Bifurcation analysis of lean premixed combustion of hydrogen/propane mixtures

A mathematical model of lean premixed combustion is adopted to perform the bifurcation analysis and obtain the stability maps of lean propane combustion in the presence of different amounts of hydrogen. Bifurcation diagrams were built as function of the residence time for pure propane, pure hydrogen, and intermediate mixtures. It has been found that even a small amount of hydrogen affects both the steady and the dynamic stability features of lean propane combustion. The region of existence of stable steady operating points enlarges with increasing hydrogen content. Moreover, the existence of stable oscillations prior to extinction found for propane air mixture is controlled by hydrogen substitution: the presence of hydrogen in the mixture leads to a narrower region of existence of stable oscillations and shifts them to values of the operating parameters far away from the typical operating conditions of lean premixed combustion. The effect of hydrogen is not only quantitative but also qualitative: the bifurcation diagrams of hydrogen propane mixtures cannot be viewed as a simple homothetic morphing of the bifurcation diagrams of the pure fuels but new stability features arise.