Dynamic modelling of compression ring conformability in high performance engines

Abstract

Internal combustion (IC) engines have been the predominant technology for sourcing or generating power for over 100 years. The fundamental function of engines has not changed since there first introduction. By combusting fuel within the chamber causes a pressure build from the expanding gasses pushing the piston assembly through the cylinder, this linear action is then translated to rotation through the crankshaft to generate work. During combustion the gasses will try to move past the piston and into the crankcase, to deter this from occurring piston rings are introduced. Thus rings are designed to be in tight contact to the cylinder wall, and is subject to friction and wear as it travels up and down the cylinder wall. When a new ring pack is introduced, a running-in process is required. This involves running the engine at a variation of speeds for set times, typically defined by the manufacturer. While this procedure is executed the compression ring will undergo a series of thermodynamic morphological stages, the material will change shape due to the heat from the combustion process and suffer material loss due to the friction wear between cylinder wall and ring face. This thesis examines the impact of the running-in method on the compression ring and its performance. The work presented shows a novel numerical method that offers the first simulated solution to compression ring rotation around the piston crown and its impact on the engine performance. This has been achieved by adopting simultaneously two modelling packages to compute dynamics and contact mechanics for a more accurate multiphysics result. Using this model a coating refinement has been developed, offering a new chamfer change to the present ISO standard ensuring a longer coating operational life.