Abstract
This paper presents an experimental approach for investigating the noise characteristics of a turbocharger of a medium-duty diesel engine ? the whine noise induced by turbine blade rotation at around low idle, and suggests a way to eliminate the audibility of the whine noise radiated from turbine housing outlet. This whine noise makes passengers or outside walkers nervous unless the noise is enough to be absorbed by mufflers. Since there is little difference in noise radiated from turbine outlet between firing and motored conditions of an engine at around low idle, the whine noise is investigated under the motored condition. The noise is examined to several physical parameters ? turbine housing dimensions, turbocharger speed, non-rotation of turbine blades, and so on. From the test results, the study suggests a practical combination of two parameters to eliminate the audibility of the noise, where the whine noise component is lower by over 15dBA than overall noise level.