Questions about Regenerative Blower

[cspeier]

I know some guys are up on this type of blower. Bruce has mentioned them several times. I have a few questions. What would a unit like this pull, cfm wise? How loud are they? Any other info would be grateful.

1 hp
3450 rpm
max pressure 50
max vacuum 45

[bruce]

I have a 3hp 3phase one, I have not gotten the time to play with it all that much and would really like to see what it can do. It is alot quieter than the vaccum blowers I'll say that much. I guess I need to get mine up and running so I can give some better feedback. Problem has been I am using my flowbench daily now and its kinda tough to take it out of service to try out a new blower. Maybe I can get sometime this weekend.

I would say a 1hp will not be large enough. Most manufacturers have files/data on thier website for these blowers so if you know the model number you can get the flow curves from them. I would not go less than 3hp, I would venture to say that the cfm's on a 1hp model will be less than 100cfm at that flow depression.



Edited By bruce on 1143139916

[Jesse Lackman]

Here is some information;



And

[Jesse Lackman]

And

[Tony]

I have wanted to play with one of these myself for a very long time, but so far have not been able to find one large enough for me at the right price.

The characteristics of these blowers are quite different to that of a centrifugal blower. They absolutely love high pressure, but flow is fairly fixed. A three phase unit coupled up to a variable frequency drive would quite likely make an excellent flow bench blower, especially at high test pressure.

A very rough rule of thumb when looking at these blowers might be around 50 CFM per horsepower, so 1Hp is probably not going to be enough. Three to ten Hp might be more like it.

[bruce]

Well had a chance today to hookup my blower, here are some pics:




Not real scientific to say the least.

This blower is rated 3 phase 220v 6 amps, 2.5-3.1 HP 80" of H2O and 154 cfm's I could only muster 100cfm (corrected to 28") @ 15.5" with the setup you see testing a 100cfm @28" plate. I do give it one thing ITS QUIET! I was able to test without hearing protection and carry on a conversation with my wife, even with the drone of my 5hp phase converter running in the background. 2 of these blowers hooked up would work quite well I think. I wish I could try out a VFD like Tony suggests but dumping more money into this right now is not a priority. My quest for a cheap (?) VFD on ebay will continue . . .

I'd really like to measure the amp draw through this setup right now and probably will do that on Saturday if I get a chance. My regular testing is done with 2 Ametek 7.5" blowers and will draw upwards of 35" on this same 100cfm plate so there is a substantial loss of depression but at a bonus of alot less amps.

Here is a pic of what my nephew refers to as my "mad scientist" rig . . .



Not a pretty thing by anymeans!

[PFM]

All,

As for the sound level of the bench this regen blower vs Amtec vac motors, I found the part under test, at high flow rates, makes more noise than all 10 motors running. My original design had provisions to reduce the fan noise with sound absorbing panels, I do not even worry about the fans now. What I need is a bigger house drop, the bench draws more than any thing else I own, ooops forgot the 3 ton AC compressor it draws more.

Regards,

PFM

[Jesse Lackman]

PFM I don't follow, are you using a regenerative blower?

I've been watching these things on eBay and it looks to me like there would not be a horrible cost difference between 10 923 vacuum motors, mine averaged $50 a piece, and a regenerative blower. One thing the big regenerative blowers are heavy. I think placing the blower in a remote location like a different room would be an interesting idea, that way the only sound you would hear would be the cylinder head port.

For example a Elmo-G 2BH1-910 (343 curve) is 580+ pounds, this model will pull 600cfm @ 130" water!

An Elmo-G 2BH1-900 (333 flow curve) is 420 lbs, this model will flow 500cfm @ 90"

Somewhere I saw the larger capacity regenerative blowers run at 3600 rpm which might make them louder.

[bruce]

Jesse, before you get to excited about the flow curves take a look at my results, I'm no where near the flow curve for my blower. I agree on the price though, the low amp draw is also a big plus. 2-3 of these blowers would move alot of air for the amps. I'll re-test mine today at actual flow versus depression and report back.

The lack of screaming blowers is also high on my list of positive things! It is quieter than the dust collector on my blasting cabinet. Cost to ship one is a big draw-back, I keep looking for a large one within driving distance for local pickup. I had this one shipped to me and it was not cheap (if I recall auction plus shipping was around $125), if you get it cheap enough that offsets the shipping cost.

I'm still looking for a large single impeller blower like Tony recommends.

[bruce]

Ok for all of you out there who are following along with this thread plus make a note of this . . . on a regenerative blower there is a BIG ARROW that points in the direction of rotation, your blower must rotate in this direction for it to work efficently!

Well now how do I know this? Seems someone had mine wired backwards and it was running the opposite way. 3 phase wiring is easy to get crossed up and my electrician (me) had the blower running in reverse rotation. I did have L1, L2, L3 wired the way it is coming out of my converter and my lathe runs in the correct direction so I assumed the blower was doing the same (yes I didn't check it), but the blower was running backwards. Anyways I swapped L1 & L2 and have it now running in the correct direction.

My findings changed some but not what I expected though, a 100cfm plate @ 28" flowed 90cfm @ 20.5" not all that impressive given the size of my blower being 2.5-3.1 hp (this was a quick check and I didn't make any corrections for temp and baro). I have to say it is still extremely quiet though.

Tony, how much effect would you think a VFD would have?

[Jesse Lackman]

Bruce, a 2.8 hp Elmo-G curve 171 shows about 90 CFM @ 20" pretty close to what you have there.

The other models I listed have 20 (curve 333) and 25 hp (curve 343) motors on them, those things are monsters.

What brand is your blower?

[bruce]

The blower I have is a Fuji and it matchs the curve in the manual now that it is flowing the correct rotation.

[Tony]

I believe a VFD would make very big difference to the performance of a regenerative blower.

These regenerative blowers have characteristics much more like a positive displacement pump, than a common air blower. (Think piston pump, or roots supercharger here) In other words the volume of air flow per revolution stays fairly constant over a very wide range of back pressure. If you look at the published flow curves, they are almost flat. These things can really be loaded up with back pressure, and flow hardly changes.

The open flow of a regenerative blower is far from impressive, whereas a common vacuum motor just pours out air when there is no significant back pressure. But under high back pressure, the regenerative blower will beat a vacuum motor easily for efficiency.

Another very interesting characteristic is that the required drive horsepower (and motor amps) for a regenerative blower increases almost directly with back pressure. So if your blower is rated at say ninety inches pressure, and you only run it at forty five inches of back pressure, the motor will be only half loaded.

What you could do with a variable frequency drive is rather interesting. It would be possible to run the three phase motor much faster than 60Hz, up to say 120 Hz or possibly even more.

That means you can trade off pressure capability for additional flow. So a 100 CFM 80" rated regenerative blower could be run at double the RPM to get 200 CFM at 40" pressure without overloading the motor.

It is easy to see that a VFD set up to be continuously adjustable from 0 Hz to 120Hz would not only double the nominal rated flow capacity, but would cut down noise and be vastly more efficient at absolutely HUGE (bench bursting) test pressures.

The motor can be run much faster than it's 60 Hz rating, and provided the motor amps are not exceeded, it will never be overloaded.

Controlling a regenerative blower by throttling is not a very good idea. If you try to reduce flow, the pressure just builds up and overloads the blower. An air bypass system may be the only way. But a VFD is obviously going to be far better than either.

[PFM]

Jesse,

No I am not using a regen blower. The point I was trying to make is the blower noise, be it Ametek or a regen is not the thing making the most noise at high flow rates, it is the part under test. The head or port above about 200 cfm at 28" is likely going to be louder than the fans. If you are flow testing nice clean velocity stacks and the like the fans will be louder, so I guess it all depends on what you are testing. I have a DB meter and plan on spending a bit of time in the shop today I will see if I can get some readings and post them.

PFM

[Jesse Lackman]

I've been worried about the noise of ten 923s.

Where does the majority of the fan noise come from?

Does it go right through the bench, or come out the blower compartment openings?

I wonder if doubling up most of the panels like I did might help with noise.

If I build another bench it will have a remote regenerative blower or at the least a remote box with the blowers in it. By remote I mean in a different room.