Performance evaluation of medium grade low heat rejection diesel engine with carbureted methanol and crude jatropha oil

Vegetable oils and alcohols (ethanol and methanol) are important substitutes for diesel fuel as they are renewable in nature. However drawbacks associated with vegetable oils (high viscosity and low volatility) and alcohols (low cetane number) call for engine with hot combustion chamber with its significant characteristics of higher operating temperature, maximum heat release, higher brake thermal efficiency (BTE) and ability to handle the lower calorific value fuel. Methanol was inducted into the engine through a variable jet carburetor, installed at the inlet manifold of the engine at different percentages of crude vegetable oil at full load operation on mass basis. Crude vegetable oil was injected at near end of compression stroke. Performance was evaluated with engine with LHR combustion chamber consisting of air gap (3mm) insulated piston with superni (an alloy of nickel) crown and air gap insulated liner with supemi insert with mixture of carbureted methanol and crude vegetable oil with varied injector opening pressure and injection timing. Comparative studies were made with crude vegetable oil operation on engine with LHR combustion chamber at similar operating conditions. Performance parameters and exhaust emissions were determined at various values of brake mean effective pressure. Aldehydes were measured by the 2,4, dinitrophenyl hydrazine (DNPH) method. Combustion characteristics were measured with top dead center (TDC) encoder, pressure transducer, console and special pressure-crank angle software package at full load operation of the engine. The optimum injection timing with crude vegetable oil operation on LHR combustion chamber was 29 degrees bTDC The maximum induction of methanol was 55% at recommended injection timing (27 bTDC), while it was 50% at optimum injection timing. With maximum induction of methanol, at an injector opening pressure of 190 bar, at recommended injection timing, engine with LHR combustion chamber increased peak brake thermal efficiency by 6%; at full load operation it decreased brake specific energy consumption by 2%, exhaust gas temperature by 16%, coolant load by 11%, volumetric efficiency by 6%, sound levels by 8%, particulate matter by 45%, NOx emissions by 46%, increased formaldehyde emissions and acetaldehyde emissions drastically, increased peak pressure by 23% and maximum rate of pressure rise by 17% when compared with crude jatropha oil operation at similar operating conditions. (C) 2014 Elsevier Ltd. All rights reserved.