Numerical Modelling Approach for Wet Humid Air Flows in Hydrogen E-Turbos

A numerical modeling approach for predicting phase transition in rapid expansions of humid air is derived. For this purpose, the well-established classical theory of condensation in wet steam flows is extended to the multicomponent flow environment. The proposed model equations for nucleation and droplet growth in humid air account for the presence of a non-condensable flow component. An Euler-Euler framework is used alongside the commercial flow solver ANSYS CFX to calculate the two phase flow. The model is validated against supersonic nozzle test cases with pressure measurements available in open literature. The onset and thermodynamic impact of phase transition is predicted with reasonable accuracy regarding the pressure distributions. Finally, the phase transition model is applied to the radial turbine stage of a fuel cell e-turbo. Droplet formation inside the turbine and the impact of phase transition on the turbine performance are discussed.