Analysis of the Condensation Phenomena Within the Radial Turbine of a Fuel Cell Turbocharger

Abstract

Abstract Cathode systems of proton exchange membrane fuel cells are tasked with providing compressed air for the fuel cell stack. The exhaust gas from the fuel cell has a pressure potential which can be utilised in a turbine to partially power the compressor. Therefore, a radial compressor and a radial turbine are often combined with an electric motor to form an electric fuel cell turbocharger. The exhaust gas used to operate the turbine is humid and hence prone to condensation. Previous studies on such condensation only investigated a turbine segment and neglected the volute. This study overcomes this simplification and analyses the aerodynamics of the full-annulus flow of volute, stator and rotor. The focus is set on the effect of the circumferential asymmetry on the occurrence and strength of condensation in the turbine rotor. The effect of variations of the rotational speed is also investigated. The main finding is, that such asymmetries or speed changes can have a significant effect for operating points for which they are able to determine the occurrence of condensation. Operating points with no or with certain condensation are less affected.