Laboratory of Rotational Laser Vibrometry

Department:   Department D 3 - Dynamics and Vibration
Head:   Ing. Pavel Procházka, CSc.

Research and development of equipment and methods for non-contact measurement of vibrations of rotating blades of machines are based on the need of the energy and aerospace industries to prevent accidents on expensive equipment - turbines of energy machines, large fans, compressors and aircraft engines. The blades of these machines are exposed to extreme stress due to centrifugal forces, and additive low-cycle and high-cycle vibration-induced fatigue cycles can cause fatigue damage to the blades with subsequent breakage. Devices for monitoring the condition and vibration of blades developed in the Laboratory have found application at the Temelín, Prunéřov, Počerady power plants. Interest in their use also comes from around the world, negotiations are taking place with companies from Great Britain, Vietnam, Finland and South Africa. One of the facilities was operated in Martinique (France).


Ing. Pavel Prochazka, CSc., research scientist, head of the Laboratory. Conceptual work, research of magnetoresistive sensors of blade passage, research of intelligent contactless sensors, development of vibrodiagnostic systems.

Ing. Dušan Maturkanič, Ph.D., associate scientist. Research of measuring techniques and data processing methods, research of uncertainties of time methods of vibration measurement, optimization of mathematical processes.

Dr. Mohammed Lamine Mekhalfia, research assistant. Design and strength calculations of mechanical parts, calculations of frequency characteristics of elements of measuring systems, construction of electromechanical devices.

Ing. Evgenyia Voronova, research assistant. Experimental research of rotating elements, measurement and data collection, processing of measured values.

Robert Hodboď, specialist. Construction of mechanical and electrical equipment, development and construction of contactless sensors, measurement and data acquisition.

The Laboratory was established in 2015 under the support of the EU project "Laboratory of the Rotational Laser Vibrometry" No. CZ.2.16/3.1.00/21359 of the Operational Programme Prague Competitiveness. The determination of the Laboratory is the research and development of non-contact vibration diagnostic systems of rotating blades of high power turbomachines, compressors and fans. The Laboratory is equipped by a test rig with a model turbine wheel and a scanning Laser Doppler Vibrometer with a derotator. An important advantage of the blade vibration measurement in this configuration is the usage of two distinct measuring and analytical methods: Blade Tip Timing and Laser Doppler Vibrometry. These methods allow practically independent data evaluation from different measurement systems. Moreover, two opposite blades are equipped with strain gauges providing additional information about blade straining during rotation. Maximal speed of the wheel is 7,000 rpm. The Laboratory is unique in the Europe. Its features predispose the utilization of the research results in power industry and engineering.

In 2015-2020, a group of scientists and researchers of the Laboratory solved the project Vibrodiagnostics of rotating blades of rotary machines in power engineering; programme VP03 - Effective energy conversion and storage, Strategy of the Academy of Sciences AV21. The aim of this project was to interconnect the scientific fields of electrical engineering, mechatronics, mechanics and mathematical statistics for the development of vibrodiagnostic systems of rotating blades of rotary machines in power engineering with an initial focus on reliability and efficiency of low-pressure steam turbine stages. In this project a mathematical model was developed to optimize sensing vibration and stationary deflections of rotating turbine blades. Methods have been developed for statistical evaluation of alternative blade vibration shape models determined from experimental data and the selection of the model with the highest probability.

The theoretical questions of measurement and evaluation of vibrations of turbomachines during rotation were solved. Special magnetoresistive sensors have been developed for this purpose. The aim was to increase the sensitivity, accuracy, resolution and frequency range of these non-contact vibration sensors. A number of top results have been achieved in this respect. For example, these sensors are able to detect 10 μm rotating blade deflections at a peripheral speed of 700 m / s. Also unique is the frequency bandwidth, which extends not only to high frequencies above 300 kHz, but also covers the DC band. Thus, the sensors can be used statically to measure a number of significant static turbine characteristics. Many of these principles have therefore been protected as a utility models or patents.

In 2019 - 2020, the Laboratory is part of a consortium solving the project "National Center of Competence Cybernetics and Artificial Intelligence", ID TN01000024 of the Technology Agency of the Czech Republic. The solved sub-project "Robotic Operations in Hazardous Environment and Intelligent Maintenance" is realized through cooperation with companies in the form of collaborative research. In this project, the researchers of the Laboratory investigate measurement methods and intelligent sensors for sensing vibrations of the blades of rotating machines at remote sites. Companies in Vietnam and South Africa have already shown interest in these sensors.

Methods and program functionalities have been developed for the calculation of advanced blade vibration characteristics from experimental data: frequency analysis of the instantaneous blade vibration state, statistical overviews of dynamic and static characteristics, residual lifetime analysis, graphical presentation of data and calculation results. The prototype of the vibrodiagnostic device was realized and verified on the model test wheel of the Laboratory, in the test rig Doosan Skoda and also on real steam turbines. The system developed in the Laboratory was used in cooperation with Doosan Skoda and West Bohemian University at the combined gas-steam power plant Pocerady on a turbine 280 MW for monitoring vibrations of blades 1220 mm. Measuring was completed after three years of faultless operation. The Blade Tip Timing system of a new concept developed in the Laboratory was used to measure vibration on a 35 MW condensation steam turbine in Martinique, where it was in operation for two years.

Currently (2019 -2021), the researchers of the Laboratory are solving the project EU H2020 "Batista - Blade Tip Timing System Validator", ID 862034, Call Clean Sky 2. The consortium set up for this project has EMTD (Coordinator - GB) and the University of Manchester (GB) as further members. SAB (Safran Aero Boosters - BE) is engaged in the project as a supervisor. The aim of the project is theoretical and experimental research for validation of systems based on the Blade Tip Timing method.

International cooperation:

In addition to domestic companies, the laboratory has wide international cooperation with research and educational institutions abroad. Now they are mainly the aforementioned institutions EMTD (GB), University of Manchester (GB) and SAB (BE), which runs the very active cooperation on the project H2020. There is also a very lively cooperation with Italian universities, in particular the Polytecnico di Torino, University of Perugia, University of Ancona and University of Roma (all IT). An active cooperation also takes place with ITWL (Air Force Institute of Technology - PL). We visit each other and exchange scientific information. In 2019, a proposal for another EU project H2020, together with the Politecnico di Torino (IT), University of Perugia (IT), ITWL (PL), University of Twente (NL), KU Leuven (BU) and parters like Czech Technical University (CR), Siemens (BE), Safran Helicopter Engices (FR), Safran Aircraft Engices (FR), Rolls Royce (GB), and others, was drawn up and submitted at the beginning of 2020. This project H2020 "Thrust - Tip Timing Enhancing the Robustness and Training for Safety in Turbomachinery" falls under the call Clean Sky 2. This project is focused on working in interdisciplinary fields: construction of sensors, signal processing, and structural analysis of the bladed discs of the aircraft engines. The objective is also to train a new generation of 11 Early Stage Researchers in managing sophisticated measurement techniques as the Blade Tip Timing. The project received a good evaluation, but was not accepted for funding in 2020. Submission will therefore be repeated in 2021.

Publications:

  • 6 articles in international journals with impact factor, 5 of them in IEEE Transactions on Instrumentation and Measurement (imp. fact = 3.067).
  • 1 part of book monograph: Vibrodiagnostics of steam turbine blades.
  • 7 presentations at international conferences: I2MTC 2015 Pisa (IT), AIVELA 2016 Ancona (IT), ICEM 2016 Rhodes (GR), I2MTC 2017 Torino (IT), ENBIS 2017 Naples (IT), I2MTC 2018 Houston (USA), ICEEE 2019 Paris (FR).
  • 6 presentations at national conferences.
  • 4 patents granted, 1 utility model granted, 2 patents pending.

The equipment of the Laboratory consists of:

  • a rotary model of a turbine bladed wheel with an electric motor drive and regulation
  • a vacuum chamber of the rotating wheel eliminating aerodynamic forces and friction heating
  • an electromagnetic vibration exciting system with a software control
  • a non-contact tip-timing measurement system of circumferential displacements of the blades
  • a calibrated strain-gauge system with a slip-ring transmission
  • a Laser Scanning Vibrometer Polytec PSV-500 with a derotator
  • a reference Vibrometer Polytec OFV-5000

The measurement system is equipped with eight pairs of electromagnets for a computer controlled vibration excitation in the axial and radial directions. The excitation function can be either direct, harmonic or impulse. The entire model wheel, including sensors and electromagnets, is enclosed by a pressure-resistant glass front wall. Two vacuum pumps decrease the air pressure in this chamber down to 5 mbar, so that conditions near to vacuum can be created.