Lubrication requirement

[kmpillai]

Dear friends,
How to estimate the lube oil flow (quantity)requirement for the piston rings during the new engine design. Is their any reference please let me know.
Thanks

KMP

 

[EngJW]

Don't think there is an actual oil flow requirement for piston rings. The piston skirts need oil, but the rings only need to stop oil from getting to the combustion chamber. The amount of oil they need to prevent metal to metal contact is minimal and the oil they get is thrown off the main and rod bearings.

There are, however, calculation methods to estimate the oil required by hydrodynamic bearings (mains, rods, cam, other bushings). Piston spray jets could be included. The total pump flow is always more than the engine needs in order to build up pressure, so there is plenty of oil left over for splash lubrication of cylinders, lifters, etc.

 

[ivymike]

I agree - jlwoodward's response seems to be correct. What motivated the question? Is there an underlying question that would be more appropriate to address first?

 

[icrman]

There are allot of variables involved. Surface finish and materials, ring contact area and shape, ring tension, and of course clearances. It's most likely something arrived at by experimentation. I remember allot of SAE articles in the past about piston ring wear and lubrication tests, using radioactive materials. You might find some useful information there.

 

[kmpillai]

Thank you very much for your replies

Mr Jlwoodward, It will very helpful if you give an idea / reference, how to estimate the main bearing oil requirements.

KMP

 

[EngJW]

I don't have the book in front of me, but there is a machine design textbook by Shigley that contains a lubrication secton based on the classic study of Raimondi ( I might not have spelled that right).

This is a study of hydrodynamic journal bearings. It is filled with practical design information in graph form. You have to know or estimate the bearing load, the speed, the clearance, and the type of oil. Then you make an assumption on the allowable temperature rise and run through an iterative procedure until the assumed and calculated temperatues come out the same. The end result is the required oil flow, the amount of side leakage, and the friction power.