Premixed Swirl Combustion and Flashback Analysis with Hydrogen/Methane Mixtures

Increased interest in the combustion of hydrogen and hydrogen blends is the driving force in the research of the alternative fuels. The usage of the new hydrogen enriched fuels is unavoidably related to changes in the ame structure, burning velocity and as a consequence ame stability. Flame ashback and blow o are the important characteristics in practical application. Flame ashback problems arising due to the use of lean premixed combustion of methanehydrogen mixtures is discussed in this paper. Firstly, one of the most important ame characteristics, laminar burning velocity SL, has been calculated for CH4-H2 mixtures with di erent hydrogen content at various pressures, temperatures and equivalence ratios. Chemkin-Pro software package with Premix code has been used for that purpose. A new approximation equation, used to calculate SL of CH4-H2 mixtures having di erent hydrogen content has been compared with the experimental results and validated. The equation predicts the values of low hydrogen content mixtures quite accurately. Secondly, the ashback limits have been determined for CH4-H2 mixtures using generic swirl burner. New turbulent burning velocity determination method has been applied and tested. The experiment results have been compared with the Bunsen burner experiment results and Fluent computations. It has been found that hydrogen enriched methane ames are more prone to ashback, although the blow o limits are extended. This is clearly due to the increased burning velocity of the methane-hydrogen gas mixture.