The development of the aerofoil-shaped turbomachine blades is of prime importance for achieving the appropriate deflection of a three dimensional flow through desired angles, to work at the same degree of incidence and thereby providing the required performances for the specific machine. The sensitivity of the rotor to incidence effects and tendency of the flow to separate from one or the other blade surface have given rise to considerations of the optimum incidence angle and cone angle for a mixed inflow turbine by a numerical investigation using the ANSYS-CFX code. In order to keep the rotor in the same casing some geometrical parameters have been hold constant and the Bezier polynomial is used to generate the new shape of the rotor blade when changing the cone angle magnitude.

An investigation on new rotor blade designs conceived to produce higher exit relative kinetic energy of a mixed flow turbine is undertaken. Accelerating the flow through the rotor in a relative frame of reference improves energy transfer to the shaft, which is only produced in a rotating rotor. A three-dimensional converging rotor channel might respond to the analysis requirements in the subsonic flow regimes. Effectively, the machine experiences a 3.71 % and 3.67 % increase in work output and efficiency, respectively, representing this study’s primary intent. This has been accomplished by varying the shroud profile to a lesser eye tip diameter, then the hub profile to a larger eye root diameter. At last, both shroud and hub profiles are varied. It appears possible to enhance the performance of the rotor in terms of optimum work done and efficiency by devising suitable blade geometry designs. ANSYS CFX 15 is the code of all simulation works.

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.

The blade shape is of great interest to hybrid turbine designers, due to its significant and direct impact on turbine performance. The inlet and outlet diameters of the vane affect the size of the rotor, which is limited because of the small space available in internal combustion engines. The effect of the ratio of the average inlet diameter and the average exducer inlet diameter on the performance of a mixed inlet turbine will be the focus of this study, which consists of two cases included herein for the purpose of illustrating the means of improving rotor performances and controlling the flow mass rate. In the first case, we achieved this by changing the average diameter of the exducer inlet, while, in the second one, we achieved this by changing the average inlet diameter. Additionally, the angles of the inlet and outlet blades were recalculated to preserve the same blade profile and to eliminate the effect of curvilinearity. It was noted that the shape of the blade was very sensitive to changes in the ratio of the investigated diameters, and—in both cases—interesting results were obtained. First, an increase in output work and in total static isentropic efficiency by 2.16% and 2.15%, respectively, was generated, with a saving of 3.52% of the used mass flow and a lighter rotor compared to one that used to take up the same space by using fixed average inlet diameter blades. In the second case, there was an increase in the output work by 3.31%, and in the total static isentropic efficiency by 3.34%, but the rotor became heavier and required an increase in the mass flow used. Since inter-blade flows are very complex, three-dimensional and viscous—featuring various types of secondary and eddy flows—the CFX.15-CFD code was used in all models to solve the averaged Navier–Stokes equations.