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Journal of Drainage and Irrigation Machinery Engin
 
2014 Vol.32 Issue.11
Published 2014-11-25
article
Article
921 Strength analysis of bulb tubular pump impeller based on
fluidstructure interaction
Tang Xuelin, Wang Xiuye, Jia Yuxia
The RNG k-ε  turbulence model and SIMPLEC algorithm are used to simulate the steady, three dimensional, internal flow field in a bulb tubular pump with up and downstream flow passages. Subsequently, the static stress in the impeller structure is analyzed numerically on ANSYS Workbench by means of sequential coupling method. The results show that the predicted performance curves of the pump are basically in agreement with the measurements. Additionally, the static pressure on the blade pressure side is higher than that on the suction side as a whole, and the low pressure appears on the blade leading edge near the impeller tip, where cavitation may be apt to occur. Impeller strength is mainly affected by centrifugal force and fluid pressure, also the peak equivalent stress and peak total displacement caused from both the centrifugal force and fluid pressure are far less than those generated by each of them. The peak equivalent stress rises with increasing flow rate, but the peak total displacement has one minimum at a flow rate. The peak equivalent stress occurs at the blade root near the blade trailing edge. The deformation of the impeller structure becomes more dominated with increasing radius, and the peak deformation appears on the blade tailing edge near the impeller tip. The results show that the impeller strength meets the requirement for operation. The presented results can provide a reference for analysis of stress characteristic of bulb tubular pump impeller.
2014 Vol. 32 (11): 921-926 [Abstract] ( 984 ) [HTML 1KB] [ PDF 1702KB] ( 1504 )
927 Hump characteristic of reversible pumpturbine in pump mode
Tao Ran1, Xiao Ruofu1, Yang Wei1, Liu Weichao2
To investigate the hump characteristic in dischargehead curve of reversible pumpturbines in pump mode, the internal flow field of a pumpturbine unit is simulated in its pump mode under different flowrate conditions by employing the detached eddy simulation (DES) method. The underlying mechanism for the hump characteristic is exploited by comparing the CFD and experimental characteristics of flow inside each passage of the unit, especially for the hydraulic losses in the diffusing passage and for the rotorstator interaction. The results show that the flow exhibits an obviously asymmetric pattern at the runner outlet as the unit is operated in the low discharge range. The asymmetric flow field is caused from the vortex and secondary flow generated in the diffusing portion of the runner passages. As a result, the hydraulic losses in the unit rise dramatically, causing a reduction in the pump head, eventually the hump characteristic occurs. Nevertheless, improving the flow pattern under the low discharge conditions can be very helpful to mitigate or eliminate the hump characteristic. The mechanism for the hump characteristic has been enunciated here. This may be referential and helpful to improve the hydraulic performance and conducive to enhance the operating stability of a reversible pumpturbine.
2014 Vol. 32 (11): 927-930 [Abstract] ( 1387 ) [HTML 1KB] [ PDF 2539KB] ( 1787 )
931 CFDbased rotational speed control method for contrarotating
axialflow waterjet pump
Shen Zhanhao, Pan Zhongyong, Li Hong, Pan Xiwei, Huang Zhenjie
To study the performance of twostage contrarotating axial waterjet propulsion pump under different rotational speed ratios, the fluid flows in a waterjet pump are simulated under different working conditions by using computational fluid dynamics(CFD) method, and the relationship between the performance and speed ratio is established, further the flow structure and turbulent energy dissipation rate are analyzed. The results show that the performance of the pump depends largely on rotational speed ratio. Through comparison, the optimum speed ratio for the best efficiency is obtained at different flow rates. When a flow rate is less than 1.0Qd, the optimum speed ratio can be realized by controlling the front impeller speed. When a flow rate is higher than 1.0Qd, however, the optimum speed ratio can be achieved by altering the rear impeller speed. Through an analysis of the velocity triangle and internal flow field at 0.9Qd, it is identified that the reduction of the front impeller speed is helpful to low angle of attack experienced by the front impeller, causing improved internal flow field and decreased hydraulic losses. These results confirm the method of speed control for the contrarotating axialflow waterjet pump is feasible.
2014 Vol. 32 (11): 931-936 [Abstract] ( 1019 ) [HTML 1KB] [ PDF 2141KB] ( 1544 )
937 New method for measuring vane profile of diffuser of 1 000 MW
reactor coolant pump
To check the vane profile of the diffuser of a 1 000 MW reactor coolant pump (RCP), which is machined by using numerical control machining technique, a set of approaches for measuring and assessing vane profile of a throughflowcomponent are proposed. Through adopting a reverse engineering analysis software PolyWorks together with a three coordinates measuring machine, the three coordinates of vane pressure and suction sides of the diffuser are measured and the root mean square of deviation of the measured profile from the designed one is figured out. Based on a statistic and theoretical analysis on the measured profile data of the vane pressure and suction sides near the vane leading and trailing edges, a formula for estimating deviation angel of pressure or suction side profile  Δβ is put forward. Moreover, a correlation for deviation angle between two vanes Δφ, and a correction formula for deviation of individual vane profile K are established. This set of methods can accurately and effectively inspect the vane profiles of a hydraulic machine and assure each profile to have the same wrap angle. Based on the measurement and evaluation of vane profiles of the diffuser of the RCP for Fuqing and Fangjiashan Nuclear Plant, all the deviation errors are allowable. As a result, the tested performance of the RCP shows that the flow rate and head deviate from the design specifications by ±2.5% and ±1.5%, respectively.
2014 Vol. 32 (11): 937-942 [Abstract] ( 1106 ) [HTML 1KB] [ PDF 1948KB] ( 1789 )
943 Blade shape optimization of centrifugal pump
impeller with adjoint method
To prevent some drawbacks in hydrodynamics optimization procedure of hydraulic machinery, such as a huge timeconsuming and the difficulty in blade shape control and update etc, an adjoint method is proposed to optimize the blade shape of centrifugal pump impellers. At first, the camber line of impeller blade of a low specific centrifugal pump is expressed as a polynomial in terms of dimensionless radius. Secondly, the governing equations of ideal fluid flow in the centrifugal pump impeller are considered as the constraints of the optimization problem; then the constrained optimization problem is transformed into an unconstrained one by introducing four adjoint variables. Finally, the variation formulas of objective function, the adjoint equations and the boundary conditions of the computational domain for the adjoint variables are deduced. The gradients of the objective function with respect to the control variables are calculated. Accordingly the blade shape is updated continually against the direction of the gradients starting with straight blade until a minimized objective function is achieved. Because the variation of flow variables is not included in the variation of objective function, the flow filed and adjoint variable field need to be simulated once only in one optimization cycle, causing a greatly reduced computing time for the optimization. The results of the case study indicate that the proposed adjoint method is feasible for blade shape optimization of centrifugal impellers.
2014 Vol. 32 (11): 943-947 [Abstract] ( 1118 ) [HTML 1KB] [ PDF 1397KB] ( 2182 )
948 Design of inducer with excellent suction performance
under multioperating conditions
Two inducers respectively with constant and variablepitch are designed to improve the suction performance of a low specific speed centrifugal pump with a flow rate ratio of 30(maximum flow rate over minimum one) based on a design principle that the head generated by an inducer should match the suction head of the main impeller of a pump. The cavitating flows in the centrifugal pumps with two inducers are simulated by using the SST turbulence model and the mixture cavitation model under a few working conditions, and the head breakdown characteristics and bubble distribution features are analyzed to disclose the mechanisms for the head breakdown caused from cavitation at various flow rates. The performance curves of the pumps with the two inducers are measured on a highspeed pump test rig. The predicted hydraulic and suction performance curves are compared with the measurements, and good agreement is achieved. It is confirmed that the design principle adopted here can be as an essential guidance on design of inducer with excellent suction performance. The head breakdown curves with decreasing inlet pressure are different from one flow rate to another. The slope of the head breakdown curve at a high flow rate is sharper than that at a low flow rate and the head declines slowly with reducing net positive suction head available. The shape of the curve at a middle flow rate is in rectangular shape. Compared with the constantpitch inducer, the variablepitch inducer is subject to an even smaller incidence angle and even high head, allowing a highspeed centrifugal pump to have a more wide range of flow rate for stable operation.
2014 Vol. 32 (11): 948-954 [Abstract] ( 1069 ) [HTML 1KB] [ PDF 2972KB] ( 1828 )
955 Comparison of conduit profiles for Siyang pumping station in Eastern
Route of SouthtoNorth Water Diversion Project
Ding Huaibo1,2, Pan Weifeng1,2
A vertical axialflow pump system will be applied to Siyang pumping station in Eastern Route Project of SouthtoNorth Water Diversion Project; hence profile 1(elbow inlet conduit plus siphon outlet conduit) and profile 2(bell inlet conduit and scroll outlet conduit) are put forward for the station in preliminary design stage. The hydraulic performance, pump structure, installation and overhaul, flow cutoff way and project investment are compared between the two profiles. After a comprehensive technical economic comparison is conducted, the following primary results are achieved: the flow patterns and hydraulic performance of profile 1 are better than profile 2, further its flow cutoff way is simpler and more reliable, and the daily maintenance work load is less than profile 2. Importantly, the pump structure of profile 2 is more complex, causing inconvenient installation and overhaul. Even though profile 1 is subject to a bigger pump house and a higher construction cost, its whole investment is still 1.465 million Yuan lower than profile 2. A conclusion can be drawn that two profiles have their own characteristics and are applicable. However, profile 1 has more obvious superiority on the whole and should be adopted firstly. According to the results of comparison and selection, eventually, profile 1 is chosen for Siyang pumping station.
2014 Vol. 32 (11): 955-962 [Abstract] ( 816 ) [HTML 1KB] [ PDF 2216KB] ( 1556 )
963 Layout design optimization of integrated pumping station and
sluice with numerical stream simulation
Lu Yinjun1, Zhou Wei1, Ming Yuemin2, Ding Guoying1
In water conservancy hub projects located at plains, usually the pumping station and sluice are integrated together for a compact layout to save land and reduce costing. However, this combined layout can result in unwanted flow patterns, such as locally reverse flow, strong lateral current and so on. Thus, as a case study, the asymmetrical layout of integrated pumping station and sluice in North Yaoguang Water Conservancy Hub Project is optimized and finalized based on twodimensional numerical stream simulations and a detailed discussion about the layout rationality and safety of navigation. It is shown that it is proper to install a diversion pier between the pumping station and the sluice upstream and downstream in order to alleviate uneven flow patterns and satisfy the safety of navigation. Additionally, the diversion pier can drive the reverse flow zones to further upstream and an increased length of the piers can reduce the velocity of lateral current. A trash rack bridge is installed in the intake of the pumping station to collect debris and improve flow patterns, causing an increased pump efficiency and operational stability. The results have significance for layout design in similar conservancy projects.
2014 Vol. 32 (11): 963-967 [Abstract] ( 921 ) [HTML 1KB] [ PDF 1449KB] ( 1701 )
968 Mixing performance of a novel passive micromixer
with logarithmic spiral channel
A passive micromixer with logarithmic spiral channel is presented in this paper. The channel is composed of two logarithmic spiral casings, and the spiral polar angle varies from 0° to 180°. The mixing performance of the micromixer is analyzed by simulating the laminar flow in it at Reynolds numbers between 0.2 and 100.0. The results show that the mixing index at the exit of the mixer decreases with increasing Reynolds number until the number arrives at 5.0. However, once Reynolds number is larger than 5.0, the mixing index at the exit increases with increasing Reynolds number. At a Reynolds number of 0.2, the influence of both coefficient b2 and width w on the mixing performance is quite little, and the mixing index is ranged from 0.6 to 0.8. The influences of the two factors on the mixing index increase with the increase of Reynolds number. At a Reynolds number of above 50.0, and b2 =0.35-0.50 as well as w=0.05-0.13, the mixing index is greater, suggesting the micromixer has exhibited a better performance.
2014 Vol. 32 (11): 968-972 [Abstract] ( 952 ) [HTML 1KB] [ PDF 2214KB] ( 1593 )
973 Thermodynamic process of interfacial gas
film in spiral grooved dry gas seal
Dry gas seals have been extensively used in centrifugal compressors. Up to now, the process of gas flowing through the seal faces is generally considered isothermal. In fact, the gas temperature varies along with the gas flowing paths. In the flowing process, several effects, such as gas compression and expansion, viscous shear of interfacial film, convective heat transfer between the gas and the seal rings, and heat transfer between the rings and the ambient medium are involved. For a typical spiral grooved dry gas seal, it is considered that just compression and expansion thermodynamic processes are experienced when a gas flows through the gap between two end faces of the seal. A relationship between viscosity and pressure of gas in the gap is established by combining Sutherland′s viscosity-temperature correlation and the process equations of ideal gas. Then the ordinary differential equations for film pressure with polytropic exponent (m) are deduced by substituting the relationship and the process equations into Muijderman′s fluid film pressure equations in a dry gas seal with spiral grooves. The gas temperature profile along the radial direction in the film is figured out by solving the film pressure equations just obtained. The results show that the film pressure in a position decreases slightly with the increase of m. The variation of gas temperature along the radial direction in the seal rings clearly demonstrates that there are compression and expansion processes when the gas flows inside the gap. When the gas is compressed, the film temperature is higher than the ambient temperature (To), and the film temperature rises with increasing m. When the gas expands, however, the film temperature decreases gradually; and the greater m is, the more rapidly the temperature drops.
2014 Vol. 32 (11): 973-977 [Abstract] ( 948 ) [HTML 1KB] [ PDF 1471KB] ( 1414 )
978 Investigation into characteristics of both wind energy
resource and wind turbines in Urumqi region
In order to evaluate the characteristics of both wind energy resource at different altitudes and wind turbines in Urumqi region, the wind speed distribution of twoparameter Weibull, variation of wind speed with altitude, wind power density and capacity factor of wind farm are analyzed. Based on the wind speed data at 10, 20, 30, 40, 50, 60 and 70 m altitudes in that region, the monthly and annual mean wind speeds, annual mean wind power density and probability distribution of wind speed are calculated in a typical meteorological year. Besides, the shape factor, scale factor and cumulative probability of the Weibull distribution at various altitudes are estimated by making use of the maximum likelihood method. Furthermore, eight kinds of small and mediumsized wind turbines are chosen to study their capacity factor and mean power output. As a result, it is shown that the wind energy resource in that region is in between available and rich zones, and the capacity factor for the selected wind turbines is quite small, ranged from 4.4% to 19.8%. This is mainly attributed to the lower mean wind speed in the region. Thus the region is unsuitable for a largescale wind farm, but smallscale wind farms or windhybrid power systems or mechanical systems driven by wind power can be a suitable option.
2014 Vol. 32 (11): 978-983 [Abstract] ( 919 ) [HTML 1KB] [ PDF 1679KB] ( 1725 )
984 Numerical simulation on hydraulic characteristics of
diaphragm pump
In order to enrich diaphragm design theory of reciprocating diaphragm pump so as to extend diaphragm fatigue life, a numerical simulation analysis is carried out on the liquid end of a diaphragm pump, and the motion characteristics of diaphragm and the influences of related parameters on the stress in it and the motion itself are investigated throughout. Because the diaphragm is deformable and driven by a unsteady pressure in the liquid end, fluidstructure interaction has to be taken into account in the simulation. The results show that the fluctuation amplitude of stress in the diaphragm is very high in a cycle of diaphragm motion, namely the maximum peak stress is as high as more than five times the minimum peak stress. The stress concentration region is located at the diaphragm edge. It has been observed that this region frequently is subject to fatigue damage in applications. When a piston stroke is less than 50 min-1, the diaphragm stress is little affected by it; or the diaphragm can experience a significantly increased stress. The ratio of pump displacement to diaphragm capacity should be lower than 85%, otherwise the diaphragm stress increases very sharply. The methods adopted can handle the change in computational domain caused from the motion of the piston and diaphragm quite well. As a result, an analysis of fluidstructure interaction has been realized for the suction and discharge processes of a diaphragm pump.
2014 Vol. 32 (11): 984-989 [Abstract] ( 1004 ) [HTML 1KB] [ PDF 1516KB] ( 1712 )
990 Root growth and distribution of spring maize
under different irrigation methods
Irrigation methods may have important influences on spring maize root growth. To investigate the effects of ridgefurrow irrigation method on the root growth and distribution of spring maize, three methods, namely conventional furrow irrigation (irrigated both sides equally, CI), alternate furrow irrigation (alternatively irrigated between north and south sides, AI), fixed furrow irrigation (irrigated one side only, FI) are attempted under field condition. The root system growth states in 0-100 cm thick soil (five layers, each 20 cm thick) located at the north and south sides of the plants are measured at tasselling, filling and maturity growth stages. The results show that the root length density of the maize irrigated with AI is larger than that with FI in 0-40 cm thick soil layer; but the density by CI is smaller in 60-100 cm soil layer. The root length density of the maize irrigated with FI in the south side is significantly different from that in the north side, however those of the maize irrigated with CI and AI don′t show such an effect. Also, the root total length and dry mass of the maize plant irrigated with AI are larger in 0-100 cm thick soil layer in the monitoring periods. Compared with FI, the grain yield, biomass yield and irrigation water use efficiency with AI are improved by 17.37%, 1842% and 17.45%, respectively. The performance of CI is in between AI and FI. The root growth and distribution in 0-40 cm thick soil layer at both sides of the plants are more greatly affected by soil water content at taselling stage. Obviously, a local irrigation is useful for root to grow in the deep soil layer, and the root growth and distribution at both sides of the plants are mostly influenced by irrigation method at tasselling stage. The root distribution is relatively uniform for the maize irrigated with CI and AI. Compared with FI and CI, AI not only can promote root growth but also increase maize yield and improve irrigation water use efficiency.
2014 Vol. 32 (11): 990-997 [Abstract] ( 1057 ) [HTML 1KB] [ PDF 2747KB] ( 1714 )
998 Experiments on conversion coefficient between electricity consumed and
water pumped for agricultural wells in Beijing plain
A series of systematic tests were conducted to calibrate conversion coefficient between electricity power consumed and water pumped for agricultural wells by means of 62 monitoring points located at different vadose zone structures and groundwater tables in the up, mid and downstream alluvial fans of River Chaobai and River Yongding. The conversion coefficients between the electricity consumed and water pumped were obtained for the agricultural wells distributed in the different alluvial fans based on the realtime water flow rate, electricity consumed and dynamic level of groundwater, which were measured by using the remote water flow rate, electricity power and dynamic groundwater level monitoring systems as well as a realtime data transmission system. It was identified that the aquifer water abundance and local groundwater level are the dominant factors for determining a conversion coefficient. Moreover, the conversion coefficients under various water abundances and groundwater levels were compared, the coefficient is in a range of 2.53-4.88 m3/(kW·h) for the counties and districts in Beijing. Not only can this outcome provide a technical support for an electricity-water conversion metering system to be applied in Beijing even in the whole nation, but also it can improve the accuracy of the system.
2014 Vol. 32 (11): 998-1004 [Abstract] ( 862 ) [HTML 1KB] [ PDF 2277KB] ( 1695 )
1005 Effects of water, fertilizer and super absorbent polymer on growth and
water use efficiency of Jatropha curcas L.
Rong Ye1, Yang Qiliang1, Jiang Yubo2, Liu Xiaogang1, Liu Yanwei1, Wang Weihua1
A series of pot grown experiments are conducted to investigate effects of water, fertilizer and super absorbent polymer(SAP) on saplings growth and water use efficiency of Jatropha curcas L.. Two watering levels, i.e. W1: 40%ET and W2: 80%ET, two fertilizer levels, N1: 0.25 g/kg and N2: 0.5 g/kg) as well as two SAP levels, S1: 0 g/kg and S2: 2 g/kg are applied in the experiments. The results show that under N2S2 condition, the total dry mass of Jatropha curcas L. in W1 treatment is significantly reduced by 7.2% and the water use efficiency is increased by 43.2% compared with W1 treatment. Under W2S2 condition, however, the total dry mass and water use efficiency of the plant are increased 14.4% and 10.5% in W2 treatment, respectively, compared with N1 treatment. Hence, S2W2N2 should be the best condition for the saplings of Jatropha curcas L. to grow. Further, SAP can significantly improve the root system, extend the canopy and add the whole plant dry mass. At N2 level, under S2W1 condition, water is saved by 35.1%, the plant height rises by 29.0% and the evapotranspiration quantity is reduced by 45.3%; fortunately, the root and canopy mass as well as the total dry mass are heaved by 14.5%, 21.8% and 20.3%, respectively, causing an as high as 98.6% total water use efficiency, compared with S1W2 condition. Therefore, applying SAP can suppress evapotranspiration quantity and reduce the loss of water in soil; additionally, it promotes the accumulation of dry mass in the plants by means of the coupling effect with fertilizer. Eventually, the water use efficiency can be improved greatly.
2014 Vol. 32 (11): 1005-1012 [Abstract] ( 1440 ) [HTML 1KB] [ PDF 1491KB] ( 1802 )
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