HYDROGEN COMBUSTION WITHIN A GAS TURBINE REHEAT COMBUSTOR Madhavan Poyyapakkam, John Wood, Steven Mayers, Andrea Ciani, Felix Guethe, Khawar Syed Alstom Baden, Switzerland ABSTRACT 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 high- pressure 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 H 2 /N 2 by volume) can be used within a reheat combustor without any penalty on gas turbine performance. INTRODUCTION Alstom is investigating the development of technologies for pre-combustion capture, where the Carbon is extracted upstream of the gas turbine, resulting in a Hydrogen-rich fuel. Such a fuel is very reactive and introduces significant challenges for lean premixed systems, as flashback within the burner can occur, which, if not leading to hardware damage, will result in high NOx emissions. Research on lean premixed Hydrogen combustion for gas turbines has been reported on several occasions, e.g. [1]. The focus of the present paper however is lean premixed Hydrogen combustion within a reheat combustor, such as the SEV within Alstom’s GT24 and GT26 gas turbines [2]. In these machines, there are two combustors, a high pressure combustor (EV), located between the compressor and a high pressure turbine stage, and a reheat combustor (SEV) located between the high and low pressure turbines, as shown in Figure 1. Figure 1 - Cross-section of the GT24/GT26 engine displaying the relative combustor positions The reheat combustor operates at a pressure of ca. 20 bars and the exhaust gases from the high-pressure turbine, the oxidant, has a temperature of ca. 1000C. Under these conditions Annular EV Combustor Annular SEV Combustor SEV Fuel Lance EV Burners Compressor HP Turbine LP Turbine Proceedings of ASME Turbo Expo 2012 GT2012 June 11-15, 2012, Copenhagen, Denmark GT2012-6 All rights reserved. Information contained in this document is provided without liability for information purposes only and is subject to change without notice. No representation or warranty is given or to be implied as to the completeness of information or fitness for any particular purpose. Reproduction, use or disclosure to third parties, without prior express written authority, is strictly prohibited. 1 Copyright © 2012 by Alstom Technology Ltd.