Dynamic behavior of intermittent combustion oscillations in a model rocket engine combustor

Chinami Aoki,Shigeru Tachibana,Seiji Yoshida,Hiroshi Gotoda

doi:10.1063/5.0001900

Abstract

We experimentally study the dynamic behavior of intermittent combustion oscillations by time series analysis in terms of nonlinear forecasting, symbolic dynamics, and statistical complexity, including the detection of the change in dynamical state based on symbolic dynamics and graph networks. We observe sudden switching back and forth between irregular small-amplitude and regular large-amplitude pressure fluctuations. The nonlinear local prediction method, permutation spectrum test, and the Rényi complexity–entropy curve clearly identify the possible presence of chaotic dynamics in small-amplitude pressure fluctuations during intermittent combustion oscillations. The network entropy in ordinal partition transition networks allows us to capture a significant change in dynamical state switching between chaotic oscillations and noisy limit cycle oscillations.

Highlights

A self-excited combustion instability, referred to as thermoacoustic combustion oscillations, arises as a mutual interaction between the heat release rate and longitudinal/transverse acoustic pressure fluctuations,[1,2] giving rise to various nonlinear dynamic behaviors
We experimentally study the dynamic behavior of intermittent combustion oscillations by time series analysis in terms of nonlinear forecasting, symbolic dynamics, and statistical complexity, including the detection of the change in dynamical state based on symbolic dynamics and graph networks
We study the dynamical state during intermittent combustion oscillations by adopting three important analytical methods for the temporal evolution of pressure fluctuations inside the combustor: the nonlinear local prediction method,[7] permutation spectrum test,[15] and the Rényi complexity–entropy curve analysis.[16]

Summary

Introduction

A self-excited combustion instability, referred to as thermoacoustic combustion oscillations, arises as a mutual interaction between the heat release rate and longitudinal/transverse acoustic pressure fluctuations,[1,2] giving rise to various nonlinear dynamic behaviors. This instability leads to the fracture damage of combustors and continues to pose significant challenges in engine development. A state of intermittency significantly emerges in turbulent combustors while transitioning from combustion noise to limit cycle oscillations and vice versa in terms of the Reynolds number,[11–13] equivalence ratio,[11–13] and flame density ratio.[14]

Objectives

Methods

Conclusion