Investigation on the jet impingement cooling of steel discs using air-atomized water mist

Abstract

The high-performance manufacturing of turbine discs requires a green, controllable, and rapid quenching method to regulate phase transformations and enable the on-demand engineering of mechanical properties during heat treatment. This study proposes the high-speed jet impingement cooling of air-atomized water mist for quenching irregularly shaped steel discs. A customized facility capable of heating to 1200 °C and cooling workpieces using 90 high-speed spraying nozzles, was developed for quenching a 210 mm diameter stainless steel turbine disc. The cooling rate was tunable by adjusting the jetting velocity (100–150 m/s) and water load fraction. Numerical simulations, based on an enthalpy-based continuum spray model, were used to circumvent the complex dynamics of water droplets by treating the mist as a single-phase fluid with phase-dependent properties, providing accurate thermal and flow predictions. Introducing the fine mist of droplets into high-speed air jets enhanced cooling performance, achieving ultrafast cooling rates of 673 °C/min during the solid solution phase transformation, four times faster than single-phase air jets and comparable to oil immersion cooling. Increasing the water load fraction substantially promote cooling, whereas increasing jetting velocity had a marginal effect. These heat transfer enhancements become less effective, as the Biot number exceeds 4 and the cooling transitioned into a conduction-limited regime. The jet impingement cooling of air-atomized mist offers a viable, controllable and environmentally friendly approach to the high-performance quenching, applicable to not only steel turbine discs but also to diverse materials and metallic components.