Madhavan Poyyapakkam

HYDROGEN COMBUSTION WITHIN A GAS TURBINE REHEAT COMBUSTOR

This paper describes a novel lean premixed reheat burner technology suitable for Hydrogen-rich fuels. The inlet temperature for such a combustor is very high and reaction of the fuel/oxidant mixture is initiated through auto-ignition, the delay time for which reduces significantly for Hydrogen-rich fuels in comparison to natural gases. Therefore the residence time available for premixing within the burner is reduced. The new reheat burner concept has been optimized to allow rapid fuel/oxidant mixing, to have a high flashback margin and to limit the pressure drop penalty. The performance of the burner is described, initially in terms of its fluid dynamic properties and then its combustion characteristics. The latter are based upon full-scale highpressure tests, where results are shown for two variants of the concept, one with a pressure drop comparable to today’s natural gas burners, and the other with a two-fold increase in pressure drop. Both burners indicated that Low NOx emissions, comparable to today’s natural gas burners, were feasible at reheat engine conditions (ca. 20 Bars and ca. 1000C inlet temperature). The higher pressure drop variant allowed a wider operating window. However the achievement of the lower pressure drop burner shows that the targeted Hydrogen-rich fuel (70/30 H2/N2 by volume) can be used within a reheat combustor wit hout any penalty on gas turbine performance.