Comparison of Flame Propagation Statistics Extracted from Direct Numerical Simulation Based on Simple and Detailed Chemistry—Part 1: Fundamental Flame Turbulence Interaction

Felix Benjamin Keil,Marvin Amzehnhoff,Umair Ahmed,Nilanjan Chakraborty,Markus Klein

doi:10.3390/en14175548

Felix Benjamin Keil, Marvin Amzehnhoff + Show 3 more

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https://doi.org/10.3390/en14175548

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Abstract

In the present study, flame propagation statistics from turbulent statistically planar premixed flames obtained from simple and detailed chemistry, three-dimensional Direct Numerical Simulations, were evaluated and compared to each other. To this end, a new database was established encompassing five different conditions on the turbulent premixed combustion regime diagram, using nearly identical numerical methods and the same initial and boundary conditions. A detailed discussion of the advantages and limitations of both approaches is provided, including the difference in carbon footprint for establishing the database. It is shown that displacement speed statistics and their interrelation with curvature and tangential strain rate are in very good qualitative and reasonably good quantitative agreement between simple and detailed chemistry Direct Numerical Simulations. Hence, it is concluded that simple chemistry simulations should retain their importance for future combustion research, and the environmental impact of high-performance computing methods should be carefully chosen in relation to the goals to be achieved.

Highlights

Achieving emission targets requires an approach that is available to all technologies that might at least be required during the transition of an energy system
Assuming that Navier–Stokes equations accurately describe fluid flows, the term Direct NumericalSimulation (DNS) for single-phase flows generally refers to a computationally large-scale simulation that resolves all relevant temporal and spatial scales of turbulence. Such assumptions cannot be maintained for turbulent combustion, where additional constitutive models are required to represent chemical kinetics, molecular transport, and thermochemical properties
While the focus of this work was the comparison of flame propagation statistics from SC and DC DNS of statistically planar turbulent premixed flames, based on the same computational setup and using the same numerical schemes, an extensive discussion of the physical mechanism responsible for the observed behavior can be found in Refs. [51,52]

Summary

Introduction

Achieving emission targets requires an approach that is available to all technologies that might at least be required during the transition of an energy system. Assuming that Navier–Stokes equations accurately describe (turbulent) fluid flows, the term DNS for single-phase flows generally refers to a computationally large-scale simulation that resolves all relevant temporal and spatial scales of turbulence Such assumptions cannot be maintained for turbulent combustion, where additional constitutive models are required to represent chemical kinetics, molecular transport, and thermochemical properties. There is a variety of models representing a comparable level of fidelity, associated with a largely different computational cost but with a certain uncertainty remaining, even for the most complex models Another form of simplification of this multiscale problem concerns the dimensionality in space and two-dimensional simulations might become necessary to allow for a higher degree of complexity in terms of chemistry [8] or for conducting parametric variations. Combustion DNS using detailed chemistry requires dozens of millions of CPU hours and generates hundreds of Terabytes (TBs) of data [3]

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