The thermal decomposition of nitrous oxide and its reaction with hydrogen, carbon monoxide and methane.

摘要

Nitrous oxide kinetics strongly influence practical combustion processes yet remain uncertain. Existing studies are plagued with experimental artifacts and base conclusions on insufficiently defined data sets, leaving mechanism development subject to multiple interpretations. This dissertation presents new data collected at temperatures and pressures of 950-1173 K and 1.5-15 atmospheres, where the greatest uncertainties remain. Data from dilute ({dollar}sim{dollar}1%) reacting mixtures of nitrous oxide in nitrogen and mixtures of nitrous oxide in nitrogen with H{dollar}sb2,{dollar} CO and CH{dollar}sb4{dollar} are discussed. The experiments were conducted in a well-characterized variable pressure flow reactor which closely simulates a zero-dimensional, adiabatic, homogeneous, gas-phase chemical kinetic process. As many of the stable species as possible were quantified in order to highly constrain the hierarchical development of a detailed chemical mechanism. Both reaction flux and gradient sensitivity analyses were used to determine key elementary reaction path processes and rates.; Using data from the N{dollar}sb2{dollar}O decomposition experiments collected here in conjunction with re-analyzed literature data, the following rate constant expression for the uni-molecular reaction, {dollar}rm Nsb2O(+M)to Nsb2+O(+M),{dollar} is developed: {dollar}rm ksb{lcub}0,Nsb2{rcub} = 9.13times 10sp{lcub}14{rcub}{dollar} exp(-57,690/RT) cm{dollar}rmsp3 molsp{lcub}-1{rcub} secsp{lcub}-1{rcub}{dollar} and {dollar}rm ksbinfty = 7.91 times 10sp{lcub}10{rcub}{dollar} exp(-56020/RT) sec{dollar}sp{lcub}-1{rcub}.{dollar} Simple Lindemann fits utilizing these parameters reproduce the pressure dependent rate constants measured here within {dollar}pm{lcub}25{rcub}%.{dollar} These results strongly depend on the choice of rate constants for the {dollar}rm Nsb2O+OHLeftrightarrow HOsb2+Nsb2, Nsb2O+OLeftrightarrow Nsb2+Osb2{dollar} and {dollar}rm Nsb2O+OLeftrightarrow NO+NO{dollar} reactions.; Numerical modeling of hydrogen/nitrous oxide data collected at these conditions indicate that reactions involving {dollar}rm Nsb2Hsb{lcub}x{rcub}{dollar} and NH{dollar}sb{lcub}rm x{rcub}{dollar} species are necessary to predict the measured species evolution profiles. Parametric experiments conducted with quantities of NO added to the initial mixture provide an estimate for the rate constant of NO + H + M = HNO + M with a nitrogen collision partner.; The catalytic effect of water vapor on CO/N{dollar}sb2{dollar}O/N{dollar}sb2{dollar} mixtures is measured, and a quantitative treatment of its influence is now possible. The highly contested direct reaction of carbon monoxide with nitrous oxide was found to be insignificant in this study. The results also show that characterization of the fall-off behavior of the CO + O +M = CO{dollar}sb2{dollar} + M reaction is necessary at these conditions.; The above results are necessary to accurately model methane/nitrous oxide kinetics at similar conditions. These data are also presented.