Rapid prototyping of close-coupled atomiser components using an analogue atomiser and high frame rate analysis

摘要

A high frequency analysis method has been used to study the melt plume of an analogue atomising system which uses water and air to replicate a full metal atomisation run. The analysis method used is designed to note changes in the melt plumes density and central position, outputting them as frequency spectra. This system has been used to aid the quick evaluation of a number of component prototypes which have already found uses in close-coupled gas atomisation. A set of 6 melt nozzles has been designed with exterior angles mismatched to the apex angle of the gas jets. The degree of melt tip mismatch changes the spread of frequencies seen in the outputted spectra. It is thought that this spread indicates a more erratic movement of the melt plume. The other design innovation tested was a new die with discrete convergent-divergent gas jets. It was decided to analyse the prototype in a bid to find out about its behaviour at varying gas inlet pressures. A point of instability was noted at an inlet pressure 2.0MPa, and a point of increased stability was noticed at 3.0MPa Alongside the new components a series of experiments was conducted into the effects of gas jet machining quality on the atomisation process. Gas jets with jagged and unsymmetrical geometry cause a greater degree of pulsation and movement of the melt plume than gas jets produced with a highly symmetrical and even finish. It was found that this pulsation and movement increased in severity as the gas inlet pressure was increased.