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The post-1998 diesel engine emissions challenge was put forth in July 1995 by the Statement of Principles (SOP) signed by the manufacturers of heavy duty engines, the U.S. Environmental Protection Agency (EPA) and the California Air Resources Board (CARB). Through this SOP, the signatories agreed to reduce the on-highway diesel engine NOx emissions by 50% from the legislated 1998 4.0 g/bhp.hr to 2.0 g/bhp.hr by the year 2004 with no increase over the 1998 particulate matter legislated level set at 0.1 g/bhp.hr. There are provisions in the SOP for the optional grouping of the gaseous hydrocarbons and NOx, limiting them at a combined value of 2.5 g/bhp.hr with a 0.5 g/bhp.hr hydrocarbon limit. In North America, particulate matter emissions standards were first imposed on heavy duty diesel engines in 1988. Since then, the NOx and particulate matter were balanced by taking advantage of the trade-off between the two pollutants inherent in diesel engines.

It is now well-known that not only dimensions but also manufacturing tolerances and layouts of oil holes and grooves affect engine bearing performance. The present paper will show that some new features of machining and operating conditions can also influence bearing operation. Scratches caused by debris in the oil and the size of the counterbore on cross-drilled main journals can have highly detrimental effects. Results will also show how out-of-roundness and ellipticity affect bearing operation. This information can be vital for designing better engine bearings.

The future growth in power density in diesel engines is greatly dependent upon successful design of the bearings. The traditional analytical methods cannot account for or grossly approximate many of the important features of an actual bearing operation. A new computer program has been developed which uses the finite element method for a more accurate analysis of bearing performance under actual conditions. The program can analyze the type and location of oil supply grooves, taper, misalignment, noncircularity of journals and bearings, and various crankshaft machining defects. The paper provides a broad overview of the computer program and sample results for a variety of practical bearing features.

An analysis and a method of computation of the oil film thickness between the piston ring and cylinder liner of an internal combustion engine is presented here. A three-dimensional form of Reynolds' equation is used to enable consideration of film thickness variation in the circumferential direction. Various ring face profiles are considered in the analysis. The “tipping” of the ring about the piston axis is also included in the calculation. The solution of the resultant lubrication equation is achieved by using a finite difference approximation.