Conditional Moment Closure for Turbulent Premixed Flames

Large Eddy Simulation of Premixed Combustion: Sensitivity to Subgrid Scale Velocity Modeling

“…The termcð1 ÀcÞ=β c comes from combined influences of flame front curvature effects induced by turbulence, chemical reaction, and molecular dissipation processes Chakraborty and Swaminathan, 2007). Although a reasonably robust value of β c ¼ 6:7 was established in past RANS calculations of various premixed flames (Ahmed and Swaminathan, 2013;Amzin and Swaminathan, 2013;Amzin et al, 2012;Kolla et al, 2009;Ruan et al, 2014;Swaminathan et al, 2012), this value cannot be used for LES because the processes influencing β c are effected by SGS turbulence. Thus, it can be evaluated dynamically as suggested by Langella et al (2015) and Gao et al (2014).…”

“…A value of 17% was used by Herrmann (2006) and 20% heat loss was assumed by Pitsch and de Lagneste (2002) and Wang et al (2011). For this study, it is taken to be 16% following Amzin et al (2012) and Kolla and Swaminathan (2010b), which gives 1950 K for the pilot temperature. These past studies showed that this uncertainty influences the temperature only close to the jet exit (x ≤ 3D), which is also confirmed here by changing this temperature over a range of about 200 K.…”

“…A small velocity of 0.2 m/s is assigned to the coflowing air to mimic the air entrainment and a 25% change to this velocity is observed to influence the LES statistics negligibly. The pilot temperature is unspecified in the experimental study and values ranging from 1785 to 2248 K were used in past studies (Amzin et al, 2012;De and Acharya, 2009;Dodoulas and Navarro-Martinez, 2013;Herrmann, 2006;Kolla and Swaminathan, 2010b;Lindstedt and Vaos, 2006;Pitsch and de Lagneste, 2002;Prasad and Gore, 1999;Salehi and Bushe, 2010;Salehi et al, 2012;Heinz, 2008, 2010;Wang et al, 2011;Yilmaz et al, 2010) suggesting that the heat loss to the pilot burner varies from 0 (De and Acharya, 2009) to 34% (Dodoulas and Navarro-Martinez, 2013;Lindstedt and Vaos, 2006). A value of 17% was used by Herrmann (2006) and 20% heat loss was assumed by Pitsch and de Lagneste (2002) and Wang et al (2011).…”

“…Three piloted stoichiometric methane-air Bunsen flames of Chen et al (1996) considered in many past RANS (Amzin et al, 2012;Herrmann, 2006;Kolla and Swaminathan, 2010b;Lindstedt and Vaos, 2006;Prasad and Gore, 1999;Salehi and Bushe, 2010;Salehi et al, 2012;Heinz, 2008, 2010) and LES (De and Acharya, 2009;Dodoulas and Navarro-Martinez, 2013;Langella et al, 2015;Pitsch and de Lagneste, 2002;Wang et al, 2011;Yilmaz et al, 2010) studies are chosen for this investigation. The reactant jet with a diameter of D = 12 mm issues into quiescent air and the flame is stabilized by laminar pilot flames of the same mixture.…”

“…The nonflamelets category includes transported PDF and conditional moment closure (CMC) methodologies. The CMC method (Klimenko and Bilger, 1999) was tested rigorously for RANS simulations of premixed flames (Amzin and Swaminathan, 2013;Amzin et al, 2012;Martin et al, 2003) but yet to be applied for LES of premixed combustion. Different PDF approaches have been used for LES of premixed combustion (Bulat et al, 2014;Dodoulas and NavarroMartinez, 2013;Rowinski and Pope, 2013).…”