Investigation of Melt Pulsation during Powder Production by Atomization with Supersonic Gas Jets
SupervisorsProf Andrew Mullis (School of Chemical & Process Engineering) - lead academic supervisor, Dr Duncan Borman (School of Civil Engineering)
Theme(s)Reacting Flows, Mixing and SafetyParticulate Flows, Sediments and Rheology
High pressure gas atomization (HPGA) is a commercial process for the manufacture of metal powders in which supersonic gas jets are used to disrupt a stream of molten metal into a fine spray of droplets. The interaction of the supersonic jets leads to the formation of a Mach disk below the atomization nozzle which increases the back pressure at the nozzle tip and so reduces the melt flow (a condition terms closed-wake). Under gas-only flow the closed wake condition is stable. However, when the metal is introduced the Mach disk can be disrupted reducing the back pressure and increasing the metal flow (the open-wake condition). During normal operation, commercial atomizers ‘pulse’ between the open- and closed-wake conditions in a quasi-periodic manner. The subsequent variation in metal flow rate results in a wide spread in the particle size distribution. Following on from a previous successful PhD project in which the gas-only flow was modelled, in this project a CFD model of the gas + metal flow will be constructed to understand atomizer pulsation. The initial approach would be to introduce the metal via a finite number of mass bearing particles to study their effect on the stability of the Mach disk.