Piston ring to cylinder wall pressure 5

[JerinG]

Can someone tell me what are usual numbers for pressures in MPa for piston rings in nowadays gasoline engines? With pressure I mean contact pressure between piston ring and cylinder wall.

 

[moon161]

I don't think you need too much. As far as motors I'm familiar with a mercedes OM617 diesel with CR of 21.5:1, as new compression is ~430 psi, and low limit for starting is about 200 psi, and once they start, they'll run fine. Do you plan any break in/run in?

 

[JerinG]

First wish is to start it and keep it under idle rpm for short time. Nothing more for now. And then check everything and decide how to move on. We don't know much what to expect. After that if it will be possible to get to some funding, we will try to correct inital design flaws that will arise and then put the engine on a dynamometer.

 

[RodRico]

JerinG, just out of curiosity and with all due respect as a fellow engine designer, why would investors put money into this new engine? What does it do better than existing engines and how will you prove to investors that you have good reason to believe it will indeed be better? I spent a lot of time pondering this and concluded my discriminators are high efficiency, low emissions, low cost, high reliability, and competitive power/weight ratio in an engine suited to propeller driven light aviation. I can back those claims with math models and won't even approach investors until I have third party test results that inspire confidence continued refinement will likely result in a viable product with an attractive market. I am assisted in my efforts by the fact that light aviation engines are not nearly as refined as automobile engines, are terribly inefficient, suffer large emissions (most still run leaded gas), and are likely among the last engines to be replaced by electric motors due to the size, weight, and hazards associated with current battery technology. Even so, I remain pessimistic and would never have "quit my day job" to pursue my design (I'm retired).

 

[JerinG]

RodRico, your comment is right on point, but I'm not the one who wants that someone puts money into this new engine design and basic design is not my idea. Investors were looking for someone to help them bring their design to the finish and it all started with a beveloid gear design that was something new for them and me also. I got a lot of starting help from this forum and I managed to produce a working gear that we needed.
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Main advantages that my investors are promoting are:
- There are considerable savings in the number of basic drive components. Less components of the drive assembly mean, consequently, smaller overall dimensions of the entire engine.
- Consequently, all this is reflected in the total mass of the engine, which in turn results in a higher specific engine power (more kW/kg of the engine mass).
- Consequently, a more calm engine operation is expected without significant vibrations.
- The new shape of the piston delivers smaller masses which are subject to greater acceleration. This consequently means smaller kinetic energies of moving parts. This means greater efficiency of the drive unit and lower fuel consumption.
- The design of the piston and the entire drive unit also allows for greater responsiveness of the engine.

Now, this all needs to be backed up. But in the end no "paper" result will back these claims. In the end no one believes you if you don't have a working prototype and we are close. It is a more risky way of getting somewhere, but that's what my investors chose. I would have done it the other way or we would find someone who could help us, but when I started it was already 50% finished.

 

[RodRico]

JerinG, May the Gods of Prototype smile upon your efforts and bring you success!

 

[JerinG]

Thanks RodRico. I will throw some sacrifice goods towards them and then we will see... It should happen in very close future.

 

[waross]

A practical illustration of the difference between the spring pressure of piston rings and the added pressure caused by the combustion.
I used to install diesel standby generators.
When there is a large electric motor on the generator, the generator must be oversized to start the motor and then runs almost all of its hours at a relatively light load.
At light load there may not be enough ring pressure to seal the oil control ring properly and the brand new engine may pump oil past the rings and out the exhaust.
I have encountered this several times.
One new engine pumped out almost all of its oil and shut down on low oil pressure in an hour or so on its first run.
The solution is to use a load bank for several days to properly seat the rings.
The point here is that you may want to consider some way of porting combustion pressure to the back side of your rings.

Bill
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"Why not the best?"
Jimmy Carter