Statistical analysis of electrostatic spark ignition of lean H₂/O₂/Ar mixtures
The concept of minimum ignition energy (MIE) has traditionally formed the basis for studying ignition hazards of fuels. However, the viewpoint of ignition as a statistical phenomenon appears to be more consistent with the inherent variability in engineering test data. We have developed a very low-energy capacitive spark ignition system to produce short sparks with fixed lengths of 1–2 mm, and the ignition system is used to perform spark ignition tests using a range of spark energies in lean hydrogen–oxygen–argon test mixtures used in aviation safety testing. The test results are analyzed using statistical tools to obtain probability distributions for ignition versus spark energy. A second low-energy spark ignition system was also developed to generate longer sparks with varying lengths up to 10 mm. A second set of ignition tests is performed in one of the test mixtures using a range of spark energies and spark lengths. The results are analyzed to obtain a probability distribution for ignition versus the spark energy per unit spark length. Preliminary results show that a single threshold MIE value does not exist, but rather that ignition is statistical in nature and highly dependent on mixture composition and spark length.
© 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. Selected to be published in a special issue of the International Journal of Hydrogen Energy dedicated to the 3rd International Conference on Hydrogen Safety. Received 21 January 2010. Received in revised form 15 May 2010. Accepted 15 May 2010. Available online 29 June 2010. This work was carried out in the Explosion Dynamics Laboratory of the California Institute of Technology and was supported by The Boeing Company through a Strategic Research and Development Relationship Agreement CT-BA-GTA-1. Thanks also to Stephanie Coronel for her work on the long spark ignition system.
Accepted Version - ijhe10_SBane_revised.pdf