With the start of the leaf raking/blowing season just a month away, I have been thinking of a way in which I could make my old leaf blower more effective so I can spend less time doing leaf blowing. I know that I can go out and buy a more powerful leaf blower, but before I do that there is an idea that I have that I believe will increase the effectiveness of my current leaf blower.

It would involve building an air amplifier attachment for my leaf blower which would increase the overall air flow by making use of the Coanda Effect. I was inspired with this idea after recently watching a YouTube video on how the Dyson air multiplier fans work.

Please reference the drawing below:

enter image description here

I want to point out that this is a cylinder-shaped attachment which would be made out of a lightweight yet durable plastic and that it would be hollow. Also, it would be designed to attach to the standard leaf blower tube which is 3.5 inches in diameter.

Would this air amplifier attachment increase a leaf blower's effectiveness?


This attachment would most likely need to be screwed on to the tube or held on with a couple of latches otherwise the back pressure inside of the attachment would likely cause it to pop off.


probably not, here is why.

the coanda effect describes how a moving mass of air entrains nearby air and sets it in motion. So if we start with an extremely fast-moving but small jet of air, with it we can urge a much larger mass of air into motion. However, energy conservation dictates that the kinetic energy of the large mass of air set into motion be less than or equal to that of the small high speed jet, and this means that the large air mass will be moving slower than the high-speed jet.

Key to making a leaf-blower effective is that the dynamic forces exerted on particles of stuff by the moving air be greater in magnitude than gravitational forces on those same pieces of stuff. If this condition is met, then particles of stuff are successfully propelled by and carried along with the air flow. The dependence of this condition on the flow velocity is nonlinear and extremely steep, with a relatively small flow rate increase having a very large effect on how heavy the particles can be while still getting carried in the flow.

This means the key to effective leaf-blowing is making the nozzle exit velocity of the air jet as high as possible, rather than distributing the jet flow over the largest possible area of the ground with the leaves on it.

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    $\begingroup$ This is the answer. I'd add two things: 1) in addition to conversation of energy, you have conversation of momentum 2) the nozzle the OP wants to build would introduce an additional loss of pressure, meaning the same fan achieves a lower volume flow rate => lower velocity. $\endgroup$
    – mart
    Sep 1 '20 at 6:21
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    $\begingroup$ I hope the conversations of energy and momentum are about conservation of energy and momentum. The one take-away I got from my research, consistent with this answer is that it's an overall loss when the OP's question is the consideration. $\endgroup$
    – fred_dot_u
    Sep 1 '20 at 9:15
  • $\begingroup$ I agree with the answer and the comments, those are things that I did not think about. Also, there would be the issue of how to secure the attachment to the tube because there would be a lot of back pressure inside of the attachment. Unless it is screwed on or held on with clips, it would likely pop off. $\endgroup$
    – user26803
    Sep 1 '20 at 11:56
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    $\begingroup$ You can optimize the flow for things like dust removal by entraining other air with it, but as already discussed you'll lose "knock-down" power. Some com[pressed air nozzles work this way. So the proposed solution might work for very loose leaves only. $\endgroup$
    – Tiger Guy
    Sep 1 '20 at 19:54

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