Experimental Study of Effect of Nozzle Diameter on Near-Field Spray Behavior of Diesel Sprays in Non-Evaporating Conditions

The near-field diesel spray process in diesel engines is the intermediate one that connects the in-nozzle flow with far field spray process and high-speed imaging techniques with high-quality temporal and spatial resolution are required in order to record this short process (< 300 μs). In this study, a high-speed charge-coupled-device (CCD) camera with the speed of up to 1,000,000 fps was used to study the near-field spray process for a diesel injector with different nozzle diameters. The tests were carried out in a constant volume vessel over a range of injection pressure and ambient pressure in non-evaporating conditions. The observed zone of the spray was where penetration length is less than 18 mm. The development of spray penetration length against time after start of injection (ASOI) was used to evaluate the spray process. The significant difference on spray penetration length development is found when the nozzle diameter varied. Injection delay decreases with the increase of injection and ambient pressure. The comparison between the experiment results and the prediction by Hiroyasu correlation demonstrates that a more accurate correlation taking into account the effect of nozzle diameter is needed in order to predict the spray penetration length in the first regime.