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The challenges that Rotordynamics will face due to the energy transition

Professor Paolo Pennacchi, Politecnico di Milano, Italy


Professor Paolo Pennacchi is a full professor of Applied Mechanics, Department of Mechanical Engineering, Politecnico di Milano. He was the chairman of IFToMM (International Federation for the Promotion of Mechanism and Machine Science) Technical Committee of Rotor Dynamics (2011-2017) and the president of Italian Society of Tribology (2014-2021). He was the general conference chairman of IFToMM-9th International Conference on Rotor Dynamics (22-25 September 2014, Milan, Italy). He is the president of Italian Scientific Society of Applied Mechanics now. His main research activities are in dynamics of machines, particularly in rotor dynamics and its related topics (especially for dynamics of machines employed for green energy - power generation, cracks in shafts and blades, seals, oil-film bearings), in traction systems for regional and high-speed trains, in diagnostics, identification and prognostics of mechanical systems in general. Further activities are in control of vibrating systems, vehicle dynamics, kinematics and bio mechanics. He has more than 400 scientific publications (books, journals, conferences, patents). He is also the Associate Editors for the journals of Mechanical Systems and Signal Processing (2013-now) and ASME Journal of Engineering for Gas Turbine and Power (2019-2022).

Abstract: In the coming years, a challenge will affect not only industrialized countries, but also in development ones, that is an energy transition, which will see the decrease of importance of fossil -type energy sources in favor of renewable sources of energy and nuclear energy.

Nowadays, the machines used for the production of energy are part of, in the vast majority of cases, the list of rotating machinery, but Rotordynamcis will have to face new problems and challenges, imposed by the energy transition.

In particular, alongside the traditional thermodynamic cycles used for the production of large -scale energy by means of steam turbines (Cycle Rankine) and/or gas (Brayton Cycle), there will be an increase of ORC (Organic-Rankine Cycle) turbines and the introduction of machines that allow the implementation of cycles with higher efficiency, like the Allam-Fetvedt cycle, which need machines that use sCO2 (supercritical carbon dioxide) as the working fluid. Even hydrogen, already used pure or mixed with natural gas as fuel, will be more employed in gas turbines, imposing the development of a new generation of compressors characterized by large flow rates and high rotation speeds.

All this will lead the Rotordynamics to deal with more complex problems in relation to the effects on rotor stability determined by high molecular weight fluids, to the design of the sealing, to the reduction of the use of lubricants of mineral origin in bearings (both of fluid-film type and with rolling elements) and their possible replacement directly with the working fluids, to the solution of the problems of supporting increasingly faster and heavier rotating machines, and to the growing demand for RAMS (Reliability, Availability, Maintainability and Safety).

This keynote lecture will face these problems in detail, also presenting the solutions tested so far.

Tribodynamics based Condition Monitoring via On-Rotor Sensing Technologies

Professor Andrew Ball, University of Huddersfield, UK


Prof Andrew D. Ball is Pro Vice-Chancellor for Research and Enterprise and Professor of Diagnostic Engineering at the University of Huddersfield. He is the founder of the University’s Centre for Efficiency and Performance Engineering (CEPE), created at the University of Manchester, which is the largest independent diagnosis research and development organisation in the world. He is one of the UK’s foremost experts in the fields of machinery diagnostics, dynamic modelling, intelligent computation and vibro-acoustics analysis, with over 30 years of maintenance engineering experience. He is the author of over 300 technical and professional publications in machine diagnosis, non-destructive measurement and related fields, and he spends much of his time lecturing and consulting to industry in all parts of the world. He has been the organizer of several international conferences in condition monitoring and maintenance. He has performed consultancy work for numerous companies, in over 30 countries and across 5 continents. In addition, he acts as an expert witness in court cases and litigations involving machine and structural deterioration or failure.

Abstract: Real-time assessing lubrication performance is a crucial to ensure the efficiency and life-expectancy of various rotating machines. This presentation overviews latest succession in modelling, characterising, sensing and processing the vibro-acoustics responses in hydrodynamic lubrication processes, achieved via On-Rotor Sensing Technologies. It will pave ways to use accelerometers and acoustics emission sensors to achieve a cost–effective real-time monitoring of fluid lubricated various components including mechanical seals, bearings, gears, engines and so on.

Gas seals in the 21st century and their effect on rotordynamic stability

Professor Luis San Andrés, Texas A&M University, USA


Professor Luis San Andrés performed research in lubrication and rotordynamics and advanced technologies for hydrostatic bearings in primary power cryogenic turbo pumps, squeeze film dampers for aircraft jet engines, damper seals for high performance compressors and pumps, and gas foil bearings for oil-free micro turbomachinery. Luis is a Fellow of ASME,  STLE, GPPS, and a member of the Industrial Advisory Committees for the Texas A&M Turbomachinery & Pump Symposia. He earned a MS in ME from the University of Pittsburgh and a PhD in ME from Texas A&M University. Luis has published over 260 peer reviewed papers in various ASME journals and conference proceedings. Several papers were recognized as best in various international conferences. Dr. San Andrés received the ASME 2022 Aircraft Engine Technology Award for sustained personal creative contributions to aircraft engine technology. Learn more about Luis’ work at

Abstract: Gas seals maintain efficiency and power delivery by minimizing leakage but also affect system rotordynamic response and stability. The keynote reviews the experimental record on gas seals and gives insight into the physical models predicting leakage and dynamic force coefficients. The review includes uniform clearance seals, various types of labyrinth seals (LS), honeycomb seals and pocket damper seals. LS with teeth on the rotor surface are notorious for producing large cross-coupled stiffnesses (k). Poorly designed LS are the cause of many rotordynamic instability fiascos. Damper seals produce direct stiffness (K) and damping (C) coefficients, orders of magnitude larger than those from conventional LS. Textured surface seals in conjunction with a swirl brake also produce very small k; hence, effectively removing a concern on rotordynamic instability.

Past are the days for known bad actors, such as LS, being the sole choice for effectively sealing the stages in a turbomachine. Incidentally, damper seals, honeycomb and hole-pattern seals in particular, can produce a large centering stiffness (K>>0 ) that makes a balance piston seal act as a third bearing, hence raising the first natural frequency of the rotor system.

Although both bulk flow and computational fluid dynamics (BFM & CFD) models are very good at predicting seal leakage, they fall short to replicate the experimental force coefficients of seals, those with complex geometry in particular. The predictive methods still need improvement, hence the need of constant and continuous experimental verification. In the 21st century, damper seals offer a remarkable opportunity to control the leakage and tailor the rotordynamic performance and stability of modern rotating machinery.

Theory and technology of vibration and deformation measurement based on microwave sensing

Professor Zhike Peng, Shanghai Jiao Tong University, China


Zhike Peng, who graduated from Tsinghua University, is currently the president of Ningxia University, a distinguished professor of Shanghai Jiao Tong University, and the deputy director of the State Key Laboratory of Mechanical Systems and Vibration. He was awarded the National Natural Science Foundation for Distinguished Young Scholars in 2011, was hired as "Cheung Kong Scholars" by the Ministry of Education in 2015,  and was selected as the "Young and Middle-aged Sci-Tech Innovation Leading Talents" by the Ministry of Science and Technology in 2016.

His current research interests include microwave vibration and sound sensing, nonlinear vibration, signal processing and condition monitoring, and fault diagnosis for machines and structures. He created the generalized parameterized time-frequency transformation theory and method, proposed the nonlinear frequency modulation component decomposition method, and invented a transformative technology of full-field vibration and deformation measurement based on microwave sensing. He has presided over more than 20 important projects, including two aircraft special projects and innovative group projects of the National Natural Science Foundation of China. He has published more than 200 high-level papers and has been included in Elsevier's "China's Highly Cited Scholars List" for 7 consecutive years. He has won the Shanghai Youth Science and Technology Talent Nomination Award, the Ministry of Education's New Century Excellent Talent Support Program, Shanghai Pujiang Talent Support Program, the Ministry of Education's First Prize in Natural Science, the Fujian Provincial Science and Technology Progress Award, and the Chinese Society of Vibration Engineering Youth Science and Technology Award, etc. He is currently a director of the National Science and Technology Innovation Leading Talents Alliance, a director of the Chinese Society of Vibration Engineering, and a chairman of the Dynamics and Control Professional Committee of the Shanghai Mechanics Society. He won the 2019 CM Innovation Award from The British Institute of Non-destructive Testing and was elected as a Distinguished Fellow of the International Institute of Acoustics and Vibration (IIAV) in 2020.

Abstract: Vibration phenomenon is ubiquitous in nature and engineering, and it contains rich physical mechanism and dynamic information. In engineering, vibration measurement and analysis technologies are essential for the design, manufacture and maintenance of major equipment. However, the existing vibration measurement technologies have limitations in terms of measurement accuracy, multi-scale, wide range and environmental adaptability. Particularly, there is a lack of solutions of contactless full-field vibration and deformation measurement for large structures. The emerging approach of vibration and deformation measurement based on microwave sensing has several unique characteristics, including large-range, high-accuracy, multi-scale, full-field synchronization and all-weather measurement capabilities, which has shown significant prospects to be employed in a wide spectrum of applications. This presentation starts with discussing the vibration measurement demands and challenges in engineering, leading to the novel method and approach of microwave sensing-based vibration measurement. Then expound the fundamental principle and key technologies of microwave vibration measurement of single-point, multi-point and full-field, respectively. Furthermore, several typical application cases are shown to demonstrate the performance of the microwave vibration measurement approach. Finally, the microwave vibration measurement technology is summarized and prospected.