Numerical simulations of a model scramjet combustor are presented. The simulations use a hybrid Reynolds-averaged Navier-Stokes and Large-eddy simulation turbulence model in order to resolve the large-scale turbulent structure of the injection flowfield. A low- dissipation flux evaluation scheme and a Crank-Nicolson type time integration scheme ensure that a large range of length scales are resolved in the simulation. Simulations are presented for a non-reacting mixing case, and a case in which combustion occurs. Finite- rate chemistry is coupled with the flow solver for the simulation of the combusting case. Measurements of N2 mole fraction and temperature are used to validate the predictions of the simulation in the mixing case. The simulation results are found to be in good agreement with the experimental measurements. The results from the mixing case are then used to investigate the mixing characteristics and turbulence field inside of the model combustor. The flow is found to self-ignite in the simulation of the reacting case. However, comparisons to mole fraction and temperature measurements indicate lower levels of combustion occur in the simulation than in the experiment. The pressure rise due to combustion is significantly lower in the simulation than measured in the experiment.