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Journal of Drainage and Irrigation Machinery Engin
 
2013 Vol.31 Issue.8
Published 2013-08-25

article
Article
645 Production parameter configuring method for screw pumps with surface-driving
Zhang Guodong, Li Mingzhong, Xue Jianquan, Wang Lei, Yue Guangtao
In order to optimally configure the production parameters of screw pump well and match well with pump, based on screw pump′s temperature field and pressure distribution law of internal liquid, with stator working conditions and pump lifting characteristics, a program checking method for screw pump well with surface-driving was established and a program checking plate was drawn, which divi-ded the production plan into reasonable program zone, pump burning region and pump breakdown area. By calculating and analyzing those parameters of two real oil wells, a production parameter optimizing method combining efficient point and system efficiency curve was proposed. The results show that high rotation speed and pump setting depth can increase stator temperature, improve lifting height, which will cause pump burn out or breakdown when they reach critical values. In order to avoid pump burning region and pump breakdown area and extend pump inspection cycle, improve economic efficiency, the optimal production parameter must be attained in field applications.
2013 Vol. 31 (8): 645-650 [Abstract] ( 1564 ) [HTML 1KB] [ PDF 1551KB] ( 1304 )
651 Influence on performance of submersible well pump changing clearance of wear-rings
Shi Weidong, Gao Xiongfa, Zhang Desheng, Lu Weigang, Zhang Qihua, Zhang Xiao
The whole flow field of the submersible well pump 200QJ80-22 was numerically simulated with CFD. By comparing the calculation results with experimental results, the influence of clearance of wear-rings on the external characteristic and internal flow field was analyzed. The results of the nume-rical simulation shows that the head and efficiency of the pump decrease as the size of clearance increases. Especially, when the size of clearance reaches 0.7 mm, the decreasing becomes very obvious yet the pump power almost remains constant; when the size of the clearance reaches 1.00 mm, the efficiency decreases from the highest point of 77.2% to 68.7%, and the head of pump decreases by about 3.5 m; when the size of clearance is 0.2 mm, reverse-flow will appear in the front shroud cavity of the first stage impeller and second stage impeller and in the area between the impeller outlet and the front shroud, which has a small influence on the flow of the impeller inlet and flow field, because there is little leakage flow; reverse-flow gradually disappears when the size of clearance increases to 0.5 mm, but more leakage flow could impact on the impeller inlet, which results in the area of passage of impeller inlet decreasing, and thus seriously affecting the hydraulic performance of the pump.
2013 Vol. 31 (8): 651-655 [Abstract] ( 2374 ) [HTML 1KB] [ PDF 1963KB] ( 1475 )
656 Accurate calculation of backlash flow in external gear pump
Li Yulong
To overcome the limitations of the available methods used for accurate calculation of backlash flow rate in external gear pumps, firstly by accurate analysis of tooth-profile near the minimum backlash position, together with meshing position variable and offset variable from theoretic meshing line, the formula to calculate length and height related to gap near the minimum backlash position was derived. And then, the corresponding backlash flow rates in a trapped-oil cycle were calculated by a variety of methods based on equivalent tooth-profile and actual tooth-profile. Under the same pressure difference, all results indicate that backlash flow rate is minimum in the beginning of trapped-oil section and is maximum in the end of trapped-oil section. The equivalent tooth-profile method can be used to calculate the backlash flow rate in the compression section of trapped-oil while cannot be used in the expansion section. The orifice flow theory is not suitable for calculation of backlash flow rate, especially at the termination of trapped-oil section, the bigger backlash value, or the higher pressure difference. The longest length of gap in backlash is readily unchanged at all meshing positions. Different meshing positions have little effects on gap value under a given offset. Finally, the important conclusion is that the popular equivalent tooth-profile method and the theory of thin-walled orifice are unsuitable for the backlash flow rate calculation.
2013 Vol. 31 (8): 656-661 [Abstract] ( 2862 ) [HTML 1KB] [ PDF 1831KB] ( 1614 )
662 Influence of increments of back sealing ring diameter of impeller on characteristic of axial force
Liu Zailun,, Li Zhenhua, Wu Jiao, Zeng Jilai
Reducing the axial force is an important way to improve the service life and efficiency as well as to get higher lift of submersible pumps. With water as the medium, standard k-ε turbulence model in multiple reference frames was used to simulate the whole flow field for unsteady incompre-ssible flow in the 300QJ230-40/2 submersible pump. The overall performance and axial force were numerically obtained, and the simulated performance curves as well as axial force against head were drawn. Mechanical metrical method for axial force was used in the test, and the simulated curves were compared with the test curves of both performance and axial force. The results show that these curves are close to each other under working conditions from 0.8 Qsp to 1.2 Qsp(heads from 46 m to 36 m). With the front sealing ring diameter increment of Δrm≠0, the diameter and number of balance holes of the impeller of constant, numerical calculations and analysis for both the whole flow filed and axial force were conducted, and the results show that the axial force could be effectively reduced by increa-sing the back sealing ring diameter of the impeller.In order to find the way of prediction and evaluation of axial force on similar-designed pumps, dimensionless curves of axial force coefficient and specific area were drawn.
2013 Vol. 31 (8): 662-666 [Abstract] ( 2082 ) [HTML 1KB] [ PDF 2207KB] ( 1030 )
667 Effect of tip clearance on unsteady flow in axial-flow pump
Li Yaojun, Shen Jinfeng, Hong Yiping, Tang Xuelin, Zhang Zhimin
In order to study the influence of the tip clearance on the unsteady flow and performance of the axial-flow pump, adopting the Spalart-Allmaras model based detached eddy simulation(DES)method and sliding mesh technique, numerical simulations of internal turbine flow of the axial-flow pump under designed conditions were carried out. The internal unsteady flow and its pressure pulsations of four different tip clearance sizes were simulated and analyzed. With the designed tip clearance, the predicted pump head and efficiency matched well with the measured data, and the maximum relative errors were less than 2.0% and 3.0%, respectively. The numerical results show that the pump performance, especially the head and efficiency tend to decrease as tip clearance becomes bigger; the intensity and range of the tip clearance vortex increase as the tip gap grows. When the gap reaches 3.3‰D2, the tip clearance vortex expands to the trailing edge of the neighboring blade. The results also show that the blade passing frequency dominated the pressure fluctuations in the impeller. The increase of the blade tip gap led to a reduction of the maximum pressure fluctuation amplitude on the front part of the impeller casing, but an increase on the middle part of the impeller casing. Pressure fluctuations in the impeller-vane gap region are dominated by the blade passing frequency(fn), while the maximum pressure fluctuation amplitude was observed to decrease as the tip clearance size increases. 
2013 Vol. 31 (8): 667-673 [Abstract] ( 2145 ) [HTML 1KB] [ PDF 3279KB] ( 1197 )
674 Researching status of centrifugal pump as turbine
Wang Tao,, Kong Fanyu, He Yuyang, Yang Sunsheng
PAT(pumps as turbines)is one of the best alternatives for energy recovery. PAT is very important for waste energy resources recovery in industry and the micro-hydropower development in remote areas. In order to further investigation on PAT, the main texts on PAT were briefly reviewed. The available reference materials of research on pumps worked as turbines were mainly conducted based on experimental, theoretical and numerical ways. The relevant research fields of PAT were summarized, such as the optimization design of flow passage components in PAT and performance improvement, the operational stability of PAT, PAT′s type-selection and performance prediction, especially the prediction for BEP(best efficiency point). Performance parameters of the pumps and PAT were obtained through experiments. The relationship of performance parameters between pumps and PAT was predicted by theoretical analysis and the empirical formulas based on the experimental data. The PAT performance can be determined by comparing the results from CFD prediction and the tests. Finally, the prospect and future tendency of research on PAT was proposed, in which the accurate method of PAT type selection, the new design theory, vibration and off-design operational stability as well as the high-power and multistage PAT study were included.
2013 Vol. 31 (8): 674-680 [Abstract] ( 2604 ) [HTML 1KB] [ PDF 1577KB] ( 1543 )
681 Hydraulic design of giant-scale Francis turbine in Xiluodu hydropower plant
Wang Zhaoning,, Guo Pengcheng, Luo Xingqi, Wang Yalin
According to high water head, large head variation and 770 MW unit capacity, a study of hydraulic design of the giant Francis turbine units in the Xiluodu hydropower plant was carried out. From the view of hydraulic stability control, the hydraulic design condition was discussed. The selecting principle and matching relationship of four key hydraulic parameters including rated speed, unit discharge, unit speed, design head as well as two important geometric parameters covering guide vane relative height and diameter ratio of the runner inlet and outlet, were demonstrated. The possible stability problems induced by different hydraulic design parameters were analyzed by comparing different preliminary design schemes, and the viewpoint of selecting low hydraulic design parameters in developing giant Francis turbine was emphasized. The results show that increasing design head can improve the vortex flow characteristics in the runner channel at the high head part load operating region, and can make the incipient cavitation at the suction surface of the blade inlet side far away from the operation region of the hydraulic turbine. Finally, it has been proved that the hydraulic design adopted has practical engineering values by the model acceptance test.
2013 Vol. 31 (8): 681-687 [Abstract] ( 2111 ) [HTML 1KB] [ PDF 1382KB] ( 2150 )
688 Optimization of cost per day of cascade pumping station water-delivery system
Sang Guoqing,, Cao Shengle, Guo Rui, Zhang Lin
In order to improve the daily operation efficiency of cascade pumping station, through analyzing the cascade pumping station water delivery operation system, the concept and expression of the pumping station operation efficiency was proposed; and the influencing factors of daily operation costs and optimizing mechanism was analyzed. Based on the above researches, aiming at minimizing the daily operation costs, taking restricting conditions, such as time-of-use electricity price, water amount, and water level of intake and outlet pools, into consideration, a daily operation cost optimization model for cascade pumping station water delivery operation system, an efficiency optimization model of cascade pumping station water delivery operation system and an efficiency optimization model of single grade pumping station were established. Based on discrete intervals, adopting dynamic programming method, a daily economic optimization operation scheme for cascade pumping station water delivery system was determined, including inter-stage hydraulic(water level, water flow)plans and internal operation plans for all pumping stations. This method was applied to the optimization of Hanzhuang cascade pumping station water delivery system, which had greatly reduced the costs.

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2013 Vol. 31 (8): 688-695 [Abstract] ( 2065 ) [HTML 1KB] [ PDF 1515KB] ( 1246 )
696 LES analyses of flow fields and structure improvements of hydrocyclones
Guo Xueyan, Wang Binjie, Yang Fan
LES(large eddy simulation)analysis has been carried out to investigate the flow fields in a hydrocyclone. Detailed flow structures and phenomena such as shortcut flow, internal circulations, locus of zero vertical velocity(LZVV)and locus of maximum tangential velocity(LMTV), have been analyzed. Combined with theories of hydrocyclone design and fluid mechanics, modification of the internal structures was conducted, including increasing thickness of overflow pipe wall,increasing depth of overflow tube insertion, appropriately increasing length of the hydrocyclone cylinder, decreasing taper angle etc. The further LES analysis shows that thicker overflow pipe wall can effectively restrain the circulation flow near the overflow pipe; but deeper overflow tube does not obviously hamper the short-circuit flow. Longer overflow tube with appropriate cone angle can determine a better LZVV and LMTV. Compared with the original cyclone, the flow fields in the modified one are obviously improved, which implies that a better liquid-solid separation can be expected.
2013 Vol. 31 (8): 696-701 [Abstract] ( 1738 ) [HTML 1KB] [ PDF 2402KB] ( 1709 )
702 Large eddy simulation of turbulent flow around moving guide vane of adjusting hydro turbine
Huang Jianfeng, Zhang Lixiang, Guo Yakun
To investigate transient hydraulic process of upstream duct system and hydro turbine, based on the incompressible viscous Navier-Stokes equations and immersed boundary method(IBM)for moving boundary, using the dynamical subgrid stresses(SGS)on Smagorinsky-Lilly model in large eddy simulation(LES), a delicate numerical simulation of three dimensional turbulent flow around one moving guide vane of a benchmark hydro turbine unit in a channel was conducted. The distributions of the pressure and the topological structures of wake were well captured as closure of the vane. The production and evolution of the wake vortices passing the kinetic guide vane was clearly shown, and the physics of the structures were analyzed. The results show that the flow around a moving guide vane will produce numerous complex transient structure which induces water hammer of upstream duct system and transient behavior of downstream runner passage. The numerical results show that the numerical method of LES-IBM with dynamical Smagorinsky-Lilly SGS model can be used to well simulate the interaction between high Reynolds number turbulent flow with motion of the vane closure, revealing the mechanism evolution properties of the wake to the downstream in the hydro turbine adjustment process. 
2013 Vol. 31 (8): 702-707 [Abstract] ( 1940 ) [HTML 1KB] [ PDF 2969KB] ( 1287 )
708 Structural design and performance research of seven-channel spherical check valve
Zhao Fei, Fu Jie, Song Wenwu, Wang Chunzhi
A seven-channel spherical check valve was designed to solve the prevailing problem and to overcome disadvantages of check valves for DN≥200 mm piping system. UG software was used to establish the model of the seven-channel spherical check valve. By using CFD technique, the internal flow of the seven-channel spherical check valve was numerically simulated. On the same water hammer test rig, the water hammers and hydraulic losses of spherical and swing check valves were tested and compared. The results show that the maximum water hammer pressure of the seven-channel spherical check valve is only half of the swing check valve, the closing time of the former is double of the latter, with the same diameter for hard shutdown condition of the pump. In the same throughout flow condition, the hydraulic loss of the former is only 10% of the latter.
2013 Vol. 31 (8): 708-712 [Abstract] ( 1970 ) [HTML 1KB] [ PDF 1540KB] ( 1370 )
713 Dielectric properties of Lou soil and moisture content detection affected by frequency and temperature
Guo Wenchuan,, Zhang Peng, Song Kexin, Han Wenting,, Xu Jinghui
To determine reasonable detecting frequency for developing soil′s moisture sensor based on dielectric properties and to reduce influence of temperature on permittivities, Lou soil in Guanzhong Plain, Shaanxi Province, was used to study the influence of frequency(10-4 500 MHz), moisture content(9%-25%)and temperature(5-50 ℃)on relative dielectric constant and dielectric loss factor by network analyzer and coaxial-line probe technology. The reasons why permittivities changed with these factors were analyzed, and the frequency-, moisture content- and temperature-dependent penetration depth was determined. The results show that with the increasing of frequency from 10 MHz to 4 500 MHz, the relative dielectric constant decreases, while the dielectric loss factor changes from increasing to decreasing then to increasing. Both dielectric constant and loss factor increase with increasing moisture content and temperature over the detected ranges. The penetration depth decreases with increasing frequency, moisture content and temperature. Frequency, moisture content and temperature are major factors which influence dielectric permittivities and penetration depth of soil. The study indicates that the reasonable frequencies for detecting moisture content of soil based on dielectric properties are over the frequency range from 50 MHz to 100 MHz.
2013 Vol. 31 (8): 713-718 [Abstract] ( 1708 ) [HTML 1KB] [ PDF 3497KB] ( 1383 )
719 Numerical simulation and structural optimization of screen filter in micro-irrigation
Wang Xinkun, Gao Shikai, Xia Liping, Xu Peng
The research of micro-irrigation screen filter was mainly concentrated in hydraulic perfor-mance test. Computational fluid dynamics software Fluent 6.3 was adopted to simulate the flow and ana-lyze the hydraulic performance of a 2 inches AZUD micro-irrigation screen filter. The screen was predigested as a porous media, and the models were built by 3D software Pro/E. Results show that the si-mulated results and experiment results agree well with each other. The maximum relative deviation was 8%, and averaged relative deviation was 4.4%. The filter internal flow distribution, the balance of screen velocity distribution and the filter life have been improved by optimizing inlet and outlet location, inlet and outlet angle and filter shapes under the same filter area and inlet diameter. Optimization results show that the head loss is reduced by 69% and the maximum speed difference between both sides on screen filter surface is decreased from 1.0 m/s to 0.1 m/s.
2013 Vol. 31 (8): 719-723 [Abstract] ( 1931 ) [HTML 1KB] [ PDF 1512KB] ( 1328 )
724 Experimental investigation on cavitation characteristics of Venturi injector
Yan Haijun, Chen Yan, Xu Yuncheng, Wang Zhipeng
In Venturi injector, the critical cavitation caused by large pressure difference will result in poor fertigation uniformity. Experimental investigation was conducted to study the cavitation phenomenon of DN25 Venturi injector. For seven different inlet pressure values, the changes of suction flow rate were measured under different pressure differences between inlet and outlet. The strain values on the enternal surface of throat and diffusion portions were detected by dynamics strain indicator. Stan-dard deviations of the strain values were calculated to analyze the relationship between the suction flow rate and the internal characteristics of the cavitating flow. The results show that critical cavitation occurs in Venturi injector when inlet pressure is below 0.20 MPa. As inlet pressure exceeds 0.20 MPa, the critical maximum pressure difference has linear relationship with inlet pressure, and critical cavitation occurs in Venturi injector. When inlet pressure is larger than the critical maximum pressure diffe-rence, the variation curves of strain standard deviation versus pressure difference appear to be “M”, where three inflection points of “M” are linear with inlet pressure, respectively.
2013 Vol. 31 (8): 724-728 [Abstract] ( 2350 ) [HTML 1KB] [ PDF 1553KB] ( 1160 )
729 Simulation of effect of water-saving renovation on spatial distribution of groundwater in Jinghui Canal irrigation area
Dai Fenggang,, Cai Huanjie, Liu Xuan, Liang Hongwei
In order to evaluate objectively environment impact of water saving renovation on groundwater and figure out a reasonable agricultural water saving scheme and a rational development and utilization mode of groundwater in Jinghui Canal irrigation area, by integrally applying GMS and ArcGIS software, a groundwater distribution model was built. Combining water-saving irrigation canal lining with farmland water saving and agricultural planting structure, eight assumed scenes and actual scenes are used to analyze the effect of water saving renovation on spatial distribution of groundwater. The results show that field water saving engineering can help reduce well irrigation water of 18.5%~33.4% and is very effective in alleviating groundwater level′s falling. Through canal system water saving enginee-ring, water use coefficient is increased by 16.9%, next to which is the role of reducing groundwater exploitation. In Jingyang, Yangfu, Loudi and Zhangbu, the agricultural planting structure and spatial distribution of soil and water resources do not work well together, which offsets the water-saving renovation effect of slowing down the fall of ground water levels, which inevitably led to the increasing trend of groundwater drop funnel. It is recommended that the artificial groundwater regulation and storage, the perfection of groundwater exploitation permit system and the adjustment of agricultural planting structure, could help achieve the sustainable use of the water resources and the sustainable development of water-saving agriculture in the irrigation area.
2013 Vol. 31 (8): 729-736 [Abstract] ( 1593 ) [HTML 1KB] [ PDF 3909KB] ( 1198 )
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