Experimental observation of lifted flames in a heated and diluted coflow

Lifted flames have attracted significant research over many years due to the importance of fundamental understanding of the stabilization mechanism. More recently, lifted flames in a hot coflow have been used to investigate autoignition properties of jet flames. Several experimental and numerical studies to predict the autoignitive liftoff characteristics of a jet in a vitiated coflow have recently appeared in the literature. The configuration of a jet issuing into a heated and diluted oxidant stream can also emulate the fundamental operating conditions of MILD combustion. This paper investigates similarities and differences of the liftoff behavior of jet flames under a wide variety of coflow oxidant conditions, ranging from autoignitive conditions to MILD combustion. The liftoff behavior is observed to not be monotonic with either coflow temperature or oxygen content. The results clearly indicate that there is a fundamental transition in the stabilization mechanism, depending on the oxidant stream properties. © 2012 American Chemical Society.