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

Abstract

The air-management system of a proton exchange membrane fuel cell (PEMFC) is responsible for supplying the fuel cell stack with ambient air at appropriate conditions. The compressor of the air-management system can be partly driven by utilizing the fuel cell exhaust gas in a turbine. The fuel cell exhaust is partially or fully saturated with water vapor. When the exhaust gas is expanded in the turbine, supersaturation occurs. This leads to the nucleation of droplets and their subsequent growth by condensation. This study provides an overview and understanding of the various phenomena caused by condensation and liquid water in the turbine of a PEMFC air-management system. The basis for this work is previously published numerical simulations that focused on individual aspects of the above phenomena. The present work revisits these results and puts them in context to provide a comprehensive understanding. Important phenomena are the effects of condensation on turbine performance through phase change losses, release of latent heat and thermal throttling. In addition, the released latent heat offers a power potential for downstream turbine stages. Through these effects, condensation can also impact the entire air-management system. However, condensation may occur unevenly, causing a circumferential asymmetry of the turbine outflow. Liquid water in the turbine can lead to droplet erosion, corrosion, and water-induced damage. In summary, it is essential to consider condensation and liquid water when developing turbines for PEMFC air-management systems.

Analysis of condensation and secondary flows at three-way junctions using optical visualization techniques and computational fluid dynamics

“…Then, the model interacts with the numerical solver through the transport equation source terms, replicating the actual condensation process. Notice that droplet nucleation and subsequent Lagrangian particle tracking, as employed by Schuster et al [39,40] or Wittmann et al [41] in the framework of condensation in radial turbines, are not considered in this work due to the significant increase in computational effort when shifting to a Eulerian-Lagrangian approach [42].…”

A Sensorless Control Method for Energy Recovery of EGTAC to Improve PEMFC Efficiency

“…Nevertheless, the installation of a sensor at the cathode outlet of the stack to measure cathode exhaust gas parameters is both expensive and difficult to install [32]. Additionally, the low temperature at the cathode outlet of the stack generates a significant quantity of water vapor, which diminishes the precision and responsiveness of the sensor [33]. The fuel cell is also susceptible to metal ions, leading to a diminished reliability of the sensor [34].…”