Papers by Keyword: Simulation

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Authors: Hao Wu, Yong Huang, Yu Sheng Quan, Pu Xin Shi
Abstract: This paper summarize the existing method that can explain the lightning shield failing and put forward a new method to analyze the development of the leader and the upward leader. By using time-varying electromagnetic field analytical method. Solve the dynamic potential at the streamer zone in the bottom of leader. Give a simulation analysis for the dynamic potential and find the trend grow in exponential form. Deduce the electric field and the magnetic field from the dynamic potential in time-varying electromagnetic field.
Authors: Adrian Ioan Niculescu
Abstract: The paper presents a complex quarter car model obtained with ADAMS software, View module, useful in the first stage of suspension dimensioning and optimization.The model is equipped with compression and rebound stopper buffer and suspension trim corrector.The proposed quarter car model with two degrees of freedom (wheel and body) performs all these goals allowing changing:Geometrical elementsPosition of equilibrium, depending on vehicle load;Trim correction;Elastic and dissipative characteristics of the suspension and tire;Suspension stroke;Road profile, assessed either by simple or summation of harmonic functions or reproducing real roadsBuffers (for stroke limitation) position and characteristics;The models developed provide information on:Vertical stability assessed by vertical movements of the body and the longitudinal and transversal stability evaluated based on adherence characterized by wheel ground contact force and frequency of soil detachment wheel.Comfort assessed on the basis of body vertical acceleration and collision forces to the stroke ends.The body-road clearanceThe trim corrector efficiencyAll above performances evaluated function the road unevenness, acceleration, deceleration, turning regime.The damping characteristic is defined by damping forces at different speed for each strokes respectively one for rebound and other for compression.The contact force road-wheel is defined based tire rigidity law.The stopper buffer forces on rebound and compression are defined based each specific rigidity characteristics.The road excitation is realized with a function generator.The software allow the model evolution visualisation in real time, also generating the diagrams of displacements, forces, accelerations, speeds, for each elements or for relative evolution between diverse elements.The simulation was realized for unloaded and fully loaded car using a road generated by a sum of harmonic functions presented in equation (8).The excitation covers the specific frequencies area, being under the body frequencies up to the wheel proper frequencies.The realized ¼ car model, have reached the goal to evaluate the suspension trim correction advantages.The simulations confirm the trim corrector increases the suspension performances, thus for the analyzed case the trim corrector increase simultaneous:Body-ground clearance (evaluated by body higher increasing) between 18.5÷55.1 %Body stability (evaluated by maximal body displacement) between 9.8÷11.4 %Body comfort (evaluated by maximal body acceleration) between 3.4÷35.5 %Adherence (evaluated by maximal and RMS wheel-groundcontact force variation) between 7.0÷12.1 %Body and axles protection (evaluated by buffer strike force) between 10.8÷38.2 %
Authors: R.M. Ramović, R. Šašić, R. Andrin
Authors: Meng Li, Rui Qi Wang, Jun Peng Zhang, Dong Wang, Dong Cao
Abstract: SF6 has been widely used in the power industry as an arc quenching and insulation medium due to its excellent physical and chemical properties since 1960. However, experience shows that SF6 gas medium has many disadvantages under certain conditions: gas may encounter liquefaction when installed in cold areas; SF6 is still expensive; dielectric strength is sensitive to electric field, and require higher equipment design and manufacturing processes; SF6 is a greenhouse gas, and is used under limitations since the Kyoto Protocol was signed in 1997[. Unfortunately, its difficult to find no environment hazards and to replace SF6 completely at present. In view that the greenhouse impact of SF6 is still very little (it is estimated less than 0.01%) in the atmosphere recently and it does not damage the ozone layer, it becomes a focus to find gas mixtures containing SF6 to replace pure SF6 gas to reduce the emissions and environmental impact of SF6. Scientists from all countries and international major GIS manufacturers, electric power sector are working together to develop new gas mixture of SF6-insulated electrical equipment [2].
Authors: Yu Ling Liu, P. Zhang, W.L. Wei
Abstract: In this paper, we use solid–liquid two-phase mixture model and the k-ε turbulence model to numerically simulate the effects of the position of baffles on the removal rate of solids in a sedimentation tank. The PISO algorithm is used to decouple velocity and pressure. The distribution of sludge concentration on different cross-sections is obtained by the proposed model.
Authors: Y.L. Liu, P. Zhang, W.L. Wei
Abstract: In this paper, we use solid–liquid two-phase mixture model and the Realizable k-ε turbulence model to numerically simulate the advection secondary flow and sludge concentration distribution in a circular secondary clarifier. The PISO algorithm is used to decouple velocity and pressure. The velocity field and the sludge concentration distribution are obtained by the proposed model.
Authors: Zhao Qi Zeng, Yu Kui Wang, Zhen Long Wang
Abstract: A micro air journal bearing for micro gas turbine engine is designed in this paper. 2D simulation of the aerodynamic micro air bearing is conducted to investigate the effect of the main parameters of the air bearing on the load capacity, including the clearance between the air bearing and shaft, the gear number and height of the air journal bearing, the rotational speed of rotor. The optimum value of the important parameters are explored and presented. The time correlation method is used to solve the RANS (Reynolds Averaged Navier-Stokes) equations. Requirements both from load capacity and motion stability is considered and compromised for a better and stable performance of the air journal bearing. The shaft is stably rotated in a relatively low speed of 1.18×105rpm, which is much lower than other researches and can be achieved easily.
Authors: Ming Tian Li, Xia Ting Feng, Hui Zhou
Abstract: Based on the cellular automata of the plane truss structure, a 2D cellular automata model is presented to simulate the fracture of rock at meso-level. Cellular automata are made up of cell, states, lattice, neighbor and rule. Rock is divided into lattice in which each lattice point presents a cell. Each cell is assumed to connect with several cells, which are called as its neighbors, in virtue of truss elements. The truss elements can adopt some different simple local laws, i.e. constitutive law, which may be elastic or elastic-plastic and the simple fracture rule. It also can adopt different mechanical properties, which present their heterogeneity and anisotropy. This model can make full use of the advantages of cellular automata such as its intrinsic parallelism, localization and so on. In the meantime, as a powerful tool to analyze the nonlinear, complex system, cellular automata can be used to study the nonlinear, complex fracture process. The model is used to simulate the direct tensile of the rock plates, the complete fracture process and the stress-strain curves are attained which are accordance with the experiment.
Authors: Byung Nam Kim, Masanori Watanabe, Manabu Enoki, T. Kishi
Authors: Ying Chun Liu, Jian Ming Zhang, De Long Zhang, Yan Yu Wang, Chun Guang Hou, Zi Ping Wang, Hua Xin Liu, Chun Rui Liu
Abstract: Through analysis and comparison of existing charging method works , adding more links constant current charging and constant voltage charging on the basis of the three-stage charging mode is proposed to receive more in line with rechargeable batteries five-phase characteristic curve charging mode. By scaling the control circuit and the PI regulator circuits use the charging current value and the constant voltage is sampled , a constant voltage corresponding to the error value to be compared and outputs the PWM control chip SG3525, causing the output current of the front end circuit chip , the regulation voltage , the error is gradually reduced until it reaches the steady-state output . 1 key components - integrated operational amplifier selection Integrated operational amplifier control circuit for the main components , essentially the entire op-amp circuits are designed to carry around , so choose the op amp circuit is particularly important . From the foregoing analysis, the current control and voltage control portion of each part requires three op amp ( both as an amplifier , a PI controller is used ) , the entire control circuit requires access to six integrated amplifier . Out of circuit integration considerations, decided to use a quad op amp manifold and a dual op amp with the completion of the manifold . By screening and the corresponding parameters available on the TI (TEXAS INSTRUMENTS TI ) website , and ultimately determine the use of quad op amp LF347 and dual op amp TLC2272.
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