Chemiluminescence Measurements During HCCI Combustion
HCCI combustion is a chemically controlled process, therefore insights into the nature of the chemical species is important. One non-intrusive method of identifying the existence of chemical species is chemiluminescence – natural light generated during the combustion. The spectral characteristics of light emitted from the combustion process can provide critical insights into the chemical kinetic processes. In this study, an optical fiber bonded to a metal plug was installed in the spark plug hole of an all-metal engine. The engine was fired, without any modifications, in an HCCI combustion mode. The optical fiber was directed to an imaging spectrometer that separated the light into its component wavelengths along a line that was as tall as the fiber diameter. A special kinetic spectrograph camera, which can acquire rows of data in rapid succession, was used to acquire the time-resolved spectra.
The movie shows the measured chemiluminescence spectra at the different times in the heat release process, which are identified by the moving vertical black line on the heat release rate (HRR) plot. Early in the heat release process there is very little light emission, and what emission can be detected is relatively broadband. The emission in the first half of the combustion event and at the peak heat release period is characterized by the presence of formaldehyde (HCHO) and the HCO radical in the 300-350 nm range, and the CH radical near 430 nm. Later in the combustion event the emission from the OH radical near 310 nm appears, and is present until the end of the measurements.
Acknowledgements: This work was performed by Rinaldo Augusta and was supported by General Motors.
Publication: SAE Paper 2006-01-1520