An Experimental Investigation of Flame Stabilization in a Heated Turbulent Boundary Layer

For a number of years the significant parameters governing flame stabilization in moving streams have been known. In high speed applications the chemical time delay plays a fundamental role. For the low speed problems the normal flame speed and quenching distance govern stabilization. Unfortunately the transition region between the two groups of problems has not been investigated. Also the actual relation between these parameters and the properties of the combustible mixture has not been established. To investigate these fundamental questions an experiment was set up to study flame stabilization in heated turbulent boundary layers. For wall temperatures above about 1700[degrees]F. the chemical time delay, represented by the length of the heated flame holder wall required for stabilization, was found to be a systematic and reproducible variable. A rational explanation was made for the transition from the low speed stabilization mechanism known to be applicable in unheated turbulent boundary layers and heated laminar boundary layers to the ignition mechanism applicable in heated turbulent boundary layers. An attempt was made to relate the observed stabilization measurements to a theoretical solution based on ignition in a laminar sub-layer. The present methods of solution for such problems were found to be inadequate. A similarity solution yielded an interesting result which agreed fairly well with experiments