The effect of absolute pressure on deposition testing is studied in the unique experimental High-Pressure Deposition Facility at The Ohio State University. Mass flow blockage and capture efficiency trends are presented for the case of deposition in a single-wall flat plate effusion cooling geometry. Arizona Road Dust in the range of 0-10 µm is delivered to a 950K coolant flow at a pressure ratio of 1.03 at absolute pressures ranging from 0.97 to 15.8 atm. The primary results indicate a non-linear decrease in both capture efficiency and blockage with increasing absolute pressure. Three potential physical mechanisms that may cause this behavior: increased particle drag, elevated flow discharge coefficient, and enhanced erosion effects are investigated via additional targeted experiments and companion Computational Fluid Dynamics (CFD) simulations. It is demonstrated that at these conditions, particles in the 5-10 µm range are capable of eroding existing deposits and reducing flow blockage. To isolate drag effects from the changes in average flow velocity that occur at higher pressure due to an increasing discharge coefficient, a reduced pressure ratio experiment is run to match volumetric flow rates at various pressures. The results reveal that blockage and sticking rates drop less dramatically with pressure when the velocity fields are approximately matched, however, particles with higher Reynolds numbers are nonetheless able to navigate the cooling hole more effectively. To support these conclusions, mesh morphing simulations are performed at 0.97 and 15.8 atm using the OSU Deposition Model, which captures both impact velocity and angle dependencies of deposition. The resulting structures and their unique characteristics are compared to experimental deposits, and the blockage computational and experimental blockage histories are presented.


An Experimental and Computational Investigation of Absolute Pressure Effects on Deposition in an Effusion Cooling Geometry

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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