The Effect of Compressibility Factor on Turbine Performance

The compressibility factor Z is one of the most common properties that describes a fluid diversion from an ideal gas. Still, its effect on turbine performance is not well known. We determine a set of non-dimensional parameters that fix the gas dynamic behaviour, independent of Z, and thus isolate the effect that Z has on turbine performance. The results indicate that, contrary to the common perception, low values of Z and hence a strong diversion from an ideal gas lead to a reduction in loss for supersonic operating conditions, if all other non-dimensionals are accounted for. The aerodynamic mechanisms responsible are due to reductions in shock, boundary layer and trailing edge loss. The results from this paper are relevant for all future turbines operating with non-ideal working fluids.