Combustion of straight glycerol with/without methane using a fuel-flexible, low-emissions burner

• Low emission combustion of straight glycerol co-fired with and without methane is achieved.
• Combustion system relies upon a two-phase atomization concept to produce a fine glycerol fuel spray.
• Gas temperature, NOX and CO emissions are reported for multiple locations inside the combustor.
• Presence of methane improves glycerol vaporization, which results in a shorter reaction zone.
• Even 100% glycerol without preheating burns cleanly, although the reaction zone is long.

In this study, we present a fuel-flexible dual-fuel combustor to simultaneously burn methane and/or straight glycerol without preheating either glycerol or air by utilizing a novel flow-blurring (FB) liquid fuel injector. Product gas temperature, NOX and CO emissions at multiple locations inside the combustor are measured to quantitatively assess the flame structure, related to liquid atomization, droplet evaporation, and fuel–air mixing in the near field. For fixed total heat release rate, the impact of fuel mix on combustion performance is investigated by varying the methane gas and glycerol flow rates. For the same fuel mix, air to liquid mass ratio effect is evaluated by varying the atomizing air flow rate. Pure glycerol flame is also investigated to demonstrate the fuel flexibility and ease of switching between gas and liquid fuels in the present system. Results show that the methane combustion can assist glycerol vaporization to results in its rapid oxidation. In spite of the differences in the flame structure, profiles of product gas temperature and emissions at the combustor exit reveal that complete and mainly lean premixed combustion with low emissions is achieved for all of the test cases indicating excellent fuel flexibility of the present combustor using the FB injector.