Development of a diesel engine muffler using a mixture of out-of-phase split exhaust streams

Because conventional mufflers for internal combustion engines are mostly constructed using a mixture or combination of perforated ducts, baffles or perforated baffles and expansion chambers, the noise reduction is limited and backpressure is high so that the fuel efficiency is low. In this paper, a new concept for an exhaust muffler for a diesel engine based on out-of-phase cancellation is proposed. The proposed muffler uses an interior chamber with two opposing rectangular slits, by which the exhaust stream is split into two out-of-phase branches. When these two flow branches are mixed, cancellation reduces the flow speeds. This results in the low backpressure and low air-regeneration noise in the new muffler. The principle of the new muffler has been demonstrated by the numerical simulation and experiments conducted on a single-cylinder diesel engine. (C) 2010 Institute of Noise Control Engineering.