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Subject to excitations from pressure pulsations in boost air, the rubber pipe connecting the turbo compressor outlet and the intercooler of an engine vibrates structurally and radiates noise. If the pipe is improperly selected, the resulted vibration may be strong enough to radiate noise which is sufficient to damage the sound quality of the vehicle. This paper presents an initial analysis on this issue. First, formulae are derived for predicting vibration and sound radiation of the pipe for a given pressure pulsation, resulting in sound transmission index for the pipe to quantify its sound insulation behavior. Then effects on the sound transmission index are investigated for pipe parameters such as pipe wall thickness, Young's modulus and density of pipe material.

For a particular vehicle engine application, no suitable compressor can be found within our existing product catalogue to deliver required pressure ratio and efficiency, necessitating a new impeller to be designed. To design the new impeller satisfying requirements on both aerodynamic performance and structural reliability, the reverse engineering method is first applied to generate a baseline model with its aerodynamically key dimensions to be optimized. Then the DOE (Design of Experiment) method is performed to optimize the model for inlet diameter, exducer and diffuser widths so that the optimized compressor stage is suitable for the particular application. This paper presents the details of the development of the new impeller.