Optimisation of high pressure gas quenching by application of CFD analysis

Abstract
At Aichelin GmbH an experimental high pressure gas quenching facility was used for heat treatment of automotive parts. Since uniformity and core strength of the heat treated parts were insufficient, a CFD-analysis was carried out to investigate the influence of the flow field on the performance of the facility. The results showed that the design of the facility was quite unfavorable from a fluid dynamics point of view. Large variations of flow velocity occurred in the charge zone and high pressure loss was produced by reduced cross section at shut-off valves. An optimization of the existing facility did not seem promising. Consequently, a new facility concept was designed, incorporating the results of the previous simulation and again tested by means of numerical simulation. The charge was simulated by a grid of cylindrical parts and in addition the gas pressure was increased to 20 bars. The new design demonstrated a very homogeneous flow field in the vicinity of the charge and pressure drop was reduced by three quarters. However the attempted quenching performance was not yet achieved with the initial blower. The results from the simulation led to the design of a full scale industrial gas quenching facility with an improved fan. This facility was able to meet the requirements in terms of core strength and uniformity from the beginning.