Molecular level simulations of hydrogen-air reacting flows under thermal and chemical non-equilibrium*

Molecular level simulations of hydrogen-air detonation waves are performed using the Direct Simulation Monte Carlo (DSMC) method [1]. The conditions presented are relevant to those in Rotating Detonation Engines or Scramjets [2]. One-dimensional (1-D) detonation waves simulated under near-equilibrium conditions have been shown to agree well with the equilibrium solution with only slight variations when using the standard equilibrium TCE model in DSMC code SPARTA [3]. The equilibrium results were obtained with the Zel'dovich-von Neumann-Döring (ZND) solution obtained from the Shock and Detonation (SDT) toolbox [4]. In this paper, an effective temperature (T_eff) formulation is explored which can account for ro-vibrational non-equilibrium. The use of T_eff within the TCE model results in a good agreement of state-specific reaction rates from a 0-D isothermal bath with those obtained from the Quasi-Classical Trajectory (QCT) calculations. A 1-D detonation case is simulated with preheated reactants at 900 K and 0.3 atm pressure and Mach number M = 3.0. The results from the effective temperature model are compared against the equilibrium DSMC result and the differences between the two are highlighted. Simulationd of 2-D detonations waves are currently in progress. 

[1] G. A. Bird, “Molecular gas dynamics and the direct simulation of gas flows” (1994).

[2] R. Fievet et al., Proceedings of the Combustion Institute 36 (2017) 2901-2910

[3] S. J. Plimpton, M. A. Gallis, Sparta, http://sparta.sandia.gov.

[4] J. Lawson, J. Shepherd, https://shepherd.caltech.edu/EDL/PublicResources/sdt (2021).