The Effects of Liquid Alkane Fuel Structure on Catalyst-Enhanced Combustion

Abstract

The U.S. Army is developing micro-combustors for use in soldier-portable power generation systems. Many of the challenges associated with micro-combustion can be potentially overcome using a catalyst, but the effects of the catalyst on ignition under the low temperature, atmospheric conditions seen in the field are not well understood. To better understand catalytic ignition phenomena under these conditions, a Catalytic Ignition and Emissions Tester (CIET) was developed and used to investigate the effects of liquid alkane fuel structure during catalyst enhanced ignition. Various mixtures of n-octane and iso-octane, as well as single component n-dodecane and n-hexadecane, were chosen as simple, surrogate test fuels to represent gasoline, jet fuel, and diesel, respectively. Fuel reactivity was shown to decrease with increased branching for all metrics tested while the effects of chain length were less definitive. The global apparent activation energies of all fuels tested were found to be in the range of 41-61 kJ/mol with 95% confidence, significantly lower than those previously reported for non-catalytic hydrocarbon combustion (>100 kJ/mol).