Large Industrial and Marine Diesel Engine Turbochargers

Figure 2.10 is a cross-section of a typical large turbocharger, with a radial flow compressor and axial flow turbine. The compressor impeller is made in two separate parts, the inducer and main part of the impeller. The inducer is usually machined from a steel casting or an aluminium forging, and is splined or keyed to the shaft. The impeller is machined from an aluminium forging except for very high pressure ratio requirements when titanium is used due to its superior high temperature properties. The advantage of the two piece compressor is ease of machining, but an additional benefit is some impeller vane damping provided by friction at the inducer-impeller contact surfaces. Compressor diffusers are vaned for high efficiency.