INHIBITION OF FLAMES BY IRON PENTACARBONYL

Abstract

In previous research [5-81 we have confirmed that Fe(C0)s is extraordinarily effective, but have also found that its incremental effectiveness decreases rapidly as it is added in higher concentrations. For example, adding 200 ppm of Fe(C0)S to premixed methane-air flames reduces the burning velocity by nearly 50%, but increasing the concentration beyond 200 ppm does not lead to significant additional reduction. The goal of the present research is to understand both the powerful inhibition at low concentration and the lack of additional effect as more inhibitor is added. A critical part of the research on Fe(C0)S is to understand iron pentacarbonyl's diminishing effectiveness at high mole fraction in order to avoid similar behavior in future fire suppressants. We also seek to determine the relative effects of homogeneous and heterogeneous chemistry in the Fe(C0)s inhibition mechanism. If particulates play a key role in the inhibition, then the search for halon alternatives could be directed toward chemicals that produce similar condensed-phase compounds. Our study of flame inhibition is intended to provide insights into flame suppression. Although the processes have different end points (weakening the flame vs. extinguishing it), the underlying mechanism is similar: the agent reduces the overall reaction rate of the fuel-air mixture. Inhibition can be viewed as the stage of suppression in which the inhibitor weakens the flame, making it more vulnerable to extinction by external factors such as heat loss or fluid-mechanical