Applied Mechanics and Materials Vols. 212-213

Abstract: The measuring method of flow of large-scale low-lift pump, in which the differential pressure of two measuring points in inlet passage instead of the mean differential pressure of two specified section of inlet passage to calibrate the relationship between flow and differential pressure, is developed. The numerical simulation on differential pressure of two measuring points in inlet passage, which is took out earlier than the pump set test method, is carried out with the standard k- turbulence model and SIMPLEC algorithm. The comparison of the relationships fitted respectively with numerical simulation approach and pump set test shows that the calibration accuracy of two different ways is nearly same. The conclusion can be drawn that the calibration of the relationship between flow and differential pressure with CFD is feasible. The CFD-based flow measurement method, as a more simple and convenient way, can be applied in large-scale low-lift pumps.

Abstract: With the use of the RNG k-ε turbulence model and the SIMPLEC algorithm, as well as after the secondary development of the software Fluent, the velocity field and pressure field of a axial flow impeller were numerically simulated in the single-phase (clear water) and the solid-liquid two-phase conditions. The distributions of pressure, velocity and solid concentration in the impeller under the single-phase flow and the solid-liquid two-phase flow conditions were compared. This study has shown that the numerical simulation results are the same as the actual situation.

Abstract: A valve-controlled cylinder hydraulic system is used widely in engineering. The principle of the valve-controlled cylinder hydraulic system is presented. The fuzzy PID controller of valve-controlled cylinder hydraulic system is designed, and the simulation model is built. Based on the model, simulation analysis is carried out. The results show that the PID controller parameters can change with the variations of control error and control-error change rate according to fuzzy reasoning, the response error of valve-controlled cylinder is kept in a range of -0.06～0.1cm, and the required control accuracy can be obtained.

Abstract: In this paper, a model that optimal daily operation(without considering peak and valley price) of single adjustable-blade pump unit in the large pumping station along the Yangtze River is established. Where the minimum cost of energy consumption of single pump unit is set as the objective function, the periods are defined as stage variables, the blade angle is expressed as a decision variable and the daily quantity of delivery water is considered as constraint. The No. 4 Jiangdu Pump Station is taken as a study case. Dynamic programming is adopted to carry out the tidal large pumping station along the Yangtze River. Through this method, under the condition of different water quantity constraint, different average pumping head and different average tidal range amplitude,the influence of the tidal variation on optimal operation of single pump unit in the pumping station is determined. The application results shows that: With the decreased of average pumping head and the increased of average tidal range, the effect of optimal operation of adjustable-blade pump unit in the pumping station along the Yangtze River is getting more and more obvious.

Abstract: The paper proposes an idea of projection weighted area in designing a new control butterfly valve. A lot of three-dimensional numerical simulations are carried out on the new valve, and the numerical simulations give a good linear relationship between relative flow coefficient and relative valve opening. An experiment setup was established to verify the results of numerical simulations, and the results show that the CFD technology to research and design the new valve plate is entirely feasible.

Abstract: There are erosion and cavitation in the wear of flow passage components of fluid machinery at the same time. With simulating the working conditions of hydraulic turbine, this paper studies the flow field (pressure field and fluid concentration distribution) of vapor-liquid-solid three-phase on the surface of test rotary table when there are erosion, cavitation and interactive wear on the test rotary table under different environmental pressure with computational fluid dynamics i.e. CFD method, and erosion and cavitation interactive wear test is made on the rotary wear test-bed. The results show that during interaction, the pressure on test piece surface is higher than that in erosion and cavitation, and both high pressure area and bubble area appear near the cavitation hole which is shown as fish-tail shape; with the environmental pressure increased and the interaction, the pressures on test piece surface and bubble are increased, and wear is thereupon increased; Under the interaction, the numerically computational area with many bubbles and big pressure gradient is basically the same as test piece wearing area, so the numerical computational results are consistent with the test results well.

Abstract: The existance of cavitation threatens hydraulic turbines’ safe and economical operation. Traditional caviation monitoring methods are inclined to be contaminated by low-frequency environmental disturbances and strong background noises. An acoustic emission signal monitoring system for hydraulic turbine cavitation is proposed. Its hardware and software configurations are described in details, as well as the main functional modules. The test results on an 8000 kW Francis turbine with cavitations in the draft tube have shown the merits of this proposed system.

Abstract: The sedimentation in rural rivers of China are threatening the drinking water safety of rural population, affecting their living environment, and weakening their comprehensive agricultural productivity. In this paper the internal flow patterns of a sludge pump with three different recessed centrifugal impellers were analyzed based on CFD by using the turbulence model to close the time-averaged Navier-Stokes equations. On the basis of computed results their energy performances were compared that the pump with backward bent blades gets highest hydraulic efficiency and the one with forward bent blades obtains lowest hydraulic efficiency while the one with straight blades goes intermedium.

Abstract: High Speed on-off Valve (HSV), when used as the pilot valve of the proportional directional valves, can improve its dynamic characteristics，reduce dead area，improve digitization and reduce the cost. Also, we can gain core competitiveness by mastering key technology in this field. This paper did simulations with Matlab and AMESim software, studied the characteristics of High Speed on-off Valve (HSV) as the pilot valve, and finally proposed key problems that need to be solved in the next stage of the research.