Theoretical consideration of combustion effects on base pressure in supersonic flight

Abstract

A theoretical treatment is given for the behavior of base pressure on a two-dimensional body in supersonic flight when the inviscid stream adjacent to the turbulent reattachment zone is subjected to combustion effects. The analysis, which rests upon a simplified treatment of the combustion zone and the Crocco-Lees mixing theory for the reattachment region is intended to give an upper-limit estimate of thrust levels attainable on the base. Previous experimental work in this area is reviewed and is shown to suffer in performance because of experiment design; the maximum performance levels could not be expected and further work in this area is indicated. Analytically, it is shown that, despite the apperance of many base flow and combustion parameters, the specific impulse is primarily a function of only the air-fuel ratio, combustion length-body base height ratio, and the free stream Mach number. The major influence of combustion on the reattaching flow is shown to be the introduction of a new characteristics length, the combustion length, and the action of this scale in constraining the reattachment length.