Optimization of combustion bowl geometry for the operation of kapok biodiesel - Diesel blends in a stationary diesel engine

The purpose of this research work is to optimize the combustion bowl geometry of a single cylinder stationary diesel engine for the effective operation of KME (kapok methyl ester) - diesel blends. Considering that the reported design modification would render the benefit of adaptation of higher blends of KME, in this study, two different combustion chamber geometries such as TRCC (trapezoidal combustion chamber) and TCC (toroidal combustion chamber) were chosen in addition to the convention design of HCC (hemispherical combustion chamber). In the experimental investigation, suitable blends such as B25 (25% KME + 75% diesel), B50 (50% KME + 50% diesel), B75 (75% KME + 25% diesel) and B100 (100% KME) were tested in a diesel engine with various combustion chamber geometries as mentioned above. Based on the results obtained from this study, TCC was shown to exhibit better performance and emission than TRCC and HCC for all test blends. Further, when compared to diesel, B25 and B50 were found to be the optimum blends with HCC and TCC, respectively, while TRCC seldom evinced better engine characteristics for any of the blends. Categorically, B50 showed a 5.2% increase in BTE (brake thermal efficiency) than diesel with TCC, whereas emissions such as CO (carbon monoxide) and smoke were reduced by 15.7% and 7.8%, respectively, with a comparable NOX (nitrogen oxides) emission with diesel. Similarly, combustion for B50 with TCC was found to be better than diesel, manifesting an increase in maximum heat release rate that that of diesel. Conclusively, from the experimental study, TCC was recognized as an ideal choice of combustion chamber design for the operation of blends up to B50 in a diesel engine.