The Effect of Ring-Groove Geometry on Engine Cylinder-Kit Assembly Using Three-Dimensional Multiphase Physics-Based Modeling Methodology - Part II 2021-01-0645

Cylinder-kit tribology has been a significant focus in developing internal combustion engines of lower emission, reduced friction and oil consumption, and higher efficiency. This work addresses the impact of ring-groove geometry on oil (liquid oil and oil vapor) transport and combustion gas flow in the cylinder kit, using a dynamic three-dimensional multiphase modeling methodology during the four-stroke cycle of a piston engine. The ring and groove geometry, along with the temperature and pressure conditions at the interface between piston and liner, trigger the oil and gas (combustion gases and oil vapor) transport. A study of the second ring dynamics is presented to investigate the effect of negative ring twist on the three-dimensional fluid flow physics. The oil (liquid oil and oil vapor) transport and combustion gas flow processes through the piston ring pack for the twisted and untwisted geometry configurations are compared. Note that the twisted second ring induces a change in crevice volume as well as the leakage area. This, in turn, affects the overall mass flow rate and influences the liquid oil-gas (combustion gases and oil vapor) distribution in different regions of the cylinder kit. A comparison with the untwisted geometry for this cylinder-kit shows that the twisted second ring resulted in a higher blowby but lower reverse blowby and oil consumption. The oil mass fraction distribution pattern across the cycle also confirms the fact. The comparison of the model predicted oil consumption with existing literature shows that oil consumption is within the reasonable range for typical engines. Implementing this three-dimensional methodology leads to a better understanding of cylinder-kit fluid flow physics and the effect of ring-groove geometry on it. The findings presented in this work pave the way to further the ongoing development of optimum cylinder-kit designs with controlled gas leakage, low oil consumption, and low cylinder-kit friction.