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Date: Fri, 21 Jan 2005 13:41:58 -0500
Subject: Re: [FlyRotary] Re: changed to Octane
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From: Jerry Hey <j-winddesigns@thegrid.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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> Lynn,  I suspected the same but without the experience to back it  up. 
>  I  had asked Rolf  just a few minutes ago what velocity the mix would 
> reach in the p port runner and he calculated around 13,000 fpm for 
> 6000 rpm.  At this speed the suction stroke is repeating every .0075 
> of a second.  Air/fuel mix  moving through the intake at such a 
> velocity might even  have a scrubbing effect on the runner walls as 
> opposed to a wetting effect.   Even if this is wishful thinking on my 
> part, I don't see fuel building up on the inside of the bends to any 
> appreciable amount.   By the way,  I am sure you have seen various  p 
> port intake manifolds.  The one I had a chance to look at was a 90 
> degree sweep with a carb mounted on top.  I think it was about 12 
> inches long.  Does that sound right to you? It may have been shorter.  
> It was definitely a sweep so no problem with fuel deposition in that 
> case.  I saw this car run through about $500 worth of rubber  burning 
> out just because we were watching.   Jerry


> I cannot picture cracking motor fuel into a number of compounds in the
> milisecond or two it spends in the runner. While there may be a number 
> of differing
> velocities measurable in the runners, they will not be far enough 
> apart to
> affect the product be burned. When the mixture is exposed to the 
> 375-400 degree
> rotor face, and then compressed about 9 times its volume, I suggest 
> that it is
> more likely to recombine any faulty mixture.
>
>  I can picture wetting the outside of a turn in that runner at low
> velocities, and perhaps if a very large number of other situations 
> exist inside that
> engine, you could get it to detonate. But detonation would have to be 
> the goal of
> the experiment, and getting it to work would be difficult. The NA 
> rotary does
> not detonate under anything like ordinary use.
>
> So if the engine was highly loaded at low revs, and the gross mixture 
> was
> reduced from near ideal to just leaner, with a very low octane fuel, 
> it might be
> possible to get it to detonate. Detonation is charge temperature 
> dependant.
> Nothing else.
>
> A long list of factors are involved in producing the high charge 
> temperature.
>
> Ignition timing, octane, RPM, plug heat range, carbon deposits and oil
> fouling are just a few.
>
> Fuel dropping out of suspension suggests a change in velocity in a 
> fixed
> system.
> However moving from a homgenious mixture to something less just takes 
> the
> removal of some energy from the flow, such as reducing the throttle 
> setting just
> slightly, or inlet air temp dropping slightly. The precip of fuel 
> droplets
> makes the mixture look leaner to the engine (any engine). Remember 
> pulling the
> choke out on cold days? The mixture that runs fine on a warm day (rich 
> enough)
> will not even allow a start on a cold day, because that mixture 
> precips into
> large droplets and (due to reduced surface area) becomes too lean to 
> even light.
>
> A NA rotary can be loaded on the dyno and taken from too rich to run, 
> through
> too lean to run, with no damage at all.
>
> Lynn E. Hanover
>
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