IngentaConnect Transported scalar PDF calculations of autoignition of a hydrogen...

Authors: Lee, C. W.¹; Mastorakos, E.¹

Source: Combustion Theory and Modelling, Volume 12, Number 6, December 2008 , pp. 1153-1178(26)

Abstract:

The joint scalar PDF method, as implemented in FLUENT, was used to simulate the autoignition of a jet of hydrogen in a turbulent co-flow of heated air. While the autoignition phenomenon is intermittent in the experiment, ensemble-averaged data on the effect of the flow on ignition length are available, which enables us to compare them with the steady state calculations.Results of sensitivity tests showed that the choice of chemical mechanism affects the calculation more than the mixing model and model constants. Further calculations for different initial conditions (i.e. temperature and velocity of the jet Tjet and Ujet and the co-flow Tair and Uair) have been done using a set of parameters selected after the sensitivity study. Scatter plots and conditional scalar profiles confirmed that the ignition is always initiated in lean mixture fractions. The ignition length was predicted with good accuracy for the case of Ujet>Uair but not so well for the case of Ujet≍Uair. For the equal velocity case, increasing the velocity resulted in delayed autoignition time (defined as the ignition length divided by the mean velocity), in agreement with the experimental trend. The results give credence to the use of the joint scalar PDF method for autoignition in non-premixed flows.

Keywords: autoignition; hydrogen jet; non-premixed flame; PDF method; CFD

Document Type: Research article

DOI: 10.1080/13647830802283095

Affiliations: 1: Hopkinson Laboratory, Engineering Department, University of Cambridge, Trumpington Street, UK

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Transported scalar PDF calculations of autoignition of a hydrogen jet in a heated turbulent co-flow