INFLUENCE OF THE BLADE STACKING ON THE FLOW THROUGH AN AXIAL-FLOW RUNNER AND PREDICTIONS OF 3-DIMENSIONAL AND QUASI 3-DIMENSIONAL NUMERICAL CODES

The influence of the stacking of the blade sections on the flow through an axial flow runner is investigated by means of quasi and three-dimensional finite element programs. The results show up higher pressure gradients close to the leading edges, in the sections near the hub, when the stacking point is displaced towards the trailing edge. These gradients become noticeable near the trailing edge when the stacking point moves towards the inlet, even if in an attenuated way these trends reverse in sections close to the shroud. The above-mentioned effects are highlighted only if three-dimensional codes or quasi three-dimensional codes with more than one hub-to-shroud surface are employed.