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Subject: Re: [FlyRotary] Re: engine exhaust
From: Mark McClure <markmcclure@me.com>
In-reply-to: <list-5367170@logan.com>
Date: Fri, 27 Jan 2012 10:22:59 -0800
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References: <list-5367170@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>

Let me first clarify, my reference was for a Turboprop or turboshaft. Tracy is correct that on TurboJets and TurboFans the 75% Air is routed around combustion chamber, cools it and then mixes with the hot gases to provide thrust. In a turboprop/shaft engine almost all of the heat energy is used up by the turbines that it passes through. In fact on the C-20J After a two hour flight you could put the exhaust covers on instantly because the exhaust tubes were not hot.

A traditional auto turbo is a turbine wheel and a compressor.  Take two of them and you almost have all the parts you need to build a cheap Turboprop putting out a few hp.  

Bob I think what you are saying is that it would be improbable to use the air to cool the oil or water temperatures and so I would have to route the air directly over the combustion chamber, just like in the turbine. Basically drilling additional holes in the rotor housings.

So I guess my thought is to try and harness that exhaust energy we are producing to provide for something. Maybe have the turbine wheel turn a generator/alternator.

Mark


Glasair SII - 30% complete
13b MSP - 5% complete


On Jan 27, 2012, at 9:26 AM, Rogers, Bob J. wrote:

> If you add another turbo to capture the remaining exhaust gas, the
> compressor portion will generate compressed air, which can be directed
> to flow over an oil cooler or a radiator, but the air will be much
> hotter than the outside air available for cooling.  When the air is
> compressed, it is heated by as much as 100 degrees.  The temperature
> rise is a function of the amount of compression.  That is why you need
> an intercooler before such air is routed to an engine intake for
> combustion.  I doubt that the air from a compressor stage of the turbo
> would be cool enough to help reduce the water or oil temperature very
> much (if at all) and the volume of air would not be significant compared
> to the volume of air available in the free stream of outside air.  Plus
> you have the added weight of the turbo to deal with.  In short, it would
> not work.  
> 
> Bob Rogers
> Mustang II, powered by Rotary 13B Turbo
> 
> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
> Behalf Of Ernest Christley
> Sent: Friday, January 27, 2012 11:09 AM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: engine exhaust
> 
> Mark McClure wrote:
>> 
>> The 13b MSP is putting out exhaust temps of 1600F. So using the same
> principles in reverse, the remaining energy powers a compressor (turbo)
> and that air is then used to assist in the cooling. 
>> 
>> So the question is: What have I oversimplified?
>> 
>> Mark
>> 
>> 
> There is so much about the rotary that is completely unexplored.  An
> option that I'm investigating with my installation is to have a blower
> attached to the shaft between the engine and PSRU.  The goals are:
> - to make more of the propeller efficient by removing the high pressure
> area from between it and the cowling
> - remove that high pressure area at the nose and
> - use it to increase manifold pressure
> - increase the manifold pressure
> - in a extremely simple and lightweight method.
> 
> I've seen the videos of people making jets out of turbos.  I've not run
> a single number, but it seems like it would be possible to duct the
> output of a really thick radiator to the input of a large turbo.  The
> pressurized air would cool the turbo and get heated in return, then
> combined with the exhaust to produce thrust.  I do seem to remember
> someone on this list doing an analysis and coming to the conclusion that
> a "rotary jet" was not viable, but if you're getting a list of drag
> reducing benefits, dealing with the exhaust (one of the worst pain
> points we've had to deal with),  AND getting some measurable thrust ...
> you'll get listed as a hairy chested hero.
> 
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