The reciprocating motion characteristics of nanofluid inside the piston cooling gallery

• Flow patterns of nanofluid and air during reciprocating motion were captured.
• The effects of engine speed, filling ratio and nanoparticle concentration were discussed.
• The VOF, CLSVOF and Eulerian-Eulerian models were carried out.
• The compressive and zonal discretization schemes were introduced into the models.
• Heat transfer mechanism of solid-gas-liquid three-phase flow was revealed.

With the peak cylinder pressure in diesel engines steadily increasing, simply extending or modifying the cooling gallery configuration may be insufficient when power rating is above a certain level. The nanofluid with better heat transfer capacity may become a more appropriate option to improve piston cooling performance. Therefore, the current paper employed a high-speed camera to capture the flow patterns of nanofluid and air inside a simplified piston gallery at various crank angles and explored the heat transfer mechanism of solid-gas-liquid three-phase flow (nanoparticles, base fluid and air) during the reciprocating motion. On this basis, three numerical simulation methods (VOF, CLSVOF and Eulerian-Eulerian) were further carried out. The effects of engine speed, nanofluid filling ratio and nanoparticle concentration were discussed. The results revealed that the nanofluid is more appropriate for the piston thermal management and the cooling effect increases with the engine speed and nanoparticle volume fraction.

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