Time-Temperature Simulation in Low-Pressure Ignition of Hypergolic Liquids

T work is concerned with the ignition of hypergolic liquids at various pressures, and attempts to simulate timetemperature relationships in a droplet before it bursts into flame. It is known ~ that the ignitibility of a propellant can be affected drastically by changes in pressure, as well as temperature and the geometry of the enclosure surrounding the impinging streams of reactants. But the reasons for this sensitivity are not clear, nor is it known whether liquid particles that differ in size also differ in ignition behavior. At atmospheric pressure, two liquids that comprise a hypergolic mixture burst into flame almost as soon as they meet. At lower pressure there is longer delay before ignition occurs. Then, below some pressure, ignition does not occur, even though slightly above this point the hypergolic mixture does ignite after a reasonable delay time. The pressure at which cut-off occurs, marking the boundary between ignition and nonignition, is not well defined and reproducibility becomes increasingly more difficult as the pressure is reduced.