فهرست مطالب r. talebitooti

Nowadays, the issue of noise and annoying sounds is one of the major challenges in design of mufflers, that is used to reduce the noise level generated by output current of vehicles' engines. Therefore, the noise generated by the exhaust system can be controlled through predicting and calculating the transmission loss level, which is considerable and cannot be neglected. The investigated muffler has been reported to have an elliptical cross section, three straight porous tubes, four expansion chamber and three divisive plates. Generally, the main purpose of this study is to analyze the acoustic attenuation performance by using the Boundary Element Method. Also, in order to approach maximum transmission loss level, the effective geometrical parameters are optimized by using Response Surface and Taguchi methods. The results of this two methods are compared with each other. Finally, due to non-dependence of the Sound Transmission Loss level at the resonant frequencies on dimentions variation of geometrical parameters, by adding sound absorbing materials to the muffler’s shell, the acoustic attenuation performance is increased more than double and the effect of different absorptive materials in this numerical simulation is investigated.

In this paper, a method based on binary-coded genetic algorithm is proposed to explore an optimization method, for obtaining an optimal elliptical tank. This optimization method enhances the rollover threshold of a tank vehicle, especially under partial filling conditions. Minimizing the overturning moment imposed on the vehicle due to c.g. height of the liquid load, lateral acceleration and cargo load shift are properly applied. In the process, the width and height of tanker are assumed as constant parameters. Additionally, considering the constant cross-sectional area, an optimum elliptical tanker of each filling condition is presented to provide more roll stability. Moreover, the magnitudes of lateral and vertical translation of the cargo within the proposed optimal cross section under a constant lateral acceleration field are compared with those of conventional elliptical tank to demonstrate the performance potentials of the optimal shapes. Comparing the vehicle rollover threshold of proposed optimal tank with that of currently used elliptical and circular tank reveals that the optimal tank is improved approximately 18% higher than conventional one.