LAUSR

A sample of unadditized diesel fuel was passed through an optically accessible model diesel injector return valve, which consisted of two successive nozzles connected to an intermediate fuel gallery. The first nozzle was cylindrical, while the second nozzle was stepped. The fuel was observed to produce a multi-phase, cavitating flow and a luminous blue-violet emission at the entrance to the second nozzle hole. The flow in the upstream intermediate fuel gallery and the first nozzle hole remained single-phase. Spectral analysis of the luminous emission revealed a spectrum with thermal features containing broad spectral lines and peaks at 358, 389, 405, 412, 430 and 475 nm, suggesting that the emission was dominated by π*→π transitions in the alkylated mono-, di-, and tri-aromatics, with additional spectral contributions from CH, C2, C3 and hydrogen (H).