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Date: Tue, 14 Sep 2004 16:42:48 -0400
From: echristley@nc.rr.com
Subject: Re: [FlyRotary] Re: Limp home mode
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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----- Original Message -----
From: "Smith, Randy" <randy.smith@intel.com>
Date: Tuesday, September 14, 2004 2:29 pm
Subject: [FlyRotary] Re: Limp home mode

> 
> 
> >-----Original Message-----
> >From: Rotary motors in aircraft
[flyrotary@lancaironline.net] On
> Behalf Of
> >echristley@nc.rr.com
> >Sent: Tuesday, September 14, 2004 11:24 AM
> >To: Rotary motors in aircraft
> >Subject: [FlyRotary] Re: Limp home mode
> >
> >I would think that a larger effect would be the
> >intake air combined with raw fuel cooling the faces
> >and housing.  Have you considered that an extremely
> >lean or rich mixture would give you the same effect?
> 
> How would it do that?  As soon as it fires it
generates heat.  Not
> trying to be flippant, I want to understand what
you mean.  I realize
> that cooling is realized with an extremely lean
mixture by causing 
> lesspower and therefore less heat to be generated.
 I also 
> understand that
> an extremely rich mixture results in unburned fuel
that carries away
> some of the heat.  Is this how it works?  Please
correct me if I am
> wrong.
> 

Yes, I was thinking of unburned fuel.  But it wasn't
a good thought.  I would cool (at least to some
extent), the internal surfaces.  The problem is that
the mixture would ignite so afterward...like as soon
as it hit the muffler 8*)

At least that way you'd need less power as you'd
have just lost a few pound by exploding the muffler
off the airplane.

> OR 
> 
> Are you suggesting that in my every other firing
scenario a lean or 
> richmixture working its way through a non-firing
face would cool 
> the rotor
> face more than just air at the expense of fuel
consumption?
> 
> How fine grained is the mixture system with fuel
injected engines?  Is
> it possible to vary the mixture for each face of
the rotor?  Something
> like "normal-lean-normal-lean-normal..."
> 
> -Randy


Yes, unburnt fuel and unused air will both carry
away a lot of heat.  EGT goes down both lean and
rich of peak.  Closing the throttle will mean less
heat is produced, but there would still be a
stoichiometric mixture that exotherms the same
amount of energy per lb of mixture.  Cut back the
fuel (or add some that can't be burned), and the air
left over will take some heat away without adding
any back.

I don't think it would help to vary the mixture
between faces.  The time periods are so short that
it's just going to average out anyway.  It's the
dynamic equilibrium of the temperature that you want
to lower.

Leaning to 30% power might possibly (with lots of
luck and a cherry on top) keep you at altitude as
long as you need, but I'd follow Tracy's
recommendations.  Instrument the engine properly and
get on the ground at the first sign of trouble.