Integrated Design and Optimization of Gas Bearing Supported Rotors

The design of direct driven turbomachinery is an interdisciplinary task. Standard design procedures propose to split such systems into subcomponents and to design each one individually. This common procedure, however, tends to neglect the interactions between the different components leading to suboptimal solutions. The authors propose an approach based on the integrated philosophy for designing and optimizing gas bearing supported rotors. Based on the choice for herringbone grooved journal and spiral groove thrust bearings, the modeling procedure for predicting their properties and the linking to the rotordynamic behavior of a generic rotor supported on gas lubricated bearings is provided. The global model for gas bearing supported rotors is linked to a multiobjective optimizer for maximizing the dynamic stability and for minimizing the windage losses of the rotor and of the bearings. Two typical rotor layouts have been included in the optimization. The geometry of a proof of concept system, that has been designed previously using the fragmented component view, is represented as a comparison to the proposed integrated approach. It is shown that the integrated solution allows to reduce the windage losses by 25% or to increase the stability margin by 35%, emphasizing the advantage of the proposed integrated design tool.