Simplified Theory for Ignition Times of Hypergolic Gelled Propellants

A simplified theory for ignition times of hypergolic gelled propellants was investigated. Two adjacent half-spaces were considered, one occupied by fuel and the other by oxidizer. The constant thermal conductivity, heat capacity, and density of each may differ, so that the thermal diffusivities ωF and ωO, where the subscripts F and O identify fuel and oxidizer, respectively, need not be the same. Arrhenius reaction at the interface with overall activation energy E and constant prefactor Q was presumed, with energy released per unit area per unit time. This can be related to the product of the heat of combustion per unit mass of reactants consumed and the mass rate of consumption of reactants per unit volume by multiplying by a characteristic thickness of the interface. A simple ignition-time formula is achieved, involving a universal constant, the value of which is approximately 1.5. The formula is useful for correlating data then estimating ignition times, and might help in investigating transient ignition pressure peaks.