Abstract
Fuel combustion inside the cylinder of an engine is greatly affected by the mixing of the air and the fuel. Better mixing leads to more efficient combustion. There has been a lot of research in the past to improve the mixing of air fuel mixture in the engine. Better mixing can be achieved by modifying the designs of inlet manifold or piston head grove etc. In this Thesis the focus is on inlet manifold. This thesis compares three designs of inlet manifold for combustion efficiency achieved by them. Those designs are helical inlet manifold, spiral inlet manifold, helical-spiral inlet manifold. Star CCM+ is used as a tool to model these three inlet manifold designs, cylinder and a piston. Same tool is used to do the analysis for combustion efficiency using some boundary conditions. Stoichiometric equation was given to the program to do the calculations. CO, CO2, NO, H2, N2, H20, temperature and pressure were chosen as the results that the program should give out once the calculation is done. The comparison of these results for all the three designs would recommend the best design among three designs of inlet manifolds. When compared, among three, Helical-Spiral inlet manifold design stood the best. It had the fewer amounts of Carbon Monoxide, more Carbon Di-oxide and more Nitrous Oxide. Having more Nitrous Oxide in the exhaust gases is contradicting the thesis; however the reasons and remedies for that problem are addressed in the conclusions section. Also Helical-Spiral design had higher pressure and temperatures generated inside the cylinder than other two designs. So Helical-Spiral inlet manifold design is suggested as the best design among the three.