Today's Message Index:
----------------------
1. 07:26 AM - inlet and outlet area (Mark A. Wood)
2. 08:44 AM - Re: Run-in and Break-in (Grant Corriveau)
3. 09:08 AM - Re: inlet and outlet area (James R. Cunningham)
4. 09:09 AM - Re: Run-in and Break-in (Scott Bilinski)
5. 09:21 AM - Re: Run-in and Break-in (James R. Cunningham)
Message 1
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| Subject: | inlet and outlet area |
--> Engines-List message posted by: "Mark A. Wood" <Mark.Wood@uvm.edu>
Jim
One of the nice things about this list is that what some people put
out as information that may not be of value is of great value to
others. Your information is in that realm for me on this issue.
The inlet and outlet area is also something I have been working on,
and you gave some great info on that. I had just looked at the inlet
of a Cessna 150 and gone with an approximation of that. I have ~60
sq. in. and now I see that this is on the edge so I will remember
this if cooling is ever marginal.
I have a question for you on the outlet area. You have a factor of
~4X for the outlet. I had heard that it should be on the line of
1.5X. I have a 2.5 inch vertical opening between the bottom of my
cowling and the bottom of the firewall. With the opening pointing
backwards this should give me a partial vacuum and ~100 sq. in.
Would this leave me short on the outlet area?
Thanks for any help.
Mark
>
>You didn't give enough information to run the calcs appropriately. For
>example, what is the approximate pressure altitude where you will be
>doing the run and your intended dISA during the run?
>
>I tried a couple of trial calculations at an approximated pressure
>altitude of 2000 feet and a dISA of +40 degrees F (a 100 degree day)
>using two different face rise conditions. Depending upon some of the
>other assumptions you make, the required cfm ranges from roughly about
>1960 cfm to somewhat over 3200 cfm. Slightly more than your 300 cfm
>leaf blower will provide. But if you really think 300 cfm is adequate,
>then its your engine and your call. The calculations I ran were not
>specifically for your conditions and your mileage may vary. I doubt
>that it will vary by a factor of 10 to 1.
>
>As an aside, and as a rough visual comparison, an airplane producing 100
>hp with 54 sq.in. of inlet area has to fly at least 99 mph at a pressure
>altitude of 2000 ft in order to cool adequately at +40 dISA. Fifty-four
>sq.in. at that speed is a flow rate of 3267 cfm and even so, the CHT's
>will be right at the upper limit. The required outlet area for that
>condition would probably be on the very loose order of 204 sq.in, but I
>didn't stop to look at the actual number.
>
>I'm sorry I couldn't be of more help or provide more encouragement.
>
>All the best,
>Jim Cunningham
>Cunningham Engineering Associates
>
--
Mark Wood
Assistive Technology Consultant, VT I-Team
Center on Disability and Community Inclusion
University of Vermont
Message 2
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| Subject: | Re: Run-in and Break-in |
--> Engines-List message posted by: Grant Corriveau <grantc@ca.inter.net>
Jim,
I find your calculations relevant to a mod I've been contemplating for my
Zodiac with a 100HP CAM100 (Honda Conversion)...
I currently have the rad on the nose/chin -- works okay, but I have some
issues about heat into the engine room, vibrations on the radiator itself as
it is mounted on the engine PSRU directly, drag....
I have toyed with the idea (ala some famous WWII aircraft most notably the
Spitfire), that moved the rad into the wing. My Zodiac has a fat wing where
I could easily accomdate 1 or 2 radiators.... but I had no idea of the
amount of airflow I would have to provide.
Your numbers at least give me some ballpark figures. Any chance you could
supply the formula that you are using?
--
Grant Corriveau
C-GHTF / HDS / CAM100
> As an aside, and as a rough visual comparison, an airplane producing 100
> hp with 54 sq.in. of inlet area has to fly at least 99 mph at a pressure
> altitude of 2000 ft in order to cool adequately at +40 dISA. Fifty-four
> sq.in. at that speed is a flow rate of 3267 cfm and even so, the CHT's
> will be right at the upper limit. The required outlet area for that
> condition would probably be on the very loose order of 204 sq.in, but I
> didn't stop to look at the actual number.
>
> I'm sorry I couldn't be of more help or provide more encouragement.
>
> All the best,
> Jim Cunningham
> Cunningham Engineering Associates
Message 3
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| Subject: | Re: inlet and outlet area |
--> Engines-List message posted by: "James R. Cunningham" <jrccea@bellsouth.net>
Mark A. Wood wrote:
>
> The inlet and outlet area is also something I have been working on,
> and you gave some great info on that. I had just looked at the inlet
> of a Cessna 150 and gone with an approximation of that. I have ~60
> sq. in. and now I see that this is on the edge so I will remember
> this if cooling is ever marginal.
Mark, I was actually using one of the Lycoming engines to approximate
the calculations since we were just talking in general terms. If you
have a Cessna 150 rather than a 152, then you are using a Continental
and your pressure drop vs. mass flow requirements would be somewhat
different, so you should treat what I said generically rather than as a
solution for your particular condition. In fact, folks with Lycomings
should also do the same, since we didn't specify actual conditions in
sufficient detail to do a cooling design for a specific installation. I
repeat, no one who reads this thread should base his cooling design on
these particular numbers.
> I have a question for you on the outlet area. You have a factor of
> ~4X for the outlet.
Not really. The relationship between inlet and outlet area is
non-linear and doesn't follow a rule-of thumb. You can set up other
flight scenarios where the outlet ratio isn't even close to 4X the inlet
area. It can be much larger (or much smaller).
> I had heard that it should be on the line of 1.5X.
The relationship is non-linear. There is no constant multiplier that
can be used, and no effective rule-of thumb. If you plan to forego cowl
flaps, then you must design for climb cooling for your specific engine
and that will also establish the lower speed limit for continuous climb.
Usually, that procedure will also result in a noticeable hit on cruise
speed.
> I have a 2.5 inch vertical opening between the bottom of my
> cowling and the bottom of the firewall. With the opening pointing
> backwards this should give me a partial vacuum and ~100 sq. in.
> Would this leave me short on the outlet area?
Depends upon your airspeed at the time. I can't answer specific
questions for use in actual design because of the potential for
incurring implied liability litigation at some time in the future. I can
say this: Required outlet area increases very rapidly with decreasing
climb speed and soon becomes larger than the frontal area of the
aircraft itself. The practical limits on outlet geometry establish the
maximum outlet size, and the maximum outlet size establishes the lower
limit on continuous climb speed. Cooling design should not be a guessing
game.
> Thanks for any help.
> Mark
I wish I could be of more help to you. I strongly encourage you to look
into the actual techniques that the engine manufacturers use when doing
their cooling calculations. Again, they don't guess at it. One typical
discussion can be found on pages 206-214 of Barnes McCormick's text,
'Aerodynamics, Aeronautics, and Flight Mechanics' (at least in my
edition, it can). Lycoming has an in-house manual that is quite similar
and may be available which they use in conjunction with the technical
specifications for each specific engine, and Stan Miley has published
his method (also similar) in research papers that he did while
researching Piper cooling systems at Raspet in the early to mid-70's.
Any or all of these would be superb references.
Message 4
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| Subject: | Re: Run-in and Break-in |
--> Engines-List message posted by: Scott Bilinski <bilinski@kyocera-wireless.com>
Radiators mounted close to the prop is bad news. Has something to do with
the prop pulses as it goes by making any type of air intake less efficient
the closer it gets to the prop. An example of a really bad design is the
big oil cooler intake right behind the prop on a P-40.
At 11:37 AM 6/30/03 -0400, you wrote:
>--> Engines-List message posted by: Grant Corriveau <grantc@ca.inter.net>
>
>Jim,
>
>I find your calculations relevant to a mod I've been contemplating for my
>Zodiac with a 100HP CAM100 (Honda Conversion)...
>
>I currently have the rad on the nose/chin -- works okay, but I have some
>issues about heat into the engine room, vibrations on the radiator itself as
>it is mounted on the engine PSRU directly, drag....
>
>I have toyed with the idea (ala some famous WWII aircraft most notably the
>Spitfire), that moved the rad into the wing. My Zodiac has a fat wing where
>I could easily accomdate 1 or 2 radiators.... but I had no idea of the
>amount of airflow I would have to provide.
>
>Your numbers at least give me some ballpark figures. Any chance you could
>supply the formula that you are using?
>
>--
>Grant Corriveau
>C-GHTF / HDS / CAM100
>
>> As an aside, and as a rough visual comparison, an airplane producing 100
>> hp with 54 sq.in. of inlet area has to fly at least 99 mph at a pressure
>> altitude of 2000 ft in order to cool adequately at +40 dISA. Fifty-four
>> sq.in. at that speed is a flow rate of 3267 cfm and even so, the CHT's
>> will be right at the upper limit. The required outlet area for that
>> condition would probably be on the very loose order of 204 sq.in, but I
>> didn't stop to look at the actual number.
>>
>> I'm sorry I couldn't be of more help or provide more encouragement.
>>
>> All the best,
>> Jim Cunningham
>> Cunningham Engineering Associates
>
>
Message 5
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| Subject: | Re: Run-in and Break-in |
--> Engines-List message posted by: "James R. Cunningham" <jrccea@bellsouth.net>
Grant, it isn't a single formula; it is a series of formulae. And, it is
for aircooled engines, specifically Lycoming. Someone else on the list
talked a bit about liquid cooled engines, and I was much impressed with
what he said.... Was it Gary? I've deleted the messages and don't
remember off the top of my head.
I've given three references for procedures quite similar to the one I
use in my post just previous to this, in response to Mark.
Good luck with your project and all the best,
Jim
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