Was work in this area done before 2018?
Would someone explain HT/FS?
- Thread starter Shel_B
- Start date
No.
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As will be shown in this study, the temporary shear-thinning behavior of VM-containing engine oils occurs typically over the shear rate range 10⁴ to 10⁸ s⁻¹ and for many years it was not possible to reach shear rates above ca 10⁶ s⁻¹ in high-shear viscometers. This meant that the shear-thinning behavior of VM solutions could not be fully explored. Typical flow curves of engine oils up to 10⁶ s⁻¹ can be found in [8,9,10,11]. This limitation has recently been addressed by the development of the PCS ultrashear viscometer (USV) that is able to reach 10⁷ s⁻¹. This enables almost entire shear-thinning curves to be obtained for VMs representative of those used in engine oils at realistic concentrations and temperatures. Full flow curves of two engine oils obtained in this way are described by Taylor [12]. To date, this approach has not been used to explore and compare the shear-thinning properties of different VMs. Such information is, however, important for designing low-friction engine oils. This paper therefore describes a systematic study of the temporary-shear-thinning properties of a range of commercial VM blends, both in simple solutions and in fully formulated engine oils. The measured shear-thinning behaviour is then used in conjunction with a conventional isothermal hydrodynamic-lubrication model in the companion paper to explore how and the extent to which shear thinning influences film thickness and friction in a journal bearing [1].
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Shear Thinning and Hydrodynamic Friction of Viscosity Modifier-Containing Oils. Part I: Shear Thinning Behaviour - Tribology Letters
Viscosity versus shear rate curves have been measured up to 107 s−1 for a range of VM solutions and fully formulated oils of known composition at several temperatures. This shows large differences in the shear thinning tendencies of different engine oil VMs. It has been found that viscosity...
link.springer.com
To be fair, the 2018 Hugh Spikes et al. paper wasn't the first paper that studied viscosity at shear rates above 10⁶ s⁻¹ but the second one.
The first paper, which is also discussed in my original thread on HTFS, is the 2017 Shell paper by R. I. Taylor and B. R. de Kraker.
Note that the abstract says "Other possible high-shear viscosity parameters are discussed, which may be an improvement on HTHS150," which is in the lines of I introducing the high-temperature, full-shear (HTFS) viscosity.
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Shear rates in engines and implications for lubricant design
R. I. Taylor and B. R. de Kraker
Shell Global Solutions (UK), Brabazon House, Concord Business Park, Manchester M22 0RR, UK
March 1, 2017
Abstract:
By combining shear-rate-range data in engine components with measured viscosity shear-rate curves on lubricants (at different temperatures), useful insights have been obtained on how the viscosity shear-rate curve of a lubricant should be “designed” to give low friction (and hence improved fuel economy). A brief review is carried out of typical shear rates in key engine components, which is backed up by the authors’ own calculations (using in-house lubrication software that includes realistic viscosity/temperature/shear-rate data). It is found that shear rates in journal bearings are typically in the range of 10⁵ to 5 × 10⁶ s⁻¹, whilst peak shear rates for the piston rings can be as high as 2 × 10⁷ s⁻¹, and for the valvetrain, peak shear rates can reach 2 × 10⁸ s⁻¹. Accurate viscosity shear-rate curves have been measured for different temperatures using a range of viscometers, including a novel mid-shear capillary viscometer that is capable of measuring viscosities in the shear-rate range of 10⁴ to 10⁶ s⁻¹. The use of such a viscometer is crucial to obtain good fits to the measured data (since usually, viscosity data are only usually available at low shear rates, 10²–10³ s⁻¹, and extremely high shear rates, > 10⁶ s⁻¹, and such data are difficult to use for accurate viscosity/temperature/shear-rate fits). The implications of the above data are then discussed for the design of low-friction lubricants that give improved fuel economy. It is highlighted that the traditional high-temperature, high-shear viscosity, HTHS150, measured at 150 ℃ and a shear rate of 10⁶ s⁻¹, although adequate for bearing-durability purposes, is probably not the ideal parameter to use for estimating the fuel-economy potential of an oil (since shear rates in engines are usually much greater than 10⁶ s⁻¹, and also because oil temperatures in fuel-economy engine tests are usually much lower than 150 ℃). Other possible high-shear viscosity parameters are discussed, which may be an improvement on HTHS150. The work also highlights that the choice of viscosity modifier, and the amount used, can have a substantial impact on the fuel-economy performance of a lubricant.
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The first paper, which is also discussed in my original thread on HTFS, is the 2017 Shell paper by R. I. Taylor and B. R. de Kraker.
Note that the abstract says "Other possible high-shear viscosity parameters are discussed, which may be an improvement on HTHS150," which is in the lines of I introducing the high-temperature, full-shear (HTFS) viscosity.
-------------------------------------------------------------------------------------------
Shear rates in engines and implications for lubricant design
R. I. Taylor and B. R. de Kraker
Shell Global Solutions (UK), Brabazon House, Concord Business Park, Manchester M22 0RR, UK
March 1, 2017
Abstract:
By combining shear-rate-range data in engine components with measured viscosity shear-rate curves on lubricants (at different temperatures), useful insights have been obtained on how the viscosity shear-rate curve of a lubricant should be “designed” to give low friction (and hence improved fuel economy). A brief review is carried out of typical shear rates in key engine components, which is backed up by the authors’ own calculations (using in-house lubrication software that includes realistic viscosity/temperature/shear-rate data). It is found that shear rates in journal bearings are typically in the range of 10⁵ to 5 × 10⁶ s⁻¹, whilst peak shear rates for the piston rings can be as high as 2 × 10⁷ s⁻¹, and for the valvetrain, peak shear rates can reach 2 × 10⁸ s⁻¹. Accurate viscosity shear-rate curves have been measured for different temperatures using a range of viscometers, including a novel mid-shear capillary viscometer that is capable of measuring viscosities in the shear-rate range of 10⁴ to 10⁶ s⁻¹. The use of such a viscometer is crucial to obtain good fits to the measured data (since usually, viscosity data are only usually available at low shear rates, 10²–10³ s⁻¹, and extremely high shear rates, > 10⁶ s⁻¹, and such data are difficult to use for accurate viscosity/temperature/shear-rate fits). The implications of the above data are then discussed for the design of low-friction lubricants that give improved fuel economy. It is highlighted that the traditional high-temperature, high-shear viscosity, HTHS150, measured at 150 ℃ and a shear rate of 10⁶ s⁻¹, although adequate for bearing-durability purposes, is probably not the ideal parameter to use for estimating the fuel-economy potential of an oil (since shear rates in engines are usually much greater than 10⁶ s⁻¹, and also because oil temperatures in fuel-economy engine tests are usually much lower than 150 ℃). Other possible high-shear viscosity parameters are discussed, which may be an improvement on HTHS150. The work also highlights that the choice of viscosity modifier, and the amount used, can have a substantial impact on the fuel-economy performance of a lubricant.
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Where is this HPL 10w-60???
Guess there was, since there was a paper in 2017. That article in your quote is the same 2018 paper I linked in post #16.No.
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As will be shown in this study, the temporary shear-thinning behavior of VM-containing engine oils occurs typically over the shear rate range 10⁴ to 10⁸ s⁻¹ and for many years it was not possible to reach shear rates above ca 10⁶ s⁻¹ in high-shear viscometers. This meant that the shear-thinning behavior of VM solutions could not be fully explored. Typical flow curves of engine oils up to 10⁶ s⁻¹ can be found in [8,9,10,11]. This limitation has recently been addressed by the development of the PCS ultrashear viscometer (USV) that is able to reach 10⁷ s⁻¹. This enables almost entire shear-thinning curves to be obtained for VMs representative of those used in engine oils at realistic concentrations and temperatures. Full flow curves of two engine oils obtained in this way are described by Taylor [12]. To date, this approach has not been used to explore and compare the shear-thinning properties of different VMs. Such information is, however, important for designing low-friction engine oils. This paper therefore describes a systematic study of the temporary-shear-thinning properties of a range of commercial VM blends, both in simple solutions and in fully formulated engine oils. The measured shear-thinning behaviour is then used in conjunction with a conventional isothermal hydrodynamic-lubrication model in the companion paper to explore how and the extent to which shear thinning influences film thickness and friction in a journal bearing [1].
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Shear Thinning and Hydrodynamic Friction of Viscosity Modifier-Containing Oils. Part I: Shear Thinning Behaviour - Tribology Letters
Viscosity versus shear rate curves have been measured up to 107 s−1 for a range of VM solutions and fully formulated oils of known composition at several temperatures. This shows large differences in the shear thinning tendencies of different engine oil VMs. It has been found that viscosity...
I now remember that my work on VII and HTFS was independent of the work by the Shell and Hugh Spikes groups. I discovered the Shell and Hugh Spikes papers about two months after my original work on VII and HTFS; therefore, I was entirely unaware of any preceding work while I came up with the concept of HTFS. It was not only a pleasant surprise but also a verification that similar work had been carried out very recently. Moreover, my calculations that estimate the VII content and HTFS were not done or repeated by these or other groups, and they remain as original research.
So, this is the historical timeline:
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March 1, 2017: Shell paper emphasizing the importance of studying viscosity at shear rates higher than 10⁶ s⁻¹
June 21, 2018: Hugh Spikes et al. tour de force paper studying viscosity, VII, and shear rate
April 12, 2019: Gokhan's discovery and introduction of the HTFS viscosity in relation to VII content, while being unaware of the Shell and Hugh Spikes papers
June 5, 2019: Gokhan's discovery of the Shell and Hugh Spikes papers
May 7, 2020: Gokhan's introduction of the automatic VII content and HTFS calculator
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Gokhan's automatic VII content and HTFS calculator (direct link to Google sheet)
So, this is the historical timeline:
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March 1, 2017: Shell paper emphasizing the importance of studying viscosity at shear rates higher than 10⁶ s⁻¹
June 21, 2018: Hugh Spikes et al. tour de force paper studying viscosity, VII, and shear rate
April 12, 2019: Gokhan's discovery and introduction of the HTFS viscosity in relation to VII content, while being unaware of the Shell and Hugh Spikes papers
June 5, 2019: Gokhan's discovery of the Shell and Hugh Spikes papers
May 7, 2020: Gokhan's introduction of the automatic VII content and HTFS calculator
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Gokhan's automatic VII content and HTFS calculator (direct link to Google sheet)
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