Modal Analysis of High Speed Cryogenic Turboexpander

Abstract

Nowadays, rotating machines have a significant role in engineering applications. The requirement of more power for rotating machines leads to higher operating speed which enhances the importance of accurate prediction of the rotor behavior. To avoid the failure, the dynamic characteristics of the rotor have to be studied in the design and development stages. High speeds rotor system is the important machine element in the production. The productivity and the quality of workpieces depended on the dynamic characteristics of a rotor. The study about dynamic characteristics of rotor helps to reduce vibration as well as to avoid the resonance. Determination of critical speeds and unbalance responses are the important parameters for analyzing the dynamic behavior of a rotor system. Finite element method is adopted here for analyzing the designed high-speed turboexpander. It is a useful method to get Campbell diagram and unbalance responses of a rotor system helps to determine the critical speed and to evaluate rotor system dynamics.

This work aims at analyzing high-speed small rotor used in turbo expanders by using finite element method. The obtained result is analyzed by drawing mode shape, response diagram and Campbell diagram by the assistance of MATLAB codes. This work also includes the comparison of results obtained by finite element analysis with the results by transfer matrix method.