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Journal of Drainage and Irrigation Machinery Engin
 
2014 Vol.32 Issue.9
Published 2014-09-25

article
Article
737 Experiments on effects of AC motor water-cooling device on performance of centrifugal pump
Lu Jiaxing, Yuan Shouqi, Yuan Jianping, Si Qiaorui, Luo Yin
The noise of AC motor cooling fan may be decreased effectively by employing a water-coo-ling system compared with a usual air-cooling system. In this paper a kind of water-cooling device is designed to simulate the cooling water circulation process in an AC motor. The noise levels of the centrifugal pump with cooling fan and with water-cooling device are measured at various flow rates, respectively. Furthermore, the pump hydraulic and suction performances are tested for the devices with 6 mm and 10 mm diameter discharge nozzles and compared with the corresponding performances of the original pump. It is shown that the noise level of the original pump is reduced at least by 8.70 dB. The device with 6 mm diameter discharge nozzle can take away the heat generated by the AC motor and is subject to a little influence upon the hydraulic and suction performances. Interestingly, that device can raise the pump head at a low flow rate. Even though the device with 10 mm diameter discharge nozzle can improve the head over the 0-15 m3/h flow rate range, particularly the head is increased by 0.30 m at the shut-off condition, unfortunately, both the hydraulic and suction performances are degraded notably by the device, especially at a high flow rate. The increased leakage or volumetric loss in the pump caused from the enlarged nozzle diameter is responsible for the performance degradation.
2014 Vol. 32 (9): 737-741 [Abstract] ( 1840 ) [HTML 1KB] [ PDF 3644KB] ( 804 )
742 Status and prospect of study on energy recovery hydraulic turbines
Wang Xiaohui, Yang Junhu, Shi Fengxia
Development and application of hydraulic turbine-based energy recovery technology have important significance in energy saving and emission reduction. Hydraulic turbines have been extensively used in petroleum, chemical and fertilizer industries, etc.; however, their design theory and method are imperfect, and their operation is subject to some instabilities as well, thus related studies on them are desirable. In this review, the application, structure and installation of energy recovery hydraulic turbine are described. It is shown that there are four sorts of structure for the turbine, namely pump as turbine, impulse turbine, guide-vane turbine and specialized turbine. The power transmission configuration of the turbine is in two modes, i.e. directly either a pump or a blower and indirectly driving a pump or a blower via a motor. Further, the achievements in the study on energy recovery hydraulic turbines obtained in China and aboard have been reviewed. The turbine selection, optimization design of runner, speed control, hydraulic thrust, structure strength and slip effect of velocity in the turbines are discussed. Finally, the development of hydraulic turbine-based energy recovery technology is prospected. The expected key study issues have been made clear, including:(1)to design and develop novel turbines that are suitable for various operating conditions and improve the total efficiency of the turbines,(2)to decide operation parameters of an energy recovery installation correctly to ensure the turbine operating stability,(3)to choose a feasible regulating method to recover the energy efficiently as the turbine is at its off-design point.
2014 Vol. 32 (9): 742-747 [Abstract] ( 1974 ) [HTML 1KB] [ PDF 1658KB] ( 1216 )
748 Pressure fluctuation and radial thrust characteristics in double volute pumps with single and double outlet
Jiang Yue , Li Hong, Liu Yi
In order to study the internal flow field in double volute pumps with different types of outlet, the three-dimensional, unsteady turbulent flows in a double volute pump with single and double outlet are simulated under various operational conditions by making use of the RNG k-ε turbulence model and sliding mesh technique. The pressure fluctuation and the corresponding frequency spectra at a few monitoring points are obtained as well. It is revealed that the pressure fluctuations in the double volute with single outlet are larger than those in the double volute with double outlet. The blade passing frequency dominates in the pressure fluctuations on the volute tongue and at the outlet under the design and off-design conditions for two volutes. At low flow rates, however, the impeller rotational frequency becomes dominant in the pressure fluctuations on the rib tip and at the volute outlet for the pump with single outlet. Two kinds of double volute can eliminate the radial thrust under different flow rates effectively, but the impeller in the double volute with single outlet is subject to a larger radial thrust because of a significant pressure fluctuation in that volute.
2014 Vol. 32 (9): 748-753 [Abstract] ( 1391 ) [HTML 1KB] [ PDF 1948KB] ( 962 )
754 Analysis of internal flow field in tar residue crushing pump
Xu Wanguo
With extensive application of ammonia/tar separation process-tank in tank in the modern coking industry, its core equipment-tar residue crushing pump needs to be investigated thoroughly. Firstly, the structure and working principle of the crushing pump are introduced, and then the 3D fluid domain model of a crushing pump along with mesh is generated in Pro/E. Secondly, the fluid flow and performance of the pump are predicted by using CFD method, the performance is compared with the experimental data; besides mesh-independence is checked and an optimal mesh size is settled. It is turned out that the predicted performance agrees well the observation, and the design of the pump needs to be modified to meet the head required. Based on the fluid flow fields simulated, there are full of vortices at the entrance of the impeller and inside the casing. The vortices generated in the pump are helpful to crush tar residues; unfortunately they can facilitate to aggravate wear of the through-flow components as well. As a result, the components should be made of excellent wear-resistant materials to extend the pump reliability and life-span. This study has some reference value for the design and manufacture of tar residue crushing pump.
2014 Vol. 32 (9): 754-758 [Abstract] ( 1395 ) [HTML 1KB] [ PDF 1768KB] ( 1007 )
759 Effects of relative setting position between diffuser and volute on flow characteristics of residual heat removal pump
Wang Wenjie, Yuan Shouqi, Pei Ji
In order to investigate the best relative setting position between the diffuser and volute, the three-dimensional, steady turbulent flows in a residual heat removal pump(RHRP)are simulated at five relative positions by using ANSYS CFX14.0. The pressure, velocity and turbulent kinetic energy distributions in the RHRP are achieved and analysed comparatively. The results show that the relative position influences the pump head slightly under design and over-load conditions. Under part-load condition, even though the relative position shows a less effect on the pressure distribution in the impeller, it impacts the flow characteristics in the diffuser and volute obviously. As the relative position is θ=79.56°, there is the widest range of high efficiency for the pump, and there is a uniform pressure gradient in the diffuser and the discharge nozzle of the volute. Besides, the variation of the pressure and velocity gradients is minimal in the volute. The results can provide a reference for selecting the best relative position between diffuser and volute. 
2014 Vol. 32 (9): 759-764 [Abstract] ( 1113 ) [HTML 1KB] [ PDF 4302KB] ( 746 )
765 Numerical simulation of flow in penstock of pumped storage power station based on weakly compressible flow model
Chen Shifan, Zhou Daqing, Chen Yang
The weakly compressible and incompressible fluid flows in the penstock of a pumped storage power station are simulated under the load rejection condition by solving three-dimensional, unsteady and turbulent N-S equations along with an involved time-dependent flow rate subroutine, respectively. A couple of important time-dependent parameters, such as pressure, flow rate in several measurement sections in the penstock, water level in the surge tank, pressure at the penstock outlet as well as flow patterns in the penstock, have been obtained. The predicted transient pressure profiles are compared with the measurements. The pressure given by the weakly compressible fluid model is closer to the experimental data than those obtained by the incompressible fluid model and one-dimensional cha-racteristics method, showing a 0.16% better accuracy and 10.87 m pressure reduction at the penstock outlet. Compared with one-dimensional characteristics method, numerical simulation has more advantages in clarifying flow patterns in a penstock and tracking instantaneous water level in the surge tank. These results may be useful for understanding load rejection condition of hydro-turbine and provide some new ideas for simulating an unsteady flow in pumped storage power stations. 
2014 Vol. 32 (9): 765-770 [Abstract] ( 1298 ) [HTML 1KB] [ PDF 3106KB] ( 877 )
771 Cavitating flow simulations and experiments on Francis turbine model
Wang Lei, Lou Yu, Wang Zhaofu
Based on a two-phase cavitation flow model, both steady and unsteady cavitating flows in a model of 1 000 MW Francis turbine for Baihetan hydropower station are carried out, and the predicted cavitation performance and pressure pulsation are compared with the measured ones. In steady cavita-ting flow simulations, the total pressure of stream in the draft tube is lowered step by step, causing a steadily reduced cavitation coefficient available so as to mimic cavitation progress in an experiment on the model. The features of cavitation development, cavity locations and evaluation of cavitating vortex rope in the draft tube have been predicted well by means of pressure distribution, velocity vector and vapour volume fraction. Additionally, unsteady cavitating flow simulations can predict temporal variations of the cavities and vortex rope as well as the frequencies of pressure fluctuation precisely; consequently, the vibration frequency and amplitude estimated are consistent with the experimental data. It is shown that vortex rope in the draft tube can affect the pressure pulsation and instability of the turbine more significantly with the development of cavitation. In other words, the pressure pulsation is more sensitive to cavitation, i.e. the more serve cavitation, the more violent pressure pulsation, and cavitation intensifies the hydraulic turbine instability.
2014 Vol. 32 (9): 771-775 [Abstract] ( 1562 ) [HTML 1KB] [ PDF 6591KB] ( 1101 )
776 Application of CFD technology in air-assisted spraying in orchard and analysis of its prospects
Zhou Liangfu, Xue Xinyu, Jia Weidong, Ding Suming, Sun Zhu
With the rapid development of numerical computational theory and computer technology, CFD technology has been extensively used in agricultural engineering to vividly visualize flows. This review mainly focused on applications of CFD technology in structure optimization(number of blades, backflow structure, stress in blade, blade angle and duct configuration)and performance prediction(efficiency and noise)of fans in air-assisted sprayer as well as validation of standard k-ε turbulence model. Additionally, the feasibility of Lagrangian method for handling interaction between air and disperse phase is verified by applying CFD technology to identify microscopic characteristics of spray. Unfortunately, CFD technology cannot provide any information about atomization mechanism of spray pre-sently. The standard k-ε turbulence model has been applied and verified in internal flow and droplet deposition on canopy. However, the effects of canopy on turbulent kinetic energy dissipation are not explored in detail, and there is lack of study on droplet deposition model. Finally, a few prospects for structure optimization and performance prediction of fans, atomization mechanism and effects of canopy on spraying flow are highlighted. Furthermore, it is proposed that how to determine the spray capacity and velocity which can match a specific canopy should be the hotpot problem in future.
2014 Vol. 32 (9): 776-782 [Abstract] ( 1607 ) [HTML 1KB] [ PDF 1402KB] ( 1189 )
783 Investigation into unsteady flow around tandem cascade of Francis turbine by employing immersed boundary method with feedback force
Wang Wenquan, Su Shiqi, Zhang Lixiang
The immersed boundary method(IBM)is one of important numerical methods for solving the interaction between flexible structure with large deformation or rigid structure and viscous fluid. The advantages of IBM are high computational efficiency, suitable for complicated shape and simple grid structure which means a conformal mesh can be avoided and an adaptive mesh technique can be implemented easily. The original IBM is suitable for the flexible body and was updated with feedback force by Lai and Peskin to approximately deal with a rigid boundary problem. In this paper the unsteady flow around a tandem cascade of Francis turbine is simulated by this updated method. Particularly, the cartesian adaptive mesh refinement and finite difference method are applied in the whole flow field. The unsteady characteristics of the flow field, the non-uniformity indexes for pressure, velocity and vorticity in the guide vane wake are attained. These results are helpful to study on the effects of uneven flow field on fluid-induced blade vibration in a hydro-turbine in future.
2014 Vol. 32 (9): 783-787 [Abstract] ( 1483 ) [HTML 1KB] [ PDF 1639KB] ( 836 )
788 Analysis of optimum drop size distribution of greenhouse air-assisted mist sprayer by using response surface method and genetic algorithm
Zhong Liping,, Qi Lijun,, Ji Ronghua, Yuan Xue, Mei Yincheng, Gao Chunhua
In order to clarify the influences of operational parameters on drop size distribution issued by a greenhouse air-assisted mist sprayer, a series of spraying experiments are conducted, then two response surface models about the drop size distribution coefficient are correlated to the operational parameters by using quadratic polynomial regression and BP neural network method to obtain the optimum operational parameters combination. It is shown that the correlation coefficient and root-mean-square error are 0.987 1 and 0.134 0 respectively for the BP neural network model, compared with 0.928 2 and 0.215 9 for the response surface model established by the quadratic polynomial regression, suggesting the former is the best model. According to the quadratic polynomial response surface model, the minimum drop size distribution coefficient is as high as 1.47%, compared with 1.58% experimental measurement. Based on the BP neural network model, however, the minimum drop size distribution coefficient predicted by genetic algorithm is just 1.21% against 1.28% experimental observation. Ob-viously, the BP neural network method combined with genetic algorithm exhibits a better accuracy than the response surface method in the operational parameters optimization of air-assisted mist sprayer.
2014 Vol. 32 (9): 788-794 [Abstract] ( 1490 ) [HTML 1KB] [ PDF 1777KB] ( 1055 )
795 Three-dimensional growth modelling and realization for potted tomato root system
Ji Ronghua, Li Xiang, Qi Lijun,, Wang Jianqin
In order to explore the distribution characteristics of potted tomato root system under negative pressure underground irrigation, the three-dimensional spatial coordinates and growth parameters of tomato roots are measured at different growth stages. After analyzed the experimental data, the root growth function, lateral point distribution, lateral root birth probability and orientation are clarified. The differen-tial L-system is proposed to describe the tomato root growth model and boundary conditions based on the root topological pattern and actual growth situation. OpenGL technique is used to realize the three-dimensional visualization simulation system for potted tomato root growth, consequently, the root spatial distribution and growth state can be reconstructed intuitively under negative pressure underground irrigation. It is shown that the averaged fitness of root tip position distribution is about 83% in seedling stage but is approximate 91% in fruiting stage compared with experimental data. Hence the growth model generated can effectively simulate the growth of potted tomato root system. The differential L-system based model can exhibit the morphological characteristics and growth characteristics of potted tomato root system at different growth stages precisely. The results may form a base for forthcoming study on interaction between soil moisture and root system growth.
2014 Vol. 32 (9): 795-801 [Abstract] ( 2355 ) [HTML 1KB] [ PDF 1594KB] ( 1485 )
802 Influences of saline water irrigation on soil physical properties in Shiyang River Basin
Ji Quanyi, Feng Shaoyuan,, Yuan Chengfu, Huo Zailin, Qi Yanbing
To reveal the regulation mechanism of saline water irrigation on soil hydraulic properties and to exploit proper irrigation schedules in arid areas in Northwest China, a series of field experiments are conducted in the middle area of Shiyang River Basin by using irrigation water with four salinity levels(0.71, 3.00, 6.00 and 9.00 g/L), the effects of salt content on soil bulk density, porosity, texture, and saturated hydraulic conductivity are identified. The results indicate that the soil bulk density increases significantly but the soil porosity decreases with increasing irrigation water salinity, thus the saturated hydraulic conductivity is changed against irrigation water salinity as well. Additionally, the soil clay content increases notably under the condition of saline water irrigation. These findings provide a new insight into understanding of the response of soil hydraulic properties to saline water irrigation.
2014 Vol. 32 (9): 802-807 [Abstract] ( 1226 ) [HTML 1KB] [ PDF 1601KB] ( 934 )
808 Determining weights of comprehensive evaluation indexes for irrigation district operation performance by method of game theory
Fei Liangjun, Wang Guangshe, Sun Jie ,, Feng Chanli, Xie Fang
In order to decide if the weight of an index for comprehensive evaluating operation perfor-mance of irrigation district is reasonable and to consider whether the outcomes of an evaluation are rational and scientific, we apply subjective analytic hierarchy process and objective variation coefficient method into determination of a series of weight based on game theory in this paper. Then we integrate these individual weights into final weights. Further, based on the driving force-state-response model, we build a comprehensive evaluation system to assess the operational performance of a large irrigation district. At last, we evaluate the operational condition of Jinghui Canal Irrigation District in Shaanxi by means of this system. The results show that the decided comprehensive weights can involve decision-makers′ subjective requirements but also can represent the actual operational circumstance of an irrigation district. Besides, the evaluating process is simple, scientific, objective, and universal, so it can provide a proper evaluation for the operational situation of an irrigation district.
2014 Vol. 32 (9): 808-813 [Abstract] ( 1165 ) [HTML 1KB] [ PDF 1508KB] ( 1025 )
814 Vegetation diversity and soil biological characteristics under different restoration patterns in abandoned salinity farmland in arid areas
Li Bing, Liang Jing, Zhang Fenghua, Liu Guangming
The effects of restoration pattern on vegetation diversity and soil biological characteristics in salinity abandoned farmland are studied in the experimental field on the alluvial fan oasis of Manas Ri-ver Basin. The restoration pattern includes water supplement, grass artificial cultivation and replanting. The results indicate that the recovery measures applied do significantly increase the vegetation diversity, soil microorganism quantity and soil enzyme activity in the field. Compared with the original abandoned farmland, the vegetation diversity is increased by 25.13% and 9.84%, the electrical conductivity is decreased by 49.15% and 33.55%, the organic mass is raised by 99.10% and 88.34%, and the alkali-hydrolysed nitrogen is 70.10% and 36.57% higher in the field treated by water supplement, grass artificial cultivation, respectively. At the same time, urease, catalase, invertase and phosphatase activity are increased by 65.18%, 47.21%, 93.23% and 116.03%, respectively, under the treatment of grass artificial cultivation. The soil microorganism quantity is minimal in the abandoned farmland, but is the highest in the field recovered with grass artificial cultivation, and is in between in the field treated by replanting method. It is shown that there exists a positive correlation between soil microbial biomass carbon and number of soil microorganisms, and there is a significantly positive correlation to phyto community α-diversity. Obviously, grass artificial cultivation or water supplement can enhance vegetation diversity and improve soil enzyme activity in abandoned farmland in arid areas, subsequently, substantially reduce salt content in the soil and promote soil nutrient accumulation.
2014 Vol. 32 (9): 814-821 [Abstract] ( 1212 ) [HTML 1KB] [ PDF 1688KB] ( 1017 )
822 Effects of irrigation schedule on water consumption and yield of seed maize
Dong Pingguo, Wang Zengli, Wen Guanggui, Fan Xiaokang
The effects of irrigation frequency on soil moisture, water consumption and water use efficiency(WUE)in growth stage, maize seed yield are studied for seed maize by field experiment under 900 m3/hm2 constant irrigation quota and four irrigation frequencies: 0, 2, 3, 4, respectively. It is showed that irrigation frequency mainly affects the soil moisture in 0-100 cm layer after jointing stage, the number of rows per ear and the number of kernels per row. The highest water consumption mainly appears in tasseling and grain fill stages. Seed maize demonstrates a variably sensitive degree to water shortage during its various growth stages, i.e. the degree decreases steadily in a sequence such as fill, jointing, seedling, milk and tasseling stages. An irrigation schedule, such as 900 m3/hm2 irrigation quota for 3 times in seeding and jointing stages, jointing and tasseling stages, tasseling and filling stages, respectively, exhibits a higher economic yield and a better WUE in arid and semi-arid areas in Northwest China.
2014 Vol. 32 (9): 822-828 [Abstract] ( 1436 ) [HTML 1KB] [ PDF 1623KB] ( 1132 )
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