Experimental Study of Diesel-Fuel Droplet Impact on a Similarly Sized Polished Spherical Heated Solid Particle

The head-to-head impact of diesel-fuel droplets on a polished spherical brass target has been investigated experimentally. High-speed imaging was employed to visualize the impact process for wall surface temperatures and Weber and Reynolds numbers in the ranges of 140-340 °C, 30-850, and 210-1135, respectively. The thermohydrodynamic outcome regimes occurring for the aforementioned ranges of parameters were mapped on a We-T diagram. Seven clearly distinguishable postimpact outcome regimes were identified, which are conventionally called the coating, splash, rebound, breakup-rebound, splash-breakup-coating, breakup-coating, and splash-breakup-rebound regimes. In addition, the effects of the Weber number and surface temperature on the wettability dynamics were examined; the temporal variations of the dynamic contact angle, dimensionless spreading diameter, and liquid film thickness forming on the solid particle were measured and are reported.