RANS vs LES CFD for Gas-Fired Combustion Equipment

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Title RANS vs LES CFD for Gas-Fired Combustion Equipment
Creator Smith, J.D.
Contributor Adams, B.R., Jackson, R., Smith, Z., Suo-Antilla, A., Smith, S., Allen, D.
Date 2017-12-12
Description Paper from the AFRC 2017 conference titled RANS vs LES CFD for Gas-Fired Combustion Equipment
Abstract High temperature gas-fired furnaces and gas flares are widely used in the chemical and petrochemical industries. The US EPA estimates that approximately 3,200 process heaters are used in the U.S. petroleum refining industry and 1,400 fired heaters are used in the U.S. chemical process industry [1]. NASA/NOAA estimated that in 2012 there were approximately 7,500 gas flares worldwide burning approximately 143 billion cubic meters (BCM) natural gas [2]. Past developments in combustion diagnostics, computational resources and software development have greatly expanded the application of computational fluid dynamics (CFD) tools for combustion analysis in the process industries. Effective use of CFD can help improve combustion efficiency, enhance heat transfer efficiency, reduce pollutant formation, and establish better safety practices. CFD has been used to develop insights into unique combustion phenomena (i.e., turbulent mixing effect on reacting flows), evaluate new and modified equipment design (i.e., improved low-NOx burners), assess operations (i.e., turn-down conditions), guide experimental work (i.e., reduce costs of full scale testing), and calculate pollutant control impacts (i.e., flare burner tip spacing on soot formation). However, not all CFD tools equally simulate all combustion processes accurately. Successful application of CFD requires an understanding of which tools work best for which applications.; This paper will compare Large Eddy Simulations (LES) to Reynolds-averaged Navier-Stokes (RANS) based CFD applied to several combustion applications to illustrate issues to consider when applying CFD to solve industrial problems. This paper will review the basis, strengths and limitations of these two approaches and provide recommendations on when each is most applicable. An LES based CFD tool simulates turbulent reaction chemistry coupled with radiative transport in buoyancy driven flames (i.e., gas flares) and the impact large flames have on surrounding objects (i.e., wind fence, process equipment, etc.). Validation work comparing LES based CFD simulations to RANS based simulations of a multi-point ground flare test will be shown to illustrate each approach for this application. Recent LES based CFD analysis of transient burner operation will also be discussed. Results of this work will be used to review and discuss how CFD codes may help assess various risk scenarios including wind, % flame coverage, and thermal fatigue for a given geometry. Several examples will be used to illustrate applications where each technology has worked and failed.
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Format application/pdf
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Metadata Cataloger Catrina Wilson
ARK ark:/87278/s6c57wv8
Setname uu_afrc
Date Created 2018-12-10
Date Modified 2018-12-10
ID 1388811
Reference URL https://collections.lib.utah.edu/ark:/87278/s6c57wv8