Towards Understanding the Improvement in Stability for Fuels with Inhomogeneous Inlets

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.

KEYWORDS:

• Turbulent
• laser diagnostics
• mixed mode combustion

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Australian Research Council (ARC) and AFOSR (USA).