The evaporation of droplets is one of the major stages of the working process that defines the combustion efficiency in the propulsion and power generation systems. Droplets of different sizes moving relative to gas flow and distributed in a complicated manner evaporate in the medium with variable gas dynamic and thermodynamic parameters. The evaporation process is very complicated, which is why whatever actual problem reduces in its theoretical analyses to an approximate model, allowing one to obtain an analytical or numerical solution. For instance, the chemical nonequilibrium model of evaporation of a single-component droplet in high-temperature flow illuminated in Chapter 5 comprises dozens of assumptions. A large number of theoretical and experimental studies are dedicated to the problems of droplets evaporation and combustion.