Design of an Axial Transonic Rotor by Modified Spanwise Loading Distribution

Improving the aerodynamic performance of the transonic fan in a turbofan engine can be beneficial for both the fuel consumption and maneuverability of an airplane. Deep insight into the supersonic aerodynamics is needed for the simultaneous improvement of all operating parameters of a transonic rotor, including the pressure ratio, efficiency, and surge margin. A design method was developed for an axial transonic rotor by using a combination of radial equilibrium theory, the free vortex method, and a distributed span-wise diffusion factor. The loading distribution obtained by this method was the highest in the hub section and gradually decreased in the tip section. To evaluate the method, a transonic rotor was designed using the geometric parameters and operating conditions of NASA rotor 67. A code was developed to determine a geometry for the new rotor and to modify it. The code was coupled with a RANS flow solver for 3D modification of the new designed rotor. Only standard multi- and double-circular arc airfoils were applied in different radial sections of the new rotor with no blade profile optimization. The results of the RANS equations solution for the new designed rotor showed 1.5% higher efficiency, 3% higher pressure ratio, and more than 1.5 times larger operating range in comparison to NASA rotor 67. The new designed method seems to be an efficient approach that not only improved the efficiency and pressure ratio but also increased the operating range of an axial transonic rotor.