Abstract

In marine diesel engines, transonic centrifugal compressors are widely used due to their capabilities to: 1) downsize engines by increasing output power; 2) cause less fuel consumption; 3) enhance the combustion efficiency. Apart from the traditional requirements such as good choke and stall margin, high boosting pressure ratio, and high stage efficiency, it is also necessary to reduce the turbocharger noise as much as possible for a more comfortable working environment. The most effective way is to reduce the compressor noise at the source, i.e. the compressor impeller itself must produce less aerodynamic noise rather than using any silencers. In this paper, we present a redesign work for an existing impeller wheel using the 3D inverse method with an in-house aeroacoustic code. The CFD simulations for the compressor characteristics and internal flow field details, the numerical predictions of aeroacoustic sound emissions, and FEA analysis for the structure integrity have all been attempted to thoroughly assess the performances of baseline and optimised impellers. The computational results found that the new impeller can lead to better performances in all three aspects, which are supported by the experimental measurements conducted for both impellers using the same test configurations. The experimental data confirmed that the inversely redesigned impeller wheel provides a wider compressor operating range, higher efficiency at large rotating speed, and a few dB(A)s lower noise emissions in the upstream radiation direction.

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