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

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.

On the Impact of Condensation and Liquid Water on the Radial Turbine of a Fuel Cell Turbocharger

“…This corresponds with the drop in subcooling and increase in the fraction of condensed vapor in Figure 5. Adapted from [12]. Copyright 2022 ASME.…”

“…Other variables, such as velocity and pressure, are hardly affected. Detailed discussions of the aero-thermodynamics discussed in this section have been published previously [12]. in pressure ratio result in almost equal parasitic power consumption by the compressor.…”

“…These effects have been studied in great detail as part of the ARIEL (Charging for Fuel Cell Systems by Interdisciplinary Electric Air Compressors) project, which deals with the development of an automotive electric fuel cell turbocharger [8]. The findings of ARIEL regarding condensation and liquid water were discussed by the authors in several studies [9][10][11][12]. However, these publications focused on single aspects and were intended for turbine experts.…”

“…For this reason, no new simulations or experiments were carried out for this work. Instead, the individual phenomena discussed and published previously [9][10][11][12] are put into context to provide said overview and understanding. This includes a summary of the effects that a turbine affected by condensation can have on the entire air-management system, see Section 3.6.…”

“…Figure 1.Electrically turbocharged air-management system for a proton exchange membrane fuel cell (PEMFC). Adapted from[12]. Copyright 2022 ASME.…”