Characterization of the Flow Regimes in the Jet Spray for Different Twin-Wire Arc Spraying Nozzles by Adapting the Background Oriented Schlieren Technique

摘要

The correct understanding of the aerodynamic phenomena occurred at nozzle outlet and at the interactions between jet/particle and jet/substrate in twin-wire arc-spraying (TWAS) is an important task to implement improvements in the nozzle design. It is also an essential challenge for the control over the coating quality. The changes in the in-flight particle velocities are considered to be only a function of the drag forces caused by the dominating flow regimes in the spray jet. The presented work deals with the adapting of an innovative and real time simple technique called background oriented Schlieren (BOS). It was used in diagnostic of the spraying plume in TWAS process. The interference of the atomization gas flow with the intersected wires causes a deformation of the jet shape. It leads also to areas with different aero dynamic forces. The secondary atomization gas (SG) flow is implemented to reduce the divergence of the spraying plume. The number, location and size of the SG outlet holes are the controlling factors in the focusing of the spray jet. The configurations of the primary and secondary atomization gas outlet nozzles directly affect the in-flight particle characteristics. The direct benefit of the better understanding of the above mentioned aerodynamic processes should lead to a targeted improvement in the twin-wire arc-spraying process.