Ed, you might get even better cooling, although no change in drag, by
keeping the opening large, but using the smoothing technique that you tried
on the smaller opening.
Bill Schertz
----- Original Message -----
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, September 03, 2003 7:18 PM
Subject: [FlyRotary] Downsize inlet duct First Flight


> The modification (reduction) of my radiator inlet duct area from a total
of
> 48 square inches to 33 square inches is dedicated to Rusty (for obivious
> reasons {:>))  Sorry, just couldn't help myself, Rusty,  - the devil made
me
> do it.
>
> Ok folks, made the first flight today with my reduced/reshaped radiator
> > inlet for the left evaporator core.  The right evaporator core was left
> > unmodified to  provide a safety net sufficient to do the pattern and
land
> if
> > take off temps exceeded expectations.  Fortunately, that was not
> necessary.
> > OAT on first take off was a humid 85 degrees.  No temperature increased
> > noted during ground run up, so launched and made max rate of climb, not
> > seeing any abnormal temp increase I left the pattern and continue Max
rate
> > climb to 4500 MSL.  Max temp of coolant during climb was 210F (normal
for
> > max rate climb at these OAT temps is 205F), Max oil temp was 200F
nominal
> > for max power climb. Max temps were reached about 2/3 of the way through
> the
> > climb.
> >
> > In level flight, my coolant temperatures normally run 5 degrees colder
> than
> > my oil temp.  Today my coolant and oil temps were the same.  So average
> > coolant temp was increased by 5 Degrees F.  Total radiator inlet duct
area
> > was decreased from 48 square inches to 33 square inches.  24 Square
inches
> > for the right inlet duct and 9 square inch inlet for the modified right
> > duct (See attached photo for comparision). Probably some drag benefit,
but
> did not try to investigate that
> > aspect.
> >
> > I flew to an airfield 50 miles away to have my transponder recertified
and
> > when I launched out of it, the OAT (ground level) was 92F
> >
> > After level off I ran at different power settings to see the effect.
> >
> >  5800 rpm burning 11.9  GPH at 4500  MSL with OAT at 78F My oil and
> coolant
> > were both 190F.
> >
> > 5400 rpm burning 9.6 GPH at 4500 MSL with OAT 80F My Oil and coolant
were
> > both 185F
> >
> > 5200 (Around my normal cruise rpm)  burning 7.25 GPH at 4500 MSL with
OAT
> 80F My
> > oil and coolant were both  180F
> >
> > In summary, the 33 % reduction in total  radiator inlet area appeared to
> > have increased coolant temps by an average of 5 Deg above the normal
(the
> > old duct).  It could be that both the remaining radiator and perhaps the
> oil
> > cooler are rejecting any additonal load with no problem.
> >
> > It appears that smoothing out the path for the air from inlet to
radiator
> > surface has benefited the cooling situation.  It could be that
additional
> > heat may be rejected by the right (second in series) radiator as the
> coolant
> > it received from the left radiator was probably now a bit hotter. I also
> > observed that the plate of the PSRU covers an area 3 " in from top to
> bottom
> > of the rear of each radiator and the plate is only 2" from the rear of
the
> > fins at its closest, so that is obviously not helping flow, the Ross
Bell
> > housing did not, so a bell housing might improve flow conditions .
> >
> >  I strongly suspect I would probably  find that a similar  reduction of
> the
> > right radiator inlet duct to 9 square inches  would see my coolant (and
> > probably oil) temps increase considerable more than another 5 F.
>
> OAT at  ground level was 94F when I landed, so not the hottest of days,
but
> not the
> > type I normally prefer to fly in.
> >
> > >From what I have seen so far, I think it worth pursuing a reduction
with
> the
> > right radiator duct.  I will probably not reduce it as much for the
reason
> > mentioned above. With some other things to take care of, probably won't
> get
> > to it until later part of Sept at the earliest.  But, I have no problem
> > flying with current asymmetrical ducts, so will leave it as is for the
> time
> > being and collect some more data.
> >
> > It it appears that some cooling benefit is derived from providing a
> smoother
> > transition from duct to radiator (even if far from a perfect
> implementation
> > of the K&M approach) than my old duct provided.  The volume of the duct
> was reduced by at least 60%, so while hard to tell from photos the white
> "filler" material actually fills most of the duct.
> >
> > Oh, yes, as an aside, its been 25 hours since I replaced the spark plugs
> and
> > right on schedule - on the way back, I got the first SAG (Sparkplug
> > Attention Getter)  indication.  So it appears 25 hours on 100LL about
the
> > average time for replacing plugs in my case.  I finally got a spark plug
> > cleaner, so need to clean a set (as the electrods do not appear worn)
and
> > see if getting the lead off the ceramic  cone helps any.
> >
> > Best Regards
> >
> > Ed Anderson
>
> Ed Anderson
> RV-6A N494BW Rotary Powered
> Matthews, NC
> eanderson@carolina.rr.com
>


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