Real-Time Prediction of Incipient Lean Blowout in Gas Turbine Combustors

The present paper addresses real-time prediction of incipient lean blowout in partially premixed, liquid-fueled gas turbine combustors. Near-lean-blowout combustion is characterized by the intensified, low-frequency combustion oscillations (typically, below 30 Hz). Two indices, namely, the normalized chemiluminescence root mean square and the normalized cumulative duration of lean blowout precursor events, are recommended for lean blowout prediction. Both indices are associated with the statistical characteristics of the flame structure, which changes from the normal distribution to the Rayleigh distribution at the approach of lean blowout. Both indices change little within a large range of equivalence ratios and start to shoot up only when lean blowout is approached. To use the two indices for lean blowout prediction, one needs to perform a detailed a priori lean blowout mapping undersimulated engine operating conditions. However, the mapping can be done without running the engines very close to lean blowout.