Ring pack behavior and oil consumption modeling in IC engines

In this dissertation, two major research areas are considered: further development of the piston ring analysis model, and application of this model to engine design and analysis in order to better understand physical processes in an internal combustion engine. The model development includes: creating the first operational three-dimension ring twist model; establishing an interface between the in-cylinder combustion model and piston ring; and adding the ring pack optimization routine.; It was found that ring twist significantly influences ring pack performance and dynamics and that the nature of ring twist requires a three-dimensional analysis of the ring motion. Simulations were performed for an engine at the same operating conditions for several combinations of twist and no twist analysis. The results show the importance of modeling ring twist to achieve accurate predictions of the ring position, inter-ring gas pressures and inter-ring pressure gradients. Special attention has to be paid to the motion of the twisted second ring at the middle of the intake and the end of the compression stroke and to the top ring at the beginning of the compression stroke and the end of the exhaust stroke.; Another part of the model development includes the ring pack optimization routine. An optimization technique was developed and applied to ring-pack design synthesis. When applied to existing engine ring-pack designs, optimized results indicated the potential for significant reduction in blow-by through the ring-pack by optimizing ring geometry.; In analysis of the blow-by of combustion chamber gasses through the ring pack, the coupled effects of ring dynamics, piston dynamics, ring-pack gas dynamics, and in-cylinder pressure are all important for achieving accurate predictions of blow-by. It was recognized that ring pack cannot be de-coupled from the engine bore-stroke ratio through its influence on piston/ring motion, therefore it has to be considered in the early stages of engine design in order to optimize ring pack performance.; In the Variable Displacement Engine (VDE) analysis, interesting physical phenomena associated with the ring pack transient processes after the engine valves are shut off were analyzed. The model predictions indicated the optimal valve timing in order to minimize losses of the in-cylinder pressure due to blow-by through the ring pack.