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Journal of Drainage and Irrigation Machinery Engin
 
2014 Vol.32 Issue.12
Published 2014-12-25

article
article
1013 Sizing and performance features of rotary and reciprocating positive displacement pumps
Cooper Paul, Wang Chaowei
An overview of some popular rotary and reciprocating positive displacement (PD) pump types is given with the objective of presenting and comparing the respective sizing relationships and performance features. Reciprocating pumps discussed are the piston and plunger types. Rotary pumps addressed are gear (external and internal), vane, lobe, screw, and liquid ring pumps. To put the relative pump sizes in perspective, attention is fixed on the rotors or reciprocating elements of PD pumps, just as impellers indicate the sizes of rotodynamic pumps. The size of a PD pump is found from a dimensionless combination of displacement flow rate, rotative speed and diameter. The flow rate, head (or pressure rise) and power are related through the component efficiencies. The cavitation coefficient, often close to unity, connects the rotor tip speed or piston speed with the required NPSH, which can also be affected by the pressure rise of the pump due to leakage across the internal clearances. Operational effects due to cavitation, ingestion of gas or abrasives, and viscous and nonNewtonian fluids are discussed.
2014 Vol. 32 (12): 1013-1022 [Abstract] ( 1031 ) [HTML 1KB] [ PDF 1624KB] ( 870 )
1023 Unsteady hydrodynamic excitation characteristics in centrifugal pump
Yang Minguan, Wang Xingning, Gao Bo, Zhang Ning, Wang Jun
The structural mesh and k-ω turbulence model were used to study the unsteady flow cha-racteristic of whole flow field in a centrifugal pump and to analyze the unsteady excitation characteristic under different working conditions.This study focused on the analysis of pressure pulsation at different locations under different working conditions and a hydrodynamic forces on the single blade, discussed the influence factor that induced the radial loading of the single blade under each revolution.It shows that, the blade passing frequency is the dominant frequency both in the pressure pulsation frequency spectrum and the impeller radial force spectrum, while the shaft frequency is the main excited frequency in the radial hydrodynamic force on a single blade.The radial force on the single blade increased with the flow, the force on single blade under low flow rate conditions is nonuniform obviously while it′s uniform close to the rated conditions or BEP.By analyzing the unsteady excitation characteristic of the single blade,the phenomenon of jet-wake at the trailing edge close to the tongue can change the blade loading significantly,the radial hydrodynamic forces is sensitive and directly related to the change of the flow structure near the volute tongue.
2014 Vol. 32 (12): 1023-1028 [Abstract] ( 977 ) [HTML 1KB] [ PDF 2202KB] ( 1501 )
1029 Hydraulic design and numerical optimization of guide vane of AP1000 model nuclear main pump
Xie Rong , Qi Heng , Shan Yujiao, Jin Weinan
Based on self-design of impeller of AP1000 nuclear main pump,the upright guide vane was designed using foundational hydraulic methods. In order to reduce the hydraulic loss in the vane flow passage, two different schemes were proposed to optimize the vane design after analyzing the CFD computational results. The first one was to directly optimize the upright guide vanes design. And the other was to redesign the upright guide vanes as twisted spatial type to match up the impeller and subsequently to optimize the vanes. In the space guide vanes design and optimization process, two different solutions were adopted to parameterize the model, and the sample database were generated. With the hydraulic efficiency of impeller and guide vane being selected as the optimization objective, ANN and genetic algorithms were used to repeatedly optimize the blade profile of space guide vanes, and finally the guide vanes were obtained with better hydraulic efficiency matching with the impeller. The influence of different numbers of guide vane on the hydraulic efficiency was also discussed to provide the theoretical guidance and reference in hydraulic performance.
2014 Vol. 32 (12): 1029-1034 [Abstract] ( 1335 ) [HTML 1KB] [ PDF 2380KB] ( 1128 )
1035 Experiment for effect of frequency converter harmonic on speed regulating pump unit efficiency
Tang Lingdi, Yuan Shouqi, Tang Yue, Gu Zhe, Wang Hui
Frequency control technology is an effective way in energy-saving for pump unit. In order to obtain the effect of frequency converter harmonic on the efficiency of speed regulating pump unit, the experimental setup was designed based on the analysis of harmonic generation mechanism and the influence of harmonic on pump unit. It was an open test apparatus and included a high frequency electrical parameter measuring instrument with filtering function, a virtual instrument, etc. In this test apparatus, research object was a typical self-sucking centrifugal pump, the high-frequency electrical parameter measuring instrument was connected to the output of the inverter, and the torque-speed sensor was connected between the motor output shaft and the self-sucking centrifugal pump. Before and after filtering, hydraulic performance parameters and electrical parameters of the self-sucking centrifugal pump unit were collected, the efficiency of the pump unit was calculated and analyzed through changing the output frequency of frequency converter can regulate the self-sucking centrifugal pump rotating speed. The results show that the self-sucking centrifugal pump unit efficiency can be improved by 1% to 3% and the motor efficiency can be increased by 3% to 9% under the condition of suppressing the frequency converter output harmonic. Moreover, the lower the frequency is, the more obvious the efficiencies of both the motor and the unit are increased in the frequency range of from 20 Hz to 50 Hz. Quantitative research on the effect of frequency converter harmonic on performance of speed regulating pump unit can contribute to the speed range selection.
2014 Vol. 32 (12): 1035-1039 [Abstract] ( 1299 ) [HTML 1KB] [ PDF 1642KB] ( 1005 )
1040 Model identification and dynamic characteristics analysis of water supply system
Meng Ruirui, Tang Lingdi, Tang Yue, Huang Zhipan
In order to study the dynamical model and characteristics of the process in which the motor speed of the centrifugal pump water supply system suddenly changes at different operating points, the experiment of model identification under speed regulation operating condition is conducted based on the design of centrifugal pump water supply experimental system with speed regulating which optimizes the outlet valve structure in water supply system. The new experiment system implement step disturbance as input signal and present the changes of operating points logically. Virtual instrument and high frequency electrical parameter measuring instrument are used for data collection. The experiment is designed based on the step response method, and the model structure is obtained from prior knowledge about this system, the model parameters are estimated in Matlab system identification tool box using the method of least squares. Based on the pole-zero diagrams obtained by Matlab, the changes on dynamical model parameters and characteristics of the system running at the speed-up condition and the speed-down condition are analyzed and compared. It is concluded that model parameters of this system change while the system runs at different operating points, the estimated model is minimum phase and stable, mathematical model for the system is second order inertia and lag structure. Real-time variable parameters identification and real-time control is more suitable for the system.
2014 Vol. 32 (12): 1040-1044 [Abstract] ( 1080 ) [HTML 1KB] [ PDF 3048KB] ( 1211 )
1045 Modeling of large pumped storage units regulating system and development of its simulation platform
Zeng Hongtao, Tian Wengang, Wang Zhixin, Lin Linlin
Pumped storage power stations play an important role in peak load shifting and frequency & phase modulation in power system. Accidents in hydraulic machinery of the hydropower plant often occur in the transition process. For the convenience of transition process simulation and analysis, the establishment of mathematical model of regulating system and development of simulation platform are essential or have important value for research and application. Aiming at the difficulty of modeling of re-gulating system of large pumped storage units, piecewise modeling method is proposed for the mathematical model of long diversion system and RBF neural network modeling method is proposed for pump turbine respectively in this paper, and frequency disturbance transient under no-load condition and the increase or decrease of load are simulated. Simulation results indicate that the established models reflect the realistic characteristics of the plant to some extent. The simulation platform of the established models is developed based on LabWindows/CVI virtual instrument software, and the ActiveX interactive technology is applied for the communication between simulation platform and Matlab, which provides an ideal environment for researchers and local operators and maintainers to carry out simulation experiments, as well as providing reference for the development of similar simulation platform.
2014 Vol. 32 (12): 1045-1050 [Abstract] ( 949 ) [HTML 1KB] [ PDF 2203KB] ( 1089 )
1051 Prediction model based on influencing factors of water consumption
Wang Pu,, Wang Yizhi,, Zhang Jin, Wang Ying,
Urban water consumption prediction is full of complexity due to the different influencing factors and the uncertainty of the statistics database. A comprehensive water consumption prediction model was developed to slove this problem. Multiple approaches were integrated into this model. Specifically, the significant influencing factors of water consumption were selected by principal component analysis: then, the selected influencing factors were further classified by gray cluster analysis and gray relational analysis. Based on the evaluation of the significant influencing factors, a multilayer perceptron network was established by SPSS software, GRNN and BP neural networks were established by Matlab software. IOWA operator was also applied to the water prediction model. Consequently, a MLP-GRNN-BP comprehensive water demand consumption prediction model was developed based on the IOWA operator. The evaluation system,using the sum of squares error(SSE), the mean square error(MSE), mean absolute error(MAE), mean absolute percentage error(MAPE), mean square percentage error(MSPE)and Theil coefficient(μ), was established to evaluate the performance of the predictive models. The proposed models were applied to the city of Chongqing for the municipal water consumption prediction to verify the feasibility of these methods. The results show that the number of significant influencing factors for water consumption in Chongqing city can be reduced from 31 to 12, and the 12 significant influencing factors can be further classified into four clusters, and four kinds of the influencing factors can be analyzed and ranked respectively. MAPE, MSPE and Theil coefficient values are within 5%, when the BP, MLP, GRNN and MLP-GRNN-BP model are used in the case study, indication a good prediction.
2014 Vol. 32 (12): 1051-1056 [Abstract] ( 1355 ) [HTML 1KB] [ PDF 1350KB] ( 1043 )
1057 Surplus energy reuse of circulating water power in alumina decomposition tank
Li Yanpin,, Ju Yang, Yuan Shouqi, Chen Dexin
To make full use of the large number of surplus energy in the circulating water system of alumina decomposition tank,and to provide technical support for energy recovery of other similar system, the characteristics of circulating water system of alumina decomposition tank have been studied. Based on the size of the system, different solutions of energy recovery have been put forward. The solution of using the surplus energy to generate electricity has been mainly focused. And in view of its peculiarities,the power generation device of the circulating water system in alumina decomposition tank was designed,which is called as the integrated power generation device for using the surplus of circulating water. A circulating water protection process was proposed to solve the problem that the circulating water should not be cut down unexpectedly. An issue named inverse power will be occurred in generator when the turbine discharge is smaller than that under non-load condition. Therefore, protection method for reverse power of generator was put forward, which included the generator excitation subsystem, speed control subsystem, synchronization subsystem and protect subsystem, all the subsystems of control and protect integrated together, forming the four unity comprehensive control panel.Practices have proved that the integrated power generation device for using the surplus energy of circulating water in alumina decomposition tank is safe,reliable and stable.
2014 Vol. 32 (12): 1057-1061 [Abstract] ( 1646 ) [HTML 1KB] [ PDF 1364KB] ( 1030 )
1062 Design and characteristic of lubricating oil chamber of hydro-viscous drive clutch
Liao Xiangping, Gong Guofang, Zhou Tianyu, Peng Xiongbin
Hydro-viscous drive(HVD)clutch is a type of power transmission device using shear stress of multi-oil films, and it is especially applied to regulate speed for large fans and pumps. However, uniform pressure and velocity of lubricating oil film between friction pairs are difficult to achieve, which can lead to over heating,deformation and uneven wear problem for the frictional disks of HVD clutch. In order to solve the problems, a new type of HVD clutch with a centrifugal oil chamber was proposed. Consequently, the lubricating oil can get into the entrance to friction pairs uniformly under the centrifugal force. Based on the fluid dynamic theory,three-dimensional flow field models of two different oil channel structures were established. Furthermore, the numerical simulation of the flow field of different lubricating oil channel was conducted by the Fluent.The influence of the oil channel structure on pressure and velocity distribution of the entrance to friction pair was researched.The results show that the centrifugal oil chamber design and improve the uniformity of pressure and velocity of the entrance to friction pairs,and greatly improve the working performance and service life for HVD clutch.
2014 Vol. 32 (12): 1062-1067 [Abstract] ( 1218 ) [HTML 1KB] [ PDF 1682KB] ( 1288 )
1068 Numerical study on hydraulic performance of submerged propellers in oxidation ditch
Wu Siyuan, Zhou Daqing, Zheng Yuan
The submerged propeller is an efficient diving mix device, which is applicable for oxidation ditch treatment in industry, city and village wastewatertreatment plant. The impeller structure and reasonable rotating speed are important factors that determine flow field distribution and energy conversion efficiency. So it is necessary to use modern design methods to develop new kinds of high efficiency submerged propellers, and research the flow field characteristics of submerged propellers. On the basis of the existing form drawing, threedimensional model of submerged propellers and unstructured tetrahedral mesh were generated. Based on Navier-Stokes equations and standard k-ε turbulence model, the flow was simulated by using a simple algorithm. Through changing some design parameters of propellers, the corresponding numerical simulation results reveal that for the same impeller diameter and service area of submerged propellers, the power consumption could be reduced effectively by optimizing blade mounting angle, which can determine the best blade mounting angle and most suitable rotational speed under given conditions. The study can provide theoretical and project guidance for submerged propellers design.
2014 Vol. 32 (12): 1068-1073 [Abstract] ( 1220 ) [HTML 1KB] [ PDF 1800KB] ( 678 )
1074 Research on particle settling in rectangular ducts under effect of walls
Tang Fuping, Shi Yan, Guo Jiaojiao, Xue Jianquan, Zhang Guodong
In order to characterize wall effect of rectangular ducts on particle settling, a prediction method of wall factor was presented using Artificial Neural Network(ANN). Extracted ρf, ρp, d, d/a, a/b, K and n as feature parameters, which substantially affect particle settling velocity.Culled 70 data of Machac′s paper to train and test the models, and compared predicted results of ANN with the calculated results of Miyamura correlation and Liu Malin correlation.The results show that, the accurate of ANN predicted results is great, the error is less than 7.5% for 90% calculated results. Comparing to Miyamura correlation and Liu Malin correlations, the ANN model has high engineering accuracy in parallel plate and rectangular ducts, and the application range of ANN has broader scope of application,and can meet complex engineering needs.
2014 Vol. 32 (12): 1074-1078 [Abstract] ( 997 ) [HTML 1KB] [ PDF 1449KB] ( 1012 )
1079 Effects of water-logging stress on net photosynthetic rate changes of winter wheat
Xiao Menghua, Hu Xiujun, Fang Kai, Miao Zimei
Based on the water level control technology, a field experiment was conducted to study the water level regulation and control on variation of net photosynthetic rate, at different growth stages, water depth and deep groundwater of winter wheat farmland. The experimental results showed that: floo-ding depth shallow and moderate duration on winter wheat had minimal impact on photosynthetic rate, with the same water level and water-logging duration, the faster water felled the larger net photosynthe-tic rate increased; under different water control conditions, variation curves of each growth stage of winter wheat in net photosynthetic rate was appeared "M" shape. With the increase of photosynthetic active radiation enhancement and temperature increases rapidly in the morning, with the effect of radiation attenuation and temperature decreased greatly decreased at afternoon, but the change was slow at noon. The net photosynthesis rate peak value appeared in 11:00 and 13:00, decreased significantly in 12:00, namely "noon break" phenomenon; lastly, wheat net photosynthetic rate had a certain correlation with photosynthetic active radiation, solar radiation, air temperature, air relative humidity and wind speed. The net photosynthetic rate had strong correlation between total solar radiation and photosynthetic active radiation, but weak correlation between air temperature, air humidity and wind speed.
2014 Vol. 32 (12): 1079-1084 [Abstract] ( 1177 ) [HTML 1KB] [ PDF 1530KB] ( 967 )
1085 Effect of infiltrated by fresh and saline water alternately on water-salt distribution properties
Wu Zhongdong, Wang Weihua, Zhang Zhaolu, Huang Rugao, Li Tao, Zhang Zhenhua
In order to solve the problem of freshwater shortage, utilize water resource sustainably in arid and semiarid region, and make the best use of saline water in shallow ground water, saline-fresh water alternately continuous infiltration, contrast with all freshwater and all saline water, was taken to study the water-salt distribution in soil profile and soil physicochemical properties. It showed that, the alternate sequence affected the formation of the macropores and lead to the difference of water permeability of soil, the amount of salt which comes from irrigation water is the main factor of soil salt; the extension of irrigation time help to improve the desalting depth of soil profile, the infiltration sequence fresh-saline-saline is the best to salt-leaching effect; it makes the sodium adsorption ratio in 20 cm depth increase under each kind of fresh-saline water combination, the soil permeability will be decreased especially infiltrated all by saline water, it will probably lead to the soil secondary salinization, this study provides an basis to the reasonable utilization of saline water.
2014 Vol. 32 (12): 1085-1090 [Abstract] ( 1112 ) [HTML 1KB] [ PDF 1395KB] ( 1142 )
1091 Effect of planting density on root-shoot growth and water utilization efficiency of seed corn
Li Donghao, Jiang Xuelian, Tong Ling
To study the growth and water depletion of seed corn with different planting densities, field experiments were conducted from March to September, 2012 and 2013, at the Wuwei Experimental Station of Crop Water Use, Ministry of Agriculture. Five planting densities that were 67 500, 82 500, 97 500, 112 500 and 127 500 plants hm-2 were conducted in 2012, and a higher planting density of 142,500 plants hm-2 was added in 2013. The root and canopy growth, evapotranspiration(ET)and grain yield of seed maize with different densities were observed. Results indicate that the effect of planting density on crop height is not significant. There is a negative correlation between leaf area per plant and planting density. With the increase of planting density, population biomass, the root dry weight in deep soil(71-100 cm)and the ET increase, while the individual biomass, the root length, the root surface area and the bottom transmittance decrease. The water utilization efficiency and grain yield increase first and then decrease with the increase of planting densities. Considering agricultural production costs and water consumption factors, the recommended local seed corn planting density is 112 500 plants hm-2.
2014 Vol. 32 (12): 1091-1097 [Abstract] ( 1782 ) [HTML 1KB] [ PDF 1527KB] ( 1234 )
1098 Experiment and calculation of discharge time for horizontal type self-cleaning screen filter
Li Qiangqiang, Zong Quanli, Liu Zhenji, Lan Jun
Through the experiment of discharge time of horizontal type self-cleaning screen filter, the relationships between sediment content at outlet and discharge time were obtained, with six different sediment content of inlet, which are S=0.006,0.013,0.015,0.018,0.027,0.063 kg/m3, and four different flow rates, which are Q=220,200,180, 160 m3/h. The changes of sediment content at outlet with discharge time are analyzed respectively such as different sediment content at same flow rate, and same sediment content at different flow rate. The results show that the sediment content at outlet rise to the maximum first,then decrease until reaching a steady value. Therefore, the minimum of discharge time is 14 s. According to the law of conservation of mass, the calculation me-thod of discharge time is also established. Based on the experimental results, the discharge time of filter is calculated, and the value of calculted discharge time is 15-47 s. Combined experimental results of discharge time, the value of discharge time for horizontal type self-cleaning screen filter is determined, which is 15-30 s. The results are consistent with the existing filter test results and actual operating results, which can be used to predict discharge time for practical engineering horizontal self-cleaning screen filter.
2014 Vol. 32 (12): 1098-1104 [Abstract] ( 1181 ) [HTML 1KB] [ PDF 1783KB] ( 1165 )
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