Nitric oxide sensitization of hydrogen detonations

This study investigates the effect of nitric oxide (NO) sensitization on stoichiometric 2H2-O2-3.76Ar and 2H₂-O₂-3.76N₂ detonations at T0 = 294K and P0 = 20 kPa initial conditions. Experimentally, both mixtures are doped with three levels of NO seeding (0, 2000, and 13000ppm) and the effect of the NO addition is evaluated on the cell width based on soot foil measurements in a rectangular channel. Three models from the literature are validated with these new experimental cell width measurements by employing the Ng method. The following conclusions are obtained: experimentally, (i) the addition of the 2000 ppm of NO has no effect on the cell width for both Ar- and N₂-diluted mixtures; (ii) for 13000 ppm of NO, a reduction of the cell width is observed on both mixtures, near 10% and 33% for Ar-diluted and N₂-dilutedmixtures, respectively; Numerically, (iii) all the models predict the strongest effect of NO for Ar-diluted mixtures, while the opposite is observed experimentally; (iv) the cell widths are satisfactorily predicted, within a 30% error, by all the models for all Ar-diluted mixtures, while a discrepancy above a factor of two is observed for all the models with N₂ mixtures; (v) numerical investigations at a higher NO seeding level revealed that the cell width is the most sensitive parameter to evaluate the effect of NO on H₂ detonations. Based on the present experimental results, higher NO seeding than 2000 ppm seems to be achievable in future studies without modifying the detonation characteristic length scales. This optimal NO seeding level must be investigated experimentally due to the large discrepancies observed in the present validation work.