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Cooling diffuser

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rparigor(at)suffolk.lib.n
Guest

Posted: Thu Nov 30, 2006 9:01 am Post subject: Cooling diffuser

Has anyone changed the cooling air intake location and shape (diffuser)

for a XS / Rotax install?



It seems that if the duct was slight shorter with a proper shaped lip,

something like the Katana Extreme photo attached, may be a better

mousetrap??



By having the entrance of the diffuser airfoil shaped, if done properly

with the flat side on the inside, it could decrease speed and increase

pressure which is exact what we want, and even give a bit of forward

thrust.



Also included a picture of Gilles diffuser.



Ron P.

Katana_Extreme.jpg

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kpaviat(at)verizon.net
Guest

Posted: Thu Nov 30, 2006 12:15 pm Post subject: Cooling diffuser

Hello Ron!

You are correct to assume the XS cowling cooling intake will not work

properly if just using the raw edges as-is after cutting the shape out of

the front of the cowling. It is important to smooth the incoming air. You

can call me directly for some detail about this (I just don't have the time

right now to publish a complete dissertation about the Southern California

experiments....)

Kp

909-437-5151

karelvranken(at)hotmail.c
Guest

Posted: Thu Nov 30, 2006 2:17 pm Post subject: Cooling diffuser

Hello Ron,

Yes I changed the cooling air intake and the shape of the cowling on my XS. 

At the moment the results are good. But we anyway need a controlable system 

for the changing conditions and temperatures. I am working on a dynamic 

balanced flap attached to the existing cooling duct aft of the oil radiator 

and fitting in the cowling. At the moment it's to early to show what I am 

doing because I need more tests and experience in flap control. Something 

for long winter evenings. But if the papermen find that this is a 

modification needing formulas and engineering reports than I put on the good 

old cowling as ugly as it is.

Karel Vranken,  F-PKRL # 447 XS Rotax 912 ULS, Airmaster CSU only 16 hours 

and waiting for the papermen's final certificate.

---

Gilles.Thesee(at)ac-greno
Guest

Posted: Thu Nov 30, 2006 3:20 pm Post subject: Cooling diffuser

Ron and all,



 	  Quote: 	
		   Also included a picture of Gilles diffuser.

   


	


For those interested, here is some info on the research I did on the 

cooling of the 914



In (hopefully understandable) English :

http://contrails.free.fr/engine_aerodyn_radia_en.php

http://contrails.free.fr/tunnel_en.php



Still in French for some time :

http://contrails.free.fr/engine_air_inlets.php

http://contrails.free.fr/engine_liquide_refroid.php



Some pictures of our cowling

http://contrails.free.fr/diap/phpslideshow.php?directory=diapo_capot_if



Hope this helps,



Regards,

Gilles

http://contrails.free.fr

grahamsingleton(at)btinte
Guest

Posted: Thu Nov 30, 2006 3:39 pm Post subject: Cooling diffuser

Gilles

It certainly does help. Have you had any discussions with Kim Prout? I 

would love to listen to a conference between you two and Kim's father Paul.

How often do things have to be invented more than once?

Graham



Gilles Thesee wrote:



 	  Quote: 	
		   For those interested, here is some info on the research I did on the 

 cooling of the 914



 In (hopefully understandable) English :



 Hope this helps,



 Regards,

 Gilles

 http://contrails.free.fr

hagargs(at)earthlink.net
Guest

Posted: Thu Nov 30, 2006 6:28 pm Post subject: Cooling diffuser

Ron:



I have changed the intake nostrils on  the cowl to the 914 and have had

very good luck with keeping it cool in the AZ heat.  The original round

configuration has the exhaust headers centered in the hole without much

view of the  cylinder fins.  I opened up each hole to the inboard side

about 1 inch having the radius decrease as it got closer to the inboard

side.  Now each nostril is egg shaped with a commanding view of each

cylinder fin bank.  Special pains were made to extend the  lip of the  new

portion of the  hole inside of the cowling to avoid having the  air spill

off of  the  inside edge and  become turbulent.  The length of the edge

toward the innermost side of each hole is about an inch deep.  It makes for

good airflow toward the  cylinder fins and presents a good appearance from

the outside.



Steve Hagar

A143

Mesa, AZ



20 hours of  flight testing



Steve Hagar

hagargs(at)earthlink.net

air.guerner(at)wanadoo.fr
Guest

Posted: Fri Dec 01, 2006 1:33 pm Post subject: Cooling diffuser

Bonjour Gilles,<?xml:namespace prefix = noxml /><?xml:namespace prefix = o /> 

Your web site is full of very interesting experiments and test results I always enjoy reading. 

Regarding engine cooling, it seems everybody agrees that the design of the cowling of the Europa XS is far from optimum and MCRs, especially yours, are a lot better regarding cooling drag and efficiency in flight . But I am just curious to know how it performs ON THE GROUND. Do you have any measurement available such as CHT vs time from a cold start, at a given OAT, with the engine running at high idle, in no wind condition? Do you get a CHT stabilization ?  

  

Remi Guerner 

Europa F-PGKL       [quote][b]

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri Dec 01, 2006 2:57 pm Post subject: Cooling diffuser

Salut Rémi,



 	  Quote: 	
		   But I am just curious to know how it performs ON THE GROUND. Do you 

 have any measurement available such as CHT vs time from a cold start, 

 at a given OAT, with the engine running at high idle, in no wind 

 condition? Do you get a CHT stabilization ?



  



Thanks for the kind words.
	


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 - 14°C to + 

37°C 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

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri Dec 01, 2006 3:27 pm Post subject: Cooling diffuser

Graham,

 	  Quote: 	
		  

 It certainly does help. Have you had any discussions with Kim Prout? I 

 would love to listen to a conference between you two and Kim's father 

 Paul.

 How often do things have to be invented more than once?


	


Thank you for your message.

I never discussed with Kim, but the research and discussions (lots of 

them) were most interesting. The knowledge on radiator cooling is at 

hand, all we have to do is share what we have learned.



Best regards,

Gilles

http://contrails.free.fr

air.guerner(at)wanadoo.fr
Guest

Posted: Sun Dec 03, 2006 4:24 am Post 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 <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />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. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> 

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

  [quote][b]

grahamsingleton(at)btinte
Guest

Posted: Sun Dec 03, 2006 5:04 pm Post subject: 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



Rémi Guerner wrote:



 	  Quote: 	
		  



 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  



*

*

rparigor(at)suffolk.lib.n
Guest

Posted: Sun Dec 03, 2006 9:44 pm Post subject: Cooling diffuser

Hello Graham



"> Another way to improve cooling on the ground is exhaust extraction,

this 

 	  Quote: 	
		   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

grahamsingleton(at)btinte
Guest

Posted: Mon Dec 04, 2006 3:22 am Post subject: Cooling diffuser

Ron

I will attach a pik. Problem with Europas is the gases can get sucked 

into the cabin, but that could be cured I'm sure.

Graham

rparigor(at)suffolk.lib.ny.us wrote:

 	  Quote: 	
		  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?

Ron Parigoris

exhaust_extraction_Steve_VolE.jpg

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robh(at)hyperion-ef.us
Guest

Posted: Mon Dec 04, 2006 7:49 am Post subject: Cooling diffuser

In re: water spray



It's been a long time since I studied heat transfer but I recall enough of

the principles (if  not the details) to know that there are a couple of

conflicting factors with this proposal.  On the plus side, a fine mist of

water  will provide some evaporative cooling, since the phase change from

liquid to gas will remove much more heat than liquid water flowing through

the air spaces in the "radiator" (a heat exchanger in engineering speak).

Also on the plus side is the fact that heat transfer to water is more

efficient than heat transfer to air.  So far, so good.  The big negative

here is the impediment to air flow - put any amount of water in the spaces

where the air is supposed to flow and less air can flow resulting in less

efficient cooling.  It's worth a try but I expect that spraying water will

cause coolant temperature to rise not fall.

Best regards,



Rob Housman

A070

Airframe complete

Irvine, CA



--

nwcmc(at)tiscali.co.uk
Guest

Posted: Tue Dec 05, 2006 5:55 am Post subject: Cooling diffuser

 	  Quote: 	
		  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. <  

   
	


I think Remi’s idea of using the cooler flap to increase cooling on the ground and reduce it in the air is great. However, although I have a Rotax 912S with Airmaster prop, I do not get significant cooling problems on the ground even when the OAT is up to 30degC. Cooling and cowl design seems to be one of those areas where even with identical setups we all get different results. One thing that is certain with the Rotax is that it has a tendency to get hot when the initial flight testing is done in the summer months. I found that the engine took about 25 hours to run-in fully, after which the oil and coolant temperatures dropped significantly.  

   

Nigel Charles  [quote] [b]

Gilles.Thesee(at)ac-greno
Guest

Posted: Thu Dec 07, 2006 12:59 pm Post subject: Cooling diffuser

Salut Rémi and all,



Been much too busy those past few days.

Slowly catching up on the cooling conversation. Many valuable inputs indeed.



 	  Quote: 	
		   ... 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.




	


True. Now this is much less of an issue when the inlet is located far 

from the propeller center line,at the bottom of the cowl, for instance.



 	  Quote: 	
		   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.




	


I wanted to be sure to build up as much static pressure in the intake to 

cool efficiently, and still have enough pressure left after crossing the 

radiator, to exit at as high a velocity as practical. The goal was to 

cool and still achieve lower drag.



Regards,

Gilles

http://contrails.free.fr

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