Different Types of Fans

Maybe they are referring to a rotary lobe blower such as Roots and others? That's not exactly a fan, and runs at higher pressure/vacuum than typical fans. For "other" how about a regenerative turbine blower?

You know this type of fan ? That opens a 5th category for you. Watch Mr.Dyson at youtube - search for "Dyson" and "fan" (that worked in google). But no answer to lobe-fan, sorry..!

M.Regier, Hamburg, Germany

Thats neat. I like the demo of the principle where the guy fills the 10 foot long bag with one breath.

As far as the tariff goes though that machine would fall into 8414.51 Table fan with self contained electric motor of an out put not exceeding 125 W. I would have to verify the motor power output just to be sure. In Canada the tariff further defines the above description at 8414.51.10.00, Table fan with self contained electric motor of an out put not exceeding 125 W, oscillating, variable speed. (In a tariff number the first 6 digits have a global application and definition, after that each country is free to further define and segregate the items within the 6 digit definition)

How do they determine the output power (in watts) of a table fan? Is it the difference between the rotational speed without the blade and with the blade to determine percent of slip?

I believe it is the motor output they are refering to.

Something like this? From Wikipedia: Jump to: navigation, search A Roots blower with two-lobed rotors. Most real Roots blowers' rotors have three or four lobes.
Key:
1 Rotary vane 1
2. Pump body
3. Rotary vane 2
a. Intake
b. Pumping
c. Forced air or air-fuel mixture into intake manifold

The Roots type supercharger or Roots blower is a positive displacement lobe pump which operates by pumping fluids with a pair of meshing lobes not unlike a set of stretched gears. Fluid

Thats it!!!!!

That thing looks like it would create some serious forced air pressure. Sort of a positive displacement fan. Thanks Lynlynch.

You're welcome. Although I now see that Tornado was first with the answer. I've never worked with Roots type blowers, but imagine they would be a maintanence nightmare, due to the close tolerances.

Cheers.

The timing gears (on the end, not shown) have to in good condition, but they are fairly common as superchargers, and regarded as very reliable.

jus' mentioning

The lobes are phased by means of timing gears running in an oil bath; neither drives the other directly. They are good for about an atmosphere or so of pressure difference, and can be pretty damn noisy. I think versions are made with two or three lobes on each shaft, but haven't heard of larger numbers.

OK thanks,

. . . . .Yes I admit I was looking for a quick fix for my total lack of knowledge on IC engines. Maybe some time I'll find the time.....

...Randall

Hi Apothicus,

The lobe type fan would appear to be the simple open bladed type found on desk fans. It resembles the propeller or screw found under the stern of ships and functions in a similar way.

Therefore I cannot agree with the suggestion that a lobe fan has any relationship to the Roots blower which is classed as a positive displacement air pump. These devices where created to provide the air supply to blast furnaces in the mid 19th century and were later adopted for use in the automotive industry to super-charge the air supply to the engine.Running clearances were nothing special and leakage within the casings were an accepted part of life with them.

Daimler used them on petrol engines and later they went on to be used on diesel engines.Detroit Diesels and Commer, (2-stroke direct supply without crank-case compression) are examples of the genre.

Typically they have a 2:1 compression ratio at an optimum efficiency of 80%.

To return to your original question I can identify 9 fan styles which are as follows:

1.Axial flow ,without guide vanes.Compact good for any application working at a low static pressure.eg toilet extract fans

2. Axial flow with guide vanes.Good for v.large vent schemes such as tunnels.

3.Forward curved or multivane centrifugal.Quiet but with a marked load increasing characteristic must be used with care.Air handlers.

4.Straight or paddle vaned centrifugal. Simple non-clogging good for materials transport. Low efficiency unit.

5.Backwards-curved or backwards inclined-blade centrifugal.Non-overloading medium pressure applications for HVAC purposes.A cost effective unit.

6. Aerofoil-bladed centrifugal.Non overloading v.high efficiency used in high volume high power HVAC applications

7. Propeller.As noted non-ducted low power fan eg the lobe fan.

8. Mixed flow. Straight through, used in high static pressure HVAC applications. Big plant applications.

9.Cross-flow or tangential flow. found in fan coil units and domestic electric floor fans.

Hope this helps.

Massey

Isn't the simpl desk fan an axial fan?

Nine !! Please do not tell the WCO that.

Heading 8414 which contains fans, also contains all the other air pumps, compressors etc.

What about Propeller and Backwards Inclined type fans? The former is obvious- hosehold ceiling or window/floor/box fan. The latter, squirrel cage, used in 99% of all residential & most commercial hvac units, is the most common Backwards Inclined fan. There are other types of Backwards Inclined fans, though.