Numerical and experimental analysis of the behaviour of a heavy-duty Diesel engine converted to dual-fuel operations

One of the possible solutions in order to reduce NO\dx and PM emissions and fuel specific consumption in a diesel engine is to substitute a part of the diesel oil with a gaseous fuel. Natural gas, due to the high octane number, allows such substitution without great modifications to the original engine, just introducing the gas feeding system. The utilization of natural gas (usually referred as "alternative fuel") instead of oil is an important advantage of such technology in terms of energy sources. In this paper the conversion of the IVECO 8360.46R engine, for bus applications, to dual-fuel operations is discussed. Experimental tests were performed to define the general behavior of the engine, especially at partial loads. Main target of the present study was the analysis of engine requirements to maintain the same output load as the full-diesel operation, and controlling exhaust emissions. To this aim analysis of the effect of the intake throttle on exhaust emissions under partial load conditions was carried out as well. Numerical simulations were used to characterize the operative conditions of the whole engine by means of an integrated 0D-1D code. Experimental pressure data were analyzed in order to obtain important information on the combustion progress. The possibility to utilize well-known heat release rate functions to predict engine performance was also considered. The fluid-dynamics code also allowed to analyze the short circuit effect of the charge.