Dynamic processes occurring during the spreading of thin liquid films produced by drop impact on hot walls

A Comprehensive Model for Liquid Film Boiling in Internal Combustion Engines

“…They showed that the Leidenfrost regime is less and less important as the gas pressure increases. Furthermore, the experimental visualizations of Chaves et al [2] and Moita and Moreira [7] show a cloud of droplets above the wall, which levitates under the effect of the Stefan flow induced by the evaporation. Therefore, in this boiling regime, the wall heats the vapor cushion which in its turn heats the liquid.…”

“…This interaction of spray with the wall involves different physical phenomena according to the conditions of impact (speed of the droplets, temperature of the wall, roughness of the surface, etc.) and of the pressure of gases in the combustion chamber [1][2][3][4][5][6][7].…”

Thermally induced secondary drop atomisation by single drop impact onto heated surfaces

“…It is important to underline that the impact of a liquid drop onto a solid surface heated at temperatures higher than the saturation temperature yields outcomes with characteristics completely different from those observed for cold surfaces. When the surface temperature is larger than the liquid saturation temperature the secondary atomisation is not generated through the so called ''crown splash'' or the other possible outcomes for impact onto cold surfaces (see for example Marengo et al, 2001), but from the vapour bubble formation and break-up at the liquid-air interface of the spreading lamella, and from the break-up of the lamella itself which, under proper conditions, may eventually levitate due to the formation of a vapour cushion on the surface (many interesting details of the first impact phase can be found in Chaves et al, 1999). The impact velocity and the surface temperature (see among others Chandra and Avedisian, 1991), the impact angle (Yao and Cai, 1988;Ko and Chung, 1996;Kang and Lee, 2000), the surface tension and viscosity of the liquid, the surface wettability, effusivity and roughness are among the main parameters influencing the process.…”

The dynamics of Leidenfrost drops

“…We found that the occurrence of spray from side-view observation strongly correlates with the presence of wetted areas with entrapped bubbles on the solid surface, as observed by FTIR. Since the surface to cools down as a result of the presence of the drop, the wetted areas with their entrapped bubbles can survive on the surface, resulting in the spray formation by the bursting of the bubbles at the top surface of the drop, in agreement with previous studies on spray formation [66,97]. Furthermore, we find the boundary between contact boiling and transition boiling to be weakly dependent on the impact velocity, similarly as reported for ethanol drops impacting on glass [57] and on sapphire [45,69].…”