The influence of pressure on the spontaneous ignition of inflammable gas-air mixtures. I.—Butane-air mixtures

As part of an investigation into explosions of various hydrocarbon-air media at elevated temperatures and pressures, we have recently been deter­mining the influence of varying initial pressures up to 15 atmospheres on their reactivities during slow combustion up to their ultimate ignition points. And as the results obtained in the experiments on the spontoneous ignition of butane-air mixtures have presented some very striking new features, which seem of undoubted importance in regard to the problem of “knock” in internal combustion engines, we are submitting them in the present communication. Hitherto, few investigators have determined spontaneous ignition tempera­tures under pressure and, in particular, little is known concerning the behaviours of mixtures with air of the higher members of the paraffin hydrocarbons. The principal research on this problem has been that of Tizard and Pye, who, employing the adiabatic compression method, found with pentane-, hexane-, heptane-, and octane-air mixtures that with compression ratios of 6·09 to 1 ignition occurred at temperatures of circa 300° C. which ( a ) were dependent upon the observed time-lags between compression and ignition, ( b ) varied but little with mixture composition, and ( c ) were lowered slightly as the paraffin series was ascended.