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Date: Thu, 26 May 2011 09:39:40 -0400
From: Ernest Christley <echristley@att.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Blower design
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Charlie England wrote:

> Not to rain too much on the parade of ideas, but I'd be fearful that 
> anything except a properly engineered blower assembly will consume more 
> power than it will add to the engine's output. Much better minds than 
> mine say that one of the reasons small turbines are so inefficient is 
> excessive leakage past the perimeter of the blades, due to the ratio of 
> the gap area to the overall area of the turbine.
> 
> Charlie

That is the biggest hurdle to overcome.  To overcome the problem the shroud must fit VERY tightly.  It's a much more 
complicated manufacturing process, but a significant percentage of the blowers you will find have the top-hat on the 
impeller blades.  Effectively, they have a cast in shroud with 0 clearance.  That was the concept I was trying to tag 
onto with the "thick cylinder with drilled holes" concept drawing.