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Journal of Drainage and Irrigation Machinery Engin
 
2015 Vol.33 Issue.7
Published 2015-07-25
article
article
553 Numerical simulation of unsteady blood flows in Bi-ventricular Assist Device
Yuan Jianping, Sun Wenting, Wang Longyan, Fu Yanxia, Hong Feng, Zhou Banglun
The unsteady blood flow field in a new type of ventricular assist device, namely the Bi-ventricular Assist Device(BVAD)under the design condition is calculated based on a CFD method. The blood velocity, turbulent kinetic energy and shear stress, mass flow rate in the pump inlets, axial and radial thrusts acted on the different components are obtained; moreover the static pressure fluctua-tion in the volutes is also analyzed. The results show that there are no notable stagnant regions for thrombus formation in the device. The pressure and shear stress are distributed similarly and uniformly in the device, showing an excellent anti-hemolysis performance. Because of the symmetrical structure of the BVAD, the axial force has been basically balanced by itself. The radial force and torque on the impellers are relatively low, showing the device can endure a transient radial load well. The pressure fluctua-tions in the volutes vary periodically, exhibiting six peaks and six valleys in time domain. The dominated frequency at every monitoring point is the blade passing frequency of the device due to the rotor-stator interaction.
2015 Vol. 33 (7): 553-559 [Abstract] ( 1736 ) [HTML 1KB] [ PDF 3417KB] ( 4830 )
560 Numerical analysis of effect of blade tip clearance on pressure fluctuation in mixed-flow pump inlet
Li Rennian,, Hu Penglin, Li Yibin,, Bi Zhen, Zhou Dong
Because of considerable influence of blade tip clea-rance on performance and flow in a mixed-flow pump, a proper selection of the clearance is important in the design of the pump. In order to identify the effects of the blade tip clearance on the pressure fluctuation characteristics in a mixed-flow pump inlet, the unsteady, three-dimensional turbulent flows in the pump are simulated at 0, 0.5, 1.0, 1.5 mm clearances, based on the SST k-ω turbulence model and large eddy simulation(LES)approach. Also, the SIMPLEC algorithm and block structured grids are adopted. The simulations are conducted at low flow rates, and the pressure fluctuation characteristics in the impeller inlet are monitored. The results show that with the increasing tip clearance the pump head decreases gradually. The tip clearance has a significant effect on the pressure fluctuation distribution along radius in the impeller inlet, the pressure fluctuation amplitude is smaller in the primary flow region in the impeller inlet, while it gets larger near the wall. The dominated pressure fluctuation frequencies at various tip clearances are the blade passing frequency, but the pressure fluctuation is quite different from one clearance to another. Specially, a larger tip clearance can reduce the pressure fluctuation amplitude. This can be in favour of improving the operational stability of the pump. 
2015 Vol. 33 (7): 560-565 [Abstract] ( 1247 ) [HTML 1KB] [ PDF 1932KB] ( 1327 )
566 Inter-stage interaction and unsteady flow characteristics in multistage centrifugal pump
Kang Can, Yang Xin, Yu Xiaojie
To analyze inter-stage interaction and transient flow characteristics in a multistage centrifugal pump, numerical simulations of both steady and unsteady, three-dimensional turbulent flow in a two-stage centrifugal pump are conducted. Pressure fluctuations at monitoring points in both the impeller and diffuser passages are obtained at different flow rates. The results show that the first-stage diffuser is the key factor for determining the non-uniform velocity distribution at the inlet of the second-stage impeller. There is a strong rotor-stator interaction between the impeller outlet and diffuser inlet in each stage. Even though the geometrical shape of the whole flow passage is so complicated, the blade pas-sing frequency is still the dominating factor that decides the pressure fluctuation characteristics in the entire flow passage in the pump. By contrast, the pressure fluctuations are less affected by the number of diffuser vanes. The pressure fluctuation amplitude at the blade passing frequency within the impeller passages increases gradually from the impeller inlet to the outlet, but vice versa in the diffuser. The pressure fluctuation amplitude at the blade passing frequency is still dominated at low and high flow rates, however, the fluctuation amplitude is amplified, especially at the low flow rate. 
2015 Vol. 33 (7): 566-571 [Abstract] ( 1408 ) [HTML 1KB] [ PDF 2141KB] ( 1345 )
572 A nonlinear partially-averaged Navier-Stokes model for turbulence flow simulations
Liu Jintao, Zuo Zhigang, Liu Shuhong, Wu Yulin, Wang Leqin
Most of the RANS turbulence models solve the Reynolds stresses by using linear and isotro-pic hypothesis, causing inaccurate predictions for turbulent flows with severe adverse pressure gradient, or recirculation flows with large curvature or complicated separated flows. At present, partially-averaged Navier-Stokes(PANS)method has been found to be better than the LES with less mesh cells in the near-wall region. In this paper, a new nonlinear PANS turbulence model is proposed by modifying the RNG k-ε turbulence model and introducing a nonlinear method for solving the Reynolds stresses. The new PANS model is used to simulate the turbulent flow fields around a NACA0015 hydrofoil and in a 90° curved rectangular cross-section duct. The predicted results agree well with the experimental data, showing a more accuracy under strong adverse pressure gradient. This suggests the model can predict 3D nonlinear turbulent flows induced by separation precisely. The effectiveness, which the nonlinear PANS model captures the behavior of turbulent flows with strong adverse pressure gradient and large curvature, has been proven. The model potentially can be used to predict complex vortex patterns in a turbomachine.
2015 Vol. 33 (7): 572-576 [Abstract] ( 1335 ) [HTML 1KB] [ PDF 1727KB] ( 2246 )
577 Numerical simulation of internal flow field and performance prediction of reversible double suction pump
Wang Chunlin, Zeng Cheng, Yang Xiaoyong, Peng Haibo, Liu Dong
To study the different behavior of a double suction centrifugal pump when it is running as a pump and a turbine, the standard k-ε two-equation turbulence model and CFX software are used to simulate the internal flow filed in pump and turbine modes and their performances are predicted. The hydraulic performances at best efficiency points are calculated respectively in pump and turbine modes, and a comparison of the flow field is made as well. The predicted performance curves in the pump mode are compared with the experimental values, showing the numerical simulation can predict the performance curves accurately. When the pump running as a turbine, the best efficiency point is moved to a larger flow rate and the efficiency varied greatly across the whole range of flow rate. A too small flow leads the torque acted on the impeller by the fluid to the reversed direction and stops doing work on the impeller. Moreover the largest energy loss occurs in the vaneless region between the impeller and volute, namely the outlet of the impeller. Through an analysis of the internal flow field in pump mode, the detailed distributions of pressure and velocity vector are obtained, and these results can provide a useful base on the hydraulic design of a pump as turbine.
2015 Vol. 33 (7): 577-582 [Abstract] ( 1394 ) [HTML 1KB] [ PDF 3008KB] ( 1458 )
583 Numerical simulation of pressure fluctuation in self-priming vortex pump
Wang Yang, Peng Shuai, Liu Ruihua, Liu Yang
To study the transient flow characteristics in a self-priming vortex pump including the impeller, air-water separation chamber as well as the suction and discharge pipes, the transient turbulent flows inside a self-priming vortex pump are simulated under different flow rate conditions by solving Reynolds time-averaged N-S equations and RNG k-ε two-equation turbulence model using ANSYS CFX software. The performance predicted based on the steady flow model is compared with the measu-red one, and the steady flow field obtained is used to initialize the transient simulation; the pressure pulsations at a few monitoring points inside the pump are extracted. The results show that the dominated frequency in the pump inlet and outlet is in between the blade passing frequency and the rotational frequency. In the side flow channels contacted with the impeller, the dominated frequency is the blade passing frequency based on the number of blades in one side of the impeller, which exhibits an obvious peak in the radial direction. The fluid pressure fluctuation near the walls of the channels is mainly in the blade passing frequency of one side of impeller blades or its multiples. The pressure fluctuation in the gaps between the baffle and the impeller tip is more significant; but the peak fluctuation is commonly in the blade passing frequency of one side of impeller blades or its multiples except a dispersion of the fluctuation at low frequencies. In the gap, the pressure fluctuation in the blade passing frequency of one side of impeller blades is declined but the fluctuation in the blade passing frequency of the whole impeller blades is increased when a monitoring point is shifted circumferentially from the two boundary edges to the centre of the gap. The denominated frequency of pressure pulsation in the impeller passages is the rotational frequency, and the peaks of the pulsation are in the rotational frequency or its multiples, furthermore, the peaks themselves decrease with the increasing multiple. 
2015 Vol. 33 (7): 583-588 [Abstract] ( 1248 ) [HTML 1KB] [ PDF 3574KB] ( 1337 )
589 Experimental analysis of dynamic stress on blades of hydro-turbine
Chen Xueli, He Yongmin, Wang Jun, Wang Quan
A piece of experimental work is conducted on the different blades in the runner of a 600 MW hydro-turbine to study its operational stability and dynamic stress. The strain gauge data at 30 locations on a blade in the runner are acquired online by using a wireless dynamics stress instrument installed on the top of the power generator set, then the variation and frequency characteristics of dynamic stress at different guide vane openings are analyzed offline. Meanwhile, the vibration and pressure pulsation data in this machine are monitored simultaneously using another instrument based on NI hardware, the results are compared with and correlated to the dynamic stress observations. It is indicated that the amplitude of dynamic stress at round 30% design opening is higher than in the vortex-rope operational region, meanwhile the spectrum of pressure fluctuations in the penstock and draft tube has some similarity to that of dynamic stress. In the spectrum of pressure fluctuations and dynamic stress, the guide vane passing frequency and harmonics as well as plenty frequency components ranged in 30-50 Hz can be observed evidently.
2015 Vol. 33 (7): 589-593 [Abstract] ( 1469 ) [HTML 1KB] [ PDF 2515KB] ( 1445 )
594 Simultaneous optimization of pump station operation scheme and pipe network in multi-source and looped water injection system
Yang Jianjun, Gao Shu, Li Qingtang
The simultaneous optimization of pump station operation scheme and pipe network can improve the system operating efficiency furthest. Aiming at the multi-source and looped water injection system, a mathematical model for simultaneous optimization of operation scheme and pipe network is established, in which the start-up and stop status, displacement of pumps, and the connection status, diameter of pipelines are taken as design variables, the operating energy consumption and investment are served as objective function, and considering the constraint conditions of displacement, pressure, looped pipe network. Taking the features of the simultaneous optimization problem, a dual generalized chromosome coding was proposed to improve the existing genetic algorithm, and then was applied to solve the mathematical mode1. In the pump coding, the binary coding is adopted in the first row to indicate the start-up and stop status of pump, the real coding is adopted in the second row to present the displacement of pump. In the pipeline coding, the binary coding is adopted in the first row to indicate the connection status of pipeline, the integer coding is adopted in the second row to present the diameter of pipelines. Thus,an exact description of the optimization variables is realized. The method of initial solutions creating and many crossover and mutation methods that adapted to the optimize problem are designed, a part of constraint conditions are satisfied, so the number of infeasible solutions is reduced. An example is optimized by using the algorithm proposed, the results of simultaneous optimization compared with the results of pipe network optimization, the operating energy consumption is reduced by 4.66%, the investment of pipe network is reduced by 1.73%, showing simultaneous optimization has a remarkable energy saving effect.
2015 Vol. 33 (7): 594-598 [Abstract] ( 1385 ) [HTML 1KB] [ PDF 1346KB] ( 1388 )
599 Impacts of type of air valve on water hammer protection in pressurized pipelines
Li Xiaozhou,Zhu Manlin,Tao Can
There is blindness and randomness in using air valves in engineering application at present, hence water hammer protection in pressurized pipelines is simulated numerically for various types of air valves to establish some theoretical guidance for selection of air valve in application. According to theory of water hammer, a hydraulic transient mathematical model is built for pressurized pipelines. The effects of air valves on water hammer protection are predicted numerically in pressured pipelines by using the method of characteristics and by employing a few the examples. The results show that a traditional air valve installed at the pipeline high point can reduce negative pressure but can cause excessive pressure as well. The set of air valves with orifice area ratio ranged in 0.05-0.20 can reduce the negative pressure effectively but also can lower the excessive pressure. The anti-slam air valve with 0.05-0.20 orifice area ratio and nearly 1.0 floating pressure coefficient can reduce the negative pressure and can decrease the excessive pressure. Properly selecting air valves and optimizing their parameters can reduce the negative pressure in a pressurized pipeline significantly and prevent column separation to occur.
2015 Vol. 33 (7): 599-605 [Abstract] ( 1667 ) [HTML 1KB] [ PDF 1653KB] ( 1686 )
606 Numerical simulation and optimization of automotive water pump to eliminate shaft seal failure in high speed operation
Zhang Junjie, Shi Weidong, Zhang Desheng, Zhang Lin
A type of automotive water cooling pump broke down in an endurance test. The reason for the failure is the rubber components of the shaft seal experienced a high temperature caused from dry run. In order to investigate the causes for the failure, the 3D turbulent cavitating flow in the pump is simulated based on the time-averaged N-S equations, SST k-ω two equation turbulence model and homogeneous cavitation two-phase flow model. The results show that cavitation phenomenon occurs in the flow in the sealing chamber of the seal under high rotational speed and temperature conditions because of the loss of system pressure and the insufficient water flowing in the region of the seal. The created vapour is trapped and unable to take the heat generated by the seal away, causing the seal failure. Then, a few measures, such as installing ribs on the pump housing, altering position and size of balance holes in the impeller hub are taken to eliminate the cavitation phenomenon, and the corresponding numerical results are validated by experiments. The numerical and experimental results turn out that these modifications allow the sealing chamber is full of liquid and the cavitation does disappear; as a result, the seal failure phenomenon is eliminated. This research output is meaningful to some extent for guiding engineering practice.
2015 Vol. 33 (7): 606-610 [Abstract] ( 1420 ) [HTML 1KB] [ PDF 3330KB] ( 1403 )
611 Effects of regulated deficit irrigation on growth of drip-irrigated muskmelon in greenhouse
Yuan Baozhong, Zhang Qingya, Bie Zhilong
In greenhouse and under drip irrigation condition, the effects of regulated deficit irrigation on growth, yield, quality and water use efficiency of muskmelon(Yilishabai variety)are investigated. Five treatments: T1(75%-75%), T2(75%-55%), T3(65%-65%), T4(55%-75%)and T5(55%-55%)are conducted according to relative soil moisture of two different growth periods such as vegetative and reproductive growth stages. It is showed that the plant height, stem diameter and leaf area are diminished with the increasing water deficit in vegetative growth stage. During fruit development stage, the fruit size and yield depend on water deficit in both vegetative and reproductive growth stages, i.e. the more the deficit, the lower the fruit and yield. The yield of T1 and T2 is the highest, and T5 is the lowest, but T3>T4, and the differences between treatments are significant. The water use efficiency of T2 is the highest, the efficiency of T1 and T4 is lower. Compared with T4, the irrigation amount of T2 is basically the same. However, the yield and water use efficiency are increased by 26.2% and 27.7%, respectively. In quality, the content of TSS is increased as the water deficit is more severe. The contents of soluble protein, free amino acids and vitamin C are increased under full irrigation in vegetative growth stage and under deficit irrigation in reproductive growth stage. However, the deficit irrigation in vegetative growth stage and copious irrigation in reproductive growth stage are conducive to synthetize titrateble acid. Taking all things into consideration, the irrigation condition of T2(75%-55%)may be the most appropriate irrigation schedule with drip irrigation in greenhouse in Wuhan area.
2015 Vol. 33 (7): 611-617 [Abstract] ( 1884 ) [HTML 1KB] [ PDF 1465KB] ( 1478 )
618 Effects of waterlogging stress on change in nitrogen of winter wheat in South of China
Xiao Menghua, Jin Qiu, Chu Linlin
Water level control is a key technique to realize the united regulation of irrigation-drainage in a wheat field and plays an important role in improving the ecological environment of the field. In this paper, based on the water level control technology, the change of nitrogen in deep groundwater in winter wheat farmland is studied by using field experiment and laboratory analysis at different growth stages and water depths. It is shown that NH+4-N concentration in groundwater in flooding treatment is less than that in non-flooding treatment at the same drainage intensity, suggesting flooding helps reduce NH+4-N concentration in groundwater. Unfortunately, with the prolonging flooding time, the decreasing rate of NH+4-N concentration gets slow. Under the condition without flooding, the longer the groundwater control time is, the slower the drainage rate is, causing groundwater has enough time to contact with the soil and crop roots, and this is in favor of the decreasing NH+4-N concentration. Additionally, flooding can reduce NO-3-N concentration as well. In the case without flooding, the NO-3-N concentration increases slightly at reviving-tillering and jointing-booting stages under water level control, but the NO-3-N concentration rises considerably at heading-flowering and milking stages. There is a danger of NO-3-N leaching in the whole growth period of winter wheat.
2015 Vol. 33 (7): 618-625 [Abstract] ( 1034 ) [HTML 1KB] [ PDF 1891KB] ( 1279 )
626 Provincial-scale spatial variation of soil water-air-thermal parameters and its main controlling factor analysis
Wang Weihua, Li Jianbo, Wang Shuo, Wang Quanjiu,
The basic soil physical parameters and water-air-thermal parameters measured at 13 sampling points in Shannxi province are analysed to master their provincial-scale spatial distribution characteristics by making use of GIS technology and statistical methods. The effects of soil texture and type and land use on the water-air-thermal parameters spatial distributions are assessed by means of variance and regression analyses. The inverse distance weighted(IDW)interpolation results show that sand content decreases while clay content increases from north to south in the province. Soil saturated hydraulic conductivity, soil air permeability and thermal permeability decrease with declining sand content. Soil texture and type as well as land use are the main controlling factors of water-air-thermal parameters spatial distribution. Explanatory power of soil type on water-air-thermal parameters spatial distribution is better than land use, but weaker than soil texture. It is advisable that soil texture, soil type and land use should be analysed in a combined manner in the provincial-scale spatial distribution prediction of water-air-thermal parameters to improve the accuracy of prediction.
2015 Vol. 33 (7): 626-633 [Abstract] ( 1306 ) [HTML 1KB] [ PDF 3209KB] ( 3269 )
634 Optimization design of triangular labyrinth channel in drip irrigation emitter
Guo Lin, Bai Dan, Cheng Peng, Zhou Wen
In order to study the hydraulic properties of triangular labyrinth channels in drip irrigation emitter, a basic structure of the channels is specified and severed as the investigational model which is defined by the three geometrical parameters such as turning angle, width and height of triangular labyrinth channel. Then, 10 cases are designed based on these parameters by means of uniform design method. Computational fluid dynamics software Fluent 6.2 is adopted to simulate the flow field in the channel of emitters numerically. The geometrical model is generated for each case by using 3D software AutoCAD. Subsequently, the flow in each model is simulated by making use of CFD software Fluent 6.2 to analyze the hydraulic performance and flow characteristics of the model and to obtain flow visualization pictures. Additionally, the flow rate is extracted and correlated to the pressure drop across the model by employing linear regression method, and an index is established for flow pattern. A mathematical relationship between the index and the geometrical parameters is developed based on the results of 10 cases by using multivariable linear regression approach. The genetic algorithm is adopted to optimize the three parameters by minimizing the flow index. The optimized triangular labyrinth channel is subject to an excellent hydraulic performance, namely uniform velocity profile and steadily reduced pressure distribution, and the flow rate through it is in an allowable range as well. This optimized channel can be a reference case for parameterized design, precision control of geometrical parameters in manufacturing and final research and development of triangular labyrinth channel in drip irrigation emitter.
2015 Vol. 33 (7): 634-639 [Abstract] ( 1561 ) [HTML 1KB] [ PDF 1873KB] ( 1511 )
640 Practices for extension of sprinkler and micro irrigation technologies in Zhejiang Province
Shen Haibiao, Yi Yongqing
technical innovation,miniaturization in unit, precision in pipe diameter, and simplicity in fertilizer and pesticide application et al various measures were adopted and therefore reduced the cost of sprinkler and micro irrigation schemes. Application innovation: sprinkler and micro irrigation technologies were applied in bamboo, waxberry and paddy rice(rice seedling)et al over thirty crops; sprinkler and micro irrigation technologies have irrigation, fertilizer application, pesticide application, defrost, snow removing, and dust leaching et al many uses; sprinkler and micro irrigation technologies were also applied in cooling and disinfecting the breeding farm of pig, cow, sheep, chicken, duck, goose, rana-spinosa and earthworm et al, and increased the comprehensive benefit. Governmental predominance: the sprinkler and micro technologies can be extended through formulating planning, increasing investment and conducting technical training.
2015 Vol. 33 (7): 640-644 [Abstract] ( 838 ) [HTML 1KB] [ PDF 2170KB] ( 1389 )
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