Numerical simulation of immersion quenching process for cast aluminium part at different pool temperatures

Abstract

The present paper outlines the recently improved Computational Fluid Dynamics (CFD) model to simulate the immersion quench cooling process. The main application area of the presented method is heat treatment of cast aluminium parts, mostly cylinder heads in automotive internal combustion engines, where an accurate heat treatment prediction plays an important role in conceptual and thermal analysis. In order to achieve low residual stress levels resulting from even temperature distribution during the cooling process, and thereby to prevent component failure during operation, the numerical model of the quenching process, as developed within the commercial CFD code AVL FIRE®, was improved by allowing for variable Leidenfrost temperature. Preliminary results of variable Leidenfrost temperature model together with the implementation of additional interfacial forces, such as lift and wall lubrication forces are presented. Only the enthalpy equation is solved in the solid domain to predict the thermal field, whereas the Euler-Eulerian multi-fluid modelling approach is used to handle the boiling two-phase flow and the heat transfer between the heated structure and the sub-cooled liquid. The results of the improved quenching model are compared with available measurement data for various water temperatures ranging from 303 K to 353 K. Using the step plate with variable thickness sections along its height as the model test case, different solid part orientations were investigated and obtained temperature profiles were analysed. The temperature histories predicted by the presented model correlate very well with the provided measurement data at different monitoring positions. The temperature distribution within the solid part, obtained from the CFD simulation, can therefore serve as a realistic input for subsequent Finite Element Analysis (FEA) of thermal stresses within the quenched solid part.