A Novel Approach for Flow Simulation and Back Pressure Prediction of Cold End Exhaust System

The performance of any automotive engine depends not only upon its core engine parts but also on the effectiveness of the sub-systems attached to the engine, like the intake, fuel, engine cooling and exhaust systems. The exhaust system being a critical system of any automotive vehicle plays a responsible role of improving the ride quality of the vehicle and fuel economy. The effective design of exhaust system is critical in order to ensure the required exhaust gas is exited from the engine and at the same time the noise is attenuated. In this paper a novel approach is developed in order to characterize the flow through the cold end exhaust system and reduce the pressure drop to achieve desired performance. The exhaust system attenuates the noise from the engine without deteriorating the engine performance by ensuring an optimum value of exhaust back pressure. Exhaust back pressure is one of the crucial parameters that are always scrutinized by the automotive manufactures to ensure that the engine delivers a superior performance. The cold end of the exhaust system which consists of muffler and resonator contributes a major part in back pressure. GEM3D is used as a pre-processor for Muffler and Resonator modelling. Back pressure simulation is carried out using GT-POWER® tool. The discretization of muffler and resonator shell and pipes for element generation had played an important role in the proper prediction of back pressure and thereby reducing valuable design cycle time and cost. Detailed study is carried out with different shell and pipe discretization element size and shapes. Optimum combinations are derived based on the study which correlates well with the testing. A graph is plotted between flow rate vs pressure drop. This methodology can be used in system level simulation of Exhaust system with good accuracy. This approach shall be applied for future vehicle programs at the early stage of product development.