Understanding Viscosity and HTHS

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Originally Posted by Gokhan
The posts keep getting deleted and no one tells me why.
Are you posting copyrighted materials? There was a recent thread here that had some removed.
 

ZeeOSix

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Originally Posted by Gokhan
The posts keep getting deleted and no one tells me why.
I see your new thread that you posted late last night is now gone. Disappointing that someone is censoring this stuff without giving a reason.
 
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I'm suspecting it's copyright. There is a blurry line between what is fair use for discussion and what is violation of copyright. Also, maybe this should go to the technical discussion section, rather than the PCMO section, since this isn't PCMO specific.
 
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ZeeOSix

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Originally Posted by Garak
I'm suspecting it's copyright. There is a blurry line between what is fair use for discussion and what is violation of copyright. Also, maybe this should go to the technical discussion section, rather than the PCMO section, since this isn't PCMO specific.
The thread that got deleted had one graph snip-it (just like the re-post of it today), and links to the source of all the info posted. If every thread that had a snip-it graph or table from a paper was deleted there would literally be 100s of disappearing threads.
 
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Originally Posted by ZeeOSix
Originally Posted by Garak
I'm suspecting it's copyright. There is a blurry line between what is fair use for discussion and what is violation of copyright. Also, maybe this should go to the technical discussion section, rather than the PCMO section, since this isn't PCMO specific.
The thread that got deleted had one graph snip-it (just like the re-post of it today), and links to the source of all the info posted. If every thread that had a snip-it graph or table from a paper was deleted there would literally be 100s of disappearing threads.
This was a guess in my part based on another thread where stuff was deleted here recently. I do agree that it would be good to have a explanation of why the deletions occurred.
 
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Originally Posted by ZeeOSix
The thread that got deleted had one graph snip-it (just like the re-post of it today), and links to the source of all the info posted. If every thread that had a snip-it graph or table from a paper was deleted there would literally be 100s of disappearing threads.
Then, I'm out of guesses. wink Gokhan might have to PM a mod and see what he can find out.
 
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Regarding the copyright it says: Open Access: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Therefore, there is definitely no copyright violation here.
 
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Okay, thanks for that, Gokhan. That should be very helpful. I'd point that out in a PM to wwilson, who of all the mods is most likely to have familiarity with said license. He will also be in the best position to give you tips as to how to properly format things and set post length, just in case that happens to be an issue, too.
 
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I checked my calculator against the data for the eleven oils with different VIIs in the Part I paper. The average (RMS) error for the base-oil viscosity at 150 C [high-temperature, full-shear viscosity (HTFSV)] is 6%, or about 0.1 cP, which is really good. The worst cases were around 10%. This answers the general question regarding the accuracy of my calculator. To answer a question asked by Garak, HTFSV is both a directly measurable quantity (as it was done in the Part I paper) and a useful quantity (as it applies to the friction and wear of the cylinders and valvetrain per the shear rates in the Shell paper's abstract). I will present the results later. References: Shear thinning and hydrodynamic fri...g oils. Part I: Shear-thinning behaviour Shear thinning and hydrodynamic friction of viscosity-modifier-containing oils. Part I: Shear-thinning behaviour Nigel Marx (1), Luis Fernández (2), Francisco Barceló (2), and Hugh Spikes (1) (1) Imperial College, London, UK (2) Repsol Technology Centre, Madrid, Spain June 21, 2018 Part II: Hydrodynamic friction of viscosity-modified oils in a journal-bearing machine Part II: Hydrodynamic friction of viscosity-modified oils in a journal-bearing machine Sorin-Cristian Vladescu (1), Nigel Marx (1), Luis Fernández (2), Francisco Barceló (2), and Hugh Spikes (1) (1) Imperial College, London, UK (2) Repsol Technology Centre, Madrid, Spain September 6, 2018 Shear rates in engines and implications for lubricant design Shear rates in engines and implications for lubricant design R. I. Taylor (1) and B. R. de Kraker (2) (1) Shell Global Solutions (UK), Manchester, UK (2) Shell Global Solutions US Inc., Houston, TX, USA March 1, 2017
 
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Originally Posted by Gokhan
To answer a question asked by Garak, HTFSV is both a directly measurable quantity (as it was done in the Part I paper) and a useful quantity (as it applies to the friction and wear of the cylinders and valvetrain per the shear rates in the Shell paper's abstract).
Certainly. Now we have to see what comes out, notably how any calculated value would correspond to an actual measured result.
 
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More un-identified editing post posting...it's worthless engaging in real time, and pointless doing it later.
 
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Here is the theory behind my HTFS formula: [Linked Image] [Linked Image] The average error in HTFS for different VII types is only 6%. However, I didn't study the error in ASTM D341 and density extrapolation, as the paper had the dynamic-viscosity values directly but not the density values. Here is the comparison of my formula for the HTFS viscosity (BO DV150) to the test oils in the paper. The oil (type of the base oil, DI, and VII) is described in the first column. I couldn't compare most DI-containing oils except Oil #11 because they didn't have high-temperature data on them. Note that the DI (detergent inhibitor) package shears as well, in some case substantially. As a result, in the second Newtonian phase (ultrahigh shear rates, full temporary shear), you're left with the base oil + unsheared part of the DI + VII solvent but the VII polymer has no effect. PMA VII is unusual in that the viscosity-boost rate increases with the temperature, greatly enhancing the viscosity index (VI). Some ultrahigh-viscosity-index 0W-20 oils may be using a PMA VII. The downside is that it requires a lot more polymer than other VII types, which could increase the deposit formation. Nevertheless, the formula still works for the PMA VII, as far as HTFS is concerned. Note that the calculation of the VI, which is a secondary calculation, is not accurate, especially for VIIs with a strongly temperature-dependent viscosity-boost rate. [Linked Image] https://docs.google.com/spreadsheets/d/1gnOrQxsbymULx1s6_uBQi8zNHfJXg7lwwQpwzLSIWQI/edit?usp=sharing
 

JAG

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Nice write-up, Gokhan. I read it several times to try to get a good understanding of it all. The first two equations it starts with intuitively make sense and the algebra that follows looks correct. Thank you for sharing the write-up.
 
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Originally Posted by Shannow
it's worthless engaging in real time, and pointless doing it later.
I mean, what could you even say? His equation is ingenious and works well. It says so right there in the paper!
 
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Originally Posted by JAG
Nice write-up, Gokhan. I read it several times to try to get a good understanding of it all. The first two equations it starts with intuitively make sense and the algebra that follows looks correct. Thank you for sharing the write-up.
Thank you, JAG!
 
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Gokhan, how do you substantiate that your assumption of "c=b/s does not vary a lot with the VII type"? The entire rheological discipline of viscosity index improvers is based on the variations between molecular types (OCP, PIB, PMA etc) and their associated molecular weight relative to shear - which is measured by SSI and thickening power - which is directly connected to the molecular weight of the polymer. Being as the range of shear stability and thickening power is massive (5ssi-50ssi are commonly used in engine oils) how can you assume that there is limited variation? this is a critical part of your calculation and in my mind introduces enough error to make any result effectively meaningless.
 
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Related to the topic, is there a way to work this backwards to get a ballpark of the HTHS at lower temperatures at KV100 and KV40? (which I guess would be "high temp" at that point, but you know what I mean) I'm curious for a drag racing application. Easing into the beams at the start, the oil temp is ~140*F. At the top end of the track, crossing the 1/4 mile, the oil temp is usually 160-165*F, reaching a max temp of 175-180*F on the idle/coast back to the pits. Assuming that oil temperature in the bearings is ~60*F higher than in the pan (I'm not sure how accurate that is), this would put the peak bearing oil temperature at wide open throttle at about 220-230*F. It would seem an HTHS100 value would be more relevant here than an HTHS150. Is there anyway, with a known KV150, HTHS150, and KV100, that the HTHS100 could be calculated within a small margin of error and assuming the oil contains no VIIs?
 
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Originally Posted by Solarent
Gokhan, how do you substantiate that your assumption of "c=b/s does not vary a lot with the VII type"? The entire rheological discipline of viscosity index improvers is based on the variations between molecular types (OCP, PIB, PMA etc) and their associated molecular weight relative to shear - which is measured by SSI and thickening power - which is directly connected to the molecular weight of the polymer. Being as the range of shear stability and thickening power is massive (5ssi-50ssi are commonly used in engine oils) how can you assume that there is limited variation? this is a critical part of your calculation and in my mind introduces enough error to make any result effectively meaningless.
Hi Solarent, It's not an assumption. Did you miss that this assertion is based on a systematic comprehensive study of different VII types in about 18 test oils? Shear thinning and hydrodynamic fri...g oils. Part I: Shear-thinning behaviour Shear thinning and hydrodynamic friction of viscosity-modifier-containing oils. Part I: Shear-thinning behaviour Nigel Marx (1), Luis Fernández (2), Francisco Barceló (2), and Hugh Spikes (1) (1) Imperial College, London, UK (2) Repsol Technology Centre, Madrid, Spain June 21, 2018 See the Excel sheet I posted above for the comparison of the formula to the test oils. Of course, the constant c = b/s in the formula varies with the VII type. However, this variation is smaller than the variation of the viscosity-boost rate b and temporary-shear rate s individually, as b and s are proportional to each other. See Figures 3 and 8 in the paper. The worst-case scenario was two of the A-OCP VIIs, which appeared to be the same VII from different manufacturers, and they resulted in +9% and +13% error. They have unusually low temporary shear for the given viscosity boost. The most negative-error extreme case was one of the PMA VIIs, which resulted in -8% error in HTFS. It has higher temporary shear than typical. Average error was only 6%, which is very good for an estimator that's not told the VII type. If you know the VII type, of course, you can set c accordingly so that the error could be very small. You can then use the formula to accurately calculate HTHS or base-oil viscosity when blending with a VII.
 
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Originally Posted by RDY4WAR
Related to the topic, is there a way to work this backwards to get a ballpark of the HTHS at lower temperatures at KV100 and KV40? (which I guess would be "high temp" at that point, but you know what I mean) I'm curious for a drag racing application. Easing into the beams at the start, the oil temp is ~140*F. At the top end of the track, crossing the 1/4 mile, the oil temp is usually 160-165*F, reaching a max temp of 175-180*F on the idle/coast back to the pits. Assuming that oil temperature in the bearings is ~60*F higher than in the pan (I'm not sure how accurate that is), this would put the peak bearing oil temperature at wide open throttle at about 220-230*F. It would seem an HTHS100 value would be more relevant here than an HTHS150. Is there anyway, with a known KV150, HTHS150, and KV100, that the HTHS100 could be calculated within a small margin of error and assuming the oil contains no VIIs?
I didn't study the temperature dependence of the VII shear but the paper did and they verified a nice formula that gives the temperature dependence. In your case, you have a monograde oil; so, there is no VII. This makes the calculation of HTHS viscosity as a function of temperature straightforward if you neglect the shear of the detergent inhibitor (DI) pack. Since there is no VII, you have: HTHS(T) = density(T) * KV(T) Again, this is neglecting the shear of the DI pack, which could be significant. You can easily obtain KV(T) from KV40 and KV100 using the Widman operational-viscosity calculator based on ASTM D341: https://www.widman.biz/English/Calculators/Operational.html To calculate density(T), which decreases with the increasing temperature T, simply multiply density(15.6 °C) with the corresponding number in this table:
Code
T (° C)  density(T) / density(15.6)

15.6	 1.000 
20	 0.997 
30	 0.990 
40	 0.983 
50	 0.976 
60	 0.969 
70	 0.962 
80	 0.955 
90	 0.948 
100	 0.941 
110	 0.934 
120	 0.926 
130	 0.919 
140	 0.912 
150	 0.905 
160	 0.898 
170	 0.891 
180	 0.883 
190	 0.876 
200	 0.869
The values in the table are based on the formula: density(T) = density(15.6 °C) * exp{-d * (T - 15.6) * [1 + 0.8 * d * (T - 15.6)]} The density correction factor d varies from oil to oil, but the typical value of d = 0.000691325 I took usually gives 1% accuracy. Note that we neglected the shear of the DI pack. However, the DI pack shears as well and you need to adjust your HTHS(T) values accordingly. To a first approximation, you can decrease the HTHS(T) by the same percentage for all temperatures as you see for the shear of the DI pack experienced at 150 °C since you know HTHS(150 °C) by measurement. In other words, if HTHS measured / HTHS calculated is 0.98 at 150 °C, decrease HTHS calculated by 2% for all temperatures -- not accounting for the variation of the shear with temperature but as a first approximation. Since we are talking about a few percent here, it shouldn't be a concern for practical purposes. This also answers your previous question regarding why your monograde boutique oils appear to have VII in them according to my calculator: The DI pack shears as well. This was discovered in the paper about shear-thinning I linked above.
 
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