Experimental and Numerical Investigation of the Multiphase Flow and Heat Transfer in an Oil Jet Cooled Engine Piston

The piston temperature has to be carefully controlled to achieve effective and efficient thermal management in the internal combustion engines. One of the common methods to cool piston is by injecting oil from the crankcase underside to the piston under-crown area. In the present study, a novel 3-D multiphase thermal-fluid coupled model was developed using the commercial CFD software SimericsMP+ to study the piston cooling using the oil jet. In this model, an algorithm was proposed to couple the fluid and solid computation domain to account for the different timescale of heat transfer in the fluid and solid due to the high thermal inertia of the solid piston. The heat transfer coefficient (HTC) and reference temperature were mapped to the piston top surface and the liner temperature distribution was also used as the boundary condition. The temperature-dependent material properties, piston motion, and thermal contact resistance between the ring and piston were also accounted for. The oil film on the piston under-crown area was captured in the model to ensure an accurate prediction of the heat transfer coefficient. The piston temperature from the numerical simulation was validated against the experiment measurement at 13 different locations, and the root mean square error (RMSE) was within 13°C. Furthermore, this study investigated the effect of oil jet temperature and oil flow rate on the piston temperature distribution. The piston cooling model developed in the current study has demonstrated to be a valuable tool in optimizing piston design and development.