Applied Mechanics and Materials Vol. 525

Abstract: Facing to the problem of hierarchical structure decision analysis which is made of scheme level + factor level + target level, the analytic hierarchy process gives a whole set of solution and process. This method is used to evaluate diesel engine simulation model. Evaluate original mean value model of large-scale low-speed marine diesel engine and the new one by this method. Calculated results prove this method is applicable.

Abstract: The process of large belt conveyor operation must be more accurate by using dynamic analysis. Dynamic analysis and complex, not easy to grasp, needanalysis software -- conveyor dynamic analysis. Based on the status analysis of the domestic belt conveyor dynamic, about software overview of belt conveyor dynamic analysis, the design principle and the belt conveyor dynamic, analysis and applicationof dynamic analysis software.

Abstract: Based on classic lateral stiffness analysis theory of flexicoil spring and rubber pad, the mechanical model and mechanical relationships of flexicoil spring with rubber pad on one end are established, and the simplified calculation formula for the lateral stiffness of flexicoil spring with rubber pad on one end is derived. By contrasted with experimental results, the theoretical lateral stiffness values of the derived simplified formula are in good agreement with the experimental results, so the derived lateral stiffness simplified calculation formula is correct and accurate. The result of this simplified lateral stiffness calculation formula can meet the requirements of engineering theoretical analysis, this calculation method can provide theoretical basis for such structures design and application, and provide parameters for dynamic calculation of railway locomotive and rolling stock.

Abstract: Aim at the dynamic reliability of stochastic truss structures under stationary random excitation. In consideration of the randomness of structural physical parameters and the geometric parameters and the random excitations were first transformed into sinusoidal ones in terms of the pseudo excitation method ( PEM) , that turned the joint-random problem into a single random problem for which only structural parameters remain random, and thus the analysis is greatly simplified. The mean value and the variance of the mean square value of the structural displacement and velocity were computed by using the theory of spectral analysis. And then the expressions of stochastic truss structural dynamic reliability were educed from the Poisson formula. Finally, the influence of the randomness of structural parameters on the structural dynamic reliability was analyzed by an example; the method of this paper was proved feasible and available comparing with the Monte Carlo method.

Abstract: Combustion in boiler blended with waste sludge can cause serious abrasion in the furnace. In this paper, Fluent6.3 was applied to establish three-dimensional numerical combustion model based on k-ε turbulence equations and Lagrangian stochastic particle trajectory to analyze a CFB (Circulating Fluidized Bed) boiler of a power plant in Guangdong province. The results show that anti-attritions will break the ring-core adherent regurgitation of the particles thus reducing erosion of particles made to the furnace wall. Furthermore, a setting of three anti-attrition ridges can prolongate the life of the wall by 2.49 times. Increasing numbers and the length of ridges are beneficial to wall, which should be limited shorter than 150mm duo to heat tube slagging, and implementing a shape of trapezoid instead of rectangle all are derived as enhancements to the feature of anti-attrition of CFB.

Abstract: In order to solve the problem of Diesel natural gas dual fuel engine, such as power reduction, low charging efficiency, the conception of diesel engine fueled with pilot-ignited directly-injected liquefied natural gas is put forward. On the basis of this theory, a medium speed diesel of the marine is refitted into dual fuel engine, in order to keep original power, decrease the temperature of combustion and reduce emission. The LNG injection timing, duration of LNG injection and the different ratios the pilot diesel to total energy are studied the method of AVL FIRE software. Conclusions are as follows: When the different ratios pilot diesel to total energy is 0.5%, the engine can not work; Delaying the LNG injection timing, shortening the LNG injection duration and choose the right ratios pilot diesel to total energy can reach the indicated power of original machine, and the NOx emissions level will be greatly reduced.

Abstract: The frequency characteristics of the valveless self-excited pulse combustor of bend tailpipe Helmholtz type with continuous supply of gas and air were investigated by experiment in this paper. The effects of bend tailpipe structure, heat load and the excess air ratio on the frequency of operation were studied. The results show that the frequency of operation decreases with the increase of tailpipe bent angle and the frequency is relatively low with the bent position at tailpipe entrance. The frequency is increased with the increase of heat load, and decreased with the excess air ratio.

Abstract: The sliding mesh method of Fluent was used to simulate the dynamic course of ball valve closure. The pressure before the valve was calculated both at constant density and variable density and compared with that of the experiment and the method of characteristic. The results show that when considering the compressibility of water, Fluent can be used to simulate the pipeline water hammer phenomenon caused by the sudden closing of the valve and it is closer to the experimental results compared with the traditional method of characteristics.

Abstract: Horizontal axis tidal turbines (HATTs) are efficient in converting tidal energy. Improvements in the design of the HATTs require a thorough understanding of the energy conversion process. In this paper, the design of a HATT with two blades is conducted by blade element momentum theory (BEM). In this simplified method, the eddy current induced by the rotors hub and tips were considered while ignoring the blade elements drag items. Based on the assumption of maximum power of blade elements, the distribution of blade elements flow angle and the chord length coefficient along the radius can be assumed to be associated only with the blade elements tip speed ratio (TSR) which is dimensionless. This approach was validated by comparing the simulation results with computational fluid dynamics (CFD). A good qualitative match between the expected value and simulation results was observed, indicating that the design method is feasible and reasonable.

Abstract: A steady state magnetohydrodynamic laminar solver with low magnetic Reynolds number has been developed in OpenFOAM platform. SIMPLE method has been used to solve the velocity vector and pressure. The induced electric potential and induced electric current has been solved according to a consistent and conservative scheme on a collocated structure grid. The solver has been validated by simulating Shercliff's case with medium Hartmann number. The results show that the numerical solution results match the analytical solutions well.