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Journal of Drainage and Irrigation Machinery Engin
 
2014 Vol.32 Issue.7
Published 2014-07-25
article
Article
553 null
Yuan Shouqi, Niu Guoping, Tang Yue, Tang Lingdi, Zhu Xiangyuan
null
2014 Vol. 32 (7): 553-557 [Abstract] ( 1651 ) [HTML 1KB] [ PDF 3597KB] ( 1664 )
558 Experimental study on flow in diffuser of liquid-jet gas pump
Xiang Qingjiang,, Wang Chao, Wu Yanlan, Li Hong
The liquid-jet gas pump has found its applications in jet aeration system and gas absorption etc. A study on the two-phase flow in diffuser of the pump is essential for the pump design and application. Thus, the pressure on the diffuser wall of a liquid-jet gas pump(LJGP)was measured by means of pressure sensors and the pressure recovery profile in the diffuser was obtained under various water working pressures and liquid-to-gas volumetric flow rate ratios. The LJGP was installed vertically; its diffuser and throat were made of Plexiglas. The results showed that the wall pressure recovery is in the range of about 2-5 kPa, the pressure profile drops initially then rises along the diffuser wall. Therefore, the effect of static pressure caused by the height of a vertical LJGP on flow in its diffuser needs to be taken into account. According to an analysis of flow in the diffuser, it was shown that the flow pattern has a great influence on its jet mixing characteristics; further the change in the location where the liquid-jet starts to mix with the gas can affect diffusing angle of the diffuser significantly. Particle image velocimetry(PIV)was used to map the liquid velocity in the diffuser, and the axial velocity distributions in cross-sections were obtained at two liquid-to-gas volumetric flow rate ratios. The results illustrated that the axial velocity is reduced by about 20%, and it was not uniform in cross-sections; the flow with high velocity has been deflected to one side wall in the diffuser at a low flow rate ratio.
2014 Vol. 32 (7): 558-562 [Abstract] ( 2176 ) [HTML 1KB] [ PDF 1659KB] ( 1887 )
563 Effects of nozzle location on new type annular jet pump performance
Xu Maosen,, Long Xinping,, Yang Xuelong,, Wu Wei,, Wang Xiaochuan,, Wang Xueying,
A numerical simulation method was utilized to explore effects of nozzle location on perfor-mance of a new type annular jet pump(NTAJP). NTAJP has a newly-designed annular nozzle in which an annular jet is off the pump suction chamber wall and totally immerged in the sucked liquid compared with the conventional annular nozzle that the annular jet is along the chamber wall only. The NTAJP performance was numerically predicted and compared with the conventional pump. Effects of nozzle location on the performance were analyzed under different central suction nozzle-to-outer annular nozzle velocity ratios(vr). It was shown that NTAJP generally has better efficiency than the conventional one. The annular nozzle located at 8 mm away from the suction chamber wall has the best performance. For the NTAJP with the nozzle at 4 mm and 6 mm away from the wall respectively, the best vr is 1/1 when the flow ratio is ranged in 0.4-0.8. For the NTAJP with the nozzle at 8 mm away from the wall, however, the best vr is 3/1 in the same flow ratio range.
2014 Vol. 32 (7): 563-566 [Abstract] ( 1894 ) [HTML 1KB] [ PDF 1420KB] ( 1353 )
567 Impact of blade number on fluid-induced vibration in centrifugal pump
Zhou Pan, Zhang Quan, Shuai Zhijun, Li Wanyou
In order to study impact of blade number on fluid-induced vibration in centrifugal pumps, the impellers of a centrifugal pump were designed with 6 and 7 blades while the rest geometry remains unchanged, the fluid induced vibration in the pump was investigated by experiment and simulation si-multaneously. Firstly, the RNG k-ε turbulence model was used to simulate the steady and unsteady flow in the two configurations; secondly, the steady velocity and pressure, and unsteady pressure fluctuations were obtained and analyzed. Finally, the vibration signals at pump feet were measured and processed to validate the simulated results and the effect of blade number. The results showed that the pressure pulsation at monitoring points in the impeller and volute with 6 blades was less than that with 7 blades, and the vibration response at the feet under shaft rotational frequency was also smaller. For the impeller with 7 blades, the peak value at two times the shaft rotational frequency and the blade passing frequency became larger; while the amplitude at the frequency larger than the blade passing frequency was decreased. These results can be instructive for design of a centrifugal pump with low vibration and noise.
2014 Vol. 32 (7): 567-571 [Abstract] ( 1728 ) [HTML 1KB] [ PDF 1493KB] ( 1842 )
572 Suitability of groundwater source heat pump variable flow operation mode for climate zone
Wang Songqing, Zhang Xu, He Shijing
For operation safety point of view, the influence of ground water source heat pump(GWSHP)variable flow operation mode on characteristics of aquifer hydraulic parameters was investigated for the office buildings in the typical cities in different climate zones. The variation characteristics of porosity and permeability coefficient of borehole wall were identified by means of numerical simulation method under various operation modes of GWSHP pumping system; consequently the suitability of GWSHP operation mode for climate zone was analyzed. It was presented that the porosity of borehole wall was decreased by 45%, 48% and 44%, the permeability coefficient was reduced by 48%, 51% and 46%, respectively, in cold, severe cold, hot summer and cold winter zones under variable flow operation mode after running for five years compared with constant flow operation mode. After taking the effect of climate zone on characteristics of air conditioning load into account, the GWSHP variable operation mode is most suitable for severe cold zone, more suitable for cold zone, but less suitable for hot summer and cold winter zone.
2014 Vol. 32 (7): 572-577 [Abstract] ( 1417 ) [HTML 1KB] [ PDF 1252KB] ( 1506 )
578 Ranking the first, second and third class factors that affect head of low specific speed centrifugal pumps
He Xijie, Zhang Meng, Li Xueying
The first, second and third class factors that affect the head of low specific speed centrifugal pumps are ranked by using grey theory. The first class factors include the impeller parameter IP and volute parameter VP; the second class factors have four parameters, such as impeller inlet parameter IIP, outlet parameter IOP, volute plane parameter VPP and cross-sectional parameter VSP; the third class factors involve 14 parameters, namely impeller eye diameter D0, outlet diameter D2 and volute base circle diameter D3 and so on. The results show that IP has the most important effect on the head but the effect of VP is the smallest for the first class factors. For the second class factors, the IOP effect is the largest, the VSP effect is the smallest, and the IIP and VPP influences are in between. For the third class factors, the head is affected in the order(great to small)of D2 β2 Z b2, β1 D0 b1, D3 α s, and b3 b4 h FⅧ, respectively in IOP, IIP, VPP and VSP parameter groups. The concept, idea and method on the classification of impeller and volute geometrical parameters are new, and the corresponding grey relational grade formulas are proposed firstly. The results achieved can provide an important basis for design and existing product update of low specific speed centrifugal pumps.
2014 Vol. 32 (7): 578-582 [Abstract] ( 2116 ) [HTML 1KB] [ PDF 1134KB] ( 1359 )
583 Design and optimization of super-large capacity submersible axial-flow pump impeller
Wu Chunjie,, Bing Zhigang, Cheng Li, Chen Jiajing, Wang Leqin, Zhai Songmao
The impeller blade of a super-large capacity submersible axial-flow pump was designed based on the airfoil theory, the flow in the pump system was simulated by using computational fluid dynamics(CFD)method and the pump performance was predicted. The pump hydraulic model was optimized based on the numerical simulations of three different hydraulic models, and verified experimentally. It was shown that there is a noticed high-pressure region near the blade pressure side and the leading edge in the original impeller, additionally near the blade suction side and leading edge there exists a low-pressure region and an intensive vorticity, which consumes considerable energy resulting in a poorer hydraulic efficiency. The original impeller was optimized by increasing the inlet blade angle and reducing the rotational speed, consequently the optimized impeller is subject to a more uniform static pressure distribution in the blade pressure side and a shrunk vortex zone in the suction side with even vorticity. Clearly, the pump cavitation performance and hydraulic efficiency have been improved. The performance of optimized hydraulic model exhibits good agreement with the experimental data, indicating the numerical results can reveal the actual performance of a hydraulic model exactly. The methods adopted in this study may provide a reference for hydraulic model optimization and perfor-mance improvement of submersible axial-flow pumps.
2014 Vol. 32 (7): 583-587 [Abstract] ( 1686 ) [HTML 1KB] [ PDF 1382KB] ( 2076 )
588 Strategic thinking on exploitation of small hydropower in China from learning 27 countries of European Union
Fang Yujian, Zhang Jinfeng,, Yuan Shouqi
The status and strategic plan of small hydropower development in the 27 Countries of European Union(EU), the composition of renewable energy resources and distributed power generation within EU, and the contributions of European Small Hydropower Association in promoting small hydropower development are introduced and analyzed in detail. According to the 12th 5-year-plan on national hydropower and new rural electrification issued by the Ministry of Water Resources of China, the small hydropower exploitation status and strategic planning are described and argued. A few outstanding issues in development of small and micro hydropower, such as confused rights and responsibilities, ma-nagement difficulties due to huge number of small hydropower plants, small hydropower development enterprises with poor continuity and unclear future trends, are identified. The problems that small hydropower equipment suppliers encountered, namely low technical level, insufficient technological backup, less funding invested and poor capability doing research and development, unsatisfactory ma-nagement skills and so on, are exposed. Additionally, the full-load hours are shorter per year in small hydropower plants. The problems related to run-off-the-river power plants are analyzed as well. Finally, there are five constructive suggestions proposed, i.e. clearing the rights and responsibilities of small hydropower enterprises to regulate its exploitation and operation, setting up a comprehensive management and development committee for small watersheds to manage many small hydropower plants as groups, tracking international developing trends of small hydropower to make our small hydropower industry bigger and stronger as well as sustainable, establishing "one integrated R&D center, two directions" to promote technology level of small hydro equipment suppliers, extending the full-load hours or equipment utilization efficiency to raise the power generation profits of small hydropower.
2014 Vol. 32 (7): 588-599 [Abstract] ( 2176 ) [HTML 1KB] [ PDF 5168KB] ( 2192 )
600 Numerical simulation and hydrodynamics optimization of direct-drive Francis turbine runner in cooling towers
Chen Yang, Zhou Daqing, Li Lingyu, Chen Shifan
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2014 Vol. 32 (7): 600-605 [Abstract] ( 1971 ) [HTML 1KB] [ PDF 1393KB] ( 1349 )
606 Analysis of characteristics of pressure fluctuation inside submersible mixer
Tian Fei, Shi Weidong, Lu Xining, Zhang Desheng, Lang Tao
For a thorough study on the vibration induced by pressure fluctuation inside a submersible mixer, the unsteady, three-dimensional turbulent flow driven by a specific submersible mixer in a se-wage treatment pool is simulated by using software-Fluent 6.3 and Gambit. The RNG k-ε turbulence model, PISO algorithm, rigid-lid approximation and sliding mesh are adopted in the simulation. The pressure fluctuation characteristics in the impeller of submersible mixer are clarified based on an examination of the unsteady flow field features in the impeller and pool. It is shown that the flow of the fluid inside the impeller and in the vicinity of impeller exhibits an obvious periodic feature, i.e. the fluid domain with high pressure and low relative velocity and the domain with low pressure but high relative velocity vary periodically with the rotating impeller. The pressure fluctuation frequency of the fluid in the impeller entrance, outlet and inside the impeller is closely related to impeller rotational frequency, and the predominant frequency is 2 times the blade passing frequency. The results may provide a reference for application of the mixers.
2014 Vol. 32 (7): 606-610 [Abstract] ( 1792 ) [HTML 1KB] [ PDF 1563KB] ( 1776 )
611 Analysis of flow in side chamber and path of comb-labyrinth seal in Francis turbine at different Reynolds numbers
Wang Wenquan, Yin Rui, Yan Yan
Since there is a large difference in geometrical scale in the side chamber and comb-labyrinth seal of Francis turbine runner, the fractional step method is used to solve the unsteady, three-dimensional, incompressible Navier-Stokes equations for the flow in the chamber and tortuous path of the seal. In order to capture vortex structure more exactly, the hexahedral mesh with refinement near the wall boundaries are adopted. The Quick upwind and second-order central difference schemes are selected for convection and diffusion terms, respectively. The velocity and vorticity profiles in the path of labyrinth seal are obtained at different Reynolds numbers; meanwhile the pressure distribution in the side chamber, axial thrust on the runner and torque on the shaft are estimated. It is turned out that a vortex structure can be developed as soon as the fluid enters the path of the labyrinth seal to consume a certain amount of kinetic energy, and a pressure drop is established to prevent the leakage. Note that the vortex structure is largely affected by Reynolds number. The results may be helpful in understan-ding the physical mechanism of complex flow in the path of comb-labyrinth seal and the influence of the seal on rotordynamics of Francis turbine. 
2014 Vol. 32 (7): 611-616 [Abstract] ( 1838 ) [HTML 1KB] [ PDF 1563KB] ( 2012 )
617 Effects of groundwater depth on maize growth and water use efficiency
Liu Zhandong, Liu Zugui, Yu Jianhe, Nan Jiqin, Qin Anzhen, Xiao Junfu
Groundwater depth has a significant impact on crop growth, development and water use efficiency. A typical summer maize crop is taken as trial object, six(0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 m)groundwater depths are set up to investigate its effects on morphological indices, grain yield, water consumption, and groundwater recharge during different growth stages of the summer maize, the diffe-rences in water use efficiency are analyzed too.It is turned out that the groundwater depth shows a little effect on plant height, however, either a too shallow or too deep groundwater level can significantly inhibit the increase in leaf-area index(LAI)and growth of stem diameter(P<0.05). The maximum LAI and the biggest stem diameter are reached at 0.4 m groundwater depth. As the crops grow, number of roots and root dry weight decrease initially, and then increase with increasing groundwater depth, a minimum is achievable at a certain depth. Bleeding sap of root system per plant rises with increasing groundwater depth before the grain-fill stage, but the bleeding sap is less affected by ground-water depth when the grain fill stage gets started. Furthermore, the groundwater depth also influences ear size, barren tip length, grain number per ear, 100-grain weight, and grain yield substantially. It is observed that 0.53 m groundwater depth is optimal for achieving the maximum maize yield. At crop growth stages, soil water content in 0-80 cm soil layers is decreased with increasing groundwater depth, but the water content at the same groundwater depth exhibits a slight change during various growth stages. The total water consumption, water consumption at each growth stage, and water consumption intensity are reduced linearly with increasing groundwater depth; their regression equations with groundwater depth have reached extreme significance level(P<0.01). Likewise, the total groundwater recharge, groundwater recharge at each growth stage, and groundwater recharge intensity are also linearly decreased with increasing groundwater depth, the regression equations are at extreme significance level(P<0.01)as well. Water use efficiency increases with increasing groundwater depth, and reaches the maximum at 1.2 m depth. The results have practical significance for utilization and assessment of groundwater resources, and formulation of optimal irrigation scheduling to achieve high maize yield in farm lands on the hills around River Yangtze and Huai.
2014 Vol. 32 (7): 617-624 [Abstract] ( 1604 ) [HTML 1KB] [ PDF 1346KB] ( 1592 )
625 Study on translocating speed and water distribution uniformity of lightweight lateral move irrigation system
Zhang Yisheng,, Zhu Delan,, Zhang Lin, Gong Xinghui,
In order to identify a reasonable translocating speed of lateral irrigation system and effects of water distribution uniformity on soil water content under a low operating pressure, a relationship between operating pressure and translocating speed at a rated irrigation quota is established through indoor and field experiments by employing the lightweight lateral move irrigation system developed in house, in addition, the variations in water distribution and uniformity as well as soil water content uniformity are analyzed in terms of time. It is clear that the relationship can estimate the translocating speed and operating pressure accurately under a given irrigation quota. The lowest and highest translocating speeds are 17.27, 58.65 m/h under 40-120 kPa operating pressure at 10, 15 and 20 mm irrigation quotas, respectively. An increasing operating pressure can improve water distribution uniformity slightly, for instance the uniformity is 0.696 for 40 kPa operating pressure, but for 60-120 kPa pressure it is increased to 0.731-0.788. Note that the water distribution uniformity is quite better in soil than on land surface at low working pressure. Particularly, the soil water content uniformity is 0.906 after 6 h since irrigation, but it can be as high as 0.953 after 24 h under 40 kPa working pressure. This suggests that the design specification on water distribution uniformity can be loosened properly by moving the irrigation system faster to reduce operating cost and energy consumption. 
2014 Vol. 32 (7): 625-630 [Abstract] ( 1778 ) [HTML 1KB] [ PDF 1375KB] ( 1955 )
631 Evaluating projection pursuit model of irrigation district based on ant colony optimization algorithm for continuous domains
Fei Liangjun, Sun Jie,, Ren Changjiang, Xie Fang
There exist two limitations in ant colony optimization algorithm for continuous domains, namely the model parameters must be in the range of 0 to 1 and the algorithm fails to search a potential optimal function value between nodes. Therefore two updates are proposed to remove the limitations,(1)modify the decoding formula to expand the parameter domain into the whole real number domain,(2)use a 3D table-T(m×d+m+1,10)to search an optimum function, and 10×m-10 node ci-ties are reduced compared with the original 2D table-T(m,d+2,10). In the improved algorithm, the number of nodes has been reduced and invalid search paths have been removed, causing greatly shortened computational time and improved accuracy. In addition, the improved algorithm is introduced into the projection pursuit model and the weight coefficients of various indices are obtained based on Jiaokou Irrigation District of River Wei in Guanzhong Plan of Shanxi Province. It was turned out that the comprehensive projections are 1.353 1(1999), 2.074 7(2005), 2.502 2(2008)and 2.403 9(2011), and the operation situation of the district falls into fair, fair, good and good category, respectively in those years. Except 2011, the district performed better and better as time went on. These evaluating results match the actual situation quite well.
2014 Vol. 32 (7): 631-636 [Abstract] ( 1314 ) [HTML 1KB] [ PDF 1367KB] ( 1453 )
637 Wireless sensor network-based viticulture environmental monitoring system
Li Jianqi, Kong Lingshuang, Wang Fuwen, Li Xiaofeng, Cao Binfang
In order to realize the key environmental parameters in viticulture to be monitored and reduce the labor intensity of agricultural workers in Southern China, a monitoring system is put forward with combination of the layered wireless sensor network(WSN)and Wi-Fi technique. The CC2530 wireless transmitter chip is used in the system as the core to construct wireless data acquisition nodes, the corresponding hardware design is carried out and a real-time collection is completed for the key environmental parameters, such as temperature and humidity of air and soil, CO2 content and so on. In order to locate network nodes, a network structure is adopted based on the virtual network cells, further the cluster head election mechanism for the cells is optimized and the multihop transmission of cluster head is achieved; the error detection and correction mechanism are utilized as well. Compared with the traditional LEACH-C clustering algorithm, the improved algorithm has a nearly 22% enhanced network energy efficiency. The system can monitor a wide range of land in viticulture because multiple assess points are allowable in Wi-Fi technique, also it can retransmit data automatically once any errors occur. This PC monitoring system is easily operated and can monitor any changes in the parameters in grape growth stages real-timely. Importantly, it can trigger an error alarm and indicate expected operations according to the expert experience database implemented. It is shown that the system is reliable in operation and can satisfy the needs of viticulture management.
2014 Vol. 32 (7): 637-644 [Abstract] ( 1359 ) [HTML 1KB] [ PDF 1466KB] ( 1648 )
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