Studies on Exhaust Emissions and Combustion Characteristics of Di Diesel Engine with Air Gap Insulation with Varied Injection Timing and Injector Opening Pressure

Abstract

Experiments were carried out to study exhaust emissions and combustion characteristics of diesel engine with air gap insulated low heat rejection (LHR–2) combustion chamber consisting of air gap insulated piston with 3 mm air gap, with superni (an alloy of nickel) crown, air gap insulated liner with superni insert with neat diesel with varied injection timing and injector opening pressure. Exhaust emissions of particulate emissions and nitrogen oxide (NOx) levels were determined at various values of brake mean effective pressure (BMEP) of the LHR-2 combustion chamber and compared with neat diesel operation on conventional engine (CE) at similar operating conditions. Combustion diagnosis was carried out using miniature Piezo electric pressure transducer, TDC (top dead centre) and special pressure-crank angle software package at full load operation. The optimum injection timing was found to be 31o bTDC (before top dead centre) with conventional engine, while it was 29o bTDC for engine with LHR–2 combustion chamber with diesel operation. Engine with LHR–2 combustion chamber with neat diesel operation showed increased particulate emissions and NOx levels at manufacturer’s recommended injection timing of 27o bTDC, and they improved marginally with advanced injection timing of 29o bTDC in comparison with CE at 27obTDC