Comparison of Different Methods of Non contact Vibration Measurement Procedia Engineering 176 ( 2017 ) 175 – 183 Available online at www sciencedirect com 1877 7058 © 2017 The Authors Published by Els[.]
Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 176 (2017) 175 – 183 Dynamics and Vibroacoustics of Machines (DVM2016) Comparison of different methods of non-contact vibration measurement Lezhin D.S., Falaleev S.V., Safin A.I., Ulanov A.M.*, Vergnano D Samara National Research University, 34, Moskovskoe Shosse,Samara, 443086, Russia Abstract Practical problems of vibration measurement and calculation are considered Different non-contacts methods of vibration measurement (with Polytec® OFV-534 1D laser vibrometer, Polytec® PSV-400-3D scanning vibrometer, ARAMIS® system) and a comparisons between each other and with Finite Element Method modeling (by ANSYS® software) are presented The experiment is fulfilled for high pressure shaft of NK-8 gas turbine engine Difference of middle value for first resonance frequency obtained by three different ways is less than 0.2% only Difference of second resonance frequency is less than 0.4% It means it is possible to use 1D laser vibrometer for measurement of vibration of detail for limited access directly in engine structure, which is more correct ARAMIS® gives a limited but precise picture of deformed shape and simultaneous displacement of all surface points of researched object in the researched place It allows applying of boundary condition for software calculation more correctly © Published by Elsevier Ltd This © 2017 2016The TheAuthors Authors Published by Elsevier Ltd is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of organizing committee of the Dynamics and Vibroacoustics of Machines (DVM2016) Peer-review under responsibility of the organizing committee of the international conference on Dynamics and Vibroacoustics of Machines Keywords: vibration measurement; ANSYS; Polytec; ARAMIS Introduction The solution of the problem of vibration of aircraft gas turbine engine details is currently of great interest Reduction of engine weight and increase of engine parameters at the same time lead to the necessity of large theoretical researches of engine details dynamic [1 – 5], and to the development of different vibration dampers [6 – 11] Today there is an always increasing number of papers, concerned with research and design of dampers for shroud and anti-vibration shelves of aircraft gas turbine engine blades [12 – 17] Choosing correctly the damper structure parameters is necessary to develop calculation methods of engine details dynamic Shells are used widely in stator and rotor of aircraft engine too A calculation of vibration by any software (ANSYS, NASTRAN etc) is simpler and not very expensive However it is difficult to apply right boundary conditions Vibration of separate detail and the same detail in engine 1877-7058 © 2017 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the organizing committee of the international conference on Dynamics and Vibroacoustics of Machines doi:10.1016/j.proeng.2017.02.286 176 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 structure may be different Thus experimental researches are necessary Measurement of vibration is a very important problem Till the present time different contact methods are used for this [18 – 20] However a vibration sensor on the surface of detail changes the picture of detail vibration Problems of measurement are considered separately from problems of modeling [21 – 24] Even if a research uses non-contact method of vibration measurement [25 – 26], there is no comparison of different vibration measurement systems Some of vibration diagnostic systems use simple non-contact methods [27 - 28] but there is no comparison of these systems with more complex and more precise methods Non-contact measurement methods need visual access to the surface of detail Sometimes it is difficult for detail in engine structure Thus a choice of non-contact method for limited access to detail is necessary Of course 3D vibrometer provides more information about detail vibration, but 1D vibrometer can explore vibration of detail directly on engine through technology holes of engine Calculation by ANSYS or other software helps in this case to choice a point of measurement for different modes Some equipment, such as ARAMIS®, is good for measurement of displacement It allows to find correct boundary conditions for software calculation, however it is necessary to check ability of this equipment for measurement of vibration processes Measurement The experiment is fulfilled for high pressure shaft of NK-8 gas turbine engine It has a maximum external diameter of 420 mm and total length of 779.5 mm It has a cylindrical shape and flange-type joints at its two ends, which connect it respectively to the high pressure compressor and the high pressure turbine modules In this experiment, the NK-8 shaft was constrained to a cast iron base, to which the rear flange of the shaft was rigidly anchored with bolts in vertical position For the numerical analysis a 3D model of shaft was developed with the CAD software suite Siemens® NX, then imported on ANSYS® Mechanical A shell-type model of the shaft is meshed with a total of 50000 shell elements, each of them associated with a thickness constant value First used equipment is Polytec® OFV-534 compact sensor head with a laser-Doppler vibrometer (LDV) combined with a CLV-2534 laser vibrometer control unit (it is presented on Figure 1, a) a) b) Fig a - Polytec® OFV-534 vibrometer; b - Polytec® PSV-400-3D scanning vibrometer The OFV-534 design includes a laser unit and a sensor head The laser unit contains a Helium-Neon laser delivering its 633 nm laser light via an optical fiber to a high precision interferometer in the vibrometer head The 177 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 laser beam, with an initial frequency f0, splits into a measurement beam and a reference beam The measurement beam passes through a Brag cell, which adds a frequency shift fb, and is then directed to the target object The back scattered light is shifted slightly in frequency by the Doppler’s effect, adding a frequency shift fd which is function of the displacement velocity of test object A photo detector converts the optical signal created from the interference of the reference beam with the back scattered light into a frequency modulated electrical signal This signal is then sent to a decoder circuit in the vibrometer controller where the signal is converted into a voltage signal proportional to either velocity or displacement Measurements were repeated six times, own mistake of vibrometer is 0.3% The selection of the representative points on the shaft for measurement is a source of problem: besides being completely arbitrary, the points on lobes could be subject to cyclic displacement, so the triggering and synchronization of each measurement should be carefully studied, which is not completely possible with manual triggering Vibration spectrum obtained by Polytec® OFV-534 is presented on Figure Its comparison with calculation results for three first frequencies is presented in Table Table Comparison of experimentally obtained (by OFV-534) and calculated frequencies Experimentally obtained frequency, Hz ANSYS-calculated frequency, Hz Error, % 210.9 204.7 3.03 364 335.5 7.83 526 465.5 11.5 Fig High pressure shaft energy spectrum obtained by single-point vibrometer The second equipment for vibration measurement is Polytec® PSV-400-3D scanning vibrometer It is presented on Figure 1, b It comprises three scanning heads, each with an integrated laser interferometer, scanner and video camera, an instrumentation cabinet with a central computer (junction box) and three data acquisition and control units OFV-5000, one for each scanning head The scanners and data acquisition are controlled and synchronized by the high performance PSV software State-of-the-art 3D graphics are used to visualize the dynamic processes, allowing 3D animated solids with textured surfaces The cameras on the scanning heads give a “stereo” image of the object which has a grid with many points This equipment allows obtaining of the whole energy spectrum of the object The shaker, governed by the control unit, excited the whole spectrum comprised between 50 Hz and 1250 Hz, while the turrets recorded the displacement velocity of each grid point Measurements were repeated six times, own mistake of vibrometer is 0.4% Vibration spectrum obtained by Polytec® PSV-400-3D is presented on Figure Its comparison with calculation 178 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 results for twelve first frequencies is presented in Table Fig Spectrum of high pressure shaft vibration obtained by PSV-400-3D scanning vibrometer Table Comparison of experimentally obtained (by PSV-400-3D) and calculated frequencies ANSYS frequency, Hz Experimental frequency, Hz 204.1 211.7 2x0 335.6 361.7 3x0 ANSYS calculation Experiment result Mode 179 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 441.7 468 2x1 465 521.9 4x0 687.9 689.8 3x1 729.5 734.4 4x1 701 792.2 5x0 180 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 846.7 811.7 5x1 1103 950.8 6x1 1008 1144.5 6x0 1142.8 1189.1 4x2 1140 1215.6 5x2 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 The third equipment is a new photogrammetric measurement suite named ARAMIS®, sold by the German firm GOM It is presented on Figure Fig ARAMIS® cameras and control equipment It comprises high-speed cameras (up to 500 fps in full resolution), supports and calibration hardware, and a data processor connected to computer The object under study needs to be coated with a stochastic color spray pattern, so the image seen by the cameras could be divided into preset “facets” (Fig 5) The elaboration software recognizes the pixels stochastic pattern in the images provided by each camera, and so it can rebuild a 3D image of the object photographed, obtaining not only out-of-plane deformations, but also non-plane strains Thus, ARAMIS® is well suited for static tests, but can also be employed for dynamic tests at low frequencies The first natural frequency of the shaft it is 211 Hz, so the maximum frame rate of the cameras turned out to be just enough to catch about pictures for each oscillation cycle, clearly not enough for describing in detail its modal behavior However it is possible to increase the frame rate of the cameras (up to 2000 fps) by reducing the resolution and consequently the dimensions of the pictures by one fourth It was considered feasible to explore the first natural frequencies, up to about 500 Hz Measurements were repeated six times, own mistake of ARAMIS® is 1.0% Fig Oscillations on the flange part of the shaft at 211 Hz, taken at 2000 fps In spite of a limited size of obtained displacement field, it is enough to compare it with calculation results Comparison is presented in Table 181 182 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 Table Comparison of experimentally obtained (by ARAMIS®) and calculated frequencies Experimentally obtained frequency, Hz ANSYS-calculated frequency, Hz Error, % 211.0 204.7 2.99 362.0 335.6 7.39 ARAMIS® provides exact picture of displacement in any little region of detail, it is useful for understanding of boundary conditions for software calculation Conclusions Comparison of two frequencies obtained by three different ways is presented in Table Frequency Table Comparison of experimentally obtained frequencies (Hz) Polytec® OFV-534 1D vibrometer Polytec® PSV-400-3D vibrometer 210.9 211.7 211.0 364.0 361.7 362.0 ARAMIS® Difference for first own frequency from its middle value is less than 0.2% only, the difference for second own frequency is less than 0.4% It means it is possible to use 1D laser vibrometer for measurement of vibration of detail for limited access directly in engine structure, which is more correct ARAMIS® gives a limited but precise picture of deformed shape and simultaneous displacement of all surface points of researched object in the researched place It allows applying of boundary condition for software calculation more correctly A future development of the present research is estimation of modal condition of detail vibration for limited space access In this case it is possible to choice the point of measurement by software calculation Acknowledgements This work was supported by the Ministry of education and science of the Russian Federation in the framework of the implementation of the Program of increasing the competitiveness of SSAU among the world’s leading scientific and educational centers for 2013-2020 years References [1] A.I Ermakov, A.V Urlapkin, The influence of a blade vibrations connectivity on a degree of disturbance of turbine wheels rotation symmetry Research Journal of Applied Sciences (11) (2014): 800-805 [2] A.I Ermakov, A.V Urlapkin, D.G Fedorchenko, The features of resonance stress scatter in turbine wheels with a weak connectivity of blade vibrations Research Journal of Applied Sciences, (11) (2014): 795-799 [3] D.P Davidov, A.I Ermakov, Blade wave finite element Research Journal of Applied Sciences (11) (2014): 849-854 [4] Y Kaneko, K Mori, H Ohyama, Effect of material damping of steam turbine vane on flutter suppression Proceedings of the ASME Turbo Expо, Volume 7, Issue PARTS A AND B (2012): 1161-1168 [5] K.V Savchenko, A.P Zinkovskii et al Influence of the Orientation of Shroud Contact Surfaces on the Static Stress State of Turbine Rotor Blades Strength of Materials 46 (4) (2014): 493-502 [6] S Falaleev, A Vinogradov, Concept of combined gas-dynamic mechanical seal and discharge device of aircraft engine rotor support ARPN Journal of Engineering and Applied Sciences (10) (2014): 1842-1848 [7] D.K Novikov, Development of Squeeze Film Damper Characteristics Calculation Methods Which Take Into Account a Liquid Inertia Forces Research Journal of Applied Sciences, (10) (2014): 649-653 [8] S.V Falaleev, K.N Chaadaev, D.S Diligenskiy, Selection of the hydrodynamic damper type for the turbomachine rotor Life Science Journal 11(7) (2014): 502-505 [9] S.V Falaleev, V.B Balyakin, Application of a hydrogasdynamic axial vibration damper for reducing GTE vibration Russian Aeronautics 57(3) (2014): 314-318 [10] G.V Lazutkin, A.M Ulanov, K.V Boyarov, Comparison of mechanical characteristics of vibration isolators made of wire pressed materials International Journal of Engineering and Technology 6(5) (2014): 2201-2208 [11] A.M Ulanov, S.V Bezborodov, Life-time of vibration insulators made of metal rubber material under random load Research Journal of Applied Sciences (10) (2014): 664-668 D.S Lezhin et al / Procedia Engineering 176 (2017) 175 – 183 [12] R.Q Wang, W.L Si, D.Y Hu, A method for the calculation of dynamic response considering joint dry friction Applied Mechanics and Materials, 437 (2013): 152-157 [13] C.M Firrone, T.M Berruti, M.M Gola, On force control of an engine order-type excitation applied to a bladed disk with underplatform dampers Journal of Vibration and Acoustics, Transactions of the ASME 135 (4) (2013): 041103 [14] A.A Ferri, W.E Whiteman, Stability analysis of a vibrational system subject to negative viscous damping and displacement-dependent dry friction damping Proceedings of the ASME Design Engineering Technical Conference, Volume B (2003): 1559-1568 [15] M.M Gola, C Gastaldi, Understanding complexities in underplatform damper mechanics Proceedings of the ASME Turbo Expo (2014): 7A [16] C.W Schwingshackl, E P Petrov, D W Ewins, Effects of Contact Interface Parameters on Vibration of Turbine Bladed Disks With Underplatform Dampers Journal of Engineering for Gas Turbines and Power Vol 134 (2012): p [17] S Tatzko, L Panning-von Scheidt, J Wallaschek, A Kayser, G Walz, Investigation of alternate mistuned turbine blades non-linear coupled by underplatform dampers Proceedings of ASME Turbo Expo 2013: Turbine Technical Conference and Exposition June 3-7, 2013, San Antonio, Texas, USA (2013): 12 p [18] D Biermann, A Zabel, T Brüggemann, A Barthelmey, A comparison of low cost structure-borne sound measurement and acceleration measurement for detection of workpiece vibrations in 5-axis simultaneous machining Procedia CIRP, 12 (2013): 91-96 [19] M Watanabe, H Iki, K Sakamoto, Y Uriu, Y Kado, Analysis of turbine generator shaft torsional vibration caused by self-commutated converters IEEJ Transactions on Power and Energy 134 (11) (2013): 900-907 [20] Alok Sinha Reduced-Order Model of a Bladed Rotor With Geometric Mistuning J Turbo, vol 131 (3) (2009): 199-207 [21] J Zhai, H Zhang, Q Han, D Wang, Y Liu, Modeling and experiments of rotor system with oil-block inside its drum cavity Journal of Vibroengineering, 150 (4) (2013): 1972-1982 [22] J Cheng, Y, Wang, C.J Cui, Finite element dynamic analysis of the shafting of transmission-laser-scanning-emitter Advanced Materials Research, 697 (2013): 190-193 [23] S.A.A Hosseini, S.E Khadem, Free vibrations analysis of a rotating shaft with nonlinearities in curvature and inertia Mechanism and Machine Theory 44(1) (2009): 272-288 [24] S Braut, R Žigulić, M Butković, Numerical and experimental analysis of a shaft bow influence on a rotor to stator contact dynamics Strojniski Vestnik/Journal of Mechanical Engineering 54 (10) (2008): 693-706 [25] X Qian, G Lin, X Du, Vibration measurement and data analysis of a spinning shaft using a camera-based motion analysis system Applied Mechanics and Materials, 29-32 (2010): 203-208 [26] Adolfo Senatore Measuring the natural frequencies of centrifugally tensioned beam with laser doppler vibrometer Measurement Techniques, 39 (2006): 628-633 [27] Yu, M., Guo, J., Lee, K.-M Strain field sensing and reconstruction for a thin-wall plate IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM 2016 – September, 7576864 (2016): 788-793 [28] Goyal, D., Pabla, B.S Development of non-contact structural health monitoring system for machine tools Journal of Applied Research and Technology, 14 (4) (2016): 245-258 183 ... uses non- contact method of vibration measurement [25 – 26], there is no comparison of different vibration measurement systems Some of vibration diagnostic systems use simple non- contact methods. .. methods [27 - 28] but there is no comparison of these systems with more complex and more precise methods Non- contact measurement methods need visual access to the surface of detail Sometimes it is difficult... – 183 structure may be different Thus experimental researches are necessary Measurement of vibration is a very important problem Till the present time different contact methods are used for this