Today's Message Index:
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1. 02:45 AM - Re: Perfect cooling diffuser (Duncan & Ami McFadyean)
2. 04:24 AM - Cooling diffuser (=?UTF-8?Q?R=C3=A9mi_Guerner?=)
3. 06:35 AM - Altrak (Michel AUVRAY)
4. 09:18 AM - Cooling diffuser (=?UTF-8?Q?R=C3=A9mi_Guerner?=)
5. 12:37 PM - Bird for sale (Sven den Boer)
6. 01:11 PM - Re: Perfect cooling diffuser (karelvranken)
7. 05:04 PM - Re: Cooling diffuser (Graham Singleton)
8. 05:50 PM - Re: Perfect cooling diffuser (GLENN CROWDER)
9. 09:44 PM - Re: Cooling diffuser ()
Message 1
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Subject: | Re: Perfect cooling diffuser |
Gilles,
Did you measure air temperature increase across the radiator (i.e. inlet air
temperature and outlet temperature)? Which, in accordance with Boyles Law
would dictate the inlet/outlet ratio; we are not in to compressibility at
our speeds!
I agree that the actual area of these is dictated by the size/type of
radiator core and the amount or air that it is able to pass. PE Irving in
his 1960's book ('Tuning of the Automobile Engine'(?)) stated that the inlet
area only needed to be 1/6th (17%) of the face area of the radiator (with
proper ducting) and cited the early E-Type Jaguar sportcar as an example.
The XS inlet area is about 60%. Mine is 30% (77cm2)and works well. I did not
have the nerve to make this smaller; preferring evolution, not revolution!
But with the experience, it could have been a bit smaller, although I made
no allowance for leakage around the sides of the radiator. My non-adjustable
outlet area is 115% the size of the inlet; which was a guess but the
measured air temperature rises suggest it could have been less.
Rgds.,
Duncan McF.
----- Original Message -----
From: "Gilles Thesee" <Gilles.Thesee@ac-grenoble.fr>
Sent: Saturday, December 02, 2006 1:20 PM
Subject: Re: Europa-List: Perfect cooling diffuser
> <Gilles.Thesee@ac-grenoble.fr>
>
> Duncan,
>
>>
>> What is your ratio(s) of inlet area to outlet area?
>
> What really matters is the ration of outlet area to RADIATOR area. As
> already stated on Contrails, too large an opening won't flow more air than
> a correctly proportioned one, since it is the radiator that governs the
> flow in the duct.
> It may help to figure the radiator duct system as a duct with 3 valves in
> series. The middle valve is the radiator. As it is partly closed, opening
> the other valves more than necessary won't change the overall throughput.
> There is no use opening the outlet more than about 1 time the radiator
> frontal area, you would only add drag without increasing air flow through
> the radiator. Drag decreases as you reduce outlet area by means of the
> cowl flap. In cruise, outlet area should be smaller than the inlet area to
> achieve minimum drag. It is advisable to construct the adjustable cowl
> flap with a range of openings from 1 time the radiator area to near zero
> (power descent on a cold day).
>
> In our setup, inlet area is 25% of the radiator frontal area, whereas exit
> cowl flaps can be adjusted from 70% to 0% of the radiator area (410 cm).
> We currently cruise with flaps adjusted to 18% of the radiator area, or
> less on cold days. On summer hot days, best cruise (75% power) is with the
> exit adjusted at about 28% radiator area. Of course we open more in a
> prolonged climb.
>
> During flight tests I installed a data logging system to check adequacy of
> the pressures and temperatures.
>
> Adjusting CHT and oil temps to within 5C of desired temperatures is a
> breeze, and we found no special limitations concerning ground run time. A
> thorough cooling study is really worth the time and hassle.
>
> Hope this helps,
> Regards,
> Gilles
> http://contrails.free.fr
>
>
Message 2
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Subject: | Cooling diffuser |
Salut Gilles,
My question regarding cooling on the ground is because all Rotax equipped Europas
are known to overheat very quickly on the ground. I know some guys who say
they do not overheat, but I have often observed them taxiing very fast to the
holding point to be sure they are aloft before reaching the boiling point. Again
the design of the Europa cowl is not optimal but cooling in flight is very
effective. On the ground however it does not work properly. I am now convinced
that the main cause for this poor cooling on the ground is the propeller. Most
Europas are fitted with Warp Drive props or Airmaster hub Warp Drive blades
combination. Those blades are narrow at the root and not very much twisted. Therefore
they do not provide a lot of air flow where the air inlets are located.
On the other hand, most MCR are using the MT prop whose design is just the
opposite: very wide blades at the root and a lot of twist which is a lot more
effective ventilator.
My own fix for the Europa cowling is a variable air scoop, below the existing inlet,
ahead of the radiator. Theoretically it is very bad, but it works! It works
because this additional inlet is located farther from the propeller axis,
therefore receiving more air flow. Sure this adds a lot of drag, but who cares
about drag during taxi and run-up? The scoop is positioned back to neutral
just before take off and can be closed to blank the radiators at cruise and descent
at cold temperatures.
Remi Guerner
Europa F-PGKL
No problem on the ground.
During first run ups we ran the engine as long as 30 minutes continuous
with several full power runs then fast idle periods.
I did not take special measurements on the ground, only monitoring CHT
during warm up, taxi, etc...The aircraft was test flown from - 14C to +
37C OAT.
I can do take the measurements you require when flying with a helpful
passenger, but since we're in autumn, you'll have to wait until summer
for hot day conditions.
Best regards,
Gilles
http://contrails.free.fr
Message 3
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Message 4
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Subject: | Cooling diffuser |
Salut Gilles,
My question regarding cooling on the ground is because all Rotax equipped Europas
are known to overheat very quickly on the ground. I know some guys who say
they do not overheat, but I have often observed them taxiing very fast to the
holding point to be sure they are aloft before reaching the boiling point. Again
the design of the Europa cowl is not optimal but cooling in flight is very
effective. On the ground however it does not work properly. I am now convinced
that the main cause for this poor cooling on the ground is the propeller. Most
Europas are fitted with Warp Drive props or Airmaster hub Warp Drive blades
combination. Those blades are narrow at the root and not very much twisted. Therefore
they do not provide a lot of air flow where the air inlets are located.
On the other hand, most MCR are using the MT prop whose design is just the
opposite: very wide blades at the root and a lot of twist which is a lot more
effective ventilator.
My own fix for the Europa cowling is a variable air scoop, below the existing inlet,
ahead of the radiator. Theoretically it is very bad, but it works! It works
because this additional inlet is located farther from the propeller axis,
therefore receiving more air flow. Sure this adds a lot of drag, but who cares
about drag during taxi and run-up? The scoop is positioned back to neutral
just before take off and can be closed to blank the radiators at cruise and descent
at cold temperatures.
Remi Guerner
Europa F-PGKL
No problem on the ground.
During first run ups we ran the engine as long as 30 minutes continuous
with several full power runs then fast idle periods.
I did not take special measurements on the ground, only monitoring CHT
during warm up, taxi, etc...The aircraft was test flown from - 14C to +
37C OAT.
I can do take the measurements you require when flying with a helpful
passenger, but since we're in autumn, you'll have to wait until summer
for hot day conditions.
Best regards,
Gilles
http://contrails.free.fr
Message 5
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I am putting my bird up for sale, moving to a 4-seater.
http://www.planecheck.com?ent=da&id=6510
Nice detail, that this aicraft will be featuring in the January number of
Aerokurier for a pilot report on the Trigear XS.
Great fun, outperforming a C!82 !
Best Regards,
Sven den Boer
A169
PH-SBR
Message 6
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Subject: | Re: Perfect cooling diffuser |
Gilles, Glenn and all,
Here some pictures of my cowl modification; indeed inspired by Mustang P 51.
Karel Vranken.
----- Original Message -----
From: "Gilles Thesee" <Gilles.Thesee@ac-grenoble.fr>
Message 7
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Subject: | Re: Cooling diffuser |
Remi
Another way to improve cooling on the ground is exhaust extraction, this
is how the EZ boys do it. I don't think anyone has tried it yet on a Europa.
You are right about the Warp Drive props. I had an Arplast PV50, nice
smooth rnning prop and better cooling. Ernst Keppert has the fixed
pitch Arplast which has the same blades and I don't think he has any
problems cooling on the ground either. I should say he has Classic
Europa, not quite the same
Graham
Rmi Guerner wrote:
>
>
> Salut Gilles,
>
> My question regarding cooling on the ground is because all Rotax
> equipped Europas are known to overheat very quickly on the ground. I
> know some guys who say they do not overheat, but I have often observed
> them taxiing very fast to the holding point to be sure they are aloft
> before reaching the boiling point. Again the design of the Europa cowl
> is not optimal but cooling in flight is very effective. On the ground
> however it does not work properly. I am now convinced that the main
> cause for this poor cooling on the ground is the propeller.
>
> Remi Guerner
>
> Europa F-PGKL
>
>*
>*
>
Message 8
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Subject: | Re: Perfect cooling diffuser |
That looks awesome Karel!
Be sure to seal off all around the duct inside so incoming air can only
go thru the rad.
Managing air flow is like herding cats - if theres a way not to cooperate,
they will
find it! On my rad, I welded on aluminum angles all the way around the face
of the rad
making a fence about an inch tall to allow the duct to slip inside. No
funky seals to monkey with!
Glenn
>From: "karelvranken" <karelvranken@hotmail.com>
>To: <europa-list@matronics.com>
>Subject: Re: Europa-List: Perfect cooling diffuser
>Date: Sun, 3 Dec 2006 22:17:45 +0100
>
>Gilles, Glenn and all,
>Here some pictures of my cowl modification; indeed inspired by Mustang P
>51.
>Karel Vranken.
>----- Original Message ----- From: "Gilles Thesee"
><Gilles.Thesee@ac-grenoble.fr>
><< DSC00001.jpg >>
><< DSC00002.jpg >>
><< DSC00003.jpg >>
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Message 9
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Subject: | Re: Cooling diffuser |
Hello Graham
"> Another way to improve cooling on the ground is exhaust extraction,
this
> is how the EZ boys do it. I don't think anyone has tried it yet on a Europa."
How exact is exhaust extraction accomplished on EZ?
How about spraying water on the radiator during extended ground operations
and temps creep high, anyone try this?
Ron Parigoris
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