Investigation of Water Droplet Erosion in the Radial Turbine of a Fuel Cell Turbocharger

Abstract

Radial turbines of fuel cell turbochargers are prone to water droplet erosion (WDE). Test bench runs of such a turbine showed erosion zones on the rotor suction side near the leading edge and on the stator suction side near the trailing edge. The aim of this study is to analyze this erosion and determine which droplet trajectories are responsible for it. For this purpose, Euler-Lagrange simulations of the non-equilibrium condensing flow are analyzed with regard to droplet deposition. It is shown that the droplets originating from condensation are not responsible for the observed erosion. It is therefore investigated whether an inflow of droplets from the fuel cell itself can be responsible for the erosion. The study indeed shows that such droplets can form wall films on rotor and stator. Therefore, the observed erosion is most likely the result of droplets formed by the break-up of wall films at the trailing edge of the stator vanes and also at the leading edge of the rotor blades.

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

“…WDE can be seen in the last third of the suction side of all stator vanes (Figure 12a) and on a narrow vertical strip near the leading edge of the suction side of all rotor blades (Figure 12b). As part of the ARIEL project, Euler-Lagrange simulations were performed to determine which droplet trajectories are responsible for this erosion [11]. The simulations showed that droplets formed by condensation occur too far downstream to be the cause of the WDE.…”

“…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.…”