59484 - Evaluation of Blow-Off Dynamics in Aero-Engine Combustors Using Recurrence Quantification Analysis 

The lean blow-out performance of an engine and the ability to re-ignite the flame, especially at high-altitude conditions, are important aspects for the safe operability of airplanes. The operability margins of the engine could be extended if it was possible to predict the occurrence of flame blow-out from in-flight measurements and take actions to dynamically control the flame behaviour before complete extinction. In this work, the use of Recurrence Quantification Analysis (RQA), an established tool for the analysis of non-linear dynamical systems, is explored to reconstruct and study the blow-off dynamics starting from pressure measurements taken from blow-off experiments of real engines. It is shown that the dynamics of the combustor exhibits chaotic characteristics far away from blow-off and that the dynamics becomes more coherent as the blow-off is approached. The degree of determinism and recurrence rate are studied during the entire combustor's dynamics, from stable flame to flame extinction. It is shown that the flame extinction is anticipated by an increase of the degree of determinism and recurrence rate at all investigated conditions. It is also shown that the blow-off event follows the increase of degree of determinism with a time delay of the order of a second. Therefore, the determinism of the system could be a good predictor of blow-off occurrence and could potentially enable control actions to avoid flame extinction. This study opens up new possibilities for engine control and operability. The development of real-time RQA should be addressed in future research.