resistance coefficient of the valve is 0.093. The maximum deformation and stress of the valve are 19.4 μm, 70.8 MPa, which are located in the tip and side surface of the seat, respectively. These deformation and stress are within the allowable ranges.
2012 Vol. 30 (5): 573-577 [Abstract] ( 2089 ) [HTML 1KB] [ PDF 3089KB] ( 1663 )
578 Stress analysis and structure optimization design of annular Udiaphragm
DENG Hong-Ying, ZHANG Sheng-Chang, ZHENG Ying-Chen
To reduce total stress level, meet the design requirement on even stress distribution and improve design efficiency of annular Udiaphragm in hydraulic diaphragm pumps, the stress and strain in Udiaphragm were analyzed and its structure was optimized by using the FEM and parameter optimization method. The stress distribution patterns, peak stress locations etc in the Udiaphragm model were summarized based on the stress distributions in the diaphragm under a series of displacement loadings calculated by conducting nonlinear analyses in FEM software Ansys. Subsequently, the structures of diaphragm end fixing clamps, moving support end and free deflection semicircle transitional segment were optimized. The parameters relating to diaphragm structure were determined by using the parameter optimization method in Ansys when the maximum stress in the diaphragm was used as a limited state variable and the total stress in elements was chosen as an objective function. The finite element analysis results indicated the maximum peak has been reduced to 0.027 MPa from 0.083 MPa in the annular Udiaphragm after the optimization, suggesting the diaphragm is going to be subject to a significantly lowered stress level. Moreover, a uniform stress distribution occurred in the inner and outer surfaces of the diaphragm, and the stress concentration effect tended to be moderate.
2012 Vol. 30 (5): 578-582 [Abstract] ( 2279 ) [HTML 1KB] [ PDF 4506KB] ( 2005 )
583 Analyzing performance parameters of upstream pumping mechanical seals based on dynamic mesh technique
CHEN Hui-Long, LIU Yu-Hui, LIU Tong, WANG Qiang, LIU Zhi-Bin, ZHANG Jia-Bin
In order to get an accurate liquid film thickness of an upstream pumping mechanical seal, a model of 3D flow domain of the seals with spiral grooves was generated by using Pro/E wildfire. The flow field in the microgap of the seals with spiral grooved faces was simulated with CFD code Fluent using the dynamic mesh and cavitation model. Liquid film thicknesses under different working conditions were obtained and compared with the experiments to verify the simulated results. And effects of working condition parameters on the stiffness and leakage of liquid film were calculated and analyzed. The results showed that the simulated liquid film thicknesses is basically consistent with the experiments (the maximum, average and minimum errors are 19.6%, 8% and 0), verifying the dynamic mesh technique is feasible for simulating flow field in the gap of a mechanical seal. Also the cavitation problem should be considered in such simulations to obtain real characteristics of the flow field. The thickness, leakage and rigidity of liquid film increase with increasing rotational speed, medium pressure. Further the spiral grooves not only produce a pumping effect, but also generate a dynamic pressure effect.
2012 Vol. 30 (5): 583-587 [Abstract] ( 1942 ) [HTML 1KB] [ PDF 2163KB] ( 1687 )
588 Calculating drainage flow rate through selfcleaning screen filters
LUO Xiu-Ping, LIU Huan-Fang, ZONG Quan-Li, YI Ping
According to the investigation of the impact factors on the flow rate， it was found that the drainage flow rate through a selfcleaning screen filter Qp is determined by a flow coefficient.In order to investigate variation features of the flow coefficient， a series of experiments were conducted at various dimensionless inlet crosssection areas of the sand suction component in a selfcleaning screen filter. It was observed that the coefficient increases with opening initially. However, once the opening rises to a certain level, the coefficient no longer changes with the opening and tends to arrive at a constant. The established flow coefficient formula showed that when the dimensionless inlet crosssection area is more than 0.15, i.e. the height of the inlet is bigger than 500 mm (in the experiments, the width of the inlet was kept to be 300 mm), the change in the flow coefficient caused by the dimensionless area is less than 0.5%. This suggests the flow coefficient almost no longer depends on the dimensionless inlet crosssection area. Such a theoretical outcome is consistent with the experimental observations. Finally, an empirical formula was proposed to calculate the drainage flow rates through a selfcleaning screen filter based on the flow coefficient established. Interestingly, the root mean square error (RMSE) is 0.001 74  only, showing the formula has an excellent accuracy.
2012 Vol. 30 (5): 588-591 [Abstract] ( 2359 ) [HTML 1KB] [ PDF 1012KB] ( 2780 )
592 Modeling and analysis of airlift pumping system based on momentum theorem
HU Dong, TANG Chuan-Lin, LIAO Zhen-Fang
In order to look for a new method to establish theoretical models for airlift pumping systems, the mixture flow governing equations were constructed for an airlift pump based on the momentum theory, and the relations among the volumetric fluxes of air, water and solid were obtained numerically by using linearization approach, theoretical analysis and empirical formulas. A river sand airlift pumping system was built in laboratory, and ordinary river sands of medium size were selected as test solid particles to investigate the reliability of the model. The relations between volumetric fluxes of both water and solid and that of air were obtained experimentally and were compared with that evaluated by the theoretical model. It showed that many complicated factors had effect on the model, and therefore it had to be linearized to make the flow parameters prediction easier. The model exhibited a good accuracy for water volumetric flux prediction and the relative errors were almost less than 8%, while slightly poor for solid volumetric flux prediction. Moreover, the model presented more accurately for air / water two phase pumping system and the relative errors were less than 6%. In addition, the theoretical evaluation matched well with the experimental observation at moderate air volumetric flux, while showed slightly poor under other conditions especially at its peak values. The results can provide an important reference for understanding and optimizing various parameters of airlift pumping systems.
2012 Vol. 30 (5): 592-597 [Abstract] ( 2367 ) [HTML 1KB] [ PDF 1170KB] ( 1942 )
598 Numerical simulation of 2D shallow water equation in arbitrary curvilinear coordinates
WU Wei-Guo, XUE Shi-Feng
The problems with complex boundary shapes, such as natural river channels, lakes, estuaries and bays, were solved by using the boundary curve fitting methods. Arbitrary orthogonal curvilinear grid was established to overcome the computational difficulties caused by those complex boundaries. Then, a set of derived equations in the arbitrary curvilinear coordinates, including 2D shallow water equation, turbulence kinetic energy equation and dissipation rate equation etc. were numerically discreted by the finite difference method. In addition, the 2D shallow water equation was numerically solved within the computational domain by using the alternating direction implicit (ADI) difference scheme. In order to verify the reliability and correctness of the method, the De Vriend's 180° plane curve flume experiment model was adopted as an example to implement the numerical simulations.  Finally, the simulation outcomes are in excellent agreement with that experimental results with a maximum error as large as approximate 10-2, indicating that the numerical method in this paper is reasonable and feasible. Hence, the method will provide an efficient way for calculating hydrodynamics of water bodies with arbitrary complex boundaries, such as natural river channels and lakes.
2012 Vol. 30 (5): 598-602 [Abstract] ( 2538 ) [HTML 1KB] [ PDF 1465KB] ( 1959 )
603 Simulation of water spraying lateral distribution in synchronously controlled moving linearmove irrigators
YUAN Yan-Wei, ZHANG Xiao-Chao, WU Cai-Cong, FAN Yun-Tao
Rainfall distribution and water trajectory information was acquired through a single nozzle indoor test. A threedimensional model of water motion was built by using the virtual reality technology, such as threedimensional modeling and particle system etc. The optimal driving speed was realized by studying the uniformity of water distribution across the lateral direction when a linear move irrigator is being moved ahead.The configuration of sprinklers was optimized by analyzed effects of the distance between adjacent two sprinklers and the height of sprinklers on the uniformity of lateral distribution of water. According to the water distributions measured by employing a single sprinkler, a water distribution model was built for a linear move irrigator.Field tests and simulation results showed that a variable vertical irrigation could be got by changing the frequency of the motors, while the uniformity of irrigation in the lateral direction depended on the type and pressure of sprinkler. The maximum relative error between field test and simulation is 339％, suggesting the simulation model is reliable. This outcome provides a means of investigating effect of irrigation and parameter optimization for a linear move irrigator.
2012 Vol. 30 (5): 603-608 [Abstract] ( 2061 ) [HTML 1KB] [ PDF 31032KB] ( 1116 )
609 Removal effect of eco ditch and wetland system on nitrogen in paddy field drainage water
HE Yu-Pu, PENG Shi-Zhang, XU Jun-Zeng, ZHANG Jian-Gang, JIAO Jian, YU Jia-Hong
The change in nitrogen concentration and distribution feature of carbontonitrogen ratio in the agricultural ditch and wetland system were analyzed based on the observed data in fields to investigate the nitrogen removal effect from drainage water in the system under a controlled irrigation and drainage condition. Results showed that TN，NH+4-N and NO-3-N concentrations in drainage were peaking after fertilization and then were significantly reduced after agricultural ditches were made to store water, causing 63.9% 67.8% and 83.2% nitrogen removal efficiencies in TN, NH+4-N and NO-3-N, respectively. The nitrogen concentration was reduced further after the drainage water was purified in wetlands, resulting in 47.7%, 44.3% and 82.0% average removal efficiencies for TN, NH+4-N and NO-3-N. Since the influence of organic matters on water quality is little under the controlled irrigation and drainage condition, a low carbontonitrogen ratio was maintained in general. The agricultural ditch and wetland system are effective in removing nitrogen in paddy field drainage water. However, the influence of low carbontonitrogen ratio on the Nitrogen removal efficiency is little under a controlled irrigation and drainage condition.
2012 Vol. 30 (5): 609-613 [Abstract] ( 2047 ) [HTML 1KB] [ PDF 1043KB] ( 2178 )
614 Wells distribution layout in irrigation district based on water supply and demand balance analysis
LI Yan-Gang, Wei-Xiao-Mei, Cai-Ming-Ke, Xu-Yi-He, Hu-Guo-Jie
Lack of reasonable and scientific planning of well layout is one of the most important reasons for the imbalance problem of groundwater supply and demand in the north irrigation districts of China. Baojixia irrigation district was used as the study model and based on its comprehensive groundwater resources， the types of groundwater development and utilization were classified. According to water supply and demand balance analysis under both sufficient insufficient irrigation conditions, the various schemes of groundwater extracting scale were figured out. A reasonable groundwater mining scale was determined based on the numerical simulation of groundwater to reduce the shortage rate of irrigation water and to balance the extraction and supply. Two methods, namely traditional method and GA optimization method， were applied to calculate the number of pumping wells， single well irrigating area and distance between two wells so as to determine a reasonable layout of well distribution in the irrigation district. The results showed that in the second scheme not only the less change in the groundwater level is obtained, but also extraction almost equals to infiltration of water and the water shortage rate is controlled in around 1%, and subsequently a sustainable groundwater utilization will be realized. According to the current number of wells, additional 53 wells should be drilled in the highland and the 242 wells should be reduced in the lowland in that irrigation district.
2012 Vol. 30 (5): 614-620 [Abstract] ( 1977 ) [HTML 1KB] [ PDF 1022KB] ( 2102 )
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主管单位
 江苏省教育厅
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 江苏大学
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 中国农业机械学会排灌机械分会
 国家水泵及系统工程技术研究中心
 中国农业工程学会农业水土工程专业委员会
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徐云峰  张文涛 陈建华
谈国鹏  朱漪云 盛    杰
　

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