Lean Blowout Features and Control in a Swirl-Stabilized, Partially Premixed Gas Turbine Combustor

Abstract

*† Early prediction and effective extension of lean blowout (LBO) are desirable for both aero and stationary gas turbines. Due to the complexities of finite thermo-chemistry/turbulence interactions, fuel atomization, evaporation and air/fuel mixing, accurate theoretical prediction of LBO is usually difficult. This paper aims to predict the proximity to LBO based on the phenomenological observations of unique and universal near-LBO features, namely the intensified low frequency combustion oscillations and the increased heat release uniformity when approaching LBO. Several indices, such as the normalized chemiluminescence RMS, pressure RMS, time ratio of the LBO precursor events, modified kurtosis, and the two-point heat release ratio, are developed to quantify the LBO features. All these indices consistently increase when approaching LBO. A unified definition of the LBO proximity based on the online computation of these indices, and a conceptual control scheme capable of simultaneous LBO extension and emission reduction are presented. It is also shown that, in certain circumstances, active LBO control may have to combine with dynamic instability attenuation.