Effects of thermal barrier coating on the performance, combustion and emission of DI diesel engine powered by biofuel oil–water emulsion

Abstract

Owing to the fast depletion of fossil fuels and their skyrocketing price due to the tremendous demand, they become imperative to find renewable alternative fuels for diesel engines. Vegetable oils and their mix with diesel in various proportions, called biodiesel, have been found to be very useful in reducing the alarming consumption of fossil fuels. In the present investigation, lemongrass oil is used as an alternative fuel. The availability of lemongrass oil is adequate for Tamil Nadu and Kerala. The coating material chosen is the partially stabilized zirconium because it has low thermal conductivity and high thermal coefficient. The piston top face, cylinder head, inlet valve and the outlet valve are coated. The purpose of low heat rejection engine or coated engine during the combustion process less heat is rejected by insulating materials. In the current work, the experiment is carried out with lemongrass oil with water emulsion and diesel in a four-stroke direct ignition engine with coating and without coating at various load conditions. The diesel engine run with lemongrass oil–water emulsion (94% LGO + 5% water + 1% surfactant), and low heat rejection engine performed better and gave better brake thermal efficiency compared with raw lemongrass oil–water emulsion blend at peak load. Then, the brake-specific fuel consumption of lemongrass oil–water emulsion in the coated engine was 325 (g kW−1 h−1) which was lower than that of lemongrass oil–water emulsion (94% LGO + 5% water + 1% surfactant) in the uncoated engine. Further, combustion parameter of lemongrass oil–water emulsion blend tested in coated engine produced 60 bars in-cylinder pressure, and it was better than lemongrass oil–water emulsion in the uncoated engine. Both the cumulative heat release rate and the heat release rate were in superior range compared with lemongrass oil–water emulsion in the uncoated engine. As regards tailpipe emission, the lemongrass oil–water emulsion blend in the coated engine at peak load delivered a steep reduction in carbon monoxide, hydrocarbon and smoke emission of base diesel blend in the uncoated engine. But, on the contrary, NOx and CO2 emissions were steeply higher compared with the diesel blend that powered the uncoated engine. The entire tested parameters led to the conclusion that lemongrass oil–water emulsion used in the coated diesel engine would be a healthier and economical substitute fuel for hydrocarbonated fuels.