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Point well taken, Bill. However, my cooling was more than adequate with the
old larger ducts, so unless I can get some benefit (like lower drag), I
don't see much point. On the other hand, if I added a turbo producing more
waste heat then that would help there with the same size ducts. I'll
continue to see what I can do with it.
Ed
Subject: [FlyRotary] Re: Downsize inlet duct First Flight
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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