Analysis And Experimental Study On The Oscillating Heat Transfer Characteristics Of Two-phase Flow In The Cold Oil Chamber Of A Piston

With the continuous increase of the engine’s requirements for emissions and power density,the problem of high thermal loads and high mechanical loads on the pistons has become increasingly prominent.The oil cooling gallery oscillating heat exchange has been widely used in high-strength engines as a very efficient method of enhanced heat dissipation.Due to the complexity and differences of piston models and the simulation results are difficult to be reliably verified,there are no common and mechanism conclusions about the heat transfer problem of oscillating two-phase flow.In this research,a visualized oscillation gallery for the oil cooling gallery was designed and built.Transparent test pieces and metal test pieces with the same structure as the actual oil cooling gallery of the engine piston were processed.At the same time,numerical simulation calculations were performed,and the test results were used to verify the calculation results to verify the accuracy of the numerical simulation model.A feasible oil cooling gallery structural optimization design scheme is proposed for piston,and the validated numerical simulation method is used to evaluate the optimized design scheme,so as to study the relationship between the oil cooling gallery structure and its heat exchange capacity.Thus providing the direction of the internal cooling gallery structure design.By comparing the results of experiments and numerical simulations,the unity of the capture rate data and the wall heat transfer coefficient is good(the maximum error of the capture rate is 8.4%,and the maximum error of the heat transfer coefficient is 8.5%).Besides,in the part of oscillating flow pattern,the above two also capture has many common characteristics.Therefore,the currently simulation method can be used as a means for further research to analyze the research conditions that other tests cannot reach.Discussing the transition between laminar and turbulent flow in the forced oscillating flow in the test.It was confirmed that the internal flow of the real machine at 1858 r/min was in a strong turbulent state as the internal flow of the test at 600 r/min,so the numerical simulation calculation method calibrated in the test can be applied to the simulation analysis of the oscillation heat transfer process in the oil cooling gallery under the actual machine operating conditions.Comparing three different oil cooling gallery structure models,using the velocity decomposition method during the analysis.Found that the heat transfer capacity of the oil cooling gallery is determined by the circumferential velocity near the wall when the oil oscillate.Therefore,when designing the oil cooling gallery structure,the cross-section waist line needs to be design to improve the circumferential speed of the oil in the oil cooling gallery around the wall,so that the oil can achieve an optimal movement process in the cavity.