With advanced gas turbine combustor and internal combustion engine designs, autoignition can happen alongside flame propagation. Laminar flame speeds are required to model flame propagation. Determining laminar flame speeds using simulation assumes flames are freely propagating, an assumption that is not valid when autoignition does occur. From a CFD modeling viewpoint however, it is useful to have extrapolated laminar flame-speed values over a wide range of conditions, to allow CFD to operate smoothly and avoid discontinuities while calculating flame-propagation properties. In this work we focus on developing an approach for generating laminar flame-speed libraries under both nonigniting and autoigniting conditions. Following a test of whether autoignition occurs, laminar flame speeds are either modeled or extrapolated. The details of the approach implemented and its validation are explained. We assess the accuracy of the extrapolation employed by calculating relevant coefficients based on flame speeds from nearby operating points. Recommendations are made for the time scales to be used in determining autoignition occurrence. The method applies well in the context of complex fuels and the consideration of fuel effects in CFD simulations. The resulting generated laminar flame speed libraries can be used to determine local turbulent flame speeds in CFD to allow simultaneous simulation of flame propagation and autoignition, based on local kinetics.


Generating Laminar Flame Speed Libraries for Autoignition Conditions

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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