Abstract
Formaldehyde, carbon monoxide and hydrogen are the typical intermediates during blue flame period in low-temperature ignition of hydrocarbons. A mixture composed of only these three components and oxidizer air was compressed up to a blue-flame-dominant temperature regime using a premixed compression-ignition engine, and a two-stage ignition behavior was observed. Chemiluminescence spectra during the induction period of CO/HCHO/Air ignitions were detected in low-temperature flames. The formaldehyde was consumed much earlier than H2 and CO; which would not be oxidized until the phase that the formaldehyde concentration becomes very low. Ignition delays are very sensitive to the presence of formaldehyde even though the amount was small. The final heat release could be recognized as a carbon monoxide explosion.
