Inverse design approach for propfan aerodynamics based on compressible lifting surface theory

Two kinds of design methodologies of propfan were briefly discussed combined with its structure and flow features. Based on the compressible lifting surface theory, an inverse approach for propfan aerodynamics design was developed. Compared with the traditional lifting surface design method of propeller, the effects of blade rotation, compressibility, long chord length, large sweep angle and blade interference were treated strictly under the small distribution linearization assumption in rotating coordinate system. The features of the profan with hub but without casing were reflected. The kernel functions of loading-downwash angle and thickness-downwash angle for propfan design were given. The kernel functions were verified by comparing with the wing kernel functions and their convergences were studied. The chordwise and spanwise integrals of the kernel functions were discussed in detail. The ways of prescribing the distributions of design parameters, especially the optimum loading distribution, were discussed. A loss model to modify the effect of flow loss on inverse design was made. A design example was given and the accuracy of this inverse design approach was analyzed. Studies show, at some transonic sections, the prescribed chordwise loading distributions have some differences from those of numerical simulation of the designed blade due to the linearization assumption differing from the real flow nature. The prescribed element power coefficient distribution and the overall performance agree well with the numerical simulation.