Dr. Dara W. Childs
Mechanical Engineering Department
Texas A&M University
Biography Dr. Dara Childs retired from Texas A&M University in January 2018 as the Leland T. Jordan Chair of Mechanical Engineering at TAMU. He did his BS (1961) and MS (1962) at Oklahoma State University in Civil Engineering. He completed his PhD in Engineering Mechanics at the University of Texas in 1968. He worked for Rocketdyne division of North American Aviation (1962-1965), Colorado State University (1968-1971), The University of Louisville (19710- 1980), and Texas A&M University, Department of Mechanical Engineering from 1980 until his retirement. He became the Director of the Turbomachinery Laboratory at TAMU in 1984. He is the author of three books and over 100 Journal papers. He has received five best-paper awards from ASME.
The Remarkable Turbomachinery-Rotordynamics Developments During the Last Quarter of the 20th Century
Rotordynamics developed from the beginning of the 20th century to deal with problems associated with steam turbines. This paper deals with intense developments starting around 1975 through 2000 in rotordynamics to deal with new, larger machines running at higher speeds and higher power levels. Most of the new problems of interest dealt with subsynchronous instabilities. Issues associated with “synchromnously unstable” motion due to the Morton Effect are also reviewed.
This presentation is based on the SAE paper, Childs, D., “The Remarkable Turbomachinery-Rotordynamics Developments During the Last Quarter of the 20th Century,” SAE Technical Paper 2015-01-2487, 2015, doi:10.4271/2015-01-2487. It was prepared and delivered as part of the 2014 SAE Garrett CLIFF GARRETT TURBOMACHINERY ENGINEERING AWARD
Dr. Kshitij Gupta
Mechanical Engineering Department
Indian Institute of Technology (IIT) Delhi
New Delhi, INDIA 110016
Fellow, Indian National Academy of Engineering (INAE) http://web.iitd.ac.in/~kgupta
Biography Dr. Kshitij Gupta is currently Emeritus Professor of Mechanical Engineering at IIT Delhi. He received his bachelors and masters degrees in Mechanical Engineering from IIT Kharagpur, and his Ph.D. degree in 1979 from IIT Delhi. He began his teaching career from IIT Roorkee (1977-80) and has been at IIT Delhi ever since. He was appointed Professor in Mechanical Engineering in 1990, and was BHEL Chair Professor (2002-04, 2005-08). He was head of Tribology Center (ITMMEC), and of Mechanical Engineering Department, Dean of Post Graduate Studies & Research, and a Member of Board of Governors of IIT Delhi. He retired in 2016 from the position of Director, IIT Delhi. His teaching and research interests are in Vibrations, Rotordynamics, Composite and Smart Material applications, Acoustics and Mechanical Design. His early research was on aeroengine rotor and blade dynamics, where he contributed to an indigenous aero gas turbine development program. Subsequent research encompasses several areas i.e., condition monitoring, cracked rotors, non-linear effects, non-metallic (composite) and smart rotors. He has published extensively in the above areas and has co-authored a book on ‘Mechanical Vibrations’.
He has been involved with several International projects such as the multi-institutional EC project on Sound and Vibration (CIRCIS 2006-2009), and in organization of several conferences and symposia, notable amongst them are the two Indo-US symposia (INDUSVAN 1996, 2001), two IUTAM Symposia (INSODYD 1998, IUROTOR 2009), and VETOMAC-VI in 2010. He is a fellow of Indian National Academy of Engineering (INAE), and member of IFToMM Technical Committee on Rotor Dynamics (TCRD).
Smart Materials in Development of Rotors – Applications and Challenges
Recent research has established the feasibility of using smart materials in development of rotors. From the large variety of smart materials available, for rotors applications mainly three materials namely the shape memory alloy (SMA), the magneto-rheological fluid (MRF) and the piezo-electric patches (PZT) have been reported in published literature. The present state of research can be considered to be in a nascent stage, nevertheless it paves the way for development of ‘smart rotors’. The present lecture will be in three parts. In the first part various types of smart materials and their relevant characteristics will be explained briefly. Current state of the art on rotor vibration control using smart materials will be presented along with a historical background. Primarily three smart materials i.e., the SMA, MRF, and the (PZT) in their individual application modes will be discussed. Potential benefits of MRF in squeeze film dampers (SFD) of turbomachines will also be examined. Advantages and limitations of each of these three materials will be brought out. In the second part, some ideas as to multiple smart material (MSM) applications for rotor vibration control will be presented. The emphasis will be towards the complementary use of various smart materials. The possibility of using other than these three smart materials in rotors will also be examined. These ideas will be enumerated through an example of a proposed smart helicopter tail rotor both in its metallic and the fiber reinforced composite (FRP) versions. The third part of the lecture will introduce an ultra smart rotor (US-RTR). The objective would be to explore the limits of US-RTR, likely challenges in its realization for various applications, and the directions for future research.
Dr. Rainer Nordmann
Emeritus Professor Mechanical Engineering
TU Darmstadt and Fraunhofer Institute LBF
64285 Darmstadt, Germany
Biography Rainer Nordmann studied Mechanical Engineering at TH Darmstadt and then undertook PhD research in Rotor Dynamics at the Machine Dynamics chair of TH Darmstadt. He was appointed Professor of Machine Dynamics at University of Kaiserslautern in 1980, teaching Machine Dynamics and Control. His research areas included Rotor Dynamics with applications to Turbomachinery. In 1996 he became Professor for Mechatronics in Mechanical Engineering at TU Darmstadt. His research activities at TU Darmstadt were concentrated on the development of Mechatronic Systems with applications to Rotating Machinery, Machine Tools and Automotive Systems. He was involved in several special domain research projects and supervised more than 100 PhD students. The methods and results of the research projects were published in several papers in international journals and presented at national and international conferences. Rainer Nordmann is coauthor of the two Springer books Rotordynamik and Magnetic Bearings. He served also as Dean of Mechanical Engineering.
After his retirement Rainer Nordmann worked from 2009 to 2012 as manager for Rotor Dynamics in the international R&D Center of Alstom Power in Baden (Switzerland). From 2009 until 2016 he was Chairman of an ISO Working Group “Rotor Dynamics and Vibrations of Machines” and from 2006 until 2011 Chairman of the IFToMM Technical Committee Rotor Dynamics. Today he is consult for the Fraunhofer Institute for Structural Durability and System Reliability LBF in the area of Adaptronics. He is involved in other consulting activities for different companies in the area of Rotor Dynamics and Mechatronics.
Modelling, Monitoring and Vibration Control for High Performance Turbomachinery
In order to support the design process of High Performance Turbomachinery with respect to a safe and reliable operation, lateral as well as torsional vibrations are calculated by means of powerful numerical tools. This includes the determination of eigenvalues (natural frequencies, modes and stability) and the vibration amplitudes of the unbalance response for lateral vibrations as well as the shaft stresses and torques due to electrical faults for torsional vibrations. It is well known that the dynamic behavior of a shaft train not only depends on the external excitations and the dynamic characteristics of the rotating parts, but also on some important interaction effects, e. g. Rotor Structure Interaction (Foundation, Casing), Rotor Fluid Interaction (Bearings and Seals), Rotor Blade Interaction (e.g. Last Stage Turbine Blades), Thermomechanical Interaction (Spiral Vibrations due to Rubbing) and Electromechanical Interaction (Electrical Air Gap torques). As a consequence multi-physical methods with tools from different disciplines are necessary. Some of the methods and tools, which are used for the described tasks are: Finite Elements (FE) for Structural Dynamics, Computational Fluid Dynamics (CFD), Electro Dynamics and Heat transfer. Furthermore Reduction methods, Modal Analysis, Identification and Sensitivity Analysis are also of importance. Modelling for Simulation is therefore an important first task for the mechanical engineer. The keynote lecture will present some of the scientific methods and tools, which have been developed and used for typical interaction effects, influencing the dynamic behavior.
When a Turbomachine goes into service, the user expects a stable long term operation with acceptable vibration values. This important second task can be achieved by means of known Monitoring Systems, consisting of sensors and suited signal processing units. Vibrations can be measured and evaluated by features, where Vibration Standards (e.g. ISO or API) can be used for this evaluation. In the keynote some extended Monitoring possibilities will be presented, which may improve the diagnosis for failures. If for example not only vibration responses (system output) are measured, but also excitation forces (system input) via active elements (AMB’s or Piezos), Frequency Response Functions (FRF) can be determined. They tell much more about the dynamic behavior of the rotor system. By comparison of measured and simulated vibration values possible parameter changes can be identified (Diagnosis). In this way the developed model for the dynamic behavior of the Turbomachine can run in parallel to the real system as a digital twin (Model Based Monitoring).
If vibrations in operation do not fulfil the expected behavior, Vibration Control is needed, in order to bring the vibration values back to acceptable values. Classical solutions of vibration control can be subdivided into: reduction of excitation , tuning of system parameters, damping enhancement, vibration absorption and isolation. These solutions can be applied either passive, semi-active or active. A good dynamic model is again very helpful to find optimal solutions. In the keynote some examples will be presented, controlling the vibrations of Turbomachines by using passive solutions (Balancing, Squeeze Film damper) and active solutions (AMB’s and Piezo-Actuators) as well.
Dr. Robert B. Randall
School of Mechanical and Manufacturing Engineering
University of New South Wales (UNSW)
Sydney, Australia 2052
Biography Bob Randall is a visiting Emeritus Professor in the School of Mechanical and Manufacturing Engineering at the University of New South Wales (UNSW), Sydney, Australia, which he joined as a Senior Lecturer in 1988. Prior to that, he worked for the Danish company Brüel & Kjær for 17 years, after ten years’ experience in the chemical and rubber industries in Australia, Canada and Sweden. His book “Frequency Analysis”, published by Brüel & Kjær in 1977 with a new edition in 1987, was widely distributed around the world. He was promoted to Associate Professor in 1996 and to Professor in 2001, and was made an Emeritus Professor on his retirement in 2008. He has degrees in Mechanical Engineering and Arts (Mathematics, Swedish) from the Universities of Adelaide and Melbourne, respectively. He is the invited author of chapters on vibration measurement and analysis in a number of handbooks and encyclopedias, and a member of the editorial boards of four journals. His book Vibration-based Condition Monitoring was published in 2011 by Wiley. He is the author of more than 300 papers in the fields of vibration analysis and machine diagnostics, and has supervised seventeen PhD projects in those areas. From 1996 to 2011 he was Director of the DSTO (Defence Science and Technology Organisation) Centre of Expertise in Helicopter Structures and Diagnostics at UNSW, with the main effort on diagnostics and prognostics of gears and bearings in helicopter gearboxes and gas turbine engines. He is still active in research, for example being a co-author of fourteen journal papers in the last two years.
The Advantages of Non-causal Signal Processing for Machine Diagnostics
It is not uncommon for techniques developed in another field to be applied in machine condition monitoring and diagnostics. An example is speech analysis, where the signals have many similarities to machine vibration signals; forcing functions are a mixture of near periodic functions (voiced sounds) and noise (unvoiced sounds) and signals are modified by a transfer function before being measured. However, it is most common for speech signals to be processed in real-time (for communications and automated translation, for example), whereas this is not a requirement, and is in fact a disadvantage for machine diagnostics. This is because real-time processing requires the use of causal signal processing techniques, which introduces undesirable features, such as phase distortion and non-ideal filter characteristics. It often means that much processing has to be done by convolutional processes in the time domain, for example filtering, differentiation/integration, and Hilbert transforms, which can be achieved much more efficiently using non-causal (FFT) techniques switching between the time and frequency domains. Machine diagnostics is about getting advance warning of impending failure, giving time to take counter-measures, so there is no advantage in getting results in real-time, the delay in any case usually being less than a second. Even in online monitoring of critical machines, purely to be able to shut them down in the case of a sudden change, it usually takes longer than this to make a decision, or for the speed to reduce when they are shut down. This paper gives a number of examples of the considerable advantages in using non-causal processing for machine diagnostics, for example zero phase shift ideal filtering, and error-free demodulation and differentiation/integration.