How to calculate the isentropic efficiency of turbine operation for a mixed medium (w
 

I use a mixture of hydrogen and water vapor, both with a volume fraction of 50%, as the working medium of a steam turbine. I would like to calculate the isentropic efficiency of a small steam turbine to evaluate the performance of the turbine, and I know the calculation of the isentropic efficiency of a steam turbine with a pure water vapor mass, but I would like to ask how to calculate the isentropic efficiency of the mixture (hydrogen and water vapor mixture), or if there are other parameters to evaluate the performance of this turbine.