Thread: Dispersed Oil Particle generator

When testing various bits and pieces of dust extraction gear for how efficiently they remove dust I usually use the background dust levels in a shed as the source of dust, and for example measure before and after filtration. However this method has problems.

Often there is simply not enough dust to perform reliable measurements, especially for large particle sizes, so sometimes I just have to wait until suitable dust levels are around eg burning off days or when inside the house and testing things like masks I wait until SWMBO decided to grill some lamb chops. In the shed I am loathe to run machinery to deliberately fill the shed up with wood dust and this too has problems as its difficult to generate a constant stream of very fine wood dust without making kgs of coarse dust. Large particles also fall out of suspension quicker and change the profile of the particle distribution. High concentrations of wood dust can also choke a particle counter and damage it beyond repair.

In my electronics area I have used incense sticks but I don't especially like the smell, obtaining s constant stream is not that easy as they don't last very long, and if I use too many they leave a filthy great layer of crap all over the place. Plus the residue is gummy and I don't want too much this stuff inside my particle counters.

Pro level devices know as Dispersed Oil Particulate (DOP) generators are available for $$$. These generate abundant streams of very fine particles at a constant rate. Usually they use a special oil dropped into an hot chamber that partially vaporises the oil forming a a swarm of fine, mostly invisible 0.25 - 1 micron droplets. These particles are swept by a carrier gas (CO2 or N2) out of the camber and last long enough in the air for the particles to be moved in/through high volume air flow and filtration systems. The drops that are filtered out or pass through the filters or particle counters eventually evaporate away leaving nothing behind.

Anyway after avoiding this issue for many years I have decided to have a crack at making a small version of a DOP machine and here it is

The chamber is inside a 1.7kg 65mm long 65mm diameter Brass Hex block to which are attached various SS BSP fittings
S = is an old 80W soldering iron - eventually this will have some sort of heating control
OR = is the oil reservoir and there is a needle valve under it for fine control of the oil flow .
I = the inlet from a small aquarium pump
O = is the outlet to which another small hose is attached and used to direct the particles to where ever is desired.
The gauge is a temp gauge from an old BBQ - it reads about 10º to low - all I need it for is to tell me when its up to Temp.
Guts.jpg

It takes about 20 minutes to get up to temp but I hope that time can be shorted by insulating the block.

After placing one drop of oil inside the chamber its looks like very little smoke is being emitted (see below - remember most is invisible) but this amount is more than enough to send my particle counters close to max.
By photographing the emissions agains a black surface with side lighting its is possible to see the bigger particles.

Wehaveliftoff.jpg

The next step is to add adjustable carrier air flow rate and temperature control and explore withe these do.

There's not a lot to it but a short WIP is in the MW forums here
Insulating a small heat exchanger - Page 2

And before anyone elses suggests it no I will not be using it with any other type of hallucinatory oil