Characterization of Near-Blowout Combustion Oscillations in a Lean, Partially Premixed Gas Turbine Combustor

Lean blowout (LBO) is a major technical challenge for dry-low-emission (DLE) combustion in gas turbine engines. For aero engines, LBO is further exacerbated by a large turndown ratio, sometimes more than ten. Intensified, low-frequency combustion oscillations, possibly caused by local flame quenching and reignition, are usually observed prior to complete blowout. Compared with dynamic instability, these near-LBO combustion oscillations usually occur at much lower frequencies, and are of much less intensity. The current paper presents the LBO phenomenology observed in an atmospheric, turpentine-fueled, partially premixed gas turbine combustor, and characterizes it using spectral analysis, autocorrelation coefficients, phase portrait, fractal dimension, and the largest Lyapunov exponent. All these measures suggest the chaotic behavior of near-LBO dynamics. The fractal dimension is less than 3 for combustion near LBO, which may suggest the possibility of characterizing LBO using low-order models.