3.1 Performance maps
From the steady solution with a circumferential averaging of fluxes through the interface using the stage interface (mixing plan) the total-total isentropic efficiency and pressure rise were computed base on mass flow averaging of total pressure and temperature with respect to inlet and outlet of the computational domain. The fan stage has a large range of operation (Fig. 3), as it is characterized by a mass flow rate from 1.5 kg/s to 10 kg/s and a pressure rise from 100 mm to 950 mm of water column when the rotational speed varies from 2500 rpm to 8000 rpm. The design (nominal) point corresponds to the maximum total-total isentropic efficiency of 74% (Fig 4), obtained for the mass flow rate of 5.06 kg/s and the speed of rotation equal to 6000 rpm.