Ablation studies of low melting point bodies in a pre-heated supersonic air stream

摘要

This report is an investigation into the melting of axi-symmetricand two-dimensional bogies at a Mach No. of M[infinity] = 1.78 and stagnationtemperatures up to 550 [degrees]K. In this temperature range, the most suitablematerial for the models was found to be an eutectic tin-lead alloya melting point of 456 [degrees]K.For the cone and hemisphere-cone models two distinct modes of meltingwere observed. In cases where the estimated equilibrium surface temperature(Tw)o was approximately equal to the material melting temperature Tm,melting occurred only at the stagnation point of the model and was suchthat a flat surface normal to the gas stream always resulted. If theaverage rate of heat transfer at the air-liquid interface be defined asqi = LmPm x, where Lm is the latent heat of fusion, Pm is the density ofthe material and x is the rate of recession of the flat surface, it isfound that qi decreases with increase of the radius of the flat nose. Avery approximate theory is found to show some agreement with the experimentalrates of heat transfer. When (Tw)o was considerably greater than Tm the flat surface was no longer preserved and the resulting steady ablatingshape was paraboloidal in nature. When this occurred x was usuallyconstant. This allowed some average steady state heat transfer rates tobe evaluated and compared with theory.Preliminary tests were also made with a two-dimensional wedge model.