BI-STABLE FLAME BEHAVIOUR OF HEAVY DUTY GAS TURBINE BURNER. RANS, LES AND EXPERIMENT COMPARISON

摘要

VeLoNOx™ series (Very Low NOx) burners have been developed by Ansaldo Energia to satisfy the most restrictive emissions limits required by various countries. For these combustion systems the characterization of the field of stable operating conditions is a key design element. In particular, flame transition is of paramount importance for the stability of these combustion systems. Usually, this phenomenon occurs during load ramps and is characterized by a change of the flame shape, occurring in a well-defined load range. Proper flame shape control is essential to achieve more stable operating conditions up to base load. At transition, experiments in a full scale pressure test-rig clearly show both a modification of the flame shape, a change of the measured air side burner effective area, and a reduction of the combustion chamber wall temperatures. LES simulations were conducted using the same boundary conditions as RANS simulations discussed in a previous work . In this paper, we show that both RANS and LES were able to correctly predict flame transition and a RANS-LES-Experiment comparison is performed.