The Effect of Blade Angle Deviation on Mixed Inflow Turbine Performances

Abstract

The choice of blades for mixed turbines is to achieve the required deflection with minimal losses. In addition, it is necessary that the blade functions without a detachment in a wide area outside the nominal operating point of the machine. In the blade profile study, it is required to satisfy the conditions relating to fluid mechanics and those relating to the possibility of realization of construction. The work carried out presents the effect of the blade deviation angle on the geometric blade shape and the performance of the mixed inflow turbine on keeping the same rotor casing in order to improve its performances. It was remarked that the efficiency is proportional to the deviation angle’s increase, but the rotor became heavy. It has been determined that the effect of the blade deviation angle on mixed inflow performances decreases dramatically starting from the angle −20° for a 100% of machine load. It was urged to avoid relying on angles greater than −20 as values for blade deviation angles. The study noted that the maximum obtained in the output work and power is related to the highest the efficiency for a specific optimum design case (−35° of deviation blade angle) due to the increase in the contact surface between the blade and the fluid, but the problem is that the rotor gets a little heavy (4.37% weight gain). Among recommendations, attention was given to the more significant absolute exit kinetic energies, for values of deviation blade angle between -10° and −20°, where an exhaust diffuser is recommended to use to recover a part of it into a greater expansion ratio. These simulation results were obtained using a CFD calculation code-named CFX.15. This code allowed for the resolution of the averaged dynamic equations governing the stationary, compressible, and viscous internal flow.