Comparison of Performance and Stability Analyses for LOX/CH4 Rocket Engines

Abstract

Liquid rocket engine development using oxygen and methane propellants is currently underway at CIRA within the context of the Hyprob program funded by the Italian Ministry of University and Research (MIUR). Different methods for evaluating the performance and combustion stability of oxygen and methane propellants are being analyzed. This study details performance and stability analyses of the NASA sponsored Penn State LOX/CH 4 Uni-element rocket as well as those for a similar rocket engine under development at CIRA. Simulations are conducted with two one-dimensional liquid rocket combustion analysis programs, The Rocket Combustor Interactive Design and Analysis code program and the Generalized Instability Model, the latter of which uses an analytical model to study combustion instabilities by solving an inhomogeneous pressure wave equation using a modified Galerkin method. Nomenclature GIM = Generalized Instability Model ROCCID = Rocket Combustor Interactive Design and Analysis Code LOX = Liquid Oxygen SSBB = Sub Scale Bread Board dV = differential volume E′ = energy sources m E = Rupe Mixing Efficiency 2 n E = integral of square of normal modes f = frequency n F = source terms in temporal ODE GR = growth rate M ′ = momentum sources MR = mixture ratio LEE = Linearised Euler Solver L 1 = first longitudinal mode L 2 = second longitudinal mode L 3 = third longitudinal mode C 1 = first coupled mode C 2 = second coupled mode C 3 = third coupled mode a = sonic velocity w f = inhomogenous term of wall boundary condition h = step height HRL , 0 x = heat release location Downloaded by UNIVERSITY OF TENNESSEE on August 13, 2015 | http://arc.aiaa.org | 2 k = wave number K = complex wave number L = length of combustor section l = mode number m = mass n = normal vector u = velocity p = pressure q = heat release t = time x = axial coordinate Y = admittance Z = impedance β = amplitude parameter in velocity lag heat response model w δ = frequency shift γ = ratio of specific heats ε = error η = temporal modes Ω = perturbed frequency ρ = density τ = time lag, sensitive time lag T τ = total time lag i τ = insensitive time lag ψ = spatial, acoustic or normal modes ω = angular frequency Superscripts ' = perturbation variable -= average . = first temporal derivative .. = second temporal derivative Subscripts c = chamber j = injector b = burning n = mode number bdry = boundary term _ nl = non linear term _ mf = mean flow term OX = oxidizerF = fuel Downloaded by UNIVERSITY OF TENNESSEE on August 13, 2015 | http://arc.aiaa.org |