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Journal of Drainage and Irrigation Machinery Engin
 
2012 Vol.30 Issue.2
Published 2012-03-30

article
Article
125 Effects of diffuser vane on mixedflow pumps performance
BING Hao, CAO Shu-Liang, TAN Lei, LU Li
A series of vaneddiffusers, which are with various vane inlet angles, vane angle distributions along streamline, leading and trailing edge positions, were designed for a mixedflow pump impeller by using the pointbypoint integration method that was applied to generate the threedimensional camber of vane on the streamlines determined by employing an iterative calculation between two kinds of relative stream surfaces. The vane thickening and leading and trailing edges smoothing were conducted on a plane of conformal mapping.3D turbulent flow fields inside the mixedflow pump with the same impeller but different diffusers were simulated by solving the Reynolds timeaveraged N-S equations and the standard k-ε turbulence equations based on SIMPLE algorithm, and the pump hydraulic efficiencies were predicted, consequently, the correlations of both the vane wrap angle and hydraulic efficiency to different design parameters were obtained. In addition, effects of various design parameters on the mixedflow pump performance were analyzed by means of relative velocity, static pressure and total pressure distributions in the inlet and outlet to the diffusers.The results showed that the diffuser vane inlet angle has the strongest influence on the performance and a reasonably selected inlet angle can reduce the shock loss. The vane angle distributions along streamlines should be selected by considering the control of wrap angle to reduce the hydraulic friction loss in diffuser. The leading edge and trailing edge positions should be selected with the consideration of static pressure recovery ability and hydraulic friction loss across diffuser.
2012 Vol. 30 (2): 125-130 [Abstract] ( 5580 ) [HTML 1KB] [ PDF 6901KB] ( 2934 )
131 Effects of number of blades on flow induced vibrationand noise of centrifugal pumps
TAN Ming-Gao, WANG Yong, LIU Hou-Lin, WU Xian-Fang, WANG Kai
The present state of research on flow induced vibration and noise of centrifugal pumps was introduced. Based on the virtual instrument data acquisition system and a routine pump test system, a closedloop test rig was established for measurement of flow induced vibration and noise in centrifugal pumps. A synchronous acquisition was realized for pump performance parameters and flow induced vibration and noise signals.  A singlestage, endsuction centrifugal pump with 5 blades, whose specific speed was 93, was chosen as the experimental model. The additional impellers respectively with 4, 6 and 7 were made and tested in the same volute. The performance of pumps with those four impellers were measured in the whole flow rate, the vibration and noise signals were recorded and processed as well. The experimental results show that the highest vibration intensity is observed in the pump with 5 blades. With increasing flow rate, the vibration intensity level keeps constant initially and then significantly rises. The frequency of noise issued from the pumps mainly was in the range of 0-2 000 Hz. With increasing number of blades, the peak shaft frequency augments gradually at small flow rates. Those outcomes will be instructive and helpful for establishing a hydraulic design method to ensure centrifugal pumps with a low level of flow induced vibration and noise. 

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2012 Vol. 30 (2): 131-135 [Abstract] ( 3300 ) [HTML 1KB] [ PDF 2218KB] ( 3664 )
136 Flow simulation and vortex structure analysis of multinozzle jet pumps
LONG Xin-Ping, YAO Xin, YANG Xue-Long
Based on the finite volume method and Realizable k-ε turbulence model, the flow field inside multinozzle jet pumps was investigated numerically. The calculation reliability was validated by experimental data. Based on the simulation results of streamwise and spanwise vorticity distribution and their peak value variation, the mixing mechanism of the two fluids was analyzed. The results show that the multinozzle could promote the mixing and improve pump efficiency. The vortex has great effects on the mixing. Relative to the streamwise vorticity, the spanwise vorticity value is large and the attenuation becomes flat. The streamwise vortex plays a major role in the mixing. The value and attenuation rate of streamwise vorticity determine the effect of the mixing in the throat. For a definite vorticity value, the greater the streamwise vorticity value is, the faster it decays. The smaller the spanwise vortex size, the faster the mixng, and the higher the pump efficiency. The vorticity distribution in the throat indicates a central nozzle may lead to greater losses. The optimum distribution is that all the nozzles are on a circle.
2012 Vol. 30 (2): 136-140 [Abstract] ( 3206 ) [HTML 1KB] [ PDF 2043KB] ( 3210 )
141 Numerical simulation of acoustic performance of Helmholtz   watermuffler for centrifugal pumps
YUAN Jian-Ping, JIN Rong, CHEN Hong-Liang, FU Yan-Xia, SUN Wei
In order to reduce the noise issued from centrifugal pump pipelines, the pressure fluctuations at the pump were calculated under different operating conditions by using the software Ansys CFX. The pressure fluctuations characteristics were investigated. Moreover, the acoustic performance of Helmholtz watermuffler with inner and outboard neck, different lengths of neck, parallel necks, series and parallel resonator cavity was analyzed by means of the acoustic software Sysnoise.  The simulated results show that the length of neck, connection type between neck and resonator cavity affect the resonant frequency and transmission loss of Helmholtz watermuffler regularly. One more resonant frequency can appear in series and parallel resonator cavities, but the resonant frequencies in series cavities move towards both ends of the resonant frequency of each single cavity with slightly degraded transmission loss. Further there are interactions among the resonant frequencies in the cavities. The resonant frequencies in parallel cavities move towards the inside of two resonant frequencies each single cavity with increased transmission loss. Meanwhile, the interactions among the resonant frequencies in the cavities do not exist.
2012 Vol. 30 (2): 141-146 [Abstract] ( 3327 ) [HTML 1KB] [ PDF 1967KB] ( 2863 )
147 Theoretical calculation of axial clearance in medium or high pressure external gear pumps
LI Yu-Long, SUN Fu-Chun
The study on theoretically estimating variable axial clearance in a medium or high pressure external gear pump is rare yet, thus a dynamics model for determining such a clearance was established in the paper based on an analysis on forced acted on a floating axial sleeve (side plate), which consisted of the pressure in squeezed film, the outside compensated forces on the sleeve, the pressure in trapped oil and the working oil pressure. Then variable axial clearances were iteratively estimated from the model in a meshing cycle by using the Runge-Kutta method. Subsequently, an analysis on the influence of compression ratio, different distributions of working oil pressure and trapped oil pressure on the clearance value was conducted. The results show that the axial clearance is about 0.13 mm in all the cases, and it is consistent with the actual value. The greater the total force of oil pressure due to the different distributions of operating oil pressure at the same compression ratio, the smaller the axial clearance. As the other conditions remain unchanged, the higher the compression ratio, the smaller the axial clearance. Moreover the operating oil pressure and compression ratio have a significant impact on the clearance, but the trapped oil pressure just has slight effect on it. Generally, in a medium or high pressure external gear pump the axial clearance really shows less variable, so that the mean value of the variable clearances can be applied in design to simplify subsequent calculations.
2012 Vol. 30 (2): 147-152 [Abstract] ( 5391 ) [HTML 1KB] [ PDF 1741KB] ( 4207 )
153 Analysis on flow field in Vshape valveless piezoelectric pump with single oscillatordual chamber
HE Xiu-Hua, LI Fu, BI Yu-Shi, DENG Zhi-Dan, WANG Jian
A kind of Vshape valveless piezoelectric pump with single oscillatordual chamber was designed and its geometric model was created.Its internal flows were numerically analyzed by the dynamic mesh model in Fluent. The unsteady flow field in the piezoelectric pump was simulated and the pump unsteady characteristics, such as instantaneous pressure, velocity and flow rate in different periods of time, were obtained. If the dynamic characteristics of the twochip piezoelectric vibrator was effectively combined with the fluid dynamics, the estimated pump performance would agree with the theoretical characteristics of valveless piezoelectric pumps, it is suggested that the dynamic mesh model is feasible in the numerical simulations of flow in such a pump. The effects of driving frequency, amplitude of the piezoelectric vibrator, pump chamber height and location of the Vtube on the pump output performance were studied by means of considerable numerical simulations. The simulation results show that the maximum outlet flow is obtained at the driving frequency of 250 Hz. Moreover, the greater the amplitude of the piezoelectric vibrator, the higher the outlet flow. When a set of amplitude, pump chamber height and Vtube location are determined reasonably, the output of a piezoelectric pump can get the best performance.
2012 Vol. 30 (2): 153-156 [Abstract] ( 2967 ) [HTML 1KB] [ PDF 1871KB] ( 2113 )
157 Optimization design of submersible pump rotor system for coal mine based on Ansys
CAO Wei-Dong, GAO Yi, WANG Xiu-Lan, XU Rong-Jun
The flow passages and rotor system of a coal mine submersible centrifugal pump were built by the 3D software Pro/E, and an unstructured mesh was generated in the passages with the software ICEM. The characteristics of such a multistage pump were estimated through the code CFX at different operating conditions based on the Reynolds timeaveraged Navier-Stokes (RANS) equations combined with the standard k-ε turbulence models and SIMPLEC scheme, and compared with experimental data, their reliability was confirmed. The simulated fluid flow results were input into Ansys Workbench to calculate the modes of the rotor system with two pivots by using fluidstructure interaction method, it was found that the first order critical speed of the rotor system was lower than the pump rotational speed. According to the deformation patterns of the rotor system the rotor system was redesigned with three pivots, the calculated critical speed of the new rotor system met the design requirement. Obviously, the life span of bearings will be extended. The results show that the quick damage of bearings 7217AC/DB and serve erosion of wearrings are mainly due to the too low critical speed of the original rotor system. The critical speed of the threepivot rotor system is higher than the pump rotational speed and it will greatly improve the reliability of both bearings and sealingrings.
2012 Vol. 30 (2): 157-161 [Abstract] ( 4651 ) [HTML 1KB] [ PDF 2031KB] ( 3065 )
162 Numerical analysis of power loss on counterweight in scroll compressor
LI Chao, LIANG Qiu-Li, ZHAO Man
The counterweight that rotates with the crankshaft in a scroll compressor has an interaction with the surrounding gas. In order to study the power loss due to such an interaction and counterweight geometrical effect on the loss, the flow domain in the housing that accommodates the counterweight was established by means of the moving mesh technique in CFD software Fluent. The resistance moment and power loss of the counterweight under different rotational speeds were obtained. Meanwhile the pressure distribution on the three counterweights and the effect of counterweight structure on both the resistance moment and power loss were analyzed too. The results show that the moment due to the pressure difference over the surfaces of the counterweight is too much larger than the moment generated by the skin friction during rotation, thus the pressure differential moment is the major cause for power loss production. Both kinds of moment are increased with increasing rotational speed. After the counterweight edges were modified with chamfer; the pressure differential moment was reduced by the improved flow condition around the counterweight so considerably that the power loss was lowered by more than 20%.
2012 Vol. 30 (2): 162-166 [Abstract] ( 2673 ) [HTML 1KB] [ PDF 1670KB] ( 2123 )
167 Influence of impeller and guide vane blade number on pressure fluctuation in mixedflow pump
ZHANG De-Sheng, SHI Wei-Dong, WANG Chuan, WANG Guo-Tao, ZOU Ping-Ping
To investigate into the pressure fluctuation feature caused from the rotorstator interaction between the impeller and the diffuser in a mixedflow pump, the unsteady flow field in the pump with different numbers of blades in the impeller and the diffuser were numerically simulated based on the standard k-ε turbulence   model, SIMPLEC algorithm and sliding mesh model. The pressure fluctuation data were acquired by monitoring fluid pressure at the points located at the impeller and diffuser. The influence of number of blades and blade thickness on the pressure fluctuation was discussed in timedomain. The results show that the number of impeller blades is the main factor causing pressure fluctuation in the whole flow field. The pressure fluctuation amplitudes in the inlet and outlet to the impeller is consistently increased when the number of impeller blades is reduced; while the pressure fluctuation at the impeller outlet and in the diffuser is less affected by the number of guide vanes. Those conclusions will provide a reference for hydraulic design of mixedflow pumps and their stable operations.
2012 Vol. 30 (2): 167-170 [Abstract] ( 4338 ) [HTML 1KB] [ PDF 1902KB] ( 3372 )
171 Cavitation performance research of mixedflow pump based on CFD
CHANG Shu-Ping, WANG Yong-Sheng
The cavitating flow in a mixedflow pump under the design working condition was simulated numerically with the SST turbulence model and homogeneous mixture cavitation model based on the Rayleigh-Plesset equations by solving the timeaveraged Navier-Stokes equations.  The NPSHH curve was extracted from the results, the cavitation inception and development were captured as well. The features of vapour volume fraction distribution in the impeller were comparatively analyzed under the slight, critical and severe cavitation conditions. The results show that this pump has met the requirement on its cavitation performance. A cavity appears firstly on the blade suction surface near the leading edge and the shroud, as NPSH is reduced, it extends towards the hub and trailing edge.The tip cavity originates from the blade leading edge and develops into a strip along a blade contour on the shroud. The hub cavity accumulates near the blade trailing edge on the hub, further the vapour volume fraction on the hub is evidently larger than on the shroud. A similar cavity distribution is indentified in all the impeller passages, and the serious blockage due to cavity in the flow passages results in a sharp reduction in pump head under the sever cavitation condition.
2012 Vol. 30 (2): 171-175 [Abstract] ( 3991 ) [HTML 1KB] [ PDF 2070KB] ( 3003 )
176 Cavitation performance prediction of engine cooling water pump based on CFD
LI Wei, SHI Wei-Dong, ZHANG Hua, PEI Bing, LU Wei-Gang
The threedimensional turbulent flow in an engine cooling water pump with the impeller, which has ever been severely damaged in operation, was simulated employing the timeaveraged N-S equations, the standard k-ε turbulence model and multiphase flow model by CFX software. The characteristics and cavitation performance were predicted and the reasons for the impeller damage were clarified by observing the flow variable distributions in the impeller of the pump. The numerical simulation results indicat that the critical NPSH of the pump is about 10.7 m at 85 ℃, and a serious cavitation occurs under zero gauge pressure, it is suggested that cavitation causes the impeller damage. The experimental head of the pump is 6.1 m at the design flow rate of 285 L/min, it is well below the numerical simulation head under room temperature, thus a serious cavitation has occurred in the real operating conditions; such a conclusion based on the predicted results is basically consistent with the experimental observations.The numerical results provide a theoretical basis for improving the cavitation performance or preventing from or mitigating cavitation in an engine cooling water pump.It offers a fast and precise computational method for simulating and identifying cavitation damage in engine cooling water pumps as well.
2012 Vol. 30 (2): 176-180 [Abstract] ( 3494 ) [HTML 1KB] [ PDF 1752KB] ( 3729 )
181 Calculation of water critical depth in channels with common shapes
LIU Ji-Liang, WANG Zheng-Zhong, SU De-Hui, YANG Xiao-Song, LIU Quan-Hong
The existing methods for calculating critical depths of open channels were summarized and their characters have been clarified.  In order to identify simple, universal, accurate explicit equations for calculating the critical depth in open channels with typical crosssections, two dimensionless variables related to channel crosssection geometry and discharge were defined. Then, those explicit equations available for five sorts of open channels with typical crosssections in literature were expressed by the dimensionless variables, thus the most appropriate ones could be selected by comparing their complexity, accuracy and application range. Also, by applying the best approximations algorithm, a new explicit equation expressed as a series of piecewise power functions was developed for the openchannel with standard citygate crosssection. For the new equations, the results of error analyses indicate that all the maximum relative errors in critical depth are less than 1% in the channel normal application range. The results of the study may provide a reference for the design and hydraulic calculations of typical open channels applied in drainage and irrigation.
2012 Vol. 30 (2): 181-187 [Abstract] ( 7134 ) [HTML 1KB] [ PDF 1615KB] ( 5255 )
188 Sand abrasion characteristics of materials for hydroturbines
REN Yan, ZHANG Lan-Jin, LI Yan-Pin, CHEN De-Xin
To prevent from or relieve sand abrasion of hydroturbines in hydropower stations on the Yellow River in a more scientific manner, it is necessary to investigate the abrasion characteristics with real sands in that river. The sediment sand in that river bed located at Huayuankou in Zhengzhou was applied into the sand abrasion characteristics measurements of the steels 1Cr18Ni9Ti and ZG0Cr16Ni5Mo in the laboratory. The flow conditions were based on the actual situation of flow in Sanmenxia Hydropower Station sited on the Yellow River. The weight loss and its rate against time of these two kinds of materials for hydroturbine were measured at three sand concentrations, six different water steam velocities. The correlations such as material weight loss to time, steam velocity and sand concentration were obtained through the analyses on the experimental results. Eventually, the mathematical models of sand abrasion characteristics were established by using the regression methods for these two materials. It was shown that weight loss is increased with increasing stream velocity for all the materials, the weight loss rises with increasing sand concentration at a constant velocity, also, the longer the time is lasted in measurements the more the weight loss gets. The obtained regression equations suggest that the material weight loss is approximately proportional to the third power of stream velocity, the first power of both sand concentration and time under those experimental conditions.
2012 Vol. 30 (2): 188-191 [Abstract] ( 2910 ) [HTML 1KB] [ PDF 1832KB] ( 2544 )
192 Numerical simulation of unsteady cavitating flow around hydrofoil
YANG Min-Guan, YIN Bi-Xing, KANG Can, SUN Xin-Kai, CHE Zhan-Fu
Based on the Reynolds timeave raged N-S equations, the unsteady cavitating flow around ys930 hydrofoil was simulated by the RNG k-ε  turbulence model and the mixture twophase caviatation model. The characteristics of unsteady cavitating flow and the cavity evolution process around the hydrofoil at a 10 deg attack angle at three cavitation numbers 1.0, 0.8 and 0.5 were obtained. The results show that there are two parts in a cavity, the front part is attached to the suction surface of the hydrofoil and full of water vapor. The rear part is the periodic, unsteady, collapsible twophase flow zone. The attaching point of the front part is basically stable, the length of the cavity initially is increased, subsequently decreased. The length is decided by cavitation number and strength of reentrant jet simultaneously. The thickness of the cavity firstly rises, and then is reduced. The smaller the cavitation number, the closer to the trailing edge of the hydrofoil the maximum thickness location. The strength of reentrant jet is inversely proportional to cavitation number, the smaller the cavitation number, the lower the strength of reentrant jet. Moreover the position of the detaching point of cavity is determined by the interaction between the coming flow and the reentrant jet.
2012 Vol. 30 (2): 192-197 [Abstract] ( 2985 ) [HTML 1KB] [ PDF 2285KB] ( 2348 )
198 Variation characters of droplet coverage area in leaf droplet water uptake process
GAO Jian-Min, AN Gui-Ren, LIU Chang-Jian, HUANG Gui-Zhen
In order to provide useful data for theoretical investigations into aeroponics, foliar fertilization and plant protection equipment development, the process of plant tissue absorbing droplet was conducted. A chamber with controlled environment (100% relative humidity and 20 ℃ temperature) was designed to observe the change in the coverage area of a droplet on a leaf with time. To eliminate the influence of droplet evaporation, three droplets respectively with 238.77, 229.92 and 212.60 μm diameters were employed to verify droplet evaporation rates. The evaporation rates of three droplets were 1.43%, 2.8% and 3.1% at the interval of 600 s respectively. Two droplets with the diameters of 340 and 540 μm were employed to conduct the droplet foliage uptake experiments. The experimental outcomes suggest that the change rate of coverage area of droplet depends on the position where a droplet is dripped and the time elapsed when the droplet is on the foliage.
2012 Vol. 30 (2): 198-202 [Abstract] ( 2536 ) [HTML 1KB] [ PDF 1917KB] ( 2410 )
203 Experiment on hydraulic performance of selfcleaning screen filter
LIU Huan-Fang, LIU Fei, GU Chen-Chen, ZONG Quan-Li, LUO Xiu-Ping
The hydraulic performances were experimented by using clean and muddy water, respectively. The filter minor head loss coefficient was measured at various flow rates (0-230 m3/h) for clean water. The filter sand filtration and drainage behaviors were studied in muddy water. Firstly, the minor head loss coefficients were measured at various sand concentrations in the muddy water at the highest flow rate 230 m3/h. Secondly, the coefficients were tested once again at various flow rates for a constant sand concentration of 0.19 g/L. The optimal periods of time for discharge of sands were measured at a series of given pressure differentials across the filter, however, for the drainage behavior. The results show that for the clean water the coefficient is increased slowly in increasing flow rate in 0-140 m3/h, however, it rises rapidly when the flow rate is 140-230 m3/h. The empirical formulas have been proposed based on those head loss experimental data. For the muddy water, once the head loss is beyond 6-7 m, the loss will be increased rapidly with sediment concentration. During the experiments on drainage behavior, when the period of time for drainage sand reaches 20 s, the sediment concentration downstream tends to keep stable and a good result is achieved sand drainage, suggesting the optimal drainage time is in 20-30 s under the given pressure difference of 0.07 MPa across the filter.
2012 Vol. 30 (2): 203-208 [Abstract] ( 4815 ) [HTML 1KB] [ PDF 2076KB] ( 2470 )
209 Processing of laser surface microtexturing on surface of SiC mechanical seal
FU Yong-Hong, WANG Zu-Quan, JI Jing-Hu, YANG Dong-Yan, FU Hao
 The laser surface texturing on the SiC mechanical seal samples were studied by using a Qswitched diodepumped Nd:YAG laser and the laser processing technique called “single pulse at a time, repeated at intervals”, and the geometric parameters of texture were measured by means of WykoNT1100 surface profiler, further the effect of laser processing parameters (pumping current, repetition frequency, number of excitations, scanning speed) on the geometrical parameters and quality of microtextures was analyzed. The results show that pumping current and number of excitations have an evident influence on the micropore processing quality, and repetition frequency is relatively small. However,pumping current, scanning speed and repetition frequency can greatly affect microgroove processing quality. High quality microtextures can be obtained via optimizing the laser processing parameters. For processing microdimple, the optimal laser parameters, such as pumping current and number of excitations are 14-16 A, 1-10, for processing microgroove. However, the optimal pumping current, repetition frequency and scanning speed are 14-16 A, 1 500-2 500 Hz and 8-25 mm/s, respectively.
2012 Vol. 30 (2): 209-213 [Abstract] ( 3537 ) [HTML 1KB] [ PDF 1848KB] ( 3534 )
214 Design and experimental study on relief valve with permanent  magnetic compression spring
SI Guo-Lei, YANG Feng-Yu, WANG Wen-Jie, LI Zheng-Gui
Because the helical compression spring has frequently suffered from various failures, such as fatigue fracture, corrosion cracking, relaxation, plastic deformation, permanent deformation during its operation in hydraulic components, a noncontact design concept was put forward for the relief valve by making use of permanent magnetic compression spring, and then the basic structure, working principle, electromagnetic force, stiffness characteristics for the valve were studied. Initially, a permanent magnetic compression spring was designed by means of analytical calculation and experimental validation so that the characteristics that magnetic force is superior to helical mechanical compression spring has been made full of use. Then a relief valve was constructed with the spring, eventually the valve performance was measured. The results show that the magnetic force keeps to be a near constant 70±5 N when the gap between the permanent magnet valve core and the valve base is 0.4-1.2 mm. During the step response test, the pressure fluctuation in the relief valve with permanent magnetic compression spring is 11.7%, compared with 22.8% in the valve with a helical mechanical compression spring. For the same technical specifications, the size of the valve with permanent magnetic compression spring is 37.5% smaller than one with a helical compression spring. Thus, we can make full use of the advantage of permanent magnetic compression spring in hydraulic valves, nevertheless further investigations still are on demand.
2012 Vol. 30 (2): 214-218 [Abstract] ( 2851 ) [HTML 1KB] [ PDF 1599KB] ( 2817 )
219 simulation and transient model for regulating period of gate valve
TANG Yue, TANG Ling-Di, LIU erHui
To investigate the transient characteristics and internal flow in the pipeline of pump system during regulating period of a valve, a onedimensional simulation model which contains the pipes, pump and valves etc has been established by software Flowmaster. CFD code Fluent 6.2 was used to solve the incompressible threedimensional transient turbulent N-S equations with the dynamic mesh method to deal with the moving boundary caused by the opening valve core. The simulation results show that the valves with linear and logarithmic regulating characteristic have a fast opening feature which means the flow rate is very sensitive to the valve opening degree, in addition the water hammer pressure falls down promptly when the relative opening degree is in the range of 10% to 20%. As the valve relative opening degree is reduced, the flow behind the valve becomes disorder, leading to great hydraulic losses and considerable drag coefficient. For instance, the drag coefficient of valve under transient period shows great difference from that under static condition when the relative opening degree is less than 0.5. These analyses show that the transient behavior and unsteady internal flow pattern cannot be handled by the existing usual analytical steady flow models during regulating period of a valve, especially at a relatively small opening degree. In that case, the steady flow models are subject to be amended in some degree to allow them to provide correct computational results.
2012 Vol. 30 (2): 219-224 [Abstract] ( 3863 ) [HTML 1KB] [ PDF 2346KB] ( 3220 )
225 Linear stability analysis for charged viscid liquid jets
WANG Xiao-Ying, WANG Jun-Feng
Based on the linear instability theory, the perturbed pressure and electric fields were analyzed and the dispersion equation of charged viscid liquid jet was established by force characteristics analysis. Through numerical computations, the influence of jet velocity, charged voltage and viscosity on the instability of charged jet were obtained. The results show that with increasing jet velocity and charged voltage, the maximum of wave growth rate, corresponding optimal wave number, and the maximum of wave number get larger, and the droplet size gets smaller. Viscosity always makes the jet more stable. When viscosity is higher, the maximum of wave growth rate and corresponding optimal wave number get smaller so that the droplet size is bigger, but the maximum of wave number remains unchanged. For the jet with a velocity in the range of 0 to 1 m/s, the 0order wave always exists regardless whether the jet is charged or not. The 1order wave appears on the surface of uncharged liquid jet only when the jet velocity reaches a certain value and high voltage makes the 1order wave occur in a lower jet velocity. The 0order wave is dominant in jet breakup because the maximum growth rate of 0order wave is larger than that of 1order wave.
2012 Vol. 30 (2): 225-230 [Abstract] ( 2731 ) [HTML 1KB] [ PDF 1820KB] ( 2234 )
231 Broadcasted fertilizer solute transport model in 2D surface water flow of border irrigation: Ⅱ. Validation
ZHANG Shao-Hui, XU Di, LI Yi-Nong, BAI Mei-Jian
The twodimensional surface water flow and solute transport model of border irrigation with broadcasted fertilizer was validated by using the experimental data according to the views of the traditional average relative error and the Markov stochastic process.From the view of the conventional average relative error, the average errors in water advance and recession phases are 4.98% and 9.37%, and the water balance error is 0.28%, the average errors in solute concentration at every observed point are 8.64%-14.22%, and the solute balance error is 0.58%. Thus the proposed model can successfully simulate the water and solute transport processes in border irrigation with broadcasted fertilizer. From the view of Markov stochastic process, the microtopography stochastic effect on the simulated results is 88.68%-96.21%, and the soil surface stochastic effect which isn′t involved in the model is 3.97%-11.32%, so that even the model just includes the microtopography randomness, it has a good simulation performance. Consequently the proposed model provides a practical and perfect numerical tool for evaluating the performance of border irrigation with broadcasted fertilizer.
2012 Vol. 30 (2): 231-236 [Abstract] ( 2601 ) [HTML 1KB] [ PDF 1958KB] ( 2129 )
237 Simulation experiments on soil water movement in multiple point sources drip irrigation
ZHANG Lin, WU Pu-Te, ZHU De-Lan, FAN Xing-Ke
In order to provide a guide to reasonable design of drip irrigation system for closegrown crops, soil water movement in drip irrigation of multiple point sources was simulated by indoor physical experiment.The spatialtemporal dynamic distribution of soil water was mainly studied under different emitter discharge rates.There were three stages in the infiltration, namely, point source infiltration, overlapped wetting front and wetting belt.The characters of soil water distribution were complex in the upper zone and relatively simple in the lower zone in the wetted volume.In the upper zone of wetted volume, there was a region with higher soil water content under the emitter and a zone with lower water content near the surface between two emitters.The soil water content tended to be uniform on the same layer in the lower zone of wetted volume.After the end of irrigation,difference in water content on the same layer in the wetted soil was decreased due to soil water redistribution.Compared to a higher emitter discharge, the infiltration depth was deeper and the average soil water content was lower at a smaller discharge at the end of irrigation for the same irrigation amount.After the irrigation was completed, the difference in infiltration depth was slight for different emitter discharges due to soil water redistribution.
2012 Vol. 30 (2): 237-243 [Abstract] ( 2852 ) [HTML 1KB] [ PDF 3018KB] ( 2405 )
244 Experimental study on electrostatic spraying device with better deposition
JIA Wei-Dong, LI Cheng, WANG Zhen-Tao
Integrating with both the highvoltage electrostatic spray and the axialflow airassisted spray technique, an electrostatic spray device with better deposition for greenhouses was developed.The axial flow velocity, droplet diameter and deposition rate were tested in laboratory. The results show that the axial flow can improve the spray coverage effectively, and plays a significant role in increasing the deposition rate of chemical droplets in the ranges close to the nozzle. In general, when this device is operated at a pressure of 0.4 MPa and a voltage of 40 kV, it can produce smaller droplets by the combined effect of static electricity and axial flow. The axial flow can screen and transport small droplets, causing the droplets have more uniform size distributions in the middle of axial spray range. The distance between a plant and the nozzle depends on the combination between static electricity and axial flow, eventually it affects the deposition rate. For the device, if such a distance is reasonable, a deposition rate that is not less than 50% can be obtained.
2012 Vol. 30 (2): 244-248 [Abstract] ( 3010 ) [HTML 1KB] [ PDF 1582KB] ( 2544 )
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主管单位
 江苏省教育厅
主办单位
 江苏大学
协办单位
 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
主  编
 袁寿其
编辑出版
 《排灌机械工程学报》编辑部
责任编辑
徐云峰  张文涛 陈建华
谈国鹏  朱漪云 盛    杰
 

Links

 
· KSB
· National Research Center of Pumps
                  More 
 

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