Towards Understanding the Improvement in Stability for Fuels with Inhomogeneous Inlets

Abstract

ABSTRACT This paper presents results from the Sydney inhomogeneous burner for two gaseous hydrocarbons: methane (CH4) and propane (C3H8). These different hydrocarbons enable the exploration of fuels with significantly different stoichiometric air-fuel ratios (A/F) and hence mixing requirements in the burner. Stability limits of blow-off velocities vs. fuel jet recession, identify that both fuels exhibit improvement due to inhomogeneity, albeit occurring at different equivalence ratios. For CH4, the largest improvement due to inhomogeneity, compared to the homogeneous limit, was close to φ = 4.76, which corresponds to V A /V F = 2. For C3H8, the peak stability occurred at φ = 12, which interestingly also corresponds to V A /V F = 2. Rayleigh imaging at 10 Hz, performed at the burner exit plane, was used to identify the mixing profiles of the two fuels for different equivalence ratios. It was verified that the optimal recess distance coincides with the most stoichiometric samples contacting the pilot, with the samples augmenting the pilot heat release. The addition of N2 further reduced the inhomogeneous improvement, verifying that mixing and the mixture near the pilot controls the inhomogeneous stability.