Combustion of CO/H2 mixtures at elevated pressures

The high pressure oxidation of dilute CO mixtures doped with 150-200 ppm of H-2 has been studied behind reflected shock waves in the UIC high pressure single pulse shock tube. The experiments were performed over the temperature range from 1000 to 1500 K and pressures spanning 21-500 bars for stoichiometric (Phi = 1) and fuel lean (Phi = 0.5) oxidation. Stable species sampled from the shock tube were analyzed by standard GC, GC/MS techniques. The experimental data obtained in this work were simulated using a detailed model for H-2/CO combustion that was validated against a variety of experimental observables/targets that span a wide range of conditions. These simulations have shown that within experimental error the model is able to capture the experimental trends for the lower pressure data sets (average nominal pressures of 24 and 43 bars). However the model under predicts the CO and O-2 decay and subsequent CO2 formation for the higher pressure data sets (average nominal pressures of 256 and 450 bars). The current elevated pressure data sets span a previously unmapped regime and have served to probe HO2 radical reactions which appear to be among the most sensitive reactions in the model under these conditions. With updated rate parameters for a key HO2 radical reaction OH + HO2 = HO + O-2, the model is able to reconcile the elevated pressure data sets thereby extending its capability to an extreme range of conditions. (C) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.