Inhibitor influence on the bistability of a CSTR

Methane combustion in a continuously stirred flow tank reactor (CSTR) in the presence and absence of chemical inhibitors such as CF3I, CF3Br, CF3H, and a chemically inert gas witt high heat capacity is simulated with the CHEMKIN program. The aim of the work is to determine the differences in results arising from the use of the various inhibitors with the aim of establishing the capability of CSTR experiments to give a rank ordering of suppressant power. The chemical inhibitors have the general tendency to raise the steady-state temperature. A high heat capacity inert gas leads to the opposite effect. Only near extinction and self-ignition can one obtain a proper scale of flame suppression capability. The curves for combustion efficiency, (CO2/[CO + CO2]), near the extinction point lead to results where the data for the additives all fall within the envelope for stoichiometric methane/air combustion in the extinction region. For self-ignition, the transition from the mushroom to the isola form of the stability curves appears to be another property that is highly sensitive to suppression power. These observations may serve as a basis for testing inhibition capabilities. Copyright (C) 1997 by The Combustion Institute