Multimethod Concept for Continuous Wear-Analysis of the Piston Group 2018-01-0839
Friction losses as well as lube oil consumption at the piston group are key factors for future engine downsizing concepts regarding to emissions and consumption. This means an early identification of friction losses and wear is essential within development. The main problem is that the wear assessment is based on long durability tests which are typically performed in a later phase. This may lead to the fact that an early optimized configuration with respect to friction can cause a potential wear problem later in the durability test program. Still ongoing trends in combustion engine engineering lead to both the minimized oil supply in the tribocontact piston bore interface and improved wear resistance. One is forced to the conclusion that understanding and quantifying wear will be a key driver for the future engine development process. The aim is a holistic concept that combines different methods to investigate wear and furthermore its combination with friction loss studies. The platform for this approach is a cutting-edge single cylinder floating liner engine. With this test bench it is possible to measure the friction losses of the piston group throughout the complete crank rotation in fired condition. In combination with the radio isotope concentration method (RIC) technology, it is possible to investigate friction and wear in parallel. This is the first time both methods are being used concurrently on the same system. Additionally, other tribological factors like blow-by and oil consumption are included in the study to completely characterize the system. The pool of methods and their connections will be introduced, and are illustrated for the piston bore interface of a passenger car configuration. This multimethod concept allows a tailored approach for the prediction of friction as well as wear based on the measurements and by using a physical simulation model. A mathematical correlation between the tribological factors, such as wear and friction, will be shown in detail.