Extinction of microgravity partially premixed flame aboard the Chinese Space Station

The radiation and strain effect can be comparably influential in a partially premixed flame (PPF), especially in microgravity environments. The present study reports the first batch of combustion experiments aboard the Chinese Space Station. The experiments were conducted using a co-flow burner installed on the Gas Combustion Experiment Insert inside the Combustion Science Rack. With both in-orbit experiments and numerical simulations, transient dynamics of extinction in the non-premixed flames (NPFs) and PPFs are analyzed. Results suggested that the NPF branch in a PPF exhibits a “ring-like” structure with partially premixed hooks at its edges prior to global extinction. The extinction is associated with strain rate and radiation effect as analyzed by numerical simulation and comparison with the experimental results. The overall NPF branch exhibits a reduced range of equivalence ratios with two edges retracting in a premixed manner under the considerable influence of radiative heat loss. The contribution of strain and radiation effect for the local extinction is demonstrated through normalized flame stretch rate, radiative heat loss, and local Damköhler number. Results suggested that radiative heat loss for the edges of NPF region can occupy 40 % of the local heat release. A diminishing influence of the strain rate effect on flame propagation leads to a shift towards radiation-controlled extinction. The local radiative extinction at the end of the NPF region ultimately triggering the extinction of the entire NPF region.