Session: 01-03 Advanced Engine Components and Future Propulsion Systems

Paper Number: 197422

197422 - A Summary of Tbcs in Ices – Evidence Supporting the Theory of Convection Vive 

Abstract: 

Periodically, research groups around the world have explored the application of thermal barrier coatings (TBCs) in reciprocating piston-cylinder engines for their potential to reduce heat transfer losses by elevating the surface temperature (i.e., reducing the temperature difference between the gas and the wall), thereby improving efficiency. In the 1970-1980s, the concept of the adiabatic engine was studied. More recently, researchers investigated “temperature swing” coatings that were designed to respond to and follow the temperature in the cylinder more closely due to their low thermal inertia. By following the gas temperature more closely, they could reduce the temperature difference between the gas and the wall during combustion but also minimize charge heating during the intake stroke. However, the literature has shown conflicting and sometimes counterintuitive results across a wide range of studies.

A potential explanation for the counterintuitive results is a theory called “convection vive” which speculates that as the surface temperature increases, the temperature in the boundary layer increases to the point where combustion can occur in the boundary layer. Combustion in the boundary layer disrupts the boundary layer and could cause the convective heat transfer coefficient, h, to increase faster than the temperature difference reduces, meaning heat transfer increases with TBCs rather than decreases.

This presentation shows results from a variety of TBC experiments which demonstrate efficiency improvements at low loads, where the wall temperature is generally low, and a slight efficiency penalty at high loads, where the wall temperature is generally high. A thorough analysis was conducted with different fuels and engines, and although it is difficult to prove conclusively with metal engine experiments, the results strongly suggest that the phenomenon of convection vive occurs at high loads, which can explain some of the conflicting results in the literature.

Presenting Author: Benjamin Lawler Clemson University

Presenting Author Biography: Benjamin Lawler is a Professor in the School of Mechanical and Automotive Engineering located at Clemson University’s International Center for Automotive Research (CU-ICAR). His research is related to improving the carbon intensity, performance, and emissions of internal combustion engines including using advanced combustion strategies and renewable low net carbon fuels like the alcohols.

Authors:

Benjamin Lawler Clemson University
Brian Gainey Clemson University