Effect of wall thermal inertia upon transient thermoacoustic dynamics of a swirl-stabilized flame

TL;DR

This study highlights the significant impact of wall thermal inertia on the transient thermoacoustic stability of a swirl-stabilized combustor, demonstrating how wall temperature changes influence instability development and hysteresis effects.

Contribution

It introduces experimental evidence and a low-order model showing the critical role of wall thermal inertia in thermoacoustic instability dynamics.

Findings

Wall temperature increase induces flame topology changes.

Thermoacoustic instability is linked to wall thermal inertia.

Hysteresis effects observed during dynamic operation.

Abstract

This paper shows the importance of considering the thermal state of a combustor to investigate or predict its thermoacoustic stability. This aspect is often neglected or regarded as less important than the effect of the operating parameters, such as thermal power or equivalence ratio, but under certain circumstances it can have a dramatic influence on the development of the instabilities. The paper presents experimental results collected from a combustor featuring a lean swirl-stabilized flame exhibiting thermoacoustic instability at some operating conditions. It is shown that this instability is caused by a change of the flame topology that is induced by the progressive increase of the wall temperature with the thermal power. This dependence of the instability on wall temperature leads to inertial effects and hysteresis when the operating condition is changed dynamically. A low-order model of the system reproducing this remarkable dynamics is proposed and validated against the experimental data.