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Journal of Drainage and Irrigation Machinery Engin
 
2016 Vol.34 Issue.9
Published 2016-09-25
737
2016 Vol. 34 (9): 737-741 [Abstract] ( 712 ) [HTML 1KB] [ PDF 2521KB] ( 751 )
742 Effects of blade wrap angle on performance of high specific speed centrifugal pump
HUANG Xi, YUAN Shouqi, ZHANG Jinfeng, ZHANG Xia
In order to investigate the influence of blade wrap angle on high specific speed centrifugal pump performance under design condition, a single-stage, end-suction centrifugal pump with a specific speed of 185 is taken as study object. Firstly, five impellers respectively with 110°, 115°, 120°, 125°and 130° wrap angles are designed when the rest geometric parameters remain unchanged, then the flow fields in the pump with these impellers are calculated numerically by using software ANSYS CFX 14.5. The results show that the blade wrap angle has a significant impact on external characteristics. If the wrap angle is oversized, the head and the hydraulic efficiency will decline. When the wrap angle increases to 130°, the best efficiency point migrates about 20% to part-load region; in addition, the low pressure zone at the impeller inlet is enlarged with increasing wrap angle, leading to cavitation more easily. When the wrap angle increases from 110° to 115°, the flow in the volute is smoother. However, when the angle is 125°, an obvious vortex region with low velocity appears around the tongue, further it is expanded and moves to the impeller outlet gradually with increasing warp angle. Also, when the wrap angle reaches to 120°, the pressure fluctuation amplitude at every monitoring point is relatively low, showing there is an optimal wrap angle for rotor-stator interaction. The performance of the pump with 120° wrap angle is measured and it is found that the results of numerical simulation are in agreement with the measurements. This study has provided some reference significance to the development of a high specific speed centrifugal pumps with better performance.
2016 Vol. 34 (9): 742-747 [Abstract] ( 1493 ) [HTML 1KB] [ PDF 2240KB] ( 1549 )
748 Numerical calculation of influence of gap between impeller shroud and diffuser side wall on performance of reactor coolant pump
CHENG Xiaorui,, BAO Wenrui
The numerical simulations of flow of water in AP1000 reactor coolant pump model are performed based on the Reynolds averaged N-S equations and RNG k-ε turbulence model by using SIMPLE algorithm. Firstly, the size of the gap between the impeller shroud and the diffuser side wall is designed with four values. Secondly, the flow field in the pumps with these sizes are simulated. Finally, the axial thrust and flow structures in the gap and collector are obtained and discussed under various gap sizes. The results show that the gap size has a certain impact on the pump head and efficiency in a range of 0.8Qd-1.2Qd flow rate. The change in gap size can cause a shift of best efficiency point from the design point, but the shift scale and direction do not correlate with the gap size evidently. Under the design condition, the pump efficiency at 0.6 mm gap is better than the others, and increased by 1.66% compared with 1.8mm gap. Under 1.2Qd flow condition, the pump is more efficient at 1.8 mm gap than at other gaps, and the pump efficiency is improved by 2.17% compared with 2.4 mm gap. Under all working conditions, the gap size has less influence on the axial thrust which shows a monotonic decreasing trend as the flow rate increases. The analytical axial thrust is much lower than the tested value obviously. But with increasing flow rate, the analytical axial thrust approaches the measurement.
2016 Vol. 34 (9): 748-754 [Abstract] ( 976 ) [HTML 1KB] [ PDF 2482KB] ( 1062 )
755 Hydraulic optimization and performance test of super low-specific-speed multistage centrifugal pump
MA Xinhua, HE Yongguan, LU Weigang, CAI Pengfei
In order to improve the hydraulic performance of existing super low-specific-speed multistage centrifugal pumps, based on ANSYS CFX, the whole flow field of a series of multistage centrifugal pumps is simulated. The energy conversion efficiency and hydraulic loss in the impeller, casing and diffuser are analyzed by defining the head and efficiency for each of them. As a result, the primary factor affecting the performance of the multistage centrifugal pump is identified to be the matching between impeller and diffuser, and the secondary factor is the flow loss in the impeller. It is proposed that the throat area of diffuser should be calculated by making use half magnitude of the absolute velocity at the impeller outlet, the designed diffuser is optimized step by step and the vortex in the impeller is eliminated by adjusting the impeller blade profile. The fluid velocity in the impeller and optimal diffuser varies uniformly and slowly, reducing the flow loss significantly. The optimized pump is manufactured, tested and compared with the original one. It is shown that the head and efficiency are significantly improved by 8.1 m and 3.2%, respectively, meeting the requirements in the national pump standard. The method in which the simulated results are compared with the measurements and then the differences between them are analyzed can provide a reference for hydraulic performance optimization of a super low-specific-speed multistage centrifugal pump. 
2016 Vol. 34 (9): 755-760 [Abstract] ( 1115 ) [HTML 1KB] [ PDF 2538KB] ( 1404 )
761 Design and experiment on driving power supply for drip irrigation piezoelectric pump
SUN Fuchun, HU Caiqi, LI Shengduo, HU Xiaoqi, LI Jie, JI Jing
According to the requirement on driving power supply by a drip irrigation piezoelectric pump, a switch driving power supply is designed in this paper based on the EG8010 inverter chip by adopting single phase bridge voltage inverter, rectifier circuit and SPWM control sine wave generator chip. Firstly, the structure and working principle of driving power supply are proposed for drip irrigation piezoelectric pumps. Secondly, a single phase sine wave with continuously adjustable excitation voltage and frequency is formed by using the corresponding control regulation circuit. Then the output voltage feedback and regulation circuits, frequency control circuit and temperature monitor circuit are designed with hardware. At last, an experiment is carried out based on the single phase sine wave which will be used as an excitation source of drip irrigation piezoelectric pump. The results show that this driving power supply has a few advantages, namely dead time control equipped, high stability, low waveform distortion, simple structure, small volume, convenient operation, low cost and etc. compared with the traditional driving power supply unit which is composed of a signal generator and a power amplifier, and it can meet the requirement on driving and control by a drip irrigation piezoelectric pump.
2016 Vol. 34 (9): 761-766 [Abstract] ( 1030 ) [HTML 1KB] [ PDF 2392KB] ( 1142 )
767 Structural features of bulb tubular pumps in first phase of South-to-North Water Diversion Eastern Route Project in China
ZHANG Rentian,, SHAN Haichun, BU Ge, ZHOU Wei, ZHU Honggeng, YAO Linbi
According to the blade regulation method and power transmission mode, the structure of bulb tubular pumps installed in the first phase of South-to-North Water Diversion Eastern Route Project in China can be classified into four kinds, i.e. compact structure with variable frequency drives(VFD)(type Ⅰ), dismountable structure with VFD(type Ⅱ), dismountable structure with gearbox power transmission chain and mechanical blade regulation mechanism(type Ⅲ), and dismountable structure with hydraulic blade regulation mechanism(type Ⅳ). Based on the blade regulation method, pump operational condition adjusting approach and power transmission chain, the major advantages and disadvantages of these structures are analyzed qualitatively and quantitatively. The result shows that even though all the four kinds of pump structure are safe and reliable, in which the maximum deformation of type Ⅳ is about 0.2 mm and the deformation differences between various locations is less than 0.1 mm under the positive and negative peak axial thrust conditions, there are some notable differences in the structure features. For instance, the weight of type Ⅳ unit is 225 t, about three times type Ⅰ. Compared with the mechanical blade regulation method, the structure with VFD is simple, but also a cylindrical hub can be adopted in the pumps, so that the pump efficiency can be improved by over 1.6%.
2016 Vol. 34 (9): 767-775 [Abstract] ( 1113 ) [HTML 1KB] [ PDF 4919KB] ( 1131 )
776 Numerical analysis and prediction of hydraulic performance of vertical axial-flow pump system model
WANG Lihui, SHI Wei, SHEN Changrong, XU Lei
Relying on the design parameters of a low head pumping station in the first phase of east route in the South-to-North Water Diversion Project, the flow in a low head vertical flow pump system model, which consists of an elbow inlet channel, axial flow pump itself and siphon outlet conduit, is simulated based on the steady, 3D, turbulent, Reynolds averaged N-S equations and RNG k-ε turbulence model. The flow pattern in the model and the pressure distribution on the impeller blade surfaces are analysed under three typical conditions, namely, small discharge(0.180 m3/s), design discharge(0.299 m3/s)and large discharge(0.360 m3/s). The hydraulic performance of the pump model is predicted and compared with the test result. The results indicate that the numerical results are basically consistent with the test data, especially at the best efficiency point, and the maximum error is less than 2% within the flow rate interested. Under design flow condition, the 3D turbulent flows in the inlet and outlet conduits are basically the same as the flows in the inlet and outlet conduits when they are simulated separately. The flow fields in the inlet conduit remain the same under different operating conditions, but these in the outlet conduit don′t. Nonetheless, in the paper, the outcomes in 3D turbulent flow in the vertical axial flow pump system model under different operating conditions can provide a reference for the study on optimum hydraulic design of a low-head pump system under multi-operation condition.
2016 Vol. 34 (9): 776-782 [Abstract] ( 1117 ) [HTML 1KB] [ PDF 4796KB] ( 1219 )
783 Analytical method for liquid film mechanical seals based on theory of narrow spiral groove with end effect modification
SONG Pengyun, CHEN Guo
In the design of upstream pumping mechanical seal with spiral grooves, the end effect in which a pressure loss occurs at the inlet of spiral grooves when the liquid is pumped into the grooves is not taken into account, causing in a significant deviation in analytical prediction from experimental observation. In order to predict the performance of a mechanical seal accurately and efficiently by an analytical method, the end effect is considered, i.e. the pressure at the spiral groove root is modified in this paper. The modified analytical expressions of liquid film pressure and opening force are obtained. The opening force is compared with the force obtained by the analytical method without end effect or with experiment or based on numerical simulation. The opening force with end effect is consistent with the experimental measurement and the numerical prediction. Compared with the numerical simulation, the mean and maximum errors in opening force are 1.9% and 6.2%, respectively, under a low pressure difference condition; compared with experimental data, however, these error increase to 8.6% and 15.5%. The averaged and maximum errors in opening force are 1.9% and 2.5% compared with numerical simulation under a high pressure difference condition. The results can provide a reference for the investigation, design and application of upstream pumping mechanical seals.
2016 Vol. 34 (9): 783-789 [Abstract] ( 1044 ) [HTML 1KB] [ PDF 1602KB] ( 1099 )
790 Analysis of aerodynamic characteristics of a horizontal axis wind turbine at different pitch angles
YIN Rui, WANG Wenquan, YAN Yan
The blade is a key component of wind turbines for capturing wind energy, and also affects the overall operating performance directly. In this paper, the aerodynamic characteristics of a small household horizontal axis wind turbine are studied. At first, a three-dimensional geometrical model of that turbine is constructed with UG software. Then, the finite volume method is used to discretize the Navier-Stokes equation and the k-ω SST turbulence model equations, and the second-order upwind scheme and the second-order central difference scheme are applied to the convection and diffusion terms, respectively, SIMPLE is used for the coupling between velocity and pressure. Finally, the aerodynamic characteristics such as power efficiency, moment as well as axial thrust are discussed at different pitch angles. The power and torque coefficients increase firstly and then decrease with increasing tip speed ratio. The maximum power and moment coefficients increase firstly and then decrease with increasing pitch angle, but the maximum axial thrust coefficient gradually reduces with increasing pitch angle. At the same time, the streamlines at different pitch angles are shown and analyzed. Hopefully, the results can provide a reference and guidance for optimization design of horizontal axis wind turbine.
2016 Vol. 34 (9): 790-794 [Abstract] ( 974 ) [HTML 1KB] [ PDF 2284KB] ( 1493 )
795 Light response and photosynthetic physiology characteristics of coffea arabica L. leaf at different irrigation and light intensity levels
WAN Mengdan, LIU Xiaogang, XU Hang, WU Hao, QI Yuntao, WANG Lu, YANG Qiliang
To explore coupled management mode of water and light intensity for tropical economic crop-coffea arabica L. tree, the effects of irrigation and light intensity levels on light response curve, photosynthetic, transpiration, stomatal conductance and others indexes are studied on coffea arabica L. leaf by using three levels of irrigation(WH-high water content level, WM-moderate level, WL-low water)and three levels of light intensity(S0-no shading, S1-slight shading, S2-severe shading). The results show that the effects of shading on the chlorophyll content and carotenoid pigment in coffea arabica L leaf are greater than those of irrigation. Compared with no shading, an increased shading intensity can raise the total chlorophyll and chlorophyll b by 13. 53%-260. 21% and 31.10%-412.91%, respectively. Compared with the low water content level, an increased irrigation level can increase the chlorophyll a, and b, total chlorophyll by 13.30%-110.65%, 92.11%-148.36% and 39.85%-124.30%, respectively, under non-shading and slight shading conditions. Compared with the low water content level, an increased irrigation level can increase the maximum net photosynthetic rate under no shading and slight shading conditions; under severe shading condition, however, the maximum net photosynthetic rate on longer increases with the increasing irrigation level steadily. Compared with the low water level, the increased shading degree can increase the maximum net photosynthetic rate by 10.73%-103.73%. The diurnal variations of net photosynthetic rate, transpiration rate and stomatal conductance all exhibit a double-peak curve under different irrigation and light intensity conditions. Compared with the no shading case, the increased shading degree can increase the net photosynthetic rate and stomatal conductance by 12.36%-57.4% and 4.56%-42.66%, respectively, unfortunately the daily transportation rate is deduced significantly. Compared with the low water level case, an increased irrigation level can substantially increase the average stomatal conductance and net photosynthetic rate. The highest water and light use efficiencies and the maximum net photosynthetic rate are achieved at a high water level and under slight shading condition. Thus the combination S1WH is the best for efficient use of water and light for coffea arabica L. leaf.
2016 Vol. 34 (9): 795-803 [Abstract] ( 931 ) [HTML 1KB] [ PDF 1728KB] ( 1060 )
804 Advances in research on compensation effects of crops under drought stress
LIU Zhanpeng,CHU Linlin
Drought is one of the common environmental stresses in crop growth environment. After a certain range of drought stress, in a short-term rewatering, a positive effect of compensation or over compensation effect can be prouduced by crops in physiological and biochemical metabolism and growth to make up the damage and loss caused by drought during the drought. Compensation effect is an important regulation mechanism for crops to resist a stress, but also is the main physiological basis for crops to control water content effectively and to realize the water saving and high efficiency agriculture. The growth compensation, physological and biochemical compensations, metabolism and yeild compensations and their inflencing factors are reviewd in the paper. On the basis, three research issues are put forward for the future, i.e. compensation mechanism agronomy and physiological index in drought stress and rewatering, compensation and feedback mechanism of photosynthesis, and benefit evaluation of compensation effect after water stress. The paper has important theoretical and practical significance for improving and enriching the theory of biological water saving, guiding the management of agricultural efficient water use, developing water-saving irrigation and providing crop water productivity.
2016 Vol. 34 (9): 804-808 [Abstract] ( 956 ) [HTML 1KB] [ PDF 1283KB] ( 1258 )
809 Application of entropy weight fuzzy matter element model in comprehensive benefit evaluation of water saving irrigation
XIAO Junlong, LIU Yongqiang, TIAN Lang , CAO Ruizhe
In view of shortcomings in multiple simple index comprehensive evaluation methods in comprehensive benefit evaluation of water saving irrigation in the past, an entropy weight method is used to determine weight of each evaluation index, and a matter element extension model based on the entropy weights is established to evaluate the comprehensive benefits of water saving irrigation in irrigation districts. An evaluation index system is developed by taking three aspects such as social, economic and ecological benefits into consideration. Four irrigation districts in Ji'an are evaluated with the above method and models. The results show that the comprehensive benefit level is fair in the Yinwan Bridge irrigation district, but the benefit levels are becoming fair, good and fine in the Tiannan, Guko and Nanche irrigation district, respectively. The stability of the results is verified by sensitivity analysis method. The study shows that the entropy weight analysis method has a certain application significance in the comprehensive benefit evaluation of water saving irrigation. 
2016 Vol. 34 (9): 809-814 [Abstract] ( 996 ) [HTML 1KB] [ PDF 1298KB] ( 1186 )
815 Effects of irrigation level and frequency on growth and water use efficiency of maize
TIAN Jianke,, ZHANG Fucang,, QIANG Shengcai,, ZOU Haiyang,, WU You,, YAN Shicheng,
In order to explore effects of irrigation level and frequency on growth, yields and water use efficiency of maize(Zhengdan-958), pot cultivating experiments are conducted in a rain shelter by using nine cases which include three irrigation levels(W1, W2, and W3 for 120%, 100%, and 80% ETc)and three frequencies(D1, D2, and D3 for 3 d, 6 d and 9 d intervals). Various growth indices of maize plants are observed and analyzed during their growth periods in the experiments. The results show that the plant height, leaf area, dry weight and yield rise with increasing irrigation level, but decrease with increasing irrigation frequency. Significance analysis indicates that irrigation level affects plant growth and yield more substantially than irrigation frequency does. The maximum maize yield per plant is achieved in case W1D3, while the minimum yield is obtained in case W3D1, showing a significant difference. Furthermore, both water use efficiency and irrigation water use efficiency increase initially and then decrease with increasing irrigation level, but they decrease steadily with increasing irrigation frequency. The water use efficiency and irrigation water use efficiency are the best in case W2D3, reaching 1.83 kg/m3 and 1.61 kg/m3, respectively. Overall, case W1D3(120%ETc, 9 d intervals)can be a more feasible irrigation proposal under the present experimental conditions. 
2016 Vol. 34 (9): 815-822 [Abstract] ( 1060 ) [HTML 1KB] [ PDF 1527KB] ( 1158 )
823 WinSRFR software-based optimization of horizontal border patch size in Hetao irrigation district
BAI Yinzhen, WEI Zhanmin, ZHANG Jian, GAO Hongyan,, WEI Zihan
In order to improve the quality of land resources and irrigation in the Hetao irrigation district, the size of the present border patch in a district is optimized based on measured water advance and recession data of horizontal border irrigation by using numerical and analytical methods. The irrigation quality index is calculated by using water balance method and calibrated by employing zero inertia model based on the design function of winSRFR software system and the field irrigation factors. The contours of irrigation quality index are obtained, the optimal ranges that meet the irrigation requirements and with good irrigation quality are determined. Typical patch layouts are put forward by considering the status of land ownership and land size, namely, layout 1: a patch with 102 m length, 65-95 m wide and 6 670-10 005 m2 area by merging border, ditch and border, layout 2: a patch with 154 m length, 65-110 m wide and 10 005-16 675 m2 area by combining border, ditch, border road and border.
2016 Vol. 34 (9): 823-828 [Abstract] ( 821 ) [HTML 1KB] [ PDF 3296KB] ( 984 )
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