- Email: [email protected]
Experimental and numerical investigation of a viscoseal: part II
FEATURE
Experimental and numerical investigation of a viscoseal: part II Jarray Mohamed, Henry Yann, Fatu Aurelian and Souchet Dominique, Pprime Institute D3, University of Poitiers, Poitiers, France This article, which is published in two parts, describes research that focuses on the analysis – through an experimental study – of the sealing behaviour of a noncontact dynamic sealing device known as a viscoseal (or sometimes called a helical groove seal). Despite its reliability and its advantageous characteristics, compared with other types of sealing devices, the viscoseal is still under-researched because of its complex characteristics. The experimental apparatus used in this work is equipped with two different test cells. The first, made from acrylic glass, is transparent and is used for the visualisation of the liquid–air interface within the viscoseal. The second cell, used for pressure measurement, is composed of bronze. The experimental results are compared with numerical results obtained using the Reynolds model and also with computational fluid dynamics code. The first part of this feature article, which was published in the August 2019 issue of Sealing Technology newsletter, provides a general introduction and covers the experimental set-up and relevant references. The second instalment, which appears here, presents the results of the study by comparing the experimental findings with the predictions of numerical models, and provides a conclusion. We begin this instalment by discussing the sealing length in the seal, as it is directly representative of seal performance.
Experimental and numerical comparison The transparent cell enables the sealing length to be easily and, more importantly, accurately measured at any point within the seal. Tests were conducted for a rotational speed ranging from 1500 rpm to 4000 rpm, and pressure inlet ranging from 0.01 MPa to 0.05 MPa. Figure 11 shows the increase in the sealing length as the pressure is increased at 2000 rpm. We used a stroboscope tuned to the same rotational speed of the viscoseal in order to be able to see the sealing length. The yellow line here marks the sealing length.
Measurements of the sealing length using the transparent cell
simulations were performed using our numerical model based on the Reynolds equation. The experimental results were compared with the numerical ones based on the modified Reynolds equation model. For more information regarding the modified Reynolds model, please refer to Souchet, D. et al.[11] The experimental results were compared with the numerical ones based on the modified Reynolds equation model. Figure 12 and Figure 13 show a comparison between the experimental results, obtained using the transparent acrylic glass poly(methyl methacrylate) (PMMA) cell, and the numerical results. The experimental points correspond to the average of at least a series of three measurements. It is important to note that temperature regulation for these tests varies between 42°C and 47°C.
Figure 11. Sealing length as seen through the transparent cell, using a high-frequency stroboscope at 2000 rpm and 43°C: 0.02 MPa (a); 0.03 MPa (b); 0.04 MPa (c); and 0.05 MPa (d).
Figure 12. A comparison of experimental and numerical results – sealing length as a function of rotational speed for inlet pressures of Pi = 0.02 MPa and Pi = 0.04 MPa.
In order to verify the various trends and results observed in our experimental work, using the transparent and bronze test cells,
September 2019
Sealing Technology
5
FEATURE
Figure 13. A comparison of experimental and numerical results – sealing length as a function of rotational speed for inlet pressures of Pi = 0.03 MPa and Pi = 0.05 MPa.
It is intuitively clear that the sealing length depends on the rotational speed: as the speed increases, the sealing length decreases. Although some deviation can be observed for an inlet pressure Pi = 0.05 MPa, the experimental and numerical results show good agreement, with a relative error that does not exceed 20% for all investigated cases and 10% for the majority (approximately equal to, or greater than 95%) of cases. The observed deviation from the numerical results is likely to be related to the thermal expansion of the transparent cell. Under operating conditions, the supply temperature can reach 47°C.
Effect of lubricant temperature on sealing length Figure 14. Comparison of experimental and numerical results – sealing length as a function of lubricant inlet temperature for different rotational speeds.
Figure 15. Pressure along the viscoseal: comparison of experimental results, Reynolds models and computational fluid dynamics results obtained using ANSYS Fluent software at 1500 rpm (top) and at 2000 rpm (bottom).
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Sealing Technology
We now turn our attention to the effect of the lubricant temperature on the sealing length. Figure 14 shows experimental results for which the inlet pressure is held constant at 0.05 MPa, whilst the inlet temperature of the fluid is varied. For the numerical model, the fluid temperature is supposed to be constant along the viscoseal. Data are once again shown for various rotational speeds. The obtained values of the sealing length, not only make sense phenomenologically, through their trend of increasing with increasing temperature or, equivalently, decreasing viscosity, but also show reasonable agreement with the numerical results.
This feature article is based on a paper entitled ‘Experimental and numerical investigation of viscoseal’ that was presented at the 17th EDF–Pprime workshop, which was held in EDF Lab Paris-Saclay, France, on 4 October 2018. For further information on this conference, contact: 17th EDF–Pprime workshop ‘Green sealing: how to combine both low leakage and low friction?’, Noël Brunetière, InstitutPprime – UPR 3346, Dépt. Génie Mécanique et Systèmes Complexes, CNRS – Université de Poitiers – ENSMA, SP2MI – Téléport 2, Bd Marie et Pierre Curie – BP 30179, F86962 Futuroscope Chasseneuil Cedex, France. Tel: +33 5 4949 6531, Fax: +33 5 4949 6504, Email: [email protected], Web: http://edf-pprime-2018. sciencesconf.org.
September 2019
FEATURE/RECENTLY PUBLISHED PAPERS Measurements using the bronze cell In this part of the study, for pressure measurement along the viscoseal, the transparent housing is replaced by the one made from bronze, previously presented in Figure 4 (see Sealing Technology August 2019, page 7). Figure 15 shows the variation in pressure along the seal, where the rotation speed is held constant at 1500 rpm and 2000 rpm – respectively a) and b). Here Pi denotes the inlet pressure, Re denotes the Reynolds model and CFD (computational fluid dynamics) denotes the numerical results obtained using ANSYS Fluent software. As expected, we see a strong correlation between numerical and experimental results. Nevertheless, some slight deviations might be observed for z > 100 mm, which can be related to eccentricity errors and thermal expansion of the housing cell.
Recently Published Papers •
N. Rodriguez, SAIS R&D & Innovation, BD Medical-Pharmaceutical Systems, Franklin Lakes, New Jersey, USA; L. Dorogin, Leibniz Institute for Polymer Research Dresden, Dresden, Germany, (and PGI-1, FZ Jülich, Germany, and ITMO University, Saint Petersburg, Russia); K.T. Chew, Department of Chemistry, Massachusetts Institute of Technology, Massachusetts, USA; and B.N.J. Persson, PGI-1, FZ Jülich, Germany: ‘Adhesion, friction and viscoelastic properties for non-aged and aged styrene butadiene rubber’, Tribology International, Volume 121, May 2018, pages 78–83. In this research, the authors study adhesion and friction between smooth glass, and fresh and aged styrene butadiene – isoprene rubber blend. The friction and adhesion are only slightly modified by the ageing process, but both elongation at break and rubber toughness are strongly reduced. The researchers attribute this to changes in the cross-link density, a decrease in the filler matrix strength and to the formation and growth of crack-like defects. The latter have a small influence on adhesion and friction, but a large effect on the elongation at break. • W. Grabon, P. Pawlus, S. Wos and W. Koszela, Rzeszow University of
September 2019
Conclusion This work is dedicated to the design and characterisation of an experimental apparatus that is able to test the performance of viscoseals. Before mounting the viscoseal housing, the manufacturing precision of different experimental components was evaluated using high precision measuring instruments. Two cells were tested – one made from transparent PMMA, which enabled visual observation of the oil film and measurement of the sealing length along the viscoseal, and one made of bronze that enabled pressure and temperature measurements to be taken along the seal. The experimental results and variation in sealing performance, with numerous functioning parameters, were found to correspond closely to numerical simulations. From the above results, it may be concluded Technology, Faculty of Mechanical Engineering and Aeronautics, Rzeszow, Poland; and Michal Wieczorowski, Poznan University of Technology, Poznan, Poland: ‘Effects of cylinder liner surface topography on friction and wear of linerring system at low temperature’, Tribology International, Volume 121, May 2018, pages 148–160. This work aims to study, experimentally, the effects of cylinder liner surface topography on friction and wear of an engine’s piston-ring liner assembly, at a low temperature (-20°C). The experiments were carried out using an Optimol SRV5 oscillating wear tester under lubrication. Specimens were cut from grey, cast iron cylinder liners, honed and/or plateau honed with diamond or ceramic stones. Counter-specimens were cut from a chromium-coated compression ring. Short time tests of 30 min duration were conducted at a temperature of -20°C, with a stroke of 3 mm. In addition, for a few sliding assemblies, the duration of the tests at the low temperature was extended to 24 h. For comparison, similar tests for a smaller number of sliding pairs were carried out at a temperature of 80°C. Before and after the tests the cylinder liner surface topographies were measured using a white light interferometer (Talysurf CCI Lite). It was found that changes in liner height and frictional resistance at the low temperature were smaller for those tested at the elevated temperature. Two-process textures tested at the low temperature led to a smaller final coefficient of friction, compared with single-process surfaces. Opposed results were obtained at the high temperature.
that the presented viscoseal test operates successfully and has produced reasonable results.
Acknowledgment This work was supported by the CPERFEDER project of Région Nouvelle Aquitaine.
Further reading 1. Souchet, D., Jarray, M. and Fatu, A., (2017), Performance characteristics of viscoseals in laminar and turbulent flow regimes, Tribology International, 114, 152–160. Contact: Jarray Mohamed, Pprime Institute D3, University of Poitiers, UPR 3346 SP2MI – Téléport 2 – 11 Boulevard Marie et Pierre Curie, BP 30179 F86962 Futuroscope Chasseneuil Cedex, Poitiers, France. Tel: +33 545 254 979, Email: [email protected]
•
•
D. Liu, S. Wang and C. Zhang, School of Automation Science and Electrical Engineering, Beihang University, Beijing, China: ‘A multiscale wear simulation method for rotary lip seal under mixed lubricating conditions’, Tribology International, Volume 121, May 2018, pages 190–203. Macroscale simulation methods are commonly used to study wear of rotary lip seals. However, these methods generally do not address the effects of microscopic interfaces which, according to experimental studies, are important factors in the wear of a rotary lip seal. For this reason, this study proposes a multi-scale wear simulation method that is applied to rotary lip seal under mixed lubricating conditions, in which the effects of microscopic aspects of interacting surfaces are taken into account. The simulation results indicate that the wear of the rotary lip seal can be reduced by reducing axial asperity density, whilst increasing the circumferential asperity density. The results also indicate that wear of the rotary lip seal is susceptible to axial asperity density when it is within a particular range. J. Cui, P. Hou, B. Zhang and X. Zhao, Yancheng Institute of Technology, Yancheng, China: ‘Investigation of flow between deformed disks in hydroviscous drive’, Tribology International, Volume 121, May 2018, pages 287–301. In order to investigate the dynamic behaviour of the oil film between deformed disks in a hydro-viscous drive, revised mathematical models, based on steadystate and axisymmetric flow conditions, are developed in this study. The models
Sealing Technology
7
Experimental and numerical investigation of a viscoseal: part II Jarray Mohamed, Henry Yann, Fatu Aurelian and Souchet Dominique, Pprime Institute D3, University of Poitiers, Poitiers, France This article, which is published in two parts, describes research that focuses on the analysis – through an experimental study – of the sealing behaviour of a noncontact dynamic sealing device known as a viscoseal (or sometimes called a helical groove seal). Despite its reliability and its advantageous characteristics, compared with other types of sealing devices, the viscoseal is still under-researched because of its complex characteristics. The experimental apparatus used in this work is equipped with two different test cells. The first, made from acrylic glass, is transparent and is used for the visualisation of the liquid–air interface within the viscoseal. The second cell, used for pressure measurement, is composed of bronze. The experimental results are compared with numerical results obtained using the Reynolds model and also with computational fluid dynamics code. The first part of this feature article, which was published in the August 2019 issue of Sealing Technology newsletter, provides a general introduction and covers the experimental set-up and relevant references. The second instalment, which appears here, presents the results of the study by comparing the experimental findings with the predictions of numerical models, and provides a conclusion. We begin this instalment by discussing the sealing length in the seal, as it is directly representative of seal performance.
Experimental and numerical comparison The transparent cell enables the sealing length to be easily and, more importantly, accurately measured at any point within the seal. Tests were conducted for a rotational speed ranging from 1500 rpm to 4000 rpm, and pressure inlet ranging from 0.01 MPa to 0.05 MPa. Figure 11 shows the increase in the sealing length as the pressure is increased at 2000 rpm. We used a stroboscope tuned to the same rotational speed of the viscoseal in order to be able to see the sealing length. The yellow line here marks the sealing length.
Measurements of the sealing length using the transparent cell
simulations were performed using our numerical model based on the Reynolds equation. The experimental results were compared with the numerical ones based on the modified Reynolds equation model. For more information regarding the modified Reynolds model, please refer to Souchet, D. et al.[11] The experimental results were compared with the numerical ones based on the modified Reynolds equation model. Figure 12 and Figure 13 show a comparison between the experimental results, obtained using the transparent acrylic glass poly(methyl methacrylate) (PMMA) cell, and the numerical results. The experimental points correspond to the average of at least a series of three measurements. It is important to note that temperature regulation for these tests varies between 42°C and 47°C.
Figure 11. Sealing length as seen through the transparent cell, using a high-frequency stroboscope at 2000 rpm and 43°C: 0.02 MPa (a); 0.03 MPa (b); 0.04 MPa (c); and 0.05 MPa (d).
Figure 12. A comparison of experimental and numerical results – sealing length as a function of rotational speed for inlet pressures of Pi = 0.02 MPa and Pi = 0.04 MPa.
In order to verify the various trends and results observed in our experimental work, using the transparent and bronze test cells,
September 2019
Sealing Technology
5
FEATURE
Figure 13. A comparison of experimental and numerical results – sealing length as a function of rotational speed for inlet pressures of Pi = 0.03 MPa and Pi = 0.05 MPa.
It is intuitively clear that the sealing length depends on the rotational speed: as the speed increases, the sealing length decreases. Although some deviation can be observed for an inlet pressure Pi = 0.05 MPa, the experimental and numerical results show good agreement, with a relative error that does not exceed 20% for all investigated cases and 10% for the majority (approximately equal to, or greater than 95%) of cases. The observed deviation from the numerical results is likely to be related to the thermal expansion of the transparent cell. Under operating conditions, the supply temperature can reach 47°C.
Effect of lubricant temperature on sealing length Figure 14. Comparison of experimental and numerical results – sealing length as a function of lubricant inlet temperature for different rotational speeds.
Figure 15. Pressure along the viscoseal: comparison of experimental results, Reynolds models and computational fluid dynamics results obtained using ANSYS Fluent software at 1500 rpm (top) and at 2000 rpm (bottom).
6
Sealing Technology
We now turn our attention to the effect of the lubricant temperature on the sealing length. Figure 14 shows experimental results for which the inlet pressure is held constant at 0.05 MPa, whilst the inlet temperature of the fluid is varied. For the numerical model, the fluid temperature is supposed to be constant along the viscoseal. Data are once again shown for various rotational speeds. The obtained values of the sealing length, not only make sense phenomenologically, through their trend of increasing with increasing temperature or, equivalently, decreasing viscosity, but also show reasonable agreement with the numerical results.
This feature article is based on a paper entitled ‘Experimental and numerical investigation of viscoseal’ that was presented at the 17th EDF–Pprime workshop, which was held in EDF Lab Paris-Saclay, France, on 4 October 2018. For further information on this conference, contact: 17th EDF–Pprime workshop ‘Green sealing: how to combine both low leakage and low friction?’, Noël Brunetière, InstitutPprime – UPR 3346, Dépt. Génie Mécanique et Systèmes Complexes, CNRS – Université de Poitiers – ENSMA, SP2MI – Téléport 2, Bd Marie et Pierre Curie – BP 30179, F86962 Futuroscope Chasseneuil Cedex, France. Tel: +33 5 4949 6531, Fax: +33 5 4949 6504, Email: [email protected], Web: http://edf-pprime-2018. sciencesconf.org.
September 2019
FEATURE/RECENTLY PUBLISHED PAPERS Measurements using the bronze cell In this part of the study, for pressure measurement along the viscoseal, the transparent housing is replaced by the one made from bronze, previously presented in Figure 4 (see Sealing Technology August 2019, page 7). Figure 15 shows the variation in pressure along the seal, where the rotation speed is held constant at 1500 rpm and 2000 rpm – respectively a) and b). Here Pi denotes the inlet pressure, Re denotes the Reynolds model and CFD (computational fluid dynamics) denotes the numerical results obtained using ANSYS Fluent software. As expected, we see a strong correlation between numerical and experimental results. Nevertheless, some slight deviations might be observed for z > 100 mm, which can be related to eccentricity errors and thermal expansion of the housing cell.
Recently Published Papers •
N. Rodriguez, SAIS R&D & Innovation, BD Medical-Pharmaceutical Systems, Franklin Lakes, New Jersey, USA; L. Dorogin, Leibniz Institute for Polymer Research Dresden, Dresden, Germany, (and PGI-1, FZ Jülich, Germany, and ITMO University, Saint Petersburg, Russia); K.T. Chew, Department of Chemistry, Massachusetts Institute of Technology, Massachusetts, USA; and B.N.J. Persson, PGI-1, FZ Jülich, Germany: ‘Adhesion, friction and viscoelastic properties for non-aged and aged styrene butadiene rubber’, Tribology International, Volume 121, May 2018, pages 78–83. In this research, the authors study adhesion and friction between smooth glass, and fresh and aged styrene butadiene – isoprene rubber blend. The friction and adhesion are only slightly modified by the ageing process, but both elongation at break and rubber toughness are strongly reduced. The researchers attribute this to changes in the cross-link density, a decrease in the filler matrix strength and to the formation and growth of crack-like defects. The latter have a small influence on adhesion and friction, but a large effect on the elongation at break. • W. Grabon, P. Pawlus, S. Wos and W. Koszela, Rzeszow University of
September 2019
Conclusion This work is dedicated to the design and characterisation of an experimental apparatus that is able to test the performance of viscoseals. Before mounting the viscoseal housing, the manufacturing precision of different experimental components was evaluated using high precision measuring instruments. Two cells were tested – one made from transparent PMMA, which enabled visual observation of the oil film and measurement of the sealing length along the viscoseal, and one made of bronze that enabled pressure and temperature measurements to be taken along the seal. The experimental results and variation in sealing performance, with numerous functioning parameters, were found to correspond closely to numerical simulations. From the above results, it may be concluded Technology, Faculty of Mechanical Engineering and Aeronautics, Rzeszow, Poland; and Michal Wieczorowski, Poznan University of Technology, Poznan, Poland: ‘Effects of cylinder liner surface topography on friction and wear of linerring system at low temperature’, Tribology International, Volume 121, May 2018, pages 148–160. This work aims to study, experimentally, the effects of cylinder liner surface topography on friction and wear of an engine’s piston-ring liner assembly, at a low temperature (-20°C). The experiments were carried out using an Optimol SRV5 oscillating wear tester under lubrication. Specimens were cut from grey, cast iron cylinder liners, honed and/or plateau honed with diamond or ceramic stones. Counter-specimens were cut from a chromium-coated compression ring. Short time tests of 30 min duration were conducted at a temperature of -20°C, with a stroke of 3 mm. In addition, for a few sliding assemblies, the duration of the tests at the low temperature was extended to 24 h. For comparison, similar tests for a smaller number of sliding pairs were carried out at a temperature of 80°C. Before and after the tests the cylinder liner surface topographies were measured using a white light interferometer (Talysurf CCI Lite). It was found that changes in liner height and frictional resistance at the low temperature were smaller for those tested at the elevated temperature. Two-process textures tested at the low temperature led to a smaller final coefficient of friction, compared with single-process surfaces. Opposed results were obtained at the high temperature.
that the presented viscoseal test operates successfully and has produced reasonable results.
Acknowledgment This work was supported by the CPERFEDER project of Région Nouvelle Aquitaine.
Further reading 1. Souchet, D., Jarray, M. and Fatu, A., (2017), Performance characteristics of viscoseals in laminar and turbulent flow regimes, Tribology International, 114, 152–160. Contact: Jarray Mohamed, Pprime Institute D3, University of Poitiers, UPR 3346 SP2MI – Téléport 2 – 11 Boulevard Marie et Pierre Curie, BP 30179 F86962 Futuroscope Chasseneuil Cedex, Poitiers, France. Tel: +33 545 254 979, Email: [email protected]
•
•
D. Liu, S. Wang and C. Zhang, School of Automation Science and Electrical Engineering, Beihang University, Beijing, China: ‘A multiscale wear simulation method for rotary lip seal under mixed lubricating conditions’, Tribology International, Volume 121, May 2018, pages 190–203. Macroscale simulation methods are commonly used to study wear of rotary lip seals. However, these methods generally do not address the effects of microscopic interfaces which, according to experimental studies, are important factors in the wear of a rotary lip seal. For this reason, this study proposes a multi-scale wear simulation method that is applied to rotary lip seal under mixed lubricating conditions, in which the effects of microscopic aspects of interacting surfaces are taken into account. The simulation results indicate that the wear of the rotary lip seal can be reduced by reducing axial asperity density, whilst increasing the circumferential asperity density. The results also indicate that wear of the rotary lip seal is susceptible to axial asperity density when it is within a particular range. J. Cui, P. Hou, B. Zhang and X. Zhao, Yancheng Institute of Technology, Yancheng, China: ‘Investigation of flow between deformed disks in hydroviscous drive’, Tribology International, Volume 121, May 2018, pages 287–301. In order to investigate the dynamic behaviour of the oil film between deformed disks in a hydro-viscous drive, revised mathematical models, based on steadystate and axisymmetric flow conditions, are developed in this study. The models
Sealing Technology
7