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.

Das Betriebsverhalten eines elektrischen Turboladers zur Bedruckung des Kathodengassystems eines automobilen Brennstoffzellensystems wird unter Berücksichtigung der feuchten Brennstoffzellenabluft untersucht. Basierend auf den Komponentenkennfeldern von Elektromotor, Leistungselektronik, Lagerung und Turbomaschinenkomponenten werden stationäre und transiente Betriebslinien berechnet, anhand derer eine Betriebspunktverschiebung gezeigt wird. Diese kann auf die Einflüsse der Gaszusammensetzung und Kondensation in der Turbine zurückgeführt werden. Anhand von drei stationären Betriebspunkten wird die Zusammensetzung der Verluste innerhalb der Maschine gezeigt. Die Verzögerung wird zudem als kritisches Manöver im transienten Betrieb durch signifikante Abnahme des Pumpgrenzabstands identifiziert. / The performance of an electric turbocharger for the cathode gas supply system of an automotive fuel cell system is investigated considering moist air off gasses. Based on the component performance maps of electric motor, power electronics, bearings and turbomachinery, steady state and transient operating lines are calculated and a shift of operating points is shown. These can be traced back to the influence of gas composition and condensation within the turbine. Based on three operating points, losses inside the machine are characterized. Furthermore, deceleration is identified as the most critical transient operating scenario due to a significant decrease of the surge margin.

Towards a carbon free society the IHI group is committed to provide products, technologies and services in line with ecological and economical sustainability. Storage and transportation of green energy are major challenges related to the global transition from fossil fuels towards 100% renewables. IHI is active in various areas ranging from SOFC technology via ammonia combustion to smart community demonstrator projects. With respect to mobility hydrogen fuel cell technology is identified as one major pillar for CO2-neutral vehicular propulsion – especially for higher payloads and extended driving distances. Since more than 20 years IHI is providing charging systems for stationary fuel cell applications and since 2004 also for mobile fuel cell applications. IHI´s oil free turbocharger for fuel cell applications is providing state-of-the-art boosting technology to enable emission free propulsion systems. It comprises a turbine, a compressor and, on the same shaft, an electric motor as well as air foil bearings to support the rotor. The turbine utilizes the enthalpy from the stack exhaust to lower the required electric power for driving the compressor. It can provide up to 40% of the needed compressor power and hence substantially increases the system efficiency. Compressor and turbine are optimized for operating conditions in fuel cell systems regarding specified airflow and pressure ratio, which is typically in the range of 3.0.