The Influence of Condensation on the Performance Map of a Fuel Cell Turbocharger Turbine

Abstract

Exhaust gas of an automotive fuel cell is enriched with water vapour and has a pressure potential which can be utilized by a turbine. The gas expansion in the turbine leads to droplet nucleation and condensation. This results in a release of latent heat and a decrease of the gaseous mass flow which has a considerable influence on the turbine performance. This study aims to numerically investigate the influence of these phenomena on the performance map of the radial turbine of an automotive fuel cell turbocharger. For this purpose, the classical nucleation theory and Young’s droplet growth law are integrated into an Euler-Lagrange approach. The results show an almost linear relation between the pressure ratio and the condensation while the specific aerodynamics of an operating point has only a minor influence. At 80 % relative humidity of the inflow, the investigated turbine showed condensation above a total-to-static pressure ratio of 1.8. Condensation leads to thermal throttling of the turbine and to a temperature increase of the rotor outflow of up to 50 K. Increasing humidity of the inflow increases the power output, but condensation losses reduce the efficiency.

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

“…The condensing flow in the turbine was previously investigated numerically (Wittmann et al, 2021c). For this purpose, the classical nucleation theory with the non-isothermal correction (NISO) and Young's growth law was implemented in the Euler-Lagrange framework of Ansys Fluent.…”

“…The aim of this study is to analyze the erosion phenomena observed in an automotive fuel cell turbocharger and to discuss plausible sources of water and phenomena responsible for this erosion. Earlier, the authors analyzed the condensation phenomena and their effects on the performance of the turbine studied here (Wittmann et al, 2021b;2021c). The authors are not aware of other publications dealing with the effects of condensation and liquid water on fuel cell turbochargers.…”

Modeling condensing flows of humid air in transonic nozzles

“…Due to its importance in steam turbines, condensation in flows of pure steam has been studied extensively in the past (Bakhtar, 2004). Due to the increasing importance of applications with condensing flows of humid air, such as fuel cells (Wittmann et al, 2021c), aerospace intakes (Young, 1995), electricity production (Roumeliotis and Mathioudakis, 2006), and compressor rotors (Wiśniewski et al, 2022b), accurate models are necessary. Such models are usually based on equations derived for condensation in pure steam.…”

“…Nonetheless, the vast majority of investigations uses an Euler-Euler approach for modeling condensation (Gerber and Kermani, 2004;Wróblewski et al, 2009;Starzmann et al, 2012;Chandler et al, 2014;Grübel et al, 2015). For this investigation, an Euler-Lagrange approach is used, which has been introduced and validated in more detail in Wittmann et al (2021a) and has been applied to condensation in fuel cell turbocharger turbines with humid air in previous publications (Wittmann et al, 2021b(Wittmann et al, , 2021c. Similar Euler-Lagrange models have been used to model condensation in radial turbines (Schuster et al, 2018a(Schuster et al, , 2018b and steam turbines (Gerber, 2002;Fakhari, 2006;Sasao et al, 2013).…”

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

“…In contrast, a turbine is a strict prerequisite for high-altitude fuel cell aircraft operations because of the greater pressures ratios involved. Without a turbine, the compressor would demand a major part of the power of the fuel cell [3].…”