The poorly-understood cool-flame combustion regime occurs at moderate temperatures and elevated pressures, and could be used to convert various fuels to a hydrogen-rich gas (syngas) for use in fuel cells. It promises the benefits of low NOx pollutant emissions and low soot formation. The development of a practical cool-flame reformer will depend on understanding the interplay between the different chemical reaction rates that result in cool-flame combustion. Due to a lack of experimental data or validated kinetic models, the usefulness of cool flames for syngas production cannot currently be assessed. Experiments will be performed in constant-pressure and constant-volume reactors at pressures near 20 atm using a variety of fossil and alternative fuels, such as natural gas, methanol, ethanol, and biodiesel. Advanced laser-diagnostic and gas-sampling techniques will be utilized to perform detailed, quantitative measurements. These experimental measurements will be compared to simulations to test the predictions of thermo-chemistry models. Existing models will then be revised, and new models developed, to accurately predict experiment.
Another important combustion regime occurs during the ignition of fuel-air mixtures. These low-temperature chain-initiation reactions are also important in the cool-flame combustion regime described above. To validate models under this regime, ignition experiments will be performed in shock tubes with optical diagnostic measurements and the results will be compared to model predictions. The fuels studied will be natural gas, methanol, ethanol, and biodiesel. The progress of the chemical reaction will be monitored by detecting intermediate species involved in the combustion process, such as CH and OH radicals. The concentration of these radicals can be measured by monitoring their chemiluminescence emissions at high speeds, allowing the progress of the entire ignition event to be tracked.
High-temperature combustion (flames) of alternative fuels:
In flames, high-temperature oxidation reactions are important and, therefore, premixed and diffusion flames can provide another complementary test-bed for combustion models of alternative fuels. Flame experiments will be performed in stagnation flows at variable pressure, and velocity and species measurements, performed using laser diagnostics, will be compared to the predictions of available models. Fuels studied will be natural gas, methanol, ethanol, and biodiesel. Model improvement and development will be an integral part of this coupled experimental, numerical simulation, and modeling effort.