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Catalytic Ignition of Ethanol-Oxygen-Nitrogen Mixtures Over 90% Platinum - 10% Rhodium in Comparison With Pure Platinum

[+] Author Affiliations
David Mehaffey, Judi Steciak, Ralph Budwig

University of Idaho, Boise, ID

Steve Beyerlein

University of Idaho, Moscow, ID

Paper No. IMECE2011-63931, pp. 1389-1398; 10 pages
doi:10.1115/IMECE2011-63931
From:
  • ASME 2011 International Mechanical Engineering Congress and Exposition
  • Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B
  • Denver, Colorado, USA, November 11–17, 2011
  • Conference Sponsors: ASME
  • ISBN: 978-0-7918-5490-7
  • Copyright © 2011 by ASME

abstract

Prior research of the catalytic ignition of renewable transportation fuels was conducted with pure platinum (Pt), an oxidation catalyst with mechanical properties that change at the temperatures expected in internal combustion engines. This study was undertaken to compare and contrast the ability of grain-hardened 90% platinum - 10% rhodium (Pt-Rh) to serve as an ignition catalyst. The temperature required to initiate surface reactions and the rate of heat generated from the reactions of ethanol-oxygen-nitrogen mixtures on Pt-Rh and Pt were obtained using a microcalorimeter. Catalyst wires were exposed to reacting flows in a plug-flow reactor and heated though electrical resistance until surface reactions occurred. The process was repeated for fixed fuel molar percentages of ethanol ranging from 1% to 3% and fuel-oxygen equivalence ratios (Φ) ranging from 0.2 to 1.0 at a constant total volumetric flow rate of 5 L/min, thus testing the effect of both the absolute and relative fuel content. Because of its lower coefficient of thermal resistance, Pt-Rh initiated surface reactions in fuel-oxygen mixtures at temperatures about 45 K higher than pure Pt; 3% ethanol mixtures ignited at an average ignition temperature of 512 K on Pt-Rh with very little variation with Φ while those on Pt ignited at temperatures ranging from a low of 450 K (Φ = 0.5) to a high of 473 K (Φ = 1.0), suggesting fuel-first coverage of the surface for these conditions. Also at 3% ethanol, reactions on Pt-Rh generated heat at an average rate of 5.5 W/cm2 while those on pure Pt generated 19.6 W/cm2 . Pt-Rh did not exhibit significant seasoning at the conditions tested whereas Pt seasoned over time and became more reactive (initiating surface reactions at lower temperatures than an unseasoned surface), a phenomenon observed in prior research. This data will aid in the design and understanding of catalytic igniters used with alternative transportation fuels in internal combustion engines.

Copyright © 2011 by ASME

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