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Journal of Drainage and Irrigation Machinery Engin
 
2015 Vol.33 Issue.10
Published 2015-10-25

829 Numerical investigation into the influence of installation location between diffuser vane and volute tongue on unsteady pressure fluctuations in centrifugal pump with vane diffuser
Zhu Xiangyuan, Jiang Wei, Li Guojun, Liu Pengfei
The diffuser installation location between the diffuser vane and volute tongue(clock effect)has a great effect on the performance of the single-stage centrifugal pump, which, however, is often ignored by designers. In this paper, the influence of clock effect on the unsteady pressure fluctuations in a centrifugal pump and the radial force of impeller are investigated. The steady-state hydrodynamic performance of the centrifugal pump with vaned diffuser was experimentally measured. Numerical simulations based on the Reynolds averaged Navier-Stokes(RANS)and turbulence models were carried out to obtain the hydrodynamic performance of the centrifugal pump applied in the experiments reported here. The numerical results of the hydrodynamic performance were in agreement with the experimental data. The accuracy of the utilized numerical approach was demonstrated. The unsteady flow characteristics of the centrifugal pump were numerically studied. The clock effect has great influence on the pressure fluctuation and the unsteady radial force imposed on the impeller.When ψ=25° or ψ=41°, the pump is characteristic of a small pressure fluctuation both in the impeller and in the diffuser, but a big pressure fluctuation in the volute. Small radial force on the impeller is another characteristic when ψ=25° and ψ=59°.Thus the diffuser should be properly installed so that the volute tongue is located near the middle of two diffuser vanes to obtain better performance.
2015 Vol. 33 (10): 829-834 [Abstract] ( 1288 ) [HTML 1KB] [ PDF 2212KB] ( 848 )
835 Modal analysis of centrifugal pump casing under pumps as turbines
Dai Cui, Bai Yuxing, Dong Liang, Kong Fanyu, Xia Bin
The PAT(pumps as turbines)is one of the best alternatives for energy recovery,and the modal analysis of pump casing has a crucial effect on the vibration performance of PAT. In order to grasp the effect of noise caused by vibration under different pump casings and testify the accuracy of the element model of pump casing, the present work is to analyze the pump casing modal by hammering under the condition of pumps as turbine. The modal experiment platform is established for meeting the feature of pump casing. The reliability and accuracy of experiment plan are achieved through experimental modal analysis. From the comparison between the numerical analysis under the three-dimensional model of pump casing and experimental results, each modal of casing is independent and orthogonal, which means that the accuracy of the experiment is obtained. The result also shows that the finite element model of pump casing can better reflect the dynamic characteristics and can be used to analyze the noise induced by vibration.
2015 Vol. 33 (10): 835-839 [Abstract] ( 1540 ) [HTML 1KB] [ PDF 2400KB] ( 859 )
840 Flow field analysis of interstage flow channel in a multistage split casing centrifugal pump
Cong Xiaoqing, Zhang Xiao, Yuan Danqing, Ge Jiajun
In order to study the distribution regularities of flow velocity, static pressure and turbulence energy of the interstage flow channel in the multistage split casing centrifugal pump,numerical simulation calculation was made for the interstage flow channel in the multistage split casing centrifugal pump in the design conditions. Based on the original design of the reflux and swirl generated by the diversion blade, three different improved schemes were proposed by changing the shape and position of the guide vane. Numerical simulation calculation was made for the improved schemes,the flow changes of three kinds of schemes were analyzed and energe loss values of four different interstage flow channels were calculated by integral.After the comparative analysis scheme2 was defined as the best, and the accuracy of numerical simulation calculation was verified by experiment. The results showed that the fluid flows along the interstage flow channel, circumfluence and vortex at guide vane of the bridge terminal caused some energy loss, thereby affecting the performance of the centrifugal pump. Changing the inlet angle of the front end and the outlet angle of the back end aims at improving the overall performance and the efficiency of the multistage split casing centrifugal pump.
2015 Vol. 33 (10): 840-845 [Abstract] ( 1555 ) [HTML 1KB] [ PDF 3445KB] ( 754 )
846 Numerical analysis of effects of splitter blades on cavitation performance in a centrifugal pump
Zhang Yunlei, Yuan Shouqi, Zhang Jinfeng, Feng Yaoning, Mao Jieyun
The pump cavitation performance will be influenced by the additional splitter blades because the shape of the impeller inlet channel is changed. In order to investigate the influences, four impeller schemes were presented based on a model pump IS50-32-160, one without splitter blades and another three with splitter blades of different inlet diameters. By using the CFD technique, numerical simulations were carried out to investigate the characteristics of internal flow and the pump cavitation performances at different NPSHA. The results show that the cavitation performance of pump is improved by the additional splitter blades, and that the proper selection of the inlet diameter of splitter blades contribute to the degree of improvements of the cavitation performance of pump, which even could avoid the blocking at the impeller inlet and vortex cavitation inside the water passage effectively, and that the cavitation performance reaches its best when the inlet diameter of splitter blades is 0.725D2 for the pump model under our investigation.
2015 Vol. 33 (10): 846-852 [Abstract] ( 1339 ) [HTML 1KB] [ PDF 2930KB] ( 835 )
853 Design and optimization of new-type space guide vanes for multistage centrifugal pump
Yuan Danqing, Han Yongtao, Cong Xiaoqing, Shi Rong
In order to improve the performance of multistage centrifugal pumps, a new guide vane was designed. The basic design principle originated from the twisted centrifugal impeller and runner guide vanes design method. By fixing the inner edge line and outer edge line, a twist surface of new guide vane was shaped. The guide vane smooth was linked up with positive and negative vanes, and a twisted blade was formed. The vanes were split into several independent continuous varying flow channels, which helps reduce water loss of guide vanes. For a high-pressure multistage centrifugal pump, different configurations of guide vane were developed. Through the evaluation of the different configurations of guide vane, by means of CFD analysis, the design rule of new-type space guide vane was studied. An optimal configuration was obtained, and by prototype testing the model had better hydraulic performance, its efficiency reached 85.68% at the design point to meet the design requirements, which proved the feasibility of this design method. This method will facilitate energy saving of multistage centrifugal pumps, and provide a useful reference for the development of guide vane.
2015 Vol. 33 (10): 853-858 [Abstract] ( 1723 ) [HTML 1KB] [ PDF 1572KB] ( 1071 )
859 Laterally averaged two-dimensional modeling of thermal structure in river-type reservoirs
Dai Lingquan,, Dai Huichao,, Mao Jingqiao, Jiang Dingguo
The impoundment of the reservoirs has a strong influence on the hydrologic regime of the natural river course, and the water thermal structure characteristics maybe change at the same time. In this work, a laterally averaged two-dimensional model for river-type reservoirs to simulate water temperature is developed. Taking the Three Gorges Reservoir(TGR)show as an example, the thermal structure after the operation of the TGR is predicted based on a normal year and an extreme dry year. Results show that the temperature has marked difference in the longitudinal direction in Spring and Summer, the commonly used one-dimensional model is difficult to reflect the real vertical temperature distribution near far from the dam; the reservoir has no stable thermal stratification during the whole year in different typical years, but in Spring, a transient and weak stratification may arise, the maximum temperature difference in the vertical direction in a normal year is 8.14 ℃,while it is 8.82 ℃ in an extreme dry year. The regions of the large temperature gradient(<100.0 m)are located below the elevation of the power plant intake(130.0 m).The water in the region with the large temperature gradient does not affect the discharged flow from the Three Gorges Reserovir in Spring.Therefore, the results can provide a scientific basis for management of the ecological environment in the Three Gorges Reservoir.
2015 Vol. 33 (10): 859-865 [Abstract] ( 1573 ) [HTML 1KB] [ PDF 2107KB] ( 1043 )
866 Several typical transient processes of pump turbine
Liu Kaihua, Zhang Yuning, Xian Haizhen
In order to study the negative effects of abnormal transient processes on the pump turbine and the corresponding improved measures, the inherent feature of performance curve of the pump turbine(named S-shaped characteristics),together with the recent research progress in several typical transient processes of the pump turbine, is introduced. The S-shaped characteristics shown in the performance curve of the pump turbine along the guide vane opening line are briefly introduced, with its physical origins and negative effects. A detailed introduction to the hysteresis phenomenon of the pump turbine is performed and it is found that the present discharge of pump turbine at the fixed rotational speed is not a unique value because the operational condition of the pump turbine depends not only on the current input of the system but also on the history of the system and hence the hysteresis phenomenon leads to the drop of water head,low efficiency, vibrations and noise. The generation condition of the hysteresis phenomenon, the influence of rotational speed and the improved methods based on changing runner inlet and outlet angles are set forth. Measurement of the dynamic stress on the shaft and influences of the rotor-stator interaction on the measured signal analysis are both elaborated,giving the corresponding phenomena, basic characteristics and paramount influencing parameters. The instability of the pump turbine working with no load at start-up as well as the instability at the guide vanes closure, and the solutions to them are also expounded. Mereover, the advantage and the disadvantage of different methods are compared.
2015 Vol. 33 (10): 866-873 [Abstract] ( 2519 ) [HTML 1KB] [ PDF 1444KB] ( 1356 )
874 Numerical analysis on effect of real gas on spiral groove dry gas seal performance
Song Pengyun, Chan Wen, Mao Wenyuan, Jiao Feng
The sealed gas of the dry gas seal is generally considered as an ideal-gas when the dry gas seal is investigated and designed. However, some gases performance may be quite different from the ideal-gas at the high pressure. Some familiar gases, such as air, carbon dioxide(CO2), hydrogen(H2)and nitrogen(N2)were studied. As to the widely used spiral groove dry gas seal, the three-dimensional numerical simulations were performed by a CFD software. The effect of real gas on the performance of the spiral groove dry gas seal, such as the opening force and the leakage, has been investigated, and the fact that the gas film temperature varies along the seal face when the gas flows through the seal faces is considered at the same time. The results show that in the range of pressure no more than 4.6 MPa, the sealing performance of air and N2 real gas is basically the same as that of ideal-gas. The opening force and the leakage of CO2 real gas in spiral groove dry gas seal are greater than those of ideal-gas, while the opening force and the leakage of H2 real gas are slightly less than those of ideal-gas. The real gas behaviour has obvious effects on the leakage of the dry gas seal, but little effects on the opening force.
2015 Vol. 33 (10): 874-881 [Abstract] ( 1574 ) [HTML 1KB] [ PDF 2229KB] ( 966 )
882 Numerical simulation of flow field of Fan based on ANSYS Workbench
Chen Huimin, Zhao Guangyin, Shu Changdong, Hu Shanfeng
Calculation modeling and solution techniques for flow field of universal axial fan Z-490 based on its characteristics is presented.A CFD model is finished and the relationship between total pressure,power consumption,efficiency and flow rate of the fan is calculated by using CFD software Workbench 13.0 and validated with test results. Through investigations into the inner pressure and velocity fields of the fan,the causes for backflow near the fan tip and low efficiency are analyzed.Compared static pressure and efficiency of the fan without rotating ring and the fan with rotating ring,results prove that the fan with rotating ring can have higher static pressure and efficiency. Compared the two kinds of rotating ring of static pressure and efficiency, results prove that the fan with 40mm width ring can have higher fan performance.
2015 Vol. 33 (10): 882-886 [Abstract] ( 3209 ) [HTML 1KB] [ PDF 1856KB] ( 1397 )
887 Influence of underground water level regulation on nitrogen and phosphorus concentration of drainage in winter wheat fields
Xu Cuilan, Sun Zhenhai, Meng Jiajia
To seek the optimal water control mode for reducing the nitrogen and phosphorus losses, so as to achieve high yield, pollution reduction, and water saving, the effect of nitrogen and phosphorus losses in winter wheat was studied by different field groundwater table controls. The results show that different water control patterns had an obvious effect on nitrogen and phosphorus concentration in winter wheat. Through the control of underground water, ammonium nitrogen(NH+4-N)in underground drainage at different growth stages of winter wheat was decreased, but the nitrate nitrogen(NO-3-N)was increased.Total phosphorus(TP)concentration of water treatment with the water level of 100mm kept increasing at the jointing-booting stage and kept decreasing at the heading-flowering stage, while that with the water level of-200 mm kept decreasing at the jointing-booting stage, but kept increasing at the heading-flowering stage. Soil available nitrogen content of winter wheat was reduced at the jointing-booting stage. Maintaining high water level at the heading-flowering stage was conducive to reducing the available nitrogen content. Available phosphorus content at the jointing-booting stage in soil was reduced to a certain extent. Maintaining high water level at the heading-flowering stage can reduce the available phosphorus content. At the lower water level, the longer the water control time was, the greater the available phosphorus content was.
2015 Vol. 33 (10): 887-894 [Abstract] ( 1392 ) [HTML 1KB] [ PDF 1690KB] ( 768 )
895 Comprehensive evaluation of irrigation district operational status based on improved entropy weight-G1-game theory method
Fei Liangjun, Wang Jinhui, Wang Guangshe, Feng Chanli, Li Kun
In order to reflect the importance of each index to evaluating irrigation areas, each index is endowed with the different weights to reflect the difference of its importance, and the accuracy of the comprehensive evaluation result also depends on the rationality of the index weight assignment. The G1 method is applied to subjective empowerment of evaluation index and the improved entropy method is applied to weight of indicators so as to meet the objectivity of the weight and guarantee that the assessment result has a certain explanation. Then the integrated method of game theory is adpted to integrate subjective and objective weights, so that the comprehensive weight of each index is obtained. The determined comprehensive weight is applied to verifying the Luohui Canal, Shaanxi large-scale gravity canal irrigation district as an example by the improved linear model. The calculation results agree with those by the extension evaluation method on the whole. With the passage of time, the evaluation level of the Luohui Canal irrigation district gradually becomes good, and the operation condition is getting better and better, which conforms to its development reality.
2015 Vol. 33 (10): 895-900 [Abstract] ( 1197 ) [HTML 1KB] [ PDF 1286KB] ( 908 )
901 Influence of the Yellow River water filtered on drip irrigation system
Sun Guanfang, Yu Jian, Du Bin, Qu Zhongyi, Shi Jigang, Zhang Ruixi
In order to investigate the possibility of drip irrigation with the Yellow River water filtered with 300 mesh, an experiment simulating a field drip irrigation system was carried out to study the process flow changes of Nf 0.72, Nf1.60, Nf2.20, Dy1.38 at different locations, the law of system average relative flow, the coefficient of variation of emitter discharge, and the system uniformity, as well as relationships between them. The results showed that the emitter clogging developed rapidly early on, the average relative flow rate of all systems showed a law of gradual change at first, followed by a rapid decline, then returning to a gradual rate of change with the increase of irrigation frequency, with the point of rapid decline at the average relative flow of 75%. The coefficient of variation of emitter discharge, which increases linearly from the beginning and then continues to run smoothly, is a strong linear relationship(p<0.001)with the system mean relative flow. When the system average relative flow is greater than 75%, drip irrigation systems Christiansen uniformity coefficient Cu and Ln Qr is a linear relationship(R2=0.790 9), therefore, it is practical to determine the drip irrigation system uniformity through the average relative flow, thus grasping the system clogged conditions in time and decision-making conveniently for its operation and management.
2015 Vol. 33 (10): 901-907 [Abstract] ( 1182 ) [HTML 1KB] [ PDF 1574KB] ( 820 )
908 Droplets distribution research of impact sprinkler based on Laser Precipitation Monitor
Zhu Xingye,, Liu Xingfa, Liu Junping, Jiang Jianyuan, TianKun
In order to research the droplet distribution of rotating sprinkler,droplet diameter and droplet velocity of 3026B impact sprinkler were measured by Laser Precipitation Monitor. The experiment was applied under the operating pressure of 0.15,0.20,0.25,0.30,0.35 MPa with no wind. Droplets mathematical models were built based on the method of least squares. Results showed that the relationships between droplets diameter and the distance along the sprinkler were indicted by exponential function,except the droplets at 4 meter from the sprinkler. The droplets frequency were up to 56.8%,64.35%,72.14%,61.72%,40.17% respectively, under the operating pressures of 0.15,0.20,0.25,0.30,0.35 MPa. The droplets frequency was the ratio of the droplets volume that diameter between in 1-3 mm to all the droplets in the whole spray area. The slope of droplets diameter cumulative frequency curve decreased with the operating pressure increasing. The relation between droplet velocity and droplet diameter were indicted by linear function model built. There were exponential relationships between droplet kinetic energy and the distance along the sprinkler.
2015 Vol. 33 (10): 908-914 [Abstract] ( 1209 ) [HTML 1KB] [ PDF 1878KB] ( 899 )
915 Key components design and experiment of roll wheel line move sprinkling irrigation machine
Wang Yanhua, Sun Peiling, Sun Wenfeng, Wang Teng, Chong Baozhong
To solve the problems of weak independent research ability, low technical content, poor equipment reliability and high economic cost in water-saving irrigation technology, a roll wheel line move sprinkling irrigation machine was designed which can save aluminum alloy material, reduce fuel consumption, and is more reliable and has high sprinkler irrigation uniformity. According to the mechanical characteristics of water pipes, by using Matlab to optimize the design of the thickness of water pipes, the optimized water pipes with three different thickness can save material and increase climbing ability. The structure of the automatic drain valve was designed, its important parameters were calculated, and the simulation experiment was carried out by ANSYS CFX. The field performance test result shows that the roll wheel line move′s indicators meet the requirements. When the sprinkler moves forward, the maximum deflection of water pipes is 2.7 m, irrigation uniformity is 92.45%, irrigation intensity is 12.59mm/h. The study can provide a reference for the further development of a roll wheel line move sprinkling irrigation machine.
2015 Vol. 33 (10): 915-920 [Abstract] ( 1690 ) [HTML 1KB] [ PDF 1559KB] ( 888 )
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