Erratum for "Analytical Model for the Impulse of Single-Cycle Pulse Detonation Tube"

I N the original evaluation of our analytical model for the singlecycle impulse of a pulse detonation tube,1 we approximated the detonation product isentrope as having a frozen composition with a corresponding polytropic exponent γ f . As discussed in the accompanying comment by Radulescu and Hanson and our response,2 for many situations, it is more appropriate to use an equilibrium approximation to the isentrope. This implies a different value of the polytropic exponent γ = γe and a new computational procedure for computing the plateau pressure P3 and results in revised values for the predicted impulse. Although the general equations and the qualitative conclusions drawn in our paper are unchanged, the revised numerical values of the predicted impulse differ up to 9.5% for stoichiometric fuel– oxygen mixtures and less than 1.3% for fuel–air mixtures at standard conditions. In this Errata, we present a revised set of data along with a short description of the calculations. The choice of the isentropic exponent, issues associated with chemical equilibrium, and the relevance to impulse calculations are discussed in the associated comment by Radulescu and Hanson and in our response to them. The input parameters of our impulse model consist of the external pressure P0, the detonation velocity UCJ, the equilibrium speed of sound behind the detonation front c2, the Chapman–Jouguet (CJ) pressure P2, and an approximation to the equilibrium polytropic exponent γe for the adiabatic expansion of the detonation products. All parameters were computed using numerical equilibrium calculations3 performed with a realistic set of combustion products. Instead of the analytic computation used in our original paper, our revised properties at state 3 (behind the Taylor wave) are now calculated by numerically integrating the Riemann invariant along the equilibrium isentrope until the plateau region of no flow is reached, ∫ P2