A multi-time scales semi-decoupled CHT (Coupled Heat Transfer) model and its application on piston transient heat transfer simulation

Abstract

Transient CHT simulations between in-cylinder combustion and chamber components are difficult to achieve due to time scale issues. In this study, a multi-time scales semi-decoupled CHT model is proposed and verified by mature CFD (Computational Fluid Dynamics) tools (e.g., Openfoam, Star CCM+, and Fluent) in a simple structure. Then, the established model is used to simulate the transient CHT process between the in-cylinder combustion and the piston. The calculated results are compared with the experimental results of the piston hardness plug. The 1D (one Dimensional) analysis demonstrates that the amplitude of the solid temperature fluctuation reaches an equilibrium state almost at the beginning of the calculation. The comparative results show that the calculation speed of the multi-time scales semi-decoupled CHT model is increased by about 15 to 20 times. The accuracy of the calculated results of the four methods is highly consistent (the difference is less than 0.4 °C). In the coupled heat transfer simulation of the piston and in-cylinder combustion, only four in-cylinder cycles are calculated to achieve the convergence of piston temperature. The hardness plug test value on the piston's top surface is higher than the peak value of the temperature wave.