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Journal of Drainage and Irrigation Machinery Engin
 
2015 Vol.33 Issue.11
Published 2015-11-25
921 Design and experiment on turbulence generator of medium consistency pump
Ye Daoxing, Li Hong, Zhuang Haifei, Tang Pan, Zou Chenhai
In order to realize fluidization and gas-liquid separation in medium consistency pulp, a method is proposed for designing a turbulence generator in which the blade camber is composed of two helixes with constant and variable leads. Then the turbulence generator is designed for a specific medium consistency pump. A mesh in the fluid domain is generated in ICEM, and ANSYS-CFX, the standard k-ε turbulent model and the Eulerian gas-liquid two phase flow model are used to analyse gas-liquid two-phase flow field in the generator, the grid independence feature is examined. It is found that air mainly accumulates in the blade suction side and near the blade root of the generator. The pump performances are measured by using a medium consistency pump test stand when pumping water and pulps respectively with 7.52%, 9.30%, 12.10% mass concentrations. It is revealed that the efficiency and head decrease with increasing mass concentration, but the head of pumping 7.52% pulp is slightly higher than that of water. Since the pump was not clogged by pulp during the test, the feasibility of the turbulence generator design method has been confirmed.
2015 Vol. 33 (11): 921-925 [Abstract] ( 990 ) [HTML 1KB] [ PDF 2356KB] ( 1144 )
926 Design of low specific-speed centrifugal pump based on boundary layer separation theory
Yang Jingjiang, Lu Xinquan, Chen Huilong, Yao Dengjie
In order to study impacts of boundary layer separation on hydraulic performance of centrifugal pump with low specific speed, new impeller blade profiles are designed by means of turbulent boundary layer theory in centrifugal pump impellers under the condition of boundary layer without separation when the geometrical parameters of blades remain unchanged at the inlet and outlet to exploit a method for preventing or supressing boundary layer separation on blade surfaces. The blade angle β is used as a primary variable in the blade profile equation and the velocity coefficient as a control factor. It is shown that that the momentum thickness of boundary layer and impeller theoretical head increase with increasing velocity coefficient. Obviously, a reduced velocity coefficient is beneficial to suppressing boundary layer separation on blade surfaces under the condition that a required theoretical head has been met. The results of CFD simulation show that an unreasonably designed blade profile of the impeller of low specific speed centrifugal pump is the major reason resulting in boundary layer separation on blade surfaces, and boundary layer separation can induce a degraded pump performance. Under the design condition, the head of the pump with redesigned blade profile doesn′t show an obvious increase compared with the original pump, while the hydraulic efficiency is improved in some degree. This suggests that the newly designed blade profile can improve the flow condition inside the impeller and prevent the onset and development of reverse flow and vortex effectively.
2015 Vol. 33 (11): 926-931 [Abstract] ( 1098 ) [HTML 1KB] [ PDF 1810KB] ( 1478 )
932 Numerical simulation of siphon formation in siphon discharge passage
Li Haifeng, He Minghui, , Pan Zaibing
Based on the RNG k-ε turbulence model and SIMPLEC algorithm, the water injection process to a siphon discharge passage is calculated numerically. Volume of fluid(VOF)method is adopted to trace the free surface and the water-air interface evolution, eventually the siphon formation process is reproduced. The mass flow at the outlet of the vacuum breaker valve is analyzed and its closing time is determined as well. The results show that the air is discharged from the vacuum breaker valve during the water filling process, then the water level ascends gradually until up to the hump. At the hump point, a small portion of the water is discharged from the valve, but the rest water flows down to the outlet along the bottom of the passage. The vacuum breaker valve experiences a series of cycles of exhausting-inspiration. The closing time is determined based on these cycles. After the valve is fully closed, a negative pressure emerges and the siphon is formed on the hump, but a longer time is needed for the rest air to be discharged.
2015 Vol. 33 (11): 932-939 [Abstract] ( 1096 ) [HTML 1KB] [ PDF 1949KB] ( 1703 )
940 Solid-liquid two-phase flow in rotor and stator cascades based on LES
Han Wei,Yue Ting,Li Rennian,Jin Yi,Shen Zhengjing,Zhang Zhao
In order to study unsteady solid-liquid two-phase flows in rotor and stator cascades of centrifugal pump and understand the flow details in the flow passages, a centrifugal pump with radial diffuser is chosen, and then the unsteady 3D flow field in it is simulated based on the mixture multiphase model and sliding mesh as well as the large eddy simulation(LES)turbulence model with structures mesh generated in ICEM. The evolution process of coherent vortexes in the two cascades is exploited and the change in vortex pattern at different locations is analyzed in the solid-liquid two-phase flow by comparing with single phase water flow. The results show that the pattern of attached vortexes remains unchanged basically under two-phase and single phase flow conditions. The vortexes produced by impeller rotation experience a series of evolution process, namely curling, merging and breaking. Even though the solid particles affect the distribution of vorticity in the flow field in the pump a little, they accelerate the dissipation of eddy energy and alter the vortex location and breaking pattern. The evolution process of vortexes depends on positions considered in the cascades under either single or two-phase flow condition.
2015 Vol. 33 (11): 940-944 [Abstract] ( 809 ) [HTML 1KB] [ PDF 3239KB] ( 1407 )
945 State feedback controller without steady-state error for water level in regulating reservoir of cascade hydropower plants
Yang Haixia, Fan Honggang, Zhu Yuanyue, Chen Naixiang
In order to keep the stability of operation of cascade hydropower stations, a state feedback controller is designed based on optimal control theory. The water level deviation value of the regulating reservoir between two power stations is introduced to the feedback regulator of the upper station. As a result, it can not only regulate the speed, but also balance the discharge of each station to stabilize the water level. Effects of weighting factors of speed, water level and guide vane opening on system dynamic characteristics of the controller are compared by numerical simulations. The results show that the weighting factors of speed and water level have a little influence on the regulation quality. For example, the maximum change in speed is about 3% in 45 s settling time; and the maximum change in water level is approximately 0.011% in around 4 000 s settling time. However, when the weighting factor of guide vane opening is reduced to 1 from 130, the maximum change in speed is decreased by approximately 46%, and the maximum variation of water level is lowered by about 41%, and the settling time is shortened to approximately 33%. Hence a controller with a smaller weighting factor in guide vane opening can reduce the settling time of speed and fluctuations in speed and water level. In order to facilitate practical application of the controller, by reasonably selecting a weight factors matrix, a reduced-order state feedback controller is designed to realize zero error in water level in regulating reservoir. According to the simulation results, regulation quality of the states, such as speed and water level reservoir has little difference between the reduced-order state feedback controller and the full-state feedback controller.
2015 Vol. 33 (11): 945-952 [Abstract] ( 988 ) [HTML 1KB] [ PDF 1844KB] ( 1300 )
953 Analysis of transient flow in vertical mixed-flow pumping system during pump stopping period by closing valve in two-phase mode
Xue Honglin, Zhang Chi, Li Yanjun, Xie Shanfeng
Based on the features of hydraulic structure in large mixed-flow pump stations, a mathematical model of pump transient stopping process is established by means of characteristics method with combination of pump and valve hydraulic characteristic curves. It is shown that if the pump station encounters an emergency shutdown, the highest pump inverse rotational speed can be as fast as 1.56 times the rate speed, causing the design limit specified in related design guidelines of pumping station is exceeded. This prediction is basically in agreement with the runaway characteristics measured on a prototype of the pump. As a case study, an optimization model is established for a valve on the discharge pipeline in the pump station to be closed in two-phase mode. In the model, the water hammer pressure is used as objective function, the valve closing angle and time are as optimizing variables with certain constrains. At first, the minimum range of objective function is determined, and the search step is shortened gradually until the optimized one is achieved. The results show that when the butterfly valve is closed for 88° in first 3 s and then for 2° in the other 20 s the maximum water hammer pressure is 31.4 m and the maximum reverse flow rate through the pump is 1.0 m3/s.
2015 Vol. 33 (11): 953-959 [Abstract] ( 864 ) [HTML 1KB] [ PDF 1761KB] ( 1488 )
960 Design of friction pairs of bottom pivot and analysis of their tribological properties in ship lock
Liu Hai,, Wang Shulin
To cope with the problem of premature malfunction resulted from abnormal friction and wear of bottom pivot in ship locks, two kinds of material, such as Fz5(3)and 38CrMoAlA, are chosen to be the material of mushroom-shaped cap respectively, forming two types of friction pairs with the 40Cr shaft head. Firstly, the tribological properties of these two pairs are measured under water and grease lubrications by a MM-200 tribometer. Then, the wear performance of five sorts of mushroom-shaped cap and shaft head couples, which are originated from two types of existing friction pairs, is identified in a test rig under simulated conditions. It is shown that the friction pairs of two materials with 40Cr, exhibit very good tribological properties under grease lubrication condition, for example, the friction coefficient is 0.061 for self-lubrication enchased brassiness Fz5(3)and 0.07 for 38CrMoAlA. Unfortunately, the 38CrMoAlA and 40Cr couple is badly worn under deficient water lubrication condition. Under the simulated conditions, the Fz5(3)and 40Cr friction pair exhibits an excellent wear performance, typically the amount of wear is just 0.45 mm for Fz5(3)and 0.12 mm for 40Cr after 150 000 loading cycles. The life span of this friction pair can meet the requirement on overhaul period of time of ship lock better.
2015 Vol. 33 (11): 960-964 [Abstract] ( 851 ) [HTML 1KB] [ PDF 1819KB] ( 1345 )
965 Beidou Navigation Satellite System-based variable prescription pesticide spraying system for farmland
Chen Zhigang, Chen Mengxi, Wei Xinhua, Li Jinyang, Li Lin
A set of embedded farmland information processing system is developed for on-board variable pesticide prescription spraying units based on Beidou Navigation Satellite System(BDS)to realize online variable prescription spraying in farmland and improve pesticide utilization efficiency as well as reduce the environment and human health hazards caused from pesticide. The EPCS-8980 ARM industrial control computer and embedded GIS system are used as information processing unit, Beidou navigation receivers are adopted as positioning tool and Hall proximity switche sensors are utilized to detect vehicle speed. The on-board computer receives positioning information from the Beidou navigation receivers through RS-232 interface, and communicates with other devices via CAN bus. The embedded GIS system is developed with eSupermap, and runs on Windows CE 5.0 on operating system. The information processing system is able to generate farmland information distribution map, decide variable pesticide spraying prescription diagram and provide interpretations as well as detect vehicle speed. The test results show that the time for prescription map interpretation is less than 1 s, the grid discriminant error is less than 0.75 m, and the speed detecting error is about ±0.1 km/h. This suggests the system can complete its preset functions and realize online variable prescription spraying well.
2015 Vol. 33 (11): 965-970 [Abstract] ( 1091 ) [HTML 1KB] [ PDF 1746KB] ( 1331 )
971 Analysis of water-saving potential of different scale irrigation fields in river network districts
Fei Yuanhang, She Dongli, Meng Jiajia, Guo Jie, Yu Shuang′en
The existence and reuse of return water in river network districts not only intensifies scale effect of water-saving potential, but also results in arguments about what the actual water-saving potential is. In the paper, irrigation water utilization coefficients of different scale irrigation fields in river network districts are studied by making use of head-tail analysis method. Additionally, the improved threshold of utilization coefficient and actual water-saving potential are evaluated comprehensively. The results show that the utilization coefficients of irrigation water in large- and medium-sized irrigation fields are significantly lower than those of small-sized fields, and the utilization coefficient varies across small-sized irrigation fields obviously. Since the effects of water-saving irrigation factor on utilization coefficient of irrigation water is higher than the other factors, the utilization coefficient of irrigation water should be improved by implementing water-saving irrigation projects. The actual water-saving potential per unit area in large- and medium-sized irrigation fields is considerably lower than that of small irrigation areas. However, because the area of large- and medium-sized experimental irrigation fields is huge, the water-saving potential mainly depends on those fields, especially in the large-sized irrigation fields which are with 8-63.72 million m3 recent actual water-saving potential and 10.95-82.01 million m3 forward actual potential, respectively. Therefore, various water-saving measures should be taken for different scale irrigation fields to improve utilization coefficient of irrigation water.
2015 Vol. 33 (11): 971-976 [Abstract] ( 1060 ) [HTML 1KB] [ PDF 1571KB] ( 1208 )
977 Nitrogen-lead interaction and accumulation effects of lead on growth of Jatropha curcas L.
Wang Weihua, Lei Longhai, Zhang Zhipeng, Yang Qiliang
In order to study on interaction of nitrogen and lead and accumulation effects of heavy metal-Pb on Jatropha curcas L., in this article, three nitrogen levels(N0:0, N1:300 mg, N2:600 mg)and three kinds of soil lead pollution levels(Pb0:0, Pb1:500 mg, Pb2:1 000 mg)are used for experiment. The results show that there is no statistical signification between Pb1 and Pb0 treatment, further the lead inhibits the growth and development of Jatropha curcas L. significantly, if no nitrogen fertilizer is applied. However, with the increase of nitrogen fertilizer, the inhibiting effect of lead on Jatropha curcas L. is relieved, the biomass of N1Pb2 and N2Pb2 is increased by 32.0% and 8.1% compared with N0Pb2. After nitrogen fertilizer is used, the soil nitrate content is almost the same in 5, 10 and 15 cm deep soil layers. Additionally, the change of soil nitrate nitrogen content in N0Pb2 and N1Pb2 is smaller compared with the other treatments. This suggests the nitrogen fertilizer can reduce the amount of lead in the plants, and improve its effective extraction. For example, the effective extractions of lead in N2Pb2 and N1Pb2 are increased by 18.1% and 27.9%, respectively, compared with that of N0Pb2. Thus, with the increase of nitrogen content, the inhibiting effect of lead on Jatropha curcas L. is decreased considerably, a high nitrogen content can increase the biomass of the plants and the effective extraction of lead, causing an improved restoration efficiency.
2015 Vol. 33 (11): 977-984 [Abstract] ( 1297 ) [HTML 1KB] [ PDF 1583KB] ( 1192 )
985 Comprehensive evaluation of operational status of large-scale irrigation district based on grey relation theory and TOPSIS method
Wang Jinhui, Fei Liangjun, Xie Fang, Wang Guanshe, Feng Chanli
At first, an objective and scientific index system is established to evaluate the operational status of a large-scale irrigation district; and then the subjective weights figure out with G1 by using the idea in game theory and the objective weights estimated with coefficient of variation method are integrated to get a set of final index weights. Eventually, the grey relation theory and TOPSIS method are applied to evaluate operational status of large-scale irrigation district with this set of index weights. To validate the method and index system, a large-scale gravity canal irrigation district—Luohuiqu Irrigation District in Shaanxi Province is chosen, and the evaluated results show that the relative closeness of this district is 0.179 1, 0.156 1, 0.214 9, 0.415 1, 0.509 1 and 0.768 2, respectively in 2007—2012, accordingly the levels of operational condition are moderate, moderate, moderate, good, good and good as well. The comprehensive evaluation results of grey relation theory-TOPSIS method are basically in accord with those obtained by extenics method, namely with time passing, the evaluated level of operational status becomes good from moderate, showing the operational condition will get better and better. This also conforms to the objective reality and developing tendency of the district. Thus, grey relation theory and TOPSIS method can be applicable in comprehensive evaluation of operational status of large-scale irrigation district.
2015 Vol. 33 (11): 985-990 [Abstract] ( 1056 ) [HTML 1KB] [ PDF 1386KB] ( 1611 )
991 Photosynthetic characteristics of Arabica coffee and its antioxidant enzyme response to limited irrigation and nitrogen
Zhang Yan, Liu Xiaogang, Wan Mengdan, Wang Lu, Xu Hang, Yang Qiliang
The objective of this study is to explore an efficient management mode of water and nitrogen fertilizer for Arabica coffee. Effects of irrigation and nitrogen levels on growth and photosynthetic characteristics of Arabica coffee were studied in greenhouse planting slot for 1.5 years. The irrigation and nitrogen management modes include four(W1-sufficient irrigation, W2-high water, W3-middle water, and W4-low water)and three(N1-high, N2-middle nitrogen and N3-low nitrogen)levels, respectively. The results show that the water content in the soil changes with irrigation time and has the maximum on the third day after irrigation; and the irrigation results in a greater effect on the photosynthetic efficiency of leaves and water use efficiency than the nitrogen does. For example, the net photosynthetic rates are increased by 19.60%-57.35%, 18.06%-94.72%, 4.40%-107.62% and 2.59%-79.94% at 10:00, 12:00, 14:00 and at 16:00, respectively, under N1 nitrogen condition at water levels W1 to W3, compared with level W4. The net photosynthetic and transpiration rates of leaves increase with nitrogen level initially, but then decrease; water use efficiency always increases with irrigation level. The activities of antioxidant enzymes(superoxide dismutase, peroxidase and ascorbate peroxidase)have got the maximum value at level W3, comparing with level W4, they are increased by 5.01%, 97.70% and 167.61%, respectively. This suggests that the enzyme is the most active when the moisture content is relatively lack. An increased irrigation and nitrogen levels can improve Arabica coffee growth parameters, such as plant height, stem diameter, branching factor, and crown diameter, number of leaves and new-branch length. For the combination of N2 and W2, not only the water use efficiency is the maximum, but also the growth parameters and initial yield are more satisfactory, thus this combination is the best for a higher efficient utilization of both water and nitrogen fertilizer.
2015 Vol. 33 (11): 991-1000 [Abstract] ( 1223 ) [HTML 1KB] [ PDF 1597KB] ( 1260 )
1001 Thinking about further development of drip irrigation technology and equipment
Han Qibiao,, Feng Shaoyuan, Cao Linlai, Huang Xiuqiao, Fan Yongshen, Li Hao
For drip irrigation technology, product and equipment to develop better in China, the popularization and application of the technology in future are the problems that should be considered and summarized currently. In this paper, the overall advance trend of drip irrigation technology is analyzed by combining with new situation of agricultural production, and it is showed that the future application scope of drip irrigation will be even border, and the concept of technology integration and intelligent irrigation will be reflected more substantially, and the efficient use of energy resources will be paid significantly more attention. Further, the development in theory, technology, equipment and manufacturing of drip irrigation has been thought and stressed to some degree. It is considered that the network optimization theory, massed water drip irrigation technology and low-energy irrigation technology and so on need to be strengthened in the drip irrigation theory and technology. In the product research and development, high flow filters, precision fertilization equipment, new type of emitters, intelligent hardware and software, drip tape recovery equipment and other innovative products should be paid significant attention. Meantime, the establishment of drip grassroots service team is called. This paper could provide a technical support for the further development of drip irrigation technology and equipment. 
2015 Vol. 33 (11): 1001-1005 [Abstract] ( 1107 ) [HTML 1KB] [ PDF 1354KB] ( 1375 )
1006 Liquid tank modelling and attitude controller design of plant protection UAV
Wang Dawei, Gao Xifeng
To improve the controllability of plant protection UAV with eight rotors, the level of liquid in the tank is analysed and modelled during pesticide spraying process. As a result, formulas for the liquid mass and moment of its inertia are presented in terms of time, causing an accurate dynamical model in time domain. To validate the correctness and effectiveness of control of the model, attitude controllers are designed by using adaptive backstepping terminal sliding mode control technology. Firstly, the typical backstepping control method is used, then the terminal sliding mode control is introduced for the last state to converge the ideal value in a finite period of time, finally, an adaptive control law is established to eliminate uncertain disturbances. Note that all the controllers designed have met the Lyapunov stability criterion. These proposed controllers are simulated and tested, their results are compared with those of fuzzy PID attitude controller. The simulated and experimental results show that the proposed dynamic model can make the adaptive backstepping terminal sliding mode controller applicable for the plant protection UAV. Compared with Fuzzy PID controllers, the effectiveness of attitude controller is improved greatly, the errors in attitude angle are reduced by about 25.57%, 24.21% and 19.41% in experiment, respectively. Additionally, the controllers are insensitive to random disturbances and subject to a nicer robustness property.
2015 Vol. 33 (11): 1006-1012 [Abstract] ( 1297 ) [HTML 1KB] [ PDF 1919KB] ( 1344 )
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