PREDICTION OF THE BLOWOUT LIMITS OF TURBULENT NONPREMIXED JET FLAMES USING THE PREMIXED COMBUSTION THEORY

摘要

A method is proposed for predicting the blowout limits of lifted nonpremixed jet flames in a coflowing air stream. Based on the premixed combustion theory, the velocity at the base of a lifted flame is balanced by the turbulent flame speed. From this simple concept, Kalghatgi derived a universal formula for calculating the blowout limits of free jet flames. The authors aimed to extend the same concept to lifted flames in a coflowing stream. Local flow parameters needed to estimate the turbulent burning velocity were determined using a RANS model. Results show that at blowout conditions, the local jet velocity is approximately equal to the turbulent burning velocity estimated using Bray's model at the blowout location. Furthermore, this method allows the blowout limits to be predicted through an iterative procedure for a variety of operating conditions. It was shown that there is good agreement between calculated and experimental blowout limits.