Validation and Development of Coupled Computational Fluid Dynamics and Ignition Kinetics Models for Transportation Fuels
Due to increased concerns with global warming and energy sustainability, there is growing motivation to develop more efficient internal combustion engines (ICEs) as well as suitable alternative transportation fuels. Such efforts will be facilitated by accurate modeling of the combustion kinetics of the candidate fuels within the ICE. Modeling combustion in ICEs commonly uses computational fluid dynamic (CFD) models, coupled with chemical kinetic mechanisms. Along with accurately capturing the spray physics and fluid dynamics, it is equally important for these combustion models to include validated chemical mechanisms. Such combinations allow for more efficient experimentation by identifying conditions most likely to lead to improved engine efficiency and reduced emissions. Hydrocarbon fuels used in transportation are complex mixtures of several hundred to several thousand hydrocarbon species. This complexity makes mechanism development and modeling of these fuels difficult, and thus surrogate fuels, which are much simpler but have chemical and physical properties similar to the real fuels, are preferred for experiments and numerical modeling. Current research focus is on validation of ignition kinetic models for surrogate transportation fuels (e.g. n-heptane, iso-octane, n-hexadecane, ethanol), in support of the DOE initiative for New Fuel and Vehicle Systems Optima. This fuels research supports development of advanced combustion engines with high fuel efficiency and reduced emissions, through improved understanding of ignition kinetics which can play a dominate role in controlling the combustion process. Development of advanced compression ignition and low-temperature combustion engines is increasingly dependent on ignition kinetic models. However, rigorous experimental validation of kinetic models has been limited. For example, shock tubes and rapid compression machines are usually restricted to premixed gas-phase studies, precluding the use of more realistic low-volatility fuels. The Ignition Quality Tester (IQT) is a constant-volume spray combustion system designed to measure ignition delay of both high and low-volatility fuels; it therefore has the potential to validate ignition kinetic models. NREL's fuels research platform based on an IQT is used for fuel ignition kinetics experiments, as well as simulations to develop and validate kinetic mechanisms. The proposed effort directly supports FY16 New Fuel and Vehicle Systems Optima AOP tasks for NREL's Advanced Combustion and Fuels research group, and is funded by EERE's Vehicle Technologies Office, Fuels and Lubricants Program.
last modified Nov 02, 2015 08:27 AM