Detection of precursor event before blowout in a gas turbine type combustor at atmospheric pressure

The need for stringent emission requirements compel modern gas turbine (GT) combustors to work under lean conditions and lower temperatures, thereby reducing NOx emissions. The operation of a combustor close to lean blowout limit increases the risk of a complete flame blowout posing a safety hazard in aircraft engines. A study was carried out on a divergent gas turbine combustor, in order to sense and detect a similar blowout phenomenon in a non/partially premixed swirl flame. Inside combustor, 45° vane angle swirler created weak recirculation zone. New swirler with 5° and 60° at entry and exit respectively was used as replacement. 5 bar and 6 bar of stagnation pressure of air were used as loading parameters during the experimentation. Photodiode sensors and high speed imaging camera were used to record data of flame. It was observed that, bursts (or unsteady events) characterized by an almost complete loss of flame i.e. abrupt extinctions were followed by re-occurrence of flame. 'Precursor events' before flame blowout were detected. These events occurred and re-occurred in an interval of several milliseconds. In both scenarios, high speed visualization was recorded at 1000 Hz for 16-20 seconds. Detection of precursor events for the liquid fuelled combustor will assist in carrying out further research using sensing methods to estimate the proximity of the combustor to LBO. Copyright © 2012 by ASME.