Abstract
The trend towards using turbochargers in various engines continues. In some applications, including engines of light duty trucks, city buses and even tractors and harvesters, the warranty of long life is demanded because turbochargers are subject to high cyclic loading and on consequence the turbochargers can determine the lifetime of the whole engine. The replacement of the aluminium compressor wheel for a titanium one significantly improves the turbocharger lifetime, but since a titanium alloy has about 60 % higher density than an aluminium alloy, the mass and the moments of inertia of the wheel increases, which further leads to changes in natural frequencies, rotor stability and power losses in bearings assuming the same bearing system as for the rotor with the aluminium wheel is employed. In this article the influence of the increased mass properties are discussed. AVL EXCITE and in-house developed model are used for the construction of Campbell diagrams and stability maps and for the obtaining of detailed information about the behaviour of the oil films in floating bearings.
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