Mudflap wrote: ↑08 May 2018, 22:28
Look at it this way:
The piston skirt is in hydrodynamic regime at all times bar the TDC and BDC reversals. Implicitly it is in full hydrodynamic regime when peak thrust loads occur, therefore the frictional loads are relatively small.
The top ring has a similar hydrodynamic regime, however its peak radial force (during peak cylinder pressure) occurs more or less when the piston is at TDC. Peak load+boundary/mixed lubrication = high friction.
The second ring is also called a scraper for a reason. It is in a boundary/mixed lubrication regime on all downstrokes regardless whether it is a taper, napier, etc. Just like the skirt and the top ring it is always in a boundary/mixed lubrication regime at TDC and BDC.
The oil ring never goes hydrodynamic.
But of course, if you still can't trust a bunch of internet hobos you can always open up an engine and compare wear at the top ring reversal (easy to spot as it has probably dug a big ass groove) to wear somewhere lower down where peak skirt thrust load should occur (not very easy to spot as it's f--k all in a good engine).
Here's some more made up plots:
https://i.imgur.com/VuTd49t.png
Well, I think I know why no one came up with such an idea before .. like mine .. Because engineers also like to bother things, and then, in good faith, they repeat those gently, inaccuracies. But I'm sure of some things, and even the Ricardo logo does not confuse me ...
https://www.sciencedirect.com/science/a ... 9X17303584
Here, too, three Swedish engineers, pretending to be scientists trying to push through such untrue things ... Exactly in their article they wrote "The piston with rings is responsible for more than half of those losses."
Especially this "half" is very repulsive with me .. because they have missed the truth about 30 to 40 times .. A little bit, ...
In conclusion, their article shows that the ring tension (N) ring strength is about 3 to 4 KG ... and we agree with that.
But with the fact that the other half is the piston friction (also 5 KG), no longer ...
http://www.new4stroke.com/sily%20w%20cylindrze.pdf
Here is also a dissertation about the forces acting on the piston. And there you can see that Force normal in relation to the liner cylinder is some 150 KG, so the forces are in a ratio of ~ 37 times. And it says here all the time about slow-speed engines ... with high-speed motors, you have to multiply that power by 3, with the same ring tension ..
Eat here and imagine that this side force is one-tenth of this force which has been hit by a connecting rod ..
Do not you think that my project looks more and more beautiful ?
Andrew
And exactly this Gruntgóra calculated 20MW, just like 20 MW, as the engine has 100 MW, it is 20%, which I cautiously estimated at 15%