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Journal of Drainage and Irrigation Machinery Engin
 
2017 Vol.35 Issue.4
Published 2017-04-25
277 Application of entropy production method to centrifugal pump energy loss evaluation
ZHANG Yongxue, HOU Hucan, XU Chang, HE Wenxuan, LI Zhenlin
To accurately calculate the hydraulic loss of centrifugal pump and its location, improve the hydraulic performance and avoid the limitations of traditional method based on pressure drop analysis, the local entropy production method was introduced in this study on energy consumption evaluation of centrifugal pumps. The whole steady flow passage of centrifugal pump was numerically simulated based on Reynolds stress turbulent model and energy equation model, and then the local entropy production terms were defined by self-definition field functions. Taking the cases of pipe flow for air and water as example, the results calculated by the local entropy production method were highly consistent with those calculated by Darcy law, pressure drop method and energy balance method, indicating that the local entropy production method established is reliable. Meanwhile, the calculation for centrifugal pump shows that the impeller and volute casing are the main domains generating entropy production, and the irreversible energy loss generated mainly cover wall entropy production and turbulent entropy production and in the design flow condition, these two occupy 48.61% and 47.91% of the whole respectively at the most. Above all, the energy loss by the entropy production method have some errors but basically accord with those by the traditional method, indicating that this entropy production me-thod is feasible in centrifugal pump irreversible energy loss evaluation.
2017 Vol. 35 (4): 277-282 [Abstract] ( 1248 ) [HTML 1KB] [ PDF 2084KB] ( 2393 )
283 Experiment study on device performance of swirling jet pump
WANG Haiqu, LI Hong, ZOU Chenhai
In order to enhance the performance of swirling jet pump device, a new swirling jet pump device was designed.Choosing three different area ratio swirling jet pumps and corresponding non-rotating jet pumps as the study object, by changing the flow ratio, changing characteristics of the swirling jet pump device performance with jet pump area ratio and flow ratio was studied. Results showed that the optimal area ratio of the swirling jet pump is less than that of the irrotational jet pump. Compared with the irrotational jet pump,when the swirling jet pump′s area ratio is bigger or smaller, its pressure ratio and device efficiency are obviously superior to the irrotational jet pump′s; while its area ratio is close to irrotational jet pump′s, its pressure ratio and device efficiency are a little better than the irrotational jet pump′s. Compared with the irrotational jet pump device, the best efficiency points of swirling jet pump device move to big flow ratio direction, which will increase the efficient district range of device performance. Swirling jet pump device′s pressure ratio can increases 0.01 at most, equivalent to 5%-10% of irrotational jet pump device′s;while its efficiency can increases 4% at most, equivalent to about 25% of irrotational jet pump device′s.
2017 Vol. 35 (4): 283-288 [Abstract] ( 915 ) [HTML 1KB] [ PDF 1602KB] ( 1110 )
289 Influence of impeller back-blade type on molten-salt pump performance
HE Xianghui, LIU Houlin, TAN Minggao, WANG Kai, WU Xianfang
To study the effect of impeller back-blade type on the external characteristics, internal flow and axial force of molten-salt pump, a vertical high temperature molten-salt pump was chosen as the research model. Impellers with forward-bent back-blade, back-bent back-blade, leaned back-blade and straight back-blade in different numbers were established by using Cero software. Based on the k-ε turbulence model, the internal flow was simulated numerically. It is shown that the back-blade shape has less influence on external characteristics of molten-salt pump at design flow rate. Low pressure area appears at the rim of forward-bent back-blade clearly. The forward-bent back-blade and back-bent back-blade have little impact on the hydraulic loss in the pump. The back-blade has an important role in the pump axial force, and the effect is best when the blade number is six and 48% axial force can be balanced at most. If considering high efficiency, the back-bent back-blade can be used. If conside-ring the axial force balance, straight back-blade can be used.
2017 Vol. 35 (4): 289-295 [Abstract] ( 954 ) [HTML 1KB] [ PDF 1802KB] ( 1412 )
296 Effects of wear-rings clearance on flow characteristic in impeller side chamber of high-speed centrifugal pump
YANG Congxin, QIANG Pan
In order to analyze the flow characteristic in the impeller side chamber and the effect of wear-rings clearance modifications on it, the RNG k-ε turbulence model is employed in the Reynolds averaged Navier-Stokes equations in this study. A high-speed centrifugal pump with a speed of 38 500 r/min in a design condition was studied using CFD method. Results show that ut/u decreases with the increase of the radius in the front and back impeller side chamber; ut/u also constantly decreases in the impeller rotation direction and reaches the minimal value at α=0°(near the volute tongue).Near the should side of front as well as back impeller side chamber,there exists ur/u>0;while near the stator side of front as well as back impeller side chamber,there exists ur/u<0.The effects of the front wear-rings clearance and rear wear-rings which are separately imposed on the flow field structure of field structure of the front and back impeller side chamber are mainly coincident: at the same axial location,with the increase of the wear-rings clearance,ut/u of the core flow region increases; ur/u close to the stator side decreases; at the same radius, the larger the wear-rings clearance, the lower the static pressure.
2017 Vol. 35 (4): 296-302 [Abstract] ( 937 ) [HTML 1KB] [ PDF 2643KB] ( 1210 )
303 Analysis of instability flow on mixed-flow pump based on LES
ZHANG Lin, SHI Weidong, ZHANG Desheng, SHI Lei
A flow-field analysis model of the mixed-flow pump was established in order to study the flow field and pressure pulsation characteristics under different operating conditions. The unsteady numerical simulation of the whole flow field under different operating conditions was carried out by Large eddy simulation(LES)based on the CFX software. The results showed that the flow pattern was consis-tent at six channels except that a certain flow separation appeared on the suction surface near the guide vanes outlet at 1.00Qopt. When the rotating stall occurred, a lot of whirlpool developed near the suction surface of the guide vanes and the whirlpool scale increased first and then decreased from the inlet to the outlet at the guide vanes,more over the vortex core was attached to the suction surface where the pressure fluctuation was smallest. The pressure pulsationat different points was analyzed by FFT transform, which showed that the amplitude of the pressure pulsation increased graduallyfrom the hub to the rim. The distributiom of the pressure pulsation frequency at the outlet was similar to that at the inlet except that the amplitude decreased a little and the dominant frequency shifted to the low-frequency direction.Additionally, the pressure pulsation under different operating conditions was also analyzed. The changing regularity of three operating conditions was consistent.However, the frequency range is larger and the frequency components are more complex at 0.55Qoptcondition than at 0.75Qoptand 1.00Qopt condition. At 0.75 Qopt the low-frequency width is significantly reduced and the frequency of low-frequency pulsation was concentrated around 1N,white at 1.00Qopt,the frequency was not obvious except 6N and 12N, the amplitude of the pulsation frequency in the low-frequency range was significantly reduced, and the integral pulsation amplitude was significantly smaller than that under the other two operating conditions.
2017 Vol. 35 (4): 303-308 [Abstract] ( 858 ) [HTML 1KB] [ PDF 1935KB] ( 1603 )
309 Numerical simulation and experiment on gas-liquid separation in medium consistency pulp pump
YE Daoxing, LI Hong, ZHANG Xiang
In order to investigate the characteristic of gas-liquid separation in medium consistency pulp pump(MC pump), the Eulerian-Eulerian model was used to simulate unsteady gas-liquid separation. The effects of rotational speed, vacuum degree and flow rate on gas-liquid separation and transient gas-liquid separation process were analyzed. A MC pump test bed was established using sonar flowmeter, and operation performance was studied. The results show that high gas volume fraction is concentrated in the back of blade in turbulence generator and gas in the impeller decreases with speed increasing. The region area of high gas volume fraction decreases gradually with flow rate increasing, and gas is concentrated in the back blade root of turbulence generator at a large flow rate. The further separation was done by back blade of the impeller. Increasing rotational speed, vacuum degree and flow rate can improve separation effect. Lots of gas is concentrated on discharge port of the impeller, which is accompanied with strong interaction of gas-liquid two phases. The study on performance experiment shows that improving rotational speed and vacuum degree is helpful to gas-liquid separation, and the results of simulation are verified. Study on the characteristic of gas-liquid separation is helpful to understanding the evolution mechanism of separation process in MC pump and can provide design reference for the structure of gas-liquid separation and degas system.
2017 Vol. 35 (4): 309-318 [Abstract] ( 1063 ) [HTML 1KB] [ PDF 3414KB] ( 1394 )
319 Differential algebra model of hydraulic turbine including surge tank dynamics
HE Jianyu, Qian Jing, ZENG Yun, GUO Yakun, YU Shige
In the transient model of the hydraulic turbine, the hydraulic dynamic of the surge tank is usually regarded as an additional input item or independent variable. In order to eliminate independent variables of the surge tank and reduce the number of unknown variables, in this article, the dynamic of the surge tank is merged into the dynamic of the penstock. First, the dynamic equation of the surge tank is transformed into the transfer function. The dynamic of the surge tank can be included into the transfer function of the dynamic inlet head of the hydraulic turbine according to the continuity equation and transfer function of the pipe. Then, transfer function of the dynamic head can be transferred into differential algebra model. This model combining with the algebraic equation of the torque forms the differential algebra model of hydraulic turbine including surge tank dynamics. In the model, the dynamic of the surge tank is no longer an additional input item or independent variable, decreasing the order of the system, reducing the variable of the equation and the computational complexity of the program. The simulation operating system is established, including a classical parallel PID controller of governor, the PI excitation controller, the third order model of generator and the hydraulic turbine model. The simulation shows that head of hydraulic turbine and generator active values of the proposed model are consistent with those of the traditional model, and the proposed model can meet the requirement of researching the transient characteristics of hydraulic turbine.
2017 Vol. 35 (4): 319-324 [Abstract] ( 838 ) [HTML 1KB] [ PDF 1542KB] ( 1205 )
325 Numerical simulation of unsteady three-dimensional flow in turbine mode of a pump-turbine
HAN Dongdong, YU Fengrong, ZHANG Siqing
In order to study the fluid flow and pressure fluctuation characteristics in the turbine mode of a pump-turbine, the geometrical model of a pump-turbine in a pumped storage power station is generated, and unsteady three-dimensional flows in the turbine mode are simulated by employing the RNG k-ε model and SIMPLE algorithm under 25%, 50%, 75% and 100%(full)load conditions, respectively. At the same time, the pressure pulsations at the inlet of volute, in the range of wicket gate, in the vaneless range between the wicket gate and the runner, in the conical diffuser and elbow of the draft tube are monitored. The results show that jet flows are issued at the wicket gate outlet under no-load and 25% load conditions, causing a deteriorated flow field in the vaneless range and a vortex structure near the runner inlet, fortunately this situation is relieved with increasing load. Under 50 % load condition, there are a few vortex rope branches to intertwine each other, the vaneless range is affected by the rotor-stator interaction of high frequency, and the flow in the draft tube is influenced by vortex ropes of low frequency, further, the interaction and rope low frequency pulsation propagate upstream and downstream, respectively. Under 75% and full load conditions, the pressure fluctuation amplitude decreases from monitoring points P1 to P5, particularly, the amplitude at point P3 in the vaneless range and point P4 in the conical diffuser declines sharply. The pulsation frequency in the vaneless range remains unchanged when the load changes, and the amplitude of various frequencies rises with increasing load.
2017 Vol. 35 (4): 325-332 [Abstract] ( 859 ) [HTML 1KB] [ PDF 3565KB] ( 1231 )
333 Performance analysis of guide vane in long-range fire- fighting water cannon
YUAN Danqing, SHI Rong, CONG Xiaoqing, JI Ming
To achieve a longer range of the most widely used fire-fighting water cannon, the vortex and the transverse flow in the tube must be eliminated.The deflector or straightener placed in the bend channel is used to reduce outlet turbulent kinetic energy in the tube. The internal flow of water cannon with 5 different curvature radius bend tubes is studied at 400 m3/h design flow. Simultaneously, the placement and number of guide vane is different. The results show that the turbulent core area can be eliminated and the flow pattern is improved evidently when guide vane is installed. When the curvature radius of the bend tube is 1.2~1.4 times the pipe diameter, the turbulent kinetic energy in the tube is greatly reduced, and its maximum turbulent kinetic energy is less than half of the case without guide vane. When the curvature radius is smaller, the pressure difference between the inlet and outlet pressure of theguide vane and the double ones is not quite different; while the curvature radius is larger than the pipe diameter, the pressure difference of the former is less than that of the latter. The single guide vane is placed near the inner wall, it not only has compact structure of the water cannon, but its pressure difference is less than that of double ones, and the vibration and rotation in the tube are relatively small.In the design of fire water cannon, we should give priority to the selection of single guide vane.
2017 Vol. 35 (4): 333-339 [Abstract] ( 1025 ) [HTML 1KB] [ PDF 2026KB] ( 1697 )
340 Predicting output power of roof wind turbine with different inflow conditions
JING Kunyao, WANG Jianwen,, ZHANG Liru,, HE Lingli
In the light of the complex and variable of terrain and wind energy on the the city building, the index, logarithmic and semilogarithmic wind profiles were established according to 3 kinds of typical surface roughness of urban and suburban to explore the influence of inflow condition on output po-wer of roof wind turbine.An S airfoil horizontal axis wind turbine was selected as the calculation modle, which was mounted at the appropriate location on the flat roof. User Defined Functions was used to load three kinds of inflow conditions, and the turbulence characteristics of the flow field and the output power of the wind turbine were numerically calculated. Results show that under the index, the accelera-tion effect is smaller and the turbulence intensity is higher, not suitable for wind turbine installation. Although the power of wind turbine is higher under logarithmic inflow, turbulence intensity is bigger, the number of wind turbine installation and appropriate location will be reduced, and there exist the problems such as structural damage and cost increase The flow separation,speed block and the turbulence intensity are all small under semi logarithmic inflow, the building wind-collecting effect is obvious, which is suitable to install more wind turbines, and can avoid the damage of wind turbine structure.
2017 Vol. 35 (4): 340-344 [Abstract] ( 919 ) [HTML 1KB] [ PDF 1699KB] ( 1129 )
345 Clogging risk and combined effect of fertigation system in groundwater containing high content of Ca2+and Mg2+
WANG Tianzhi,, WANG Di, XU Feipeng, LI Yunkai,
In order to analyze the clogging risk and combined effect of the fertigation system in the groundwater with high contents of Ca2+and Mg2+, the spring maize drip irrigation in the field was experimented. The content of Ca2+and Mg2+ in the groundwater is up to 180 mg/L. Two types of irrigation water and two types of emitters were chosen. And the fertigation security problem of the groundwater with high content of Ca2+and Mg2+ and the reclaimed water was analyzed. The results show that there was a bigger security problem in fertigation with the groundwater with high content of Ca2+and Mg2+ compared with the reclaimed water. After seven times drip irrigation, the Dra and CU in the groundwater decreased to 77.6%, 79.9% respectively, and were 3.0% and 5.3% lower than those in reclaimed water. Owing to the clogging, the amount of irrigation water and fertilizer and the uniformity in the groundwater were lower than those in reclaimed water. The plant height, stem diameter, yield and water use efficiency of the spring maize in the groundwater were 7.4%, 3.5%, 3.7%, 3.7%, respectively lower than those in reclaimed water. This research can provide references for rational utilization of groundwater in the drip irrigation.
2017 Vol. 35 (4): 345-350 [Abstract] ( 1032 ) [HTML 1KB] [ PDF 1360KB] ( 1589 )
351 The relationship between soil water potential and water content of two soils
WU Yanyou,,, HU Linsheng,, GU Ruizhi,, WU Yansheng,, LI Minghong,
Soil moisture characteristic curves of the two species of soils were researched. Based on the Gibbs free energy,the model of soil water potential and water content was founded. As loam and loam clay were two common soils, the relationship between soil water potential and moisture losing time with four soil water levels was monitored, and Logistic equation was used to fit the relationship between soil water potential and water content. The results showed that the established model based on Gibbs free energy was quite feasible since the relationship between soil water potential and moisture losing time can be well fitted by Logistic equation. And the relationship between water content(calculated by the model of soil water potential and water content)and moisture losing time can be well fitted with Logistic equation. The field water capacity of loam clay was 11.6% higher than that of the loam. However,the time point when water content of loam decreased to wilting moisture was later than that of the loam clay, which indicated that the water-holding capacity of the loam was obviously higher than that of the loam clay. This research could provide the real-time irrigation technical support for the information of crop water demand.
2017 Vol. 35 (4): 351-356 [Abstract] ( 1283 ) [HTML 1KB] [ PDF 1322KB] ( 2241 )
357 Development and performance test of lateral move irrigation system
TIAN Kun, ZHU Xingye, WAN Jinghong, BAO Ya
A novel lateral move irrigation system was introduced based on the development trend of Sprinkler Irrigation system at home and abroad at present.The unit adopted the special connecting to realize the fast connection and disassembly of the device. The span number was flexibly changed for avoiding excessive spray and spray leakage phenomena of the unit with more special truss connections according to the terrain demand. The truss was equipped with special slotted manner which could change the nozzle installation height and spacing flexibility according to the crop water requirement. And it also could reduce floating and evaporation loss of sprinkler irrigation and improve the sprinkler irrigation uniformity. A low-pressure and spray-plate sprinkler nozzle equipped reduced the system pressure and saved energy consumption. The lateral move irrigation system adopted the intermittent control system to realize automation operation of the unit and fulfilled the requirements of modern far-ming precision irrigation. By analyzing the performance of the unit, the results show that when the pressure, sprinkler spacing and the height are 0.07 MPa,3 m and 1 m respectively, sprinkler irrigation uniformity coefficient reaches 86.5% and distribution uniformity coefficient reaches 80.9%. Compared with existing products, the unit has the advantages of easy disassembly, extensive adaptability, water saving, energy saving and high uniformity, so it has considerable prospects of applications. 
2017 Vol. 35 (4): 357-361 [Abstract] ( 691 ) [HTML 1KB] [ PDF 1453KB] ( 1148 )
362 Characteristic parameter wireless monitoring system of hydraulic turbine based on Android
WU Chen, TANG Yue, TANG Lindi, CHENG Jun, LI Ke
In order to achieve wireless monitoring of hydraulic mechanical performance of hydraulic turbine, a hydraulic turbine characteristic parameter monitoring system based on Android was presented. STM32 was used as core to build the lower machine of hydraulic characteristic parameter monitoring system,acquiring inlet and outlet pressure through A/D conversion,and acquiring the numerical value of flow,torque and speed in the manner of measuring frequency. STM32 conducts preliminary processing of data and shows them on the TFT LCD screen,simultaneously transfers data to the upper machine and Android phone respectively through serial port or Bluetooth. The upper machine is programmed by Qt,aimed at displaying real-time data,drawing relative curve as demand,as well as generating report diagram,the feature of cross-platform of Qt makes it easy to transplant software to different operating systems. A relatively supporting Android APP needs to be installed,receiving data through bluetooth to achieve the function of displaying real-time data,saving to database and drawing curve,etc.The result of field-test shows that the lower machine can accurately receive and process data transmitted by sensor,the upper machine and Android client can both receive,process data as well as draw curve in particular data link,which greatly improves the experience of users,human-computer interaction,system expansion and migration.
2017 Vol. 35 (4): 362-368 [Abstract] ( 727 ) [HTML 1KB] [ PDF 1817KB] ( 1167 )
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