Calibration Of Infrared Window And Study Of The Wind Tunnel Properties

Open Access
Author:
Axten, Christopher Joseph
Area of Honors:
Aerospace Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Mark David Maughmer, Honors Advisor
  • Cengiz Camci, Thesis Supervisor
Keywords:
  • Convective Heat Transfer
  • Pin Fin
  • Infrared Imaging
Abstract:
In the world of turbomachinery, increasing the efficiency of the air-breathing gas turbine engine is always the end goal, which is accomplished by operating at the highest possible turbine inlet temperature. However, this leads to issues in designing turbine blades, typically made of nickel alloys, that are capable of withstanding the thermal stresses associated with combustor exit temperature. Thus, bled off air is commonly passed through turbine blades in a serpentine pattern and over pin fins within the blades to increase the blade cooling. The most common pin fin design uses a circular cross section, however past studies have shown other cross sections are more favorable. Different pin fin geometries, and configurations of pin fins, produce varying temperature fields around the pin fins, and thus can produce different convective heat transfer results. An optimized pin fin design and configuration would improve the convective heat transfer while not compromising on the pressure losses over the pin fins, which would ultimately result in turbine blades reaching higher temperatures and thus higher efficiencies. Past studies have performed their measurements with liquid crystal thermography on the endwall to determine the convective heat transfer coefficients. This study seeks to instead use infrared thermography to measure the temperature field of the endwall to determine the convective heat transfer characteristics. This method requires calibrating an infrared window that is set to view the heated endwall, which acts as the test section. The experiments were conducted using a FLIR T620 high resolution infrared imaging camera. The test section of the wind tunnel was set up with an infrared window from Edmund Optics. One endwall of the test section is uniformly heated by supplying different voltages, from 0 to 75 Volts, to a thermofoil Minco heating element for various velocities, ranging from 20 meters per second to 30 meters per second. The transmission losses, conduction losses, and convective heat transfer coefficient were determined from infrared images and thermocouple temperature readings. The flow around through the tunnel was observed and through the recorded temperature field the convective heat transfer coefficient of the test section was calculated. The entire experiment was conducted in the Turbomachinery Heat Transfer Lab open loop wind tunnel.