Platform Development of Fuel Cell Air Compressors and Turbine Expanders

Hydrogen fuel cell is one of paths to achieve carbon neutrality transportation. In the last two decades, significant improvements have been made in compactness, efficiency and durability of fuel cell systems. For heavy duty truck applications, a life span similar to heavy duty diesel engines is required. As a critical component in the fuel cell system, air compressors play an important role to meet fuel cell systems’ high efficiency and durability requirements. In this paper, a holistic approach has been taken to develop a series of airfoil bearing centrifugal compressors for a wide range of applications from forklift, passenger vehicles to commercial vehicles, and achieve high efficiency and durability of one million start-stops. In the new platform development, cooling circuit was optimized so that the external cooling air circuit for the rotor and air bearings is no longer needed, which resulted in 4% efficiency improvement. Hollow rotor structure was adopted to achieve lightweight and high stiffness for higher operating speed. The corresponding silicon carbide (SiC) controllers capable of 100K Hz frequency were developed with 99% efficiency and software was developed to achieve precise speed control and optimized take-off and shut-down profiles. Foil air bearings were developed to provide adequate loading capacity and durability. Overall efficiency of permanent magnet synchronous motor (PMSM) and controller achieved 95%. Newly developed compressors were validated in the stringent bench tests and vehicle road tests.