Kálmán Kandó Doctoral School of Transportation and Vehicle Engineering  

Department of Aeronautics, Naval Architecture and Railway Vehicles (VRHT)

Supervisor: Dr. Veress Árpád

Filling Process Analysis of Viscous Torsional Vibration Dampers

Introducing the research area

Viscous torsional vibration dampers are used to reduce the amplitude of harmful torsional oscillations on the crankshaft of high-performance internal combustion engines and to prevent fatigue damage of engine parts. The operation of this damping device is based on the viscosity change of the silicone oil contained in the device, the magnitude of which depends mostly on the shear rate and the temperature. The aim of the research is to measure the rheological properties of the oil and to develop a material model, which can be used to cost-effectively analyze, improve and optimize the filling process and operation of this damper with help of advanced fluid dynamic simulations. The accuracy of the numerical results can be verified by neutron radiography measurements performed in the framework of the research. As a result of the work, the development and production time and the cost can be reduced not only for torsional vibration dampers, but also of all equipment with using the same silicone oil as working fluid.

Brief introduction of the research place

BME VRHT participated in hundreds of industrial research projects and tenders in the area of “Technical Calculations and its Applications in Vehicle Engineering”. In the present research, it cooperates with the Bay Zoltán Institute for Applied Research, the Budapest Neutron Centre of the Hungarian Academy of Sciences, Knorr-Bremse Fékrendszert Kft. and Hasse & Wrede.

History and context of the research

In the design of nowadays’ modern internal combustion engines, a trend can be observed that involves reducing the size of the engine and the speed of the driven shaft. As a result, the transmitted torque and the load on the engine’s crankshaft are significantly increased. During engine operation, harmful oscillations can occur on the shaft, of which torsional oscillations are the most dangerous. This phenomenon not only reduces the engine power and increases fuel consumption but can also lead to the fatigue of the engine and its components transmitted through the drive train. [1] The Knorr-Bremse Group’s Berlin-based market-leading cooperative competence centre, Hasse & Wrede has been designing, developing, manufacturing and marketing torsion vibration dampers for decades. By using a torsional vibration damper (see Figure 1), the life of the engine can be extended by making the rotation of the crankshaft more oscillation-free. The viscous version of these vibration dampers exerts a damping effect based on the non-Newtonian viscoelastic properties of silicone oil. The damping characteristics of the silicone fluid, in particular the viscosity of the fluid, change due to the effect of stress (shear) and temperature, which must be taken into account for both production and operational use.

 

Figure 1: Structure of a viscous torsional vibration damper [2]

The research goals, open questions

The aim of the present research is to i.) have a deeper understanding of the operation and filling process of viscous torsional dampers, ii.) perform parameter sensitivity analysis for affecting physical phenomena, iii.) adjust the parameters with significant effect on accuracy or/and on process optimization.

To achieve the goals, it is necessary to perform 1.) the model development for describing the non-Newtonian behaviour of silicone oil based on measurement (material model), 2.) an analysis of the real filling process using measuring equipment (measured result), 3 .) and in virtual space with help of advanced numerical simulations (simulated result), while 4.) the difference between the measured and the simulated results is minimized by further corrected model parameters. 5.)

When measuring the material properties and the filling process, a solution must be found to a.) correctly take into account the Weissenberg effect [3] by measuring the high viscosity silicone oil type AK1.000.000 selected for investigation and b.) the effect of thixotropy [4] on the results; c.) look inside the metallic, closed geometry of the damper during filling and to track the oil-front inside the device; d.) prepare a test-damper for oil front tracking; e.) build a filling device for on-the-spot filling of the damper.

Methods

 

Rheology deals with the description of the flow and deformation properties of fluids using chemical and structural engineering. I used a rotary rheometer in the frequency range of 0.1–100 Hz and in the temperature range of 25–200 °C to determine the rheological characteristics (shear stress and viscosity as a function of shear rate) of silicone oil type AK1.000.000. The nonlinear relationship between the shear stress () and the shear rate
() in the fluid is expressed by the dynamic viscosity () according to Equation (1) [5].

 

                                                          (1)

 

Small amplitude oscillatory shear tests are performed in the shear rate range of 0.628–628 rad/s to develop the Carreau-Yasuda viscosity model describing the dynamic viscosity of oil (see Equation (2)) with the Anton Paar Physica MCR 501 rotary rheometer available in the Miskolc. The model parameters are () zero-shear viscosity; () infinite-shear viscosity; () time relaxation factor; () transition control factor and () Power Law index [6].

                                    (2)

 

Neutron radiography is one of the most advanced non-destructive materials testing methods in modern materials sciences, where the object is scanned by neutron beams and scattering or reflecting neutrons on atomic structures is observed. While X-rays only interact with the electron cloud, the neutron beam can penetrate all the way to the nucleus and explore a world that X-rays or any other radiation produced under controlled conditions cannot. Since neutron beams more easily penetrate metals than hydrogen-containing materials (such as water or silicone oil), they are suitable for viewing a liquid inside a metal device. [7] Neutron beam can be obtained by by-passing ray stream in a block of working nuclear reactor.

The Carreau-Yasuda viscosity model developed from the rheology measurements is implemented into Ansys Fluent sub module for calculating multiphase flows. By importing the geometry of the test-damper, already used in the neutron radiography measurements, and setting the measurement conditions in the software, a transient fluid dynamic simulation of the filling process is performed. In this method the governing equations (mass, momentum and energy conservation laws) are solved iteratively over each control volume, which together makes the flow domain. By considering the flow parameters calculated for each volume, a solution is interpreted over the entire flow field, such as the pressure, velocity, temperature and viscosity fields. The current position of the fluid front is also determined. [8]

Results

 

Prior to testing AK1.000.000 silicone oil, preliminary measurements were performed with AK600.000 silicone oil, since the viscosity of this oil is lower and more fluent. Thus, it takes less time to prepare the sample (filling into cup, removing air bubbles, cleaning). The preliminary measurements were performed in the shear rate range of 0.1–100 1/s at 100 °C with 15 seconds shear time. As the measurements made on different samples (taken from the same oil) were close to each other with a small standard deviation, the reproducibility of measurements was verified. Upon doubling the shear duration (to 30 s) the viscosity change over time is steeper. Different viscosity results are also obtained if the samples are allowed to rest for different times after measurement (molecular chains need some time to regenerate). The time dependence of rheological properties is called thixotropy and its consideration makes the mathematical description of the change in oil viscosity difficult. Using the measurement results available in the literature [9], I could develop a Carreau-Yasuda viscosity model for AK1.000.000 silicone oil in the temperature range of 0–80 °C with a relative error of 9%. Prior to neutron imaging of test-damper, preliminary measurements were performed to determine the appropriate material for the test-damper that provides the best visibility for the oil in the resulting images. Preliminary measurements have shown that metals with high mass attenuation coefficient (such as nickel, manganese, chromium, cobalt and iron) not only tend to highly activate and need a long resting time to recover, but also significantly conceal silicone oil in the results (see left side of Figure 2). However, placing silicone oil in aluminum housing, the visibility of the oil drop is significantly improved (see right side of Figure 2).

 

Figure 2: Neutron image of silicone oil in housing made of cast iron (left) and aluminum (right)

After implementing the Carreau-Yasuda viscosity model valid for AK1.000.000 oil into Ansys Fluent and importing the CAD model of the test-damper used for neutron radiography measurements, the first oil filling simulation has been made at 80 °C oil temperature in a quarter geometry of the test-damper (see Figure 3). Numerical results show that it takes 0.9 s to load 7.5 grams of silicone oil into the damper. During the filling process (from left to right) the viscosity of the oil increases continuously and the fluid flow slows down.

 

Figure 3: Numerical simulation of silicone oil spread in damper-gap (oil is in red, air is in blue)

Expected impact and further research

 

The present research resulted in the development and application of a methodology for process optimization of torsional vibration dampers based on rheological measurements. The methodology is useful not only in the vehicle industry to save time, cost and capacity, but in the other areas (e.g. electronics, aerospace, and medical), where silicone oil is used. The neutron imaging method is first used here to monitor the propagation of a viscous medium. Further measurements are needed to extend the range of application, to check the results of the optimizations and to determine the surface tension and wetting effect for accuracy improvements.

Publications, references, links

List of corresponding own publications:

 

M. Venczel, Á. Veress: Introduction to Design and Analysis of Torsional Vibration Dampers in Vehicle Industry, International Journal of Engineering and Management Sciences, 4(1), 310-324, 2019. https://doi.org/10.21791/IJEMS.2019.1.39.

 

Venczel Márk, Dr. Veress Árpád: A viszkózus torziós lengéscsillapítók termikus vizsgálata hőmérséklet-csökkentés céljából, GÉP, Vol. 70, No.1 (2019) pp. 38–42

Link: http://real.mtak.hu/94180/ (25.08.2020.)

 

Márk Venczel, Árpád Veress: Model development with verification for thermal analysis of torsional vibration dampers, 17th International Conference of Numerical Analysis and Applied Mathematics, Rodosz, Görögország, Időpont: 2019. szeptember 23–28. Konferenciakiadvány: AIP Conference Proceedings, 2293, 200011, 2020. https://doi.org/10.1063/5.0026437

 

List of references:

 

[1]    Wojciech Homik: Diagnostics, maintenance and regeneration of torsional vibration dampers for crankshafts of ship diesel engines, Polish Maritime Research, 1(64) Vol 17, pp. 62–68. Link: https://content.sciendo.com/downloadpdf/journals/pomr/17/1/article-p62.xml (25.08.2020.)

 

[2]    Hasse&Wrede: Visco damper, After Sales Service, Service flyer, Hasse&Wrede GmbH, Berlin, Germany. Link: https://www.hassewrede.com/media/documents/Serviceflyer.pdf (25.08.2020.)

 

[3]    Dealy, J.M.; Vu, T.K.P.: The Weissenberg effect in molten polymers, Journal of Non-Newtonian Fluid Mechanics 1977, 3(2), 127–140. https://doi.org/10.1016/0377-0257(77)80045-1

 

[4]    Giorgia Bettin: Thixotropy - a review, lecture material, 2006. Link: https://nnf.mit.edu/sites/default/files/documents/sr-2006-1.pdf (25.08.2020.)

 

[5]    Malvern Instruments Worldwide: A Basic Introduction to Rheology, 2016. Link: https://cdn.technologynetworks.com/TN/Resources/PDF/WP160620BasicIntroRheology.pdf (25.08.2020.)

 

[6]    https://www.computationalfluiddynamics.com.au/tips-on-modelling-non-newtonian-fluid-viscosity/ (25.08.2020.)

 

[7]    https://nmi3.eu/news-and-media/neutron-imaging-past-present-and-future.html (25.08.2020.)

 

[8]    https://www.math.uci.edu/~chenlong/226/FVM.pdf (25.08.2020.)

 

[9]    Kőkuti, Z.; Dr. Czirják, A. Szilikonolaj nemlineáris viszkoelasztikus tulajdonságainak mérése és modellezése, PhD dissertation, Doctoral School of Physics, Institute of Technology and Materials Science, University of Szeged, Szeged, 2015. Link:

http://doktori.bibl.u-szeged.hu/2672/1/Kokuti_Zoltan_PhD_Ertekezes.pdf (25.08.2020.)