Abstract

This work summarizes results for a three cylinder fuel injector that has been adopted as a model for investigating combustion phenomenon in the 8-Foot High Temperature Tunnel (HTT) at NASA Langley Research Center. The primary objective here is to understand the flame lift-off phenomenon in the three cylinder fuel injector geometry in two-dimensions. Three chemistry models, namely fast chemistry, one-step kinetics and two-step kinetics are employed in conjunction with a computational fluid dynamics code to analyze the flame structure and flame lift-off characteristics downstream of the fuel injector.

Effects of fuel jet velocity and chemistry model on the flame lift-off phenomenon from the injector surface are analyzed by considering simultaneously the combined convection (outside the cylinders) and conduction (inside the cylinders). Results indicate that as the fuel jet velocity is increased, the flame is transformed from a wrap around configuration to a clearly lifted flame configuration. Of the three chemistry models considered in the present study, only the two-step chemistry model predicts a clearly lifted flame. The ability of the CFD code to predict lifted flame is important since a slightly lifted but stable flame is of paramount importance to the operation of the combustor.

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