Advanced radiation models to enable direct comparisons between computed and measured temperatures and compositions in laminar and turbulent flames

1604446 - Haworth

Combustion will continue to play a central role in propulsion and power generation for the foreseeable future. This includes engines for light- and heavy-duty road vehicles (cars and trucks). Aggressive fuel economy and emissions targets have been established to simultaneously reduce energy consumption and pollutant emissions, including greenhouse-gas emissions. At the same time, alternatives to petroleum-derived fuels (e.g., biofuels) are being introduced to reduce the carbon footprint of combustion-based energy systems. Predictive mathematical/computational tools are urgently needed so that engineers can optimize future engines and other combustion systems for maximum performance with minimum fuel consumption and emissions, while enabling the introduction of future sustainable fuels. These tools must include accurate representations of the key underlying physical processes. Radiative heat transfer is important in combustion systems, by virtue of their high temperatures, but has received relatively little attention to date because of its extreme complexity. This project will develop advanced radiation models that will be an important part of a new generation of predictive mathematical/computational tools, which in turn will enable the introduction of a new generation of high-efficiency, low-emissions, alternative-fuel vehicles.

High-resolution optical diagnostics and numerical simulations are increasingly being brought to bear to provide fundamental insight into the underlying physical processes in engines and other combustion systems, and to inform the development of reduced-order models that can be used for device and system design. However, the connection between experiment and numerical simulation/modeling remains somewhat primitive. For example, extensive simplification and modeling are required to provide quantitative values of temperature and equivalence-ratio distributions from measured radiative intensities for nonintrusive optical diagnostics techniques. At the same time, increasingly sophisticated models for spectral radiative heat transfer are being developed for computational fluid dynamics (CFD)-based simulations of turbulent reacting flows, and these models provide an ideal starting point for directly computing the radiative intensity signals that correspond to various optical diagnostics techniques. By the end of this project, two important diagnostic techniques will have been developed/advanced for applications to harsh high-pressure combustion environments such as those in piston engines, simulation models will have been extended to directly compute radiative intensity signals corresponding to these diagnostic techniques, and a proof-of-concept of the advantages of making direct comparisons between computed and measured radiative intensities (versus derived quantities, such as temperature and equivalence ratio) will have been completed.