Doctor of Philosophy, The Ohio State University, 2016, Mechanical Engineering

An experiment was performed at The Ohio State University Gas Turbine Laboratory for a film-cooled high-pressure turbine stage operating at design-corrected conditions, with variable rotor and aft purge cooling flow rates. Several distinct experimental programs are combined into one experiment and their results are presented. Pressure and temperature measurements in the internal cooling passages that feed the airfoil film cooling are used as boundary conditions in a model that calculates cooling flow rates and blowing ratio out of each individual film cooling hole. The cooling holes on the suction side choke at even the lowest levels of film cooling, ejecting more than twice the coolant as the holes on the pressure side. However, the blowing ratios are very close due to the freestream massflux on the suction side also being almost twice as great. The highest local blowing ratios actually occur close to the airfoil stagnation point as a result of the low freestream massflux conditions. The choking of suction side cooling holes also results in the majority of any additional coolant added to the blade flowing out through the leading edge and pressure side rows. A second focus of this dissertation is the heat transfer on the rotor airfoil, which features uncooled blades and blades with three different shapes of film cooling hole: cylindrical, diffusing fan shape, and a new advanced shape. Shaped cooling holes have previously shown immense promise on simpler geometries, but experimental results for a rotating turbine have not previously been published in the open literature. Significant improvement from the uncooled case is observed for all shapes of cooling holes, but the improvement from the round to more advanced shapes is seen to be relatively minor. The reduction in relative effectiveness is likely due to the engine-representative secondary flow field interfering with the cooling flow mechanics in the freestream, and may also be caused by shocks and other compr (open full item for complete abstract)

Committee: Randall Mathison (Advisor); Michael Dunn (Committee Member); Sandip Mazumder (Committee Member); Jeffrey Bons (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2011, Mechanical Engineering

Rotor purge flow cavity seals are used in gas turbine engines to prevent ingestion of the mainstream gas flow into the purge cavity. Ingestion into this cavity leads to an increase in the cavity air temperature and subsequently to the rotor disk and stator metal temperatures leading to higher thermal stresses and reduced disk and stator fatigue life. An over designed cavity seal with an excess amount of purge flow has the downside of increasing engine fuel consumption through reduced turbine efficiency. The opposite approach of strengthening the hardware to withstand the higher stress and temperatures would increase the weight of the propulsion system. Understanding how the purge flow cavity and cavity seals interact with the mainstream gas is important to producing a balanced design between weight, fuel consumption, efficiency, and fatigue life of surrounding hardware. The main objective of this research was to perform an experimental and computational study of a one and one half stage high-pressure turbine installed at The Ohio State University Gas Turbine Laboratory Turbine Test Facility with emphasis on the rotor purge cavity. The rig housing the turbine stage incorporated many features found in a typical commercial high-pressure turbine such as a cooled high-pressure vane row with hub and shroud cooling, a downstream blade row followed by a downstream vane row, the ability to created elevated radial inlet temperature profiles using a combustor emulator, and a cooling supply line to the purge cavity. Multiple runs were performed to study the effects of cooling flows from both an aerodynamic and heat transfer perspective and incorporated instrumentation throughout the rig in order to capture time-accurate temperature, pressure, and heat flux measurements. The run matrix included cold rig configurations with no cooling flow, high-temperature uniform inlet profiles at the vane inlet for cases with and without cooling flows, and high-temperature radial inlet profile (open full item for complete abstract)

Committee: Michael Dunn (Advisor); Sandip Mazumder (Committee Member); Mohammad Samimy (Committee Member); Jen-Ping Chen (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering

As the demand for greater efficiency and reduced specific fuel consumption from gas turbine engines continues to increase, design tools must be improved to better handle complicated flow features such as vane inlet temperature distortions, film cooling, and disk purge flow. In order to understand the physics behind these features, a new generation of turbine experiments is needed to investigate these features of interest for a realistic environment.This dissertation presents for the first time measurements and analysis of the flow features of a high-pressure one and one-half stage turbine operating at design corrected conditions with vane and purge cooling as well as vane inlet temperature profile variation. It utilizes variation of cooling flow rates from independent circuits through the same geometry to identify the regions of cooling influence on the downstream blade row. The vane outer cooling circuit, which supplies the film cooling on the outer endwall of the vane and the trailing edge injection from the vane, has the largest influence on temperature and heat-flux levels for the uncooled blade. Purge cooling has a more localized effect, but it does reduce the Stanton Number deduced for the blade platform and on the pressure and suction surfaces of the blade airfoil. Flow from the vane inner cooling circuit is distributed through film cooling holes across the vane airfoil surface and inner endwall, and its injection is entirely designed with vane cooling in mind. As such, it only has a small influence on the temperature and heat-flux observed for the downstream blade row. In effect, the combined influence of these three cooling circuits can be observed for every instrumented surface of the blade. The influence of cooling on the pressure surface of the uncooled blade is much smaller than on the suction surface, but a local area of influence can be observed near the platform. This is also the first experimental program to investigate the influence of vane inlet (open full item for complete abstract)

Committee: Dr. Michael Dunn PhD (Advisor); Dr. Sandip Mazumder PhD (Committee Member); Dr. William Rich PhD (Committee Member); Dr. Mohammad Samimy PhD (Committee Member) Subjects: Fluid Dynamics; Mechanical Engineering