Numerical simulation of methanol droplet combustion in carbon-dioxide enriched air

Methanol combustion in space applications within an environment enriched with radiatively participating suppressing agent such as CO₂ has been investigated. Nitrogen in the oxidizer stream (air) has been replaced by CO₂, while the oxygen mass fraction has been kept constant (0.23). Numerical results are obtained using a predictive, transient, two-phase, axisymmetric numerical model that includes surface tension effects and a radiation model based on optically thin approximation. Product species such as CO₂ and H₂O are considered as the radiating species. Results for combustion in a nearly quiescent (initial Reynolds number 0.01), CO₂ enriched atmosphere (replacing N₂ in air with CO₂ from 20% to 70%) and initial droplet diameters in the range of 0.8 mm to 1.55 mm are presented. Extinction diameter for a given initial droplet diameter increases with increasing %CO₂. Linear variation of the extinction diameter with initial diameter of the droplet becomes non-linear with increasing CO₂ in the oxidizer stream (when CO₂ is greater than approximately 20%).