Abstract
The effect of swirl on lifted flames in a nonpremixed jet has been studied experimentally by rotating a nozzle to generate a continuous swirl. A model for turbulent lifted flames, based on turbulent large scale structure, is extended to account for the effect of swirl in the prediction of lift-off heights.
Results show that the lift-off height decreases linearly with nozzle rotational speed in turbulent jets. The model for swirl jets predicts that a normalized lift-off height depends solely on swirl number, and experimental results substantiate this prediction. For laminar jets, the lift-off height shows a nonlinear dependence on nozzle rotational speed and becomes independent of jet velocity as the swirl number increases. These characteristics are attributed to the jet breakup behavior in swirl jets.