Comparative investigation of the effect of hemispherical and toroidal piston bowl geometries on diesel engine combustion characteristics

Diesel engine parameters are in general more compatible with operating on neat diesel than biodiesel and its blends. Therefore, optimizing operating conditions as well as piston bowl geometry to achieve a better performance with biodiesel in conventional diesel engines is highly essential. In the present study, hemispherical piston bowl geometry (HPBG) of existing diesel engine was modified into toroidal piston bowl geometry (TPBG) to evaluate the performance of a diesel engine running on a 20% blend of dairy scum oil biodiesel (B20). The experimental results revealed increased brake thermal efficiency and heat release rate by 5.5% and 17.24%, respectively, while brake specific fuel consumption, HC emission, and CO emission were decreased by 8.75%, 15%, and 14.47%, respectively, in response to the engine modification applied. Such improvements using the TPBG could be attributed to improved fuel atomization, reduction of fuel droplet size, increased cylinder temperature, enhanced squish-swirl, and turbulence kinetic energy during combustion. The findings of the present study could pave the way for the fabrication of diesel engines, which are more efficiently compatible with biodiesel and its blends.