The Effect of the Vibrational Excitation of Molecules on the Shock-Induced Combustion in a Syngas-Air Mixture

Abstract

Mechanisms of combustion intensification in a syngas-air mixture supersonic flow behind the oblique shock wave front are investigated when the vibrations of reactant molecules are pre-excited. The simulation shows that the excitation of H₂, N₂, and CO molecules in front of the shock wave is much more effective to shorten the induction zone than mere heating the mixture. The energy efficiencies of both methods of combustion initiation are compared. It is shown that in order to ensure the identical ignition delay length it is needed to put noticeably greater specific energy in the case of heating the gas than that upon the excitation the molecule vibrations. In addition, low-temperature ignition of the mixture with vibrationally pre-excited H₂, N₂, and CO molecules makes it possible to raise the efficiency of conversion of the reactant chemical energy to the thermal energy released during combustion compared with the method of heating the mixture.

Keywords:

• Chain-branching reactions
• Excited molecules
• Ignition enhancement
• Shock-induced combustion
• Syngas
• Thermal nonequilibrium

ACKNOWLEDGMENTS

This work was supported by Russian Foundation for Basic Research (grants 08-01-00808 and 08-08-00839) and the Federal Purpose Program “Scientific and science-educational manpower of innovational Russia” (state contract No 2.740.11.0074).

Notes

Note. ^a All other species have efficiencies equal to unity. ^b The fall-off behavior of this reaction is expressed in the form as used by Baulch et al. (2005).