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

Autoignition of Hydrogen and Air Inside a Continuous Flow Reactor With Application to Lean Premixed Combustion

[+] Author and Article Information
D. J. Beerer

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

V. G. McDonell

UCI Combustion Laboratory, University of California, Irvine, CA 92697-3550mcdonell@ucicl.uci.edu

J. Eng. Gas Turbines Power 130(5), 051507 (Jun 17, 2008) (8 pages) doi:10.1115/1.2939007 History: Received June 29, 2007; Revised April 14, 2008; Published June 17, 2008

With the need to reduce carbon emissions such as CO2, hydrogen is being examined as potential “clean” fuel for the future. One potential strategy is lean premixed combustion, where the fuel and air are allowed to mix upstream before entering the combustor, which has been proven to curb NOx formation in natural gas fired engines. However, premixing hydrogen and air may increase the risk of autoignition before the combustor, resulting in serious engine damage. A flow reactor was set up to test the ignition delay time of hydrogen and air at temperatures relevant to gas turbine engine operations to determine maximum possible mixing times. The results were then compared to past experimental work and current computer simulations. The current study observed that ignition is very sensitive to the initial conditions. The ignition delay times follow the same general trend as seen in previous flow reactor studies: ignition within hundreds of milliseconds and relatively low activation energy. An experimentally derived correlation by Peschke and Spadaccini (1985, “Determination of Autoignition and Flame Speed Characteristics of Coal Gases Having Medium Heating Values  ,” Research Project No. 2357-1, Report No. AP-4291) appears to best predict the observed ignition delay times. Homogenous gas phase kinetics simulations do not appear to describe ignition well in these intermediate temperatures. Therefore, at the moment, only the current empirical correlations should be used in predicting ignition delay at engine conditions for use in the design of gas turbine premixers. Additionally, fairly large safety factors should still be considered for any design to reduce any chance of autoignition within the premixer.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Comparison of current data with past ignition delay studies

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Figure 2

Schematic of the continuous flow reactor

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Figure 3

Velocity profile in the test section during cold flow test. Reynolds number=125,000.

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Figure 4

Fuel concentration profile in the test section during the FID test

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Figure 5

Classification of ignition events

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Figure 6

Comparison of current results with previous measurements and correlations

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Figure 7

Comparison of experimental work to homogenous simulations (mechanism by O’Conaire (30))

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Figure 8

Hydrogen-oxygen explosion limit chart with experimental test conditions identified. The shaded region represents typical gas turbine combustor inlet temperatures and pressures.



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