Ignition Studies for Kinetic Mechanism Development and Validation

Project began in 2017 and was completed in 2020. It is closely related to a previous ARC project and is part of the Combustion Chemistry Cluster.

Given the potential for changes in powertrain design that autonomous vehicles can enable, it is all the more important to develop effective, accurate and predictive powertrain design tools. For the engines of these autonomous vehicles, whether the vehicle is hybridized or not, analysis led design strategies are critical to developing optimized engine designs that fully exploit the potential benefits of autonomy in ground vehicles.

The primary objectives for this project were to significantly advance the predictive simulation capabilities for the internal combustion engines that are the foundation of the ground mobility of the U.S. Army and to develop methods for engine design that are responsive to continuing shifts in the fuels supplying the U.S. military. Since real jet fuels are mainly comprised of hundreds of hydrocarbon molecules, the development of validated, predictive and multi-scale combustion models is a challenge to implement within the current scope of engine level CFD applications. Therefore, practical simulation of the diesel engine combustion process required the use of simplified chemical kinetic models and the consideration of model compounds or mixtures of model compounds, referred to as surrogate fuels. To be useful for combustion within practical devices, the surrogates must successfully emulate the targeted physical properties and gas phase combustion behavior of the real fuel with a limited number of pure components.

For this project, which represented one component of the Combustion Chemistry Cluster, the research objectives were to generate ignition data for the purpose of quantifying fuel reactivity and providing high fidelity data for developing reaction theory and reaction mechanisms, and for developing and validating reduced kinetic mechanisms for use in engine simulations. To achieve these objectives, an experimental approach was used with combines the strengths of two existing experimental systems. The first is a modified CFR Octane Rating Engine with added instrumentation that generated the data needed for the validation of kinetic mechanisms and optimization of the reduced mechanisms. The second is the University of Michigan rapid compression facility which is a unique system that was used to generate ignition and reaction pathway data at kinetically limited conditions relevant to engine conditions.

Publications:

• Kang, D., V. Kalaskar, D. Kim, J. Martz, A. Violi, A. Boehman. Experimental characterization of jet fuels under engine relevant conditions - Part 1: Effect of chemical composition on autoignition of conventional and alternative jet fuels. To appear in Fuel, 2018.
• Kang, D., D. Kim, V. Kalaskar, A. Violi, A. Boehman. Experimental characterization of jet fuels under engine relevant conditions - Part 2: Insights on optimization approach for surrogate formulation. To appear in Fuel, 2018.
• Kang, D., D. Kim, K. H. Yoo, A. Violi, A. Boehman. The effect of molecular structures of alkylbenzenes on ignition characteristics of binary n-heptane blends. To appear in Proceedings of the Combustion Institute, 2019.

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