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Journal of Drainage and Irrigation Machinery Engin
 
2012 Vol.30 Issue.3
Published 2012-04-10
article
Article
249 Field measurement of water hammer and signal analysis at pump stop due to power failure in long watersupply pipeline
LIU Mei-Qing, LIANG Xing, LIU Zhi-Yong, LIN Qi, WU Yuan-Wei
The method of maximum entropy estimation was applied to analyze the transient pressure, rotational speed and discharge signals which were measured and recorded in a pump station for a pump at pump stop caused from power failure and to identify their timefrequency features. Before that, the wavelet packet theory was used to denoise the measured signals. It was found that the main pollutant in the signals was the noises with a higher than 50 Hz frequency. Then, both the wavelet pocket method and the fast Fourier transform (FFT) were used to remove the pollution. At last, the simulated water hammer signals were compared with the measured ones denoised to confirm effect of the surge tank combined with air valves on water hammer prevention. The results show that even waveforms of the two denoised signals respectively by the wavelet pocket method and FFT are similar. The latter method considerably reduces the useful information in pressure peaks, while the wavelet packet theory can eliminate noises effectively and allow the denoised signal to have a similarity to the original one. A surge tank with airvalves takes a substantial effect on preventing from water hammer. The column separation model can correctly predict the maximum values of pressure, backflow discharge in a pipeline and the reverse rotational speed of pump. Those data provide evidence for pumping system safety assessment. Unfortunate, the existing models fails to accurately simulate the attenuation process of water hammer wave, thus more precise models are needed.
2012 Vol. 30 (3): 249-253 [Abstract] ( 2551 ) [HTML 1KB] [ PDF 1936KB] ( 2591 )
254 Static analysis on rotor of type ZJ-200-25 screw centrifugal pump
Abstract: In order to investigate the vibration characteristics of impeller and pump shaft of screw centrifugal pump in operation, the type ZJ-200-25 screw centrifugal pump with double blade was chosen as the study model. A threedimensional mathematical model of fluid flow in the pump was established and the flow was simulated numerically under the design condition. A finite element model for the rotor system of the pump was generated as well. The statics and mode analysis were conducted under the flow field pressure distribution in pump chambers when the rotor was prestressed. The 1st to 6th order natural frequencies and the modes of vibration of the rotor system were obtained. It was showed that the strength of the rotor completely satisfies the design requirement  and the maximum stress points were located at the root of blades and the shoulder of shaft. The rotor was rigid, and a natural frequency of rotor system was close to the blade passing frequency of impeller, thus the rotor system design was unreasonable. Therefore, it is necessary to optimize the structure of rotor by altering the position of bearings, resizing shaft diameter and changing material. In that cases, the natural frequency of the rotor will be changed and may be far away from the blade passing frequency.
2012 Vol. 30 (3): 254-259 [Abstract] ( 3366 ) [HTML 1KB] [ PDF 2036KB] ( 2892 )
260 Influence of gap on pressure pulsation and radial force of centrifugal pumps
Shi-Wei-Dong, ZHANG Lei, CHEN Bin, JIANG Ting, ZHANG Hua
Abstract: The unsteady flow in centrifugal pumps induces a pulsation in fluid pressure inside the volute channel and imposes a radial force on the volute wall too. Thus effect of the gap between the volute tongue and impeller outlet on them was tackled by means of a nonoverload submersible sewage pump with extremely thickenedblades. Three pump models with different base circle diameters, such as 390, 435 and 460 mm were designed. The unsteady flow fields in those models were obtained numerically based on the standard k-ε turbulence model and SIMPLE algorithm. The characteristics of pressure pulsation on the tongue and the radial force on the wall against gap were obtained. The results showed that the pressure pulsation and the radial force presented an obvious periodicity due to the rotorstator interaction. The dominant frequency of pressure pulsation at the monitor points in the volute was the blade passing frequency. At the same flow rate, the intensity and amplitude of pressure pulsation at the dominant frequency were increased with decreasing gap.The timeaveraged radial force imposed on the wall was decreased and then increased with increasing flow rate.Compared with the original pump model, the averaged radial force in the new models was increased regardless of gap at the same flow rate.
2012 Vol. 30 (3): 260-264 [Abstract] ( 3112 ) [HTML 1KB] [ PDF 2234KB] ( 2819 )
265 Design program for axial flow impeller blade based on Joukowski transform
YAN Jing, WANG Tao, XIAO Guo-Hua, LI Yu
To improve the performance of axial flow pumps and upgrade the design principle of the pump blades, a new approach for calculating the blade camber was proposed here. The principle and procedure that the approach designs the blades of axial flow impeller were presented based on the Joukowski transform. The geometrical properties of an eccentric circular cylinder, which was formed by the superposition of three twodimensional potential flows—a doublet, a uniform plane flow and a point vortex, fluid dynamics around it and the position of stagnation point on it were described. Further, the geometrical properties of a circle arc, which was derived from Joukowski transform, and the fluid dynamics around it were discussed as well. Based on the above achievements, the method and producer for determining the direction and shape of a blade camber were developed in terms of the specified circulation and freestream velocity. The method and producer proposed here are completely different from the traditional ones, such as the singularity method, streamline method and so on for axial flow pump blades. The new approach is easily handled by pump engineers and it is hopeful that the approach can offer a new way for designing axial flow pump blades for the engineers.
2012 Vol. 30 (3): 265-269 [Abstract] ( 2925 ) [HTML 1KB] [ PDF 1368KB] ( 3007 )
270 Effect of swept blade on hump and cavitation characteristics of axial flow pump
LIU Zhu-Qing, XIAO Ruo-Fu, Lv Teng-Fei , LI Shu-Lin
A swept blade was designed based on changing the stacking line in the meridional plane of an axial flow pump impeller. The high speed fuel axial flow pumps, with swept blades and datum blades respectively, were simulated in the overall operation by the code of computational fluid dynamics (CFD) and the overall efficiency and pump head performance curves were obtained. Using the full cavitation model, the cavitation performances of pumps were predicted under the designed point condition and near stall point condition to investigate the effects of swept blade on the cavitation performance and distribution of pressure on blade surfaces of an axial flow pump. According to the numerical results, the swept blade changes the hump characteristic of the axial flow pump, controls the onset and growth of the secondary flows, and recovers the lowenergy fluid on the endwalls. Therefore, the stability of operation in the hump zones is improved. Near stall point condition, the swept blade improves the cavitation characteristic of the pump, changes the pressure distribution on the impeller inlet, and avoids the separated flow on the endwalls. While under the design point condition, the swept blade reduces the cavitation characteristic, the blade surface pressure distribution also presents the pressure difference of the datum blade is higher than the swept blade, resulting in the ability of doing work of the former is better than the latter.
2012 Vol. 30 (3): 270-273 [Abstract] ( 2960 ) [HTML 1KB] [ PDF 1805KB] ( 2625 )
274 Numerical calculation of whole and non whole flow field in centrifugal pumps
Based on the whole and nonwhole flow domain methods, the influence of flow domain on the numerical results in centrifugal pumps was investigated by calculating threedimensional steady incompressible turbulent flows. The standard k-ε turbulence model and virtual block technology were also adopted. The internal flow fields and hydraulic performance of five centrifugal pumps with different specific speeds were calculated at the design conditions. Also, the hydraulic performance obtained was compared with the test. It is observed that the influence of flow domain is remarkable. The whole flow domain method shows a higher accuracy rather than the nonwhole flow domain one, for example, the prediction accuracies in head and efficiency are improved by 1.54% and 1.67%, respectively. The static pressure distributions in the impellers obtained by the two methods are basically the same, but those in the volutes are significantly different. The velocity profile in the gap between impeller and volute is layered for the whole domain method. However, it is triangular for the nonwhole domain one. The secondary flow pattern within the crosssections of volute is not completely symmetry. It is believed that the flows in the wearingring gap and the chamber between the impeller and the pump casing, which have been considered in the whole flow domain method, affect the development of that secondary flow.
2012 Vol. 30 (3): 274-278 [Abstract] ( 2964 ) [HTML 1KB] [ PDF 1960KB] ( 2532 )
279 Analysis and test on PZT insulin pump with dualchambers in series
In order to reduce the cost and simplify the structure of insulin pumps, the piezoelectric(PZT) pump was adopted in insulin injection to replace common one equipped with a step motor. The working principle and two operating modes, such as direct and indirect transfusions of insulin were analyzed for PZT insulin pump. The performance of valveless piezoelectric pumps and those with active valve or passive valves was compared; then a PZT pump with dualchambers in series was proposed for insulin injection so as to improve the pump output pressure.A prototype of such a pump was produced and its performance with three different cutoff valves was measured under both direct and indirect transfusion modes. The measured performance parameters included both opening pressure and flow rate. The results show that the indirect transfusion mode exhibits a better flow and pressure performance than the direct transfusion one. The maximum flow rate in indirect mode reaches 810 mL/min when the voltage and frequency of driving signal are 100 V and 210 Hz. The umbrellashape valve gives rise to a higher flow rate.
2012 Vol. 30 (3): 279-282 [Abstract] ( 2639 ) [HTML 1KB] [ PDF 1626KB] ( 2522 )
283 Effect of tip clearance on performance of low specific speed centrifugal pump with semiopen impeller
CUI Bao-Ling, HUANG Da-Gang, SHI Pei-Qi, JIN Qing-Ming
In order to analyze the effects of tip clearance on the flow and performance of low specific speed highspeed centrifugal pump with a semiopen impeller, the inner flow field in a pump with the specific  speed ns=19.3 was numerically simulated based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model at the tip clearances 0.5, 1.1 and 2.5 mm. The performance of the centrifugal pump was measured as well.The results show that the flow in the impeller is improved with a bigger clearance, but the hydraulic loss caused from the circular flow in the impeller at a relatively big clearance is larger than that at a more tight clearance, so the head and efficiency were decreased with increasing tip clearance. Also, the relative velocity and static pressure of fluid in the clearance were reduced at the middle and trailing edge of blade with increasing tip clearance, especially the relative velocity. The static pressure shows a nearly linear relation to radius. The tangential and radial velocity along the axial direction in the impeller passages were lowered with increasing clearance. Comparison of the results simulated with the experimental data suggests CFD method is quite able to simulate a change in the performance due to varying tip clearance.
2012 Vol. 30 (3): 283-288 [Abstract] ( 4219 ) [HTML 1KB] [ PDF 2314KB] ( 2948 )
289 Variable pitch profile equation of screw centrifugal pump
According to the structure characteristics of impeller of a screw centrifugal pump, the streamwise evolutionary pattern of blade pitch was analyzed by applying the theory of relative velocity ratio of liquidsolid twophase flow model for an impeller pump, and then a parametric equation for variablepitch was deduced. For the given hydraulic performance parameters and a volume fraction of the solid phase at the design point, a smooth, threedimensional blade profile could be established through the parametric equations.The water performance of a screw centrifugal pump whose blades were designed in that way was measured, and accordingly its performances of liquidsolid twophase flow were estimated numerically at three volume fractions of 5%, 15% and 25% with a CFD code, respectively. The results show that the pump efficiency for transporting solidliquid twophase medium is better than for transporting water. At the design point, for a given volume fraction of solid phase, the pump efficiency is increased by 8.5%; however, when the volume fraction is different from that given value, the pump efficiency is reduced.Compared with water single phase flow, the pump head of liquidsolid twophase flow is not only decreased, and but also lowered gradually with increasing solidphase concentration.
2012 Vol. 30 (3): 289-294 [Abstract] ( 3677 ) [HTML 1KB] [ PDF 1686KB] ( 2921 )
295 Analysis on  effect of splitter geometrical parameters on performance of centrifugal pump using grey theory
In the research of influence of geometrical parameters of splitter blades on centrifugal pump performance, the regularity of ranking of the parameters and its reliability should be emphasized. Consequently, the comprehensive influence and its regularity of splitter pitch relative to the full length blade β, deflecting angle α, dimensionless inlet diameter   and number of blades Z on the pump head and efficiency is analyzed in detail by using the grey theory. The results of the ranking by which the four geometrical parameters influence the head and efficiency are obtained by means of a lot of calculations. The result showed that the effect of the splitter pitch relative to the full length blade β on the pump head was the largest, the deflecting angle α is the smallest, the dimensionless inlet diameter  and number of blades Z were in between for all the cases. Meanwhile, the effect of D′on the efficiency was the largest, parameter α was the smallest, β and Z were between them. The repeatability of the ranking of splitter blades parameters is good, and the reliability is high. The results may establish an important base for further study on the hydraulic performance and the optimization design of a centrifugal pump with low specific speed.
2012 Vol. 30 (3): 295-299 [Abstract] ( 2364 ) [HTML 1KB] [ PDF 1328KB] ( 2317 )
304 Calculation method for effect of silt sediment to lifting force of radial gate  
In order to estimate the effect of silt sediment on the lifting force of steel radial gate, a calculating formula was proposed. In the formula, the silt deposited in front of the gate was considered to be the Bingham material which consists of coarse and fine particles. Also, the torques due to grillage sediment weight, rotational hinge friction resistance, seal friction resistance, undersuction effect, door weight and additionalweight were torque etc were involved in the formula. The lifting forces applying on the sluicing steel radial gates in the 2nd and 4th HydroPower Station on the River Xi′er were estimated and compared with those measured in the stations. It was shown that in the case of less sediment deposition, the opening and closing torque on a radial gate is mainly decided by the door and additionalweight, but the lifting force caused from the sediment cannot be ignored. It is the sediment that leads to there is a difficulty in opening gate, thus it should be fully taken into account in the gate design and propose a reasonable operation and maintenance plan for the gate to prevent the event that the gate cannot be opened or closed properly. The accuracy of the calculation formula can meet the needs of engineering practice when it is used to calculate the lifting force of a radial gate with deposited silt in front of it.
2012 Vol. 30 (3): 304-308 [Abstract] ( 3144 ) [HTML 1KB] [ PDF 1374KB] ( 2652 )
309 Vertical distribution of streamwise velocity and its prediction in Ushaped channel
YANG Shi-Hong, HAN Jin-Xu, PENG Shi-Zhang, GAO Xiao-Li, GU Hong, LI Jiang-An
To find a guide to water management in field irrigation, the vertical distribution of streamwise velocity in a Ushaped open channel was clarified by means of indoor and field experiments. In addition, a twopower law for such a distribution was established by using the law of velocity in asymmetric closed channel. The methods for defining the parameters in the twopower law were given, and then the law was validated by the experimental data. The results showed that the flow velocity was lowered with increasing water depth, but the peak velocity appeared under the free surface. The predicted velocity distribution by the twopower law agreed with the experimental data in the 0.10-0.95 dimensionless depth so well that the error was as small as 5%, suggesting the law can involve the effect of free surface and channel wall. Compared with the traditional law of velocity distribution, the twopower law is more accurate, and may be used in an open channel with a crosssection of other shape.
2012 Vol. 30 (3): 309-314 [Abstract] ( 3634 ) [HTML 1KB] [ PDF 1823KB] ( 2933 )
315 Performance prediction for pump and pumping system
Based on the existing formulas and those proposed by the author for pump and pumping system performance (efficiency and NPSHc) conversion, a further mathematical derivation was introduced and a group of universal conversion formula was developed in the paper. The universal formulas were applicable for head, flow rate, efficiency and  NPSHc. The head curves of both pump and pumping system were presented in a quadratic polynomial, and the head coefficients were calculated by using the least square method. The overall efficiency formula was detailed and the method for determining the constant involved the formula was introduced. Also, a universal NPSHc formula, which is applicable to any operating points, and where the shock loss effect is include, was provided in this paper. The approach for determining the coefficient in that formula was proposed as well. The universal formulas for head, flow rate, efficiency and NPSHc were derived according to flow similarity in pumps and by means of the affinity laws of pump, and presented with head coefficient, efficiency constant and NPSHc coefficient. All the formulas, their coefficients and constants were integrated into one formula, respectively; thus they were considered as universal ones, which are applicable to both model and prototype pumps. The universal formulas can be used to estimate pump and pumping system performance and carry out performance conversion from model to prototype.
2012 Vol. 30 (3): 315-323 [Abstract] ( 2610 ) [HTML 1KB] [ PDF 1995KB] ( 2259 )
324 Calculation of water normal depth in channels with common shapes
Liu-Ji-Liang, WANG Zheng-Zhong, SU De-Hui, YANG Xiao-Song, LIU Quan-Hong
Water normal depth calculation is an important task in the design of an open channel for drainage and irrigation. First, dimensionless variables including channel roughness coefficient, bed slope, geometric parameters, and discharge were introduced for each common section. In order to obtain general equations and evaluate their accuracy, the explicit equations available for water normal depth were expressed by those dimensionless variables. Then, the real ranges of those variables were specified for each common section in applications, the relative errors in the explicit equations that involve the variables were analyzed in the ranges. Also, the global relative error distribution diagrams were plotted to compare the maximum relative error and the global one. According to these analyses, the most appropriate equations, which can explicitly calculate the water normal depth in the channels with five types of common section, were spotted. Finally, based on the best approximations algorithm a new piecewise explicit equation was proposed for the water normal depth in a standard castlegate section. It was shown that the maximum relative errors in all the recommended equations are less than 1％ for the water normal depth in six types of common section. The results in the paper have provided an effective method for designing channels with six types of common section and carrying out hydraulic calculations.
2012 Vol. 30 (3): 324-329 [Abstract] ( 6709 ) [HTML 1KB] [ PDF 1569KB] ( 5446 )
330 Comparison of power generation scheme and benefit analysis for pump units in Jiangdu No.3 Pumping Station in reverse mode
WEI Qiang-Lin, HAN Yong-Geng, CHOU Bao-Yun, HE Shu-Quan
Jiangdu No.3 Pumping Station is located at the source of East Route of SouthtoNorth Water Diversion Project.
The station is subject to amount of redundant water from the upper reach, so it can utilize the water to generate power; however, the time for pumping water is much longer than that for generating power. Considering those features, it is necessary to optimize the power generation scheme for this reversible pump unit. In doing so, the basic situation and benefits of power generated by the pump unit in reverse mode were introduced; the technical issues were analyzed and the economic benefits were compared when the pump unit is reverse mode. The benefits of the pumping station due to power generation in the past more than 3 years were summarized, and the net benefits of three power generation schemes were analyzed and compared from the relationship between investment and income. The results indicated that large pumping station generating power by exploiting redundant water from upper reach can achieve better economic and social benefits. However, if a pumping station can be used to generate power or not and what scheme will be adopted should depend on the consideration about the primary and secondary relationship between pumping water and power generation as well as the economic and social benefits. For Jiangdu No.3 Pumping Station, the initial power generation equipment was updated to frequency converters. Though the frequency converters were installed, the cost of the main electric motors was reduced, causing the total cost of equipments was decreased. As a result, the power output was increases by 30%-35%. Besides, the frequency converters have no influence on the pumping efficiency of pump units, so they are technologically feasible. Moreover, the frequency converters are reliable in operation and can be installed easily.
2012 Vol. 30 (3): 330-334 [Abstract] ( 3735 ) [HTML KB] [ PDF 1391KB] ( 1925 )
335 Influence of weed leaves surface structures on droplet spread and evaporation
Qi-Li-Jun, WANG Pei, ZHANG Jian-Hua, LI Hui, JI Rong-Hua, WANG Jun
In order to reveal the difference in droplet spread and evaporation of the weed leaves with different surface structures, a series of experiments were conducted in this paper. The spray liquid was 0.5% glyphosate, the additive was organic silicon in a series of concentrations, and the sizes of tested droplets were 228 and 288 μm. The tested weed leaves had three surface structures, namely hairy, waxy and rough. The experimental evaporation process was recorded by a digital camera, so that the evaporation time and the image of maximum droplet spread area could be read from the video. The digital images of maximum spread area were segmented by using the Image Processing Toolbox of Matlab; eventually the size of the spread area was obtained. The experiment results indicated that increasing additive concentration led to an expanded spread area and a reduced evaporation time for the same leaf and droplet size. For the same droplet size and additive concentration, hairy leaves showed a largest spread area and a shortest evaporation time. The additive concentration exhibited most significant influence on spread and evaporation time when a droplet was on a leaf with waxy surface. For a leaf with rough surface, the grooves on the surface made the droplets in small size be spread relatively hard; for the droplets in large size, however, the groove structure showed less dominated effect on the spread area.
2012 Vol. 30 (3): 335-340 [Abstract] ( 2662 ) [HTML 1KB] [ PDF 1847KB] ( 2487 )
341 Optimization design of horizontal Francis turbine with two runners
ZHENG Yuan, YANG Chun-Xia, ZHOU Da-Qing, SHEN Ming-Hui, LI Xiao-Xu
The fluid dynamics through a horizontal Francis turbine with two runners in a power station aboard was analyzed by using a CFD code, suggesting the turbine was subject to a low efficiency and poor cavitation performance because of significant hydraulic loss caused from complex flow passage geometry and unsmooth flow. Since the update of stationary flow passages was unallowable, just the turbine runners can be optimized. It appears that there are three ways to optimize the runners, i.e. change the blade shape, adjust the runner crown profile and alter the relative location of two runners. Based on the N-S equations, Spalart-Allmaras turbulence model and SIMPLIC algorithm, the threedimensional, steady turbulence flow in the optimized turbine was simulated, the details of flow were obtained and the hydraulic performance was predicted. The results showed that the flow rate was increased to 28.55 m3/s, the left and right runner efficiency were reached to 92.24% and 91.78%; when the runner of type Ⅲ and crown profile of type B and the two runners blades having a stagger pattern were adopted. Meanwhile, the cavitation performance of the runners of type Ⅰ, Ⅱ and Ⅲ was analyzed, showing the runner of type Ⅲ has the best cavitation behavior.
2012 Vol. 30 (3): 341-345 [Abstract] ( 4389 ) [HTML 1KB] [ PDF 2385KB] ( 3014 )
346 Design and numerical simulation of inverted bucket pilot operated steam traps
LI Shu-Xun, XU Deng-Wei, LI Que, WANG Chao-Fu
Since the pilotoperated steam trap is subject to a high level of noise and a poor bearing capacity of pressure when it is operated under high temperature, high pressure and high flow rate condition, a new type pilotoperated stream trap, which is in shape of inverted bucket and is applicable for ultrahigh flow rate, was designed and developed in the paper. A Mathematical model was set up for the valve, and a twostage throttle sleeve muffler was designed according to the throttling principles of flow. A numerical simulation of threedimensional, turbulent flow in the valve was conducted by using the CFD code Fluent based on Reynolds timeaveraged N-S equations, the SIMPLEC scheme and the standard k-ε turbulence model. The results show that the maximum pressure, that the pilot valve can bear, is increased to more than 10 MPa from 6.3 MPa, the maximum working pressure of the pilotoperated steam trap is 8 MPa and its mass flow rate is as high as 30 t/h. By comparison and analysis, it is obtained that the internal flow field in the inverted bucket pilotoperated valve with a muffler is more uniform and the pressure is changed gradually; in consequence, cavitation is avoided effectively. The maximum pressure drop is decreased to 190.8 kPa from 247.7 kPa; accordingly, the total pressure drop is increased by 165.6 kPa and the pressure drop ratio rise to 0.56 from 0.18, further the level of noise is lowered by 33 dB(A). As a result, the result in the paper can provide a reference for the design of inverted bucket pilotoperated steam trap.
2012 Vol. 30 (3): 346-350 [Abstract] ( 3144 ) [HTML 1KB] [ PDF 2574KB] ( 2284 )
351 Deflection analysis of annular Udiaphragm in hydraulic diaphragm pump
DENG Hong-Ying, ZHANG Sheng-Chang, ZHENG Ying-Chen
To establish a basic theory system and design method for a new type of annular Udiaphragm in hydraulic diaphragm pumps, the relation between Udiaphragm deflection and deformation quantity was analyzed by using the nonlinear analysis function in finite element software Ansys. A thin, hollow, double shell Udiaphragm finite element model with geometry and material nonlinear character was established for the annular Udiaphragm used in the prototype of hydraulic diaphragm pump. The deflection of the Udiaphragm model was analyzed under different compression and stretch displacements when the displacements of the supported end were fixed, the displacements of the free supported end were prescribed and the pressure loads were applied on both sides of the Udiaphragm. The computed displacements of deflection were fitted by using differential evolution method where the correct fitting curves were determined by controlling mean square error and correlation coefficient and so on. The Udiaphragm movement was clarified and an empirical relation for the deflection was obtained, eventually a theoretical formula for camber working volume was given. All the results above will provide a theoretical basis for working mechanism and design optimization of an annular Udiaphragm.
2012 Vol. 30 (3): 351-355 [Abstract] ( 2574 ) [HTML 1KB] [ PDF 1640KB] ( 2109 )
356 Spatial and temporal variation of crop water productivity in China
CAO Xin-Chun, WU Pu-Te, WANG Yu-Bao, ZHAO Xi-Ning, ZHANG Bao-Qing
In order to evaluate the water use efficiency in agriculture in China, the data relevant to the water used for crop production of 459 large irrigation districts in 31 provinces in the years of 1998, 2005 and 2010 were collected; then the values of Grain Irrigation Water Productivity (G) was calculated. The spatial autocorrelation analysis was carried out to study the spatial and temporal variation of G during 1998—2010. The results revealed that G is increased with year in every large irrigation district in all the provinces; meanwhile, the G for a representative year is 1.03 kg/m3, the maximum one is 2.15 kg/m3 in Henan and the minimum is 0.25 kg/m3 in Hainan. There is a clear spatial clustering phenomenon, i.e. a higher G is in HuangHuaiHai region whilst a lower one is found in the south of China. The amplitudes of change in G in Jiangxi, Anhui and Chongqing are different from their neighbors, a localized effect is presented. The reasons for such spatial and temporal variation of G were elaborated.
2012 Vol. 30 (3): 356-361 [Abstract] ( 2646 ) [HTML 1KB] [ PDF 1391KB] ( 2184 )
362 Study on characteristics of soil water resources in Hanwang station located in Huaibei Plain
WANG Jing-Cai, XIA Zi-Qiang, PENG Zhao-Ran, LU Zhi-Hua
In order to understand soil water and characteristics of its resources, some parameters including soil moisture, moisture storage capacities, evaporation, infiltration have been observed for fouryear in Hanwang Experimental Station of Hydrology and Water Resources located in Huaibei Plain under 0.5-3.5 m groundwater levels and three mulch conditions. And a water balance was also used. The results showed that in the same layer the soil moisture content was the highest with straw mulch, the lowest without mulch, was in between with plasticfilm mulch; the changes in soil moisture were relatively stable under mulch conditions; soil unsaturated zone, which is similar to a reservoir, plays an important role in regulation and storage of soil water. Thus, soil water can be considered as an important water resource. With increasing thickness of soil unsaturated zone soil evaporation was pronounced, but phreatic evaporation and infiltration were gradually reduced. The present result has significance in exploitation and utilization of soil water resource and agricultural production.
2012 Vol. 30 (3): 362-367 [Abstract] ( 2749 ) [HTML 1KB] [ PDF 1823KB] ( 2384 )
368 Working stability of two way stepping fluidic sprinkler
The differences between the forward and backwardstepping process of the twoway stepping fluidic sprinkler of type PXSB50 were analyzed to study the stability of the sprinkler. The gasliquid twophase flow in the pipes for controlling forward and backwardstepping process was studied and the pressure difference in the pipes was compared. The length of the deriving fluid tube, the size and position of the air compensating hole have influence on forward or backwardstepping frequency and angle, spraying range. The frequency was increased but the spraying range was with reducing length. For the same length, the forwardstepping frequency was considerably higher than the backwardstepping frequency; accordingly the spraying range in the forwardstepping process was smaller than that in the backwardstepping process. The closer the air compensating hole was placed to the reversing mechanism, the faster the stepping frequency becomes, and the smaller both the stepping angle and the spraying range get. For the twoway stepping fluidic sprinkler of type PXSB50, an optimum combination of the length of the deriving fluid tube, the size and position of the air compensating hole was obtained by theoretical analysis and experiment, those parameters as follows: the length of the deriving fluid tube 378 mm, the length of the forwardstepping pipe 648 mm, the length of the backwardstepping pipe 648 mm, the diameter of the forwardstepping air compensating hole is 2.0 mm, the diameter of the backwardstepping air compensating hole is 25 mm, the position of the forwardstepping air compensating hole is 3 mm.
2012 Vol. 30 (3): 368-372 [Abstract] ( 2044 ) [HTML 1KB] [ PDF 1706KB] ( 2274 )
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 中国农业工程学会农业水土工程专业委员会
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 袁寿其
编辑出版
 《排灌机械工程学报》编辑部
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徐云峰  张文涛 陈建华
谈国鹏  朱漪云 盛    杰
　

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