Optimization techniques for designing an inward flow radial turbine rotor

The choice of the principal dimensions of a turbine rotor for a given set of inlet design specifications can be found by solving aerodynamic equations. An analytical method is indeed difficult and can be very time consuming, especially if the complete procedure has to be repeated for different cases. In view of this, numerical optimization techniques can be a useful tool to problems involving a large number of variables. However, turbines commonly operate at high temperature and at high speeds, therefore the design process is an interactive one between the aerodynamic requirements and the mechanical, thermal limitations. This paper describes the complete design work of a turbine rotor based on using a nonlinear optimization technique to calculate the optimum principal dimensions of the rotor including optimum number of blades. Also, a prescribed mean stream velocity approach is used to determine the optimum axial length and the flow passage. For mechanical consideration, structure and thermal stresses and modal (vibration) analyses were carried out to satisfy design requirements.