Session: 05-04 Structure & Dynamics

Paper Number: 76448

Start Time: December 3, 2021, 04:00 PM

76448 - Harmonic Analysis of the High Speed Direct Coupled SCO2 Turbo-Generator 

The high-speed direct-coupled supercritical carbon dioxide (sCO2) turbo-generator is being developed for the sCO2 Brayton cycle test loop facility at IISc Bangalore. The design speed of the turbine-generator pair is ~60,000 rpm. The rotor includes a turbine impeller, induction generator rotor, thrust collar, and rotating sleeve of the dry gas seal. Due to the differential pressure across the impeller surfaces, the shaft is subjected to a significant thrust load. The shaft is supported using 3+2 combination of taper roller bearings to accommodate both thrust and radial forces. The bearings are mounted on the shaft in 3+2 tandem-back to back-tandem (TBT) configuration.

This paper presents the rotordynamic and harmonic analysis of the rotating components using ANSYS finite element solver. Preliminary rotordynamic analysis of the 40 kW sCO2 turbo generator is performed using the AxSTREAM-Rotordynamics module. This is followed by bearing selection analysis using SKF SimPro Expert. The geometrical parameters such as rotor length, diameter, bearing locations are arrived at to maintain enough separation margin between the operating and critical speeds. The selected bearing and shaft configuration is analyzed using ANSYS to predict the critical modes and shaft deflection. The forces at the bearing locations and deflections at various locations of the shaft have been estimated using harmonic analysis. In the absence of an active damper, only material damping (ζ = 0.01 - 0.05) has been considered. This paper also describes the effect of the damping ratio and balancing grades on the bearing forces and deflection of the rotor.

Presenting Author: Ashutosh Patel Indian Institute of Science