Numerical investigation of aerodynamic droplet breakup in a high temperature gas environment

• Drop breakup for various We and Re numbers at isothermal as well as evaporating conditions.
• VOF model coupled with a local evaporation model and adaptive grid refinement.
• Quantification of the effect of heating and evaporation on droplet breakup.
• Breakup is affected by heating mainly at low We numbers.
• An enhanced 0-D model is proposed to predict droplet heating and evaporation of deformed droplets.

The Navier–Stokes equations, energy and vapor transport equations coupled with the VOF methodology and a vaporization rate model are numerically solved to predict aerodynamic droplet breakup in a high temperature gas environment. The numerical model accounts for variable properties and uses an adaptive local grid refinement technique on the gas–liquid interface to enhance the accuracy of the computations. The parameters examined include Weber (We) numbers in the range 15–90 and gas phase temperatures in the range 400–1000 K for a volatile n-heptane droplet. Initially isothermal flow conditions are examined in order to assess the effect of Weber (We) and Reynolds (Re) number. The latter was altered by varying the gas phase properties in the aforementioned temperature range. It is verified that the We number is the controlling parameter, while the Re number affects the droplet breakup at low We number conditions. The inclusion of droplet heating and evaporation mechanisms has revealed that heating effects have generally a small impact on the phenomenon due to its short duration except for low We number cases. Droplet deformation enhances heat transfer and droplet evaporation. An improved 0-D model is proposed, able to predict the droplet heating and vaporization of highly deformed droplets.