Effect of Nozzle hole Geometry on a HSDI Diesel Engine-Out Emissions

The combustion and emission characteristics of a high speed, small-bore, direct injection, single cylinder, diesel engine are investigated using two different nozzles, a 430-VCO (0.171mm) and a 320 Mini sac (0.131mm). The experiments were conducted at conditions that represent a key point in the operation of a diesel engine in an electric hybrid vehicle (1500 rpm and light load condition). The experiments covered fuel injection pressures ranging from 400 to 1000 bar and EGR ratios ranging from 0 to 50%. The effects of nozzle hole geometry on the ignition delay (ID), apparent rate of energy release (ARER, ARHR), NO_x, Bosch smoke unit (BSU), CO and hydrocarbons are investigated. The results show that the 430 VCO produced longer ignition delays and cool flames of longer durations and higher intensities than its counterpart, the 320 mini sac nozzle, under all the operating conditions At zero EGR, the analysis of the data for the two nozzles showed the dependence of NO_x on the premixed combustion fraction, and the dependence of smoke on the mixing controlled and diffusion controlled combustion fraction. The impact of EGR on this dependence is examined. Also, the trade-off between the engine-out emissions of NO_x and Bosch Smoke Unit is determined for the two nozzles.