I am doing a project in which I need a certain amount of air coming out from a small tube and I have tried different solutions but have decided I should ask for advice. At the moment I am using a12V dc computer fan with 200CFM that pushes air at different speeds and times (this is controlled by the PWM pins in the arduino). This is doing what I want it to do HOWEVER the air that it produces goes into a ventilation hose (so far so good) and then into a connection that reduces the size of the tube (this last step is essential, but it results in a lot of air being pushed back into the ventilator, and so the air losses a lot of strenght), I am a bit stuck as it needs to be stronger but I'm not sure how to navigate around this.
While thinking of solutions I came across an inflate/deflate balloon project which used an air pump and an air vacuum. My question here is: Could I inflate a balloon that has two apertures so that I push a constant air through aperture "A" and once the air stops, a NC solenoid valve in the other apperture opens and the air in the inflated baloon is directed into apperture B which will then release enough air?
What do you guys think? Would this be possible at all? I know there would be no vacuum and I'm not sure if the inflated baloon produces enough pressure for the solenoid to work? - It's a thing that solenoids need a minimum working pressure, right?
Thanks on advance for your help! If I missed out anything let me know please
Is Your fan a cooling type fan?
If it is... Such a fan can push air through a tube having the same
diameter as the fan wings. Every attempt to narrow the tube causes a back pressure and the fans stalls.
You need another type of fan. Radial fans are better to build up pressure.
Another alternative is using a compressor and a valve opening according to the air requirements.
If you have a solenoid with specifications, they all show the minimum pressure. The minimum pressure is only a consideration if you have a piloted solenoid rather than a regular on-off solenoid. Tell us what you are using.
Hi! Yes, it's a pc cooling fan. The first attempt I did was at using a compressor and it was really loud, the air coming out blows into instruments so that didn't really work. I'll have a look at the other type of fans! Thank you!!
I've not bought the solenoid yet as I don't know if I should go down this track although I guess the only way of knowing is trying. I did have a quick search after I posted and I realised there's diff specs on diff solenoid valves but was unaware of what you said about this not being important with on/off solenoid valves so I'll have a look at this too. Thank you!
I do have some practical experience from things like this. Pressure fans are a lot different from "light wind" creating fans.
I'm not sure about the terminology, "back pressure", "counter pressure", "pressure"... what You should look for.
It creates the right amount of air for the instrument to produce sound. I am thinking I should then look for a pressure fan with similar or above revolutions per minute?
That's a pure cooling fan. They're often rated in volume per second, or so but doesn't work creating pressure.
What You can do is to divert a portion of the of the airflow and letting the remaining flow pass without any obstacle.. However I doubt You'll get the air You need.
For fans like this the outlet area should be at minimum the inlet area.
For informed product selection, you need to say (at least) the required flow rate (through the small tube) and pressure.
But would something like this work?
Their example (coincidentally) shows a balloon being inflated and deflated, but I doubt that is necessary, if you find an air compressor with the right specs.
well, I would say it needs at least 100 cfm. I actually came across that project, but I don't think the pump by itself would be enough.
That's why I thought of the option of inflating a balloon or a silicone rubber shape with two openings, and then deflating it on the other side by timing a solenoid valve, and using that accumulated pressure inside to produce enough air force ( I hope that reasoning makes sense)
I get this, and I've looked at pressure fans- they seem to be really low on their CFM specs though, which makes me question if it would work. Once again, I might have to just buy one and try it.
Yes, Cubic Feet per Minute. That is okay! Thank you! I might end up having to deal with the system I have at the moment and having mics on the instruments to increase their volume if I can't figure out another solution- Seems like the 200CFM pc fans I have, don't have equivalents with pumps or radial fans. I shall have a look and at least test it out and will update
No. You need to involve the pressure aspect as well.
That's usual for compressors used for air hammers, air torque wrenches, air paint devices. CFM and pressure.
I've got a 2.5 cm ID tube in the system I've operated, hopefully I can stick with this diameter- in terms of lenght, ideally the air can travel up to 2 meters with enough pressure.
To give more context, in my current prototype there is a 3d printed part that does the connection between the duct tube that is the same size of the fan I have, and the smaller tube. When that connection is screwed on, there is still quiet a lot of pressure (enough to to work, even when the outlet diameter has reduced), but as soon as I add the tube all of this is lost entirely and barely any air comes out. It gets all pushed back, which is what I am assuming the centrifugal fan would fix?
Copy some data, Air volume: 262 m3/h, Power: 51 W, Air pressure: 300 PA.
Do You have any idea about the pressure needed to press 100 CFM through a 1" tube? Why not a larger tube?
It's just because the aperture for the instruments is quite small, and so otherwise the air would get lost and not produce the sound if that makes sense.... I am completely clueless, I operate and trial and error which is possibly not smart, but based on your question I'm guessing I'm being unrealistic on achieving this?
If you need a silent/weak motor, there isn't much power and you have a big tradeoff between CFM and pressure. If you have strict pressure and CFM needs, that translates into power.
A 1HP (or 746 W) blower might get you 200CFM at 1.5psi.
Note the rather large velocity (about Mach 0.3). If the requirement is actually 200 cfm, not the 100 cfm shown above, then the average velocity would double to about Mach 0.6 ... which is still subsonic...
This site can help "ballpark" the pressure drop through the tube:
