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Research Papers: Fuel Combustion

Modeling of Entropy Generation in Turbulent Premixed Flames for Reynolds Averaged Navier–Stokes Simulations: A Direct Numerical Simulation Analysis

[+] Author and Article Information
Nilanjan Chakraborty

School of Mechanical and Systems Engineering,
Newcastle University,
Claremont Road,
Newcastle-Upon-Tyne,
NE1 7RU, UK
e-mail: nilanjan.chakraborty@ncl.ac.uk

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received March 31, 2014; final manuscript received September 9, 2014; published online October 21, 2014. Assoc. Editor: Reza H. Sheikhi.

J. Energy Resour. Technol 137(3), 032201 (Oct 21, 2014) (13 pages) Paper No: JERT-14-1093; doi: 10.1115/1.4028693 History: Received March 31, 2014; Revised September 09, 2014

The modeling of the mean entropy generation rate S·"'gen¯ due to combined actions of viscous dissipation, irreversible chemical reaction, thermal conduction and mass diffusion (i.e., T¯1,T¯2,T¯3, and T¯4) in the context of Reynolds averaged Navier–Stokes (RANS) simulations has been analyzed in detail based on a direct numerical simulation (DNS) database with a range of different values of heat release parameter τ, global Lewis number Le, and turbulent Reynolds number Ret spanning both the corrugated flamelets (CF) and thin reaction zones (TRZ) regimes of premixed turbulent combustion. It has been found that the entropy generation due to viscous dissipation T¯1 remains negligible in comparison to the other mechanisms of entropy generation (i.e., T¯2,T¯3, and T¯4) within the flame for all cases considered here. A detailed scaling analysis has been used to explain the relative contributions of , and T¯4 on the overall volumetric entropy generation rate S·"'gen¯ in turbulent premixed flames. This scaling analysis is further utilized to propose models for T¯1,T¯2,T¯3, and T¯4 in the context of RANS simulations. It has been demonstrated that the new proposed models satisfactorily predict T¯1,T¯2,T¯3, and T¯4 for all cases considered here. The accuracies of the models for T¯1,T¯2,T¯3, and T¯4 have been demonstrated to be closely linked to the modeling of dissipation rate of turbulent kinetic energy and scalar dissipation rates (SDRs) in turbulent premixed flames.

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Figures

Grahic Jump Location
Fig. 2

Variations of T1¯×αT/(ρ0cpSL2) (solid line) and res(T1¯)×αT/(ρ0cpSL2) (broken line) with c˜ across the flame brush along with the prediction of Eq. (8c) (model) (line with circles) for cases: (a) A, (b) B, (c) C, (d) E, (e) F, (f) G, (g) H, and (h) L

Grahic Jump Location
Fig. 5

Variations of T4¯×αT/(ρ0cpSL2) (solid line) and res(T4¯)×αT/(ρ0cpSL2) (broken line) with c˜ across the flame brush along with the prediction of Eq. (15) (model) (line with circles) for cases: (a) A, (b) B, (c) C, (d) E, (e) F, (f) G, (g) H, and (h) L

Grahic Jump Location
Fig. 1

Variations of T1¯×αT/(ρ0cpSL2), (broken line), T2¯×αT/(ρ0cpSL2) (solid line), T3¯×αT/(ρ0cpSL2) (line with + symbol), T4¯×αT/(ρ0cpSL2) (line with circles), and S·¯gen×αT/(ρ0cpSL2) (line with stars) with c˜ across the flame brush for cases: (a) A, (b) B, (c) C, (d) E, (e) F, (f) G, (g) H, and (h) L

Grahic Jump Location
Fig. 4

Variations of T3¯×αT/(ρ0cpSL2) (solid line) and res(T3¯)×αT/(ρ0cpSL2) (broken line) with c˜ across the flame brush along with the prediction of Eq. (13) (Model) (line with circles) for cases: (a) A, (b) B, (c) C, (d) E, (e) F, (f) G, (g) H, and (h) L

Grahic Jump Location
Fig. 3

Variations of T2¯×αT/(ρ0cpSL2) (solid line) and 0.1×res(T2¯)×αT/(ρ0cpSL2) (broken line) with c˜ across the flame brush along with the prediction of Eq. (10) (line with circles) and Eq. (12) (line with stars) for cases: (a) A, (b) B, (c) C, (d) E, (e) F, (f) G, (g) H, and (h) L

Grahic Jump Location
Fig. 6

Variations of S·"' gen¯×αT/(ρ0cpSL2)=(T1¯+T2¯+T3¯+T4¯)×αT/(ρ0cpSL2) (solid line) with c˜ across the flame brush along with the predictions of Eqs. (8c), (12), (13), and (15) (model) (broken line) for cases: (a) A, (b) B, (c) C, (d) E, (e) F, (f) G, (g) H, and (h) L

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