Modeling and verification of valve train dynamics in engines
This study involved the modeling and verification of the finger follower valve train arrangement with the focus on the non-linear behaviour of high speed valve springs. The project was divided into three phases namely; the measuring of valve train dynamics, modeling of the valve train and the verification of the dynamic models by comparing the results from the two aforementioned two phases. Acceleration and force were measured on a running engine. A force transducer was specially developed for this purpose. Digital signal processing was used in the analysis and implementation of all measured data. The spring model was developed systematically from a solid model, into a finite element model, and finally into a dynamic model. All development steps were continually checked with experiments and calculations. The primary concept used in the spring modeling lends itself to modal analysis theory in conjunction with the superimposing of non-linearities onto a linear model. The dynamic model was verified and good correlations were found, especially at high engine speeds where valve train dynamics play an important role. Parameter adjustments could be made in the dynamic model and the effect that some engine mechanisms, such as engine oil aeration, had on the valve train dynamics were identified. The project was concluded with a case study of a cam profile optimisation project. Dynamic problems were found that would normally not have been identified without the dynamic model.