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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 mathematical model for tribological analysis of different automotive- valve-train configurations has been developed as a part of the FLARE (Friction and Lubrication Analysis of Reciprocating Engines) package. The model is based on an in-depth kinematic analysis and on a rigid-body dynamic analysis, including dynamic analysis of the valve spring. Lubricant film thickness, contact pressures, and frictional power loss are predicted. A mixed-lubrication model is used to determine the friction force at the cam-follower interface. In addition, lifter rotation is modeled to predict its effect on frictional power loss. Detailed results are presented for a pushrod valve train. Also, this paper compares frictional power loss for five different valve train types. They are: direct-acting overhead cam, pushrod, end-pivoted finger follower, center-pivoted finger follower, and cam-in-head. The valve trains are made equivalent by keeping the valve lift and the no-follow speed the same.

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.

Comparisons are made between friction predictions of the FLARE (Friction and Lubrication Analysis of Reciprocating Engines) computer code and experimental data for the purpose of validating FLARE. An in-line four-cylinder engine under motoring conditions was selected for doing the experiments. Three major friction producing subassemblies were considered: piston assembly, crankshaft main bearings, and valve train. A Taguchi-type L16 matrix was used for the piston assembly, while an L8 matrix was used for the valve train. A traditional approach (varying one parameter at a time) was used for crankshaft main bearings. The agreement between experimental measurements and FLARE predictions, for all the cases studied, is very good. The match is closest for the valve train, followed by the crankshaft main bearings and piston assembly. In addition, trends and effects of changing design parameters are predicted correctly by FLARE.

This paper documents the effects of primer composition and concentration on cold starting of 3.1L variable fuel vehicle (VFV) engines with fuel methanol. Primers were restricted to two commercially viable types: full boiling range gasolines and light isocrackate (LIC). Results show that cold starting performance improved with increasing pentane:butane ratio in fuels of equivalent RVP, and improved with increasing primer content. Cold starting performance showed an excellent correlation with vapor-air equivalence ratio (Фfv) and with initial liquid mass fraction of butanes and pentanes; the correlation between cold starting performance and fuel RVP was p.

This paper reviews issues relating to seats including design for comfort and restraint, mechanics of discomfort and irritability, older occupants, and low-back pain. It focuses on the interface between seating technology and occupant comfort, and involves a technical review of medical-engineering information. The dramatic increase in the number of features currently available on seats outreaches the technical understanding of occupant accommodation and ride comfort. Thus, the current understanding of seat design parameters may not adequately encompass occupant needs. The review has found many pathways between seating features and riding comfort, each of which requires more specific information on the biomechanics of discomfort by pressure distribution, body support, ride vibration, material breathability, and other factors. These inputs stimulate mechanisms of discomfort that need to be quantified in terms of mechanical requirements for seat design and function.

Transfer-port and in-cylinder flow fields have been mapped in a crankcase-compression, loop-scavenged two-stroke engine under motored conditions (1600 r/min; delivery ratio: 0.5). The impulsive, high-velocity flow (initially ≳2200 m/s) issuing from the transfer ports is fairly uniform and symmetric in space. The resulting in-cylinder flow field displays a classic scavenging loop pattern, but is complex and asymmetric. The data also characterize backflow from the cylinder into the transfer ports and the spin-up and breakdown of the scavenging-loop vortex during compression. The detailed LDV results provide some quantitative support for the widely used Jante scavenging test. FOR THE GREATER PART OF A CENTURY, the scavenging process has been recognized as critical to the performance of two-stroke-cycle engines.