Watery Fuel Diffusion Flames

University Of California-Irvine, Irvine CA

Investigators

Abstract

1605533 - Dunn-Rankin Currently, 90% of worldwide energy utilization comes from the combustion of fossil fuels, and this use is not expected to decline worldwide for the foreseeable future. Consequently, improvements in combustion performance to increase fuel efficiency and reduce the emission of harmful pollutants are important. The classical fire triangle shows that for sustained combustion to occur, heat, fuel, and a supply of oxidizer must be present; a reduction of any of these can make a flame burn less robustly, which may result in a decrease in temperature, an increase in flame fluctuations, and ultimately flame extinction. Interestingly, sometimes these nearly extinguished flames exhibit the highest combustion performance (i.e., high efficiency and low emissions). Since water is commonly used to extinguish unwanted flames, it is important to determine if just the right amount of water can potentially produce high performance near-extinction combustion. In addition, some next-generation fuels have very high water content that can naturally produce this same near-extinction behavior. The proposed research explores the role of water when it is introduced as a fuel side reactant in a non-premixed flame. The broad scientific and technical impact of this work includes an improved understanding of combustion chemistry of systems that incorporate water naturally or artificially to manipulate the combustion process. The project is of great value to undergraduates, graduates, and international scholars interested in sustainable energy; it will incorporate research participation for students at all levels, as well as opportunities to extend professional collaborations. The project will also broaden the participation of underrepresented minorities in STEM fields and as part of the NSF-funded Louis-Stokes Alliance for Minority Participation (LSAMP). The technical focus of the work is to explore the role of water, over a range of pressures between 1-50 atm and operating conditions, in diffusion flames using a co-flow jet and counter-flow burner configuration. This work will look specifically at flame extinction due to the addition of water, which significantly reduces flame temperature and also dilutes the fuel-air mixture. Measurements include flame temperature and concentrations of important radical species involved in inhibiting combustion. The methods for measuring temperature will include thermocouples, thin filament pyrometry, and Coherent anti-Stokes Raman spectroscopy (CARS). Qualitative measurements of OH and CO will employ planar laser induced fluorescence. Experimental results will be compared with computational fluid dynamic calculations and with detailed chemical kinetics calculations for both atmospheric and high pressure conditions. The combination of experiments and calculation will expose comprehensively the role of water in controlling combustion.