Thermomechanics of laser-induced shock waves in combustible mixtures

In this study, a combined experimental and numerical approach is taken to further investigate the thermomechanics of shock wave formation in combustible mixtures. This study focuses on several gas mixtures including air, methane/N ₂, methane/air, and biogas/air. The lean and stoichiometric combustible mixtures are studied at three different laser energy levels. The Jones blast wave theory is used to calculate the energy involved in development of the resulting shock waves and used to specify the initial conditions for the plasma in simulations. In addition, interferometry is used to gain insights into the thermodynamic conditions within the plasma kernel, for validation of the numerical model results. The energies calculated for the different mixtures studied show that shock waves generated in the combustible mixture likely gain energy early in the breakdown process from exothermic chemical reactions. Shock wave results from experiment are shown to be replicated by the model, and the variations of the density inside of the hot core region are in agreement between the simulation and experimental results.