Integration of Infrared Thermography to Measure Part-to-Part Cooling Variations on Turbine Blades
Open Access
- Author:
- Knisely, Brian
- Graduate Program:
- Mechanical Engineering (PHD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 20, 2021
- Committee Members:
- Jacqueline O'Connor, Major Field Member
Reid Berdanier, Co-Chair & Dissertation Advisor
Karen Thole, Co-Chair & Dissertation Advisor
Jose Palacios, Outside Unit & Field Member
Stephen Lynch, Major Field Member
Daniel Connell Haworth, Program Head/Chair - Keywords:
- infrared
turbine
imaging
cooling
film cooling
instrumentation
blades
turbine blades
infrared imaging
infrared thermography
cooling variations - Abstract:
- Firing temperatures in gas turbine engines continue to increase to allow for higher efficiencies and reduced emissions. Cold air extracted from the compressor is used to reduce temperatures of turbine components, but efficient use of these cooling flows is needed. The thermal performance of a cooled turbine part is quantified by the overall effectiveness, where improved designs are characterized by higher effectiveness. Previous work with rotating blades used point-based sensors to study heat transfer, while spatially-resolved measurements were limited to stationary geometries. The current study builds on past work by studying effectiveness on rotating blades at engine-relevant test conditions using spatially-resolved measurements. Infrared (IR) imaging is a technique that has been widely used in gas turbine heat transfer research to measure spatially-resolved surface temperatures. Advancements in IR technologies have allowed for sensors that can measure turbine blades rotating at engine speeds, in excess of 10,000 RPM. This dissertation documents the challenges of implementing IR imaging with turbine blades, provides approaches to implement such a measurement system, and demonstrates the use of IR imaging to assess blade-to-blade cooling variations that result from manufacturing variations. An IR imaging system was developed to measure surface temperature on blades rotating at engine-relevant conditions at the Steady Thermal Aero Research Turbine (START) test facility. The IR imaging system response was characterized at integration times from 1.0 to 10.0 microseconds and 10 to 200 images averaged for stationary subjects and rotating subjects at several speeds. An experimental method and scaling parameter were developed to determine the optimal integration time for a given object speed and size. The ability to study film cooling on rotating blades with IR imaging was demonstrated. A procedure to map the acquired images to three-dimensional part space for comparisons with model predictions is described, with considerations for which mapping features to use, mesh generation, and uncertainty estimation. Manufacturing variations that affect the performance and life of film-cooled turbine blades were studied in the START rig. IR imaging was used to measure overall effectiveness variations on a section of the pressure side of nine rotating blades with the same nominal design. Film cooling trajectories were compared for the same cooling hole on each blade. Thermal results were correlated to blade flow measurements for the full blade and specific cooling holes. At low flow rates the cooling jet is swept in the mainstream flow direction, while the jet is more aligned with the hole axis at high flow rates. Variations in both film trajectories and effectiveness increased as cooling flow rate increased. Effectiveness varied by nearly 10% between blades, which when scaled to engine conditions indicated that some blades would last only half as long as other blades due to manufacturing variations.