Flashback and self-ignition in the premixing zone of typical gas turbine swirl combustors in lean premixed operation are immanent risks and can lead to damage and failure of components. Thus, steady combustion in the premixing zone must be avoided under all circumstances. This study experimentally investigates the flame holding propensity of fuel injectors in the swirler of a gas turbine model combustor (A2EV burner) with premixing of H2-NG-air-mixtures under atmospheric pressure and proposes a model to predict the limit for safe operation. One jet-in-crossflow-injector (JICI) and three trailing edge injectors (TEIs) were tested. OH* chemiluminescence and OH-PLIF inside the swirler were applied. The fuel-air-mixture was ignited inside the swirler in proximity to a fuel injection hole with a single laser pulse during steady operation. If the flame was washed out of the premixing zone not later than four seconds after the ignition the operation point was defined as safe. Operation points were investigated at three air ratios, 573 K or 673 K air preheat temperature and 40 to 100 vol.% hydrogen in the fuel. The determined safety limit for atmospheric pressure yields a similarity rule based on a critical Damköhler number. Additionally, the proposed rule is applied at conditions typical for gas turbines.
Flame Holding in the Premixing Zone of a Gas Turbine Model Combustor after Forced Ignition of H2-NG-Air-Mixtures
2016
Article (Journal)
English
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