Combustion of fuel-lean mixtures in adiabatic, well-stirred reactors

Abstract

The use of a well-insulated, well-stirred reaction volume as a combustor allows one to investigate a hitherto-unused combustion regime beyond the lean flammability limit. The combustion of H 2 , CO, CH 4 , C 2 H 4 , C 3 H 8 , and mixtures of these has been studied in this regime at pressures up to 2 atm in three quite different reactors. The reaction responsible for releasing most of the heat of combustion has a large apparent activation energy in all cases and is very fast. The activation energies and relative rates for different fuels agree with those determined in flames at higher temperatures. The rate of heat release with hydrogen does not depend on the partial pressure of oxygen when the latter is present in large excess, and is proportional to the total pressure. Mixtures of hydrogen with other fuels exhibit lower rates of combustion than does hydrogen alone. A qualitative explanation of the results in terms of the currently accepted mechanism of hydrogen combustion is presented.