optimization of oil and water immersion quenching process using numerical simulation methods

This paper presents the new Computational Fluid Dynamics (CFD) modelling technique to simulate the immersion quench cooling process. The main application of the present method is heat treatment of components, mostly steel landing gears and aluminum cylinder heads, in automotive and aerospace industries. The accurate heat treatment prediction of all complicated boiling physics plays an important role in conceptual and thermal analysis. Low residual stress levels are achieved by uniform temperature distribution during the cooling process and is the key to prevent component failure during operation. The numerical model developed within the commercial CFD code AVL(TM) FIRE M is used to model the complicated quenching process. Four steel gears placed on a steel structure were quenched in an oil tank with two different orientations and the temperature distribution studied for complete quenching period. After the steel gears, the study was extended for an aluminum step plate quenched in a water tank. The aluminum plate with variable thickness sections along its height was modelled. Two different solid part orientations were investigated, and the temperature profiles analyzed. Only the enthalpy equation is solved on 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. Temperature-dependent oil and water properties are used in these multiphase calculations. The results of both gear and step plates for two orientations are compared at ten thermocouple locations. The temperature histories predicted by the step plate correlate very well with the measurement data provided at ten 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.