Design of an Air-Cooled Radial Turbine Part 2: Part 2 Experimental Measurements of Heat Transfer

The paper focuses on manufacture and testing of an additively manufactured, cooled radial turbine. To the authors knowledge, this is the first published work that provides experimental temperature data for a small, internally cooled radial wheel constructed using Selective Laser Melting. This work is highly relevant observing the close correlation between turbine inlet temperature and system efficiency. An internally cooled radial turbine was tested on the hot gas turbocharger rig at the University of Bath and compared with a baseline uncooled rotor. Thermal history paint was applied to the turbine rotor surfaces to determine the distribution of maximum exposed metal temperature. Both the uncooled and internally cooled turbine rotors were manufactured using Selective Laser Melting (SLM) technology. The resolution and strength of the printed prototype was tested prior to the high speed and high temperature experiment. The highest temperature at turbine leading edge and overall average thermal loading were compared quantitatively between the baseline uncooled rotor and the cooled rotor with internal secondary air plenums. The coolant was supplied from the compressor to the turbine through the centerline of the rotor shaft. The aerodynamic performance and component efficiency were also measured during the experiments. The test results indicate that the internally cooled turbine has a pronounced temperature drop at the blade leading edge and, indeed, throughout the blade passage. This increases the potential for increased turbine inlet temperature in order to achieve improved cycle efficiency. This experimental work has established a foundation for radial turbine internal cooling technology in the turbocharger and micro gas turbine industry.