Turbocharging is used as a means to downsize petrol engines, thereby, producing more power for a lower engine size, when compared with a naturally aspirated engine. The introduction of a turbocharger means that a throttle body is included in the petrol engine downstream of the turbocharger compressor. Due to the presence of this throttle valve, flow is restricted through the outlet pipe of the turbocharger during low load engine operation. For example, during transient tip out - tip in maneuvers. Hence, there is a chance of the turbocharger operating in near surge or surge conditions. Surge noise generated during this stage is clearly audible and can also affect the durable life of the compressor and other rotor systems of the turbocharger. This paper describes an experimental method to predict and measure the turbocharger surge noise. An experimental turbocharger noise rig, designed and built for this purpose, is explained. Using a time and frequency analysis of the measured data the fundamental mechanism of noise generation is identified. Finally, a passive solution to reduce the surge noise is proposed.
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