Staged/sequential combustion is a state of the art method to provide operational flexibility and reduced emissions in gas turbines. To use Computational Fluid Dynamics (CFD) to study such systems a reliable and computationally inexpensive turbulent combustion model is necessary. A key requisite for such a model is the accurate determination of the flame location in order to predict emissions, flame dynamics, and temperature distribution. Previously a model was developed for reheat combustion, based on a progress-variable method using autoignition reactors. However, sequential combustion systems are now being implemented where both auto-ignition and flame propagation are important. Consequently, the reheat model has been extended to consider flame propagation in mixtures that do not auto-ignite. This has been achieved by incorporating a small proportion of combustion products in the reactant mixture considered by the reactor. This approach has broadened the model's applicability to address the full space between autoignition and flame propagation regimes. The revised model has been validated by comparison with reacting jet in vitiated cross-flow experiments demonstrating a significantly better prediction of the position of both attached and lifted flames than the original model.
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