Visisizer For Faster In-Flight Particle Sizing

Visisizer is a direct imaging system which combines a pulsed laser to freeze subject motion, a digital camera to capture frames at high or low speed, and a computer to display and analyse images.

To evaluate and improve the efficiency of liquid chemical delivery, Oxford Lasers has developed 'VisiSizer'.

This cost effective laser based system provides unique insights into three key aspects of the spraying process - the break up of spray into droplets as it leaves the nozzle, the size and velocity distributions of droplets in motion, and the adherence of droplets to surfaces.

Oxford Lasers 'VisiSizer' is a direct imaging system which combines a pulsed laser to freeze subject motion, a digital camera to capture frames at high or low speed, and a computer to display and analyse images.

'VisiSizer' can characterise sprays from the initial formation of the spray through to its eventual deposition.

Cone angle, drop size and drop velocity, key parameters of the spray, are easily and accurately analysed; even non spherical droplets are measured correctly - impossible with other techniques.

Short pulses of laser illumination (down to 5 nanoseconds) are used to freeze images of the spray as it leaves the nozzle and breaks up into droplets, with thousands of drops per second being captured in real time.

Images are used to measure droplets of any shape and size, but 'VisiSizer' software is not deceived by out-of-focus droplet images which appear bigger than they really are.

By measuring the sharpness of the image edges, 'VisiSizer' automatically corrects for this effect.

While drop size and velocity distribution information is vital in finding out how nozzle parameters affect spray performance, it is the interaction of the droplets with the surface that determines the effectiveness of the delivery system.

Images showing the impact of droplets onto the surface, when viewed as a movie, can indicate how many of the droplets bounce off on impact and how many adhere to the target surface.

Zooming in on individual droplets, 'VisiSizer' shows such uniquely clear details that for the first time it is possible to see that many droplets are not only non spherical but many enclose a clutch of air bubbles inside them.

Alternative measuring systems such as phase Doppler anemometry would measure the size of a non spherical droplet incorrectly and give no indication of any air inclusions.

The high speed, high magnification of movies obtained by Oxford Lasers 'VisiSizer' are so easy to understand that they can be used as a training tool for end users.

Back to top