Abstract
In nonlinear dynamics, there are three classic routes to chaos, namely the period-doubling route, the Ruelle–Takens–Newhouse route and the intermittency route. The first two routes have previously been observed in self-excited thermoacoustic systems, but the third has not. In this experimental study, we present evidence of the intermittency route to chaos in the self-excited regime of a prototypical thermoacoustic system – a laminar flame-driven Rijke tube. We identify the intermittency to be of type II from the Pomeau–Manneville scenario through an analysis of (i) the probability distribution of the quiescent epochs between successive bursts of chaos, (ii) the first return map, and (iii) the recurrence plot. By establishing the last of the three classic routes to chaos, this study strengthens the universality of how strange attractors arise in self-excited thermoacoustic systems, paving the way for the application of generic suppression strategies based on chaos control.
Highlights
Despite extensive research, thermoacoustic instability remains a serious problem in many combustion devices, such as gas turbines and rocket engines
We focus on how chaos arises after the onset of thermoacoustic instability, when the system is in a more dangerous state characterized by high-amplitude self-excited nonlinearly saturated oscillations
Those aperiodic fluctuations showed signs of high-dimensional chaos (Tony et al 2015), they arose before the onset of full-blown thermoacoustic instability, implying that the intermittency route to chaos has yet to be established in the self-excited regime of a thermoacoustic system
Summary
Thermoacoustic instability remains a serious problem in many combustion devices, such as gas turbines and rocket engines. It arises from positive feedback between the heat-release-rate (HRR) oscillations of an unsteady flame and the pressure oscillations associated with the combustor acoustics (Poinsot 2017). The term ‘self-excited’ refers to oscillations that have saturated nonlinearly after the onset of thermoacoustic instability. There is a need to better understand how self-excited thermoacoustic oscillations arise in combustion systems, so that they can be avoided or suppressed
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