Early detection of the combustion instabilities by quantifying diagonal-wise measurements of joint recurrence plots of pressure and radiant energy fluctuations

This article presents a study of the early detection of combustion instabilities of a 250 kW liquid rapid premixed oil swirled burner. The main objective was the calculation of indexes, based on a chaotic analysis, able to detect in advance the combustion instabilities. In the combustor, the air mass flow rate was kept constant, and in order to induce the combustion instabilities, the fuel mass flow rate was adjusted during the experiments in which pressure and radiant energy fluctuations were simultaneously measured from the combustion chamber. In this chaotic analysis, joint recurrence plots were calculated in order to analyze the dependence between the pressure and radiant energy fluctuations. Hence, a diagonal-wise quantification was applied to the joint recurrence plots to calculate four indexes: the τ-recurrence rate index R R τ, the τ-determinism index D E T τ, the τ-average diagonal line length index L τ, and the τ-entropy index s τ. The results show that all four indexes were capable of sorting all cases under analysis into two groups: the “combustion noise regime” due to the low-amplitude aperiodic oscillations and the “combustion instability regime” due to the high-amplitude periodic oscillations. In addition, early detection of the transitions were also detected. Therefore, the results presented in this research showed that the four indexes were effective precursors in order to detect in advance the combustion instabilities.