Abstract:
In order to minimize the sound transmission due to exhaust gases, the most common and important part of the engine system is muffler. A backpressure on engine is always produce due to the use of the exhaust muffler. This back pressure represents the extra static pressure exerted by the muffler on the engine through the restriction in flow of exhaust gases. The back pressure mainly depends on the internal shape and overall design of the exhaust muffler. Design of muffler is a complex function that affects noise characteristics, emission and fuel efficiency of engine. In this study, a combine model of response surface methodology (RSM), Artificial Bee Colony and Grey analysis is used for optimizing the back pressure and other internal plates pressure of a motorcycle reactive muffler, in order to improve the performance of the muffler. For this optimization process, the design variable parameters are diameter of perforation, number of perforation and chamber size. To measure the back pressure 3D CFD based CAE software has been used. Prediction of acoustics transmission loss is an important analysis required for the development of muffler at an initial design stage. For this reason, acoustics transmission loss analysis is conducted. It is found that after optimizing the design of the muffler, the back pressure and other internal plate pressures are decreased and the acoustics transmission loss is increased that can ensure the improvement of the muffler efficiency. It has been also found that for a constant exit diameter of an exhaust muffler the back pressure varies with the change of the engine speed. Due to this variation of the back pressure, the fuel consumption per unit distance is also varies. An attempt has been made in this study to stabilize the back pressure to a suitable value by using an automated mechanical IRIS. The function of the mechanical IRIS is to provide a variable exit diameter to the exhaust muffler. An automated mechanical system will be integrated with the IRIS, so that the exit diameter will vary automatically depending on the engine speed. It has been found through 3D based CFD simulation that the back pressure remains constant for a wide range of speed of the engine. This will ensure maximum the fuel consumption per unit distance throughout the wide range of speed variation.
