Experimental investigation on the influence of ambient pressure on twin-fluid atomization of liquids with various viscosities

Twin-fluid atomization for combustion application has been investigated over the years for a wide range of operating conditions and typically low viscous liquids. Nevertheless, little has been published concerning twin-fluid atomization for entrained flow gasification (EFG) application. Twin-fluid atomization for EFG is connected with several challenges arising from the specific technical operating conditions. Typically, the system operates by gasifying high viscous liquid or suspension fuels featuring viscosities up to 1000 mPa s and complex rheolog-ical behavior. Additionally, the atomization of such fuel is performed at elevated ambient pressure (up to 80 barabs) due to the subsequent process step.
Detailed investigations applying state of the art measuring techniques on the atomization of high viscous liquids using external mixing twin fluid atomizers at increased ambient pressure are scarce. Research work pre-sented is therefore focused on the atomization of liquids within a wide range of viscosities at increased ambient pressure. The experiments in the current study were conducted at several pressure stages (1 – 21 barabs) at the pressurized spray test rig (PAT) using the Newtonian liquids water (1 mPa s) and water/glycerol-mixture (100 mPa s). ... mehrThe droplet size and velocity distribution within the spray was measured using a Phase-Doppler-Analyzer (PDA) at several axial locations with high radial resolution. A high-speed camera was used for the visualization of the jet disintegration process and spray angle determination. Experimental results reveal that for a fixed liquid mass flow and constant atomizing air velocity Sauter mean diameter (D32) decreases with increas-ing ambient pressure for both low and high viscous liquids. Additionally, a distinct increase of D32 was observed with increasing axial distance for increased ambient pressure. Both, ambient pressure and viscosity have a signif-icant influence on this effect which can be attributed to droplet coalescence.