The article is devoted to estimating the intensifying efficiency of methane-air ignition by adding a small amount of hydrogen and/or ethylene. It presents features of the experimental determination of the ignition delay period for fuel-air mixtures using shock installation and methods of processing empirical data. The testing of the known ignition kinetic models for methane, hydrogen, and ethylene with air was carried out. The results of test calculations were compared with those previously published, as well as original experiments. The kinetic model was chosen to provide the minimum discrepancy between the calculated and experimental data. The regularities of the effect of hydrogen and ethylene additives on the ignition dynamics of the methane-air mixture for the range of initial pressures from 1 to 8 bar at temperatures from 900 to 1100 K were obtained with the use of non-stationary numerical modeling. Methane-air mixtures with the mass fraction of additives not exceeding 10% were studied. The quantitative indicators of possible reduction in the ignition delay period of methane-air mixtures were detected.
The effect of a small addition of Xe on the conditions for the occurrence of detonation in an incident shock wave (SW) with a change in its intensity is studied. The experiments are carried out in a shock tube (ST) with mixtures (75 -q)% H 2 + 25% air + q% Xe, where q = 0, 0.25, and 0.5. The addition of Xe leads to a shift in the detonation threshold to the region where the conditions are more unfavorable for its occurrence. Moreover, decreasing x from 0.5 to 0.25 causes a stronger shift in the detonation threshold; i.e., dependence x became nonmonotonic. This effect is due to a strong increase in the frequency of high-energy collisions of O 2 and Xe in the front compared to the equilibrium behind the wave and the subsequent significant acceleration of the chemical interaction of O 2 and H 2 behind the front. It is a consequence of the occurrence of a specific translational nonequilibrium in the wave front. This is indicated by the results of similar studies of the effect of replacing a small amount with an inappropriate amount of Xe on the conditions for the onset of detonation for mixtures of 10% H 2 + 5% O 2 + 85% He. In addition, the results of the performed numerical simulation with mixtures (75 -q)% H 2 + 25% air + q% Xe (q = 0.25, 0.5), taking into account the rotational relaxation of О 2 and N 2 for conditions close to the conditions of the aforementioned experiments, showed the possibility of a nonmonotonic shift of the detonation threshold.
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