This paper presents a detailed loss analysis of a centrifugal compressor stage with a vaned diffuser for application in a heavy-duty engine turbocharger. The analysis is carried out in order to investigate the loss distribution in the stage. To quantify the impact of different loss types and locations, a detailed validated steady-state three-dimensional (3D) computational fluid dynamics (CFD) solution is employed. The local entropy production rate is calculated for two operating points (full load and part load), which are most relevant to the real-world operation of the compressor in a truck application. Two methods are suggested as the procedure for the division of the whole fluid volume into subvolumes because this is key for the resulting loss distribution. The primary loss-generating mechanisms are shown at main operating conditions to reveal the regions of improvement. A detailed grid study was conducted to enable the calculation of the entropy ratio. It was possible to capture around 78% (partial load) and 70% (full load) of the entropy production with a mesh with circa 100 × 106 elements. Around half of the losses were due to the boundary layer friction, followed by losses associated with a boundary layer separation resulting from the back-flow at the shroud contour close to the impeller exit and back disk friction accounted for with 6–7% of the stage's losses.

This paper presents a detailed analysis of a centrifugal compressor stage with a vaned diffuser for application in a heavy duty engine turbocharger. The analysis is carried out in order to investigate the capability of a steady-state 3D CFD to predict the pressure distribution resulting from the flow through the stage. As it is impractical to investigate the whole range of conditions, the first objective of this paper is to define the operating points, which are most relevant to the real operation of the compressor, to be used in this paper. In order to do this, the engine operation is weighted in terms of the total fuel consumption across a reference route: Portland-Pendleton-Portland. After the definition of the primary operating points, a CFD setup is created with regard to previous work on steady-state 3D CFD of a centrifugal compressor stage. The CFD analysis is validated against extensive hot-gas test stand data. The experimental data include the static pressure distribution in the diffuser shroud, determined with an array of 256 pressure transducers. A maximum discrepancy between the CFD and the experiment of around 1.6% difference is achieved for all primary operating points.

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