Effect of ceramic coating on the performance, emission, and combustion characteristics of ethanol DI diesel engine

Abstract

Ethanol and vegetable oils played an important role for more than 70 years in many countries all over the world. Since 19th century, ethanol has been used as fuel for Compression Ignition (CI) engines. By fermenting and distilling the biomasses, ethanol can be obtained and hence it can be considered as a renewable fuel. One way of increasing the efficiency of the ethanol fuel CI engine is to use it as a Low Heat Rejection Engine (LHR). In LHR engine, the thermal efficiency of the CI engine can be increased by reducing the heat loss to the surroundings through coolant and exhaust gas. The heat can be transferred from the combustion chamber to the piston, cylinder wall and finally to the cooling water. The heat transfer can be minimized by insulating the piston and cylinder wall and coating the piston and the cylinder wall with ceramics, which can withstand high thermal stresses. The coating materials have low thermal conductivity, thus reducing the heat flux into the piston and thus the heat transfer to the coolant is reduced. In the present work, Zirconia is used for coating the engine components for lower thermal conductivity. It is concluded that sole ethanol as fuel with glow plug show a reduction in exhaust emissions with reduced efficiency compared with conventional CI engine operated with diesel fuel. But it was observed that, there is a slight increase in thermal efficiency of the engine with the retarded injection timing. Converting a conventional engine to low heat rejection diesel engine further increases the thermal efficiency and reduces the carbon monoxide and unburned hydrocarbon emissions drastically, whereas oxides of nitrogen emission are increased because of higher combustion temperature.