Experimental investigations on direct injection diesel engine with ceramic coated combustion chamber with carbureted alcohols and crude jatropha oil

Alcohols and vegetable oils are important substitutes for diesel fuel, as they are renewable in nature in the context of depletion of fossil fuels. Compression ignition (Cl) engines, due to their excellent fuel efficiency and durability, have become popular power plants for automotive applications. Vegetable oils have energy content suitable to be used as compression ignition engine fuel. Problems associated with crude vegetable oil (high viscosity and low volatility) and alcohol (low cetane number and energy content) call for engine with low heat rejection (LHR) combustion chamber with its significance characteristics of higher operating temperature, maximum heat release, higher brake thermal efficiency and ability to handle the lower calorific value fuel. Investigations were carried out to evaluate the performance of the engine with LHR combustion chamber consisting of ceramic coated cylinder head fueled with crude jatropha oil with carbureted alcohol with varied injection timing and pressure. Alcohol (ethanol/methanol) was inducted through a variable jet carburetor, installed at the inlet manifold of the engine at different percentages of jatropha oil [at full load operation by mass basis at manufacturer's recommended injection timing of 27 degrees bTDC (before top dead center) with conventional engine (CE)] during suction stroke and crude jatropha oil was injected at near end of compression stroke. Comparative studies were made with pure vegetable oil operation with similar operating conditions and also with alcohols. Engine with LHR combustion chamber with maximum induction of alcohol along with injected crude jatropha oil showed improved performance over CE at 27 degrees bTDC and 31 degrees bTDC. However, it increased nitrogen oxide (NOx) levels. Ethanol operation showed improved performance with CE, while methanol operation showed improved performance with engine with LHR combustion chamber. Alcohol operation increased aldehydes drastically with both versions of the combustion chamber with varied engine parameters, when compared with pure vegetable oil operation. (C) 2015 Elsevier Ltd. All rights reserved.