An Inverse Heat Conduction Approach to Heat Flux Measurements in a Two-Stage Rotating Turbine

<p dir="ltr">The quantification of the heat transfer in the flow path of a turbine is critical to the definition of more rigorous formulations of efficiency, such as the adiabatic turbine efficiency, to measure and realize the efficiency gains demanded of the next generation of gas turbines. Traditional heat flux measurement techniques and sensors based on differential temperature and calorimetric approaches are inherently intrusive as they may introduce a local distortion to the typical thermal and flow behavior on a surface of interest. As a result, they may be inappropriate for heat transfer measurements on the surface turbines that are exposed to the main flow. Inverse heat transfer solvers bypass the issue of thermal disruption and perform non-intrusive heat flux measurements, including on otherwise inaccessible surfaces, using only experimental temperature measurements as input. In this thesis, an inverse heat transfer algorithm is built on the Levenberg-Marquardt method and is validated through a series of controlled heating experiments using a canonical test article. Afterwards, an axisymmetric, thermally equivalent heat transfer model of the two-stage Purdue Small Turbine Aerothermal Rotating Rig (STARR) casing is created and coupled to the inverse heat transfer algorithm. Finally, infrared (IR) measurements of the outer casing metal temperatures from a legacy STARR test campaign are input to the inverse heat transfer algorithm to quantify the transient heat transfer to the turbine casing in two distinct loaded tests.</p>