Low-Temperature Flameless Combustion of a Large Drop of n-Dodecane under Microgravity Conditions

The forced ignition, combustion, and spontaneous ignition of a drop of n-dodecane in an atmosphere of air at a normal pressure under microgravity conditions were studied based on a physicomathematical model of drop combustion and a detailed kinetic mechanism of the oxidation and combustion of n-dodecane C12H26. The selection of n-dodecane was related to the Russian–American experiment CFI (Cool Flame Investigation) Zarevo performed in 2017 aboard the International Space Station with the use of the large drops of this hydrocarbon. The analysis carried out deepens our knowledge about the flameless combustion of a large drop under the conditions of microgravity. The calculations showed that, after the radiation extinction of a hot flame, the drop can continue to evaporate because of the exothermic low-temperature oxidation of fuel vapor with repeated blue flame flashes at a characteristic temperature of 980–1000 K. A detailed analysis of the calculation results showed that the regular splashes of temperature resulted from the thermal decomposition of hydrogen peroxide—branching with the release of hydroxyl radicals.