ON THE COOL FLAMES OF METHANE

Methane is an attractive alternate fuel. It burns cleanly and is resis tant to ''knock.'' For many years methane was believed not to give ris e to the phenomenon of cool flame, a process basic to the problem of ' 'knock'' in internal combustion engine. This paper shows that methane exhibits the same combustion events as those observed in higher hydroc arbons: slow combustion; production of hydrogen peroxide; multistage, low temperature ignition; single and multiple cool flames; regions of negative temperature coefficient; and high temperature ignition. The i gnition diagrams are normal, but the cool-flames regions are found at higher temperatures and are much narrower than for higher hydrocarbons . This is the reason why the methane cool flames escaped experimental observation for such a long time. These findings give a rationale for the high, but not absolute, resistance of methane to ''knock.''