Two phase flow combustion modelling of a ducted rocket

Under a co-operative program, the Defence Research Establishment Valcartier and Université Laval in Canada and the TNO Prins Maurits Laboratory in the Netherlands have studied the use of a ducted rocket for missile propulsion. Hot-flow direct-connect combustion experiments using both simulated and solid fuels have been carried out on a wide range of configurations to identify the geometries and flow rates necessary for good combustor performance. The experiments using a simulated ducted rocket fuel, a reacted mixture of ethylene and air, have all been modelled using reacting flow Computational Fluid Dynamics (CFD) with the goal of being able to analyze and predict combustor performance. The combustion was modelled with onestream and twostream PDF (Probability Density Function) models. With the onestream model, all of the fuel components, both gaseous and solid carbon, were injected together and were assumed to react instantaneously in the presence of the oxidizer. Because of this, the onestream model overpredicted the combustion efficiency with respect to the experimental results for most of the combustor configurations examined. With the twostream model, however, the fuel stream was separated into gaseous and solid carbon components, with the carbon injected as a series of 75 nm particles. These particles decompose gradually into carbon monoxide gas, based on a model using both the kinetics of the surface reactions and the diffusion of oxygen to the surface of the particles. For the majority of the configurations, better predictions of combustion efficiency were obtained with the twostream approach when compared to the experimental results than for the onestream PDF model. © 2001 by the Department of National Defence, Canada and TNO Prins Maurits Laboratory, the Netherlands.