Inhibitor rankings for alkane combustion

The effect of hydrocarbon fuel type on the ranking of inhibitor effectiveness has been investigated through computer simulations. The approach involves carrying out sensitivity analysis on the detailed kinetics of the combustion of C-1-C-4 hydrocarbons. Tt is demonstrated that the main reactions determining burning velocities are the same. Similar suppressant rankings from the combustion of different hydrocarbon fuels are largely due to the reactions of a number of small radicals that are common to ail of these systems. Inhibitor addition reduces the concentration of these radicals with the active agents being recycled by the common breakdown products of the fuel. Inhibitor effectiveness of additives in a variety of fuels was analyzed using experimental data on the effects of additives on burning velocity in small additive concentration ranges. An universal ranking of additive efficiency is presented. The results demonstrate that the active agents in practically all cases are the small inorganic compounds created from decomposition processes. Inhibition effectiveness of agents is at a maximum at low concentrations. At higher concentrations, saturation effects, brought about by the approach of active radicals to their equilibrium concentrations, lead to substantial decreases in the effectiveness of high efficiency suppressants in comparison with their effects at small concentrations. The results show that the probable maximum increase in total flame suppression effectiveness of high efficiency agents will not exceed one order of magnitude in molar fractions in comparison with the effect of halon 1301 (CF3Br). (C) 2000 by The Combustion Institute.