Optical Measurements of Hydrocarbons Emitted from a Simulated Crevice Volume in an Engine

The process of hydrocarbon emission from an engine crevice was simulated in an operating research engine by the introduction of a small tube into the combustion chamber. This simulated crevice volume was used to determine the fate of unburned hydrocarbons that interact with the crevice. Shadowgraph photography and spontaneous Raman spectroscopy were used to determine flow patterns, temperatures, and hydrocarbon concentrations 1 mm from the tube opening. Hydrocarbon species were first detected at the tube exit late in the expansion stroke, long after the start of outflow from the simulation volume. A flame was never observed near the tube exit. Unburned hydrocarbons exiting the tube did not undergo rapid oxidation at temperatures up to 1400 Kelvins.