Three Dimensional Velocity and Temperature Field Measurements of Internal and External Turbine Blade Features Using Magnetic Resonance Thermometry

Abstract

Magnetic Resonance Thermometry (MRT) is a maturing diagnostic used to measure three-dimensional temperature fields. It has great potential for investigating fluid flows within complex geometries leveraging medical grade MRI equipment and software along with novel measurement techniques. The efficacy of the method in engineering applications increases when coupled with other well established MRI-based techniques such as Magnetic Resonance Velocimetry (MRV). In this study, a challenging geometry is presented with direct application to a complex gas turbine blade cooling scheme. Turbulent external flow with a Reynolds number of 136,000 passes a hollowed NACA-0012 airfoil with internal cooling features. Inserts within the airfoil, fed by a second flow line with an average temperature difference of 30 K from the main flow and a temperature-dependent Reynolds number in excess of 1,800, produce a conjugate heat transfer scenario including impingement cooling on the inside surface of the airfoil. The airfoil cooling scheme also includes zonal recirculation, surface film cooling, and trailing edge ejection features. The entire airfoil surface is constructed of a stereolithography resin — Accura 60 — with low thermal conductivity. The three-dimensional internal and external velocity field is measured using MRV. The fluid temperature field is measured within and outside of the airfoil with MRT and the results are compared with a computational fluid dynamics (CFD) solution to assess the current state of the art for combined MRV/MRT techniques for investigating these complex internal and external flows. The accompanying CFD analysis provides a prediction of the velocity and temperature fields, allowing for errors in the MRT technique to be estimated.