Experimental Study on the Effect of a Strong Negative Pressure Gradient on a Shear-Driven Liquid Fuel Film


Shear-driven liquid wall films play a major role in the fuel preparation process in advanced prefilming gas turbine combustor nozzles. Advanced two-phase flow CFD-codes have been identified as a valuable tool in the design and the optimisation process of these components.For the CFD calculations, it is assumed that the wavy liquid film propagates with a time averaged local film thickness ¯h f .
The wavy surface structure and its interaction with the gaseous phase is described via a sand grain roughness approach. For a full description of the liquid film motion, the shear-stress t at the air/liquid interface, the equivalent sand grain roughness ks and the mean film thickness ¯h f have to be determined.
To develop a correlation for the roughness effect of the wavy film surface on the driving co-current accelerated air flow, numerous measurements in an atmospheric wind tunnel have been performed. Additional experiments in a geometry typical of the technical application at elevated pressures allow a validation of this correlation.