Ultraviolet Spectroscopy of Engine-Fuel Flames 270002
DETAILS are given of the method of control of the engine so that quantitative and reproducible measurements of detonation and comparisons with spectra can be made. Typical data are tabulated and photographs are shown of the free-burning flames of hydrogen, carbon monoxide, methane, gasoline in a blow-torch, and the like. The spectra of explosion and of detonation in the engine confirm earlier conclusions. By means of a synchronous shutter, the spectra of radiation during the four quarters of a stroke are obtained for straight-run gasoline under detonating and non-detonating conditions for the same fuel containing tetraethyl lead, aniline and iodine as knock suppressers and for cracked-gasoline blends. The outstanding result is that, during detonation, the first-quarter spectrum extends far into the ultra-violet, that of the second quarter, a somewhat less distance; the third and fourth quarters are characterized by very little radiation energy. During normal explosion, or when knock suppressers, irrespective of their chemical nature, are used in the engine under detonating conditions, the spectra of all four quarters have the same length and essentially the same intensity. Lead emission-lines from tetraethyl lead appear only in the first quarter. These and other facts are considered in the light of theories of the mechanism of knock suppressers and inducers.
In the discussion following the paper the value of spectroscopic investigation of the fluid reactions in an engine is set forth, data to show that the ionization theory is wrong are referred to, and an illustrated description of a theory of detonation is presented.