Research PaperStudies on the influence of combustion bowl modification for the operation of Cymbopogon flexuosus biofuel based diesel blends in a DI diesel engine

•A novel biofuel, Cymbopogon flexuosus is used as an alternative energy source.•C20-D80 + 20 ppm profile stayed close to diesel fuel with BB.•Three different combustion bowl CB1, CB2, and CB3 were considered.•Resulting in higher thermal efficiency and lower HC, CO, emission.•Reduction of oxides of nitrogen and smoke emission for C20-D80 + 20 ppm and CB2.

The aim of this experimental work is to figure out the optimized the combustion bowl geometry on a constant speed diesel engine for its efficient functioning with a novel biofuel. The novel biofuel considered for this research work was Cymbopogon flexuosus biofuel. To improve the performance level, 20% Cymbopogon flexuosus biofuel was blended with 80% of diesel fuel (C20-D80) and to further reduce the emission magnitude, 20 ppm of cerium oxide was added to the blended fuel (C20-D80 + 20 ppm). For this study four different combustion bowls were designed based on the keen literature survey. They were hemispherical combustion bowl (BB), shallow depth re-entrant combustion bowl (CB1), Toroidal re-entrant combustion bowl (CB2), Toroidal combustion bowl (CB3). Based on the experimental evaluation, the results have been discussed for low load and full load conditions for better understanding. Regarding the fuel modification, C20-D80 + 20 ppm resulted in better engine characteristics owing to combined effect of the oxygen molecule bearing fuel and superior thermal stability and activation energy of the cerium oxide nanoparticle. Of the various bowls considered for the tests, the combustion bowl CB2 showed superior performance and emission reduction compared with its competitors CB1, CB2, and BB. It could have ascribed to the better mixing rate, gain of swirl velocity and the turbulence level of the bowl. CB2 resulted in higher BTE and lower BSEC of 4.1% and 12.02% in low and full load conditions for C20-D80 + 20 ppm. Emission reduction observed was 17% of HC, 43.66% of CO and smoke emission of 12.28% at full load condition. Peak pressure at low load resulted in negligible change but at full load for CB2 10.08% rise was achieved. It was concluded that Toroidal re-entrant combustion bowl (CB2) was the most optimized combustion bowl for C20-D80 + 20 ppm cerium nano particle powered by a single cylinder diesel engine.