Assessing the Impacts of Viscosity and Radiative Transfer in Internal Detonation Scenarios Involving Hydrogen-Air Mixtures
Predictions from a hydro code are compared against those obtained from a computational fluid dynamics (CFD) framework to numerically assess the effects of: viscous and radiative losses associated with a propagating pressure wave, the point source ignition approximation, and their subsequent impact on the over-pressure characteristics during internal detonation scenarios involving hydrogen-air mixtures. The hydro code employed: TNT equivalencies to represent the heat of hydrogen combustion and solved the inviscid (Euler) equations in conjunction with the JWL equation of state for momentum transport. The CFD simulations resolved the detonation wave employing: the SRK equation of state, Large Eddy Simulations and employed spectrally-averaged mean absorption coefficients for the radiative properties. Detonation wave propagation in air (non-reacting) as well as in premixed hydrogen-air mixtures (reacting) were studied employing a 21-step detailed chemistry mechanism. The adequacy of our modeling procedure was first established by obtaining reasonable agreement between our predictions from the two modeling frameworks with reported measurements from a small- scale explosion study. The same CFD modeling methodology was subsequently extended to larger scales. The heats of reaction resulted in acceleration and strengthening of the wave front in both lean and rich hydrogen-air mixtures investigated in this study, with trends agreeing with predictions from flame speed theory. However, viscous losses resulted in a noticeable weakening of the detonation wave during its propagation. Including the effects of radiative transfer had no impact on the wave propagation due to the relative magnitudes of the radiative source and chemical heat release terms.
