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Casaday, Brian PatrickInvestigation of Particle Deposition in Internal Cooling Cavities of a Nozzle Guide Vane
Doctor of Philosophy, The Ohio State University, 2013, Aero/Astro Engineering
Experimental and computational studies were conducted regarding particle deposition in the internal film cooling cavities of nozzle guide vanes. An experimental facility was fabricated to simulate particle deposition on an impingement liner and upstream surface of a nozzle guide vane wall. The facility supplied particle-laden flow at temperatures up to 1000°F (540°C) to a simplified impingement cooling test section. The heated flow passed through a perforated impingement plate and impacted on a heated flat wall. The particle-laden impingement jets resulted in the buildup of deposit cones associated with individual impingement jets. The deposit growth rate increased with increasing temperature and decreasing impinging velocities. For some low flow rates or high flow temperatures, the deposit cones heights spanned the entire gap between the impingement plate and wall, and grew through the impingement holes. For high flow rates, deposit structures were removed by shear forces from the flow. At low temperatures, deposit formed not only as individual cones, but as ridges located at the mid-planes between impinging jets. A computational model was developed to predict the deposit buildup seen in the experiments. The test section geometry and fluid flow from the experiment were replicated computationally and an Eulerian-Lagrangian particle tracking technique was employed. Several particle sticking models were employed and tested for adequacy. Sticking models that accurately predicted locations and rates in external deposition experiments failed to predict certain structures or rates seen in internal applications. A geometry adaptation technique was employed and the effect on deposition prediction was discussed. A new computational sticking model was developed that predicts deposition rates based on the local wall shear. The growth patterns were compared to experiments under different operating conditions. Of all the sticking models employed, the model based on wall shear, in conjunction with geometry adaptation, proved to be the most accurate in predicting the forms of deposit growth. It was the only model that predicted the changing deposition trends based on flow temperature or Reynolds number, and is recommended for further investigation and application in the modeling of deposition in internal cooling cavities.

Committee:

Jeffrey Bons (Advisor); Ali Ameri (Committee Member); Michael Dunn (Committee Member); Datta Gaitonde (Committee Member); Sandip Mazumder (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

particle deposition; turbomachinery; internal cooling, engine fouling

Rao, Chadalavada BhaskarEnchanced extrusion with internal cooling die
Master of Science (MS), Ohio University, 1980, Chemical Engineering (Engineering)

The objective of this work was to design a biaxial die, with which extrusion could be done horizontally, thereby allowing better control of the temperature in the land and improvements in the operating con- ditions. The land temperature gradient was impressed previously by immersion of the exit end of the die under water. This improved design should be used with or without a melt conditioner.

Polyethylene and polypropylene were extruded through a 12/1 (deformation ratio of 12 to 1) biaxial die, using a C.W. Brabender Model 200 Single Screw Extruder. The die was cooled with Teflon ®to reduce friction between the walls of the die and polymer. The ribbons extruded were highly oriented and had high tensile properties and were 1.5 inches wide and 1/32 inches thick. Prestone ®and water were used as coolant. For polypropylene the maximum extrusion rate of oriented ribbon was 9.2 inches per minute. Oriented polyethylene could not be produced successfully using this die.

Thermal analysis of polypropylene samples demonstrated a 7.5° C melting point elevation and polyethylene samples demonstrated a max- imum of 3.5° C elevation in melting point. For polypropylene samples the maximum crystallinity obtained was 77.5%, maximum tensile strength was 67,840 Psi (0.468 G Pa). There were no changes in dimensions when kept in an oven at 100° C and at 140° C for a maximum of one hour.

It was demonstrated that the horizontal extrusion can be done without producing surface defects and can enhance the orientation. The work suggests that the samples can be reproducible if the flow rate and temperature of the coolant are controlled.

Committee:

John Collier (Advisor)

Subjects:

Engineering, Chemical

Keywords:

Internal Cooling Die; Melt Conditioner; Polyethylene; polypropylene

Peterson, Blair AA Study of Blockage due to Ingested Airborne Particulate in a Simulated Double-Wall Turbine Internal Cooling Passage
Master of Science, The Ohio State University, 2015, Aero/Astro Engineering
The development of flow blockage by particulate accumulation in the internal flow passages of a gas turbine double wall cooling scheme was studied experimentally. This parametric investigation focused on the effects of particle concentration, flow temperature, and particle size on the deposition characteristics in a cylindrical impingement/film cooling geometry. The impingement and film cooling hole layout is based on the leading edge cooling scheme of a modern nozzle guide vane (NGV). Tests were run at a constant pressure ratio of 1.02 (cavity pressure to exhaust) and the mass flow rate was permitted to decrease throughout the test as the cooling passages became obstructed. Particulate concentration was varied by holding the mass injected constant while adjusting the test injection time and rate. Particles consisted of Arizona Road Dust with distributions of 0-5, 0-10, and 0-20 µm. Flow blockage increased by 4% over a range of two orders of magnitude in particulate concentration for the smallest particle size distribution. At 452 °C the blockage levels increased to nearly four times that of the ambient conditions. Similar amounts of particulate deposited on the film cooling wall at ambient and high temperature, but the high temperature particulate caused greater blockage to the film holes. The effect of particle size was difficult to discern due to clumping of the smallest particles into large agglomerations. This clumping effect was coupled with the trend of increasing temperature. Implications for continued internal deposition research are discussed.

Committee:

Jeffrey Bons, Dr. (Advisor); Randall Mathison, Dr. (Committee Member)

Subjects:

Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

Gas Turbine; Deposition; Film Cooling; Impingement Cooling; Particulate Ingestion; Flow Blockage; Internal Cooling; Double-Wall;