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Journal of Drainage and Irrigation Machinery Engin
 
2013 Vol.31 Issue.6
Published 2013-06-25
article
Article
461 Experimental study on hydraulic performance of saddle zone in axial flow pump with adjustable guide vane
In order to analyze the effects of adjustable guide vane(AGV) on axial pumps working in saddle zone, in the hope of optimizing adjusting laws, performance test of a new axial-flow pump with AGV was carried out on the pump test bed. Q-H, Q-η and Q-P curves at different guide vane angles were obtained. The effects of AGV on hydraulic performance of the model pump in saddle zone were analyzed. The results show that, at the same flow rate, head and efficiency of axial flow pump increase as guide vane angle is adjusted from 0° to -5°. With AGV, the separation vortex in the flow channel is suppressed effectively; flow regime at pump outlet is optimized obviously; kinetic energy recovery rate is improved. Head and efficiency of the pump are improved by 0.15 m (0.046 9Hd) and 193% respectively. The critical flow discharge is decreased by 0.004 94 m3/s and the range of saddleshaped zone is narrowed by 6.64%, broadening the range of stable working zone. At guide vane angle of -5°-0°, the shaft power changes little. In this experiment, the best values of hydraulic performance obtained are at -5° guide vane angle, but they can be further improved.
2013 Vol. 31 (6): 461-465 [Abstract] ( 2356 ) [HTML 1KB] [ PDF 1315KB] ( 1847 )
466 Numerical investigation of effect of bend inlet on radial force of mixedflow impeller
To investigate the effect of bend inlet on the dynamic characteristics of mixedflow impellers, adopting numerical simulation method, the performance and characteristics of radial force of mixedflow impellers installed at the point of three pipediameter long away from the bend and on the straight pipe respectively were simulated and analyzed. After steady analysis of the flow field and comparing the axial speed distributions at the impeller inlet, the results show that axial velocity distribution at the inlet has obvious velocity differences in bend plane with bend inlet, but the performances of pumps with straightpipe inlet and bend are basically identical, corresponding with test results. the unsteady simulations under designed flowrate show that the impeller with straight pipe inlet almost has no steady radial force, while the impeller with bend inlet has an obvious increase of steady radial force, especially the unsteady radial force at blade passfrequency, but the unsteady radial force caused by activity and inertia interference remains basically the same. These analyses can be referential for fixedflow and structure design with bend inlet.
2013 Vol. 31 (6): 466-470 [Abstract] ( 1835 ) [HTML 1KB] [ PDF 1981KB] ( 1622 )
471 Performance optimization for refueling pumps
 For a particular air refueling power system model which consists of RAT and a centrifugal fuel pump, on the premise of maintaining constant RAT, using the hydraulic design to optimize the performance of the refueling pump, thus the development needs of the system as a whole to improve the output power was satisfied. Firstly, using CFD method, the refueling pump was redesigned to optimize the performance. Full threedimensional numerical simulation is applied to the optimized model. After repeatedly iterative optimization processes, the final optimized design was finally obtained. Secondly, based on optimization results, specimen products were made and tests were performed to verify the design. The comparison of test data and simulation results shows that, after cycling optimization procedure of theoretical design, numerical simulation and theoretical redesign, the optimized pump′s performance is superior to that of the original one. The analysis of the internal flow shows that the vortexes in the optimized flow domain are smaller and weaker. Compared with the original one, the optimized pump′s efficiency is increased by 8%, and the pumping pressure is raised by 10%. The results of this study can help enhance the reliability of system operation and solve the matching problem of the system and provide reference for optimal designing of other airfuel pumps.
2013 Vol. 31 (6): 471-474 [Abstract] ( 2066 ) [HTML 1KB] [ PDF 2901KB] ( 1614 )
475 Numerical simulation and experimental investigations of 50IB-32 centrifugal pump′s cavitation
In order to study the internal flow inherence of the impeller when the pump was in cavitation, based on Rayleigh-Plesset cavitation model and RNG k-ε turbulence model, the whole flow passage of 50IB-32 model pump under the design conditions was numerically calculated. The development of cavitation in the flow of the impeller was compared and analyzed in primary cavitation, critical cavitation, and serious cavitation. Static pressure distribution on pressure side and suction side of blade and vapor volume fraction of the blade under different NPSH were obtained by the numerical calculation. The results show that bubbles first appear in the low pressure area of the suction side of blade and then extend from the inlet to the main flow as inlet pressure decreases; bubble distribution on the blade gradually increases. In critical cavitation, bubbles extend inside the flow; in serious cavitation, the flow was filled with bubbles, which disturbs and damages energy exchange in the flow and cause overall performance curve to degrade. The results of the experiment agree with the simulation, which validates the feasibility of numerical calculation.
2013 Vol. 31 (6): 475-478 [Abstract] ( 1928 ) [HTML 1KB] [ PDF 1778KB] ( 1848 )
479 Hydraulic design and BVF diagnosis of high efficiency centrifugal pump
In order to provide diagnostic evidence for optimizing design, the boundary vorticity flux (BVF) theory was introduced to diagnose blades, with the purpose of exploring the relationship between BVF distribution on blade surface and hydraulic performance. Based on twodimensional flow theory and velocity coefficient theory, applying the parameters of IS150-125-250 centrifugal pump, a centrifugalpump impeller was designed. And selfcompiled programs were used to complete the hydraulic design of the whole flow passage of the centrifugal pump. In comparison with the blade of reference, the space bending and twisting characteristics of the designed blade are more obvious. Applying RANS (Reynolds averaged N-S) equations with a standard k-ε twoequation turbulence model, numerical simulation of the inner flow field of the two pumps was carried out and a comparison and analysis of the data of numerical simulation of two centrifugal pumps, which was obtained from 13 working condition points, inclusive of the designed conditions, was made. With the numerical results of inner flow of the design pump and model pump, applying BVF diagnostic method, the BVF distribution of suction surface and pressure surface of two pumps was analyzed. The results show that, in comparison with the centrifugal pump of reference, the designed centrifugal pump has higher head and efficiency in the range of lower flow rate, and the maximum efficiency can be increased by 5.3%; the BVF distribution of the designed pump is more even and smooth, with smaller peak values, which indicates that the BVFbased flow field diagnosis can help restrain the unfavorable flow and effectively improve the hydraulic performance of the centrifugal pump.
2013 Vol. 31 (6): 479-483 [Abstract] ( 2267 ) [HTML 1KB] [ PDF 3851KB] ( 2151 )
484 Position of guide vane trailing edge of nuclear reactor coolant pump under gasliquid two phase condition
To study the influence of different positions of guide vane trailing edge on the pressure fluctuation and gas fraction fluctuation in volute wall of nuclear reactor coolant pump under gasliquid phase condition, and find a best position of guide vane trailing edge, the threedimensional numerical software CFX was used to simulate the internal transient flow field of pump, with monitoring points set in different positions, in the hope of learning pressures and gas fraction distributions at different times and different positions within each model pump. By comparing pressure fluctuations, frequency domains and time domains at the same position of each model, it was found that the pressure is lower and steadier when the guide vane trailing edge is in the center plane of volute. In another word, the vibration and noise caused by pressure fluctuation were lower; it is the best position for safety. At the same time, it was also found that the fluctuation frequency of volute wall was influenced by impeller rotation frequency. Except similar tongue, impeller rotation almost has little effect on gas fraction distribution of volute wall and outlet.
2013 Vol. 31 (6): 484-489 [Abstract] ( 1813 ) [HTML 1KB] [ PDF 2175KB] ( 1756 )
490 Optimal operation of circulating water pump in thermal power plant under different weather conditions
Based on the circulating water pump (CWP) optimal operation model, with the whole circulating cooling water system as the subject, taking influences of different weather conditions fully on CWP optimal operation into consideration, a new kind of equivalent profit curve and corresponding net earning power curve was drawn to directly guide CWP optimal operation.Taking a 660 MW power plant for example, the proposed and previous equivalent profit curves were compared and analyzed. The results show that,the proposed equivalent profit curves can always effectively guide the CWP optimal operation. However, the CWP operation mode based on the existing equivalent profit curves is not always optimal, and the CWP optimal operation mode possibly changes due to the working CWP operation modes. In the meantime, by applying the proposed equivalent profit curves and net earning power curves, the CWP optimal operation in the 660 MW power plant was technically and economically analyzed. By comparing net earning power curves under different loads, it is found that, under summertime high temperature conditions, the operation cost of circulating cooling water system under low load may be higher than that under high load.
2013 Vol. 31 (6): 490-495 [Abstract] ( 2055 ) [HTML 1KB] [ PDF 1395KB] ( 1726 )
496 Algorithm of optimal operation with adjustableblade and  variable speed for pumping station
A mathematical model of optimal operation with adjustableblade and variable speed for multiple pump units in pumping station was made and a decompositiondynamic programming aggregation method based on DPSA was proposed. With minimal daily electric consumption as the target, water quantity pumped by units as coordinated variable, the abovementioned model was decomposed into several submodels of daily optimal operation with adjustableblade and variable speed for single pump unit. The submodel took the blade angle and pump speed as decision variables, the discrete values of water quantity pumped by each unit as state variable, and was solved by applying DPSA. The constructed aggregation model took water quantity pumped by each pump unit as decision variable, the discrete values of water quantity pumped by pumping station as state variable, and was solved by dynamic programming method. Taking the operation of a pumping station as a case, the optimal operation of multiple pump units with adjustableblade and variable speed has average cost saving of 5.80%, 25.19% and 32.20% under 100%, 80%, and 60% loads respectively.
2013 Vol. 31 (6): 496-500 [Abstract] ( 1619 ) [HTML 1KB] [ PDF 1315KB] ( 1411 )
501 Research on upper bracket resonance and air admission damping of hydroelectric unit
The stability test research for turbine generator set of Himmetli power station showed that the vibration amplitude of upper bracket was out of limits in specific load zone. Based on the measured experimental data, the relationship between vibration signals of upper bracket and pressure pulsation signals of spiral case inlet, head cover and draft tube is analyzed. The dynamic characteristics of upper bracket and stator bracket are analyzed and the natural frequency is obtained. The results show that the frequency of turbine pressure pulsation in the load zone is close to the natural frequency of upper bracket, which leads to the resonance of structure of the upper bracket. The test of air admission for vibration reduction, adding high pressure air from head cover into runner, has also been done. The results show that, through the spectrum analysis of the pressure pulsation signals of spiral case inlet, head cover and draft tube after air admission, the frequency which causes resonance has disappeared and the vibration amplitude has been reduced greatly. Based on the actual situation of power plant, some practicable measures of air admission, that is, inserting the pressure air compensating pipe under the original natural air compensating valve side, are proposed. After putting these measures into practice, no resonance phenomenon occurs when the unit operates in that specific load zone.
2013 Vol. 31 (6): 501-505 [Abstract] ( 1924 ) [HTML 1KB] [ PDF 2553KB] ( 2432 )
506 Application of hydraulic damping governor in rapid winchhoist
In order to solve repeated oscillations, heating and burning of friction plates in the operation of centrifugal governor, applying the speed control principle of hydraulic hoist to rapid winchhoist, hydraulic damping governor is adopted to improve the winchhoist governor. In this paper, the speed control principle of damping governor is expounded; and a fluid mechanics model of governor is established; flow and damping moment calculation formulae are deduced. The experiment results of QPK-2×160 kN type rapid winchhoists, equipped with two different governors, were analyzed. The results show that fluid control is mainly related to the diameter of the damper; the damping moment is inversely proportional to the square of the damper area; the damping moment increases as the angular speed of the damper increases. The hydraulic damping governor has a good damping characteristics, which can absorb load vibration, impact, reduce moment and reduce time and range of the speed surging. Only moment balance can be achieved after 2-3 oscillation absorptions. The results also show that hydraulic damper governor can prevent equipment resonance, improve system smoothness and stability, enhance the hoist reliability of winchhoist system, make gate descend at an even speed and prolong its service life, thus extend the application scope of rapid winchhoist．
2013 Vol. 31 (6): 506-510 [Abstract] ( 1977 ) [HTML 1KB] [ PDF 1420KB] ( 2235 )
511 Dynamic analysis and numerical simulation of internal wind field in air purification
To provide foundation for optimal design of the filter and the inlet and outlet of the tunnel, dynamics method was used to analyze the mechanism of air purifier and deduce theoretically filter resistance in absorption process. Starting from the internal air flow field in an air purifier, a geometric model of internal wind field was built and porous medium was adopted to simulate the filter. Fluent software was applied to numerically simulate internal wind flow. The different values of pressure field and velocity field were measured and analyzed on three crosssections of different heights (0.05 m, 010 m and 015 m) with inlet velocity changing from 1 to 5 m/s. The results show that the wind flow remains steady when inlet velocity is 1-2 m/s, HEPA filter produces the strongest flow resistance at section of 0.10 m high. Therefore, the area of air inlet and outlet should be increased to be consistent with the main wind channel so as to get better internal flow field and meanwhile to avoid vortex phenomenon and lower flow superposition effect at the outlet. Fluent software simulation produces effective results and can provide theoretical basis for solving flow field issues in practice.
2013 Vol. 31 (6): 511-516 [Abstract] ( 1876 ) [HTML 1KB] [ PDF 5258KB] ( 2132 )
517 Dynamic coefficients of small coneshaped annular seal rotor
To solve the liquid dynamic coefficients of small coneshaped annular seal and exciting force that rotor sustained, a full threedimensional model of small coneshaped annular seal was built. By applying CFD Fluent software to cavitation model, the surface pressure distribution of rotor and location of cavitation were obtained. The rotor surface pressure variation under the condition of pressure drop, ω/Ω and different rotor speed were studied, and the distribution of the gas phase was obtained. Finally, as per rotor dynamic model and excitation force formulas, seal dynamic coefficients and whirlfrequency ratio were analyzed under conditions of pressure drop 1.38, 2.41 and 3.45 MPa; rotor speed 1.02×104, 1.74×104 and 2.46×104 r/min respectively. Calculated values were then compared with theoretical values of Childs and experimental values of Lindsey. The results show that, by increasing the pressure drop, the ω/Ω or speeding up the rotor, small coneshaped annular seal gap pressure can be increased, cavitation range can be reduced effectively and the sealing performance of annular seal can be improved. The simulation results correspond closely to experimental values and theoretical values, wholly approaching the experimental values. The research can provide theoretical basis for engineering study of small coneshaped liquid annular seal.
2013 Vol. 31 (6): 517-522 [Abstract] ( 1752 ) [HTML 1KB] [ PDF 3484KB] ( 1827 )
523 Butterfly disc structure improved design and numerical analysis based on CFD
In order to analyze the effects of butterfly valve disc structure on the valve cavitation coefficient, flow resistance coefficient and the internal flow characteristics, based on finite volume method and standard k-ε turbulence model, at different opening degrees (rotation angle of valve plate), threedimensional steady numerical simulation calculation of butterfly valves of combtype and wedgetype structure discs was carried out. Velocity distribution, pressure distribution and velocity flow chart of the valves under different working conditions were compared and analyzed. The effects of velocity on the formation and expansion of the vortex was obtained. The results show that the fluid in wedgetype disc butterfly valve flows more smoothly, and the flow resistance coefficient of the valve decreases at larger opening. Therefore, it reduces the impact of flow on the valve body and passage and improves flow circulation. The cavitation coefficient of wedgetype disc butterfly valve is bigger than that of combtype disc and the anticavitation performance is enhanced. The study provides a basis for analyzing the impact conditions inside the valve and can be useful in optimizing valve design.
2013 Vol. 31 (6): 523-527 [Abstract] ( 2328 ) [HTML 1KB] [ PDF 8649KB] ( 1695 )
528 Relationship of energy conversion for Venturi injector
To understand the causal conditions and processes of negative pressure in the throat of Venturi injector, by measuring pressures at the inlet, outlet and throat for Venturi injector respectively, the energy conversion relations of water flow at different feature sections were studied. The results show that the inlet pressure energy is translated into the throat kinetic energy when water flows through the Venturi injector. As the inlet pressure energy and the discharge increase, the kinetic energy in the throat increases, when the kinetic energy in the throat reaches a certain value, the pressure energy at the throat disappears completely and the negative pressure occurs. When the negative pressure reaches the minimum value and remains stable, the flow velocity increases significantly as the inlet pressure increases. The kinetic energy and head loss in the throat also increases very quickly as the flow rate increases. At the same flow rate, the differences between actual and theoretical flow velocity could indicate the size of throat vacuum space. Compared with freeoutflow conditions, under nonfreeoutflow conditions, the starting pressure causing the negative pressure in the throat increases, and the flow volume is relatively great. To obtain the same negative pressure, the inlet pressures and flow rate under nonfreeoutflow conditions are significantly greater than those under freeoutflow conditions.
2013 Vol. 31 (6): 528-533 [Abstract] ( 1647 ) [HTML 1KB] [ PDF 1525KB] ( 1941 )
534 Structural parameter design for variable regulatorsinprecision irrigation sprinklers
In order to simultaneously control the spray field and volume of sprinklers in accordance with various shapes of irrigation area, a variable regulator design for precision irrigation sprinklers is proposed. The variable regulator was constructed with upper and lower waterblocking pieces, each of which comprises a central throughhole as well as fanshaped throughholes and fanshaped waterblocking pieces. As the sprinkler rotates, the upper and lower waterblocking pieces rotate in opposite directions. In conducting, both the watercarrying area and spray range increase; when it is closed, both the watercarrying area and spray range decrease. In this study, the structural parameters, including the central angle of the fanshaped and central throughholes for minimizing the sprinkler energy loss, were designed; based on the local resistance theory of water movement, the central throughhole diameters for the upper and lower waterblocking pieces were also designed. The results show that the variable regulator designed in this study can guarantee the minimal resistance loss at watercarrying cross section; through spray range and watercarrying area testing, it is found that the contours of sprayed areas has transformed from circles to approximately squares, with the largest range approaching closely the original nozzle range and the water distribution being even, which can meet the demand of controlling spray flow and spray range as they vary and realize variablerate precision irrigation.
2013 Vol. 31 (6): 534-539 [Abstract] ( 2492 ) [HTML 1KB] [ PDF 36624KB] ( 7539 )
540 Effects of different water treatments on growth, yield and quality of greenhouse eggplant
In order to improve watersaving irrigation and eggplant yield in greenhouse, through experiments under drip irrigation in the greenhouse, the effect of different field water capacities (respective irrigation minima of 90% of FC, 80% of FC, 70% of FC, 60% of FC, hereinafter referred as T1, T2, T3 and T4) on the crop growth, root development, fruit yield and quality were studied. The results show that, as soil water content threshold declined, plant height, stem diameter, leaf area and aboveground biomass first increased and then decreased. T2 is better than the other three treatments. Eggplant roots are mainly distributed in soil depth between 0-40 cm, which is rapidly reduced as soil depth increases. Total root length density and total root surface area density decreased as irrigation minima decreased. The highest yield was obtained under T2, which is 1.03 of T1, 1.13 of T3 and 114 of T4 respectively. There is no significant difference between the four different treatments. The crude fiber content and nitrate content in the fruit are reduced when soil moisture content is too high or too low. Higher soil moisture is conducive to the amount of amino acids in the fruit, whereas reducing VC content decreased as irrigation minima decreased. To sum, T2 is the best irrigation minimum treatment for the growth of eggplant. Under T2, the growth, yield and quality of eggplant is better.
2013 Vol. 31 (6): 540-545 [Abstract] ( 1762 ) [HTML 1KB] [ PDF 2159KB] ( 2010 )
546 Numerical simulation of soil water infiltration under bubbled root irrigation based on HYDRUS-3D
With large flow and columnar flow boundary, bubbled root irrigation is greatly different from traditional drip irrigation and infiltrating irrigation. It is therefore necessary to study water movement under bubbled root irrigation from different boundaries. Based on the theory of unsaturated soil water dynamics, combining the characteristics of soil water movement under bubbled root irrigation, an infiltration model with columnar flow boundary was established. The HYDRUS-3D software was applied to solve the model numerically. The model is validated through the contrast of measured values and simulated values of the soil moisture which change over time. The results show that the simulation results are in well agreement with measured values. The relative error between simulated and measured values is less than 10%, both of which are quite consistent. The simulation results can provide some theoretical basis for the rational design and operation of the bubbled root irrigation system. The influences on soil moisture content by dripper discharge and drivepipe opening length were studied through numerical simulation method. The results show that the rate of moisture migration increase as dripper discharge increases; the differences caused by dripper discharge decrease over time. With the same water capacity, the range of soil wetting body slightly decreases as dripper discharge increases. The increases of the opening hole areas have no significant effect on the wetting body shape and size, but it has greater influence on soil moisture distribution.
2013 Vol. 31 (6): 546-552 [Abstract] ( 2222 ) [HTML 1KB] [ PDF 2936KB] ( 1932 )
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