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Abstract
An extended database on blowout velocities of inert-diluted methane, propane, and hydrogen jet flames in the turbulent regime was experimentally established and used to examine and verify existing theories of blowout velocity estimation. Helium, argon, nitrogen, and carbon dioxide were used as the inert diluents to generate different initial properties at the jet exit. The theories of blowout velocity estimation by Kalghatgi (Combust. Sci. Technol., vol. 26, pp. 233–239, 1981) and Broadwell et al. (Proc. Combust. Instit., vol. 20, pp. 303–310, 1984) in the highly diluted regime were carefully examined using jet flames of different fuels diluted with inerts of different gas properties. The results showed that among the theories the blowout velocity estimation of Kalghatgi is more reliable in the extended region. On the other hand, the blowout velocity estimation of Broadwell et al. can do as well after proper modification by including the Reynolds number effect Re f. Based on the experimental results, modifications to the theories are proposed to accommodate for the deviation when they are used in the diluted regime. In addition, different from laminar jet flames, diffusive properties in terms of mass and thermal diffusivities are not the dominant parameters of blowout velocity in turbulent jet flames.
The financial support by National Science Council, ROC, through projects NSC90-2212-E-006-120 and NSC91-2212-E-006-039 are gratefully acknowledged.