Modeling and verification of valve train dynamics in engines

[摘要] This study involved the modeling and verification of the finger follower valve trainarrangement 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 comparingthe results from the two aforementioned two phases.Acceleration and force were measured on a running engine. A force transducer wasspecially developed for this purpose. Digital signal processing was used in the analysisand implementation of all measured data.The spring model was developed systematically from a solid model, into a finite elementmodel, and finally into a dynamic model. All development steps were continuallychecked with experiments and calculations. The primary concept used in the springmodeling lends itself to modal analysis theory in conjunction with the superimposingof non-linearities onto a linear model.The dynamic model was verified and good correlations were found, especially athigh engine speeds where valve train dynamics play an important role. Parameter adjustmentscould 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 withoutthe dynamic model.

[发布机构] Stellenbosch University