In Situ Control of Lubricant Properties for Reduction of Power Cylinder Friction through Thermal Barrier Coating

Abstract

Lowering lubricant viscosity to reduce friction generally carries a side effect of increased metalmetal contact in mixed or boundary lubrication, for example near top ring reversal along the engine cylinder liner. A strategy to reduce viscosity without increased metal-metal contact involves controlling the local viscosity away from top-ring-reversal locations. This paper discusses the implementation of insulation or thermal barrier coating (TBC) as a means of reducing local oil viscosity and power cylinder friction in internal combustion engines with minimal side effects of increased wear. TBC is selectively applied to the outside diameter of the cylinder liner to increase the local oil temperature along the liner. Due to the temperature dependence of oil viscosity, the increase in temperature from insulation results in a decrease in the local oil viscosity. The control of local viscosity through TBC targets areas of high hydrodynamic power losses mid-stroke while avoiding an increase in boundary friction near ring reversal. If temperatures near ring reversal remain unaltered, the expected result is the same oil viscosity, boundary friction, and wear rate near TDC as that of a non-insulated liner. In order to calculate the frictional benefit of insulating the cylinder liner, an in-cylinder heat transfer model predicts the temperatures along the liner. The local oil temperatures and engine performance parameters are then applied to a ring pack simulation to calculate the contributions to hydrodynamic and boundary friction power loss. The BsFC and wear rate results are then compared to baseline simulation data for TBC performance metrics. The results show the TBC insulated liner maintains adequate viscosity and film thickness near TDC for wear protection in the ring, while decreasing a significant portion of hydrodynamic for friction power loss in the mid-stroke. For the case studied, TBC offers a 0.7% BsFC improvement from the reduction in power cylinder friction with no increase in the wear rate of the ring pack. -ivAcknowledgements I will never forget my time here at MIT. I have grown mentally and personally thanks to this wonderful university and the people in the community. Above all, it has been fun and unpredictable here in Boston. I have witnessed a community come together for both tragedy and success during my time in Boston. Many people have been pivotal to my growth and development here at MIT and I would like to take the time to thank them in this section.My journey at MIT began with the guidance and grace of my advisor Dr. Victor Wong. Thanks to Dr. Wong, I was able to find a project with a perfect fit for my interests; and a project that stands to make an impact in the diesel engine industry. Thank you for the great opportunity to pursue my passion in diesel engine research.This project would not have been possible without the support of my project sponsor, Detroit Diesel. Specifically, I would like to thank Kevin Sisken, Sandeep Singh, David Atherton, and Peter Attema for their support throu...

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