Two-phase flow-based numerical investigation of the temperature maps of sodium-cooled exhaust valves in a turbocharged engine

Abstract

Valves at the outlet of the combustion chamber in modern combustion engines must withstand very high temperature and acceleration. Such valves are subject to thermal loading to have to tolerate the limit of material temperature. The present study constitutes a contribution to predict the temperature maps of the sodium-cooled exhaust valves considering the real conditions of an engine operation. An adequate subdivision of the valve is used to better assess the effect of each part of the cylinder head. Therefore, the instantaneous heat transfer coefficient and adiabatic wall temperature for each subdivision are evaluated. To survey the two-phase flow phenomenon, the valve motion was modeled by a dynamic mesh method, and the sodium sloshing was modeled by the volume of fluid multiphase model. The average values of these parameters are calculated and introduced as boundary conditions in a finite element model implemented in the commercial code ANSYS to extract the temperature map. The results indicated that the maximum temperature errors between the simulated and the test results were 45.5 °C and 37.2 °C in the axial and radial directions of the valve, respectively, and their maximum relative errors were not more than 8%. As an application, this methodology is used to highlight the temperature maps and to show the region of extreme temperature in the aim of avoiding any damage.