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Journal of Drainage and Irrigation Machinery Engin
 
2017 Vol.35 Issue.2
Published 2017-02-25

93 Effects of diffuser installation position on pressure fluctuation in the mixed flow pump
GU Yandong, YUAN Shouqi, PEI Ji, LIU Yong, CAO Jian
In order to investigate the effects of diffuser installation position on the hydraulic performance, pressure fluctuation characteristics in the mixed flow pump, eight schemes(C0-C7)of different diffuser installation position are analysed through steady and unsteady simulations by using ANSYS CFX 14.5. Through grid independency analysis, the predicted results of the original scheme C0 has a good agreement with the experimental performance, thus the numerical simulation is reliable. The results show that the diffuser installation position almost has no effects on the head but influences the hydraulic efficiency obviously, and the head of each scheme reaches the design requirement. The hydraulic efficiency of C2 is the largest but that of C7 is the smallest, whose difference is about 2.6%. Each scheme has the same main activating frequency, three times blade passing frequency, but its amplitude is different, the amplitude of C7 is the largest and those of C0 and C2 are similar. Besides, the pressure fluctuation is weakened along the discharge pipe. The pressure fluctuation intensity varies evidently with the change of diffuser installation position, and the maximum in the circular casing occurs near the diffuser leading surface. The pressure fluctuation intensity of C7 is largest, C0 taking the second place, and that of C2 is the smallest. Overall, the diffuser installation position C2 has the optimal performance and pressure fluctuation, which can be a significant reference for installing the diffuser in the mixed flow pump.
2017 Vol. 35 (2): 93-99 [Abstract] ( 942 ) [HTML 1KB] [ PDF 6377KB] ( 748 )
100 Numerical simulation on the flow field and cavitation in a scroll hydraulic pump
SUN Shuaihui,, WU Kai, HUANG Yi, GUO Pengcheng, LUO Xingqi
The computational fluid dynamics(CFD)technique was applied to simulate scroll hydraulic pump. The Schnerr-Sauer model was used to simulate the cavitation phenomena in the pump. The change of the fluid domain was simulated by the dynamic mesh technology with elastic deformation and grid reconstruction. The flow field in the scroll hydraulic pump under 0.5 mm meshing clearance was figured out, and the pressure and velocity at special points were monitored. The results showed that the pressure peak in suction chamber happened at 0° which reached 1.5 MPa. And the high-pressure difference between the external clearance resulted in the high-speed jet flow near the clearance which led to the vortex and cavitation. At the downstream of the clearance, the local area of suction chamber increased due to the movement of orbiting scroll, which generated the vacuum and cavitation. The vortex and cavitation led to the fluctuation of pressure and velocity of regions around, blocked the flow passage, and made the small wave of flow rate diagram. The movement of orbiting scroll and asymmetry of inlet made the difference of pressure, velocity and vortex distribution between the left and right flow passage and suction chamber. Moreover, during the later suction process, the flow in the right flow passage is almost motionless, and the fluid flowed into the right suction chamber mainly through the top flow passage.
2017 Vol. 35 (2): 100-105 [Abstract] ( 1182 ) [HTML 1KB] [ PDF 3222KB] ( 805 )
106 Effect of impeller geometric parameters on characteristics of inlet recirculation in centrifugal pump
LIN Gang, YUAN Jianping, SI Qiaorui, ZHOU Banglun, SUN Wei
In order to study the influence of impeller geometric parameters on inlet recirculation, three-dimensional steady numerical simulations of the flow within a low specific speed centrifugal pump IS65-50-160 were conducted using the standard k-ε turbulence model. The hydraulic performance of the pump was predicted and compared with experimental results. The influences of number of blades, angle of attack and blade leading edge position on the inlet recirculation ware clarified, and the distribution of velocity and streamline under different operational conditions were discussed, too. The results show that the inlet recirculation first occurs near the wall of inlet pipe. The velocity of recirculation flow decreases with the increase of number of blades. The predicted pump head is higher under every condition and there is a weaker recirculation when the number of blades is 7. The recirculation flow velocity from the impeller to the inlet pipe is much low and the streamlines in the impeller channels are distributed evenly at 10° angle of attack, suggesting a suppressed recirculation in the pump. The pump has a better performance and its recirculation zone is decreased when the leading edge is extended further into the impeller eye.
2017 Vol. 35 (2): 106-112 [Abstract] ( 1005 ) [HTML 1KB] [ PDF 2190KB] ( 867 )
113 Effect of unequal spacing blade distribution on pressure fluctuation of self-priming vortex pump
LIU Zhichao, KONG Fanyu, WANG Yang, XIE Shanfeng, ZHAO Lifeng
In order to reduce pressure pulsation amplitude and the noise of vortex pump when the pump is running,three kinds of impeller blades are designed based on the unequal spacing blade distribution, studying the steady-state performance and pressure fluctuation of self-priming vortex pump. Internal radial and axial gap pressure data of self-priming vortex pump is obtained by computing vortex self-priming unsteady flow and the performance of the pump with the RNG k-ε model. The numerical results show that the unequal spacing blade distribution will have a certain effect on the performance of self-priming vortex pump. When the modulation angle is small, that has little effect on the efficiency of the self suction pump. Compared with the equal spacing blades, the pressure distribution of the unequal spacing blades is small. In addition, the unequal spacing blade can effectively reduce pressure pulsation amplitude of the self-priming vortex pump and change pulsating frequency distribution, and changes of modulation angle will affect the pressure fluctuation amplitude.When the modulation angle is 5°,pressure fluctuation amplitude of main frequency declines a lot. The better pressure fluctuation characteristics can be obtained by controlling the modulation angle in the proper range.
2017 Vol. 35 (2): 113-118 [Abstract] ( 1091 ) [HTML 1KB] [ PDF 2204KB] ( 571 )
119 Characteristics of valveless piezoelectric micropump based on logarithmic spiral composite tube
ZHANG Xitong, XU Wei, HE Xiuhua
A new type of logarithmic spiral pipe structure was presented to improve the characteristics of flow resistance in tubes to enhance the performance of the micropump. It is a kind of three-way tube consisting of the converging tube which was traditional diffuser/nozzle elements and the branch tube with the outline of logarithmic spiral. Orthogonal optimization was carried out on converging and branch tubes using the method of numerical simulation to optimize the structure. The results of the numerical simulation were supported by experimental data and the errors were within 20% and 12% respectively for the forward and reverse direction. The findings indicated that the ratio of the resistance through opposite directions of this new pipe was approximately a constant 1.7, which was better than the traditional diffuser/nozzle elements. The micropump with the logarithmic spiral pipe was fabricated and tested. The experimental findings showed that the head and the flow rate had peaks at 225 Hz of frequency and increased with the input voltage amplitude. The micropump could reach the maximum head of 396 mm water column and flow rate of 0.43 mL/min. This new logarithmic spiral pipe can effectively improve the performance of valveless piezoelectric micropump.
2017 Vol. 35 (2): 119-125 [Abstract] ( 787 ) [HTML 1KB] [ PDF 2441KB] ( 708 )
126 Modal analysis of axial-flow pump rotor system in water
CHEN Yujie, ZHENG Yuan, KAN Kan, ZHANG Haisheng, XU Jianye, CHEN Peng, CHEN Rongjie
Studying the modal of axial-flow pump rotor system in water and the impact of water on modal is important to ensure the efficiency, stable running of the pump and to avoid resonance. By secondly developing the ANSYS Workbench based on fluid-solid coupling theory, we compiled APDL language to couple the fluid and solid calculation equation so as to calculate the modal of axial-flow pump rotor system in air and water. The results show that when the three-dimensional modeling of structure domain was carried out before modal analysis, the hollow portion of structure cannot be simplified to solid area, which is different from flow field analysis. The existence of water makes each order natural frequency of rotor system declined. The depreciation coefficient ranges from 7.95% to 13.29% and each order depreciation coefficient does not show an obvious rule. The blade passing frequency of axial-flow pump is 15 Hz and the guide passing frequency of axial-flow pump is 25 Hz, which are much less than each order natural frequency of axial-flow pump rotor system in water, so it is less likely to generate resonance during running time.
2017 Vol. 35 (2): 126-132 [Abstract] ( 952 ) [HTML 1KB] [ PDF 1545KB] ( 731 )
133 Numerical simulation of three-dimensional turbulent flow in a transition process of a hydraulic turbine passage with uniform rotation of guide vane
WANG Wenquan, LI Weizhong, YAN Yan
The three-dimensional transition process in a simplified flow passage of model Francis turbine is researched based on an implicit direct forcing immersed boundary(IB)method combined with the three-step time-splitting method. The coupling mathematical model of the transition process including turbulent flow and rotating rigid guide vanes is established using unsteady Navier-Stokes equation with additional momentum source term. The moment source is not pre-calculated, but determined implicitly in such a way that velocity at the immersed boundary interpolated from the corrected velocity field accurately satisfies the non-slip boundary condition. The temporal distribution of vorticity and turbulent quantity are gained at the whole transient process, also, the drag and lift coefficients as well as other force against attack changing are obtained through the information transferring between the solid grid and fluid background grid. At the same time, the coupling relations among the turbulent flow, the dynamical force response of blade and the rotating of guide vane are achieved, which is helpful to improving the design of hydraulic transition process.
2017 Vol. 35 (2): 133-137 [Abstract] ( 1018 ) [HTML 1KB] [ PDF 2054KB] ( 558 )
138 Protective properties of horizontal air vessel for water hammer
HE Cheng, ZHANG Jian, ZHENG Yuan, WANG Yankang, HE Dongyang
Considering the problem of vertical air vessel safety, large installation space and the limitations of the topographic condition and plant size, a new installation type of air vessel, called the horizontal air vessel, is introduced as an alternative scheme. Based on the method of characteristic, the boundary condition mathematical model of horizontal air vessel is built and the numerical calculation formula of pressure and water level in the vessel is deduced. According to the fluid transients numerical simulation of the vertical and horizontal air vessels under pump-stopping, the results show that both the vertical and horizontal air vessels can effectively protect the pump-stopping water hammer; with the same shape parameters, the variation of water level in the horizontal air vessel is smaller than that in the vertical vessel, and the horizontal air vessel has a relatively better protective properties for water hammer than the vertical air vessel. As for a given volume horizontal air vessel, there is a best restric-ted orifice for water hammer protection. Under the prerequisite that the water of the air vessel supplied to the pipeline is enough, increasing the initial gas volume and installation elevation of horizontal air vessel will make the protective effects on water hammer better.
2017 Vol. 35 (2): 138-143 [Abstract] ( 821 ) [HTML 1KB] [ PDF 1537KB] ( 663 )
144 Fitting expression of relationship gas viscosity, and temperature and/or pressure
DENG Qiangguo,, SONG Pengyun, MAO Wenyuan, XU Hengjie
Gas viscosity is an important parameter for the performance of gas lubrication mechanism such as dry gas seal. The gas viscosity is related to temperature and pressure under the condition of high pressure, but there are few researches about the detailed relations between viscosity, temperature and pressure. Nitrogen(N2)is taken as the study object, and the viscosity-temperature fitting expression and the viscosity-pressure fitting expression, the viscosity-temperature-pressure fitting expression have been obtained based on the AP1700 material physical platform using the least square method by a mathematic software. The calculated results by the fitting expressions have enough accuracy compared with the viscosity values offered by the National Institute of Standards and Technology(NIST)Chemistry WebBooks, China national standard Heat Exchangers(GB/T 151-2014), calculated values in Booser′s publication Tribology Data Handbook respectively and calculated values by the Lucas equation. The results show that the fitting expressions can be used to express the changing laws of gas viscosity with temperature and pressure and to calculate the viscosity concerning the temperature and/or the pressure.
2017 Vol. 35 (2): 144-151 [Abstract] ( 2501 ) [HTML 1KB] [ PDF 1677KB] ( 2483 )
152 Mechanism analysis and inclination optimization of the wind turbine side speed limit mechanism
SUN Feng, WANG Jianwen,, LIU Xiongfei ,
The theoretical torque formula is derived for the small-sized wind turbine with the speed li-mit mechanism. The aerodynamic performance of the blade and the tail, reveals the wind wheel cornering, tail deflection and gravity return torque generation mechanism were anahyzed. The exact expression formula of the moment was derived. It is pointed out that the research on the speed limit mechanism lays an emphasis on the dynamic balance process between lateral torque; On this basis, the selection principle of lateral mechanism important parameters is presented in detail, and under the conbination of post dip β′ and side inclination β″ of 8 different tail oblique hinge axies, using Matlab simulation software we draw the programming tail moment Mb and motor P output power curves. The results show that the post dip β′>side inclination β″structure cornering speed wind turbine can satisfy the requirements of dynamic equilibrium between the torque in the control process. Using Matlab software in the β′>β″ structure found the best angle combination of post dip β′=8 and side inclination β″=3 is found, which can ensure that wind power output is constant and the laterality of the intergral wind turbine is stable, which provides a technical basis for the future which will further analyzing the small-sized wind turbine side mechanism analysis.
2017 Vol. 35 (2): 152-157 [Abstract] ( 958 ) [HTML 1KB] [ PDF 1408KB] ( 591 )
158 Growth and quality of potted strawberry under aerated drip irrigation in the three typical soils in Henan Province
LEI Hongjun, FENG Kai, ZHANG Zhenhua, PAN Hongwei, ZANG Ming
The effects of aerated drip irrigation on the potted strawberry growth and quality under three typical soils were researched to provide technical support for the cycle aerated irrigation technology. Results showed that compared with control treatments, the crop growth and physiological parameters in aerated groups were increased by 25.3%, 21.5% and 18.2% for plant height, 18.6%, 13.4% and 15.7% for net photosynthetic rate, 26.4%, 5.6% and 10.9% for transpiration rate, 12.6%, 3.4% and 15.7% for VC content in the yellow clay soil in Zhengzhou city(YC), clay loam soil in Nanyang city(CL), and heavy loam soil in Zhumadian city(HL), respectively. The sugar-to-acid ratio in aerated group in the soil of YC, CL and HL were increased by 47.1%, 7.7% and 25.1%, respectively. The root length, root-to-top ratio and root activity of aerated groups were better than the control treatments, and increased by 48%, 24.1%, 40.2% in the YC soil, 17.8%, 28.0%, 20.0% in CL soil, 27.7%, 20.8%, and 40.1% in HL soil, respectively. Significant differences were found in root length, root-to-top ratio, and root activity between the aerated and control treatments. In short, the aerated drip irrigation could significantly improve the strawberry growth for all the three soils with the best improvement effect in YC soil.
2017 Vol. 35 (2): 158-164 [Abstract] ( 838 ) [HTML 1KB] [ PDF 1429KB] ( 1164 )
165 Assessing blue and green water use efficiency in grain production of China
WANG Dandan, XIAO Lan, ZHANG Junhong,
In order to assess the spatial variation of blue and green water use efficiency in grain production of China, the provincial total and irrigated farmland water resources utilization of generalized water productivity(Ptu, Piu), evapotranspiration and water productivity(PtET, PiET)and rain-fed grain crops water productivity(Pr)in the year 2010 were calculated. Then the spatial distribution pattern of all water productivity indicators, as well as the effects of irrigation on regional water and productivity were analyzed. The result shows that national Ptu, PtET, Piu, PiET and Pr were estimated to be 0.765, 0.979, 0.767, 1.002 and 0.758 kg/m3 respectively. The spatial distribution pattern of four indicators Ptu, PtET, Piu and PiET was similar with each other, while none of them was significantly correlates with Pr in grain production. Irrigated farmland played a leading role in both water use and the spatial distribution of water productivity of China. The unit production of grain yield in irrigated farmland was 2.6 times that in the rain-fed farmland at the national level. Piu in the North China Plain and its surrounding provinces was higher than Pr, while irrigation reduced water productivity in 15 provinces, for example Hainan province, although the yield of grain crops increased. The results can provide a reference for agricultural water management.
2017 Vol. 35 (2): 165-171 [Abstract] ( 918 ) [HTML 1KB] [ PDF 2469KB] ( 697 )
172 Effects of activated carbon on agronomic traits and yield of spring maize
WANG Zengli, FENG Hao,, FANG Yuan
Effects of activated carbon on agronomic traits and yield of spring maize were studied by using pot experiments. The results show that the growth rate of the growth period and chlorophyll content of spring maize first increase and then decrease with the increasing of activated carbon(0-9 g/kg). The total dry matter accumulation of spring maize has shown a decline in seeding and a rise in heading. The soil blended with activated carbon increase upper biomass of spring maize in the vegetative growth stage, whereas it had a threshold value for underground biomass in the reproductive growth stage. The root growth was dramatically inhibited when the content of activated carbon was more than 6 g/kg. The number of grains and ear length have a significant positive correlation with kernel yield, and the kernel percentage had a significant or an extremely significant positive correlation with the root-shoot ratio. In conclusion, the soil blended with activated carbon could obviously increase the number of grains, the root-shoot ratio and the yield of spring maize. Blending 1 g/kg of activated carbon to soil was effective and optimal to the yield of spring maize.
2017 Vol. 35 (2): 172-177 [Abstract] ( 819 ) [HTML 1KB] [ PDF 1299KB] ( 633 )
178 Influence factors of muddy water film hole irrigation infiltration
ZHONG Yun, FEI Liangjun, FU Yuliang, JIN Shijie, WANG Jinhui
In orded to reveal the difference of muddy water infiltration and clean water infiltration, through the test data of free infiltration of muddy water film hole irrigation, analyzed the influence of free water infiltration capacity of muddy water film hole irrigation, such as clay and sand grade,size of film hole,soil bulk density and initial soil water content were researched.The results show that various factors all have a significant impact on the film hole irrigationfree infiltration capcity,putting forward the relationship between the influence factors and the infiltration capacity of muddy water film hole irrigation.And the model of clay and sand grade,size of film hole,soil bulk density and cumulative infiltration volume per unit film hole area of free infiltration of muddy water film hole irrigation of initial soil water content and steady infiltration rate was established, moreover, its correlation coefficient is greater than 0.960 0. Based on the model, the cumulative infiltration volume per unit film hole area and steady infiltration rate can be obtained, further judging the free infiltration capacity in soil under muddy water film hole irrigation. The results could provide the reference for further studies of muddy water film hole irrigation free infiltration law and muddy water film hole irrigation technology.
2017 Vol. 35 (2): 178-184 [Abstract] ( 761 ) [HTML 1KB] [ PDF 1790KB] ( 594 )
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