Radial Blade Air Movers?

[Brooks]

Hello everybody! This is my 1st post, so hello my name is Mark

I've come across some interesting radial blade blowers at a local "Old Industrial Junk" house, which I'm very optimistic about. They are made by a company called Kooltronic. I took a bunch of pictures, so I'll start with that-












I hope that's not too many pics for the board, if so just let me know and I'll turn them in to links.

Anyhow, the pics pretty much tell the whole story. They're 2-stage blowers, as you can see in the pics the 1st wheel feeds in to the 2nd wheel. The wheels are 10'' diameter, ~3.75'' inlet, and 12 straight blades. Motor is 1/2hp 230v 3phase 3450rpm. The other side of the motor has a centrifugal "squirrel cage" type blower on it which I've gathered is no good for our application, so it is irrelevant and would not be used (more on that later).

I've found some information at the Kooltronic website, although there is nothing that matches up exactly to what I've found. The dimensions of the housing in this are the same as the housings I've found, though the part #'s are different and obviously they only show a single stage blower.

In my mind, the design of this blower will nearly double the pressure capability of a single, while flow will stay essentially the same. Is my thinking correct? I'm a newb so take it easy on me :laugh:

Going by the numbers at the Kooltronic site (don't know if they are correct), I am thinking I will need 4 of these blowers (8 wheels) to get a capacity that I'm happy with @ 3450rpm. Increased rpm.....??

My current idea is to use 2 motors to drive 2 housings each. I will take off the "squirrel cage" blower from the opposite side and mount the radial blade blowers, making the necessary changes for the housing to work correctly with "reverse" rotation.

So my question is; what do you guys think? Are these feasible? How do you think they'll perform?

Thank you for any advice you may have!

[bruce]

Welcome to the forum Mark!

Pics are not a problem plenty of space.

We were all newb's at one time and I'm sure we'd all say we are still learning when it comes to our flowbench addiction.

I personally can't add any advice on the blowers but I'm sure someone will come along that can . . . this forum incompasses the world and everyone is on different time zones but eventually they show up.

Again welcome to the forum!

[Tony]

Hello Brooks, welcome to the Forum.

Now this is mighty interesting. Sort of like a giant two stage vacuum cleaner motor on steroids.

The main problem that I see is the motor speed and rotor diameter combination is only going to develop perhaps seven inches of pressure per stage, maybe fourteen or fifteen inches total with both stages in series. Another rough guess might be 150 CFM with half a horsepower.

But all is not lost. The motor is three phase which is good, and it means you could possibly operate it off a VFD and run it at greater than 60Hz. If for example, you run it at 120Hz, that will double the rpm, and create four times the developed pressure. But it may not require anything like double the motor speed or sixty inches of pressure to work quite well in a flow bench.

The other concern is that half a horsepower is not a lot of available drive power, and the motor may be quite easily overloaded unless the flow is sufficiently throttled, and the CFM numbers kept suitably low.

But a very interesting piece of hardware to be sure.

[Brooks]

It's good to be here Bruce!

Thanks for the input Tony. Your thoughts are similar to mine with regard to these blowers. It is good to have outside opinions though, since this is all new territory for me.

My biggest concern is the motor HP. What has your experience been with HP requirements on your large wheel? Or, what is a guesstimate total HP required to flow 800-1000cfm @ 28''? Obviously that is a very "blanket" type of question to ask, but I am just trying to get a very rough idea if these motors are even in the ballpark.

I am thinking that 4 of these housings can perform more than adequately, given the right HP and RPM. I can't fathom that 8 10'' wheels won't work when 12-15 little vacuum motors do.

So let's say I use 4 of these housings, each powered by 1 of the 1/2hp motors, essentially making 2hp available drive. I am thinking a VFD will probably be required (and nice to have) to get a CFM capability I'm happy with. Do you think that will be asking too much of those motors?

Only reason I'm so set on these motors is I can't buy the housings separate. They're a package deal only, or so I'm told.

Thanks again, the help is invaluable

EDIT: Oops, I found the answer to my hp questions elsewhere on the forum. I've been reading like crazy and it's all still a bit overwhelming so I can't recall all that I've read. The information here goes deeper than I imagined, and I thank all of those who contributed!

[Tony]

Hi Brooks, it really comes down to drive horsepower and efficiency. But 40% efficiency might be a reasonable starting guess.

A VFD is an excellent idea, and pressure goes up with rpm squared, so not a lot of extra speed will be required to get some very respectable pressures. It is the lack of available horsepower that will limit you.

If you are expecting 800 CFM at 28" that works out to about roughly 3.5 air horsepower. (psi x CFM / 229)

So your blower drive motor might need to supply anything from 7Hp (50% efficiency) to 10Hp (35% efficiency) regardless of anything else.

My original guess for those blowers was 14" pressure at 150CFM which is roughly 0.32 air horsepower. That may have been a bit optimistic with only a half horse drive motor.

[Brooks]

Thanks again Tony, I got the same numbers after I did some more looking and found your post about required drive horsepower. I'm going to go back and see if I can come up with 2 5hp motors. I'll update with what happens.

[Sir Yun]

I found a similar blower

9000 liter/min = aprx. 530CFM @ 2kPa (about 0.29 psi- 20 cm H20). watts specified seems to add up as well

i'm not shure about the capabilities for producing higher pressures but as i flow heads of maybe 150max i should be allright in the air quantity dpet. :;):

[Tony]

Most of these larger types of blowers have induction motors, and so the speed will be pretty well fixed at around 2,900 rpm (50 HZ) or 3,500 rpm (60 Hz) depending which country you live in.

A pretty good guess of developed pressure can be made by just measuring the rotor diameter.
To just reach thirty inches of pressure would require a rotor of around 24" diameter at 2,900 rpm, or about 20" diameter at 3500 rpm.

As pressure increases with tip speed squared, either slightly more speed, or a slightly larger diameter rotor will increase developed pressure significantly.

Unfortunately, going the other way, a similar decrease in rotor diameter will greatly diminish the developed pressure. A 10" to 12" rotor will only develop one quarter the pressure of a rotor twice the diameter.

The conclusion being, that higher rpm, or a larger diameter rotor is a much more efficient solution than stacking rotors in series to increase pressure.

Having now built a couple of high speed blowers, a step up pulley drive system is the worst solution. A VFD is far better. Run the motor at 100 Hz (or whatever) to reach the required pressure, and the VFD can also then be used to set and control test pressure.

If you are patient and frequent the machinery junk yards and auctions, a proper industrial high pressure blower may eventually fall into your hands at a friendly price.

I very recently scored an absolute beast of an air blower. It has a 42 inch diameter rotor and a 28 Hp motor. Should be good for 90" pressure at well over 1,000 CFM flat out. I have no plans to use it at this stage, but it would make for an interesting future project.

[bruce]

[Tony]