CFD Analysis of Exhaust Manifold of Multi- Cylinder SI Engine

In present century, spark ignition engines have become a non-separable part of the society, and are used in many sectors of energy. They act as backbone for transportation systems, but, as a bitter truth they behave like a major source of air pollution. There are basically three types of emissions, emerged from a SI engine; exhaust emissions, evaporative emission, and crankcase emission, and the major pollutants emerged from these engines are CO, CO2, SOX, NOX. Present project work aims at reducing emissions. It is a well-established fact that smooth combustion minimizes the emissions, and exhaust process contributes a lot in accomplishing smooth combustion process. In present project work, different designs of exhaust manifold for a multi cylinder spark ignition engine are optimized for reducing emissions, by evaluating back pressures and exhaust velocities. For this purpose four different designs, namely, short bend center exit, short bend side exit, long bend center exit with reducer, and long bend side exit with reducer are considered, and their performance is evaluated for different loading conditions. As a result performance scores of different models based on back pressure and exhaust velocity are evaluated, and on the basis of these scores, overall performance score is investigated. In next step, on the basis of overall performance score, ranking of different models is carried out. The results show the suitability of short bend centre exit model for the purpose, as it scores better rank in the analysis. The analysis is carried out on virtual models of manifolds. Models of manifolds are developed on CATIA v5 modelling software, and for the purpose of analysis ANSYS Workbench is used.