The current computational fluid dynamics (CFD) study presents the effect of piston bowl geometry on the performance and emissions of a direct-injection diesel engine. Different piston bowl profiles, namely, hemispherical combustion chamber (HCC), shallow depth combustion chamber (SCC) and toroidal combustion chamber (TCC), have been created with a baseline compression ratio of 17.5. CONVERGE TM CFD code coupled with the SAGE combustion model was used for numerical analysis. It is observed that the TCC piston bowl geometry renders better air-fuel mixture inside the cylinder, which leads to a homogeneous charge. Further, numerical experiments are carried out to analyze suitable TCC piston bowl geometry by varying the depth of the bowl. Out of all the cases, the case with 1.26 mm decrease in depth of bowl from the baseline (TCC) design gives better emissions and performance characteristics.
The present work focuses on optimization of biodiesel combustion phenomena through parametric approach using response surface methodology. Physical properties of biodiesel play a vital role for accurate simulations of the fuel spray, atomization, combustion, and emission formation processes. Typically methyl based biodiesel consists of five main types of esters: methyl palmitate, methyl oleate, methyl stearate, methyl linoleate, and methyl linolenate in its composition. Based on the amount of methyl esters present the properties of pongamia biodiesel and its blends were estimated. CONVERGE TM computational fluid dynamics software was used to simulate the fuel spray, turbulence and combustion phenomena. The simulation responses such as indicated specific fuel consumption, NO x , and soot were analyzed using design of experiments. Regression equations were developed for each of these responses. The optimum parameters were found out to be compression ratio-16.75, start of injection-21.9° before top dead center, and exhaust gas re-circulation-10.94%. Results have been compared with baseline case.
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