An analytical model for the impulse

An analytical model for the impulse of a single-cycle pulse detonation tube has been developed and validated against experimental data. The model is based on the pressure history at the thrust surface of the detonation tube. The pressure history is modeled by a constant pressure portion followed by a decay due to gas expansion out of the tube. The duration and amplitude of the constant pressure portion is determined by analyzing the gas dynamics of the self-similar °ow behind a steadily-moving detonation wave within the tube. The gas expansion process is modeled using dimensional analysis and empirical observations. The model predictions are validated against direct experimental measurements in terms of impulse per unit volume, speci¯c impulse, and thrust. Comparisons are given with estimates of the speci¯c impulse based on numerical simulations. Impulse per unit volume and speci¯c impulse calculations are carried out for a wide range of fuel-oxygen-nitrogen mixtures (including aviation fuels) varying initial pressure, equivalence ratio, and nitrogen dilution. The e®ect of the initial temperature is also investigated. The trends observed are explained using a simple scaling analysis showing the dependency of the impulse on initial conditions and energy release in the mixture