Mar 14, 2018
Two-substance nozzles – which are also referred to as 'pneumatic atomisers' – rely on a second medium (compressed air, gas or steam) to supply the energy required for atomisation.
Media such as compressed air, gas or steam can reach extremely high speeds even when the pressure differences involved are relatively low – sometimes even matching or exceeding the speed of sound. Two-substance nozzles work by exploiting this phenomenon.
The flow speed of the second medium breaks the liquid down into fine droplets. Consequently, the liquid that is being atomised only has to travel at a relatively low flow speed itself. This results in very fine atomisation even in the case of highly viscous liquids or suspensions.
Depending on its viscosity, density and surface tension, the liquid that is being atomised can be supplied using suction, a downward slope or pressure. Within certain limits, some two-substance nozzles can also act as injectors.
That is why SCHLICK utilises a dynamic drop measuring device based on the dual PDA principle (PDA – Phase Doppler Anemometry). This contact and interference-free measurement procedure can determine both local speeds and other quantities, such as the relevant droplet sizes and volume flow densities.
This means that even highly complex spray and coating situations can be measured, compared and optimised, enabling reproducible results to be achieved for highly individual requirements.