15th European Conference on Turbomachinery Fluid dynamics & Thermodynamics

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Main Topic:

Operational Experience



Markus Schödel - Leibniz Universität Hannover, Germany
Philipp Nachtigal - Leibniz Universität Hannover, Germany
Joerg R. Seume - Leibniz Universität Hannover, Germany


The air supply system of a PEM fuel cell usually consists of a centrifugal compressor as the core component. The operating range of turbomachines is generally limited, reducing the operational flexibility of the fuel cell. In order to supply the fuel cell with sufficient air at any operating point and keep the compressor in a stable range, it is necessary to bypass some fraction of the compressor air at part-load. This bypassed air mass flow does not contribute to the power generation of the fuel cell, increasing the parasitic power consumption and therefore lowering the system efficiency. Within this study, different compressor range-extending features are investigated experimentally. For the investigations, the impeller geometry is kept constant and only the diffuser is modified. Experiments with different static diffuser inserts show the potential of pivoting the diffuser vanes: The surge margin of the compressor increases by up to 44.7 percentage points. However, due to efficiency losses, the compressor power consumption increases when the fuel cell is operated at full-load. Further experiments with different leading edge angles of the diffuser vanes demonstrate that the map of the centrifugal compressor can be shifted towards lower mass flow rates. Thus, the compressor map is adapted to the operating range requirements of an automotive fuel cell. While the original compressor is only able to cover 68 percent of the total fuel cell’s operating range with a surge margin of 20 percent, a compressor with adapted leading edge vane angles in the diffuser covers over 76 percent. By reducing the leading edge angle over the vane height of the diffuser linearly, the compressor power consumption decreases over the entire operating range of the fuel cell. A reduced power consumption of up to 6.3 percent is achieved at part-load.


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