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Journal of Drainage and Irrigation Machinery Engin
 
2012 Vol.30 Issue.1
Published 2012-01-30
article
Article
1 Cavitation model with noncondensable gas effect and its numerical simulation
SONG Yu,CAO Shu-Liang
A transport equationbased cavitation model was developed according to the homogeneous assumption in this paper.The mechanism of evaporation and condensation was considered in the model.The noncondensable gas was also taken into account in cavity formation and development.The RNG turbulence model was employed with a modified turbulent viscosity according to the mixed density.The proposed model was implemented to simulate the steady cavitating flow around a NACA66 airfoil.The pressure coefficient distributions on the suction side of the foil agreed well with the experiment results.Furthermore,the effects of noncondensable gas,inlet turbulent kinetic energy and turbulence dissipation rate on the cavity length were evaluated.The proper values of noncondensable gas,inlet turbulent kinetic energy and turbulence dissipation were selected.Then,the proposed model was applied to an unsteady cavitating flow.The numerical results clearly reflected the whole process of the cavitationcloud generation,growth,dispersion and collapse.The simulation showed re-entrant jet is one of the main reasons for the breakoff process.The Strouhal number obtained agreed well with the experiment results.The overall results prove the reliability of the proposed model in cavitating flow simulations.
2012 Vol. 30 (1): 1-5 [Abstract] ( 2966 ) [HTML 1KB] [ PDF 1203KB] ( 2093 )
6 Analysis on tracing ability of PIV seeding particles in flow fields of centrifugal pumps
LI Ya-Lin, Yuan-Shou-Qi, Tang-Yue, Yuan-Jian-Ping
PIV seeding particles selection is flow fielddependent,so that the selecting suitable seeding particles to flow field in centrifugal pumps is the key thing to allow the accuracy of PIV measurement to be guaranteed.Based on the particleliquid twophase turbulent flow theory,the forces acting on the seeding particles,mainly including the viscous resistance and the forces caused from centrifugal acceleration field in a centrifugal pump were analyzed.Then the Lagrange equation of a seeding particle was established by introducing an external potential force into the BBO equation.Using the Fourier integral transform,a formula,which is applicable for PIV measurement of flow field in a centrifugal pump,for calculating the seeding particle tracing ability was deduced initially.Utilizing the PIV phaseaveraged measurement results of the flow field in a centrifugal pump,the seeding particle tracing ability was estimated.The results turned out the particle tracing ability in the radial direct is poorer than that in the circumferential one,thus the seeding particles should be selected according to the priority of tracing ability in the radial direction.Even though the results of PIV measurement are processed with a phaseaveraged technique,the velocity of seeding particles doesn′t represent the real velocity of fluid because of the effects of impeller rotation and streamline curvature,and causing a maximum error is as high as about  4.55%.The formula can be used to examine the reliability of seeding particles to improve the accuracy of PIV flow measurement in centrifugal pumps.  
2012 Vol. 30 (1): 6-10 [Abstract] ( 4431 ) [HTML 1KB] [ PDF 934KB] ( 2604 )
11 Numerical simulation of submersible mixer with three blades
TIAN Fei, SHI Wei-Dong, LU Xi-Ning, CHEN Bin, Ou Ming-Xiong
To study the performance of a submersible mixer,the fluid flow driven by the mixer in a sewage pool was simulated using Fluent 6.3.An unstructured tetrahedral mesh was generated by Gambit.The MRF technology,k-ε turbulence model and SIMPLE algorithm were adopted in the simulation.The entire fluid flow field and the velocity distribution in each crosssection were analyzed.The shaftpower,axial and radial distance affected by the mixer were studied as well.The results showed that a continuously recirculation current of water is established in the pool〖JP2〗 by the submersible mixer,namely the fluid is propelled in the axial direction initially and diffused in the radial direction.Consequently,the water in the pool is agitated throughout and the flow velocity is usually higher than 0.3 m/s,which complies with the working requirement of the mixer.It suggests the submersible mixer matches the sewage pool and makes sure that a motor with 3.0 kW rate power is suitable for it.Such a numerical flow simulation method can provide a reference for practical applications of submersible mixers.
2012 Vol. 30 (1): 11-14 [Abstract] ( 4162 ) [HTML 1KB] [ PDF 1067KB] ( 2185 )
15 Multistage auxiliaryimpeller performance analysis and its application
WU Da-Zhuan, Yang-Shuai, Sun-You-Bo, Wang-Le-Qin, Min-Wei-Bin
In order to analyze the structure of lowpower consumption auxiliaryimpeller and apply it to selfpriming pumps,the main factors affecting power consumption and sealing pressure ability were analyzed by using CFD numerical simulation.A variety of numerical models were established based on blade type,number of blades,antirotation guide vanes,radial clearance and balance outlet locations.The k-ε turbulence model was adopted for steady flow simulation in predicting hydraulic performance.The obtained results showed that 4.9% more sealing pressure could be achieved when afterwardbent blades were used and the number of blades was increased.However,40% more power consumption was generated during the same process and therefore the sealing pressure power ratio was decreased.The antirotating vanes can eliminate the liquid rotation and improve the sealing ability 5.7% higher.The change of vanes′ width has little effect on further enhancing the ability of sealing pressure.With the decrease of the radial clearance between impeller and wall,sealing ability performs much better.The presence of balance outlet can improve the sealing effect 3.5% better.However,the location of balance outlet has a greater impact on the ability of sealing pressure.In the same time,twostage auxiliaryimpeller was put forward and was analyzed about power consumption and sealing ability.Analysis and engineering application results showed that the multistage auxiliary impeller with afterwardbent blades and fixed blades has a better sealing performance and the power consumption could be reduced to 55% of a singlestage structure.
2012 Vol. 30 (1): 15-19 [Abstract] ( 2645 ) [HTML 1KB] [ PDF 1352KB] ( 1701 )
20 Optimization method for hydraulic performance of centrifugal pump at multi operation points
WANG Kai, LIU Hou-Lin, YUAN Shou-Qi, WU Xian-Fang, WANG Yong
An optimization method for the hydraulic design of centrifugal pumps at multioperation points was proposed by means of a global optimization algorithm and a computational model for estimating hydraulic losses and energy performance of centrifugal pumps.In the method,the values of several key geometric parameters in an original design were used as the initial conditions,and the design head was considered as a constraint condition,and the weighted average shaftpower at multiple operation conditions was chosen as the objective function.The adaptive simulated annealing algorithm was used to solve the model of hydraulic losses and energy performance.Additionally,the supertransitive approximation method was applied to update optimal weighted coefficients in the objective function.A centrifugal pump with a special speed of 129.3 was optimized with the method.The CFD numerical simulations were done for the original design and the optimized one,respectively.It was shown that the shaftpower of the optimized case is less,but the head is higher than the original design at 0.6Qd and 1.2Qd.The weighted average shaftpower optimized is decreased by 0.06%,but the weighted average efficiency rises by 0.46% compared with the original design.The results could be really useful to design an energysaving centrifugal pump.
2012 Vol. 30 (1): 20-24 [Abstract] ( 2631 ) [HTML 1KB] [ PDF 931KB] ( 1746 )
25 Effect of runner outlet swirling flow on diffuser pressure recovery
HAN Feng-Qin, WANG You-Qing, GAO Hai-Peng, JIU Bao-Tian-Qiao
In order to study the effect of swirling kinetic energy at runner outlet on the pressure recovery performance of a straight diffuser with a larger cone angle,the hydrodynamic mechanism and rules behind the effect were investigated with computational fluid dynamics.A bulb turbine with adjustable guide vanes and runner vanes was employed as the model.The 3D flow through the whole channel of the turbine,from the inlet to the case including bulb and stay vanes,guide vanes,runner vanes to the outlet of draft tube(diffuser) was computed.Through calculating the pressure recovery coefficient Cp and the specific hydraulic deficiency δD of the draft tube in a wide operating range,a hydrodynamic relationship between the optimum swirling kinetic energy and the maximum pressure recovery in the straight diffuser was established,subsequently,the hydraulic performance of the draft tube was predicted.A new parameter,named kinetic energy distortion rate Iek at the outlet of diffuser was defined,and the pattern of kinetic energy in diffuser was compared under various inflow swirls.The result revealed that there is a clear correlation between Iek and Cp,that is,when the distortion rate Iek is minimum,the recovery coefficient Cp is the peak and the deficiency δD is minimum.Thus,the new parameter Iek can be used as an index for evaluating the quality of swirling flow through a straight draft tube in the bulb turbine with adjustable guide vanes and runner vanes.
2012 Vol. 30 (1): 25-29 [Abstract] ( 2084 ) [HTML 1KB] [ PDF 1280KB] ( 1583 )
30 CFD numerical simulation of flow field in charging pump for nuclear power plants
ZHU Rong-Sheng, WANG Tao, FU Qiang, CHEN Jing-Jun
In order to study the internal flow mechanism of the multistage centrifugal charging pump in nuclear power plants,the steady 3D turbulent flow in such a pump in a 1 000 MW nuclear power plant has been simulated numerically by using CFD technique,where the k-ε standard turbulence model and SIMPLEC algorithm were adopted.The velocity,pressure and turbulent kinetic energy distributions in the impeller and diffuser of every stage were obtained; through those variables the internal flow characteristics were analyzed.The results showed that a local low pressure zone appears in the gap between the impeller and the diffuser.An nonuniform velocity distribution and reverse flow pattern,which are related to extra hydraulic losses,present in the region between the impeller outlet and the diffuser inlet.In that region,the turbulent kinetic energy is not only much high but also subject to very nonuniform profile,generating larger energy loss.By means of the numerical simulations the regions with remarked hydraulic loss have been identified.This is quite helpful to optimize the pump design in future.
2012 Vol. 30 (1): 30-34 [Abstract] ( 2898 ) [HTML 1KB] [ PDF 2088KB] ( 1595 )
35 Calculation of gap between roller and valve plate for roller rotary oil pump
ZHANG Sheng-Chang, LIAN Jia-Di, DENG Hong-Ying, CHEN Xi-Dong, KE Yu-Long, ZHANG Yu-Lin
To improve the efficiency of rod oil pumps,a new type of multistage,doubleaction roller rotary oil pump was put forward.In the pump rolling friction pairs are used to replace the conventional sliding friction ones and that cause a lower friction loss.A structure of multiple stages in series was adopted to raise discharge pressure greatly.Meantime a doubleaction structure in the inlet and outlet chamber was applied to get the radial force on the rotor balanced.Through analysis of forces applied on a roller in the pump,a force equilibrium equation was established.Based on the principle of minimum sliding friction,an optimal slot width was determined precisely by means of a computer code composed.By analyzing the rolling condition of a roller,the equilibrium equation of frictional moments on the roller surface was deduced,and considering the principal of optimal gap between two flat plates,eventually,a formula for determining the optimal gap between the roller and the valve plate was deduced.For a design example,such an optimal gap was calculated.As the gaps     were 0.044 399 mm and 0.055 975 mm,respectively,the forces applied on rollers will be relief and the leakage will be reduced,subsequently the pump overall efficiency will be improved.The method proposed in the article comes up with a theoretical trial for determining,optimizing and choosing the gap to the pump.
2012 Vol. 30 (1): 35-39 [Abstract] ( 4070 ) [HTML 1KB] [ PDF 1102KB] ( 1978 )
40 Simulation of vertical inlet pipes layout effect on pump inflow patterns
XU Cun-Dong, YANG Ke, XIAO Lu, SONG Yong-Zhan, HUANG Xiong
The flow field in the intake and suction pipe of a pump station was simulated numerically by means of CFD software Fluent.In the computation,the finite volume method,3D unstructured mesh and steady incompressible RNG k-ε turbulence model were applied.Moreover,both the hydraulic loss and massweighted velocity uniformity at pipe inlet were optimized based on CFD simulations.To investigate the effect of vertical suction pipe position on flow pattern at the pipe inlet,the flow fields in the pump intake and suction pipe were simulated when the suction pipe was located at various positions in the pump intake which were specified by two parameters: one is the distance from the entrance to suction pipe to bottom of the pump intake,the other is the minimum distance between the outside wall of suction pipe to the side wall of the pump intake.Those parameters were expressed as a fraction of the inner diameter D of suction pipe according to the current pump intake design specifications.The velocity uniformity and hydraulic loss were correlated to the two parameters.The results indicated that in the large pump stations equipped with horizontal centrifugal pumps reasonable large two parameters can ensure the flow pattern at the pipe inlet uniform to prevent the pump intake from sand sedimentation and allow the pump to be operated efficiently and stably.The simulation results suggest that the minimum distance between the outside wall of suction pipe to the side wall of the pump intake and the distance from the entrance of suction pipe to bottom of the pump intake should be(0.4-0.8)D and(0.6-0.8)D,respectively,for reference in pump intake design.
2012 Vol. 30 (1): 40-45 [Abstract] ( 2637 ) [HTML 1KB] [ PDF 1844KB] ( 2044 )
46 Startup transient behavior of bulb pump unit with VFD
ZHANG Ren-Tian, LI Ci-Xiang, YAO Lin-Bi, ZHU Hong-Geng
In order to obtain the transient hydraulic characteristics of the bulb pump unit in a pump station with VFD during startup,the essential features of lowspeed synchronous startup controlled by VFD were analyzed initially.Then the moment equilibrium equation of the rotor of pump unit was established in the startup transient period.The mathematically expressing approach for the electromagnetic torque in the synchronous motor in terms of time was investigated.The resistance moments,inclusive of hydraulic resistance moment,bearing frictional moment and motor cooling fan resistance moment etc,and their mathematical expressions were clarified.Finally,the flow rate allocation and conservation between the rapiddrop gate and flap valve during the transient period were determined.Taking Huaiyin No.3 Pumping Station as a study case,the startup transient process of the pump unit under the design condition was simulated to obtain the primary electrical and hydraulic parameters.In the simulation,the pump started running when the instant exciting current reached 0.63 times its design value and the frequency was about 6.5 Hz,causing a 15 s lag delay.As a result,a best match was obtained between the motor rotational speed frequency and the lag time for opening the rapiddrop gate.At the design condition,when the rotational speed of the synchronous motor is linearly increased from 0 to 125 r/min in 100 s interval,the optimal lag time is 70 s for opening the rapiddrop gate
2012 Vol. 30 (1): 46-52 [Abstract] ( 3153 ) [HTML 1KB] [ PDF 1773KB] ( 1598 )
53 Experiment research on erosion of self excited inspired pulsatile jet in submerged conditions
GAO Chuan-Chang, Zhao-Li, Liu-Xin-Yang, Huang-Xiao-Liang
In order to compare erosion effect of the selfexcited inspired pulsatile jet with the continuous one under different submergence conditions,experimental studies of paraffin erosion caused from a jet was carried out by using own developed apparatus.In the experiments,the jet impact power,inspired air capacity,eroded surface depth,volume loss and eroded surface area were obtain under different submerged depths.The experimental results showed that the impact power of the continuous jet is larger than inspiration pulse jet; while the power of the inspired pulsatile jet is higher than that of the jet without inspiration.Moreover,the difference in impact power between the inspired and noninspired jets steadily gets smaller with increasing submerged depth.When the submerged depth is shallower(30 m or less),the eroded surface depth of the continuous jet is smaller than the inspired pulsatile jet due to the stronger denudation caused from the air inspired.However,if the submerged depth is deeper(40 m or more),the eroded surface depth of the continuous jet is larger than the inspired pulsatile jet because of the less air inspired.The eroded surface area and volume loss of the inspired pulsatile jet are less than the continuous jet under various submerged depths.The eroded surface area and volume loss of two kinds of jet become small gradually,and their difference between the two jets also gets closer and closer with increasing submerged depth.
2012 Vol. 30 (1): 53-56 [Abstract] ( 1953 ) [HTML 1KB] [ PDF 1132KB] ( 1563 )
57 Water resources carrying capacity of Xianyang City basedon system dynamics
HUANG Rui, LIU Jun-Min, LI Lin-Kai
Based on the principles and methods of system dynamics,carrying capacity of water resources system of Xianyang City is divided into industrial,agricultural,life and ecology,water and wastewater treatment and reuse subsystem.Regarding water shortage level as the main feedback factor,considering people's decisionmaking preferences of using water when water is in shortage,a system dynamics model of water resources carrying capacity of Xianyang City was established by means of the feedback relationships between the various subsystems.The simulation results showed that if the city is being developed according to the trendbased development plan,it will be subject to severe water shortage(in a level of 9% to 35%) in planning year since the agricultural and ecological water was diverted to the rapidly developing industry.If the city is developed in the track of resourcebased and environmental protection,the ecological environment will be protected very well; however,industrial and agricultural development will be severely constrained.If the city is adopted an economic development plane,even though industry development will be rapid,the city will be subject to agricultural irrigation decreased,environment degraded,serious overexploitation of groundwater,causing 3%5% water shortage,eventually leading to poor sustainable development.If the city is indicated to choose a coordinated development mode,a 13.8% growth rate of industry and agriculture will be maintained,more wastewater treated will be reused,agricultural irrigation area will be expanded steadily,and ecological environment will be improved in a great deal,water shortage will be as low as 0.4%.It suggests this plan is the optimal solution to make sure water resources carrying capacity of Xianyang City will be kept in sustainable manner.
2012 Vol. 30 (1): 57-63 [Abstract] ( 2234 ) [HTML 1KB] [ PDF 1535KB] ( 1773 )
64 Experimental study on flow characteristics of water cycle in air conditioning heat pump unit
TONG Ming-Wei, HU Peng, SUN Ya-Hui, WANG Qian, YU Jia-Jia
A new ceiling cooling panel of capillary porosity wick(CCPCPW) which was configured by porous media of potassium citrategypsum was put forward to reduce high energy consumption and improve comfort of the air conditioning heat pump unit.In this case,when water is cooling the medium,CCPCPW behaves like a uniform channel.In the paper,the flow resistance in CCPCPW and the serpentine radiant heat transfer pipes(SRHTP) was studied by experiment.A comparison of resistance between CCPCPW and SRHTP was made when the flow rate of cooling water was ranged in 4-40 L/h; moreover,the Ca2+ concentration in circulating water were tested by the ICPOptional Emission Spectrometer in CCPCPW when the unit was run for 1 200 hours.The results showed that the lower permeability of CCPCPW leads to a larger resistance compared to SRHTP when the flow rate is less than 17 L/h.However,when the flow rate is larger than 17 L/h,the larger permeability of CCPCPW results in a lower flow resistance compared to SRHTP.This suggests the inertial force by the disturbance of CCPCPW is smaller than SRHTP,and the friction factor of CCPCPW is smaller.After running for 360 hours,the Ca2+ concentration has been stable to make sure the recirculation water can be used for a long period of time in the air conditioning system.
2012 Vol. 30 (1): 64-68 [Abstract] ( 2118 ) [HTML 1KB] [ PDF 1125KB] ( 1556 )
69 Hydrodynamic lubrication characteristics of planet gear thrust washer used in highspeed planetary transmission
WANG Hong-Wei-1, 2 , MA Biao-1, ZHAO Xi-Jing-2, ZHENG Chang-Song-1
For the washer in planetary transmission with spur gears,in order to reduce wear between the thrust washer and planet gear due to the force in the axis direction,hydrodynamic lubrication design was presented by machining rectangular grooves in the radial direction into one side of thrust washer.Such grooves can result in a hydrodynamic pressure to separate the contact surfaces and reduce the wear accordingly when there is a relative movement between the planet gear and thrust washer.Rectangular grooves were chosen due to their symmetrical structure,two rotational directions and easily to be machined.A steady Reynolds equation was set up and the finite volume method(FVM）was used to obtain its numerical solutions.The effects of number of grooves,ratio of groove angle to periodic groove angle,depth of grooves and radial width etc on carrying capacity of hydrodynamic washer,oil flow rate and temperature rise were studied.Considering feasibility of application,the lubrication characteristic was analyzed for the cases with less number of grooves(2-12).The results show that when the number of grooves is about 20,the carrying capacity of oil film is the highest.When the number of grooves is in the range of 10 to 60,if the ratio of groove angle to periodic groove angle is about 0.5,the carrying capacity will be better.Moreover,the wider the radial width of washer,the higher the carrying capacity.More number of grooves,deeper groove depth and wider groove radial width increase the oil flow rate or vice versa.Larger ratio of groove angle to periodic groove angle results in a low oil flow rate.The measures of decreasing temperature rise are more number of grooves,wider radial width to make sure the groove depth is 10-40 μm.
2012 Vol. 30 (1): 69-74 [Abstract] ( 2815 ) [HTML 1KB] [ PDF 1974KB] ( 1403 )
75 Numerical analysis of slipper bearing′s film shape in axial piston pump using genetic algorithms
LIU Hong, PENG Zeng-Xiong, JING Chong-Bo
The film shape of slipper bearing has a great influence on its lubrication characteristics in axial piston pumps.In order to calculate the slipper lubrication characteristics correctly,the film shape should be obtained precisely.Firstly,considering the slipper overturn phenomenon,the film shape was described by using nonuniform gap,and the lubrication equation of the slipper was established and solved by the GaussSeidel relaxation method to obtain its pressure field.Then an optimization problem,which consists of two decision variables,one objective function,two equality constraints and two inequality constrains,was deduced for the film shape.The two equality constraints are based on the simplified normal force balance equation and flow rate continuity equation,which were obtained with equilibrium analysis of force on the slipper by considering the relation between the film shape and a corresponding pressure field.The two inequality constrains,the slipper tilt angle and azimuth angle were involved.Finally,the Niche Genetic Algorithm was applied to solve this problem.The results showed that this method is really robust and can achieve the optimum solution faster with a higher accuracy，and can get a steady 3D film shape of a slipper precisely.The method has provided a theoretical base for correct prediction of slipper lubrication characteristic and slipper bearing design.
2012 Vol. 30 (1): 75-79 [Abstract] ( 2469 ) [HTML 1KB] [ PDF 1391KB] ( 1615 )
80 Principle and application of evaporation pan with device of water automatic replenishing
LIU Xiao-Fei, ZHANG Ji-Yang, SUN Jing-Sheng, SHEN Xiao-Jun, Uzokwe Pauline Adaobi
In order to better make use of pan evaporation for guiding crop irrigation,a simple,cheap and easy for use evaporation pan with a device of water automatic replenishing was designed based on the working principle of the Markov′s bottle.In fact,such a pan was an updated version of the 20 cm standard evaporating pan by attaching a device that can replenish water automatically,so that water keeps a constant level in the updated pan.According to the standard evaporation in the 20 cm standard evaporation pan,the water evaporation process in the designed pan was verified.The relationship between the water evaporation and water consumption by winter wheat during the same growing period was established by field experiment.The results showed that the designed pan has a good stability,the average relative error between two different measurement groups was less than 5%,and the average relative error in more than 5 day was less than 2%.In addition,there was such a significant correlation between the water surface evaporation of the designed pan and 20 cm standard evaporation pan that the correlation coefficient was as high as 0.99.In North China,the ratios of the water consumption by winter wheat over that accumulated water evaporation of the designed pan device were 1.09,1.31 and 1.16 at jointing,headingflowering and grainfilling maturity stage,respectively.Therefore,the water evaporation of the designed pan device can guide farmland irrigation to realize excellent quality,high efficient and high yield of crop.
2012 Vol. 30 (1): 80-84 [Abstract] ( 4791 ) [HTML 1KB] [ PDF 1147KB] ( 2075 )
85 Analysis on discharge energy dissipation in twostage plugs
YIN Ze-Gao , ZHU Hui-Jie, CAO Xian-Wei, CHEN Geng, ZHENG Qing-Xin
In order to analyze the discharge energy dissipation of a twostage plug and reveal the influence of its geometrical parameters on the dissipation,a threedimensional RNG k-ε turbulence model was adopted to study discharge in the plug.A physical model of the plug was established to validate the computational results,good agreement has been achieved.The area contraction ratios of both plugs are 0.2,0.3,0.4 and 0.5,respectively,the relative lengths of two plugs are equal to 0.5,1.5 and 3,respe ctively,causing 144 experimental cases.Then the verified mathematical model of energy dissipation was used to estimate the discharge energy loss in the twostage plugs at the 144 conditions.The results showed that the area contraction ratio influences the energy dissipation more significantly than the relative length.The energy dissipation rate and ratio of the first plug were increased,but those of the secondstage were decreased with increasing area contraction ratio of the second plug.The energy dissipation rate and ratio the first plug were decreased,the energy dissipation rate of second plug was varied little,but its energy dissipation ratio was increased with increasing area contraction ratio of the first plug.When the area contraction ratios of the two plugs were optimal,their energy dissipation rates were the largest.
2012 Vol. 30 (1): 85-90 [Abstract] ( 2059 ) [HTML 1KB] [ PDF 1678KB] ( 1515 )
91 Water filling and emptying process of pipeline with combined air valve
ZHENG Yuan, XUE Chao, ZHOU Da-Qing
In order to research the air pressure changes in water filling and emptying process of a long distance pressuredpipeline,sectional treatment and ordinal water filling and water emptying were adopted according to the characteristics of the pressuredpipeline.For each segment of the circular pipe,a mathematical model which involved the relationship between the water volume and water depth was established.On the basis of the definite positions of air valves and drain pipes as well as with the principle of small flow filling, the ideal equation concerning with the characteristics of air valve were calculated by Fortran programmed code for the various flow rates of both water filling and water emptying.The results show that the greater flow rate of the water filling and water emptying,the higher and lower the corresponding air pressure,and the higher risk of the pipe.The greater flow rate of water filling and water emptying should be accepted on the premise that the pipe is safe.The final filling flow rate is 16 m3/s,and the drain valves are full opening during water emptying process.
2012 Vol. 30 (1): 91-96 [Abstract] ( 2470 ) [HTML 1KB] [ PDF 1552KB] ( 1750 )
97 Experiment on dust suppression performance of selfpriming sprayer
MA Zhong-Fei , ZHANG Yu-Xiang, YANG Xiu-Li, GE Zhi-Lin
To improve the spray dust suppression,a means,namely selfpriming sprayer dust suppression,was put forward,the working principle of dust suppression was analyzed,and the selfpriming sprayers with different structures were designed.The orthogonal and related comparison experiments were made on those designed selfpriming sprayers.The test results indicated that the distance between the mixing chamber throat and driving nozzle outlet,diffusion angle and driving pressure have different effects on the SMD value,effective range,atomization angle,amount of air entrained.When the distance between the mixing chamber throat and driving nozzle outlet,diffusion angle and driving pressure are 48 mm,30° and 6 MPa,those parameters achieve their optimal values and the best performance presents in dust suppression.The SMD value of conventional single nozzle spray is 124.3 μm,but that of selfpriming sprayer is 108.5 μm,causing a reduction of 12.7% in SMD.As the driving pressure is 6 MPa,the efficiency of all size dust removal is 92.67% and that of breathable dust removal is 87.21% in a conventional single nozzle spray.However,at the same driving pressure,the efficiency of all size dust removal 93.6% and that of breathable dust is 92.69% in the selfpriming sprayer optimized by the orthogonal experiments.Obviously,the dust removal efficiency of breathable dust has been improved greatly in the optimized selfpriming sprayer compared with the efficiency of all size dust removal.
2012 Vol. 30 (1): 97-101 [Abstract] ( 2580 ) [HTML 1KB] [ PDF 1190KB] ( 1775 )
102 Analysis of flow field of spiral groove dry gas seal face based on CFD
YU Shu-Rong, CAO Xing-Yan, DING Xue-Xing, ZHANG Wei-Zheng, HAN Ming-Jun
The threedimensional microscale models of flow domain between two matching rings with spiral grooves in a dry gas seal was built by Solidworks,then the steady laminar flow in the models with various gas film thicknesses was numerically calculated by Fluent.At a special condition,a gas film thickness,which allows both the opening force in the film and the leakage through the film can achieve optimal values simultaneously,was determined based on the predicted dynamic pressure effect and radial flow velocity.For a series of gas film thickness,namely 3.5,4.5,5.5 μm,the effects of surrounding pressure and rotational speed of rotating ring on the leakage and power consumed were investigated.The results showed that a better dynamic effect and less leakage are obtained with the film thickness of 3-6 μm; moreover,the best dynamic effect and minimum leakage are achieved at the thickness of 3.5 μm.The leakage and power consumption rise linearly with increasing rotational speed as the film thickness and surrounding keep to be constant.Similarly,the leakage and power consumption arise linearly with increasing pressure as well when the film thickness and rotational speed remain unchanged.
2012 Vol. 30 (1): 102-106 [Abstract] ( 2901 ) [HTML 1KB] [ PDF 1472KB] ( 1558 )
107 Sealing performance of mechanical seals with variousend faces using dynamic mesh technique
CHEN Hui-Long, Li-Wen-Yu, Wu-Rong-Zhen, Lin-Qing-Long, Huang-Jian-Ping
Dynamic mesh technique in Fluent is used to simulate the film flow between two rings of mechanical seal.By this method the unknown thickness of film flow can be obtained so that the flow field in the film more resembles to that in the real situation.Then,the pressure,wall shear stress and leakage rate were estimated and compared among the mechanical seals with usual flat,micropore and microporespiral groove end faces,respectively.The results turned out that both the micropore and spiral groove can produce dynamic pressure effect.The high pressure region appears in the tapered section of the micropore end face,for the spiral groove face,the high pressure region locates at the step behind the groove trailing edge instead.Compared with the usual mechanical seal,the micropore mechanical seal can generate sufficient dynamic pressure and be subject to less frictional wear,but a relative larger leakage rate.However,the microporespiral groove mechanical seal not only has less frictional wear but smaller leakage and an excellent lubrication characteristic.As a result,the microporespiral groove mechanical seal maybe provide a feasible way to get a high sealing and noncontacting performance with zero leakage.
2012 Vol. 30 (1): 107-111 [Abstract] ( 2013 ) [HTML 1KB] [ PDF 1265KB] ( 1805 )
112 Broadcasted fertilizer solute transport model in 2D surfacewater flow of border irrigation: I.Modeling
ZHANG Shao-Hui , XU Di, LI Yi-Nong , BAI Mei-Jian
The surface water depth cross land was obtained numerically by simulating the 2D full hydrodynamics model in border irrigation firstly.Then the linear and logarithmic profile of turbulent velocity along the depth in scale form was extended to those in tensor one; subsequently,a nonuniform 3D flow velocity field across the land and along vertical direction was constructed by combining the continuous equation of incompressible hydrodynamics.Eventually,a convectiondiffusion equation was adopted to describe the broadcasted fertilizer solute concentration across land and along depth of water in border irrigation.The diffusion coefficient was determined by using the nearby wall nonuniform flow velocity model.The initial condition was determined with the thin water layer hypothesis in surface water flow simulation of border irrigation.The overland boundary for solute dissolution and transportation was imposed by using a firstorder kinetics reaction model and mass conservation equation of solid fertilizer at a point.In this way,a fertilizer solute transport model is proposed in a 2D surface flow of border irrigation.
2012 Vol. 30 (1): 112-116 [Abstract] ( 2440 ) [HTML 1KB] [ PDF 851KB] ( 1695 )
117 Multivariable regression models of reference crop evapotranspiration and the spatial distributions in Xinjiang
LIAO Yi-Qun, LI Yi, Robert Horton, CUI Chen-Feng
Meteorological dates of 42 weather stations in Xinjiang were used to estimate ET0 at daily and monthly time scales by using Penman-Monteith equation.Multiplevariable regressions of ET0 in terms of 4 major climatic elements were conducted to obtain empirical equations for calculating ET0.Combining with the spatial analysis function of code ArcGIS,the coefficients of the empirical regression formulas for whole Xinjiang were interpolated based on the regression formulas in 42 stations;consequently the spatial distribution of those coefficients was obtained.The results indicated that the spatial distributions of ET0 were obviously varied across Xinjiang both at daily and monthly scales.And the values of ET0 in southern part of Xinjiang were significantly larger than those in northern.It was reasonable and reliable to use the multiplevariable regression formulas to estimate ET0 in different parts of Xinjiang.Because the empirical formulas are simpler than Penman-Monteith equation and with relatively high accuracy,they have fairly promoting values and good application prospects.For the regions without meteorological data,by using the coefficient plots proposed in the paper,ET0 values in those regions can be estimated at a given time scale.
2012 Vol. 30 (1): 117-124 [Abstract] ( 2091 ) [HTML 1KB] [ PDF 2460KB] ( 1591 )
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 江苏省教育厅
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 江苏大学
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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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