CFD Prediction of Partload CO Emissions using a Two-Timescale Combustion Model

Todays and future electric power generation is characterized by a large diversification using all kind of sources including renewables resulting in non coherent fluctuations of power supply and power usage. In this context, gas turbines offer a high operational flexibility and a good turn down ratio. In order to guide design and down select promising solutions for improving part load emissions a new combustion model based on the assumption of two separate time scales for the fast premixed flame stabilization and the slow post flame burnout zone has been developed within the commercial CFD code ANSYS CFX. This model enables the prediction of CO emissions generally limiting the turn down ratio of gas turbines equipped with modern low NOx combustion systems. The model will be explained and validated at lab scale conditions. Finally application of the model for a full scale analysis of a gas turbine combustion system is demonstrated.