Investigations on exhaust emissions of aninsulated diesel engine with alternative fuels

In the context of depletion of fossil fuels, ever increase of pollution levels with fossil fuels and escalating prices of crude petroleum in International market, the search for alternative fuels has become pertinent. Alcohols (ethanol, methanol and butanol) and vegetable oils are important substitutes for diesel fuel. Alcohols renewable in nature, have low C/H (C=Number of carbon atoms and H=Number of hydrogen atoms in fuel composition and highly volatile. Butanol has higher calorific value than ethanol and methanol. Vegetable oils comparable cetane number and energy content when compared to diesel fuel. However, the drawbacks of vegetable oils (high viscosity and low volatility) and alcohols (low cetane number and low energy content) to be used as fuels in diesel engine call for semi adiabatic diesel engine (SADE) with its significance characteristics of higher operating temperature, maximum heat release, high brake thermal efficiency and ability to handle the low calorific value fuel.Exhaust emissions from diesel engine cause severe health hazards once they are inhaled in. They also cause environmental disorders. Hence control of these emissions is immediate step and urgent. In order to take advantages from both vegetable oils and alcohols, it is proposed to use the vegetable oil along with carbureted butanol in semi adiabatic diesel engine. Butanol 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 in conventional manner. Exhaust emissions were determined with semi adiabatic engine consisting of air gap (3 mm) insulated piston with superni (an alloy of nickel) crown, air gap (3 mm) insulated liner with superni insert and ceramic coated cylinder head with mixture of carbureted butanol and crude vegetable oil with varied injector opening pressure and injection timing. Comparative studies were made with data of conventional engine (CE) with maximum induction of Butanol at similar operating conditions. Aldehydes were measured by wet method. The maximum induction of butanol was 60% at recommended injection timing of 27obTDC (before top dead center), while it was 55% at optimum injection timing of 29obTDC.