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Research Papers: Fuel Combustion

Evaluation of the Accuracy of Selected Syngas Chemical Mechanisms

[+] Author and Article Information
Fahad M. Alzahrani

Department of Mechanical Engineering,
KFUPM,
Dhahran 31261, Saudi Arabia
e-mail: fahadmz@kfupm.edu.sa

Yinka S. Sanusi

Department of Mechanical Engineering,
KFUPM,
Dhahran 31261, Saudi Arabia
e-mail: sanusi@kfupm.edu.sa

Konstantina Vogiatzaki

Assistant Professor
Department of Mechanical Engineering,
City University of London,
London EC1V 0HB, UK
e-mail: Konstantina.Vogiatzaki.2@city.ac.uk

Ahmed F. Ghoniem

Ronald C. Crane (1972) Professor
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: ghoniem@mit.edu

Mohamed A. Habib

Professor
Department of Mechanical Engineering,
KFUPM,
Dhahran 31261, Saudi Arabia
e-mail: mahabib@kfupm.edu.sa

Esmail M. A. Mokheimer

Professor
Department of Mechanical Engineering,
KFUPM,
Dhahran 31261, Saudi Arabia
e-mail: esmailm@kfupm.edu.sa

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received December 27, 2014; final manuscript received February 5, 2015; published online March 12, 2015. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 137(4), 042201 (Jul 01, 2015) (13 pages) Paper No: JERT-14-1426; doi: 10.1115/1.4029860 History: Received December 27, 2014; Revised February 05, 2015; Online March 12, 2015

The implementation of reduced syngas combustion mechanisms in numerical combustion studies has become inevitable in order to reduce the computational cost without compromising the predictions' accuracy. In this regard, the present study evaluates the predictive capabilities of selected detailed, reduced, and global syngas chemical mechanisms by comparing the numerical results with experimental laminar flame speed (LFS) values of lean premixed (LPM) syngas flames. The comparisons are carried out at varying equivalence ratios, syngas compositions, operating pressures, and preheat temperatures to represent a range of operating conditions of modern fuel flexible combustion systems. NOx emissions predicted by the detailed mechanism, GRI-Mech. 3.0, are also used to study the accuracy of the selected mechanisms under these operating conditions. Moreover, the selected mechanisms' accuracy in predicting the laminar flame thickness (LFT), species concentrations of the reactants, and OH profiles at different equivalence ratios and syngas compositions are investigated as well. The LFS is generally observed to increase with increasing equivalence ratio, hydrogen content in the syngas, and preheat temperature, while it is decreased with increasing operating pressure. This trend is followed by all mechanisms understudy. The global mechanisms of Watanabe–Otaka and Jones–Lindstedt for syngas are consistently observed to over-predict and under-predict the LFS up to an average of 60% and 80%, respectively. The reduced mechanism of Slavinskaya has an average error of less than 20%, which is comparable to the average error of the GRI-Mech. 3.0. It however over-predicts the flame thickness by up to 30% when compared to GRI-Mech. 3.0. The NO prediction by Li mechanism and the reduced mechanisms are observed to be within 10% prediction range of the GRI-Mech. 3.0 at intermediate equivalence ratio (φ=0.74) up to stoichiometry. Moving toward more lean conditions, there is significant difference between the GRI-Mech. 3.0 NO prediction and those of the reduced mechanisms due to relative importance of the prompt NOx at lower temperature compared to thermal NOx that is only accounted for by the GRI-Mech. 3.0.

Copyright © 2015 by ASME
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References

Figures

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Fig. 2

Experimental (symbols) and predicted (lines) LFSs at varying equivalence ratio for (a) H2/CO = 5/95 (experimental from Ref. [25]) and (b) H2/CO = 50/50 (experimental from Ref. [43]): p = 1 atm and Tu = 300 K

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Fig. 3

Experimental (symbols) and predicted (lines) LFSs for varying syngas composition at (a) φ = 0.6 and (b) φ = 0.8. Experimental from Ref. [25]: p = 1 atm and Tu = 300 K.

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Fig. 4

Predicted LFSs for varying operating pressure at (a) φ = 0.6 and (b) φ = 0.8. Reference mechanism: GRI Mech. 3.0. H2/CO = 50/50 and Tu = 300 K.

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Fig. 5

Experimental (symbols) and predicted (lines) LFSs for varying preheat temperature at (a) φ = 0.6 and (b) φ = 0.9. Experimental from Ref. [30]: H2/CO = 50/50 and p = 1 atm.

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Fig. 6

LFS average error between experimental and calculated values for all kinetic models. Varied parameters are calculated at fixed H2/CO = 50/50, p = 1 atm, and Tu = 300 K.

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Fig. 1

LFS of pure H2 and CO fuels under lean conditions predicted by GRI mechanism: Tu = 300 K and p = 1 atm

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Fig. 8

Laminar flame structure and temperature predictions by GRI model at varying conditions for (a) H2/CO = 5/95, φ = 0.5, (b) H2/CO = 50/50, φ = 0.5, and (c) H2/CO = 50/50, φ = 0.9: p = 1 atm and Tu = 300 K

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Fig. 7

LFT predictions of all kinetic models at varying equivalence ratio for (a) 5/95 and (b) 50/50 H2/CO syngas compositions: p = 1 atm and Tu = 300 K

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Fig. 9

Flame temperature predictions by all kinetic models at varying conditions for (a) H2/CO = 5/95, φ = 0.5, (b) H2/CO = 50/50, φ = 0.5, and (c) H2/CO = 50/50, φ = 0.9: p = 1 atm and Tu = 300 K

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Fig. 10

H2 profiles predicted by all kinetic models at varying conditions for (a) H2/CO = 5/95, φ = 0.5, (b) H2/CO = 50/50, φ = 0.5, and (c) H2/CO = 50/50, φ = 0.9: p = 1 atm and Tu = 300 K

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Fig. 11

CO profiles predicted by all kinetic models at varying conditions for (a) H2/CO = 5/95, φ = 0.5, (b) H2/CO = 50/50, φ = 0.5, and (c) H2/CO = 50/50, φ = 0.9: p = 1 atm and Tu = 300 K

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Fig. 12

OH profiles predicted by the detailed and reduced kinetic models at varying conditions for (a) H2/CO = 5/95, φ = 0.5, (b) H2/CO = 50/50, φ = 0.5, and (c) H2/CO = 50/50, φ = 0.9: p = 1 atm and Tu = 300 K

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Fig. 13

NO predictions of detailed and reduced kinetic models at varying equivalence ratio for (a) 25/75, (b) 50/50, and (c) 75/25 H2/CO syngas compositions: p = 1 atm and Tu = 300 K

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Fig. 14

NO predictions of detailed and reduced kinetic models for varying syngas composition at (a) φ = 0.5 and (b) φ = 0.9: p = 1 atm and Tu = 300 K

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Fig. 15

NO predictions of detailed and reduced kinetic models for varying operating pressure at (a) φ = 0.5 and (b) φ = 0.9: H2/CO = 50/50 and Tu = 300 K

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Fig. 16

NO predictions of detailed and reduced kinetic models for varying preheat temperature at (a) φ = 0.5 and (b) φ = 0.9: H2/CO = 50/50 and p = 1 atm

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