Shear rates in engine components...

[Shannow]

Have found some more pics, just thought I'd share...no commentary, just some pics that may help inquisitive people's researches.

First is how viscosity changes with shear rate and temperature in a typical multigrade...HTHS is measured at 10^6 shear rate, so well into the second Newtonian phase.

This gives an indication on the shear rates in different parts of the engine...note that galleries and stuff, the KV is the dominant range...bearings, pistons, rings the second Newtonian above a couple thousand revs.

Last, a couple of indicative VMs effect on viscosity with shear rate at cold temperatures.

 

[Eddie]

Interesting and the comparison between a long stroke engine vs a short stroke engine. Ed

 

[BrocLuno]

Ah yes, the good old days when you could buy PIB-1 in gallon jugs at some local refiners

 

[userfriendly]

That's it! I'm switching back to a mono-grade as soon as the weather warms up.

 

[dailydriver]

I'd like to see those studies done on the shear at the tips of the valve stems/rocker arms, both ends of the pushrods (rocker and lifter), and cam lobe to lifter roller.

 

[Shannow]

dailydriver,
some of those locations are a bit hard, as you need the MOFT and then the differential surface speeds to calculate it. Bearings and pistons they use capacitance techniques and position measurements to get the gap across which the shear is applied to get shear rate.

So the wiping of valvestems with rockers, I can calculate the wiping velocity, but being a cyclic load, the film thickness can't be got at...similarly the movement of pushrods in cups.

Roller liftersn on a camshaft are more hertzian stresses, and therefore EHL is the main factor.

Have got some indicative shear rates of lobes/lifters, of 10^6 to 10^8.

 

[Jetronic]

They're talking about shear rates in the 10^8 sec^-1 region, 100 times higher than the hths shear rates.

Could, with some highly VII treated oils, the viscosity shear down even further at those rates or could this result in permanent shearing?

 

[userfriendly]

Where is 540 Rat when you need him?

 

[ledslinger]

Originally Posted By: Eddie
Interesting and the comparison between a long stroke engine vs a short stroke engine. Ed


My girlfriend was on the edge of her seat for that graph.

 

[A_Harman]

I like how the first graph shows viscosity loss vs. shear rate. Viscosity bottoms out at 10^6, which is where the HTHS test is done. Nice how that works out, isn't it?

 

[Shannow]

A_Harman,
I'm trying to learn how the viscosity index in high shear relates to the VI in kinematic...that three D one eplains, but I'm stuggling for actual numbers.

Here's another, in the early days of high shear viscometry (not a Selby paper, but Selby papers are very very good), where a separate oil supply was fed to a single main of a particular engine, and the draw off rate of lubricant was measured.