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Journal of Drainage and Irrigation Machinery Engin
 
2017 Vol.35 Issue.3
Published 2017-03-25

185 Influence of shroud contour of semi-open impeller on hydraulic performance of ceramic centrifugal pump
TAO Yi, YUAN Shouqi, LIU Jianrui, ZHANG Fan, TAO Jianping
In order to investigate the effect of shroud contour of semi-open impeller on the hydraulic performance of a ceramic pump, seven contours with different angles between the contour and the radial direction, namely 24°, 22°, 20°, 18°, 16°, 14° and 12° are designed and corresponding numerical simulations are carried out, the hydraulic performance as well as flow field in these pumps are obtained. The variations of static pressure, total pressure and relative velocity along streamlines from the inlet to the outlet of impeller, the mass flow rate through the gap between the casing and the contour and the flow rate at the outlet of impeller are analyzed in detail. The simulated results show that as the angle decreases the pump head and total efficiency decline, but also the highest efficiency moves towards a low flow rate. The increased leakage through the gap in the mid-portion of contour, reverse and secondary flows at the outlet of impeller are responsible for the reduction in both the head and the efficiency. A comparison between the simulated performance curves and tested data for the optimum(20° angle)and poorest(12° angle)cases is made. The simulated results show good agreement with the measurements, in consequence, the optimization design is achieved. The results presented in this paper can provide a reference for the design of shroud contour of semi-open impeller in ceramic centrifugal pumps.
2017 Vol. 35 (3): 185-191 [Abstract] ( 996 ) [HTML 1KB] [ PDF 3030KB] ( 772 )
192 Internal flow characteristics of residual heat removal pump during different starting periods
ZHANG Keyu, YUAN Jianping, SUN Wenting, SI Qiaorui
In order to investigate the evolution process of internal flow in residual heat removal pumps during different starting periods, the transient flow field in a residual heat removal pump is simulated by using a method based on the combination of Flowmaster and CFD technology, and the evolution processes of pressure, velocity and vortex in the impeller and guide vanes are analysed. A mathematical model is built for the motor starting period with Matlab-Simulink, then the motor speed variation with time is obtained through a simulation, showing the rated speed can be achieved at 5.5s. Further, a model is generated in Flowmaster to simulate the starting process of the residual heat removal pump, and the flow variations with time are obtained during different starting periods. Finally, the internal flow fields in the pump are analysed in ANSYS CFX during different starting periods. It is shown that the pressure gradient is obviously sharper during the alternating starting period than during the minimum flow starting period in pipeline because the pump is subject to a high temperature and high pressure condition in the former period, while the pressure distribution in the volute almost remains unchanged in the dual-pump operating period. The vortex evolution processes in the impeller and guide vanes all experience three different stages, namely, vortex generation, separation and disappearance in three different starting periods. Note that the vortex disappears sooner during the dual-pump operating period than in the other two periods. The flow in the flow passages becomes uniform at 5.5s, reflecting the inertia action of fluid affects the development of flow field in different starting periods significantly. The head is the minimum during the dual-pump operating period in comparison with the other periods, and the head rises with increasing impeller rotating speed with an overshoot as the speed stops accelerating. The overshoot effect is mostly evident during the dual-pump operating period. 
2017 Vol. 35 (3): 192-199 [Abstract] ( 1004 ) [HTML 1KB] [ PDF 2896KB] ( 717 )
200 Numerical analysis on transient characteristics of hydraulic turbine under variable working conditions
SHI Fengxia,, YANG Junhu,, WANG Xiaohui,
In order to study the transient characteristics of hydraulic turbine under variable working conditions, an unsteady three-dimensional simulation of internal flow field in a hydraulic turbine is performed based on the Reynolds time-averaged governing equations and standard k-ε turbulence model, the characteristics of transient pressure pulsation of internal flow field, radial and axial forces acting on the impeller are presented. The results show that the transient pressure pulsation is more obvious under variable conditions, though static pressure is smaller under low flow conditions, the pressure pulsation amplitude is the largest. The pressure pulsation amplitude is the smallest at best efficiency point, while the amplitude is in between under high flow conditions. The pressure pulsation amplitude in the interface between the impeller and the volute depends on monitoring positions, also a more violent amplitude is found at the volute discharge, a smaller one occurs in the tongue. The pressure pulsation amplitude rises with increasing flow rate. The dominant frequencies of pressure pulsation in the interface, at the inlet and outlet are equal to the blade passing frequency. There are radial and axial thrusts under various operating conditions. The distribution of transient radial force vector is approximately circular, but the transient axial force declines with reducing flow rate or vice versa and exhibits a nearly periodic vibration pattern with a minimum value.
2017 Vol. 35 (3): 200-206 [Abstract] ( 842 ) [HTML 1KB] [ PDF 1717KB] ( 709 )
207 Status of study on single channel centrifugal pumps and its developing tendency
FENG Jinsheng, LIU Houlin, DING Jian, WU Xianfang, DONG Liang
The application and structure of single channel centrifugal pumps are presented briefly. Then, the status of study on hydraulic design method, energy prediction model and unsteady fluid flow characteristics is outlined and summarized based on previous works achieved in China and abroad. Finally, the development trend of study on single channel centrifugal pump is prospected according to the current research results. Aiming at the strong unsteady characteristics inside the single channel of the centrifugal pump, it is essential to establish a formula for solving the slip factor within a full range of flow rate, and modify and update the existing formula for energy loss models, as well as develop an energy performance prediction model for the single channel pump. Based on a slip factor and performance prediction model, hydraulic design methods for single channel impellers can be put forward. Hence, the important issues in the study on single channel centrifugal pumps should include more extensive investigations into unsteady fluid flow characteristics, establishing more accurate energy performance prediction model and developing perfect design methods.
2017 Vol. 35 (3): 207-215 [Abstract] ( 1098 ) [HTML 1KB] [ PDF 1440KB] ( 799 )
216 Worldwide technical analysis on multistage centrifugal pump based on patent map
LU Zhanxiong, LIU Qiong, WANG Kai, CHEN Kun
In order to obtain development trends of multistage centrifugal pump, the technology in multistage centrifugal pumps was studied from the point of view of patent data, including patent application trend, patent distribution in various countries, IPC distribution, patentee distribution and patent citation frequency. At the same time, based on patent map technology, a few major research directions in multistage centrifugal pump technology were identified. It is shown that studies on multistage centrifugal pump technology are relatively little, mainly conducted in China, and in the developing stage, suggesting the multistage centrifugal pump technology is still a hot spot in research. Enterprises and individuals usually are patentees of multistage centrifugal pump technology abroad, but institutes and universities are the patentees in China, furthermore, these patents are not all commercialized. Themes of multistage centrifugal pump technology in patents are mainly focused on design of the pump parts, while those on its application are less. The core technology or basic study on multistage centrifugal pump is basically distributed in the United States, and the most frequently cited patent on multistage centrifugal pump is US7407371B2.
2017 Vol. 35 (3): 216-221 [Abstract] ( 5518 ) [HTML 1KB] [ PDF 1900KB] ( 922 )
222 Effects of canal lining on soil organic matters in Jing Huiqu Irrigation District and their spatial variability
WEI Xue,,,, ZHOU Beibei,,,, WANG Quanjiu,,,
In order to fully understand the impact of water-saving irrigation canal lining on soil quality, spatial and temporal variation characteristics of soil organic matter(SOM)and soil particles in both sides of lining canals are investigated in trunk and branch canals Jing Huiqu Irrigation District, Shaanxi Province by using traditional statistics, geostatistics and GIS. The results show that SOM in both sides of lining canals is 18.96-162.92 mg/kg with an average of 86.07 mg/kg, particularly, SOM is the maximum for cast-in-place concrete lining canals, and is the minimum for composite geomembrane lining cannels, is in between for masonry ling cannels. Based on a variogram analysis the semivariance function of SOM can be best fitted by using an exponential function with a 21.7 km range. The spatial covariance has a second-order trend and anisotropy on the spatial variability in the study area; and the spatial heterogeneity, caused by the relevant part of the overall spatial variability, accounted for a smaller proportion, presenting of moderate dependence on space and belonging to moderate variability. Using the ordinary Kriging interpolation method, the spatial distribution of SOM and soil particles are obtained; and the characteristics of the spatial distribution and influencing factors are analyzed.
2017 Vol. 35 (3): 222-227 [Abstract] ( 792 ) [HTML 1KB] [ PDF 1518KB] ( 705 )
228 The surge shaft hydraulic characteristics of hydropower station
HONG Zhenguo
In order to study the surge shaft hydraulic characteristics in turbine load change, taking Yang′er Hydropower Station surge shaft as research object, through the numerical method the surge shaft stability section, impedance hole size, the highest and the lowest water level are calculated; at the same time in order to prove the feasibility of numerical method, through regulation the calculation unit speed, spiral case pressure and draft tube pressure are guaranteed, and by model test the surge shaft hydraulic characteristics are further analyzed. Results show that the surge shaft stable sectional area is 688.134 m2, impedance hole diameter is 4.50 m, the highest surge water level is 2.120 m lower than the surge shaft top, the lowest surge water level is 5.541 m higher than the surge shaft bottom; spiral case maximum pressure rise is 67.85 m, the rate of rise is 29%; the unit rotating speed rise is 350.7 r/min, the rate of rise is 40%; the draft pipe minimum water pressure head is 0 m. Spiral case pressure, unit rotating speed and draft pipe pressure are in a safe and economical range. The surge shaft flow is stable, with good flow condition, no vortex, no negative pressure and the pressure difference of hole impedance is small.
2017 Vol. 35 (3): 228-234 [Abstract] ( 847 ) [HTML 1KB] [ PDF 1463KB] ( 858 )
235 End face modification and thermal characteristics of mechanical seal in emulsion equipment
CHEN Huilong, REN Kunteng, LI Tong, WANG Bin, ZHAO Binjuan
Failure of double end face of mechanical seals in emulsion equipment occurs frequently in operation. To overcome this problem, the end surface is modified by adding spiral grooves. Then the influences of flushing pressure on film thickness, opening force, temperature and fluid leakage and other performance parameters are studied numerically by considering the viscosity-temperature relationship of fluid based on a computational heat transfer model of fluid film, which is established by using dynamic mesh and UDF method. A comparative analysis of the relation between thermal characteristics and flushing pressure as well as the friction power consumption is conducted before and after the modification. It is shown that when the flushing pressure increases, the film thickness decreases, the film pressure and temperature as well as the leakage of the flushing fluid rise. In the modified seal, the mean peripheral temperature is reduced significantly. With increasing flushing pressure, the mean temperature increment is smaller, and is considerably less affected by flushing temperature and flow rate, additionally, the seal stability is strengthened. Under the same working condition, the flushing pressure can be reduced by 0.1-0.5 MPa to prolong the seal life and reduce the flushing system energy consumption significantly.
2017 Vol. 35 (3): 235-242 [Abstract] ( 993 ) [HTML 1KB] [ PDF 2460KB] ( 693 )
243 Numerical simulation of fan nozzle of guide board type cleaning jet flow field
YANG Yu, QIU Tao
In order to improve the cleaning efficiency and the cleaning quality of guide plate type fan nozzle jet, and optimize its structure, several 3D medels of the fan nozzle jet at different diversion distances,diversion angles and cleaning distances are established by using Pro/E software, which is aimed at the flow field characteristics of fan nozzle jet only around water. Based on the standard k-ε model, the numerical simulation of jet flow field is conducted for its flow velocity and pressure by the ANSYS Workbench software. The changing regularity of these models′ jet flow characteristics under the same boundary and initial condition is analyzed, which is beneficial to the design and optimiztion the guide board type fan nozzle. The results show that with the increase of inclination θ, the blowing pressure on the cleaned piece gradually decreases; on the contrary the clean range increases. As cleaning distance increases, the pressure on the cleaned part axis gradually decreases. And the clean range slightly increases. Thus, the cleaning effect of fan nozzle of guide board type is the best under the condition that the faninclination is 20°, the fan striking distance is 15 mm or 20 mm and installation height of nozzle is between 80 mm and 120 mm.The conclusion can provide reference for the design and optimization of fan nozzle.
2017 Vol. 35 (3): 243-247 [Abstract] ( 1070 ) [HTML 1KB] [ PDF 1582KB] ( 814 )
248 Applicability of one dimensional algebraic model in brackish water irrigation of severe saline-alkali soil
ZHAO Liandong, GAO Peiling,, WANG Naijiang, LIU Xiaoyuan, YANG Daming, LIU Quanzhong
In order to verify the applicability of one dimensional algebraic model in brackish water irrigation of severe saline-alkali soil, one dimensional infiltration experiments are conducted in laboratory on saline-alkali soil with different levels of mineralization degree(2, 3, 4 and 5 g/L). The model parameters are decided by means of experimental relationships between infiltration rate and wetting front as well as cumulative infiltration. Then infiltration time history and moisture content of soil profile are simulated numerically with the model. The root mean squared error(RMSE)and the index of agreement(D)are chosen to evaluate the applicability of the model. The results show that all the RMSE of infiltration time is less than 6.7 min; all the D produced by infiltration time model is more than 0.99. All the RMSE of water content is <3.5%; all the D produced by water content model exceeds 0.90. This suggests that one dimensional algebraic model can effectively describe the infiltration process of severe saline-alkali soil, this model also can simulate water distribution in soil profile more accurately after an infiltration ends.
2017 Vol. 35 (3): 248-255 [Abstract] ( 728 ) [HTML 1KB] [ PDF 1601KB] ( 514 )
256 Assessment of risk-based irrigation decision-making with consideration of future rainfall
NIE Qianwen, LUO Yufeng, LIU Fangping, LYU Xinwei, CUI Yuanlai, JIAO Xiyun
Increasing the use efficiency of rainfall is an effective way for saving agricultural water consumption. Although an irrigation decision-making based on future rainfall can improve rainfall use efficiency and reduce waste of water, there also exists a yield reduction risk caused from incorrect rainfall forecasts. Taking Ganfu Plain Irrigation District as an example, the water requirement of rice is predicted and irrigation schedules are decided based on the short-term temperature and rainfall forecast data in 2014-2015 in early and late season rice growing periods. In this risk-based irrigation decision-making strategy, the future rainfall is taken into account, and the new strategy is assessed against the convectional strategy in terms of water-saving, yield and number of irrigations. The results show that the risk-based irrigation decision-making with consideration of future rainfall can save 7.8%-16.7% water compared to traditional irrigation decision-making except for early season rice in 2014, in that case, two decision-making strategies predict the same irrigation water quota. Since rainfall is heavy in the early season rice growing stage, the yield is not affected by drought basically. For the late season rice, the yield predicted by the new strategy is lower but the reduction is within 0.3% and the number of irrigations is fewer by 1 or 2. Therefore, the risk-based irrigation decision-making can improve rainfall utilization efficiency, reduce number of irrigations and save irrigation water with a very little yield reduction.
2017 Vol. 35 (3): 256-262 [Abstract] ( 777 ) [HTML 1KB] [ PDF 1698KB] ( 697 )
263 Effects of bubbled-root irrigation interference infiltration on transport characteristics of water and nitrogen
LIU Xian, FEI Liangjun, LIU Yang
To improve the water and fertilizer utilization efficiency of bubbled-root irrigation, in this paper, experiments are carried out on field fertilizer infiltration to identify wetting front migration, wetting volume, soil water and nitrogen distribution in different distances between emitters(30, 40, 50, 60 cm). Results show that the distance between emitters has a great influence on the migration distance of wetting front and wet volume. With increasing distance between emitters, the maximum horizontal wetting distance and wet volume both are large, but the migration distance of wetting front and intersection time all decrease. After the irrigation, the soil moisture and NH+4-N content are the highest under the emitters and higher at the intersection. As redistribution continuing, the wetting front migration and wet volume increase, and NH+4-N content in the volume rises gradually. The redistribution for 1 day, the wetted body basically reaches steady state; for 5 days, the NH+4-N content achieves the maximum. Within 15 days of observation, the NO-3-N content is always in a steadily increasing state. The above results will lay a foundation for a better use efficiency of nitrogen and water in bubbled-root irrigation. 
2017 Vol. 35 (3): 263-270 [Abstract] ( 710 ) [HTML 1KB] [ PDF 2355KB] ( 602 )
271 Influence of irrigation method on alfalfa growth and water-salt dynamics
ZHANG Chang′ai,, XIN Shurong,, WANG Guoliang, WANG Chengzhang, SHENG Yibing
In order to optimize irrigation method for alfalfa growth in saline-alkali soil in the Yellow River Delta region, a field plot experiment was conducted. In the experiment, three irrigation methods such as natural rainfall, drip irrigation and flood irrigation are applied. The effects of these irrigation methods on plant height, population, yield and water-salt dynamics in the saline-alkali soil are observed. The experimental results show that the plant height and yield of alfalfa are all increased in flood and drip irrigations in comparison with natural rainfall. There is not significant difference in the plant height and yield of alfalfa from flood irrigation to drip irrigation with 60% water saving, suggesting drip irrigation is one water saving irrigation method which is worthy of recommendation to alfalfa cultivation. In flood irrigation, the water content in 0-60 cm thick soil layer is mainly affected, in drip irrigation, however, the water content in 0-20 cm layer is changed significantly. The salt content in 0-60 cm soil layer is affected greatly in flood irrigation in comparison with 0-20 cm soil layer in drip irrigation. The PH and EC values in 0-60 cm soil layer vary in flood irrigation, however, these values seem to show a uniform variation across the whole layer in drip irrigation. 
2017 Vol. 35 (3): 271-276 [Abstract] ( 798 ) [HTML 1KB] [ PDF 1463KB] ( 898 )
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