10 research outputs found
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Thermal and mechanical stresses in thick spheres with an extended FGM model
In this study, an exact solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material with a new graded
model is presented. The temperature distribution is assumed to be a function of radius. The material properties are graded along the radial direction according to exponential functions of radial direction. The advantage of this model, compared to the other models (linear or power law models), is in satisfaction of the material boundary conditions for several types of material
variation profiles. Employing the model, the energy and Navier equations are solved using the generalized Bessel function and the Lagrange method. In addition, a method for solving the
governing equations in spherical coordinates is presented. The analytical solution of the heat conduction equation and the Navier equation lead to the temperature profile, radial displacement, radial stress, and hoop stress as a function of
radial direction
A new and efficient mechanism for spark ignition engines
International audienceIn this paper a new symmetrical crank and slider mechanism is proposed and a zero dimensional model is utilized to study its combustion performance enhancement in a four-stroke spark ignition (SI) engine. The main features of this new mechanism are superior thermodynamic efficiency, lower internal frictions, and lower pollutants. Comparison is made between its performance and that of the conventional four-stroke SI engines. Presented mechanism is designed to provide better fuel consumption of internal combustion engines. These advantages over standard engine are achieved through synthesis of new mechanism. Numerical calculation have been performed for several cases of different mechanism parameters, compression ratio and engine speed. A comprehensive comparison between their thermodynamic processes as well as vibration and internal forces has been done. Calculated efficiency and power diagrams are plotted and compared with performance of a conventional SI engine. Advantages and disadvantages of the proposed mechanism are discussed in details