Session: 27-05 Non-Linear Rotordynamics

Paper Number: 121480

121480 - Case Study of User Defined Element Integration in Rotor Dynamics Software 

Gas turbine engine companies often employ home-grown or internally developed computer programs for rotor dynamics design-analysis.  Developing, and maturing these sometimes over decades to support day-to-day design execution and some of the more specialized problems in Rotor Dynamics.  As some problems now require higher fidelity modeling or visualization, along with the incorporation of more physics-based capabilities, the employment of commercially available, general use software becomes attractive to predict general engine dynamic behavior with these additional features.

In 2010, Vance et al. [1] corrected the record and informed us that the first Squeeze-Film Damper (SFD) was invented by Sir Charles Parsons in 1889 and incorporated into the first practical steam turbine. Most commercial software is using the formulation given by Adam et al [2] which includes an overall solution strategy for a SFD software package ready for FE implementation.  They have performed the benchmarking using the SFD/ADINA combined with numerous relevant example-problem solutions.  An SFD/flexible rotor test rig was also developed.  At that time, the necessary approach and methods had been developed, proven, and demonstrated by their work.  Later Zeidan et al. [3] summarized the history of SFDs since 1960’s and discussed major technical issues for their integration into turbomachinery, including oil cavitation vs. air ingestion and fluid inertia effects. These are not included in the most of the SFD commercial codes available today.  San Andrés [4] has further developed the code, which includes the limitation mentioned in the previous research work.  Having the ability to model complex and nonlinear features such as the SFD discussed as well as others, like thrust dependent bearing stiffness [5] and observed response such as side-banding due to over stress bearing[6], is important to predicting rotor dynamic system behavior accurately. 

 Three case studies are presented in this paper, namely (1) squeeze file dampers with inertia terms in addition to conventional stiffness and damping, (2) thrust dependent bearing stiffness in transient analysis and (3) the explanation of side-banding in the response utilizing transient analysis solutions.  The approach described in this paper seeks to make use of already proven general finite-element nonlinear analysis (transient and harmonic analysis) which are available in the market.  This process of integration will allow us to include system nonlinearities (particularly at the bearings and dampers) appears to be necessary if analytical predictions are to be realistic. The work is applied to Nelson-McVaugh model to validate for squeeze file damper element for harmonic analysis.  This paper will be useful for the end user for implementing and enhancing the capability in house as well as commercial software where user defined element is possible. 

References

1. Vance, J., Zeidan, F., and Murphy, B., 2010, Machinery Vibration and Rotodynamics, John Wiley and Sons, NY, Chapter 5.

2.  Adams, M. L., Padovan, J., Fertis, D. G., “Engine Dynamic Analysis with General Nonlinear Finite-Element Codes” NASA Contractor Report 187222. 

3.       Zeidan, F., L. San Andrés, and J. Vance, 1996, "Design and Application of Squeeze Film Dampers in Rotating Machinery," Proceedings of the 25th Turbomachinery Symposium, Turbomachinery Laboratory, Texas A&M University, September, pp. 169-188.

4.       San Andrés, L., Savela, Gregory, Sung-hwa Jeung, and Sean Den, “SQUEEZE FILM DAMPERS: AN EXPERIMENTAL APPRAISAL OF THEIR DYNAMIC PERFORMANCE,” Asia Turbomachinery and Pump Symposium Singapore, February 22-25, 2016.

5.        Fleming, David P., Murphy, Brian T., Sawicki, Jerzy T., and Poplawski, J. V. “Transient Response of Rotor on Rolling-Element Bearings with Clearance”, NASA/TM—2006-214408, October 2006.

6.        Ehrich, F.F.  “Some Observations of Chaotic Vibration Phenomena in High Speed Rotodynamics”, Transaction of ASME, Vol. 113, 50-57, January 1991

Presenting Author: Parag Mathuria Pratt & Whitney

Presenting Author Biography: Parag Mathuria is Rotodynamics Practitioner at Pratt and Whitney since 2016. He has accumulated extensive experience in 25+ years in the field of Mechanical engineering specialized in vibration. He earned Bachelor and Master degree in Mechanical engineering from Shivaji University, India and PHD in Mechanical Engineering from IIT Bombay. He has published 18+ Journal and conference papers in the area of sound and vibration and two patents. His most recent endeavors have been to perform the rotodynamic analysis in APU, Aero-engine and Rigs using experimental and analytical tools.

Authors:

Parag Mathuria Pratt & Whitney
Gregory Savela Pratt and Whitney