Evaluation of combustion mechanisms using global uncertainty and sensitivity analyses: A case study for low-temperature dimethyl ether oxidation

A global uncertainty analysis is performed for three current mechanisms describing the low-temperature oxidation of dimethyl ether (Aramco Mech 1.3, Metcalfe et al., Int J Chem Kinet 2013, 45, 638-675; Zheng et al., Proc Combust Inst 2005, 30, 1101-1109; Liu et al., Combust Flame 2013, 160, 2654-2668) with application to simulations of species concentrations (CH2O, H2 O2 ,CH3 OCHO) corresponding to existing data from an atmospheric pressure flow reactor and high-pressure ignition delays. When incorporating uncertainties in reaction rates within a global sampling approach, the distributions of predicted targets can span several orders of magnitude. The experimental profiles, however, fall within the predictive uncertainty limits. A variance-based sensitivity analysis is then undertaken using high dimensional model representations. The main contributions to predictive uncertainties come from the CH3 OCH2 + O2 system, with isomerization, propagation, chain-branching, secondary OH formation, and peroxy-peroxy reactions all playing a role. The response surface describing the relationship between sampled reaction rates and predicted outputs is complex in all cases. Higher order interactions between parameters contribute significantly to output variance, and no single reaction channel dominates for any of the conditions studied. Sensitivity scatter plot