Thermal Profiling of Cooled Radial Turbine Wheel

Accurate temperature measurements are required over the surface of turbomachinery to validate models that predict component life. A limited number of techniques are currently available, and all have limitations in the harsh operating conditions of turbomachinery. A new technique, called Thermal History Paint (THP), has been developed to overcome these limitations to enable accurate temperature profiles to be recorded in harsh environments. There are limited publications that cover the use of this technique. This paper demonstrates the capability of the THP through the implementation on turbine wheels.

Using the advanced capability of additive manufacturing, a cooled radial turbine wheel was designed, manufactured and tested. A solid wheel of the same external dimensions was manufactured and tested under the same conditions to act as a baseline. This paper covers the first published use of the THP to measure the spatial temperature distribution on radial turbomachinery. The results allow direct comparison between the operating temperature of the solid and cooled wheels, therefore, quantification of the effectiveness of the cooling. The paint exhibited good durability through the tests of both wheels in a hot gas rig at University of Bath.

Specific calibration data was generated for the test and the repeatability of the measurements was determined to be within 8K. Both the cooled and baseline wheels were measured at many locations and the THP recorded a significantly higher temperature on the baseline. The measured temperature profiles were in good agreement with expectation and CFD simulations. The results enable the validation of thermal models and demonstrate the capability of the new measurement technique.