Biet, C. and Baar, R., "Turbocharger Test Bench Extension for Acoustic Measurements at Cold Environment Conditions," SAE Int. J. Engines 8(4):1790-1797, 2015, doi:10.4271/2015-01-1672.
Acoustic measurements, especially interesting for new bearing concepts such as ball bearings, are an important part of the evaluation of turbochargers. Typically, acoustic benchmarking is done at standard conditions, neglecting possible negative effects of very low temperatures, as they might be encountered in real-world applications.For realistic turbocharger measurements at cold environment conditions down to −10 °C, special adjustments to the turbocharger test bench have been made. This article introduces a soundproofed climate chamber built in the turbocharger test bench which is able to achieve low component and oil supply temperatures while still providing adequate conditions for acoustic measurements.In the first part of the paper, the concept of the acoustic climate chamber is presented. Layout calculations are shown as an indicator for the performance of the acoustic and thermal isolation. For the second part of the paper, acoustic measurements with different turbochargers have been made at the following temperatures: 20 °C, 10 °C, 0 °C, −5 °C and −10 °C. The acoustic benchmarking included both air borne and structure borne sound as well as two distance sensors to measure the orbital movement of the turbocharger shaft at the compressor side. The experimental procedures are being described in detail.Two aerodynamically identical turbochargers, one representing typical journal bearings and the other one representing a ball bearing concept, were examined Both show a quite different acoustic behavior concerning the body temperature. While the emitted sound pressure levels of the journal bearing seem to be almost independent from the temperature, the measurements with the ball bearing do show a strong influence towards high sound emissions at low temperatures.