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Journal of Drainage and Irrigation Machinery Engin
 
2014 Vol.32 Issue.5
Published 2014-05-25
article
Article
369
2014 Vol. 32 (5): 369-372 [Abstract] ( 1923 ) [HTML 1KB] [ PDF 2671KB] ( 1673 )
373 Influence of operational condition and tip clearance size on trajectory of tip leakage vortex
Shi Weidong, Shao Peipei, Zhang Desheng, Wu Suqing, Li Tongtong
Based on the SST k-ω turbulence model and vortex intensity method, the flow through the impeller tip and tip leakage vortex trajectory in a model axial-flow pump were simulated numerically. The influence of operational condition and tip clearance size on the trajectory was analyzed. It is shown that the starting point of leakage vortex core moves to the middle portion of blade from the blade leading edge gradually with increasing flow rate. The relative flow direction in the impeller passage is deflected and the trajectory of tip leakage vortex is altered accordingly under the entrainment induced by the primary flow with increasing flow rate as well. Note that the slope of the vortex core trajectory also gets enlarged by the primary flow. The rollup of leakage vortex is enhanced and the affected region is expanded, the starting point of the vortex also moves from the leading edge to the trailing edge, and the static pressure in the vortex core is decreased gradually, causing a risk of cavitation with increasing tip clearance size. A positive head curve appears at around 0.9 times the design flow rate under a tip clearance as large as 1.5 mm, suggesting the tip leakage vortex can influence the instability of head curve significantly.
2014 Vol. 32 (5): 373-377 [Abstract] ( 1820 ) [HTML 1KB] [ PDF 2382KB] ( 1578 )
378 Effect of guide vane inlet and outlet angles on performance of energy recovery turbines
Shi Fengxia, Yang Junhu, Wang Xiaohui
Four energy recovery hydraulic turbine models were designed according to different combinations of guide vane inlet and outlet angles based on an existing single-stage centrifugal volute pump, and the fluid flows in them were simulated numerically by using software Fluent 6.3. It was shown that at the same flow rate all the turbine efficiency and head were declined markedly with increasing inlet angle; at the best efficiency point(BEP), however, the hydraulic efficiency of model A was 7% hi-gher than that of model D. For the same inlet angle, once the outlet angle was greater than the inlet angle, the circulation at the guide vane outlet was decreased and the efficiency of turbine was reduced; otherwise, the efficiency was raised. With increasing inlet and outlet angles, BEP was moved to a higher flow rate, and the pressure distribution in the impeller was distributed more non-uniformly. Therefore, the inlet angle plays a crucial role in determining turbine performance and a guide vane with an inlet angle larger than the outlet angle is beneficial to turbine efficiency. Especially, for a turbine in which the basic geometrical parameters of all the hydraulic components except the guide vane were fixed, there is an optimum combination between inlet and outlet angles of the guide vane. This result can provide some theoretical basis for further study on energy recovery hydraulic turbines.
2014 Vol. 32 (5): 378-381 [Abstract] ( 2066 ) [HTML 1KB] [ PDF 1631KB] ( 1628 )
382 Development of 150QJS20 stainless steel casting multistage deep-well pump
Zhang Qihua, Xu Yuanhui, Xu Yan, Ma Dongqi, Zheng Wei, Lian Songjin , Lu Weigang
Stainless steel casting multistage deep-well pumps have been extensively used in some specific applications where excellent corrosion- and wear-resistance as well as long life-span are highly desirable. Because of stainless steel investment casting multistage deep-well pumps with high cost, they are targeted to mid- or high-end users. By utilizing existing stainless steel casting techniques, a type 150QJS20 multistage deep-well pump was developed. Four kinds of techniques used in the development process are as follows:(1)the guide vane was cast by using outward rather than inward flanging technique to overcome the difficulty in cleaning sand from castings;(2)the inflow diffuser was adopted in this design to reduce manufacturing cost and shorten the axial length of di-ffuser, and eventually to improve the pump operation reliability;(3)tie-bolts are used to assemble the pump, and connection between stages is realized by spigots filled with O-shape seals, causing a more compact pump construction, convenient transportation and easy maintenance;(4)major accessories are interchangeable in the same series to reduce manufacturing cost. A prototype pump was built and its performance was measured, showing its efficiency being comparable with the international standard level and a greatly improved stage head. Compared with the traditional multistage deep-well pumps, the new type pump has a more compact configuration and lighter weight. Therefore the success in development of 150QJS20 pump can provide useful experience for development of other similar stainless steel casting pumps for mid- and high-end users.
2014 Vol. 32 (5): 382-387 [Abstract] ( 1775 ) [HTML 1KB] [ PDF 1575KB] ( 1421 )
388 Structural design and performance test of serial-three-chamber piezoelectric pump
Sun Xiaofeng, Jiang Delong, Yang Zhigang
To explore effects of number of chambers on performance of piezoelectric pump, a new structure, e.g. serial-three-chamber piezoelectric pump was designed and fabricated by using three passive check valves based on the working principle of piezoelectric pump with more chambers. A series of experiments were performed on the pump with water under different working conditions and the experimental results were compared with those of a serial-double-chamber piezoelectric pump. The best working condition was studied analytically and validated experimentally for the designed pump. It was turned out that the flow rate of the three-chamber pump was lower than that of the double-chamber one, the flow rate of the former was 0.7 times the latter, but the output pressure of the former was as high as appro-ximate 1.5 times that of the latter. This suggests that increasing number of chambers can improve the output pressure, while it can reduce output flow rate as well. For the designed pump, the 860 mL/min maximal output flow rate and 80 kPa output pressure can be achieved under the 110 V AC driving voltage.
2014 Vol. 32 (5): 388-392 [Abstract] ( 1360 ) [HTML 1KB] [ PDF 1555KB] ( 1360 )
393 Numerical simulation of mechanism for sill rectifying flow in pumping station intake
Luo Can, Cheng Li, Liu Chao
To eliminate vortices in a pumping station intake, the flow patterns in the intakes without and with a sill in their bottom were simulated based on the incompressible N-S equations, Realizable k-ε turbulence model and SIMPLE algorithm. It was shown that there were large recirculation zones in both sides of the intake without a sill and the main stream was obviously off the central line and shif-ted to one side, causing unbalance flow rate in both sides. For the intakes with a sill, the large recirculation zones still existed if the sill was placed further away from the intake outlet and the main stream kept to be shifted one side considerably as well. If the sill was moved to the intake outlet closer, the vortices shed from the sill could disturb the flow pattern near the outlet straightforward. When the sill was located at the distance(7-10)D away from the intake outlet, then the flow pattern was improved significantly, leading to the flow rate distributed uniformly into each pump suction pipe. The downstream recirculation zone at the bottom of the sill kept shrunk until it disappeared at all with increasing height of the sill, eventually, an upstream recirculation zone occurred. It was illustrated that a better flow pattern was achievable with the height of approximate 0.3H′. Note that the top width of sill had a less effect on the flow pattern. The predicted flow patterns were in good agreement with the measurements. These outcomes can be useful for flow pattern improvement in pumping station intakes with expanding width towards the intake outlet, but also has practical significance.
2014 Vol. 32 (5): 393-398 [Abstract] ( 1528 ) [HTML 1KB] [ PDF 6976KB] ( 1356 )
399 Short-term hydrodynamic features of Chinese sturgeon spawning ground under reservoir regulation conditions
Mao Jingqiao,, Li Zhi, Dai Huichao,, Ke Yun
The water level of Three Gorges Reservoir(TGR)reached to 175 meters in 2010, indicating this hydropower project had started its normal operation. Chinese sturgeon spawning ground is located at downstream of Gezhouba reservoir immediately and the water level of the ground is affected by regulation of both reservoirs. Since hydrodynamics in the ground can play a crucial role in multiplication of Chinese sturgeon, effects of regulation of both reservoirs on the hydrodynamic characteristics of Chinese sturgeon spawning ground are investigated to explore its suitability for reservoir regulation of a hydraulic project. A three-dimensional hydrodynamic model is built for the Chinese sturgeon spawning ground from Gezhouba to Yichang reach. The short-term hydrodynamic characteristics of the spawning ground are studied by simulation method at two water levels at which two spawning events were observed in 2011. It is shown that the bottom layer flow, which is directly related to multiplication of Chinese sturgeon, is smooth and stable, but there is local turbulence in two streams mixing regions and in bumpy areas of the bed. The stream velocity is varied from 0.8 to 1.4 m/s; a higher velocity is observed in the downstream of Dajiang Power Station and Erjiang Power Station, but the highest velocity is found in the downstream of at Erjiang Power Station. The fluid domains with a stream velocity suitable for Chinese sturgeon spawning are ranged respectively from the end of the training levee in the downstream of Dajiang Power Station to the first 1/3 portion of the central separation levee in the river, and from the end of the central separation levee to 700 m extension in the downstream of the separation levee.
2014 Vol. 32 (5): 399-403 [Abstract] ( 1532 ) [HTML 1KB] [ PDF 1742KB] ( 1518 )
404 Statistical method for analyzing shaft orbit of hydro-generator
Fu Jing, Zhang Fei, Li Bing
Because the methods for analyzing the shaft orbit of hydro-generator are very less presently, the shaft orbit cannot be monitored effectively in a long period of time in operation. In the paper, a few parameters, namely standard deviation, coefficient of variation, area and normalized area are defined for the shaft orbit based on statistic method, then the shaft orbits of the hydro-generator in a hydro-power plant were studied under various operational conditions at a fixed head by the parameters. It was shown that the clarity of shaft orbit can be described by the defined standard deviation and coefficient of variation. The influence of hydraulic parameters under various operational conditions on shaft orbit can be indicated by the coefficient of variation.Under the same working condition,the normalized areas measured at different locations have the same order and identical trend, so that effects of monitoring locations and bearing clearance adjustment etc on the orbit have been eliminated, eventually a general assessment of the shaft orbit can be made. The standard deviation and normalized area are sensitive to change in the shaft orbit caused from the variable operating conditions of a hydro-generator unit, thus they can be used in shaft orbit on-line monitoring of a hydro-generator unit.
2014 Vol. 32 (5): 404-409 [Abstract] ( 1430 ) [HTML 1KB] [ PDF 3732KB] ( 1538 )
410 Optimization of circulating water system based on LSSVM and SA-BBO algorithms
Zhang Lei, Wei Long, Ye Yalan, Qiao Zongliang, Xu Zhigao
The optimization of circulating water system in a thermal power plant holds a great significance for determining the optimum vacuum degree of a condenser and improving total efficiency of the plant to save energy. Therefore, a prediction model for steam turbine output power is established based on least squares support vector machine(LSSVM)by considering the circulating water system of two 600 MW steam turbine units in a particular thermal power plant. There is no local minimum in the model and excellent prediction results can be achieved for a variety of problems. Then, an optimization model for the vacuum degree in the condenser is developed based on maximization of the profit by ta-king circulating pump shaft power, turbine power increment, the price difference of coal and electricity on the market into account. Initially, the recorded operational parameters of the plant over a period of time are input into the model, a data pre-processing is conducted on the parameters and their stability is identified. Then the vacuum degree is optimized by means of the simulated annealing and biogeography-based optimization algorithms(SA-BBO)to obtain the optimum vacuum degree, best combination of the operational parameters of the condenser and circulating pump under various operating conditions. The optimized results have been made into an optimized combinations chart to guide the operation and regulation of steam turbines.
2014 Vol. 32 (5): 410-415 [Abstract] ( 1739 ) [HTML 1KB] [ PDF 1481KB] ( 1886 )
416 Energy loss-based computational method for moment arm of frictional resistance in ball bearings
Gao Shizhao, Xu Guobin
In order to solve the problems in computational method for moment arm of friction resistance in the ball bearings which make a hydraulic gate supported and movable, the rolling friction in the ball bearings is simplified from energy loss point of view. Firstly, the rolling friction is due to micro-sliding friction, and the micro-sliding contact surfaces are approximately circular area, then the stress distribution can be obtained by superimposing two similar Hertz stress formulas to meet the contact boundary condition. Secondly, the rolling friction is caused from elastic-hysteresis which is related to the plastic effect in the material of balls. A bearing ball can be deformed by an external load, during such a deformation, the structural damping, which is caused from the internal friction in the material will consume a part of energy, leads to the elastic-hysteresis. The elastic-hysteresis is proportional to strain. Thirdly, the rolling friction is caused from an adhesion-effect that is relevant to surface energy. When a ball is rolling in two bearing rings, it needs to overcome the surface energy; eventually, a part of e-nergy is consumed as well, causing the adhesive effect occurs. Finally, a few materials frequently used as in ball bearings, such as 440C stainless steel, silicon nitride, silicon carbide and tungsten carbide etc, were involved in the calculation of moment arm of friction resistance. It was found that the moment arm is proportional to slip ratio, and inversely proportional to load.
2014 Vol. 32 (5): 416-421 [Abstract] ( 1153 ) [HTML 1KB] [ PDF 1510KB] ( 1850 )
422 Numerical analysis of unsynchronizing motion of ring inlet valve in reciprocating compressor
Zhang Manlai, Zhang Qin, Liao Ruiquan, Li Yong
In order to clarify motion characteristics of the ring inlet valve in a reciprocating compressor the expansion or suction process in the compressor was simulated with CFD approach by exploring the unsynchronizing motion of valve plates. During the unsteady flow simulations, a user defined C subroutine was composed to involve the motion functions of piston and four valve plates, displacement boun-dary conditions, impact criteria between valve plate and seat or lift limiter, displacement constrains for impact and rebound velocity boundary, eventually the displacement increments of four valve plates were determined at the end of each time step. Besides, the moving mesh technique was applied to update the mesh to realize a dynamic simulation of motion of various valve plates. Based on the mesh-independent feature identified, the effects of spring stiffness and crank shaft speed on the motion of the four valve plates and the flow rate through them were investigated. The simulated results show that the unsynchronizing motion of valve plates magnifies itself by showing different opening and closing angles from inner to outer of the plates. With increasing spring stiffness and decreasing crankshaft speed, the unsynchronizing motion among four valve plates becomes more and more evident. Additionally, the inner or the first valve plate flutters initially at the speed of 300 r/min, however, when the spring stiffness is increased to 6 000 N/m from 4 000 N/m, the second valve plate starts to flutter, and the flow rate is reduced to 0.8 times the flow rate without unsynchronizing motion. This suggests that the unsynchronizing motion must be considered when a flow rate is under determination.
2014 Vol. 32 (5): 422-428 [Abstract] ( 1258 ) [HTML 1KB] [ PDF 2432KB] ( 1497 )
429 Finite element analysis of arm of SR100 vertical impact sprinkler
Li Hong, Liu Zhenchao, Tang Pan, Wang Chao
The arm of a vertical impact sprinkler is one main part for bearing a load. The structure of the arm was simplified and the forces acting on it were calculated based on an analysis of the forces applied on the deflector in the sprinkler. Besides, the hydraulic force generated by a water jet impacting on the arm was figured out by using a theoretical analysis. Modal, static, and fatigue analyses for the arm were conducted by using finite element method on ANSYS Workbench. Eventually, the natural frequency and vibration mode of the arm at each modal are obtained, showing the vibration modes are mainly presented by bending, twisting and local deformations. When the arm works under the frequen-cy less than 41.785 Hz, its vibration modes are usually in the first order. A stress distribution in the arm is generated in the static analysis, and a stress concentration is found in the position where the deflector is installed. In the fatigue analysis, it is shown that the safety factor varies greatly across the arm and the minimum factor is found to be 1.229 1 in front end of the arm. This means that crack or fracture can occur easily in that portion in the arm in a long-term operation, and the strength of that portion should be strengthened. In order to improve the stability and reliability of the arm of sprinkler in operation, the local configuration with stress concentration in the arm may need to be redesigned or the arm may adopt a material with even stronger strength.
2014 Vol. 32 (5): 429-434 [Abstract] ( 1707 ) [HTML 1KB] [ PDF 1790KB] ( 1704 )
435 Temporal and spatial variation of grain production water footprint and net virtual water export in Hetao Irrigation District
Liu Jing,,, Wu Pute,,,, Wang Yubao,, Zhao Xining,,, Sun Shikun,,, Zhang Xiaohong
Properly evaluating utilization of water resources in an irrigation district is of great significance for improvement of the existing water resources management; thus two concepts, namely water footprint and virtual water are introduced and their temporal and spatial variations are analyzed in Hetao Irrigation District from 1960 to 2008. The analysis is focused on green and blue water and based on two indexes, such as the ratio of water for grain production to totally consumed water, R1, and the ratio of virtual water for grain export to water for grain production, R2. The results show that the grain water footprint is decreased to 1.63?109 m3 in 2008 from 3.53?109 m3 in 1960, and the net virtual water export demonstrates a decreasing trend in 2000s. Besides, the blue water accounts for 90% of both the grain water footprint and net virtual water export. The grain water footprint and net virtual water export in the central irrigation district(Hanghou, Linhe and Wuyuan)are larger than those in the other areas(Dengkou and Qianqi). Further, R1 is decreased at an averaged rate of 1.07% during the studied period, while R2 is showed a fluctuating rise. The value of R2 is decreased in 2000s, but it still is as high as 76.22% in 2008. In future, water use efficiency of green and blue water should be improved in Hetao Irrigation District. This study can provide a theoretical basis for policy-making in water resources management and sustainable development of an irrigation district.
2014 Vol. 32 (5): 435-440 [Abstract] ( 1835 ) [HTML 1KB] [ PDF 4080KB] ( 1595 )
441 Water-saving irrigation scheduling for transplanted cotton following wheat harvest
Liu Hao, Zhang Jiyang, Sun Jingsheng, Shen Xiaojun, Zhang Junpeng, Ning Huifeng
To develop a suitable irrigation scheduling for transplanted cotton following wheat harvest, an experiment was conducted in non-weighting lysimeters to study effects of frequency of watering on plant growth, boll development, seed cotton yield, fiber quality and water use efficiency in 2011. The results showed that the watering at germination stage and early stage of leaf blade formation to promote seedling growth(scheduling CT1)can enhance plant growth, but not significantly increase seed cotton yield and fiber quality, resulting in the lowest gin turnout and water use efficiency. If there are irrigations after cotton seedlings transplanted only, the forthcoming rainwater(scheduling CT4)can not meet water requirement for plant growth, in consequence normal development of both bud and boll is restrained, causing a lower seed cotton yield and poor fiber quality. Compared with scheduling CT1, the irrigation scheduling in which watering is taken place in squaring stage doesn't reduce seed cotton yield and fiber quality, but also leads to a 8.5% increased gin turnout and a 30.8% improved water use efficiency. Eventually, both water-saving and high yield can be achieved simultaneously for transplanted cotton following wheat harvest.
2014 Vol. 32 (5): 441-447 [Abstract] ( 1375 ) [HTML 1KB] [ PDF 1532KB] ( 1461 )
448 Effects of irrigation with saline water on growth and water use efficiency of film-mulched cotton plant
Zhang Junpeng,, Feng Di, Cao Caiyun, Sun Jingsheng,, Sun Chitao, Zheng Chunlian, Liu Hao,
In order to reveal the characteristics in growth and development of a cotton plant for response to irrigation with saline water, effects of water salinity on germination, plant height, leaf area, number of fruit branches, aboveground biomass, yield, water consumption and water use efficiency etc were studied for cotton plants by means of small-scale field trial. The results showed that germination rate and qualified seedling rate decreased with increasing salinity of water, and there is statistical significance between the 5 and 7 g/L total dissolved solid(TDS)salinity treatments and the control group, but not for 3 g/L TDS treatment. In the case of whole gap filling through transplanting plants, the saline water exhibited an inhibitory effect on the morphological indices of growth and development of cotton plants, and the higher the water salinity, the stronger the effect. Particularly, the plant height, leaf area and aboveground biomass were affected most significantly by the salinity in bud stage, but gradually less influenced after boll stage. Additionally, the number of fruit branches and boll growth were decreasingly affected with growth of cotton plants. There was no statistical significance in the water consumption among various treatments. The cotton seed yield and water use efficiency were decreased gradually in 3, 1, 5, 7 g/L treatments, among which there is statistical significance between the 7 g/L treatment and the control group. Compared with the initial salt content in 0-40 cm soil la-yer, after the irrigation trails the salt content in the soil layer remained unchanged in 1 g/L and 3 g/L treatments, but was increased in 5 and 7 g/L treatments. These results can provide an important reference for productive use of saline water.
2014 Vol. 32 (5): 448-455 [Abstract] ( 1724 ) [HTML 1KB] [ PDF 1442KB] ( 1475 )
456 Design and experiment on fertigation plunger pump in center pivot irrigation system
Yan Haijun, Wang Zhipeng, Ma Kai
Fertigation technology for center pivot irrigation systems has increasingly become a research focus in precision agriculture inside and outside China. Fertigation equipment with high working pre-ssure and low but stable flow rate is the key factor to guarantee high fertigation uniformity. In order to meet the requirement of center pivot irrigation systems a double-cylinder plunger pump including liquid ends, drive ends, pistons, seals, AC motor and so on was designed by taking crop fertilization characteristics into account. The design flow rate per cylinder is 150 L/h and the maximum working pressure is 1.0 MPa. Meanwhile 100 h durability test, stroke regulation test(20%-100% stroke)and frequency conversion test(30-50 Hz)on a prototype of the pump were conducted. It was showed that the discharge of the pump decreases with increasing discharge pressure and all the variation coefficients of discharge within 100 h are smaller than 5% under various discharge pressures. The measured discharge is almost the same as the theoretical one, and the maximum error between them is just 7.5% at a 60% stroke. Additionally, the pump discharge rises linearly with AC motor frequency. Clearly, the pump discharge can be adjusted by changing the plunger stroke and altering the AC motor frequency to expand the range of pump discharge. The developed plunger pump is applicable for a fertigation system, such as the center pivot irrigation system to realize precision fertilization.
2014 Vol. 32 (5): 456-460 [Abstract] ( 1705 ) [HTML 1KB] [ PDF 1608KB] ( 1588 )
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