This article describes the first development phase of a centrifugal compressor with variable geometry which is designed to match the needs of future heavy-duty engines. Requirements of truck engines are analyzed, and their impact on the properties of the compressor map is evaluated in order to identify the most suitable kind of variable geometry. Our approach utilizes the transformation of engine data into pressure ratio and mass flow coordinates that can be displayed and interpreted using compressor maps. One-dimensional and three-dimensional computational fluid dynamics fluid flow calculations are used to identify loss mechanisms and constraints of fixed geometry compressors. Linking engine goals and aerodynamic objectives yields specific recommendations on the implementation of the variable geometry compressor.

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.

This paper presents the development approach, design and evaluation of three turbocharger compressors with variable geometry for heavy duty engines. The main goal is the improvement of fuel economy without sacrifices regarding any other performance criteria. In a first step, a vaned diffuser parameter study shows that efficiency improvements in the relevant operating areas are possible at the cost of reduced map width. Concluding from the results three variable geometries with varying complexity based on vaned diffusers are designed. Results from the hot gas test stand and engine test rig show that all systems are capable of increasing compressor efficiency and thus improving fuel economy in the main driving range of heavy duty engines. The most significant differences can be seen regarding the engine brake performance. Only one system meets all engine demands while improving fuel economy.

This paper presents the development approach, design, and evaluation of three turbocharger compressors with variable geometry for heavy duty engines. The main goal is the improvement of fuel economy without sacrifices regarding any other performance criteria. In a first step, a vaned diffuser parameter study shows that efficiency improvements in the relevant operating areas are possible at the cost of reduced map width. Concluding from the results, three variable geometries with varying complexity based on vaned diffusers are designed. Results from the hot gas test stand and engine test rig show that all systems are capable of increasing compressor efficiency and thus improving fuel economy in the main driving range of heavy duty engines. The most significant differences can be seen regarding the engine brake performance. Only one system meets all engine demands while improving fuel economy.