Spontaneous and triggered longitudinal combustion instability is simulated numerically in a single-injector liquid rocket engine using a recently developed axisymmetric compressible flow solver. Turbulence is treated using a Delayed Detached Eddy Simulation (DDES) model while chemical reactions are modeled using a Compressible Flamelet Progress Variable (CFPV) method. The baseline case is an unstable case which exhibits spontaneous instability and simulates well the experimental evidence. Heat loss is then introduced by imposing isothermal boundary condition on the chamber wall. Various temperature values are used, with spontaneous longitudinal-mode instability still occurring at the higher-wall temperature. Stable but inefficient combustion occurs for the lowest wall temperature. Stabilization is also achieved by shortening the chamber length. Subsequently, triggered instability of the chamber by perturbing the propellant mass flow rates for all stabilized cases. Unsteady oscillation can be triggered to higher-amplitude limit cycles. Geometric modification proves to be a more effective stabilization method.
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