United States Department of Transportation
i
Compression Ratio and Catalyst Aging Effects on Aqueous Ethanol Ignition (Year 2): Part 2 Catalyst Aging and Effects of Water on Ignition
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2009-09-01
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[PDF-2.06 MB]
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TRIS Online Accession Number:01206851
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Edition:Final Report: August 2008 - September 2009
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Abstract:A tubular plug-flow reactor under low Reynolds Numbers Re flow regimes, along with a 127 μm diameter coiled platinum (Pt) wire, were used to study catalytic surface reactions of nonflammable, fuel-lean mixtures of propane, oxygen, and water vapor diluted with nitrogen. The average wire temperature at ignition, the power required to initiate surface reactions, and the power generated from surface reactions were calculated from experimental data. Ignition temperatures varied from 450 to 540 K +/- 1 K and heat generation flux varied from 6 to 11.2 W/cm² depending on the fuel, oxygen and water content. Less than 6 W/cm² electrical flux to the wire was required to initiate surface reactions. Aging effects were observed. Unseasoned wires had to be heated to a higher temperature before surface reactions occurred. Grain growth was observed in seasoned wires. Eventually, catalyst performance suffered and deposits were seen at grain edges. Water vapor affected the combustion process, but not as much as was expected at the fuel:water ratio used (maximum 70:30 propane:water molar ratio). The ignition temperatures of wet experiments increased by no more than 10 K. Water had little effect on the heat generated due to surface reactions with at most ~3% difference between dry and wet experiments. The finite volume modeling program Fluent® was used to predict the average wire temperature as a function of power input to the wire in air cross-flow. These results were within ~25 K of the values calculated from experimental data.
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