Design of supersonic combustors based on pressure-area fields

A family of one-dimensional heat addition processes having a pressure-area relationship pAele-1=constant is studied. Equations are develeped for real and ideal gases and simplified relationships are obtained for the latter including the determination of the value of ∈ for the most efficient process and for the conditions at the entropy limit. The important combustor variables are found for a particular supersonic combustion ramjet operating on a selected trajectory, and the effect of combustor optimization on engine specific impulse is given. This analysis is used to evaluate the results of a hydrogen air combustion experiment made in a 1.58° half-angle conical combustor 24 in. in length at an inlet Mach number of 1.95. It is concluded that to increase the combustion efficiency from the experimentally observed 71% to 100% and at the same time sustain the minimum entropy rise, a contoured combustor having approximately 4.5 in. of additional length coupled with an 11% reduction in exit radius would be required.