Study on the Asynchronous Vibration Components of LE-7A Liquid Hydrogen Turbopump Rotor by Eigenvalue Analysis Considering Rotational Speed Dependency of Rotordynamic Fluid Force

Abstract

For suppression of the development cost and improvement of reliability, dynamic design of fuel turbopump (FTP) rotor loaded on rocket engine is needed. For this objective, finite element model of LE-7A FTP was built, and it well-explained vibration characteristic of the synchronous vibration component in the test data of engine. However, conventional rotor model could not explain the asynchronous vibration occurred in the same test at high rotational speed range. In this paper, rotational speed dependency of rotordynamic (RD) fluid force is focused. RD fluid force acting on impeller shroud was obtained by bulk flow analysis, and its RD coefficients were modeled considering their dependency on rotational speed. Then, these rotational speed dependent RD coefficients were applied in all turbo components: inducer, seal, and turbine. FEM model of LE-7A FTP was improved considering them, and eigenvalue analysis was conducted. This result was compared with test data of engine, and it was confirmed that this FEM model considering rotational speed dependent RD coefficients can explain well the asynchronous vibration characteristics.