The dissociative cooling concept, part one: the effect on heat transfer of gas mixture injection into air at the axisymmetric stagnation point

摘要

By embedding a dissociating material into the porous outer structure of a projectile, stagnation point heat transfer may be reduced by transpiration cooling resulting from the outflow of the dissociated gas products. The principal material considered is ammonium chloride, NH_4Cl, which dissociates at temperatures over 615K thus absorbing enthalpy, hence providing additional heat transfer reduction. Stagnation point heat transfer solutions for the injection of the dissociation products of NH_4Cl, into both equilbrium and frozen boundary layers are presented and compared to those for the injection of other gases such as helium. Results show that dissociative cooling has the potential to provide a significant reduction in stagnation point heat transfer as temperatures rise because the gas injection rate increases with the temperature of the NH_4Cl interface.