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Journal of Drainage and Irrigation Machinery Engin
 
2016 Vol.34 Issue.8
Published 2016-08-25

645 Influence of impeller parameters on pressure fluctuation in pump outlet
CHAI Liping, YE Huan, REN Zhiming, LI Hui
In order to study the vibration performance of series-parallel pump′s outlet, fast Fourier transform and multi-coherent analysis technique was used to analyze the pressure data. Firstly, the orthogonal experiment of two parameters and three levels was carried out to evaluate the influence of the number of blades and the blade angle on impeller′s outlet. Then, the pressure signal of impeller′s outlet was fitted, the fitting degree of three signals was 0.809 6, 0.818 0 and 0.719 4, and was fitted the multi-coherent analysis technique was fitted to reveal the influence of primary and secondary impellers. The results indicates that the peak of frequency domain of impeller′s outlet pressure appears in the position of blade frequency, which accords with the rotation rule;the number of primary impeller′s blades affects the pump outlet pressure fluctuation most; and the peak value of pump′s outlet pressure reduces when the number of primary impeller′s blades increases. The research can be as a reference for the design of series-parallel pump.
2016 Vol. 34 (8): 645-650 [Abstract] ( 972 ) [HTML 1KB] [ PDF 1765KB] ( 1104 )
651 Effect of rotating speed on cavitation performance of nuclear reactor coolant pump
FU Qiang, ZHANG Benying, ZHU Rongsheng, CAO Liang
To study the effect of the rotating speed on cavitation performance and inlet flow pattern of the nuclear reactor coolant pump, thenumerical simulation and cavitation test at different speeds are conducted for AP1000 nuclear reactor coolant pump by the use of theoretical analysis, numerical calculation and experiments, then cavitation characteristics with different speeds(30, 40, 50 Hz )and different flow rates(0.7Qd, 1.0Qd, 1.3Qd)are obtained. The relationship between the static pressure distribution of the impeller inlet section and flow performance of the pump is analyzed. The results show that the rotating speed has a greater impact on pump cavitation performance under low flow conditions. With rotating speed reduced, cavitation trend curve change under low flow conditions is more apparent than under the high the flow conditions. The model can more easily gain access to critical cavitation when the NPSHC reduced at a high rotating speed under rated flow at different rotating speeds. The NPSHC is lower when the model pump is at a low rotating speed, and the slope of lift curve declines slowly in cavitation. At a rated rotating speed, the model pump in high flow more easily gets access to the critical cavitation. With the rotating speed and flow decreasing, the flow rate decreases, a reflux at the inlet of the model at the beginning of the pilot phase is caused more likely, which disrupts the inlet flow field, thus resulting in local severe cavitation.
2016 Vol. 34 (8): 651-656 [Abstract] ( 1239 ) [HTML 1KB] [ PDF 1768KB] ( 1031 )
657 Effect of wear-ring clearance on cavitation flow and performance of centrifugal pump with inducer
XIAO Liqian, LI Yibin,, LIU Yi,, BI Zhen, ZHAO Weiguo,
In order to investigate the effect of wear-ring clearance on the cavitation performance of the centrifugal pump with THE pre-positioned inducer, the cavitation flow and performance in the centrifugal pump with the pre-positioned inducer were numerically simulated with four different projects which were 0.15,0.25,0.40 mm and 0.60 mm based on the RNG k-ε turbulent model combined with Rayleigh-Plesset Homogeneous cavitation model,and compared with experimental results. The results show that the size of the wear-ring clearance has a greater influence on the external performance and cavitation performance; with the increase of the wear-ring clearance, compared with 0.15 mm, the total head efficiency and the head efficiency of the impeller decrease, the changes of the head are up to 0.60%,4.21%,and the changes of the efficiency are up to 6.50%,9.32%. Moreover, the head and efficiency of the inducer increase, and they are up to 29.86%,28.40%.The cavitation curves wave with the increase of the wear-ring clearance and the decrease of the cavitation number, and the wider the clearanceis, the more obvious the flactuationis. The cloudy cavitation bubbles are distributed on the pressure surface that is close to the front shroud, which causes cavitation instability, and the wider the clearanceis, the more the cavitaionis,the greater the critical cavitation numberis. It is found that the factors that influence the cavitation instability of the pump are possibly related to the impact of leakage high-pressure fluid of the wear-ring outlet on the main flow,the occurrence of cavitation at the intersection of impeller inlet and wear-ring clearance outlet and the change of the outlet flow angel caused by cavitating in the pre-positioned inducer.
2016 Vol. 34 (8): 657-664 [Abstract] ( 1368 ) [HTML 1KB] [ PDF 5297KB] ( 1002 )
665 Influence of guide vane blade number on pressure fluctuation in multistage centrifugal pump
MA Xinhua, FENG Qi, JIANG Xiaoping, WANG Wei, LU Weigang
In order to investigate the influence of common denominator of impeller and guide vane numbers on pressure fluctuation in the multistage centrifugal pump, four guide vanes with different blade numbers were designed and the hydrodynamic performance at the rated point remained unchangable. Based on the standard k-ε turbulence model, computational fluid dynamics software CFX was employed to carry out the numerical simulation calculations. Pressure fluctuations at monitoring points of impeller and guide vane in the second stage of the pump are obtained. The results show that the numerical simulation results coincide with experimental results, which proves the feasibility of the numerical simulation. The matching form of having the greatest common denominator of impeller and guide vane number has an obvious influence on the static pressure distribution in multistage centrifugal pumps, mainly for the periodic disciplinarian of circumferential pressure in the inlet of guide vane. The number of impeller is the main factor causing pressure fluctuation in the guide vane, and blade passage frequency has a great impact on the flow-induced vibration. The amplitude of pressure fluctuation increases with the increasing of the number of guide vane.
2016 Vol. 34 (8): 665-671 [Abstract] ( 1034 ) [HTML 1KB] [ PDF 1903KB] ( 1313 )
672 Characteristics of pressure fluctuation in pump-turbine in turbine mode
QIAN Zhongdong, LU Jie, GUO Zhiwei, ZHANG Jianjun
In order to investigate the pressure fluctuation characteristics of pump-turbine in turbine mode, a three-dimensional unsteady flow in a pump-turbine is numerically simulated using the shear stress transport(SST)k-ω turbulence model. By comparing computational flow discharge and efficiency with experimental ones, the flow models are validated. The pressure fluctuations in the guide vanes, runner and draft tube under three different operational conditions are analyzed, respectively. The results show that both the shape and the rotating direction of vortex rope have an obvious influence on the pressure fluctuation. At a low discharge, vortex rope is helical and has the same rotating direction with the runner, a severe low-frequency pressure fluctuation appears at the runner outlet. The frequency of pressure fluctuation on the runner blade is about 0.62 times the runner rotational frequency and the dominant frequency in the draft tube is about 0.36 times the runner rotational frequency. At an optimum and large discharge, the vortex rope is tubular, the amplitude of pressure fluctuation at the runner outlet is reduced. The dominant frequency of the pressure fluctuation in the draft tube is the same as the frequency of pressure fluctuation on the runner blade. At a large discharge, the vortex rope is in the inverse rotating direction of the runner, and the maximal amplitude in the pressure fluctuation in the draft tube appears at the tube elbow. 
2016 Vol. 34 (8): 672-678 [Abstract] ( 1269 ) [HTML 1KB] [ PDF 2911KB] ( 1120 )
679 Numerical calculation on cavitation range of large-scale drainage pumps system
YAN Hao, CHAI Liping, LI Yue, LI Qiang, SHI Haixia
To study the cavitation range of large-scale drainage pumps system, based on SST k-ω turbulence model, the pumps internal cavitation is described by using the Rayleigh-Plesset model, combined with the model pump experiment to verify the numerical results. Also, the emphasis is put on the distribution of cavitation, cavitation volume fraction under the same inlet water level and different flow coefficients, and blades surface pressure distribution under the large flow conditions. The result shows that under the optimal conditions, when the flow coefficients(δ)are 0.8 and 1.0, blades angles of the non-cavitation ranges are-8°-0° and-8°-+6°; the cavitation range rapidly expands for lowering the inlet water level; on the contrary, the range will decrease. However, under the larger flow conditions, the more the blades angle deviation from 0° is, the greater the volume fractions are conditions under the larger flow. What’s more, when the water level is up to the highest flood control water level, the biggest operation flow is 28.75 m3/s in non-cavitation conditions; and the blades surface pressure distribution will increase as the blades running angle enlarges under the large flow conditions. The results can provide a reference for the stable operation of the large-scale drainage pumps system.
2016 Vol. 34 (8): 679-685 [Abstract] ( 1146 ) [HTML 1KB] [ PDF 1603KB] ( 987 )
686 Numerical analysis of internal flow of abrasive entrained waterjet nozzle
LONG Xinping,, LIU Qi,, RUAN Xiaofeng,, CHEN Zhengwen, XUE Shengxiong, WU ziquan
Abrasive entrained waterjet nozzle is a core component of high-pressure abrasive waterjet equipment. In order to investigate the internal flow and particle movement in the nozzle, numerical simulation of the multiphase flow in the nozzle was conducted based upon the Euler-Lagrange approach, and Discrete Particle Method was adopted to calculate the trajectories of abrasive particles by taking the shape factor of particles and the energy loss due to the collision with the wall into consideration. The results indicate that the air phase near the entrance of focusing tube has a comparatively large tangential velocity which will drag the particles to conduct circumferential movement, and the resulting centrifugal force will enhance the possibility of the collision of the particles with the local wall which can enhance the erosion in this area. A longer focusing tube will contribute to the dissipation of the circumferential movement and guarantee the particles ejecting from focusing tube without large tangential velocity. The decease of particle shape factor will enhance the acceleration of abrasive particles. The particle inlet velocity has little impact on the particle outlet velocity in the current nozzle model. The results are of importance to gaining a deep insight of the nozzle internal flow and nozzle optimization.
2016 Vol. 34 (8): 686-692 [Abstract] ( 1523 ) [HTML 1KB] [ PDF 1570KB] ( 1511 )
693
2016 Vol. 34 (8): 693-702 [Abstract] ( 687 ) [HTML 1KB] [ PDF 4866KB] ( 632 )
703 Analysis of crop water requirement and influence factors in Jinghui Canal irrigation district
SONG Yang,, LI Hui,, ZHOU Weibo,, DONG Qiguang
The transpiration and evaporation, and irrigation water requirement change of winter wheat and maize were analyzed by using CROPWAT model. The correlation coefficient of crop water requirement with meteorological factors was calculated by using SPSS software. The result showed that the average transpiration and evaporation of winter wheat was 634.04 mm in the whole growth period, and the peak appeared in the middle of April to mid-May, the whole irrigation area had the same trend of transpiration and evaporation of winter wheat; the average transpiration and evaporation of maize was 525.22 mm, and the peak appeared in the middle of July to late August, the maximum was 535.97 mm in Sanyuan and the minimum was 514.68mm in Fuping. Irrigation water requirement of winter wheat in the sowing-over wintering stage was minimum, and theat in the turning green-jointing stage increased. Irrigation water requirement of corn in the tasseling, flowering stage was 22.67 mm. July-August was for the grain formation-milk stage, water requirement was 63.53 mm, until late September, corn irrigation water requirement dropped off. Crop water requirement was positively come lated with temperature, whileit was negatively correlated with precipitation and it was less correlated with wind speed and relative humidity. Temperature, sunshine time and relative humidity are the main factors influencing the crop water requirement.
2016 Vol. 34 (8): 703-708 [Abstract] ( 899 ) [HTML 1KB] [ PDF 1767KB] ( 968 )
709 Characteristics of total phosphorus loss into surface runoff from farmland
ZHU Hao, , TONG Juxiu, , XIA Chuanan, , LI Jiayun, , HU Xiaonong, , YUAN Yongkun
To characterize phosphorus loss in surface runoff from farmland,simulated rainfall experiments were performed in a test field in Qingpu District of Shanghai. And different methods of fertilization were implemented to study the total phosphorus loss at different stages of runoff. The results show that phosphorus loss was more in the early runoff stage than that in the late runoff stage with stable heavy rainfall, and loss rate of the former is almost three times that of the latter. However, it takes a much longer time of the late runoff stage, so the mass of phosphorus loss will be large in the late runoff stage, which is approximately 1.5 times that of the early run off stage. Moreover, the total mass of phosphorus loss has a notable correlation with runoff volume where the correlation coefficient of them is close to 1 by computation, so runoff volume has a great effect on the mass of phosphorus loss. On the other hand, different applications of fertilizer also affect the bulk of phosphorus loss. The soil phosphorus would be easier to lose if the direction of fertilizer application is parallel to the direction of surface runoff flow,compared to the perpendicular flow. And the peak value of total phosphorus concentration in the former condition is almost 2.5 times that in the latter condition. The results will provide a significant reference for the reduction of reduce phosphorus loss and the corresponding non-point source water pollution.
2016 Vol. 34 (8): 709-714 [Abstract] ( 1126 ) [HTML 1KB] [ PDF 1438KB] ( 1210 )
715 Effects of alternate different irrigation amount modes on yield and water use efficiency of Cassava
ZHAO Yu, YANG Qiliang, WANG Qijian, LIU Xiaogang, WANG Weihua
In order to explore a compensatory effect of crops after encountering drought stress and then rehydration, the change of growth, yield and water use efficiency of Cassava under alternate different irrigation amount modes was studied. Five water treatment modes were designed in this experiment,i.e. three conventional watering treatments: T1, T2, T3(every time the irrigation amount of 10 mm, 20 mm, 30 mm, respectively), two alternate watering treatments: T4(repeated alternate two kinds of combined irrigation amount as 10 mm or 20 mm), T5(repeated alternate two kinds of combined irrigation amount as 10 mm or 30 mm). Results show that compared to T2 treatment, T5 treatment significantly increased total leaf area, total dry mass, yield, total water use efficiency by 31.1%, 20.3%, 64.6% and 114.0%, respectively. Compared to T3 treatment, T5 treatment saved irrigation water by 33.3%, the total dry mass reduced a little, but the root mass, total water use efficiency and yield significantly increased by 11.2%, 119.0% and 13.3%, respectively. Therefore, T5 treatment is the best mode to improve yield and water use efficiency of Cassava in greenhouse.
2016 Vol. 34 (8): 715-721 [Abstract] ( 1018 ) [HTML 1KB] [ PDF 1299KB] ( 1011 )
722 Variation of soil salinity in wasteland of oasis saline drip irrigation area in Xinjiang
LI Wenhao,, WANG Zhenhua,, ZHENG Xurong,, ZHANG Jinzhu ,
In order to investigate whether using drip irrigation has an impact on soil salt content and composition in wasteland of saline oasis area in Xinjiang or not,one wasteland next to the drip irrigation cotton field in a typical saline oasis area(Xiayedi irrigation area in Manasi river basin of Xinjiang)was fixed-point monitored for five years from 2009 to 2013 to analyze the change of salinity and ion in each soil sampling between 0 to 140cm. The results show that owing to the influence of irrigation in drip irrigation cotton field, ground water level rises and,groundwater mineralization is increased,there fore the increase of soil salinity in wasteland of saline oasis area from mid-april to mid-october of the same year is more than the reduction value from mid-october to mid-april of the following year in Xinjiang.Salt,SO2-4,Cl-,Mg2+,Ca2+,Na+,Cl-/SO2-4 and sodium absorption ratio are increasing year by year. The alkalinity of wasteland soil increased and the composition of zwitter ion changed year by year, but during this test the type of saline alkali soil belongs to chloride-sulphate solonchakall along in the studies area. After the drip irrigation technology popularized in oasis areas, saline wasteland becomes an important gathering place with reducing the salt content of farmland.
2016 Vol. 34 (8): 722-729 [Abstract] ( 1259 ) [HTML 1KB] [ PDF 1930KB] ( 1353 )
730 Analysis of effect of human activities on regional groundwater level
LIU Zhiyong, LIU Dong,,,, LIU Wenting, LUO Tianqi
To study the effect of human activities on underground water level, taking Heilongjiang Land Reclamation Mudanjiang Administration as an example,the number of wells,crops area, groundwater irrigation area and other nine factors were chosen, as the evaluation indicators of the effect of human activities on underground water level, and the technique for order preference by similarity to ideal solution(TOPSIS)was used to establish the effect degree evaluation model for quantitative analysis of the influence of human activities on the groundwater level of each farm, which is under Mudanjiang Administration, from the year 2000 to 2013. The results show that the effect of human activities on the groundwater level of farm 855,8510,8511, Xingkai Lake, Hailin and Ning′an is minimum; that of farm 857 and Yunshan is moderate; that of farm Qingfeng and from 858 is a little higher, and that of farm 850, 854 and 856 is maximum. The results reveal the temporal and spatial differences of the human activities effect on the regional groundwater level from 2000 to 2013. In space, the effect is gradually weakened from northeast to southwest;temporally,the effect is generally enhanced from 2000 to 2003, and is gradually weakened from 2004 to 2013.
2016 Vol. 34 (8): 730-736 [Abstract] ( 905 ) [HTML 1KB] [ PDF 1387KB] ( 1170 )
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