Optimization Of Rotor-bearing Systems Research Articles

Multiobjective optimization of rotor-bearing systems with an investigation of goal programming approach

With ever-increasing demand for higher flexibility and higher speeds of operation of high-speed rotating machinery, study of their unbalance responses and stability are of paramount importance. For easier maintenance and transport, weight of such systems is also a critical criterion. In the present study, optimum design parameters of a rotor-bearing system are found by employing multiple multiobjective optimization schemes for simultaneously minimizing unbalance response, maximizing stability limit speed, and minimizing system weight. This is an improvement over previous systems where simple equal weighting of multiple objective functions is carried out to reduce computational challenges. The shaft is assumed to be hollow and modeled as an assembly of 10 two-noded Euler–Bernoulli beam elements with an isotropic disc mounted on it. Genetic algorithm and its multiobjective variant (NSGA-II) are used to find the global optima. The technique of goal programming is identified as a more practical and less computationally challenging alternative to Pareto-based optimization, while yielding an approximate optimum. Complexities arising due to gyroscopic effects and dynamic nature of anisotropic fluid film bearings are also considered, along with practical upper and lower bounds of design variables and maximum von Mises stress developed in the system as constraints.

Optimum design of rotor-bearing system stability performance comparing an evolutionary algorithm versus a conventional method

The main intent of this paper is to formulate, demonstrate, and validate a practical means of implementing an evolutionary optimization technique in a rotor-bearing system. The optimum design of a flexible rotor supported on three-lobe bearings is studied for the optimal performance considering system stability along with other design criteria such as fluid film thickness, power loss, film temperature, and film pressure using the genetic algorithm and the method of feasible directions. The results for different operating speed values obtained and presented in this study are to provide a comparison of these two methods, and to show the potential of the genetic algorithm in optimization of rotor-bearing systems. The genetic algorithm obtained reasonably good results for the objective function and comparable to the method of feasible directions. Thus, the genetic algorithm provides the designer an alternative design optimization approach for rotor-bearing systems.

Sensitivity Analysis and Optimization of Undamped Rotor Critical Speeds to Supports Stiffness

Abstract This paper introduced a new approach that employed the assumed-modes method and the receptance method, to the sensitivity analysis and the optimization of rotor-bearing systems. First, the frequency equation in terms of receptances was derived. The natural frequencies and the critical speeds for a typical rotor system were then illustrated. Beginning with the receptance equation, the authors, for the first time, derived a sensitivity matrix and employed it into an optimization process. The topographical method in conjunction with the variable metric method followed for the optimal solution. In the solution process, the sensitivity matrix provided important information for search direction. Examples of critical speeds adjustment via supports change in an optimal sense were illustrated. Numerical results showed that the approach was very efficient and the solutions were very accurate. This approach, in addition, provided such valuable information as which supports dominated specific critical speeds. The developed approach proved to be very helpful to rotor engineers in both rotor modification and rotor design.