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Fuel Combustion

Mixture Preparation Effects on Distributed Combustion for Gas Turbine Applications

[+] Author and Article Information
Ahmed E. E. Khalil

Department of Mechanical Engineering,  University of Maryland, College Park, MD 20742aekhalil@umd.edu

Ashwani K. Gupta

Department of Mechanical Engineering,  University of Maryland, College Park, MD 20742akgupta@umd.edu

Kenneth M. Bryden

Department of Mechanical Engineering,  Iowa State University, Ames, IA 50011kmbryden@iastate.edu

Sang C. Lee

Department of Nano Science and Engineering,  Kyungnam University, 630-701, Masan, Republic of South Koreasanglee@kyungnam.ac.kr

J. Energy Resour. Technol 134(3), 032201 (May 07, 2012) (7 pages) doi:10.1115/1.4006481 History: Received January 29, 2012; Accepted March 21, 2012; Published May 07, 2012; Online May 07, 2012

Distributed combustion is now known to provide significantly improved performance of gas turbine combustors. Key features of distributed combustion include uniform thermal field in the entire combustion chamber for significantly improved pattern factor and avoidance of hot-spot regions that promote thermal NOx emissions, negligible emissions of hydrocarbons and soot, low noise, and reduced air cooling requirements for turbine blades. Distributed combustion requires controlled mixing between the injected air, fuel, and hot reactive gasses from within the combustor prior to mixture ignition. The mixing process impacts spontaneous ignition of the mixture to result in improved distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed, or nonpremixed modes of combustor operation with sufficient entrainment of hot and active species present in the combustion zone and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here to further explore the beneficial aspects of such combustion under relevant gas turbine combustion conditions. The near term goal is to develop a high intensity combustor with ultralow emissions of NOx and CO, and a much improved pattern factor and eventual goal of near zero emission combustor. Experimental results are reported for a cylindrical geometry combustor for different modes of fuel injection with emphasis on the resulting pollutants emission. In all the cases, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra low NOx emissions were found for both the premixed and nonpremixed combustion modes for the geometries investigated here. Results showed very low levels of NO (∼10 ppm) and CO (∼21 ppm) emissions under nonpremixed mode of combustion with air preheats at an equivalence ratio of 0.6 and a moderate heat release intensity of 27 MW/m3 -atm. Results are also reported on lean stability limits and OH* chemiluminescence under different fuel injection scenarios for determining the extent of distribution combustion conditions. Numerical simulations have also been performed to help develop an understanding of the mixing process for better understanding of ignition and combustion.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

A schematic diagram of different fuel introduction scenarios, end cross-sectional view at middle location of the combustor

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Figure 2

A schematic diagram for the combustor, longitudinal view along the cylinder axis and a 3D model

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Figure 3

High intensity CDC cylindrical combustor test rig with optical access (left) and product gas exit (right)

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Figure 4

NO emission for different injection arrangements

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Figure 5

CO emission for different injection arrangements

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Figure 6

OH* chemiluminescence intensity distribution for different injection arrangements

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Figure 7

Temperature distribution at the air/fuel injection plane for the different cases

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Figure 8

Methane mass fraction distribution at the air/fuel injection plane for the different cases

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