The effects of injector hole convergence on diesel combustion and emissions

The influence of different nozzle hole geometries in diesel spray behaviour and emissions was studied. Two multiple-hole nozzles, with different convergence ratios, were tested in an injection test rig and in a single cylinder engine. The nozzle hole diameter was changed but the injection pressure and mass flux were kept fairly constant. The tests in cold conditions were carried out with two different ambient pressures in order to obtain data from penetration and spray angle. Emission results are exhibited in terms of brake specific fuel consumption, dry soot and nitrogen oxides. Additional data from the cylinder conditions such as the burnt products' temperature and the heat release rate were obtained. Convergent nozzles presented a higher penetration rate, but a narrower spray angle. In terms of combustion, Findings showed little difference in fuel consumption for both nozzles; nevertheless, for the tested conditions divergent nozzles exhibited worse mixing rates than the convergent ones.