Estimation of third body efficiencies from experimental data: Application to hydrogen combustion

In this work, the role of H2O and CO2 as diluents is investigated, in operating conditions relevant to MILD combustion of hydrogen. Through virtual species analysis, the role of third body collisions emerges in phenomena such as ignition and speciation. Global sensitivity analysis shows that a single third body efficiency exhibits a larger impact than a group of sensitive reactions. For fall-off reactions, the adoption of a PLOG format, rather than a classical TROE can introduce errors as high as 2000% on macroscopic combustion targets due to the absence of key collision efficiencies. Heuristic optimization methods in OptiSMOKE++ provide best estimates and confidence regions for the third body efficiencies of H2O and CO2 in H +O2(+M)& BULL;HO2(+M) and H2O2(+M)& BULL;2OH(+M) in TROE formulation. Eventually, a method to extract this information using the PLOG formulation is proposed. This approach is applicable to other reactions in case theoretical calculations are unavailable or difficult to perform.& COPY; 2023 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.