Abstracts Category : Other

Numerical investigation of the piston skirt lubricationin heavy duty diesel engines

by Zhen SM Meng

Friction reduction in the power cylinder system ofinternal combustion engines has been undergoing broad and intensestudy in an industry-wide effort to reduce CO2 from the engines. Asa major source of frictional loss in the system, the pistonskirt-liner interface, specifically in heavy duty diesel engines,is investigated in this thesis work using a model developedin-house. Prior to the calculation of various cases for parametricstudy, improvements were made to the existing model in order toincorporate the characteristics of heavy duty diesel engines, andto enhance the robustness and accuracy of the model in general.These improvements include enabling arbitrary distribution oilsupply to the system, more efficient way to incorporate theshear-thinning effect of multigrade lubricants, and new scheme atthe start of the simulation to resolve the situation with largeoverlap between piston skirt and liner. The first part of theanalysis from application focuses on the geometric parameters ofthe system such as installation clearance, deformation of thecomponents, and surface roughness of piston skirt. The effects ofeach individual parameter are discussed and summarized. The secondpart of the analysis is focused on the sensitivities of the systemto the amount and distribution of oil supply. It was found thatmore lubricant can help reduce friction on thrust side duringexpansion stroke and on anti-thrust side during compression stroke.However, due to the rapid loss of oil at the piston-liner interfaceduring early compression stroke, there is a limit to the advantageof more oil addition. It has also been suggested that with acertain amount of oil supply, it is more beneficial to add thelubricant higher on the liner. This thesis work is the first effortwith the model to systematically study the piston skirt lubricationin heavy duty diesel engines. It is expected to be facilitated bythe measurement and observation from experiments in thefuture.Advisors/Committee Members: Tian Tian (advisor).