Effect of Fuel Temperature on the Structure of a High-Pressure Liquid-Fueled Swirl Flame

Experiments were conducted in a liquid-fueled, piloted swirl burner operating at high pressure (1.0 MPa and 2.0 MPa) to study the influence of fuel injection temperature on the coupled flow and combustion processes. Simultaneous 10 kHz stereoscopic particle image velocimetry and OH* chemiluminescence measurements were used to characterize the overall flow and flame structure over a range of equivalence ratios at three discrete fuel temperatures: 367, 486, and 577 K. The location of the pilot flame was found to be insensitive to the fuel temperature, while the main flame moved closer to the injector as the fuel temperature was increased. This was accompanied by an increase in the axial velocity in the region of the main flame and a downstream shift of the shear layer along the border of the central recirculation zone. Analysis of the mean velocity fields relative to the location of maximum OH* chemiluminescence intensity showed an increase in velocity normal to the mean flame position with higher fuel temperatures. This indicates the flame speed increases with fuel temperature, which, along with the changes to the fuel injection process, helps explain the observed changes to the flow and flame structure.