Investigation of Flame Stability Characteristics of the EV Burner on the GT13E2 Engine

Abstract

The development and optimization of dry low NOx combustors for industrial gas turbines could largely benefit from better understanding of the way the burners stabilize lean premixed turbulent flames. This has motivated the present work where the stabilization properties of turbulent (partially) premixed flames in the annular combustor of the ALSTOM GT13E2 gas turbine equipped with the EnVironmental (EV) burner are studied. The study benefits from the results of a previous analysis where the flame anchoring properties have been determined in single EV burner configuration, using a one-dimensional boundary layer type model and Large Eddy Simulation (LES). These properties, which are confirmed by experiments on single burner atmospheric and high pressure test rigs, consist in two possible stabilization modes for the flame: a) anchored just downstream the exit of the burner or b) displaced inside it, depending if the bulk equivalence ratio is below or above a characteristic value. The change from one flame stabilization mode to the other implies a change in the NOx characteristic versus flame temperature due to different levels of unmixedness (higher when the flame is stabilized inside the burner). Such a change in the NOx characteristic is found also in the GT13E2, indicating that flames in the combustor of this engine have same stabilization properties as seen on single burner rigs. It is seen that low frequency pulsations—typically anticipating the approaching of the lean stability limit—becomes discernible on the GT13E2 as soon as the equivalence ratio falls below the characteristic value separating the two flame stabilization modes. This finding gives the opportunity of more effective extrapolation of single burner test rig data to engine conditions. Finally, a simple model which can determine the effect of propane content in natural gas on the conditions where the transition between the two stabilization modes takes place is developed.