Towards predictive simplified chemical kinetics for hydrogen detonations.

A methodology to develop predictive simplified kinetics schemes (one-step/three-step chain-branching) is presented in which detonation velocity-curvature (D − κ) curves computed with detailed thermochemistry are used as the fitting target aiming to capture the turning point of the curve (κ crit). This was motivated by the similar trend observed between the κ crit values obtained using the simplified schemes of Taileb et al. (2020), fitted using conventional methods, and the critical reactive layer heights for detonation propagation under yielding confinement (h crit) reported by the same authors. Both updated schemes satisfactorily reproduce the target D − κ curves and are used to (re)compute multidimensional cellular detonations propagating in channels and confined by inert layers. Simulations show a much better agreement with the results obtained with detailed kinetics for the detonation flow fields, cell sizes distributions, and h crit. Moreover, it is observed that the average curvatures of the computed fronts are in line with those predicted by the D − κ formulation, providing supporting evidence of the applicability of reduced order models for fast and inexpensive estimates of detonation limiting behaviors in safety studies. Novelty and Significance Statement The novelty of this research lies in proposing and testing an alternative methodology to determine the kinetics parameters of simplified kinetics schemes (1 − step and 3 − step) so that these retain the predictive capabilities of detailed kinetics. This is achieved by using detonation velocity-curvature curves (D − κ) as a fitting target. Conventional fitting procedures, such as targeting ignition delay times and/or matching ZND profiles have been shown to perform poorly in previous research. The new methodology shows significant improvements in the prediction of dynamic detonation parameters in ideal detonations such as cell sizes distributions, as well as in the prediction of the critical reactive layer heights for detonation propagation under yielding confinement (h crit); a canonical configuration of interest to propulsion and industrial safety. For the latter, the new methodology yields h crit for H 2 -O 2 detonations of h crit = 12 mm instead of 24 mm (with conventional methods), and h crit = 8 mm instead of 20 mm , for the 1-step and 3-step models, respectively. The D κ results are much closer to those obtained with detailed kinetics ( h crit = 6 mm) and to the experimental measurements ( h crit = 4. 6 mm). The methodology is generic to be applied to any mixture of interest. [ABSTRACT FROM AUTHOR]