Dimensional Analysis and Experimental Validation for a Rotary Vane Expander Operated with Air or Hydrogen at Different Feeding Pressures

Rotary vane expanders are employed usually to power tools in industry, using industrial compressed air as working fluid. The commercial rotary vane expanders are designed in accordance with ISO 2787. Because they may be employed also for other scopes, this work evaluates their power and isentropic efficiency when operating with air or hydrogen at different inlet pressures by way of a dimensional analysis, which is carried out considering the variables affecting the performance, such as inlet and outlet pressures and temperatures, gas viscosity, and rotational speed. The outcome of the analysis comprises two dimensionless performance maps: one for power and another for isentropic efficiency. With the use of a specially designed test bench, data for constructing the performance maps are gathered with air and hydrogen. The model is then validated while operating with air or hydrogen under different inlet pressures, ranging from 370 to 720 kPa with expansion ratios between 2.0 and 3.0. The output shows good accuracy in predicting the power and isentropic efficiency of the expander with errors lower than 6.70% and 6.74% respectively.