is a snow blower impellor really just a pump?

[hothead77]

I (my company) have been building and selling snow blowers for some 20 odd years now.In the past 3 we have developed our own snowblower.Although it works very well, there is a problem with consolidating the snow into a single stream as it leaves the chute.This is a non issue for most users.Once it's off the road the job is done-however Some need to load trucks or place the snow in a particular spot.

My hope was that some kind soul might have insight on the turbulance problem at the exit and be willing to share some ideas. sorry about the spelling.

thanks
Mike

 

[smckennz]

Hi Hothead
I know nothing about snow blowers, but had some experience with solids handling fans years ago.
If I understand correctly, the snow and air are forming a mixture at the discharge outlet, and you would prefer a stream of dense snow and the air separate.
If this is the case, there are several things you could look at:
1) You may be moving more air than you need. Try throttling the air flow by putting a piece of metal across part of the fan outlet. The metal should be put across the Inside of the scroll, not the outside.

2) Presumably you are using a centrifugal fan. These also make a reasonable centrifuge, with the snow being flung out to the scroll periphery.Once this separation has occurred is is important to try to maintain it. The air will try to re-entrain the snow in any areas of turbulence or where the air is moving faster than the snow. Any discharge bends should be arranged to curve in the same direction as the fan scroll, otherwise the centrifugal force at the bend will try to make the snow jump to another surface and will be blown apart by the airstream. The use of baffles splitting the duct in two may help as well. The idea is to split the snow and air streams once seaparation has happened. This is used in some dust handling gear. As cold snow tends to stick to metal, I assume you are taking suitable precautions to minimise sticking.

3) If I was you, I would find the best performing snowblower on the market, pull it apart and see if you can figure out what makes it work better than the others.

Cheers

Steve

 

[imok2]

hothead77
I'm just brainstorming, how about a 2 stage blower where 1 stage throws it in a receiver attached to the blower and a 2nd stage blower that throws it into a chute for disposel into a truck,etc. 2nd blower could be detachible

 

[hothead77]

yes imok2 that's just what we do. A helical ribbon feeds the 5 bladed impellor at the center.see pictures at

http://www.snoquip.com.

Web site under construction but you'll see an interesting photo gallery on the machine.

Smckennz - that is a most interesting idea!!
When I view videos of the snow exiting the chute, at times it is obvious that there are 2 distinct streams of snow that interfere with each other.I had never considered that one may be created by air.It comes in definite pulses.If you heared the machine run dry though you would problably be Certian you were right! It has a thrumming sound not heard in other blowers.Also it creates a very strong wind from the chute.I assumed that was good.
I restricted the exit so as to allow only the fastest moving snow at the tips of the impellor blades to exit.This helped casting distance but did not remove the interference that I beleive really is at the root of the problem.Also the smaller exit makes plugging more likly.

Another thought was that the slower snow from the inner part of the impellor(~300 fps) is being hit by the next buckets fast snow(~800 fps) from the outter tip.Still need to look at the geometry of this idea.

The idea of taking the best parts of various other designs is exactly what this blower is.And it is indeed an awsome machine.It is difficult to plug in even the slushist conditions but can cut the infamous "sierra cement"(that results from our freeze thaw cycles).

Perhaps a ring around the impellor face would slow the air intake.I have seen this used but assumed it was for strength.It would really reduce the intake area while allowing the same velocity.

anyway ,great idea- thanks much - feel free to send any others along!

Mike

 

[hothead77]

Must have drank too much wine befor my last post.All the snow leaving the exit is traveling at the same speed - the force is not on a tangent to the impellor house.centrifugal force is outward - how embarrassing!

Still think your right though smckennz.

thanks
Mike

 

[pennpoint]

hothead77
The force that moves the mass is centrifugal until it reaches the tangential outlet, then the force that takes over is centripital. But lets not split hairs. From what I saw from your pictures is that (In my view) your blower blades may need to have larger surface areas. This would mean more mass could be moved and thrown. How large?? Then again your bhp would increase also.
Is there any indication that the screw mechanisms capacity can overcome the blower inlet. Does the snow/ice cake up at the inlet to the blower to where it's inlet is choked.
Possibly a funnel shaped blower inlet would enhance the flow of snow. Looking for intuitive answers.
In your pictures every thing is painted nicely. Is the paint powder coat? What of long term protection. If the screw blades or blower rust, snow and ice WILL stick to it for sure. Low surface friction coeff. coating would be good, like Teflon or UHMW Poly.

Disclamer; I am a Southern California boy and can't say I have a whole lot of snow smarts. Just a few gut feelings here. No! wait I do have a friend who (for 37 years) drives a snow plow in Milo, Maine. Oh yah! I did put snow chain on a car once too.

Good Luck

pennpoint

 

[smckennz]

I think pennpoint may be onto it.
Drumming indicates uneven flow.
What may be happening is snow piling up at the fan inlet and gradually blocks it until the suction increases to the point where it sucks in a chunk. Then the inlet is cleared and the cycle repeats.
If this is happening, then you need either more suction, or a better way of shovelling the snow into the fan inlet - possibly chisel ends on the fan blades at the inlet end that bite the snow off, and the screws arranged to ram the snow in if this is possible. Perhaps reduce the fan inlet hole to increase the velocity, and maybe attach a short tapered screw to the impeller to wind the snow into it like the chisels, but this would add cost. But hey, its not my money.

Hard to do without pictures, and I think you have probably forgotten more about showploughs than I'll ever know.

Good luck

Cheers

Steve