Development of Compression Spring Variable Valve for Exhaust Mufflers

The main function of the muffler is to reduce noise from the internal combustion engine without affecting its performance due to the impact of higher backpressure. The backpressure of the exhaust system is directly related to the fuel efficiency of the engine. BS VI and the forthcoming RDE emission control systems (hot end) use combination technologies such as DOC, DPF,SCR and multiple SCR. In BS IV application, emission control system (hot end) contributes about 30% of the total allowable exhaust backpressure, whereas in BS VI regulation the contribution of hot end system is about 70% of exhaust backpressure. The addition of hot end internals (DOC, DPF, SCR) in BS VI system increases backpressure abnormally and hence the engine performance decreases. So,there is a mandatory requirement to control backpressure of the exhaust system.Although these hot end components contribute additional value for acoustic tuning, the upcoming NVH targets demand precise optimization. Noise and back pressure are two non-complimentary parameters in exhaust system development. The variable valve technology introduction in muffler is one method to optimize the above parameters. In general, variable valve in muffler containing a torsional spring improves acoustics in lower rpm and reduces exhaust system backpressure at higher rpm. This paper deals with the development of variable valve with compression spring as an alternative of torsional spring (Flapper valve) using GT-POWER 1D tool. The conceptual design and working progress of new valve followed by acoustics and backpressure simulation and validation is dealt in detail.The new valve functioning with compression spring achieved 15% improvement in back pressure at higher rpm and 7% improvement in exhaust noise at lower rpm.