Gas temperature and boundary layer thickness measurements of an inert mixture using filtered broadband natural emission of species at Rapid Compression Machine conditions (Part II)

摘要

Our understanding of the combustion process is hindered by the boundary layer at the optical access. To be detected by the camera, the infrared emission of the mixture (or the laser) should pass the boundary layer at the window of the combustion system. Regardless of the type of experimental techniques used (either the laser or natural emission of the species), part of the emission could be absorbed by the boundary layer due to its low temperature. Hence, the measured data includes some uncertainty and errors due to the boundary-layer absorption and its thickness (it reduces the optical length), which have not yet been quantified due to the unavailability of the boundary layer thickness, especially during a transient process such as engine compression stroke.