Abstract
The potential for reducing emissions on a 0.5 litre single-cylinder HSDI engine was explored in experimental work with a unit injector and a two-stage lift nozzle. A computer model of the fuel spray provided a useful means to quantify the fuel spray characteristics and rates of air/fuel mixing corresponding to the engine test results. At high speed and load, a reduction of spray hole diameter and increase of injection pressure gave a 59% increase in the rate of air/fuel mixing and reduced soot emission by 54%. At lower speed and load, an optimised two-stage lift nozzle reduced both soot and combustion noise. Simulated cycle emission results with the electronic unit injector show the progress towards future emission requirements.