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. To facilitate liner wear measurement at points of interest, including ring reversal locations, direct proton and deuteron beam irradiations are used to create distinguishable spots of radiation on the surface of the liner. The irradiated parts are then reinstalled in the test engine and the engine is run under typical or extreme operating conditions. Gamma rays emitted from radionuclides of irradiated wear particles abrading from the rings, bearings and liner during engine operation serve as detectable tracers as the particles circulate in the lubrication system.
Measuring the level of radiation associated with these particles using a gamma ray spectrometer provides a direct measure of the mass of wear particles present in the oil at the time of measurement. When compared to calibration values, these measurements give the direct amount of wear incurred during a given test period.
With this technology, it is possible to measure ring, bearing, and liner wear simultaneously, in real-time, without disassembling the engine for inspection. The use of germanium based spectrometers has significantly improved isotope resolution, enabling better component identification and increasing the probability that more components can be observed simultaneously.