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From: "Greg Ward" <gregw@onestopdesign.biz>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2603730@logan.com>
Subject: Re: [FlyRotary] Re: Supercharging
Date: Tue, 18 Dec 2007 09:18:32 -0800
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Thanks Ed;
The below is one of the reasons for looking at a SC in the first place. 
Specifically on a missed approach and go-around, in a ticklish spot, the 
responsiveness of the SC vs. the time it takes a TC to spool up, might be an 
advantage.  And, as I have been hearing, back pressure (from a turbo) kills 
HP in a rotary.  Maybe I'm picking the nit a little hard here??
Greg

<snip> There are certainly advantages to a supercharger in some 
applications - and
> to a turbo in others.  The immediate boost response of a roots type blower 
> is about the only reason they are the bedrock of the top end drag racers. 
> Unlike a turbo which needs some time to spool up, the roots type 
> superchargers produce boost much quicker.  There are several types on 
> impellers designed to increase the efficiency of the root types blowers, 
> but I am not aware of any that approach the centrifugal impeller in 
> efficiency.
>
>
> While the turbo uses the "free" exhaust flow energy,   you do get back 
> pressure with the turbocharger that effects (decreases) engine power so 
> that has to be considered also.  But, overall, its my understanding that 
> the turbo is a bit more efficient and also does not decrease crankshaft 
> power (at least not as much) as a supercharger.  However, there may be 
> other reasons (like not having to have all that heated exhaust pipes 
> routing around to and from a turbocharger) as well as cost for using one 
> vs the other.
>
> Gee, its great to be back {:>)
>
> my 0.02
>
> Ed
>
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