Microgravity experiments on flame spread of an N-decane droplet array in a high-pressure environment

The flame-spread phenomena of a n-decane droplet array in the supercritical pressure range were studied in microgravity. Experiments were performed at ≤ 5 MPa, which is over the critical pressure of n-decane. In microgravity, the flame-spread rate decreased with increasing pressure, had a minimum at a pressure around half of the critical pressure, and then increased again. It had a maximum at the pressure near the critical pressure and then decreased gradually with pressure. In normal gravity, the flame-spread rate monotonously decreased and there was a pressure limit beyond which the flame spread did not occur. Around the critical pressure, a jet-like flow of fuel vapor from an unburned droplet heated by the flame of a burning droplet was observed. The internal flow rate increased with pressure and had a maximum near the critical pressure. The mechanism responsible for the maximum flame spread rate near the critical pressure was the enhanced heat and mass transfer caused by the fuel-vapor jet and flame propagation along that jet. Original is an abstract.