Goals

Advance a multiscale approach to collaborative reaction kinetic model development and validation, by focusing team efforts on particular alcohol fuels. The team’s initial focus has been on n-butanol. This has recently broadened to include detailed kinetic modeling of other isomeric butanols, plus some comparisons with smaller alcohols and the corresponding ketones, aldehydes, and enols. In the future we expect to use what we have learned from the butanol study to develop improved detailed models for ethanol, and other alcohols.

Deliverables

• A demonstration to the combustion chemistry community of the benefits of working as a team to unravel the chemistry of proposed alternative fuels much more rapidly than can be achieved by uncoordinated efforts in groups operating individually.
• A reaction model, including thermochemical and transport databases, for combustion of all four isomers of butanol, including low-temperature chemistry, from fuel-lean to fuel-rich/pyrolysis conditions, with well defined uncertainties and predictability. In future years, we expect to expand this to other alcohol fuels as resources permit.
• An evaluated combustion experiment database for the target fuels, including data collected in shock tubes, rapid compression machines, flow reactors, and laminar flames.
• Identification of the most important parameters (rate coefficients and molecular properties) in the model, so that the model can be used reliably to predict the performance of butanol in engines. 
• Accurate computation of the important parameters that are not available from direct experiments, using quantum chemistry and improved rate-theory methods. 
• Estimates of the uncertainties of all the parameters in the model, and the basis for these uncertainties.

Relevance to Practical Fuel Combustion

• Strategies for using some butanol isomers as fuel additives are approaching commercialization; they have several important practical advantages over ethanol (e.g. lower evaporative emissions and so lower contribution to smog, miscible with gasoline in all proportions) which may allow them to succeed commercially on a large scale despite competition with the commercially well-established ethanol. 
• It is very interesting scientifically to compare the combustion of all the butanol isomers, to begin to develop a systematic understanding of how the structure of an alcohol fuel affects its performance.
• Several alcohols fuels are in the market or soon to enter it, and all would benefit from better understanding of the fundamentals of alcohol combustion chemistry. Ethanol is widely used in the USA and Brazil, but existing models do not accurately predict its combustion performance. Methanol is widely used in China. Improved understanding of methanol chemistry would also be helpful in predicting DME performance.

Relevance to Other Thrusts

• Butanol was the first fuel studied by the team, and we developed many of our team’s methods for effective interaction and collaboration through our work together on butanol.
• Our results on butanol emphasized the need to improve the rate coefficients, etc., for the small molecules formed from butanol (and other fuels), since many of the butanol combustion experiments are more sensitive to these parameters than to butanol chemistry per se. This has led to the Foundation Fuels thrust.
• Several technical issues encountered during the butanol work will arise again in the Biodiesels Thrust, e.g. (1) need for better methods for coupled internal rotors; (2) methods for modeling effects of transient H-bond formation in transition states; (3) methods for extrapolating experimental flame speeds to zero-strain-rate limit. The Biodiesels thrust will benefit from all these methodological improvements made during the Alcohols project.