A turbocharger unit mainly consists of a centrifugal compressor and a turbine coupled together by a solid shaft. This is employed to boost the charge air pressure of the engine. Turbocharging in modern diesel and gasoline engines have become a common and essential operation to result higher power outputs, lower emissions, improved efficiency and refinements from a similar capacity of naturally aspirated engines.
The automotive turbocharger system is a source of synchronous and asynchronous noises that should be eliminated or reduced for passenger comfort. Subjectively, a high whistle noise was audible in the passenger cabin during in a mid-rpm range drive in all gears in a 4 cylinder diesel vehicle. Objective noise and vibration data confirm the issue as unbalance whistle.
A detailed study has been carried out to identify the source and radiating part of the unbalance whistle noise generated in a 4 cylinder diesel engine running a passenger car. This paper presents the work carried out to reduce unbalance whistle in passenger cabin. The paper is categorized in three segments. First section describes the NVH aspects of turbocharger. Second section describes the root-cause analysis and concept formulation for the noise problem. The final section describes the solution which reduces the whistle noise in passenger cabin.