Development and combustion characterization of a novel twin-fluid…

Prior studies have indicated that the flow blurring (FB) injection generates fine sprays, hence clean and premixed combustion of fuels with a wide range of viscosity, though the increase in fuel viscosity causes lifted flames that might undergo blow off, and offset flame sustainability. The present study aims to achieve improved fuel prevaporization and fuel-air mixing hence, less-lifted flames and ultimately yield stable, clean, and premixed combustion of viscous fuels using a novel twin-fluid injector, called swirl burst (SB) injector. The novel injector design integrates the advantages of the FB atomization with swirling atomizing air (SAA). Preliminary spray diagnostics have shown that the novel SB injector effectively generated the SAA and enhanced secondary atomization in terms of shorter breakup length and wider spray angle compared to the FB injector. The current study investigates the global combustion performance of the SB injector for viscous straight vegetable oil (VO) by comparing with that of the FB injection. The work also explores the effect of atomizing air to liquid mass ratio (ALR) on the SB flames. The investigated combustion features include visual flame images, emissions, and thermal characteristics of straight VO sprays in a lab-scale (7 kW) swirl-stabilized gas turbine burner. Results of blue flames, temperature profiles of the combustor outer surface and gas products, ultra-low emissions of carbon monoxide and nitrogen oxides, consistently show that the novel SB concept and FB successfully achieved clean and stable lean premixed combustion for non-preheated straight VO. Compared to the FB injection, the use of the SB injector successfully resulted in a less-lifted VO flame with lower CO emissions due to early atomization completion and longer droplet path for faster fuel pre-vaporization, and better fuel-air mixing by the strengthened aerodynamic interaction between the SAA and primary combustion air. Increase in ALR for the SB injector resulted in cleaner combustion, again due to possible finer droplet evolution and enhanced aerodynamic interaction between reactant flows.