Search Results

A comprehensive computer package, FLARE, has been developed for carrying out Friction and Lubrication Analysis of Reciprocating Engines. FLARE considers four major lubricated components in an automotive engine -- piston skirt, piston rings, bearings, and valve train. Hydrodynamic, mixed, and boundary lubrication models are used, as appropriate, to model the lubrication phenomena. All the analytical models are based on solution of governing equations. Three levels of analyses with varying degrees of detail have been developed. Availability of different levels provides the flexibility of matching the complexity and accuracy of the analysis with the objective of the analysis. An empirical engine friction model, which is based on experimental data, is also available. Many user-friendly features are built into the FLARE system to make it easier to use for design engineers. This paper gives a brief overview of all the analysis sub-models incorporated into FLARE.

Lubrication analysis of piston skirts is a complex problem because of elastic and thermal deformation of the skirt, mixed lubrication, and surface geometry. Several analysis methods have been developed at General Motors over the years for carrying out the piston lubrication analysis. These methods differ in how much of the complexity is modelled. This paper briefly describes these methods and compares the friction prediction of each of these methods with data from an experimental rig designed to measure piston-assembly friction. In addition, results are presented to demonstrate the effect of some design parameters on the lubrication performance of a piston skirt.

An array of engine bearing analysis methods has been developed at General Motors over the years. All of these analyses consider wedge and squeeze effects, finite-length bearing, variation of load with crank angle, and cavitation effects. The simplest among them utilizes the so-called mobility method for solving the governing Reynolds equation. Others include finite-element solution for bearings with arbitrary geometry and grooving, finite-element solution for elastohydrodynamic lubrication, mass-conserving finite-volume solution, non-Newtonian lubricant analysis, and thermohydrodynamic analysis. This paper reviews these methods, describes when and how these methods are used, compares results and describes some applications.

A method for determining the optimum location of oil-feed holes in crankshaft journals is described. The method is applied to the 92 series Detroit Diesel Allison Division (DDAD) engines. On an average, the minimum oil-film thickness of the main bearings was increased 83% by relocating the oil holes. A qualitative verification of the results was obtained by a coolant-contamination test. The revised crankshaft was used in the MY1985 production of the engine.