Experimental investigation on free and impingement spray fueled with methanol, ethanol, isooctane, TRF and gasoline

Characteristics of free and impingement spray fueled with methanol, ethanol, isooctane, toluene reference fuels (TRF) and gasoline were investigated by using a Phase Doppler Anemometry (PDA) system with a direct injection gasoline injector. Results show that all these fuels performed a similar impingement process: a large fraction of incoming droplets adhered to the wall because of the stick and spread mechanism according to empirical transition criteria. The size of reflected droplets reduced compared to incident droplets, which indicated these reflected droplets were derived mainly from splash process. Incident droplets characteristics were affected by preceding reflected droplets through energy and mass exchange, hence the following outcomes. Among these fuels, ethanol and TRF were characterized with larger incident droplets because of high possibility of coalescence with reflected droplets. Ethanol droplets characterized with high K (expressed by Reynolds number and Ohnesorge number) value promoted a fine breakup and small reflected droplets. The droplets of gasoline and TRF with high incident normal velocity were more likely to perform the energy transformation from normal momentum to tangential momentum.