Gas temperature and boundary layer thickness measurements of an inert mixture using filtered broadband natural species emission (Part I)

Abstract

A new experimental methodology to simultaneously measure gas temperature and boundary layer thickness was developed and explained for the first time in this work. The new methodology is based on the line-of-sight broadband filtered natural infrared emission of species and it solves one of the main challenges of using the broadband spectroscopy to measure gas temperatures: quantification of the absorption of the core gas infrared emission due to the cold boundary layer on the optical access of combustion systems. To evaluate and validate the new methodology, it was applied to measure the gas temperature and boundary layer thickness of a mixture of methane, carbon dioxide, and nitrogen using Rapid Compression Machine RCM). High-speed infrared cameras with two filters at wavelength ranges of 3.329 to 3.629 μm and 4.069 to 4.445 μm were used to measure the filtered natural emission of methane and carbon dioxide during the post-compression period. Measured gas temperatures at two conditions were compared with the modeled temperature calculated using the isentropic compression equation. Excellent agreement, within 1%, was reached between modeled and measured gas temperatures.