In this work, a mathematical model of fuel conversion and energy balance has been developed to study the dynamic behavior of a lean premixed pre-vaporized combustor fed with ethanol/air and ethanol-hydrogen/air mixtures. The combustor was modeled as a well stirred reactor (WSR). Results show that, for a simplified model reaction, Hopf bifurcations occur. Spontaneous oscillations have been found, suggesting that the combustion reaction plays an important role in the development of dynamic regimes. Hydrogen addition stabilizes ethanol combustion, damping the oscillations. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.