| Many numerical optimization methods have been developed and used for design optimization of rotor bearing system. Most of these available rotor-bearing system analysis programs make use of gradients to search feasible design parameters to achieve optimal objective functions. These methods are reasonably effective for well-behaved objective functions, because the gradient of the function helps to guide the direction of the search. However, when the continuity and existence of derivatives of objective function are not present, gradient methods lack robustness and may become trapped in local optima. These problems with the application of numerical optimization are difficult to over come. The development of faster computers has allowed implementation of more robust and efficient optimization methods. Genetic algorithms are one of these robust methods. Genetic algorithms are classified as guided random search techniques. They use objective function information instead of derivatives.; In this dissertation, procedures based on genetic algorithms have been developed and presented for design optimization of three-lobe and tilting-pad journal bearings in rotor systems. This optimization approach is based on film thickness, power loss, stability, film temperature, film pressure, and global objective. There is a strong relationship among these design objectives. There are common bearing design variables that influence these objectives. The design variables such as pad axial length to journal diameter ratio, pad arc length, bearing radial clearance, pad offset factor, pad preload factor, and bearing orientation with respect to load, play an important role in design optimization of rotor-bearing system objectives.; The results are verified in a further step, where a complete rotor-bearing system is optimized. The examination and validation of the proposed algorithms are compared with results from a numerical method. The results showed the feasibility and superior effectiveness of genetic algorithm techniques for the design optimization of rotor-bearing system. |
