Solid-Fuel Ramjet Regulation by Means of an Air-Division Valve

Abstract

An in-e ight regulation technique, which can provide an optimal operation of a solid-fuel ramjet (SFRJ) motor over a wide e ight envelope, has been analyzed. Regulation capability is essential for an efe cient use of the SFRJ propulsionforapplicationsinvolvingvariablee ightandoperatingconditions.Themethodisbasedonacontrollable air-division valve, which drivespart of the inlet airinto thesolid-fuel port, whiletherest of the aire ow ischanneled through a bypass to the aft-mixing section of the combustor. The model takes into account parameters ine uencing the burning rate of the solid fuel (e.g., port-e ow rate, port diameter ) and formulates a general regulation law in terms of the instantaneous opening state of the division valve fora constant fuel-to-air ratio operation. The control lawwascheckedforcertaincases,considering typicaltrajectories.Ithasdemonstrated agoodregulationcapability over a broad operational range (between sea level and 15-km altitude ). Nomenclature A = area d = diameter f = fuel-to-air ratio f (h) = function of altitude in the regulation law, Eq. (22) G = air mass e ux g(M) = function of Mach number in the regulation law, Eq. (23) H = inlet step height h = heat-transfer coefe cient; altitude L = fuel grain length M = Mach number m = temperature exponent C m = mass-e ow rate n = mass-e ow rate or mass e ux exponent C