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Journal of Drainage and Irrigation Machinery Engin
 
2012 Vol.30 Issue.4
Published 2012-07-30

article
Article
373 Influence of splitter blades on unsteady flow characteristics in centrifugal pump
YUAN Shou-Qi, Ye-Li-Ting, Zhang-Jin-Feng, Yuan-Ye, Zhang-Wei-Jie
Ansys-CFX software was adopted to simulate the unsteady flow field at different operating conditions in an entire centrifugal pump whose impeller was designed with and without splitter blades. To analyze the influence of design parameters of splitter blades on the unsteady flow field of the pump, the splitter blades were designed to have different inlet diameters and circumferential positions. The results show that when splitter blades are added, the pump head increases by 2%-12% and the pressure fluctuations at the impeller inlet, volute outlet and the interface of impeller and volute are reduced, thus the splitter blades have improved the “jetwake” flow structure. The influence of design parameters of splitter blades on the unsteady flow field in the pump is variable. When the inlet diameter of splitter blades is 106 mm and the blades are deviated to the suction side of the full length blades by 5° , the head is the highest and the pressure fluctuations are the lowest.
2012 Vol. 30 (4): 373-378 [Abstract] ( 3026 ) [HTML 1KB] [ PDF 4450KB] ( 2021 )
379 Numerical and experimental investigations on super large area ratio jet pumps
Long-Xin-Ping, CHENG Hong-Gui, YANG Xue-Long, XIAO Long-Zhou
Two jet pumps with superlarge arearatios (574 and 6005), respectively, were designed according to the conventional theory and the engineering requirements. Based on the finite volume method, the Realizable k-ε turbulence model with the standard wall function was adopted in the three dimensional flow simulations and structure optimization of the pumps. The simulation results indicated that the best efficiency point moves to a higher flow ratio and the optimum throat length increases with area ratio. Six jet pumps were manufactured according to the optimized parameters; subsequently their performance was tested under different driving pressures. There were six area ratios through the combinations of two size nozzles and three throat diameters. The experimental data show that the fluid flow inside those pumps has selfsimilarity like a conventional jet pump. The existing theory for predicting cavitation flow ratio overestimates the cavitation performance of those pumps, and it needs to be updated. The experimental data agreed well with the simulation results, confirming the reliability of numerical simulation and the feasibility of structure optimization. The investigation into the pumps with super area ratios has extended the application range of jet pumps.
2012 Vol. 30 (4): 379-383 [Abstract] ( 2797 ) [HTML 1KB] [ PDF 2330KB] ( 1641 )
384 3D PIV measurements of rotorstator interactions in doubleblade centrifugal pump
LIU Hou-Lin, YANG Dong-Sheng, TAN Ming-Gao, WANG Kai, ZHUANG Su-Guo
In order to study the impellervolute interaction in a doubleblade centrifugal pump, the flow in three sections of impeller passages was measured with nine different locations between a blade and the tongue of volute at the best efficiency point. The relative velocity field and axial velocity field are greatly dependent on the distance between a blade and the tongue. When a blade is between the tongue and the section 1 on volute, the flow rate in that passage is the lowest, and the relative velocity field is uniform. Meanwhile, there is a low velocity zone in the corner between the shroud and the blade suction side at the passage outlet, causing a jetwake flow pattern at the impeller outlet. A higher axial velocity range is observed at the passage inlet. As the blade leaves far away from the tongue due to its rotation, the flow rate in the passage is increased, and flow is separated from the blade pressure side, establishing a vortex there. The relative velocity profile at the passage outlet becomes uniform, and the axial velocity at the passage inlet decreases as well. As the blade gets close to the tongue, the flow rate in the passage is reduced, and the scale of the vortex is decreased and disappears eventually. The relative velocity at the blade pressure side outlet is lowered, but that at the blade suction side is increased, meanwhile the axial velocity at the passage inlet continues decreasing.
2012 Vol. 30 (4): 384-389 [Abstract] ( 2941 ) [HTML 1KB] [ PDF 4415KB] ( 1959 )
390 A novel resonantlydriven piezoelectric gas pump
WU Yue, YANG Zhi-Gang, LIU Yong, WANG Long, XIE Hai-Feng
The pumps driven directly by piezoelectric membrane not only have a poor performance when pumping gas, but also they may be damaged with a high temperature generated by the piezoelectric membrane when the flow of gas is blocked. Even though the pumps driven by piezoelectric stack have an excellent performance, they are quite costing. To solve the problems above, a novel piezoelectric pump was presented. The pump was driven by an annular bimorph and the displacement of the diaphragm was amplified at the resonance frequency. Firstly, the working principle of the pump was described, and a mechanic model of vibration was built to clarify displacement amplification principle. The analysis shows that the amplification factor is related to the stiffness of spring lamination and piezoelectric vibrator, viscous damping coefficient of system and driving frequency. The experimental prototypes were manufactured and the experiments indicate that the amplification factor of displacement amplifier is more than 4.2 at a 70 V sinusoidal AC driving voltage, the maximum flow rate could be up to 1 685 mL/min; when the gas flow is blocked, the pump can operate continuously as long as 2 000 h without a noted temperature rise in bimorph.
2012 Vol. 30 (4): 390-394 [Abstract] ( 2897 ) [HTML 1KB] [ PDF 1554KB] ( 2111 )
395 Collector discharge pressure fluctuation of 1 000 MW nuclear reactor coolant pump
ZHU Rong-Sheng, LI Xiao-Long, YUAN Shou-Qi, ZHENG Bao-Yi, FU Qiang
To investigate the collector discharge pressure fluctuation characteristics and the related factors in a 1 000 MW nuclear reactor coolant pump, steady and unsteady 3dimensional numerical simulation was conducted to depict the inner flow inherence and detailed pressure content of a domestic pump model. Both time and frequency domain analysis were further put forward. It is shown that reverse flow is one of the reasons that cause the pressure fluctuations at the joint of the collector and the discharge. Obvious pressure fluctuations exit at the collector discharge and the adjacent area. In addition, the more the operation condition deviates from the design point, the more severe the pressure fluctuations are. The fluctuation amplitude in the upper passage is higher than that in the lower passage. The mean amplitude are 11.5%, 9.62% and 13.78% respectively in the upper passage, while they are 13.62%, 12.53% and 15.79% respectively in the lower one under the flow rates of 0.9Q, 1.0Q, and 1.2Q. At the adjacent diffuser vanes, the fluctuation amplitude near both sides of the casing wall is larger than that near the midspan line. In the regions far from the diffuser outlet, the fluctuation amplitude is increased gradually from the top side wall of casing to the bottom one. The shaft rotating frequency is the major factor influencing pressure fluctuation at ever monitor point when the pump is working at the design point. However, both the shaft rotating frequency and the blade passing frequency  are the main factors when it works at offdesign points.
2012 Vol. 30 (4): 395-400 [Abstract] ( 4567 ) [HTML 1KB] [ PDF 4420KB] ( 1526 )
401 Numerical simulation of transient flow in axialflow pump unit model during runaway caused from power failure
ZHOU Da-Qing, Zhong-Lin-Juan, Zheng-Yuan, Mao-Yuan-Ting
A threedimensional unsteady CFD simulation method was established based on the RANS equations and Spalart-Allmaras turbulence model by varying rotating speed of reference frame and sliding mesh techniques to simulate the transient flow in an axial pump unit model in the runaway caused from power failure. The governing equations of fluid flow are discretized with the finite volume method; the temporal item is approximated with a firstorder backward difference implicit scheme, a secondorder central difference scheme is applied to the source and diffusion items, a secondorder upwind scheme is for the convection items, and the velocitypressure coupling method is chosen to be SIMPLEC. A steady simulation was performed first for providing an initial condition to the transient case. The results showed that the pump attained its runway speed in 20.35 s. The estimated runway speeds were 1 610 r/min and 1 989 r/min by two techniques, comparing with the experimental speed of 1 720 r/min. Additionally, the pump rotational speed, flow rate, torque and static pressure at monitor points against time were revealed during the transient period. These data will provide a reference for pump design and operation of pumping station.
2012 Vol. 30 (4): 401-406 [Abstract] ( 2557 ) [HTML 1KB] [ PDF 3320KB] ( 1518 )
407 Numerical simulation of twophase flow in high shear pulp pump
YE Xiao-Yan, TIAN Ying-Ying, DING Ya-Na, SHEN Liang-Bin, ZHU Li-Kai
In order to study the mixing effect of flow and analyze the flow pattern as well as the velocity characteristics in high shear pulp pump, a geometrical hydraulic model of a high shear pulp pumps was established by Pro/E, and solidliquid twophase flow in it was simulated by using the CFD method based on the mixture model, standard k-ε turbulence model and SIMPLEC algorithm. The meshindependence check was conducted to reduce the influence of mesh size on the results.A series of CFD numerical simulations were carried out under different discharges and rotational speeds, respectively, and the results were compared among the cases to identify their influence on the flow field in the pump. The results show that the mixing uniformity of two phases was improved considerably after the solid phase was sheared in the shearing chamber, suggesting the shear pulp pump exhibited a better mixing and homogenizing effect for the solid phase in flow. The rate of two phases mixing becomes slow when the discharge is increased, and the mixing rate and uniformity of two phases are improved when the rotational speed increases.Note that the mixing rate and uniformity of two phases in the impeller but those in the inlet to the impeller are affected in a great deal by a change in the rotational speed.
2012 Vol. 30 (4): 407-411 [Abstract] ( 2256 ) [HTML 1KB] [ PDF 3067KB] ( 1633 )
412 Experimental study of piezoelectric vibrator deformation and cavity volume fluctuation of piezoelectric pump
In order to precisely get the cavity volume fluctuations of piezoelectric pumps in operation, the deformation characteristic of a circular piezoelectric vibrator, which was one key factor to be responsible for the cavity volume fluctuations, was analyzed and measured in a noncontact manner. The experiment model was a circular piezoelectric unimorph vibrator with substrate and ceramic in the diameters 65 mm and 60 mm,respectively.The relations of amplitude of the center point on the vibrator plane to frequency, driving voltage, and those of amplitude of the points distributed radially in the vibrator subject to a sinusoidal voltage were studied. Based on quadratic functions, the amplitude of each point on the radius was fitted to get the deformation curve by using a Matlab code. According to the fitted curves, a theoretical method for estimating the cavity volume fluctuations was established. The results show that the amplitude of the center point decreases with frequency but increases with driving voltage; the amplitude of each point on the piezoelectric vibrator decreases with radius; the fitted results agree well with the experimental data and the maximum relative error is 6.96% only. According to the theoretical method proposed, it is predicted that under the excitation of sine voltage of 100 V, 30 Hz, the volume fluctuation of pumping cavity is 34.009 mm3, and the theoretical maximum output flow rate is 61216 mL/min.
2012 Vol. 30 (4): 412-416 [Abstract] ( 2146 ) [HTML 1KB] [ PDF 2081KB] ( 1566 )
417 Parametric design of centrifugal pump impellers
ZHANG Ren-Hui, ZHENG Kai, YANG Jun-Hu, LI Ren-Nian
The problems in the optimization design of centrifugal pump impeller were elaborated and it was found that the implicit relation between the hydraulic performance and the complicated geometry shape of impeller passages was a main obstacle. The existing parametric design methods for centrifugal pump impellers, such as the NURBS surface method, freesurface deformation method and partial differential equation method were introduced in detail. To reduce the computational cost, a partial differential equations method was used to control the geometry shape of centrifugal impellers parametrically, the boundary conditions of the equations were parameterized as well.Suppose the parameters a(u,v) are constant and the response surface methodology (RSM) was applied to optimize the design of centrifugal pump impellers, a 2nd order polynomial response surface was constructed according to the trial results.Unfortunately,  it was identified that a 2nd order polynomial fails to present the complicated nonlinear relation between the objective function and the control variables. So the partial differential equations had to be proposed to construct the hypersurface response of objective function. Then a boundaryvalue problem of hyperspace was numerically solved. Eventually, an optimal design of pump impellers was achieved.The result of the optimized design case shows that the proposed theory and method are reasonable.
2012 Vol. 30 (4): 417-421 [Abstract] ( 3156 ) [HTML 1KB] [ PDF 2275KB] ( 2332 )
422 Energy balance of pulse liquid-gas jet pump
Zhang-Jin-Hua, GAO Chuan-Chang, YAN Yong, WANG Xiao-Hui
An analytical expression of energy loss to pressure ratio in the pulse liquidgas jet pump was deduced by using the energy conservation principle and the chef factors influencing the energy conversion of flow were clarified. The effects of energy losses in major flow components on the pump performance were studied, and then were confirmed by experiments and numerical simulations. The optimum area ratio (the throat area over jet area) is 4.34, at which the pump exhibits a higher pressure ratio over a large range of flow rate ratios, based on the experiments made on the pumps with five different arearatios. The results showed that the energy losses in the major flow components estimated theoretically are basically in agreement with the measurements. The energy loss ratios in the flow components were calculated, and their relations with area ratio and flow rate ratio were analyzed. The major parameters affecting the energy balance and performance of a liquidgas jet pump included the frequency of pulse jet, area ratio, flow rate ratio and throat length. By comparing the experimental data of the pump driven by a pulse jet with those driven by a steady jet at various area ratios, it was verified that using pulse jet is an effective way to improve the liquidgas jet pump efficiency.
2012 Vol. 30 (4): 422-427 [Abstract] ( 2470 ) [HTML 1KB] [ PDF 2691KB] ( 1482 )
428 Modeling and analysis of nonlinear hydroturbine governing system with complex penstocks
BA Duo-Duo, YUAN Pu, CHEN Di-Yi, DING Cong
 A nonlinear model was established for a hydroturbine speed governing system with complex penstocks to study nonlinear behaviors of the system. A response curve with critical points of Hopf Bifurcation was obtained through a theoretical analysis. It was shown that the system is stable on one side of the curve but unstable on the other side. The stability of the system was analyzed on both sides of the Hopf bifurcation curve by means of numerical simulations. These simulations not only justified the theoretical analysis but also determined a proper range of PID parameters for a stable governor. The nonlinear dynamic behaviors of the governing system were clarified by using bifurcation diagram, Poincare map, power spectrum diagram, time domain diagram, phase orbits diagram and a spectrum diagram. These analysis methods and results will be useful for allowing a hydropower station in safe operations.
2012 Vol. 30 (4): 428-435 [Abstract] ( 2268 ) [HTML 1KB] [ PDF 5359KB] ( 1533 )
436 Flow pattern and hydraulic performance of tubular pump
Cheng-Li, LIU Chao, B.P.M.van Esch, TANG Fang-Ping, JIN Yan, ZHOU Ji-Ren
In order to establish a relationship between flow pattern and hydraulic performance of a tubular pump, the flow pattern and hydraulic performance at a low flow rate, best efficiency point and a high flow rate were investigated by means of flow simulation, performance test and PIV measurement in a tubular pump. The steady flow field in the pump was obtained through solving the timeaveraged N-S equations in the multiple reference frames (MRF) with the help of the SIMPLEC algorithm and the RNG k-ε turbulence model. The flow patterns in the pump were analyzed at different operating points. There was a large recirculation zone before the blades inlet when the pump operated at the low flow rate. The flow patterns were fine and there was no any reverse flow regions in the pump when it worked at the BEP (Best Efficiency Point) and the high flow rate. The results indicated the hydraulic loss in the suction pipe is similar to that in a normal pipe, but the hydraulic loss in the discharge pipe depended on operating points. A minimum hydraulic loss in the discharge appeared at the BEP. The estimated performance was in agreement with the test data, both the predicted flow patterns and the PIV measurements showed that there was remarked reverse flow region in front of blades near the tip and there existed a large separated flow zone near the hub downstream of blades at the low flow rate. Thus, attention should be paid on the flow pattern in impeller and guide vanes at a low flow rate in the optimal design of such a tubular pump.
2012 Vol. 30 (4): 436-441 [Abstract] ( 2380 ) [HTML 1KB] [ PDF 3781KB] ( 967 )
442 Optimizating pump station operation scheme and pump selection in multi source water injection systems
YANG Jian-Jun, ZHAN Hong, DING Yu-Cheng
In order to optimize the type and number of pumps, operation parameters of pumping stations in multisource water injection systems simultaneously, a mathematical model was established, in which the input power of pumps is objective function, the water balance in system, flow rate and operating pressure as well as type of pumps are served as constraint conditions. Taking the features of this optimization problem in account, a dual coding was proposed to improve the existing genetic algorithm, and then was appied to solve the mathematical model. In that dual coding, a real number was adopted in the row in the coding to indicate the flow rate of a pump, an integer was put into the second row to present the number of a water injection station where the pump was installed; thus, an exact discribtion of the optimization variables was realized; obviously, the coding of solution was in variable length. An approach was porposed, where the type of pump was determined initially according to a flow rate, then the rest operating parameters of the pump were decided based on the known type. In applications of the improved genetic algorithm, the method for generating of initial solutions was given; meanwhile, a variety of crossover and mutation methods, which were adaptable to the optimization problem, were cast. As a result of this, a part of the constraint conditions were satisfied, and the number of infeasible solutions was reduced. The water injection system in an oil field with deep oil wells was optimized by using the algorithm proposed, the total input power was reduced by 2.42%, showing simultaneously optimizating pump seclection and pump operating parameters has a remarkable energy saving effect in the multisource water injection system.
2012 Vol. 30 (4): 442-446 [Abstract] ( 2208 ) [HTML 1KB] [ PDF 1100KB] ( 1641 )
447 Rotational deformability of temperature analogy method
Chen-Yan, ZHANG Qin-Zhao, CAO Shu-Liang
Temperature Analogy Method (TAM) is a new method of generating dynamic grids by using analogy of temperature field. For dynamic grids methods, their rotational deformability depends on the transfer modes of rotational deformation. To investigate the root reasons influencing the rotational deformability of TAM, the transfer modes of rotational deformability were compared among TAM, spring analogy and elasticity approach by using rotating cylinders with different sizes. In doing so, TAM, traditional spring analogy method and its updated version were used to generate the dynamic grids around an airfoil in various rotational angles, respectively. The following results were obtained: First, TAM has a different transfer mode from spring analogy and elasticity approach, i.e. it transfers the rotation of moving boundaries correctly and effectively within the whole computational domain by means of a rotational map. Second, the grid quality of around the airfoil with 90° rotational angle generated by TAM in a single step is better than those around the same airfoil with a smaller than 90° rotational angle generated by the traditional spring analogy method and its updated version in a multiple step. This suggests that TAM is of great advantage in rotational deformability.
2012 Vol. 30 (4): 447-451 [Abstract] ( 2378 ) [HTML 1KB] [ PDF 7629KB] ( 1438 )
452 Tribological property of mechanical seal with laserinduced  multiscale surface texturing
JI Jing-Hu, FU Yong-Hong, WANG Zu-Quan, HUA Xi-Jun, FU Hao
The multiscale surface textures of microdimples and macrogrooves were produced with a Q switched lightpumped Nd: YAG laser using the laser processing technique called single pulse at a time, repeated at intervals. The morphology of the laser textured sample was measured with a 3D profiler. The tribological property of the mechanical seal with laserinduced multiscale surface textures was investigated under different sealing pressures and rotational speeds on a computeraided mechanical seals experimental device and compared with that without textures. The results showed that the regular microdimple and macrogroove textures can be produced on the surfaces of mechanical seal by laser. The tribilogical property of mechanical seal can be improved significantly by the laserinduced multiscale surface textures under the low pressure, low speed and high pressure, high speed conditions during the experiments. The textured mechanical seals exhibited a lower and stable friction torque compared with one without textures. The friction torque of the textured mechanical seal can be decreased by 65% at most. The reason for this is the surfaces textured significantly improve the lubrication condition of a mechanical seal, and the friction torque is decreased eventually.
2012 Vol. 30 (4): 452-456 [Abstract] ( 2636 ) [HTML 1KB] [ PDF 2023KB] ( 1641 )
457 Thermodynamic process of lubricating gas film in dry gas seals with spiral grooves
Han-Ming-Jun, LI You-Tang, SU Hong, DING Xue-Xing, YU Shu-Rong
An analytical pressure distribution function in the gas film is obtained by using the PH linearization and an iterative method without considering deformation of the seal rings based on the Reynolds equation under the sliding boundary conditions. From the equation relating to entropy change of microfluid flow in the spiral grooves, the temperature field in the gas film was obtained. The temperature distribution in the gas film under the different polytropic exponents was analyzed by considering the process of entropy change of the fluid in the spiral groove. The thermoelastic deformation of the seal rings and an approximate analytical formula for the gas film thickness were obtained for different polytropic exponent, the pressure distribution for the thermoelastic deformation was worked out as well based on the generalized Reynolds equation. The leakage through the seals was predicted and compared with the theoretical one without deformation for different polytropic exponents. The results demonstrated that the highest temperature in the film appears inside the seals as a fluid flows inwards and the most significant deformation occurs there. The leakage was increased with deformation, eventually affecting the sealing performance. The leakages under different polytropic exponents were much closer to the experimental measurements. The results can be used as a theoretical basis for optimization design of dry gas seals.
2012 Vol. 30 (4): 457-462 [Abstract] ( 2186 ) [HTML 1KB] [ PDF 2094KB] ( 1445 )
463 Online jet mixing control system of pesticide concentration
CHEN Zhi-Gang, ZHU Shu-Li, QIU Bai-Jing
 The problems such as narrowed adjustable concentration and poor control accuracy are prevalent in common online pesticide concentration control systems in jet mixing process. In order to solve these problems so as to realize an accuracy and intelligent control on pesticide concentration in the process, an advanced control system was developed here. In the system, the control chip—TMS320F2812 produced by TI was used as the hypogynous computer and a humancomputer interaction interface was composed on the host computer in LabVIEW environment. The host and hypogynous computers sharing data was realized by means of the communications between serial ports. The host computer was responsible for data input, display and storage. The hypogynous computer regulated the flow rates of water and pesticide into the mixer, respectively. The analytical relation between the motor rotational speed and the flow rate of water was obtained by fitting their experiment data; similarly, the mathematical relation between the control voltage of the electricmagnetic valve and the flow rate of drug could be gained as well. The control accuracies on the flow rates of both water and pesticide that were pumped into the jet mixing tank were studied at different mixing ratios based on the system. In the experiments, the flow rates of water and drug, the relation between two flow rates were tracked. It was demonstrated that the errors of control on flow rates of water and pesticide were less than 2% and 3%, respectively. Since the mixing ratio of water and drug is adjustable in the concentration control system, a practical ratio can be achieved. As a result, the mixing ratio varying range can be expanded significantly (more than 10 times).
2012 Vol. 30 (4): 463-468 [Abstract] ( 1928 ) [HTML 1KB] [ PDF 1496KB] ( 1523 )
469 Effects of liquid properties on electrostatic spray characteristics
WANG Jun-Feng, WANG Ze, HUO Yuan-Ping, MAO Wen-Long, ZHANG Juan-Juan
Experimental investigation was performed for electrostatic spray of several spray liquids under capillaryannular electrode configuration. The effects of the material properties of the spray liquids and electrode voltage on electrostatic spraying were analyzed through the working parameters of chargemassratio(CMR). Experiments show that in the case of microflow rate ranges, there is almost a linear growth of the applied voltage and the CMR before Rayleigh limit within the right voltage range. Spray liquid electrical conductivity has a great influence on the chargemassratio,the higher the spray liquid electrical conductivity is, the faster the CMR of drops with the electrode voltage increases, and when it is lower, the applied voltage plays a leading role on the CMR. The CMR response is inversely proportional to spray liquid viscosity but proportional to spray liquid surface tension.
2012 Vol. 30 (4): 469-472 [Abstract] ( 1670 ) [HTML 1KB] [ PDF 1806KB] ( 1907 )
473 Design and test of automatic control system of artificially simulating rainfall with variable intensity
Zhou-Qi, CEN Guo-Ping, ZHANG Liang, CHEN Tai-Hong
For artificially simulating rainfall with variable intensity in laboratory, a linear relation between the simulated rainfall intensity and the frequency of flow rate, and that between the frequency and the regulating voltage of electric actuator were established through analyzing the performance parameters of the actuator; subsequently, an automatic control system for such a simulation was designed based on the flow rate regulation of water supply. An automatic control algorithm with variable timestep was proposed based on the LabVIEW language and then applied into gradation control on the water supply in the artificial rainfall system by analyzing the performance parameters of signal acquisition equipment and the voltagemechanical sensitivity of electric actuator. The voltagemechanical sensitivity of electric actuator was 0.2 mm/V, and the minimum control accuracies of frequency of water supply flow rate and rainfall intensity were 7 Hz and 0.053 mm/min, respectively. The experimental results indicated that the relative error between the rainfall intensity achieved and the designed one is less than 4%; the fidelity and the stability of simulated rainfall intensity is above 0.98; the spatial homogeneity coefficient of rainfall intensity is above 0.97; the linear correlation coefficient of rainfall intensity is above 0.75.
2012 Vol. 30 (4): 473-478 [Abstract] ( 3163 ) [HTML 1KB] [ PDF 1404KB] ( 1269 )
479 Amelioration effect of water repellency by tillage
Chen-Jun-Ying, Wu-Pu-Te, Zhang-Zhi-Tao, Xiang-You-Zhen, LI Yuan-Nong
In order to eliminate the negative influence of soil water repellency on agricultural production, two kinds of strong waterrepellent soils (clay and sand) collected from Israel was used to investigate the amelioration effect of tillage on water repellency of soil. Sixteen treatments in total, including four depths (0-2.5 cm, 0-10 cm, 0-20 cm, 0-30 cm) of tillage, planting (cabbage) or not, were set in experimental pots. The treatments with planting were tilled in every 4 months and those without planting weren't tilled during the experiment for one year. Water Drop Penetration Time(WDPT) of soil was measured before and after each tillage applied for every treatment. After analyzed and compared the WDPT, the results show that tillage can eliminate the repellency for a while, but the repellency reoccurs after irrigation for a period of time. The water repellency disappears after the soils experiences many times of tillage; moreover the amelioration effect of repellency shows a significant positive correlation to number, duration and depth of tillage. The amelioration effect of tillage on clay soils is more obvious than on sand ones. The results can provide the evidence that a physics method can improve the water repellency of a soil.
2012 Vol. 30 (4): 479-484 [Abstract] ( 2128 ) [HTML 1KB] [ PDF 3073KB] ( 1616 )
485 Influence of various soil textures and layer positions on infiltration characteristics of layered soils
Li-Yi, Ren-Xin, Horton Robert
In order to compare the effects of layer positions and soil texture variation on infiltration characteristics of layered soil, two types of soils were selected. Ponded infiltration experiments were conducted at three layer positions. The following results were showed: At the three layer positions, 5-10 cm, 10-15 cm and 20-25 cm from soil surface, the time when the wetting front reached the layer interface and the corresponding cumulative infiltration were dependent on the layer positions and soil texture in layers. The upper the layer positions, the shorter the time for the wetting front arriving at the layer interface, and the smaller the corresponding cumulative infiltration.  Effect of infiltration reduction was the best when layer position was 10-15 cm from the soil surface. The deeper the layer position, the more obvious the change in infiltration rate and the higher the infiltration rate curve moved up. Before water entered the layer interface, the cumulative infiltration and wetting front were increased nonlinearly with time; however, once the water was in the interface, they raised in a nearly linear relation against time. There was an approximately linear relationship between cumulative infiltration and wetting front, but their relations varied with the layer positions. Soil moisture distributions in layered soils showed a discontinuity, they were also affected by the soil texture in layers. In general, layer positions had obvious effects on infiltration of layered soils.
2012 Vol. 30 (4): 485-490 [Abstract] ( 2133 ) [HTML 1KB] [ PDF 2607KB] ( 1619 )
491 Effect of initial water content on soil infiltration characteristics during bubble irrigation
Niu-Wen-Quan, FAN Xiao-Kang, Zhou Xiaobo, Chen-Jun-Ying
The effects of initial water content in soil on the soil moisture distribution during bubble irrigation were investigated using repacked soil boxes. Five initial soil Moisture content were tested. The results showed that the initial soil moisture content has less influence on the shape of soil wetted volume but quite large on the volume sizes under the condition of bubbledroot irrigation. The time needed to wet soil surface was reduced and the expansion of the wetting front became fast horizontally and vertically with increasing initial soil moisture content. The higher the initial moisture content, the more uniform the distribution of soil moisture in a wetted soil volume. Empirical equations were fitted with the experimental data to estimate the surface wetted radius, maximum horizontal wetted radius and vertical wetted depth. The IRE and the RMSE between prediction and observation were 0.63%, 0.4%, 083% and 0.59%, 0.12%, 0.73%, respectively, suggesting the empirical equations are applicable for estimate of soil water infiltration parameters in bubble irrigation.
2012 Vol. 30 (4): 491-496 [Abstract] ( 2326 ) [HTML 1KB] [ PDF 2325KB] ( 1079 )
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