Experimental investigation of two-phase flow and heat transfer performance in a cooling gallery under forced oscillation

摘要

The demand of increasing power density of the Internal Combustion Engine promotes the technology development using internal cooling gallery of the piston. The oil flow and heat transfer performance o the piston internal cooling gallery have great influence on the cooling performance, which affects the thermal conditions of the piston and of the entire engine. The experimental study using visualising method is therefore critical and important to observe the flow patterns inside the piston gallery. In this paper, we presented the visualised study of two-phase flow patterns within an open cooling gallery by using a high-speed camera at various crank angles. The effects of motor speed both on the flow patterns and temperature distribution were investigated and the heat transfer mechanisms in gas-liquid twophase flow during reciprocating motion were explored. Based on the study, the period-doubling phenomenon, which represented the transition from laminar flow to turbulent flow, was observed when the speed was around 400-500 rpm. Results indicated the increase of motor speed can effectively improve the cooling performance. Results also showed when the speed was higher than 600 rpm, the reduction of temperatures was quite close, which proven the existence of optimal or minimum requirement of motor speed to achieve good quality cooling performance. The results obtained in this study could be used as a critical reference for numerical studies and important experimental reference to further investigate the design and optimisation of engine cooling gallery for vehicle application. (C) 2018 Elsevier Ltd. All rights reserved.