Direct prediction of liquid rocket combustion instabilities with emphasis placed on velocity- and pressure-coupled responses

Aiming at a direct and quantitative prediction of unstable waves evolving in the liquid rocket combustor, a theoretical-numerical analysis is conducted. Instability equations in terms of perturbed flow variables are space-averaged to provide the timeintegrated ODE's in terms of modal amplification factors for pressure- and velocity-coupled unstable waves. Acoustics and combustion responses are fully coupled in the formulation and numerically solved in implicit manner. Effects of magnitude of perturbation, droplet lifetime, combustion region, and pressure-, velocity-coupled responses on the instabilities are discussed.