Thermal Design of High Pressure Ratio Turbocharger Compressor Wheels

High pressure ratio turbocharger compressor wheels have significantly high temperatures at the exducer side and also heat input from the bearings. The temperature distribution could reach ranges where the compressor wheel, usually made from aluminum alloys, could creep and start rubbing. For this case the design process should include design for thermal stresses.

Heat transfer analysis whether using convection coefficients or results from a conjugate heat transfer CFD analysis should be calibrated against experimental values.

However, it is difficult to obtain temperature values on rotating parts. The temperatures in high pressure ratio wheels make the measurement of these temperatures difficult as it is difficult to make the instrumentation survive at these high temperatures. In the work described in this paper a new approach was developed to measure temperatures on high speed rotating wheels. The system developed was a telemetry system comprising of a transmitter and a set of rotating and stationary antennas The nature of the system and the positioning of the transmitter enabled the measurement of the temperatures without damaging the instrumentation. The temperatures measured using this system were used to calibrate heat transfer coefficients for thermal stress analysis.

The thermal stress contribution to the stresses in the exducer and back disk regions were significant and cannot be neglected. This method was used to develop a new process for thermal design of compressor wheels.