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Proceedings Paper

Laser-induced ignition characteristics of methane- and hydrogen-air mixtures at high pressures
Author(s): Herbert Kopecek; M. Weinrotter; S. Charareh; F. Winter; Ernst Wintner
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Paper Abstract

A Nd:YAG laser was employed to ignite methane- and hydrogen-air mixtures to investigate relevant parameters of laser ignition. The lean side ignition limit of methane was found to be at air/fuel-equivalence ratios (λ) of 2.4 applying a laser pulse energy of 50 mJ. It has to be mentioned, however, that above λ = 2.2 only slowest combustions causing weak pressure rises could be observed. Successful ignitions of hydrogen-air mixtures were achieved up to λ = 8 but it was not possible to examine the lean side limit due to weakest pressure rises far below detection limits for λ >8. Despite much lower values of minimum ignition energy for reported hydrogen-air mixtures in the literature, the minimum laser pulse energies examined for ignition are of the same magnitude as for ignition of rich methane-air mixtures lying around 5 mJ. Minimum pulse energy needed for ignition was decreasing with increasing pressure for hydrogen-air mixtures showing the same trend as in case of methane. The ignition delay time for hydrogen at λ = 2.0 could be observed as ~7 ms being 40 times shorter compared to methane at the same air/fuel ratio. Unfavorable transmission losses of laser energy were observed for methane/air mixtures below λ = 2.1 demanding optimized focusing optics and temporal pulse shaping for future laser ignition systems.

Paper Details

Date Published: 15 July 2004
PDF: 8 pages
Proc. SPIE 5506, Nonresonant Laser-Matter Interaction (NLMI-11), (15 July 2004); doi: 10.1117/12.580026
Show Author Affiliations
Herbert Kopecek, Technische Univ. Wien (Austria)
M. Weinrotter, Technische Univ. Wien (Austria)
S. Charareh, Technische Univ. Wien (Austria)
F. Winter, Technische Univ. Wien (Austria)
Ernst Wintner, Technische Univ. Wien (Austria)

Published in SPIE Proceedings Vol. 5506:
Nonresonant Laser-Matter Interaction (NLMI-11)
Mikhail N. Libenson, Editor(s)

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