Fine Particulate Deposition in an Effusion Plate Geometry

Abstract

Fine particulate deposition testing was conducted with an effusion plate geometry representative of a gas turbine combustor liner. Preheated coolant air with airborne particulate was fed into an effusion plate test fixture with the flow parallel to the target plate. The test fixture was in an electric kiln that establishes elevated plate temperature, similar to a gas turbine combustor. Test variables include hole diameter, length/diameter ratio, inclination angle, and compound angle. In addition, coolant and plate temperature were varied independently to determine their influence. All tests were continued until the effusion holes had blocked to produce a 25% reduction in mass flowrate while maintaining constant pressure ratio. The blockage rate was found to be more sensitive to flow temperature than to plate temperature over the range studied. Blockage rate was insensitive to effusion hole diameter from 0.5 to 0.75 mm but increased dramatically for hole diameter below 0.5 mm. Blockage shows a moderate increase with hole length/diameter ratio. The strongest dependency was found with the inclination angle; roughly an order of magnitude increase in blockage rate was documented when increasing from a 30 deg to 150 deg. A compound angle of 45 deg caused a negligible change in blockage rate, while a compound angle of 90 deg increased blockage rate for low inclination angles while decreasing it for high inclination angles. For the flow angle dependency, interpretation is provided by means of computational fluid dynamics (CFD) simulations of the particulate delivery and initial deposition location prediction using the Ohio State University (OSU) deposition model.