Effect of wall heat insulation on wall heat transfer mechanism in rapid compression and expansion environment

Abstract

Heat insulation by a wall material which has low heat capacity and heat conductivity is one of the effective ways to reduce heat transfer. By the heat insulated coating, wall temperature is fluctuated following the behavior of in-cylinder gas temperature, which decreases the gap between gas and wall temperature. In order to suppress wall heat transfer in wide engine operation range, Model Based Development is required. In this study, wall heat transfer mechanism under wall temperature fluctuated condition by heat insulation was investigated by simultaneous measurement of wall heat flux and flow behavior in wall boundary layer in RCEM. As a result, it was clarified that turbulent energy was influenced by wall temperature behavior, which impact on heat transfer coefficient. In addition, non-dimensional velocity distribution in wall boundary layer was not changed drastically by wall temperature behavior. In terms of modeling under heat insulated condition, wall heat flux was able to be predicted well by wall heat transfer model taking into account of density change in wall boundary layer.

Keywords

• ices
• heat insulated coating
• wall heat transfer
• modeling
• thin-film thermocouple
• μpiv