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Technical Paper

Cam/Roller Component Fatigue Reliability Analysis

Life prediction and reliability analysis of a cam roller system were investigated. From the tribological analysis, the cam roller system was found to operate under low film parameter conditions and components were subjected to the risk of contact fatigue. Surface analysis performed on the failed rollers indicated that the surface distress was the primary cause for failure. Then, numerical analyses were performed to evaluate the cam roller life and its related reliability. The adopted approach combined a contact fatigue crack growth calculations with a probabilistic model for controlling the design uncertainty. The computation-efficient Fast Probabilistic Integration (FPI™) code was used to solve the problem. With appropriate descriptions for uncertainty distributions, the surface fatigue life of the specified cam roller system can be predicted along with a confident reliability level.
Technical Paper

Analytical Engine Design Methods: A Review

Computer based analytical design techniques are transforming the engine design process. Analytical tools allow faster and more accurate design optimization. The design process is also shortened because the electronic transfer of files permits the design to be worked concurrently by engineers working with different analysis packages or on various parts of the design. Prototype parts and tooling can be made directly from the Computer-Aided Design (CAD) by various rapid prototyping methods. The analytical design techniques can also permit a highly optimized design with less possibility of corrections being necessary in the development stages. This paper reviews these new design techniques and examines how they can be used to improve the design technique. The following design tools are discussed.
Technical Paper

Piston Ring Pack Friction and Lubrication Analysis of an Automotive Engine Using a Mixed Lubrication Model

A ring pack friction model has been developed based on the mixed lubrication concept to investigate the effects of ring surface topology on ring/liner interfacial frictions. The simulated friction results were verified by using the moving liner test rig and good correlations were established. The developed model was then extended to simulate the ring pack frictions under engine firing conditions. Surface roughness pattern oriented in the transverse, isotropic, and longitudinal directions were analyzed. The results indicate that the influence of surface pattern on ring pack friction is very substantial. A reduction of 9 percent of the ring pack friction is observed simply due to the surface pattern change. Friction reduction is a result from an increase in film thickness. This also helps to decrease the friction spikes near the dead centers and reduce ring wear. An increase in surface roughness magnitude significantly increases the ring pack friction.
Technical Paper

Instantaneous Unburned Oil Consumption Measurement in a Diesel Engine Using SO2 Tracer Technique

The contribution of lubricating oil to diesel engine particulate emissions is of concern not only because of stringent particulate emissions standards but also because of engine-to-engine variability. Unburned oil contributes directly to the particulate soluble organic fraction. A real-time oil consumption measurement technique previously developed was further refined to also measure real-time unburned oil consumption. The technique uses high sulfur oil, low sulfur fuel, and fast response, sensitive SO2 detection instrumentation. Total and unburned oil consumption maps over the engine operating range are presented. Results show that both total and unburned oil consumption generally increase as speed and load are increased. Unburned oil consumption shows some peaks at intermediate speed, high-load conditions. Oil consumption from individual cylinders was measured and shown to be approximately equal.
Technical Paper

On-Line Oil Consumption Measurement and Characterization of an Automotive Gasoline Engine by SO2 Method

An on-line oil consumption measurement system using the SO2 tracer method has characterized automotive gasoline engine oil consumption under various engine operating conditions, including a 200-hour durability test. An oil consumption map of total engine, individual cylinder, and valve train was produced for various speed and load ranges under both steady-state and step-transient operating conditions. The effect of spark timing as an additional engine parameter on the oil consumption was also investigated. Oil consumption maps have enlightened the conventional understanding of oil consumption characteristics and broadened the areas of concern for control technologies. This paper reports the benefit of the on-line oil consumption measurement system, the result of oil consumption history over the durability test, discrete measurement of oil consumption contribution within the engine, and various oil consumption characteristics affected by engine operating conditions.