Fluid Dynamic and Mechanical & Electrical Control Engineering

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Authors: Rico H. Hansen, Anders Hansen, Torben O. Andersen
Abstract: A key component of upcoming secondary controlled fluid-power systems for e.g. wave energy is the implementation of discrete force control of cylinders by discrete variation of the cylinder displacement. However, as the discrete control is implemented by shifting between fixed system pressures in multiple cylinder chambers using on/off valves, the energy efficiency of the performed shifts is essential for the total system efficiency. However, pressure shifting on a volume, where the dynamics of pressure propagation in the pipelines is negligible have been proved to have an unavoidable minimum loss due to the compressibility of the fluid. This paper performs a simulation study, showing that an improved energy efficient shift may be implemented by utilising the pressure propagation in the line between valve and cylinder chamber.
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Authors: Lian Cheng Ren, Jiang Meng, Zhen Zhen Lei, Jiu Hua Wang
Abstract: On bases of numerical simulation and theoretical analysis, two cases of media, water and slurry (a kind of pseudoplastic power-law fluids), were used in the same hydrocyclone under the same operating condition. The Compare results show that the effect of the medium viscosity on the radial-velocity profile is slight; on the other hand, the effect of the media viscosity on the tangential-velocity profiles is important. The increase of the media viscosity produces not only the increase of the viscous resistance but also the steep reducing of the peak value of tangential-velocity profiles, which means that the inward viscous force loading upon the particles are enforced, on the other hand , the outward centrifugal force loading on the particles reduces greatly. The increase of the media viscosity leads to the great decrease of the separation ability of a hydrocyclone.
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Authors: Xiong Zhou, Er Ping Wan, Peng Zhang
Abstract: Water-cooled roller is the core component of the production of negative plate of electrolytic lead, and the thickness and uniformity of negative plate of electrolytic lead is determined by flow field of internal cooling water of water-cooled roller. In order to catch the distribution of flow field inside of water-cooled roller and guide the design, the moving reference frame technology in fluent software is used to numerically simulate the 3d flow in water-cooled roller and display the characteristics and state of the flow inside the water-cooled roller Intuitive. The optimal aperture of water hole is obtained through the contrastive analysis of simulation of different apertures of water holes. The performance of water-cooled prototype meets the requirements of field investigation, also the thickness and uniformity of negative plate of electrolytic lead meet production requirement.
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Authors: Yun Jiang Cheng, Shu Han Wang, Xiang Yang Xu, Wen Yong Li
Abstract: The jet pipe electro-hydraulic servo valve is a typical two-stage flow control servo valve, its static and dynamic characteristics are analyzed in this paper. The interaction of the mechatronic and hydraulic system is considered by multidomain simulation tool, the all key parameters are tunable and this provides the optimal possibility to develop a high-performance jet pipe electro-hydraulic servo valve.
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Authors: Henrik C. Pedersen, Per Johansen, Cemre Yigen, Torben O. Andersen, Daniel B. Rømer
Abstract: The focus of the current paper is on a small 18 cm3/rev Digital Displacement Pump (DDP), where it is investigated how temperature influency the pump behaviour and static performance. An experimentally validated model of the DDP is presented, which is the basis for the investigation. From the results it is found that although the temperature highly influences the pump behaviour it is possible to mostly compensate for this by accurately controlling the closing angle of the low pressure valve.
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Authors: Jian Hua Zhao, Dian Rong Gao
Abstract: The oil pocket of the hydrostatic worktable in the modern heavy numerical control (NC) machine tools is designed under the circumstance that the working load acts equally on the oil pockets. But when the work piece is out of the rotary center of the worktable, the working load acts unequally on the oil pockets, and then the performance indexes for the oil pockets, such as acting force, oil film thickness, hydraulic damping, rated flow, are different. Based on the eccentric working load, under the circumstance that the oil pocket provides the fluid oil with constant pressure and constant flow mode, the coupling relationship between the oil pockets is analyzed, and the expression and the relatively bar graphics are presented. To achieve the machining quality and to prevent against the totally worn-out of the machine tools, it is best to adjust one oil pocket in order to keep the oil film of all oil pockets at the same thickness. While one oil pocket is adjusted, the oil pockets are intercoupling, and then the performance indexes change synchronously. According to the characteristics of the oil pocket in the hydrostatic worktable, the expression on the coupling relationship for the oil pocket is derived, then the performance indexes are analyzed qualitatively and the curves are plotted. The proposed research analyzed qualitatively the coupling relationship on the performance indexes for the constant pressure and the constant flow oil pockets separately in the worktable. It can improve the design efficiency and the accuracy with the help of the computer programs, and provides the reference for the practical engineering.
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Authors: Xiang Hui Lu, Dian Rong Gao
Abstract: This paper analyses the flow of the double nozzle flapper valve. Three-dimensional model is established with software Pro/E, fluid analysis software is used for modeling and meshing, CFD method is applied for researching pressure, and flow characteristics of the fixed damping hole is researched when parameters of double nozzle flapper valve is varied. The results show that: the highest velocity through the fixed orifice hole is about 150m/s, the pressure is about 5.9MPa; Using orthogonal test to analyze the simulation results, it is obtained that the power losses of the double nozzle flapper with the change of the diameter, length and the angle of the fixed orifice, the influencing factors on the power losses are the diameter, length and the angle, and the best parameter combination through orthogonal table analysis is gained, which can provide the reference for the whole designing of the double nozzle flapper valve.
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Authors: Yin Zhang, Xiang Dong Kong, Chao Ai, Wen Jian Cai
Abstract: The wind energy can be transferred through an intermediate medium such as hydraulic fluids. In this paper a hydraulic system is utilized to transfer the wind energy from a wind turbine to a synchronous generator. A close loop hydraulic transfer system with fixed displacement pump and variable displacement motor is introduced and the mathematical model is obtained. The simulation of the hydraulic wind turbine is derived by using the SimHydraulics toolbox of MATLAB and AMESim. The simulation results demonstrate the effectiveness of the modeling and are useful to design the control system.
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Authors: Xiao Gang Deng, Xiong Zhou
Abstract: Due to the large-scale violent circumfluence occurred in the traditional electro-floatation (TEF), the interference to the mixture of micro-bubbles and floccules should not be neglected in the floatation. In this paper, the Pulsing Electro-Floatation (PEF) using square wave impulse direct current has been presented. The circumfluence in the inhomogeneous field of the PEF would be gentler than TEF, and the energy utilization rate would be improved. Based the theory of multiphase flow continuous medium, the conservation of momentum equation in the inhomogeneous flow field of PEF has been obtained, and liquid-bubble flow field of the PEF has been simulated using the Fluent module of the ANSYS 13.0. The research result shows that the inhomogeneous flow field in PEF has more reasonable energy distribution, less extent of circumfluence in the process of the micro-bubbles floating, and more benefit for the development and floatation of the bubbles-floccules mixture compared with the TEF. With the same current density, the energy consumption of PEF is 1/4-1/3 that of TEF, but has the similar floatation effect with TEF.
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