Modeling of Flame Blowout and Emissions in Vitiated Combustion of Biofuels

Abstract

The widening gap between the demand and supply of fossil fuels has catalyzed the exploration of alternative sources of energy. Interest in the Power, Water Extraction and Refrigeration (PoWER) cycle, proposed by the University of Florida, as well as the desirability of using biofuels in distributed generation systems, has motivated the exploration of biofuel vitiated combustion. In earlier research efforts on the PoWER engine, lower emissions have been demonstrated by using conventional diesel fuels, achieved through high levels of exhaust gas recirculation (EGR) in semiclosed (SC) mode of operation, inherent in the PoWER cycle. In this work, combustion performance of biofuels has been investigated through modeling of chemical kinetics of ethanol, dimethyl ether (DME) and biodiesel surrogate methyl butanoate (MB), and comparison was made against conventional diesel fuel that was modeled using surrogate fuel n-heptane. The combustion performance was compared over a range of equivalence ratios and EGR levels. The simulations were performed using a constant-pressure continuously stirred tank reactor (CSTR) model developed using the Camera combustion code, implemented in C++. Results have been presented showing comparative trends in emissions, stability and combustion efficiency.