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Journal of Drainage and Irrigation Machinery Engin
 
2015 Vol.33 Issue.8
Published 2015-08-25
article
article
645 Effect of elbow on guide vane region flow for a bidirectional axial flow pump
Ma Pengfei, Wang Jun, Liu Weiwei, Cai Kuiyi
The elbow on an axial flow pump can cause interference to the upstream fluid of it. In order to investigate the best relative position between elbow and guide vane,a high specific speed bidirectional axial-pump was chosen as the study object to analyze the cause of numerical simulation results change, which occurred when guide vane grid rotated. It was found that the relative positions both between vane and blade and between vane and elbow can affect the steady numerical simulation results. Then the flow field of passage without guide vane and blade was simulated by the LES(Large Eddy Simulation)method, the cause of pump performance change was analyzed, and the result was verified by comparing the flow field of guide vane area at different positions. The results show that the pump performances at different positions of guide vane have a certain difference, and the inlet incidence angle of guide vane may deviate from the design angle.It can be used to reduce the influence of elbow on pump performance by extending diffusion tube, reducing elbow angle and adjusting guide vane arrangement in design.
2015 Vol. 33 (8): 645-650 [Abstract] ( 1191 ) [HTML 1KB] [ PDF 2212KB] ( 1263 )
651 Influence of volute configurations on radial force of hydraulic turbine
Yang Junhu, Li Tailong
In order to study the influence of the volute configurations on the radial force of the hydraulic turbine, the XWT 500-18 type hydraulic turbine in a chemical plant was selected as the research object. The SST k-ε turbulent model and the boundary layer grid were used to simulate hydraulic turbine with various volutes of single volute, double volute,in which the same impeller was adopted.The performance characteristics, pressure distribution and radial force of the hydraulic turbine with two different volutes were compared and analyzed according to the simulated results. The results show that the head and shaft power of single volute turbine are close to those of double volute turbine in all conditions. There is no advantage of performance in double volute turbine. The distribution of static pressure near the inlet of double volute impeller is not more uniform than that of single volute impeller due to the existence of the diaphragm. The radial force of the optimal point of the single volute turbine is the minimum which is half as large as that of double volute turbine. The radial force of the double volute turbine is higher than that of the single volute turbine overall while its balance is poorer. The direction and spiral angle of two kinds of turbines change greatly at small flow rates while its range is smaller at big flow rates. The results of the analysis can provide the reference of the understanding of the radial force and volute design in hydraulic turbine.
2015 Vol. 33 (8): 651-655 [Abstract] ( 1325 ) [HTML 1KB] [ PDF 2004KB] ( 1411 )
656 Influence of turbulence models on head prediction accuracy for centrifugal pumps
Yang Xingbiao, Li Hong, Chen Chao
In order to study the applicability of eddy viscosity turbulence model and Reynolds stress turbulence model in head prediction accuracy for centrifugal pumps, the heads of 10 specific speed centrifugal pumps were predicted under three different discharges(0.3Q, 1.0Q, 1.2Q)by using CFX 14.0 version of eddy viscosity model and Reynolds stress model. The predicted values were compared with the test values. The results indicated that as for the low specific speed centrifugal pump we recommended Reynolds stress BSL-EARSM model for 0.3Q. For head prediction of the discharge(1.0Q), the BSL-RS model, compared with the commonly used RNG k-ε, k-ω model, has higher prediction accuracy. When using the eddy viscosity class model to forecast the head of 1.0Q, the predicted values are less than the test values. For the head forecast at ns larger than 103, the simulation values are less than the test values. Researches provide reference for improving head prediction accuracy for centrifugal pumps.
2015 Vol. 33 (8): 656-660 [Abstract] ( 1407 ) [HTML 1KB] [ PDF 1340KB] ( 1576 )
661 Internal flow numerical simulation of centrifugal pump under gas-liquid two-phase flow
Liu Ruihua, Li Guidong, Wang Yang
A centrifugal pump at a specific speed of 129 was chosen to study the internal flow and pressure changes in the running process of centrifugal pumps under gas-liquid two-phase conditions. The unsteady numerical simulation for the full flow field of the pump was processed by the Eulerian-Eulerian inhomogeneous flow model based on CFX simulation software. The pressure pulsation and the volume distribution of the gas phase on the selected monitoring points and surfaces in the volute flow channel under different gas-phase volume fraction conditions were obtained. Comparing the numerical simulation with experimental performance curves, the results show that the gas phase volume is distributed mainly in the ipsilateral direction of impeller front cover in the flow channel of the volute. The monitoring points have the pressure pulsation frequency equivalent to the passing frequency of the blade under different gas contents. With the gas phase volume fraction increasing, the law that the pressure amplitude of monitoring points cyclically changes with time begins to be destroyed, the pressure pulsation frequency domain has a certain disorder and a series of fluctuations appear at low frequency. The fluid pressure of impeller is unevenly distributed due to the inhomogeneous distribution of the gas phase, thus making radial force which the impeller suffered decreased and its periodicity damaged.
2015 Vol. 33 (8): 661-666 [Abstract] ( 1572 ) [HTML 1KB] [ PDF 2263KB] ( 1311 )
667 Surplus energy recovery of industrial circulating cooling water and its key technologies
Li Yanpin,, Yuan Shouqi, Chen Dexin
Based on the research of structural mode of the industrial circulating cooling water system, three typical circulating water systems have been summed up, including the heating and cooling water series system, the heating and cooling water independent system and the circulating water open system. Through the analysis of the residual energy in the circulating cooling water system, it is found that whatever the structural mode is, the surplus energy is about 5-30 m generally, and in some systems it can be up to 50 m or so. All these belong to the low surplus energy system. Based on the surplus energy characteristic of circulating cooling water systems, three typical surplus energy recovery ways have been proposed, including turbine-fan unit, small or micro hydropower generating device and the turbine pump unit. For the three surplus energy recovery ways, the respective key technology or problems have been pointed out. The key of turbine-fan unit is the design of the ultra-low specific speed turbine, but its high cost, low efficiency, single model, lack of research on flow field; the key of surplus energy power generation is the selection of the turbine and its circulating water protection and reverse power protection; the key of the turbine pump unit is the design of the turbine or the reverse pump as turbine(PAT). And the differences between the PAT and the turbine, including the working process, the design theories and methods and the flow passage have been also pointed out. These differences lead to the low-energy density and low efficiency of the PAT. Therefore, the economic and technological comparison between the PAT and the turbine should be made to determine which should be selected in turbine pump unit.
2015 Vol. 33 (8): 667-673 [Abstract] ( 1296 ) [HTML 1KB] [ PDF 1312KB] ( 1551 )
674 CFD simulation of shutdown transient process of pumped storage power station under pump conditions
Zhang Languo,, Zhou Daqing, Chen Huixiang
Three-dimensional unsteady numerical simulations, combined with the normal single-phase model and the VOF model, were executed on the geometrical model of the whole flow system of a pumped storage power station. Through numerical calculation, the changeable flow configuration and variation law of some parameters, such as unit rotating speed, flux, runner moment and pressure of measurement points were obtained and compared with experimental data. Results show that the extreme value of unit rotating speed and measurement points pressure agree fairly well with experimental data. In the shutdown transient process, pressure variation at spiral casing inlet and draft tube inlet is influe-nced by the closure law of guide vanes, while that between runner and guide vanes is mainly affected by runner rotation. As guide vanes close and flux decreases, water flows upstream through the inner side of the draft tube and rotates with the runner. After guide vanes close completely, vortex inside the draft tube is the key factor of its hydraulic energy loss.
2015 Vol. 33 (8): 674-680 [Abstract] ( 1866 ) [HTML 1KB] [ PDF 7801KB] ( 879 )
681 Analysis of self-excited vibration caused by leakage of flexible valve in pump system
Si Jing, Yu Yonghai, Wang Jinxing
To analyze the flow characteristics of leakage as well as the mechanism of self-excited vibration in valves, a method of characteristics was used to assess the effect of flexible valve leakage on the self-excited vibration in water-supply pump system. The water level of piezometric pipe in upstream of valve as a function of time was obtained. Two comparative schemes were proposed to simulate the process of self-excited vibration by changing the length, the material of the pipeline and the leakage of valves in the above pump system. It is shown that the length and material of the pipe significantly affect the amplitude and cycle of self-excited vibration as well as the increasing rate of the vibration amplitude. In addition, the leakage of the valve has little influence on the amplitude and cycle of self-excited vibration, but has a significant effect on the increasing rate of vibration amplitude. A pipe explosion accident may occur without the inhibiting of self-excited vibration.
2015 Vol. 33 (8): 681-684 [Abstract] ( 1111 ) [HTML 1KB] [ PDF 1385KB] ( 1431 )
685 Study on solid-liquid two-phase flow characteristics of lubricating film in upstream pumping mechanical seal
Chen Huilong, Zuo Muzi, Wu Qiangbo, Xu Cheng, Wang Yu, Li Shulin
A three-dimensional geometry model and a numerical simulation model are established for an upstream pumping mechanical seal to study the solid-liquid two-phase flow characteristics of lubricating film in the seal. The two-phase flow in the film is simulated in Fluent based on the mixture model. The solid particle distribution features, the effects of particle volume fraction on the sealing performance are analyzed. The two-phase flow results are compared with the single-phase flow simulation. It is shown that the particles mainly culminate in the root surface of a spiral groove and on the sealing surface next to the root surface. Such a pattern becomes more evident with the increasing particle concentration. Meanwhile, the opening force of liquid film and the friction torque are augmented with the increasing particle volume fraction in the range of parameters achieved in the study.
2015 Vol. 33 (8): 685-690 [Abstract] ( 1196 ) [HTML 1KB] [ PDF 1563KB] ( 1336 )
691 Newlysimplified method for hydraulic design of microirrigation laterals based on emission uniformity
Ju Xueliang,, Wu Pute,, Paul R. Weckler, Zhu Delan,, Zhang Lin,
2015 Vol. 33 (8): 691-700 [Abstract] ( 974 ) [HTML 1KB] [ PDF 1592KB] ( 836 )
701 Effects of biological soil crusts on soil air permeability and water conductivity
Wang Weihua, Li Jianbo, Wu Xiangbo, Wang Quanjiu,
Biological soil crusts(BSCs), which develop in the semiarid water-wind erosion crisscross region of the Loess Plateau, north of Shaanxi Province, China, have great influence on soil air permeability and water conductivity. This study aims to assess the effects of biological soil crusts on soil air permeability, soil water storage capacity and infiltration rate of four types of biological crusts(no crust, BSC removed, 3 year crust and 7 year crust). The results showed that the same saturated water content corresponding to different soil air permeability, throughout the process of soil saturated water content increased and decreased, scilicet, soil air permeability in the process of water content decreased was significantly higher than the increased phase. Soil air permeability was significantly reduced by BSCs. Owingto the presence of biological soil crusts, soil total porosity and capillary porosity were increased significantly. Then soil water storage capacity was increased, but soil water permeability was declined. With the biological crust growing longer, the infiltration capacity declined more signifi-cantly. By comparing the three types of infiltration model, the coefficient of determination, R2, of Horton model was greater than that of other models, showing that Horton model fitted values are much closer to the measured values, and can better describe the soil infiltration characteristics under the co-verage of BSC in this study area.
2015 Vol. 33 (8): 701-707 [Abstract] ( 1506 ) [HTML 1KB] [ PDF 1621KB] ( 1447 )
708 Characteristics and influencing factors of crop water requirements in northeastern Yunnan
Wan Mengdan, Wang Lu, Zhang Yan, Liu XiaoGang, Yang Qiliang, Wu Hao
Based on daily meteorological data from three typical meteorological stations(Huize,Zhaotong and Zhanyi stations)during 1955—2013,rice,spring maize and winter wheat water requirements were calculated by FAO-56 Penman-Monteith equation and their changing trends were analyzed; simultaneously the influence of meteorological factors on main crops water requirements were probed by partial correlation and stepwise regression analysis.The results showed that at Zhaotong station, the main crops water requirements decreased in various degree with time. An decreasing tendency of rice,spring maize and winter wheat was 10.07 mm/10 a,1.44 mm/10 a and 1.06 mm/10 a,respectively. However, the main crops water requirements at other stations showed an increasing trend.Rice water requirements at Huize and Zhanyi stations were increased by 8.85 mm/10 a and 4.48 mm/10 a, respectively; spring maize water requirements were increased by 8.38 mm/10 a and 4.57 mm/10 a, respectively; winter wheat water requirements were increased by 7.39 mm/10 a and 3.10 mm/10 a, respectively.Besides, the water requirements of the same crop during different growth stages at the three stations were about the same. The order of rice water requirements at every growth stage was tillering>jointing>earing>milk>yellow maturity>turning green; for spring maize the order was jointing>grouting>seeding>booting>maturity; for winter wheat the order was milk>flowering>maturity>seeding.The influences of different meteorological factors on crop water requirements were different.Sunshine and mean wind speed were main factors, which had a significantly positive correlation with rice and spring maize water requirements. The climatic factors which affected winter wheat water requirements were different for every station.The winter wheat water requirements at Huize and Zhanyi stations had a significantly positive correlation with mean temperature and sunshine hours, while those at Zhaotong station had a significantly positive correlation with sunshine hours, but a significantly negative correlation with relative humidity.
2015 Vol. 33 (8): 708-715 [Abstract] ( 1038 ) [HTML 1KB] [ PDF 1361KB] ( 1123 )
716 Economic effects and coupling models of water and fertilizer of rice cultivated in aerobic soil
He Jinyu, Tian Juncang,,
To probe the relations of water and fertilizer with the yield, the field experiment on the mo-del of water and fertilizer coupling of rice cultivated in aerobic soil by mulch drip irrigation was carried out by a current rotary combination design, and its application prospect was comparatively analyzed. The relation between irrigation quota, nitrogen, phosphorus and rice yields was in line with the ternary quadratic regression model under the tested soil by mulch drip irrigation. The regression coefficients of the first term, the second term and the water-nitrogen interaction term have extremely significant level. The roles of increasing yields of the three factors were in order as follows: irrigation quota> nitrogen> phosphorus. There was a highly positive correlation between the estimating yields calculated by the model and harvest yields, of which predictive accuracy was up to 99%. Thus the irrigation quota and fertilizer application with maximum yield and their maximum yields were calculated by the regression model. On the basis of this, the optimum schemes of water and fertilizer to achieve target yields were proposed. If target yields were 9 300-9 600 kg/hm2, the irrigation quota, nitrogen and phosphorus application were from 9 730-10 500 m3/hm2, 272-363 kg/hm2 and 136-147 kg/hm2, respectively. If the economic benefits were considered, the optimum irrigation quota, nitrogen and phosphorus application were 8 500-9 015 m3/hm2, 225-240 kg/hm2 and 90-120 kg/hm2, respectively. The results from the different planting patterns showed that the yields of rice cultivated in aerobic soil by mulch drip irrigation were hardly different from those by the irrigation after direct seeding, which has roughly the same production costs as the rice seedlings transplanting cultivation, but, of which water use efficiency was much higher than that of the other three planting patterns(about 1.06 kg/m3 on average). Compared with the conventional transplanting seedlings cultivation, the planting way to rice cultivated in aerobic soil by mulch drip irrigation saves about 50% water and about 30% fertilizer.
2015 Vol. 33 (8): 716-723 [Abstract] ( 1231 ) [HTML 1KB] [ PDF 1395KB] ( 1354 )
724 Design and optimization of transmission system for hose reel irrigators based on planetary gears
Zhao Jin, Qiu Zhipeng, Peng Tao, Tang Yue
In order to improve the efficiency of hose reel irrigators and broaden the speed range of the water turbine or motor on it, a new kind of transmission system is designed based on three-stage pla-netary gear.This new type of transmission structure got three gears: the gear of the normal work, power recovery gear and manual recovery gear. The efficiency of new transmission system improved nearly 21%. Aiming at maximizing transmission efficiency and minimizing volume of three-stage planetary gear part, a multi-objective optimization model is established. Traditional optimization algorithms take discrete variables for continuous variables which may cause infeasible results. In order to solve the problems caused by rounding to the module or the number of teeth, genetic algorithm toolbox GADS is used to deal with the mixed discrete variables problems by the multi-objective linear weighting method. The optimized results show that the efficiency of three-stage planetary gears increases 10.64% and vo-lume decreases 16.3%.The newly designed model for the transmission system of hose reel irrigators can be referred in view of the research and development of the new prototype.
2015 Vol. 33 (8): 724-730 [Abstract] ( 1484 ) [HTML 1KB] [ PDF 1623KB] ( 1439 )
731 Pressure effect on rolling irrigation system uniformity
Li Qichao, Sun Wenfeng, Wang Yanhua
To solve problems such as uniformity poor, mobile inconvenience, large scale rolling irrigation system was developed. The effect of pressure on water distribution uniformity and intensity of the rolling irrigation system were investigated by single factor multiple comparison experiment. Using the functions of Design-expert. The results showed that pressure significantly influence the water distribution uniformity, and the water distribution uniformity increased with the increase of pressure. When the pressure is less than 0.30 MPa, the irrigation intensity had positive correlation with pressure. But when the pressure is larger than 0.30 MPa, the influence was insignificant. When the pressure is 0.40 MPa, the average water distribution uniformity coefficient is 88.75% and irrigation intensity is 12.3 mm/h, which meet the performance requirements of large scale side-roll irrigation system. The research provided reference for the promotion and application of rolling irrigation system.
2015 Vol. 33 (8): 731-736 [Abstract] ( 1102 ) [HTML 1KB] [ PDF 1612KB] ( 1320 )
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