Development of Compression Spring Variable Valve for Exhaust Mufflers

The primary function of exhaust muffler is to reduce noise from the internal combustion engine without affecting its performance due to the impact of higher back pressure. The exhaust system back pressure is directly related to the engine fuel efficiency. The consumption of back pressure by the emission control system in BS IV regulation is about 30% from the total permissible engine limit, whereas in BS VI consumption is about 70%. The combination technologies used in BSVI and forthcoming RDE regulations such as TWC, GPF, DOC, DPF and SCR increases significant back pressure in exhaust system, hence the engine performance decreases. This demand robust method to control the exhaust back pressure for better fuel efficiency. Emission, noise and back pressure are the non-complimentary parameters in exhaust system development. The variable valve technology introduction in muffler is one method to optimize the above parameters. In general, mechanical variable valve in muffler containing torsional spring is used to improve the acoustics in lower rpm and to reduce exhaust backpressure in higher rpm. This paper deals with development of variable valve with compression spring as an alternative of torsional spring valve by using GT-POWER 1D tool. The conceptual design and working progress of new valve followed by comparative performance evaluation in acoustics and back pressure are dealt with in detail through simulation and validation. The new valve functioning with compression spring achieved 15% improvement in back pressure at higher rpm and 7% improvement in exhaust order noise at lower rpm.