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Perfect cooling diffuser

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gcrowder2

Joined: 09 Jan 2006
Posts: 136
Location: Golden, Colorado USA

Posted: Fri Dec 01, 2006 2:28 pm Post subject: Perfect cooling diffuser

I created an almost exact copy of the Kuchemann/Weber perfect

diffuser on my Europa to try and keep my 135 hp EA81 cool.

All cooling on the EA81 is thru the water jacket and none is done by air

cooling on the 912/914 so the ducting has to be good.

  Both cooling in the air and ground are very good.  I can run the

engine as long as desired at 1800 rpm on the ground without over

heating even on a 100 F day.  In the air, water temps to go 200 F

after a 2 minute climbout then drop back to 185 for cruise.

  There is a 12" long diffuser section that expands like a bell to

slow and pressurize the incoming air.  After the rad, there is a

converging duct that accelerates the hot air back to free stream.

  There also is  a pull up cowl flap inside the converging section

that allows most of the incoming air to be shut off under cruise

conditions, adding 10 mph by cutting the flow and associated

drag when its not needed.  Works great!



                                      Glenn



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Gilles.Thesee(at)ac-greno
Guest

Posted: Fri Dec 01, 2006 3:18 pm Post subject: Perfect cooling diffuser

Glenn,



 	  Quote: 	
		  

  There is a 12" long diffuser section that expands like a bell to

 slow and pressurize the incoming air.  After the rad, there is a

 converging duct that accelerates the hot air back to free stream.

  There also is  a pull up cowl flap inside the converging section

 that allows most of the incoming air to be shut off under cruise

 conditions, adding 10 mph by cutting the flow and associated

 drag when its not needed.

This is the way to go.
	


Nice work designing and constructing your cooling duct and cowl flap. 

Küchemann is indeed a excellent basis to start from.

We had long discussions with Michel Colomban, of Cri-Cri and Ban Bi 

fame, who also used calculated sections similar to Küchemann's 

theoretical curves.

Since I had the opportunity to build a small wind-tunnel, I chose to use 

the stream-line approach (also in Küchemann's book), to exactly match 

our radiator block characteristics.

The results showed that a shorter -hence less lossy- diffuser was 

adequate in our case.

We also had to manage cylinder cooling air and intercooler duct.



Your cowling looks very sexy.

Congratulations,



Gilles Thesee

Grenoble, France

http://contrails.free.fr

grahamsingleton(at)btinte
Guest

Posted: Fri Dec 01, 2006 3:25 pm Post subject: Perfect cooling diffuser

Glenn

Which Subaru conversion did you use, the weak link often seems to be the 

reduction drive.

Graham



GLENN CROWDER wrote:



 	  Quote: 	
		   I created an almost exact copy of the Kuchemann/Weber perfect

 diffuser on my Europa to try and keep my 135 hp EA81 cool.

 All cooling on the EA81 is thru the water jacket and none is done by air

 cooling on the 912/914 so the ducting has to be good.

 Both cooling in the air and ground are very good. I can run the

 engine as long as desired at 1800 rpm on the ground without over

 heating even on a 100 F day. In the air, water temps to go 200 F

 after a 2 minute climbout then drop back to 185 for cruise.

 There is a 12" long diffuser section that expands like a bell to

 slow and pressurize the incoming air. After the rad, there is a

 converging duct that accelerates the hot air back to free stream.

 There also is a pull up cowl flap inside the converging section

 that allows most of the incoming air to be shut off under cruise

 conditions, adding 10 mph by cutting the flow and associated

 drag when its not needed. Works great!



 Glenn



 _________________________________________________________________

 View Athlete’s Collections with Live Search 

 http://sportmaps.live.com/index.html?source=hmemailtaglinenov06&FORM=MGAC01 

 ------------------------------------------------------------------------

 ------------------------------------------------------------------------

gcrowder2

Joined: 09 Jan 2006
Posts: 136
Location: Golden, Colorado USA

Posted: Fri Dec 01, 2006 8:33 pm Post subject: Perfect cooling diffuser

Hi Graham!

  I used the Marcotte M150 drive made in Canada.  Its been very good so far.

http://www.geocities.com/rayfiset/psru.html

  More info here:

http://www.sdsefi.com/air14.html

  The engine was built by Ram Performance Subaru in Dayton Ohio

http://www.ramengines.com

  He has a new 200 hp Supercharged EA81 with Rotrex supercharger on his site 

now.

I don't know of any unhappy users at this time!



                                   Glenn



 	  Quote: 	
		  From: Graham Singleton <grahamsingleton(at)btinternet.com>

Reply-To: europa-list(at)matronics.com

To: europa-list(at)matronics.com

Subject: Re: Perfect cooling diffuser

Date: Fri, 01 Dec 2006 23:29:01 +0000




<grahamsingleton(at)btinternet.com>



Glenn

Which Subaru conversion did you use, the weak link often seems to be the 

reduction drive.

Graham



GLENN CROWDER wrote:



>I created an almost exact copy of the Kuchemann/Weber perfect

>diffuser on my Europa to try and keep my 135 hp EA81 cool.

>All cooling on the EA81 is thru the water jacket and none is done by air

>cooling on the 912/914 so the ducting has to be good.

>Both cooling in the air and ground are very good. I can run the

>engine as long as desired at 1800 rpm on the ground without over

>heating even on a 100 F day. In the air, water temps to go 200 F

>after a 2 minute climbout then drop back to 185 for cruise.

>There is a 12" long diffuser section that expands like a bell to

>slow and pressurize the incoming air. After the rad, there is a

>converging duct that accelerates the hot air back to free stream.

>There also is a pull up cowl flap inside the converging section

>that allows most of the incoming air to be shut off under cruise

>conditions, adding 10 mph by cutting the flow and associated

>drag when its not needed. Works great!

>

>Glenn

>

>_________________________________________________________________

>View Athlete’s Collections with Live Search 

>http://sportmaps.live.com/index.html?source=hmemailtaglinenov06&FORM=MGAC01

>------------------------------------------------------------------------

>------------------------------------------------------------------------

>






	


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ami(at)mcfadyean.freeserv
Guest

Posted: Sat Dec 02, 2006 12:25 am Post subject: Perfect cooling diffuser

Glen,

What is your ratio(s) of inlet area to outlet area?

I realise that it is adjustable.



Duncan Mcf.

---

Gilles.Thesee(at)ac-greno
Guest

Posted: Sat Dec 02, 2006 5:20 am Post subject: Perfect cooling diffuser

Duncan,



 	  Quote: 	
		  

 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 

cm²). 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 5°C 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

m.clews(at)sky.com
Guest

Posted: Sat Dec 02, 2006 7:02 am Post subject: Perfect cooling diffuser

We have a 914 and usually use a blanking plate over the oil radiator, about 

1/4 blanked off in the summer and 3/4 blanked off in the winter.

This works well but a varible flap would be better, what designs do you guys 

use and are any approved by the PFA ?

Mike Clews

G-OMIK

---

gcrowder2

Joined: 09 Jan 2006
Posts: 136
Location: Golden, Colorado USA

Posted: Sat Dec 02, 2006 10:03 am Post subject: Perfect cooling diffuser

Hi Duncan!

  The rad face area is 9x12" so 108 sq in.  Inlet area is 34 sq in so ratio 

.31.  Outlet area is

4 x 12" so 48 sq in so ratio .44.

  The idea behind the bell shape is as the air enters the duct and begins to 

slow down,

it can follow a tighter radius without separating.  When the air enters the 

rad, it is

straightened again and then accelerated back to free stream in the 

converging duct.

  I think I still have some excess cooling capacity so I think this rad/duct 

combo is probably

good for 150 hp.  The guy in San Diego building the 200 hp supercharged

Europa is pretty much copying my cooling system so it will be interesting!  

I have a 2

row dual pass aluminum rad on my setup.  I suggested going to a 3 row dual 

pass brass for his

supercharged setup.



                                               Glenn



[quote]From: "Duncan & Ami McFadyean" <ami(at)mcfadyean.freeserve.co.uk>

Reply-To: europa-list(at)matronics.com

To: <europa-list(at)matronics.com>

Subject: Re: Perfect cooling diffuser

Date: Sat, 2 Dec 2006 08:22:55 -0000




<ami(at)mcfadyean.freeserve.co.uk>



Glen,

What is your ratio(s) of inlet area to outlet area?

I realise that it is adjustable.



Duncan Mcf.

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karelvranken(at)hotmail.c
Guest

Posted: Sat Dec 02, 2006 2:48 pm Post subject: Perfect cooling diffuser

Gilles,

This is the forum that I like most.

Average of the Europa builders have Rotax engines and the radiator (234 cm2) 

and ugly cowling (underside) are part of the kit. Those who personalise 

their build with other engines or modifications look forward to problems for 

eligibility in the different countries in Europe. So as Remy Guerner once 

said: I present my airplane for control without cowlings. But to the point 

now: Your radiator is 410 cm2 and Glenn has 685 cm2. I am convinced that 

your investigation and theoretical statement is correct. Why don't dare we 

tell that the original radiator for EUPA is undermeasured and the cowling 

design is a misfit for all those who are building following the manual? 

Shall I tell you that in France the G.D.A.C. don't approve the build in of 

the digitrak wingleveler because the kit is not that one who was eligible 

for their administration! I was surprised to see Glenns photographs because 

they show nearly what I realised and therefore encourage me to continue as 

well as your technical support. But as I said already: I didn't invent the 

wheel, unfortunately, and what I am doing at the moment is not finished and 

tested enough, so when my cowl flap will be nearly perfect I will give you 

more feadback of the results.

Karel Vranken,  F-PKRL # 447 XS Monowheel Rotax 912ULS Airmaster CSU

---

ami(at)mcfadyean.freeserv
Guest

Posted: Sun Dec 03, 2006 2:45 am Post subject: 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.



---

karelvranken(at)hotmail.c
Guest

Posted: Sun Dec 03, 2006 1:11 pm Post subject: Perfect cooling diffuser

Gilles, Glenn and all,

Here some pictures of my cowl modification; indeed inspired by Mustang P 51.

Karel Vranken.

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gcrowder2

Joined: 09 Jan 2006
Posts: 136
Location: Golden, Colorado USA

Posted: Sun Dec 03, 2006 5:50 pm Post subject: 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



[quote]From: "karelvranken" <karelvranken(at)hotmail.com>

Reply-To: europa-list(at)matronics.com

To: <europa-list(at)matronics.com>

Subject: Re: 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.

---

karelvranken(at)hotmail.c
Guest

Posted: Mon Dec 04, 2006 1:16 pm Post subject: Perfect cooling diffuser

Glenn,

The duct inside isn't part of the cowling. I made it of carbon tissu, it 

looks like a black hole, but be sure it is perfectly sealed on the radiator. 

The radiator also is modified, no more the square block but a 4 cm thick one 

of 26 cm x 15 cm = 390 cm2.

Karel Vranken.

---

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