Experimental investigation of multi-pulse injection strategies for pollutant emissions reduction in a PCCI 3.0 L diesel engine

The aim of this work is trying to mitigate the side effects of single-pulse PCCI combustion mode – mainly ascribable to massive injections of fuel into environments particularly favorable to spray penetration and wall impingement – by the usage of multi-pulse injection strategies, starting from double up to quadruple schemes, and trying in each case to find the best calibration by tuning the input parameters under control in order to optimize the set of engine points listed below: •??1000 RPM X 94 Nm (BMEP = 3.97 bar) •??1400 RPM X 27 Nm (BMEP = 1.13 bar) •??2000 RPM X 120 Nm (BMEP = 5.02 bar) •??2000 RPM X 161 Nm (BMEP = 6.75 bar) •??2000 RPM X 200 Nm (BMEP = 8.39 bar) The procedure consists in analyzing the impact produced by each of the above parameters on a bunch of quantities of interest like: BSFC, CO, soot, HC, combustion noise (CN) and NOX, representing the quality level of the combustion; the scope is in fact to exploit smaller jets with reduced inertia to penetrate less even under favorable conditions with benefits in terms of impingement, charge preparation time, combustion efficiency, duration of the smokeless premixed-burn, pressure rise rate and related structural stress, peak-temperatures – for NOX reduction – and extension of the heat release towards the end of the cycle for post-oxidation of residual unburnt species and higher exhaust temperatures to assist the catalyst’ conversion reactions.