Bearing lubrication

[kmpillai]

Dear friends,
For a new I.C. engine (during the design stage) how to estimate the main journal bearings lube oil flow requirement.

Thanks & Regards
KMP

 

[vanstoja]

The calculation of lubricant flow for fluid film radial bearings is a complicated process too difficult to talk about in a forum such as this. Flow depends on the bearing geometry and the nature of lubricant feed, eg. self-acting or force-fed. The latter may have axial grooves, circumferential grooves, radial holes, etc. all of which have different equations which often involve experimentally determined parameters. Generally, total flow for force-feed lubrication is a direct function of diameter, diametral clearance cubed,delta pressure, journal rotational speed, shaft eccentricity and an inverse function of lubricant viscosity and length of bearing (or between grove lands).
You need a good bearing design book to make such calculations. One such book is Trumpler,P.R., 1966, "Design of Film Bearings", Macmillan Co. New York. Machine Design magazine published several empirical design methods in articles including Booser,E.R. & Wilcock,D.F., "New Techniques Simplify Journal Bearing Design", Apr.23,1987,PP.101-107. These authors probably have a book on the subject which can be recommended based on their extensive list of papers/articles on fluid film bearing design.

 

[myCAE]

Hi,

Use finite element code such as PAFEC or SOLVIA;
If it is about just an estimation, you can use FEM assuming the bearing operate in hydrodynamic lubrication mode.
If you want better accuracy then use FEM assuming the bearing operate in thermohydrodynamic mode.
If you want good accurracy, use FEM assuming the bearing operate in Elasto thermo hydrodynamic mode. If you want a full accuracy, use Elastohydrodynamic code that handle cavitation and hybrid lubrication. Then you will simulate the exact rate of flow, the power friction losses and other parameters. The complete FEM tool combined with design experiments will drive you to the perfect choice in term of bearing and oil, since you are at the design stage. It is easy after this step to comply with standard and choose with respect to the manufacturer spec.

If you want just estimation, just a simple FEM code can do the work, after solving the pb. for presures, a post processing step will give you the velocities and then, after integration, you can access the rate of flow.

Regards