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System contamination caused by contaminates or small particles built-in, self-generated, or inhaled from environment presents severe problems. The problems include but are not limited to the malfunctioning of valves, pumps, seals and injectors or lock-up of these components; increased wear of bearings, piston rings, and other friction components; and degradated machine performance. In general, system contamination changes a deterministic system into a stochastic system and shortens machinery service life. In this paper, these contamination problems are discussed in categories and associated analysis, testing and computer modeling methodologies are also discussed.

Radioactive tracer technology is an important tool for measuring component wear on a real-time basis and is especially useful in measuring engine wear as it is affected by combustion system operation and lubricant performance. Combustion system operation including the use of early and/or late fuel injection and EGR for emissions control can have a profound effect on aftertreatment contamination and engine reliability due to wear. Liner wear caused by localized fuel impingement can lead to excessive oil consumption and fuel dilution can cause excessive wear of rings and bearings. To facilitate typical wear measurement, the engine's compression rings and connecting rod bearings are initially exposed to thermal neutrons in a nuclear reactor to produce artificial radioisotopes that are separately characteristic of the ring and bearing wear surfaces.

Physical wear plays an important role in engine performance and longevity, with the vast number of engines alone indicating the extent of the poten-economic impact. Nevertheless, engine wear is often treated subjectively in terms of understanding the critical wear mechanisms caused by external and internally generated contamination or by the many transients encountered during an engine's duty cycle. In fact, in few other areas of engine design is quantitative data so limited. Consequently, there is a definite need to obtain quantitative, real-time data on engine wear, in general, and to establish correlations between engine wear and inlet air contamination, in particular. This paper discusses laboratory research designed to investigate these concerns.