The market for turbochargers is growing on a massive scale: The increasing diversity of vehicle models makes it necessary to adapt supercharging systems to suit more and more engine variants. Tailor-made solutions of this type are increasing development effort which is why IAV is rethinking its methodology and has linked numerous standalone tools. This is producing better results in a shorter time.
In developing turbocharger systems, IAV is right at the side of its customers from concept and development through validation and optimization to calibration and market launch. At the concept definition and development stage, we use numerous tools developed in-house which our engineers have grouped together and linked in two blocks. Bringing together the various disciplines in this way has established an optimized development process as an answer of coping better with the growing complexity involved in developing turbochargers. This development process has now been successfully applied many times in customer projects.
Three tools for the concept phase
The first block forms the concept phase and covers the aspects of target definition, matching and benchmarking. This is where IAV uses two tools it has developed for matching and benchmarking turbochargers as well as for simulating gas exchange. The first step involves defining how to meet customer demands – such as on the turbocharger compressor. IAV makes an initial proposal which, for instance, covers the diameter of the compressor impeller as well as the minimum and maximum mass flow.
One key tool here is IAV’s supercharging database: “It contains over 150 datasets, in other words maps of compressors and turbines, and makes it possible to compare internally defined parameters at component level”, says Sven Müller, Technical Consultant for Powertrain Systems Development. After entering just a few engine parameters, the matching tool searches the database for appropriate compressor and turbine variants. The developers then simulate gas exchange in order to identify the turbocharger characteristics optimized for the particular powertrain concept while allowing for combustion parameters and dynamic effects.
This is the point at which the process is handed over to the aerodynamics developers to meet the performance requirements. The second block involves designing and laying out the turbocharger components in detail – the compressor impellers, for example. To do this, IAV’s developers use four tools for designing the impellers, CAD, FEM and CFD. In the first step, the AxCent tool is used for producing the impeller geometry which the engineers then examine with StarCCM+ (CFD) and Ansys (FEA) to establish how well it performs.
“To optimize the aerodynamics of the impeller geometry, we work through several loops made up of impeller design, CAD, CFD and FEA”, reports Tom Steglich, team manager in the Powertrain Integration division. “As soon as we have reached the targets set, we use the Creo CAD program to configure the impeller ready for production”. At the design and CFD stage, this is then followed by several loops to optimize the design of the housing. Once the turbocharger, including housing, is completely available as a CAD model, detailed CFD simulation takes place in a last step to compute comprehensive maps for the turbocharger.
These are used, for example, to compare results with engine process simulation or test bench measurements. A further IAV tool is used for developing turbines with variable guide vanes (VTG). The Matlab-based tool enables us to dimension all aspects of the entire VTG system very quickly, saving a huge amount of development time over configuring a system in the conventional way.
Better results from a deep understanding of the engine
IAV’s developers have acquired a deep understanding of the exhaust gas turbocharger system from numerous numerical and experimental studies. This begins with analyzing the thermodynamics and extends through to the component level. “This also lets us develop ideas of our own, such as the variable trim compressor (VTC) or a new wastegate concept”, explains Dr. Panagiotis Grigoriadis, team manager in the Powertrain Mechatronics division.
Further methodology improvements planned
“Better results in a shorter time” – that is one way of summing up the benefits of the new development process. In future, it is to be further improved. Among other aspects, it is planned to link benchmark and matching tool. To design turbocharger housings, it is intended to use automatic optimizers as a means of improving the aerodynamics and extending the life of turbine housings.