Abstract
Keywords: Computational Fluid Dynamics, multi-phase flow, boiling, quenching, coupled simulation
The paper provides details about a newly developed modeling procedure to simulate quenching process using a commercial Computational Fluid Dynamics (CFD) code AVL FIRE. Boiling mass transfer process is triggered by submerging of a heated solid part into a sub-cooled liquid bath. As a result two-phase flow with boiling phase change is handled using the Eulerian two-fluid method. Mass transfer effects are considered based on either film or nucleate boiling regime. Separate computational domains constructed for the quenched solid part and the liquid (quenchant) domain are numerically coupled at the interface using the AVL-Code-Coupling-Interface (ACCI) feature. The program handles multiphase flow dynamics in the liquid domain in conjunction with the temperature evolution in the solid region in coupled fashion. The paper features numerical simulation results of a real cylinder head of a 4 cylinder gasoline engine. Computational grids consist of 1.2 million cells in both, the coolant (liquid) domain and in the solid region. Flow features such as vapor pocket generation, bubble clustering and their disposition are predicted. Comparison between measured and computed temperatures at different monitoring positions shows very good agreement for two cylinder head orientations. Strong non-uniformity in temperature distribution within the structure was found, which is of great importance in evaluating residual stresses and fatigue patterns within the quenched object. Effects on the structure resulting from the quenching process are presented through sample Finite Element Method results. Cylinder head packing (simultaneous quenching of multiple solids) has been investigated on a pack of 18 solids. Physical trends have been predicted.