Journal of Drainage and Irrigation Machinery Engin

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排灌机械工程学报

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Journal of Drainage and Irrigation Machinery Engin

	2012 Vol.30 Issue.6 Published 2012-11-30

	article

Article

	621	Adaptive mesh refinement technique for seepage flow field in groundwater source heat pump system
		WANG Xiao-Hong, SHI An-Feng, ZHENG Xiao-Lei, JIA Jiang-Tao
		A fast and highly efficient numerical computational method has important practical significance for development and application of the technology in groundwater source heat pumps. Normally the boundary of an aquifer has an irregularshape. Compared with unstructured grids, adopting structured grids can effectively decrease the complexity in discretization of the mathematical equations and is very beneficial for developing an adaptive mesh refinement (AMR) algorithm to simulate the seepage flow field of groundwater source heat pump system. To develop a computational method based on the structured grids, a simple pretreatment method was proposed to deal with the grid cells on the aquifer boundary. In the method, the effective permeability on the interfaces between grid cells rather than those of the grid cells was involved in computations, further an algorithm for calculating the effective permeability on the six faces of a grid cell was proposed. The threedimensional computational examples show that even more coarse cells are adopted a more accurate result can be reached for a domain with irregular boundary. In the AMR algorithm the cell sizes depend on the temperature gradient, i.e. the smaller cell size the lower the gradient; as a result of this, the time consuming for simulating the underground seepage flow in a groundwater source heat pump system is reduced considerably but the accuracy remains the same.
		2012 Vol. 30 (6): 621-626 [Abstract] ( 2015 ) [HTML 1KB] [ PDF 2150KB] ( 1699 )

	627	Influence of interstage seal clearance on performance of newtype well pump
		SHI Wei-Dong, WANG Chuan, SI Qiao-Rui, XU Jing, LU Wei-Gang
		In order to explore influence of interstage seal clearance on the performance and flow field of multistage well pumps, a newtype well pump QS-40-30-55 was taken as the investigation model; the whole flow field in the pump with different seal clearances were stimulated with Fluent. Effects of the clearance on the overall performance and internal fluid flow field in the pump were analyzed. The results showed that the head and efficiency of the pumps are reduced, while the shaftpower remains unchanged with increasing clearance at the same flow rate. A stream of liquid in the guide vane exit flows back into the impeller hub along the interstage seal clearance and then it moves into the guide vane through the side chamber between the impeller and the guide vane, causing a disturbance in the flow at the guide vane exit and the entrance to the next stage impeller, which increases the hydraulic losses and degrade the pump performance. The experimental results of the prototype of the pump show the best efficiency point occurs at a lower flow rate than the specified one, but it is still in accord with the National Pump Test Standard of China. Because the impeller disc friction loss and the leakage loss through the interstage seal clearance have been involved in the computational model, the estimated performance by CFD is in very good agreement with experiments (error is less than 1％), confirming the validity of CFD numerical simulation approach. Those results might be instructive for optimal design of newtype well pumps, especially whose impellers are designed by means of the impeller diameter maximization method.
		2012 Vol. 30 (6): 627-631 [Abstract] ( 2382 ) [HTML 1KB] [ PDF 1485KB] ( 1632 )

	632	Threedimensional inverse design and fluid flow numerical simulation for centrifugal impeller
		YANG Wei-1, WANG Fu-Jun-1, WANG Hong-2
		In order to solve the problems of traditional design methods, which are mainly rely on experience of a designer and the design cycle is often too long, a threedimensional (3D) inverse design method was used to design the impeller according to given flow field conditions. The method has a better control ability of design outcomes during the design procedure. Based on the inviscid and potential flow assumption, a 3D velocity field in centrifugal impeller is decomposed into an averaged circumferential flow and a periodic one; subsequently they are solved numerically in the twodimensional meridional plane and the bladetoblade surface to approximately obtain the 3D fluid flow field. 3D geometry of a blade is established according to the slip boundary condition on the surface of the blade, the flow field in the designed impeller is obtainable simultaneously as well. A centrifugal impeller was designed by a 3D inverse design code developed by the authors, also a 3D steady, turbulent fluid flow in the impeller was simulated by using a CFD code to examine the flow field and evaluate the impeller performance. The viscous fluid flow simulated and inviscid one obtained in the design are in qualitative agreement, confirming the validity of the 3D inverse design method. The results indicate that combination of the inverse design method and the turbulent flow simulation technique can shorten design cycle and improve design quality effectively. This design strategy may be applicable to impeller design of the rest type of fluid machine.
		2012 Vol. 30 (6): 632-635 [Abstract] ( 2415 ) [HTML 1KB] [ PDF 1302KB] ( 2114 )

	636	Radial forces of waterjet propulsion mixedflow pump
		CHENG Li, Bart P.M. van Esch, LIU Chao, ZHOU Ji-Ren, JIN Yan
		Fluctuations of fluid pressure in hydraulic machinery can cause resonance and fatigue damage of blades. In order to study fluidinduced forces, which are caused by impellerdiffuser interaction, unsteady radial forces due such an effect was conducted in a mixedflow pump with a vaned diffuser by using CFD computation and model experiment. A closedloop test rig was built for the pump and a corotating dynamometer was installed between the impeller and the pump shaft to measure the instantaneous forces and moments on the impeller. The dynamic behavior of the experimental rotorshaft system was determined by carrying out extensive calibrations. The measured forces at the blade passing frequency showed an unexpected dependency on flow rate. Another important observation was that the blade excitation forces cause the impeller to whirl in the direction opposite to shaft rotation. The computed global characteristics and the magnitude of blade interaction forces showed good agreement with measurements, respectively. The measured results were compared with the unsteady ones estimated by using CFD codeFluent. Over a large range of flow rates, the trend of force variation agrees well with the measurements. The reasons for deviation of prediction from experiment were explained.
		2012 Vol. 30 (6): 636-640 [Abstract] ( 2222 ) [HTML 1KB] [ PDF 2112KB] ( 1583 )

	641	improving gas and liquid phases mixing in impeller with high gas void fraction
		ZHANG Jin-Ya, ZHU Hong-Wu, XU Bing-Gui, DING Kuang, QIANG Rui
		To solve the problems, such as gasliquid separation in the impeller of a rotodynamic multiphase pump under high gas void fractions (GVF) and subsequent reduction in the pump performance, several methods for breaking gas packets to inhibit gasliquid separation and enhance the mixing between two phases were presented, including implanting short blades, using Tshaped blades, and opening holes on the blades where gas packets appear. Then, under the rated condition, the flow fields in three amended impellers were simulated under the GVFs of 60％ and 80％, respectively, by means of CFD codeFluent. The results show that the streamlines are more evenly distributed in all the amended impellers than those in the original one, the degree of mixing of two phases is improved greatly. Additionally, the local highest GVF in all the amended impellers is not only lower than that in the original impeller, but the GVF distribution in them is more uniform. Besides, a comparison of total pressure head rise across the original impeller and the amended ones was made. It was showed that the total pressure rise of the amended impellers is similar to the original one under low GVFs, but it is larger in high GVFs. The amended impeller with opening holes exhibits the highest head rise, which is even better than that of the original impeller, suggesting the means of opening holes not only enhances the ability of mixing of twophase but also prevent extra hydraulic losses furthest.
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		2012 Vol. 30 (6): 641-645 [Abstract] ( 2213 ) [HTML 1KB] [ PDF 1958KB] ( 1775 )

	646	Effects of some factors on hydraulic performance of mixedflow pump with guide vanes
		CHANG Shu-Ping, Wang-Yong-Sheng, Su-Yong-Sheng
		In order to improve hydraulic performance of a mixedflow pump with guide vanes, effects of several factors such as tip clearance, number of blades, blade angle and blade thickness on the performance were explored numerically. The SST turbulence model and SIMPLEC algorithm in the Ansys CFX 120 software were used to simulate the internal flow fields of the pump by means of multiblock structured meshes. The results showed that the head, shaftpower and efficiency are declined with increasing tip clearance. The head and power show gradually less increase with increasing number of blades and too many blades or too few blades are all unfavorable to pump efficiency. The changes in both head and power caused from a variable blade stagger angle become dominated with increased flow rate, suggesting the best efficiency point location and the shape of the efficiency curve are adjustable by altering the angle. The best efficiency point is moved to a high flow rate and the slightly increased peak efficiency is observed with decreasing maximum blade thickness. Under the premise of meeting manufacturing process and installation requirements, those factors optimally chosen can improve hydraulic performance of a mixedflow pump with guide vanes.
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		2012 Vol. 30 (6): 646-649 [Abstract] ( 1899 ) [HTML 1KB] [ PDF 1855KB] ( 1785 )

	650	Experimental study on performance of liquid jet gas pump by utilizing wallattached fluidic oscillator
		XIANG Qing-Jiang, YUN Qiang-Long, LI Hong, WU Yan-Lan
		A new kind of jet, which is a wallattached oscillating jet produced by a fluidic element, was put forward and is going to be used in a liquid jet gas pump (LJGP). The liquid jet gas pump was vertically installed on a testrig, and then the performance of twentyfour test models with various dimensions was measured and compared with that of the pump with an ordinary straight jet. The results showed that the driving pressure has a significant influence on the performance, but the performance curves exhibit a similar peak pressure ratio h, the maximum flow ratio q and the pump best efficiency η increase with increasing driving pressure. At the same working pressure, the performance curves get more flat as the area ratio of throat to nozzle m is increased, namely, the peak h decreases and the maximum q increases, and the efficiency η gets a maximum at some value of m. This indicates that there is an optimum area ratio m at which the pump has the best efficiency. The best efficiency of a gas pump with an oscillating liquid jet was about 16%, less than that with a normal straight jet, but the two pumps have an approximate gas flow rate suctioned. Note that an oscillating jet needs a larger area ratio m, moreover as the oscillating frequency is increased, the pressure ratio h is improved but still less than the straight jet. At the given working pressure of 300 kPa, an empirical equation for the unsteady performance curve of a LJGP was proposed by best fitting experimental data. The equation might be used to guide the practical application for such a pump.
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		2012 Vol. 30 (6): 650-654 [Abstract] ( 2208 ) [HTML 1KB] [ PDF 1214KB] ( 1986 )

	655	Analysis of flow in liquid jet pump—Part Ⅰ:Experiment and threedimension numerical simulation
		WANG Song-Lin, WANG Yu-Chuan, GUI Shao-Bo, GAO Chuan-Chang, CAO Shu-Liang
		The performance of a horizontally installed liquid jet pump with side suction was tested and its internal flow was analyzed by numerical simulation. The standard k-ε twoequation turbulence model and SIMPLE method were adopted in the numerical simulations. The simulated performance parameters agreed well with experimental ones at the best efficiency point. Twofluid mixing process and its flow pattern in the pump were analyzed as well based on the numerical simulation results. At a large flow ratio (q>0.8), a reduced local pressure ratio and the suctioned liquid with loss of energy are observed in the region from throat inlet to 0.6 times the throat diameter down stream due to mixing and local frictional losses. As the flow ratio increases, the energy obtained by the suction fluid is decreased, thus the distance where an energy transfer takes place between two fluids increases; the two fluids velocity becomes uniform once the suctioned liquid travels in the nozzle for a distance as long as 6-8 times the throat diameter. However, the peak pressure occurs in less than that distance. Such a two liquid mixing process in the throat is similar to that of fully developed turbulent flow. For the side suction jet pump, there are vortexes in the crosssection induced by a secondary flow due to asymmetric flow in the suction chamber, but the velocity of the secondary flow is so smaller than the mainstream velocity in the throat that the major characteristics of the jet pump can be obtained by a two dimensional theoretical analysis.
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		2012 Vol. 30 (6): 655-659 [Abstract] ( 2948 ) [HTML 1KB] [ PDF 2047KB] ( 1815 )

	660	Influence of positive preswirl generated by different airfoils on performance of centrifugal pump
		WANG Hai-Min, Zhou-Cai-Min, Huang-Xiong, Lin-Hao
		Two sets of inlet guide vanes with different airfoil sections were designed for the preswirl regulation in a centrifugal pump by using the basic design theory of turbomachinery to optimize its operation conditions.Subsequently, effects of positive preswirl induced by the guide vanes with different airfoils on the hydrodynamic performance of the centrifugal pump were studied. The result showed that an appropriately designed positive preswirl could increase the efficiency of the singlesuction centrifugal pump.Compared with the performance without the inlet guide vanes, the efficiency of the centrifugal pump installed the inlet guide vanes with straight constantthickness could be increased as high as 2.05% and the responding shaftpower consumption could be reduced as low as 6.35%. For the guide vanes with Gottingen364 airfoils, the efficiency of the pump was increased by 2.34% and the reduction in shaftpower consumption was lowered by 6.53%.The inlet guide vanes with both straight constantthickness blade and Gottingen airfoil showed little influence on the head. For the straight constantthickness blade, the best efficiency point was moved to a low flow rate 172 m3/h at the 20° and 40° preswirl angles; for the Gottingen airfoil, the best efficiency point was changed to 172 m3/h as well; however, the best efficiency occurred at 190 m3/h at the 40° preswirl angle.Clearly, the high efficiency range has been extended at the 20° and 40° preswirl angles for the inlet guide vanes with Gottingen airfoil.
		2012 Vol. 30 (6): 660-664 [Abstract] ( 2164 ) [HTML 1KB] [ PDF 2171KB] ( 1932 )

	665	3D PIV measurement of flow in doublechannel pump under overall operating conditions
		WU Xian-Fang, LIU Hou-Lin, WANG Kai, TAN Ming-Gao, YANG Dong-Sheng
		The inner flow characteristics in a doublechannel pump were measured under eight flow rates with a particle image velocimetry (PIV). To guarantee the accuracy of three dimensional PIV measurements, a few key techniques, such as the optical fiberbased external trigger synchronization system and three dimensional equivalent calibration methods, were applied in the measurements. A Visual C++2005 code was composed to obtain the relative velocity components from the absolute ones measured according to the velocity triangle. The results showed that one large scale doesnt appear in a flow passage of the impeller until the flow rate as low as 04 time the design flow rate Qd.. Moreover, this vortex gets more evident with decreasing flow rate. As flow rate decreases, the absolute velocity in the volute diffuser is decreased as well. A vortex doesnt occur there until the flow rate is reduced to 02Qd. The absolute velocity gets maximum values at the flow rate of 02Qd. There exist dominated largescale vortices in the impeller and volute at the shutoff condition, suggesting the poorest flow condition has emerged there.
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		2012 Vol. 30 (6): 665-669 [Abstract] ( 1797 ) [HTML 1KB] [ PDF 3292KB] ( 1859 )

	670	Computation of spatial submerged hydraulic jump with different abrupt expansion ratios
		ZHENG Tie-Gang, DAI Hui-Chao, DING Quan-Lin
		Since the abrupt expansion can enlarge turbulence intensity level in a local range of water flow, it can be utilized as kind of important energy dissipaters. In order to study effects of abrupt expansion ratio on hydraulic characteristics of down stream flow, spatial submerged hydraulic jumps with the abrupt expansion ratios of 1.000, 0.833, 0.667, 0.500, 0.333 are simulated numerically based on a nonuniform structured mesh, the RNG k-ε turbulence model and the pressure and velocity coupling algorithmPISO. It was found that the change of abrupt expansion ratio has obvious influence on down stream velocity, turbulence kinetic energy and energy dissipation rate. The smaller the ratio, the more obvious the change in velocity, the faster the primary flow diffuses, and the more clearly the flow pattern transition develops. With decreasing expansion ratio, the smaller the turbulent stresses, the larger the energy dissipation rate. Compared with a typical hydraulic jump, the spatial submerged hydraulic jump possesses greatly improved energy dissipation rate. However, once the ratio is less than 0.5, the dissipation rate on longer is improved obviously yet.
		2012 Vol. 30 (6): 670-676 [Abstract] ( 2298 ) [HTML 1KB] [ PDF 1986KB] ( 2131 )

	677	Efficiency scaling method for pumps and their systems
		LU Wei-Gang, YAN Deng-Feng, ZHEN Feng
		The theoretical bases of existing efficiency scaling formulas and several scaling methods recommended in some industrial standards for pumps were analyzed. It was found that those formulas are incompletely mathematical expression, experiencedominated and less universal, etc. The hydraulic loss ratios and efficiency at the best efficiency point computed with different efficiency scaling formulas were compared, and it was identified that the efficiency of the prototypes scaled from the models by using Medici's and Fromm's and Moody's formulas shows quite difference compared with the measurements. The efficiency of the prototypes estimated by the rest formulas is less difference from the tests, in which Ackeret's formula gives a minimum error. A flow regimedepended efficiency scaling method for pump and its system was put forward, in which three formulas of skin friction factor for three flow regimes were introduced according to essentials of fluid mechanics, and then the corresponding mathematically simplified formulas were proposed for they to be applied conveniently. Based on the internal flow characteristics in pumps, the basis for determining the skin friction factor was analyzed and argued, and influences of the proportional constants of pump performance parameters and skin friction factor on the efficiency scaling were studied; eventually an additional method for estimating the efficiency coefficient was resulted. For the same prototype and model of pump and its system, the efficiencies scaled with those different methods were predicted; the reasons for difference in efficiency estimated and feasibility of the methods were analyzed. The results indicate that the proportional constants have less influence on the flow regimedepended efficiency scaling method compared with Ackeret's and Hutton's formulas. Thus, as the flow regimedepended efficiency scaling method is applied, the efficiency scaled with a skin friction factor in any flow regimes doesn't seem to show significant difference.
		2012 Vol. 30 (6): 677-682 [Abstract] ( 2766 ) [HTML 1KB] [ PDF 1318KB] ( 2412 )

	683	Quantitatively optimal selection on regulation mode of pump unit in large pumping stations
		FENG Xiao-Li, CHOU Bao-Yun, YANG Xing-Li, DONG Bo
		In order to reasonably select a regulation mode of pump units and therefore to realize the optimal operation, a technical analysis was conducted under the consideration of the following factors as regulating system components, transient characteristics during startup and shut down, installation and maintenance, reliability and applicability, and so on. Then, a method for quantitatively selecting the regulation mode of pump units was put forward, in which the total cost on equipment investment and pump units operation was minimized to allow the units to be operated optimally in a large pumping station. Nevertheless, head variation, operating time, variable operating conditions, equipment investments and operation cost were taken into account comprehensively in the method. For typical types of pump, their regulation model was optimized by using the method. The results indicate that it is necessary to install a blade angle adjusting device or pump rotational speed regulating instrumentfrequency converter when either the operating head is much more deviated from the high efficiency zone of a pump unit or there is a larger variation in the head. Additionally, the head annual variation profile also has a certain influence on selection of the regulation mode. After the cost on instruments is reduced, the economical benefit caused from a realized optimal operation by means of either the blade angle adjusting device or rotational speed regulating instrument is even more considerable since the head can be varied in a significantly wide range. The method provides evident for quantitatively determining regulation mode of pump units.
		2012 Vol. 30 (6): 683-689 [Abstract] ( 1808 ) [HTML 1KB] [ PDF 1658KB] ( 1981 )

	690	Effects of support structure on lubricating properties of bidirectional thrust bearings
		HUANG Bin, WU Jun-Ling, WU Zhong-De, JIAO Lei, Wang-Le-Qin
		A threedimensional thermoelastichydrodynamic mathematical model of thrust bearing was set up and the boundary conditions was adopted for analysis of the effects of support structure on hydrodynamic lubrication performance of bidirectional thrust bearing in pumpturbine. The finite difference method was employed to solve the THD model, and the thermalelastic deformations in the pad were obtained by the finite element software ANSYS11.0. The data transfer between the THD model and ANSYS11.0 was carried out automatically by an interface program. The calculation model set up in this paper was then applied to a calculating example. The oil film thickness distribution, oil film pressure distribution and pad temperature distribution were obtained. Good agreement between the theoretical calculating results and experimental test was obtained. On this basis, the static performance distribution and thermoelastic deformation distribution on the pad surface of three different support disks were analyzed. The results show that improving lubricant performance can be obtained if the support structure is chosen correctly, and the thermoelastic deformation distribution on the pad surface of cutting away disk or doubledisk supported thrust bearing are better than the singledisk one, which leads to prior lubricant performance.
		2012 Vol. 30 (6): 690-694 [Abstract] ( 1977 ) [HTML 1KB] [ PDF 2941KB] ( 2148 )

	695	Transient simulation of turbine jointed with diversion penstock
		FAN Hong-Gang, Huang-Wei-De, Chen-Nai-Xiang
		With consideration of the influence of transient flow in pipe during a transition of operation condition, a coupled calculation model for the transient flow in a pipe and threedimensional unsteady flow in a turbine was developed in this paper. The transient flow in pipe was calculated by the characteristic method and the unsteady flow in the turbine was calculated by the finite volume method for threedimension incompressible flows. A coupled iteration was carried on at the interface between the pipe and the turbine based on the continuity of flow and the balance of total pressure of water. Three methods, including coupled calculation method, traditional transient simulation method and traditional threedimensional flow calculation method, were used to simulate the loadrejection transient process of a hydraulic turbine with diversion penstock. The results showed that the trends of pressure, flow of unit and rotational speed, etc, are consistent in all three methods. However, because the reflection and superposition of water hammer wave is considered in the coupled calculation method, the increase in water hammer pressure at the spiral inlet is higher and the pressure fluctuation in the turbine is stronger, suggesting the method can reflect the interaction between transient flow in the pipe and threedimension unsteady flow in the turbine more realistically.
		2012 Vol. 30 (6): 695-699 [Abstract] ( 1873 ) [HTML 1KB] [ PDF 1974KB] ( 2032 )

	700	Simulation and analysis of inhomogeneous flow field in pulsed electrofloatation
		DENG Xiao-Gang, ZHOU Xiong
		Due to the largescale violent circumfluence in the traditional electrofloatation (TEF), there is interference to grown and floatation of the mixture of microbubbles and floccules, causing lower energy utilization efficiency. In this paper, a pulsed electrofloatation (PEF) method was proposed by using a square wave impulse direct current. Since the circumfluence in the inhomogeneous field generated by PEF is weaker than that by TEF, the energy utilization efficiency will be improved. Then the liquidbubble flow field of PEF was simulated by using Fluent of Ansys 13.0. The results showed that the inhomogeneous flow field in PEF has a more reasonable turbulence energy distribution and less violent circumfluence induced by microbubbles floating. This suggests that PEF is helpful to the formation and floatation of the bubblefloccules mixture. With the same electric current density, the power consumption of PEF is as low as 1/4－1/3 that of TEF, but a similar floatation effect has been reached compared with TEF, so the power consumption efficiency is much better.
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		2012 Vol. 30 (6): 700-704 [Abstract] ( 1726 ) [HTML 1KB] [ PDF 3622KB] ( 1790 )

	705	saving in cooling water circulation system and its implement
		TANG Yue, MA Zheng-Jun, DAI Sheng, ZHANG Xin-Peng, HUANG Zhi-Pan
		The cooling water circulation system is frequently subject to a low efficiency and a high energy consumption caused from improper pump selection, unreasonable regulation of working condition, unscientific management of operation and difficulty in energy consumption evaluation. In order to reduce the energy consumption, the water circulation system in a chemical plant was used as an investigation model, then the situation of equipment installation and pump operation conditions during normal production period were surveyed. Comparing the existing energy consumption with that under a variable frequency speed regulation, the space for energy saving was identified; eventually, the analysis of assessment of energy consumption of the whole system was completed. An energysaving water supply strategy, where a variable frequency speed regulation was utilized in the pump stations of the cooling water recirculation system, was established according to the pump affinity laws and by considering the energysaving in the pumps themselves and their systems. Under the premise of meeting the chemical production process requirements, a constant pressure water supply was realized in the water recirculation pipe network. Moreover, a survey method for evaluating the energy consumption in a cooling water recirculation system was suggested based on pump performance curve, motor torquespeed curve and operation parameters in the key operation conditions of the system. After the cooling water circulation system was refurbished in that chemical plant, the annual electric power consumption in the plant was reduced to 1.4×105 kW·h from 2.1×105 kW·h, the saved power is around 7×104 kW·h, causing the power consumption was reduced by up to 33%.
		2012 Vol. 30 (6): 705-709 [Abstract] ( 2125 ) [HTML 1KB] [ PDF 1308KB] ( 2006 )

	710	Numerical simulation of opening process of shuttle check valve
		LI Liang-Chao, ZENG Xiang-Wei, XIANG Ke-Feng, XU Bin, SONG Dan-Lu
		The flow field in a shuttle check valve was numerically simulated by using the CFD method to examine whether the valve is subjected to cavitating flow during its opening process. A user defined subroutine and a dynamic mesh technique were used to involve the pool motion. The results show that the fluid flows mainly along the valve wall and backflow formed in the center of the valve during its opening process. And there have vortices existing in the shuttle valve. Cavity onsets easily in the center of the vortex as the pressure there is the lowest. The inception and development of cavitation in the valve are closely related to the inlet and outlet pressure and valve opening degree. Furthermore, cavitation can cause flow instabilities. It is demonstrated that under a certain pressure difference, the valve spool is opened to the maximum degree initially and then gradually rebound to a stable position with fluctuating steps.
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		2012 Vol. 30 (6): 710-714 [Abstract] ( 2795 ) [HTML 1KB] [ PDF 3291KB] ( 1817 )

	715	Twostep throttle properties of hydraulic valve ports
		YUAN Shi-Hao, YIN Chen-Bo, LIU Shi-Hao
		The geometrical features of the U and V ports as well as their combinations (U-U, U-V and V-V) were analyzed, and then the throttle areas of those ports were calculated in a simplified manner so as to investigate two-step throttle properties of hydraulic valve ports. The ratio of throttling areas in terms of valve opening was obtained, and it was observed that the location of the minimum throttle area of U port varies; however, this is not true for V port. The cavitation functions of U and V ports against opening were obtained and the cavitation curves also were plotted by using cavitation number σ. According to the cavitation functions, it was observed that the severe cavitation zone in U port varies with opening, but that in V port is fixed. When the inlet and outlet of throttling port are reversed, there is an obvious change in cavitation number at the same opening. The stiffness analytical formulas for U and V orifices were derived and the stiffness curves were calculated under various pressure differentials across a port and openings. For a lower pressure differential and a smaller opening, a stiffer stiffness can be achieved.
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		2012 Vol. 30 (6): 715-720 [Abstract] ( 2442 ) [HTML 1KB] [ PDF 1587KB] ( 2261 )

	721	Surface reconstruction technique for kaplan turbine blades
		LAI Xi-De, LI Guang-Fu, ZHANG Wei-Bin, WANG Li-Fa
		Some surface reconstruction related issues as Scattered point cloud data acquisition, data pretreatment, triangulation, NURBSbased surface reconstruction Methods, inspection of fairness and accuracy ,ect,were discussed in detail.Then the process of surface reconstructing freeform surfaces of mechanical parts such as tubomachine blades was presented. For solving the problem of surface reconstruction of kaplan turbine blade contours based on scattered data, the basic theory of surface reconstruction was reviewed and a blade surface was divided into various regional blocks based on its feature in shape; then a method for constructing a surface patch in a rectangular domain whose four boundaries were two streamlines and two interaction curves between a blade and a meridian plane was proposed. As a result of those, a 3D model of blade that meets design requirements was yielded. The efforts show that the digital geomety model constructed by this method has good smoothness and accuracy. It proposed a foundation for the subsequent work and provides an objective basis for reverse engineering applied in fluid machinery industry.
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		2012 Vol. 30 (6): 721-725 [Abstract] ( 2182 ) [HTML 1KB] [ PDF 1853KB] ( 2060 )

	726	Hydraulics problems in farmland irrigation
		WU Pu-Te, ZHU De-Lan, Lv Hong-Xing , ZHANG Lin
		Based on the practice in research and development of technology and product design in watersaving irrigation engineering for years, a primary idea for developing irrigation hydraulics was proposed. The agriculture irrigation process can be divided into four stages, namely, water conveyance, irrigation, soil water infiltration and water absorption of plant. Water conveyance and irrigation are included in irrigation hydraulics. Soil water infiltration belongs to soil physics, but water absorption of plant is closely related to water physiology of plant. Therefore, the basic theory of agriculture irrigation consists of irrigation hydraulics, soil physics and water physiology of plant. Accordingly, the basic concepts, objects and methods in irrigation hydraulics were proposed. Irrigation hydraulics should focus on investigation into the laws of water stream motion in water conveyance and irrigation with an objective that water can be delivered into soil economically and efficiently as well as distributed evenly. The connotation of irrigation hydraulics mainly includes three parts: laws of motion of irrigation water, hydraulic calculation of irrigation system and evaluation of irrigation uniformity. The contents developed in irrigation hydraulics can be served as a basic theory of irrigation and guide the research and development of technology and product in irrigation engineering, eventually provides new approaches and means for the design of an irrigation project.
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		2012 Vol. 30 (6): 726-732 [Abstract] ( 2729 ) [HTML 1KB] [ PDF 1387KB] ( 2474 )

	733	Entropy weight coefficient evaluation of irrigation and drainage scheme based on analysis of quality and rain ingredients of tomato
		SHAO Guang-Cheng, GUO Rui-Qi, 蓝Jing-Jing, CHEN Chang-Ren, GAO Zheng
		In order to find an irrigation and drainage treatment under which tomatoes have a good quality and high yield under rainshelter cultivation conditions in South China, effects of ten different irrigation and drainage schemes on plant growth, physiological indicators and fruit quality, yield of tomato were observed in a plot experiment, and a comprehensive index was proposed to assess the quality of tomatoes based on their main ingredients measured. The quality comprehensive index, yield, water consumption and irrigation amount were served as the indicators, then entropy weight evaluation values for the ten irrigation and drainage treatments were determined by using the entropy weight coefficient method. It was shown that the ninth treatment with the entropy weight value of 0.873was optimal, the better one is the fifth treatment with the weight valve of 0.85, and the poorest one was the first treatment with the lowest weight value of 0.593. The results indicated that for the ninth treatment where a 60% irrigation amount of the control treatment was applied, and the plastic drainage tube was located at 0.8m depth under the soil surface in the rainshelter cultivation condition, even the reduction in tomato yield was slightly reduced, the quality indexes such as soluble solids, titratable acidity, vitamin C, ratio of sugar over acid and so on were improved, causing better fruit taste and flavor; meanwhile, a high water use efficiency was achieved. Clearly, that treatment can be used as the irrigation and drainage scheme for tomato to have good quality and high yield in South China in rainshelter cultivation.
		2012 Vol. 30 (6): 733-737 [Abstract] ( 2082 ) [HTML 1KB] [ PDF 1175KB] ( 1772 )

	738	movement in layered soils during evaporation under perforated plastic mulch
		LI Yi, REN Xin, SI Bing-Cheng
		In order to reveal the evaporation characteristics of different textures of layered soils, two types of layered soils such as Lou soil and sandy soil, were selected to do column evaporation experiment in laboratory at three layer positions under the perforated plastic mulch conditions of 6 percentages of open area (0-100%). During the experiment the soil moisture and temperature distributions were measured, the evaporation was recorded against time as well. The results showed that soil temperature distribution is dependent of openholeratio and layer position; the temperatures on the soil surface under the condition with mulch fully covered at three positions are higher than the bare soil by 3.6, 66 and 21.8℃, respectively. The deeper the layer position, the more the difference of soil temperature between the soil surface and the deepest layer position. Such a difference is reduced for a larger openholeratio of mulch. A larger openholeratio results to a higher evaporation and the deeper the layer position, the higher the curve of cumulative evaporation against time. Power and logarithmic function can better describe the relationship between cumulative evaporation and time for both sparse and sandy soils. Generally, both openholeratio of mulch and layer position affect water and heat movement in soil.
		2012 Vol. 30 (6): 738-744 [Abstract] ( 2618 ) [HTML 1KB] [ PDF 1983KB] ( 1780 )

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