Several representative research areas pursued at CRFL are detailed in the following. Advancements coming out of these studies would improve the current understanding of reacting flows and the computational modeling of practical combustion systems.
Inter-scale turbulence chemistry dynamics with reduced basis representations
The longer term objective of this project is to explore the potential of employing new reduced basis representations within current state-of-the-art Large-Eddy Simulation (LES) frameworks to more accurately predict important resolved-scale dynamics associated with flame-turbulence interactions in premixed turbulent combustion. Our aim is not to develop a new simulation method with a complete set of new basis functions, but rather to develop new modeling elements embedded within current LES frameworks to capture dynamically dominant subgrid-resolved-scale interactions necessary for accurate prediction of resolved-scale premixed turbulent combustion dynamics. The analyses will derive from a series of numerical experiments designed to capture essential flame-turbulence dynamics in all premixed turbulent combustion regimes. The anticipated outcomes will include a library of reduced basis functions to incorporate as new modeling elements to capture potentially important dynamics currently missing in LES.
This research focuses on the dynamics surrounding flame front dynamics in fully turbulent high Reynolds number combustion, with general applicability to a wide range of technologies including aircraft combustors and gas turbines. This approach has the potential to initiate new directions in analysis and LES modeling strategies for broad application to non-equilibrium turbulent flow dynamics outside the classical cascade description.
Sponsored by the U.S. Air Force Office of Scientific Research
Development of yield-based sooting tendency modeling to enable advanced combustion fuel
The goal of this project is to accelerate the introduction of advanced combustion fuels and engines by developing fundamental knowledge that will enable them to be implemented while reducing soot particulate emissions. Given the importance of soot emissions from engines, projects focused on ameliorating them are underway at National Renewable Energy Laboratory (NREL), Sandia National Laboratories, Lawrence Livermore National Laboratory (LLNL), and other Department of Energy (DoE) facilities; this project seeks to complement those efforts through university-level research. Specifically, we will determine sooting tendencies for a large number of promising biomass-derived fuels through computations, then use the results to identify the fuel properties that maximize engine performance in terms of low emissions, select the biomass-derived fuels that have the best values of these properties, and improve Computational Fluid Dynamics (CFD) simulations so that the full value opportunity of advanced fuels in reducing particulate emissions can be realized.
Sponsored by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy
Accurate prediction of soot emission and morphology in fuel-flexible combustors
Due to the high sensitivity of the soot formation process to the fuel chemistry, soot particles generated from the combustion of alternative and traditional fuels have significantly different characteristics. In order to mitigate soot formation from next-generation combustors and advance public health and environmental quality, this project aims to fill the gap in the present understanding and modeling of soot formation in complex flow systems by bridging several high-fidelity computational and experimental methodologies over a wide range of time and length scales. The outcome of this research effort is expected to be a major leap in the development of predictive capabilities for the mass, size distribution, chemical makeup, and morphology of soot generated from the combustion of alternative fuels. These soot characteristics are expected to be included in future emission regulations. The fundamental understanding and predictive capabilities developed in this research will enable improved engine and combustor design to mitigate soot formation, and therefore advance public health and environmental quality.
Sponsored by the Penn State Institutes of Energy and Environment
Non-equilibrium chemistry-turbulence interaction
Energy conversion devices, such as gas turbines, reciprocating engines, solid rockets, and furnaces, are responsible for the release of various pollutants, specifically nitrogen oxides, carbon monoxide, and aerosol particulates. Describing the formation and evolution of these pollutants is extremely challenging, as they all react slowly with their environment, leading to locally non-equilibrium reaction-diffusion systems. However, the interactions between turbulent unsteadiness and pollutant formation are not well understood. Direct Numerical Simulations (DNS) of turbulent reacting flows are currently performed, with specific attention paid to the inception of large aromatic molecules and their chemical derivatives, to characterize the effects of non-equilibrium chemistry on soot formation. Such analysis will also shed lights on possible means for the systematic reduction of aromatic chemistry. The same methodology will be extended to investigate the evolution of other pollutants with slow chemistry. Additionally, more fundamental concerns can be addressed, such as those associated with the effects of temporal turbulent intermittency on the formation of slow-chemistry molecules.