Development of an analytical model to evaluate the effect of the ported shroud on centrifugal compressors

Abstract

Extending the operational range of centrifugal compressors is strategically vital for turbocharging internal combustion engines, particularly in enhancing efficiency and expanding operational capabilities. This extension is crucial for reducing environmental impact by enabling engines to perform more efficiently under a wider range of conditions. In the transition from conventional thermal reciprocating engines, fuel cells, especially proton exchange membrane fuel cells (PEMFCs), are emerging as strong alternatives. In automotive applications, PEMFCs often require turbocharging to supply compressed air to the cathode system of the fuel cell stack. This integration is essential for utilizing the heat from the fuel cell's waste products, thereby improving overall system efficiency. Ongoing research and development in radial turbomachinery are critical for optimizing the performance of these propulsion systems. Specifically, adapting turbocharger designs to meet the unique requirements of fuel cell systems and extending their operational range are essential tasks. Using a simplified CFD model, the impact of a ported shroud on compressor performance and range extension has been investigated. Flow structure analysis identified that the primary role of the ported shroud is to modify the relative flow angle on the rotor at the highest span channel. Additionally, a simplified analytical model was developed to quantify the effectiveness of different ported shroud geometries on the compressor by examining changes in tangential velocity after mixing with the flow from the cavity.