Woodruff School of Mechanical Engineering
Mechanical Engineering Seminar
Complex Dynamic Interactions of Multistage, Aeroelastic, and Localization Phenomena in Turbomachinery
Dr. Bogdan Epureanu
University of Michigan
Wednesday, February 29, 2012 at 3:00:00 PM
MRDC Building, Room 4211
Our group is focused on nonlinear dynamics, structural health monitoring, computational and experimental structural dynamics, and aeroelasticity with applications relevant to aerospace and automotive structures, micro-sensors, turbomachinery and combustors, and nano-bio systems. This presentation deals with methods to construct accurate models of realistic industrial turbomachinery. Creating such models requires overcoming several challenges. For example, deviations to the cyclic symmetry of turbomachinery blisks are common due to manufacturing, wear, or foreign object damage. These deviations, called mistuning, are random can lead to dramatically increased forced responses of a few of the blades through a phenomenon known as mode localization. In addition, the dynamics of turbomachinery often exhibits multi-stage effects which must be accurately captured. Moreover, the effects of mistuning and multiple stages interact with the aerodynamics also. The high computational cost associated with predictions for such complex dynamics has led to the development of various reduced order modeling techniques. Two key advancements in this field will be discussed. The first is a new approach for capturing both large and small mistuning. This approach makes use of a new expansion, referred to as the pristine, rogue, interface modal expansion (PRIME). The PRIME basis is a new basis composed of modes computed only from cyclic symmetry analyses. By strategically projecting a finite element model from the physical space onto the new basis, it is possible to accurately and efficiently model large mistuning. In addition, the new method can account for both large and small mistuning simultaneously using an extension of the component mode mistuning approach. The methodology requires only sector-level calculations and thus can be applied to highly refined, realistic models of industrial size. The second advancement which will be discussed is a new methodology to construct reduced order models of multi-stage systems with mistuning that also use only single-sector calculations. The multi-stage models are then coupled to a flow solver to explore the effects of the aerodynamics on the multi-stage response. The methodology consists of first creating efficient structural models, and then iteratively calculating the aerodynamic stiffness matrices for each stage. A variety of numerical and experimental results are provided for single-stage and two-stage industrial rotors, and the accuracy and efficiency of the proposed methods are discussed.
Bogdan I. Epureanu is an Associate Professor of mechanical engineering at the University of Michigan. He received his Ph.D. from Duke University in 1999. His research blends theory and fundamental experiments in nonlinear dynamics, structural health monitoring, aeroelasticity and computational dynamics, with applications relevant to aerospace and automotive structures, micro sensors, turbomachinery, and biological systems. Examples include creating novel mechano-chemical dynamic models of nanoscale transport processes, developing the next generation of highly-sensitive structural health monitoring techniques, discovering novel methods for forecasting the nonlinear dynamics of complex systems, developing innovative reduced order models of complex structures, creating advanced system identification and control methodologies for complex structures and fluid-structural systems. Professor Epureanu has published more than 65 articles in archival journals, more than 75 conference papers and reports. He is also an Associate Editor of AIAA Journal and Journal of Vibration and Acoustics, and serves on the editorial board for Nonlinear Dynamics Journal, and Advances in Mechanical Engineering Journal. He has earned several awards, including the 2004 American Academy of Mechanics Junior Achievement Award, an NSF Career Award in 2004, the 2003 ASME/Pi Tau Sigma Gold Medal Award, the 2001 Young Innovator Award from Petro-Canada, and the 2005 Beer & Johnston Outstanding Mechanics Educator Award by the American Society for Engineering Education.