Experimental and Numerical Study of Laminar Diffusion Flames in Microgravity Environments

Experiments on laminar jet diffusion flames were conducted aboard China’s Space Station under varying fuel flow rates and ambient oxygen concentrations (21%—30%). Measurements of flame morphology and the distributions of OH^* and CH^* was obtained. By combining these data with numerical simulations, the flame characteristics under different operating conditions were analyzed, along with and the influencing mechanisms of ambient oxygen concentration and fuel flow rate on flame morphology. The results show that as the fuel flow rate gradually increases, the flame morphology undergoes a transition from hemispherical to conical and finally cylindrical. An excessively large flame radiation fraction is the primary reason for flame opening at the tip, while an increase in ambient oxygen concentration promotes the closure of the flame tip. Compared to normal gravity, flames in microgravity exhibit lower flow velocities, which leads to higher flame radiation and lower flame temperature.