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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Experimental and Computational Analyses of Methane and Hydrogen Mixing in a Model Premixer

[+] Author and Article Information
Amin Akbari, Scott Hill, Vincent McDonell, Scott Samuelsen

UCI Combustion Laboratory, University of California, Irvine, CA 92697-3550

J. Eng. Gas Turbines Power 133(10), 101503 (Apr 28, 2011) (11 pages) doi:10.1115/1.4002808 History: Received May 26, 2010; Revised June 29, 2010; Published April 28, 2011; Online April 28, 2011

The mixing of fuel and air in combustion systems plays a key role in overall operability and emissions performance. Such systems are also being looked to for operation on a wide array of potential fuel types, including those derived from renewable sources such as biomass or agricultural waste. The optimization of premixers for such systems is greatly enhanced if efficient design tools can be utilized. The increased capability of computational systems has allowed tools such as computational fluid dynamics to be regularly used for such purpose. However, to be applied with confidence, validation is required. In the present work, a systematic evaluation of fuel mixing in a specific geometry, which entails cross flow fuel injection into axial nonswirling air streams has been carried out for methane and hydrogen. Fuel concentration is measured at different planes downstream of the point of injection. In parallel, different computational fluid dynamics approaches are used to predict the concentration fields resulting from the mixing of fuel and air. Different steady turbulence models including variants of Reynolds averaged Navier–Stokes (RANS) have been applied. In addition, unsteady RANS and large eddy simulation are used. To accomplish mass transport with any of the RANS approaches, the concept of the turbulent Schmidt number is generally used. As a result, the sensitivity of the RANS simulations to different turbulent Schmidt number values is also examined. In general, the results show that the Reynolds stress model, with use of an appropriate turbulent Schmidt number for the fuel used, provides the best agreement with the measured values of the variation in fuel distribution over a given plane in a relatively time efficient manner. It is also found that, for a fixed momentum flux ratio, both hydrogen and methane penetrate and disperse in a similar manner for the flow field studied despite their significant differences in density and diffusivity.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The known vortical structures of the jet in the cross flow (8-9)

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Figure 2

Premixer assembly in traversable test stand

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Figure 3

Cross section of premixer assembly

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Figure 4

Methane measurement locations. Areas shaded gray represent an area of increased measurement density.

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Figure 5

Hydrogen measurement locations. Areas shaded gray represent an area of increased measurement density.

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Figure 6

Normalized axial velocity comparison between experimental and numerical result for RSM Sct=0.7

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Figure 7

Contours of methane mole-fraction in the plane of Y/D=0 for k-ε and RSM simulations

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Figure 8

Measured methane mole-fraction distribution at three downstream planes

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Figure 9

Comparison of experiment and simulations at Z/D=0.3125

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Figure 10

General qualitative comparison at Z/D=0.3125

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Figure 11

The effect of Sct in k-ε and RSM models

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Figure 12

Comparison between different turbulent models and experiment at Z/D=0.9375

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Figure 13

General qualitative comparison at Z/D=0.9375

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Figure 14

The effect of Sct in k-ε and RSM models

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Figure 15

Comparison between different turbulent models and experiment at Z/D=1.875

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Figure 16

General qualitative comparisons at Z/D=1.875

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Figure 17

The effect of Sct in k-ε and RSM models

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Figure 18

Normalized averaged fuel/air differences between experiment and numerical cases over the planes (methane)

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Figure 19

Comparison between different turbulent models and experiment at Z/D=0.3125

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Figure 20

The effect of Sct in k-ε and RSM models

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Figure 21

Comparison between different turbulent models and experiment at Z/D=0.9375

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Figure 22

The effect of Sct in k-ε and RSM models

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Figure 23

Comparison between different turbulent models and experiment at Z/D=1.875

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Figure 24

The effect of Sct in k-ε and RSM models

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Figure 25

Normalized averaged fuel/air differences between experiment and numerical cases over the planes (hydrogen)

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