Temporal kurtosis of dynamic pressure signal as a quantitative measure of combustion instability

Abstract

In this study, the kurtosis of dynamic pressure (DP) signal is implemented to quantify the thermoacoustic stability of a combustion process. The variation of the temporal characteristics of DP signal experiencing the three phases of thermoacoustic stability (i.e., stable, transitional, and unstable with limit cycle oscillation) was explained in terms of the temporal kurtosis (TK), the instantaneous kurtosis evaluated with a subset of DP signal. The explanation suggested that TK would be a promising parameter as a quantitative measure of combustion instability (CI). The feasibility of TK as an indicator of CI was investigated using DP data obtained from combustion tests with a rocket engine, with a lab-scale gas turbine combustor, and with a lab-scale aero engine combustor. In these feasibility studies, the time history of TKs reflected the temporal changes in combustion stability during the combustion processes successfully. It turns out that TK can serve as a real-time indicator of the change in stability condition and also as a precursor of upcoming severe instability. It is expected that the implementation of TK in quantifying the progress of thermoacoustic instability would significantly enhance the performance of commercialized monitoring systems of CI.