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Jab cooling

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TELEDYNMCS(at)aol.com
Guest

Posted: Mon Oct 01, 2007 5:36 am Post subject: Jab cooling

In a message dated 10/1/2007 2:58:40 AM Eastern Daylight Time,  europa-list(at)matronics.com writes:

  	  Quote: 	
		  Concerning the Jabiru, there is little room    between the prop and the 

front cylinders to provide a correct diffuser, so    the inlet must be of 

larger size, and the efficiency will be lower.

But    the engine can be adequately cooled all the same, at the price of a 

little    more drag, of course. 	
  

 Hi Gilles and all,

  

 I've had a chance to test my turbulators installed at the mouth of my left  cooling intake and they worked exceedingly well. I've seen, on average, a  25F drop in CHT's on the left side now that I have turbulated the airflow  entering the left side intake. One cylinder dropped 45F and went from being  the second hottest of the six to the coolest. Interestingly, the  engine is now running in the 240F-260F range on all CHT's, but the delta  pressure did not change! This has left me with the impression that  all this talk about 6" of water column being needed for adequate cooling is a  bunch of bullshit put forth by the engine manufacturers to make you go away and  be quiet.

  

 I still have 3" WC on the right at cruise and the hottest CHT is about  250F. The coolest CHT on the right is 219F in cruise. I still have 5" of WC at  cruise on the left side and the highest CHT is now about 260F, down from  295F on the hottest cylinder in cruise. The coolest on the left is now 235F,  down from 275F prior to the turbulators.  All of my testing  results indicate that pressure is the absence of flow, not a  sign of flow. Internal cooling duct pressure, measured against static pressure  inside the cowl, seems to be have an inverse relationship to flow, if  indeed it has any relationship at all. My test results show pressure is  meaningless and FLOW is what we're after.

 

I think ultimately what I'm going to do here is dimple the area around  my intake ducts like a golf ball. The zigzag tape is ugly and I can't think  of a way to make it pretty, so I think dimples are the answer. Should make for  quite a conversation piece, don't you think?

  

 Clearly, Andy Silvester used the Lancair cowls as a model for his Europa  cowl set. I've studied close up pictures of the Lancair cowl to try and  find out what the difference between the two really is. The only thing I  notice is the Lancair inlets protrude about 1" farther in front of the  cowl than mine do.,  I think this has something to do with the pressure  wave I've observed in front of my left intake with my crude string tests. So  Gilles, you are likley correct in your analysis.

  

 FWIW, every Sonex cooling suggestion I've tried has lead to hotter,  not cooler temps. So, Jabiropaphiles, my suggestion is don't bother with  anything Sonex has to say. 

  

 The moral of this story is: for better FLOW, excite the  area just outside the hole. Almost pornographic, isn't it? (notice how I didn't  say for better PRESSURE?)

  

 Now, I'm back to analysis of boundary flow on the  wings.......



Regards,

  

 John Lawton

 Whitwell, TN (TN89)

N245E - Flying 

 

  



See what's new="_blank">Make AOL Your Homepage.

  [quote][b]

astills

Joined: 24 Apr 2007
Posts: 6
Location: Phoenix,Ariz

Posted: Mon Oct 01, 2007 6:19 am Post subject: Jab cooling

John,  

Do you think you could take p picture and attach it so we could see the tape on the front of the cowls.   

Al Stills  

N625Az  

       

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of TELEDYNMCS(at)aol.com

 Sent: Monday, October 01, 2007 6:30 AM

 To: europa-list(at)matronics.com

 Subject: Jab cooling  

  

  

     

In a message dated 10/1/2007 2:58:40 AM Eastern Daylight Time, europa-list(at)matronics.com writes:  

   	  Quote: 	
		    

Concerning the Jabiru, there is little room between the prop and the 

 [i]front cylinders to provide a correct diffuser, so the inlet must be of 

 larger size, and the efficiency will be lower.

 But the engine can be adequately cooled all the same, at the price of a 

 little more drag, of course[/i].  	
    

   

    

Hi Gilles and all,  

    

   

    

I've had a chance to test my turbulators installed at the mouth of my left cooling intake and they worked exceedingly well. I've seen, on average, a 25F drop in CHT's on the left side now that I have turbulated the airflow entering the left side intake. One cylinder dropped 45F and went from being the second hottest of the six to the coolest. Interestingly, the engine is now running in the 240F-260F range on all CHT's, but the delta pressure did not change! This has left me with the impression that all this talk about 6" of water column being needed for adequate cooling is a bunch of bullshit put forth by the engine manufacturers to make you go away and be quiet.  

    

   

    

I still have 3" WC on the right at cruise and the hottest CHT is about 250F. The coolest CHT on the right is 219F in cruise. I still have 5" of WC at cruise on the left side and the highest CHT is now about 260F, down from 295F on the hottest cylinder in cruise. The coolest on the left is now 235F, down from 275F prior to the turbulators.  All of my testing results indicate that pressure is the absence of flow, not a sign of flow. Internal cooling duct pressure, measured against static pressure inside the cowl, seems to be have an inverse relationship to flow, if indeed it has any relationship at all. My test results show pressure is meaningless and FLOW is what we're after.  

    



 I think ultimately what I'm going to do here is dimple the area around my intake ducts like a golf ball. The zigzag tape is ugly and I can't think of a way to make it pretty, so I think dimples are the answer. Should make for quite a conversation piece, don't you think?  

    

   

    

Clearly, Andy Silvester used the Lancair cowls as a model for his Europa cowl set. I've studied close up pictures of the Lancair cowl to try and find out what the difference between the two really is. The only thing I notice is the Lancair inlets protrude about 1" farther in front of the cowl than mine do.,  I think this has something to do with the pressure wave I've observed in front of my left intake with my crude string tests. So Gilles, you are likley correct in your analysis.  

    

   

    

FWIW, every Sonex cooling suggestion I've tried has lead to hotter, not cooler temps. So, Jabiropaphiles, my suggestion is don't bother with anything Sonex has to say.   

    

   

    

The moral of this story is: for better FLOW, excite the area just outside the hole. Almost pornographic, isn't it? (notice how I didn't say for better PRESSURE?)  

    

   

    

Now, I'm back to analysis of boundary flow on the wings.......

 

 Regards,  

    

   

    

John Lawton  

    

Whitwell, TN (TN89)

 N245E - Flying   

    

   

  



 

         

  

See what's new="_blank">Make AOL Your Homepage.  

   	  Quote: 	
		    http://www.matronics.com/Navigator?Europa-List 	
0 	  Quote: 	
		   	
1 	  Quote: 	
		   	
2 	  Quote: 	
		   	
3 	  Quote: 	
		   	
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        [quote][b]

brian.lonnon(at)tiscali.c
Guest

Posted: Mon Oct 01, 2007 8:02 am Post subject: Jab cooling

Hi John,

  

 Could you provide a picture of your turbulator please?

  

 Thanks

  

 Brian

  

 G-BYFG

  

 XS trigear, Jabiru 3300

 [quote]   ---

gdh(at)isp.com
Guest

Posted: Mon Oct 01, 2007 8:25 am Post subject: Jab cooling

Hi John,

 I want to add to Al Stills request of showing us how you made and installed  the turbulators.  Sounds like an interesting approach to my cooling  problems.  I did put an "eyebrow" on the left air intake but it didn't seem  to make much difference.

 Thank you.

 Dale Hetrick

 [quote]   ---

fklein(at)orcasonline.com
Guest

Posted: Mon Oct 01, 2007 10:09 am Post subject: Jab cooling

 	  Quote: 	
		   In a message dated 10/1/2007 2:58:40 AM Eastern Daylight Time, 

 europa-list(at)matronics.com writes:



 Concerning the Jabiru, there is little room between the prop and the

 front cylinders to provide a correct diffuser, so the inlet must be of

 larger size, and the efficiency will be lower.

 But the engine can be adequately cooled all the same, at the price of a

 little more drag, of course.


	


On Monday, October 1, 2007, at 06:30  AM, TELEDYNMCS(at)aol.com wrote:

 	  Quote: 	
		    

 I've had a chance to test my turbulators installed at the mouth of my 

 left cooling intake and they worked exceedingly well. I've seen, on 

 average, a 25F drop in CHT's on the left side now that I have 

 turbulated the airflow entering the left side intake. One cylinder 

 dropped 45F and went from being the second hottest of the six to the 

 coolest. Interestingly, the engine is now running in the 240F-260F 

 range on all CHT's, but the delta pressure did not change!


	


 	  Quote: 	
		   Clearly, Andy Silvester used the Lancair cowls as a model for his 

 Europa cowl set. I've studied close up pictures of the Lancair cowl to 

 try and find out what the difference between the two really is. The 

 only thing I notice is the Lancair inlets protrude about 1" farther in 

 front of the cowl than mine do.,  I think this has something to do 

 with the pressure wave I've observed in front of my left intake with 

 my crude string tests. So Gilles, you are likley correct in your 

 analysis.


	


As a (at this point at least) probable Jab buyer, I've been following 

this thread w/ interest. Up til now, I had assumed that the difference 

between right and left side cooling issues was a consequence of the 

difference in prop wash. I've also assumed that references to "right" 

and "left" were to starboard and port, i.e., as seen from the cockpit 

rather than say from the front of the engine looking aft. I believe 

that the protrusions around the circumference of the Lancair cowl 

inlets are intended to minimize the effects of prop wash on air 

entering the inlets. Also, from the pictures I've seen of the 

Suncoast/Jab air ducting, it appears that the port and starboard ducts 

have identical (but opposite hand) shapes which do not appear to factor 

in the front to rear offsets of the port/starboard cylinder banks.



It just now occurs to me (after reviewing Giles's Contrails articles 

referenced previously) that the difference in distance between the 

inlets and the first cylinders seen by air entering the port and 

starboard ducts may be of equal or even greater importance...and may be 

the source of the differential in port/starboard cooling effectiveness.



This is conjecture on my part, and of course no substitute for the 

rigorous testing John L. has done; still, it might be nice to get to 

the heart of the problem. Please comment at will!



Incidentally Giles, 2 of the 3 articles you referenced come up in 

french; could you offer any clues as to how I could view them in 

english?



Fred

A194

-- 

This message has been scanned for viruses and

dangerous content by MailScanner, and is

believed to be clean.

Gilles.Thesee(at)ac-greno
Guest

Posted: Mon Oct 01, 2007 11:52 am Post subject: Jab cooling

Fred Klein a écrit :

 	  Quote: 	
		   Incidentally Giles, 2 of the 3 articles you referenced come up in 

 french; could you offer any clues as to how I could view them in english?


	


Fred,



In the future all the articles will be in English. But it takes time for 

a non natural English speaker/writer.

Now if there is a massive demand about a specific page, I might put it 

on the front burner...



Best regards,

-- 

Gilles

http://contrails.free.fr

grahamsingleton(at)btinte
Guest

Posted: Mon Oct 01, 2007 1:05 pm Post subject: Jab cooling

Gilles

you are a gentleman. Your english is as good as mine! Wish my french was 

half as good {{

Graham

Gilles Thesee wrote:

 	  Quote: 	

 <Gilles.Thesee(at)ac-grenoble.fr>

 Fred Klein a écrit :

> Incidentally Giles, 2 of the 3 articles you referenced come up in 

> french; could you offer any clues as to how I could view them in english?

 Fred,

 In the future all the articles will be in English. But it takes time for 

 a non natural English speaker/writer.

 Now if there is a massive demand about a specific page, I might put it 

 on the front burner...

 Best regards,

-- 

Graham Singleton

Tel: +441629820187

Mob: +447739582005

aireupora(at)sbcglobal.ne
Guest

Posted: Mon Oct 01, 2007 6:20 pm Post subject: Jab cooling

[quote][b]

grahamsingleton(at)btinte
Guest

Posted: Tue Oct 02, 2007 1:43 am Post subject: Jab cooling

John

thanks for your fascinating test results. I too am very puzzled by the 

apparent lack of effectiveness of Pressure. Air will only move from hi P 

to Low P, (apart from Coriolis effects of course, witness circulation 

round cyclones)

I wonder if your turbulator is helping keep the flow attached over the 

whole of the outside of the cowl? That might reduce the pressure around 

the outlet at the back and that is what is important as we all know but 

can't quite understand (how to make it better I mean)

In flight the flow over the cowl will be quite assymetric

Thoughts Gilles?

Graham



TELEDYNMCS(at)aol.com wrote:

 	  Quote: 	
		   In a message dated 10/1/2007 2:58:40 AM Eastern Daylight Time, 

 europa-list(at)matronics.com writes:

 

     /Concerning the Jabiru, there is little room between the prop and the

     front cylinders to provide a correct diffuser, so the inlet must be of

     larger size, and the efficiency will be lower.

     But the engine can be adequately cooled all the same, at the price of a

     little more drag, of course./

 

  

 Hi Gilles and all,

  

 I've had a chance to test my turbulators installed at the mouth of my 

 left cooling intake and they worked exceedingly well. I've seen, on 

 average, a 25F drop in CHT's on the left side now that I have turbulated 

 the airflow entering the left side intake.

  

 The moral of this story is: for better /FLOW/, excite the area just 

 outside the hole. Almost pornographic, isn't it? (notice how I didn't 

 say for better /PRESSURE/?)

  

 Now, I'm back to analysis of boundary flow on the wings.......

 

 Regards,

  

 John Lawton

 Whitwell, TN (TN89)

 N245E - Flying

Gilles.Thesee(at)ac-greno
Guest

Posted: Tue Oct 02, 2007 1:19 pm Post subject: Jab cooling

Graham Singleton a écrit :

 	  Quote: 	
		   Your english is as good as mine! Wish my french was half as good {{


	


Graham,



Blushing with embarrassment 

Thank you for your kind message.

I already updated the English version of the Cowling slideshows.



Any corrections concerning style, spelling, grammar, etc. are welcome.



Best regards,

-- 

Gilles

http://contrails.free.fr

Gilles.Thesee(at)ac-greno
Guest

Posted: Tue Oct 02, 2007 1:23 pm Post subject: Jab cooling

<grahamsingleton(at)btinternet.com>

 	  Quote: 	
		   I wonder if your turbulator is helping keep the flow attached over the 

 whole of the outside of the cowl? That might reduce the pressure 

 around the outlet at the back and that is what is important as we all 

 know but can't quite understand (how to make it better I mean)

 In flight the flow over the cowl will be quite assymetric

 Thoughts Gilles?


	


Graham, John and all,



A little busy at the moment, so I may have missed some detail on John's 

setup. I'm naturally much interested in any successful engine installation.

John, did you provide a link to your engine installation ? Sorry if I 

missed the obvious.



Please continue to give info,

Best regards,

-- 

Gilles

http://contrails.free.fr

m.j.gregory(at)talk21.com
Guest

Posted: Tue Oct 02, 2007 4:08 pm Post subject: Jab cooling

I recall that in 1995 I asked the late Richard Cabrinha why he had changed from a chin intake to a pair of Lo-Presti style circular intakes on his Free Spirit Mark II, for cooling a Continental IO 360, and he replied "because they work!"  He told me that if the diameter were too large then there would be a reverse flow, spilling air out round the circumference of each intake.  He refined the size by putting some oil around each rim and doing a quick circuit: inspection on landing showed whether the oil film had spread inwards or migrated outwards, and he would then the repeat the test with different diameters accordingly.  

   

For those on HTML, here is a picture of the final result:  

[img]cid:image002.jpg(at)01C80558.1A3745B0[/img]  

   

It may not have been the most scientific way of finding the right size, but he claimed that it worked.  I have no information on the distribution of air and temperature levels for the six cylinders.  He did however incorporate cowl flaps, one on each side at the rear of the cowling (the starboard one is visible in the picture), which he said he would like to eliminate in due course to simplify the design with a fixed outlet area.  

   

Best regards  

   

Mike  

   

--

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TELEDYNMCS(at)aol.com
Guest

Posted: Wed Oct 03, 2007 8:46 am Post subject: Jab cooling

In a message dated 10/3/2007 3:00:41 AM Eastern Daylight Time,  europa-list(at)matronics.com writes:

  	  Quote: 	
		  I    recall that in 1995 I asked the late Richard Cabrinha why he had    changed

from a chin intake to a pair of Lo-Presti style circular intakes on    his Free

Spirit Mark II, for cooling a Continental IO 360, and he replied    "because

they work!"  He told me that if the diameter were too large    then there would

be a reverse flow, spilling air out round the    circumference of each intake.

He refined the size by putting some oil    around each rim and doing a quick

circuit: inspection on landing showed    whether the oil film had spread

inwards or migrated outwards, and he would    then the repeat the test with

different diameters  accordingly. 	


 

  

  

 Hi Mike, Graham, and all,

  

 That is essentially what I've done with my string testing, although I  wasn't aware that size had much to do with it (Typical male, huh?) I've not  played with changing the size of the intake at all. It does seem like 25  square inches of intake should be more than adequate for cooling this little  engine, though.

 . 

 What I've seen in my string tests is an apparent low pressure area forming  on the outboard side of the left intake as viewed from the cockpit. I've also  noticed an apparent high pressure area directly in front of the inlet when my  turbulators are not installed and this high pressure "bubble" rejects the string  as it approaches the intake from upwind.  At one point it turns the string  180 degrees and it blows towards the fan. Installing turbulators at the lip of  the intake helped considerably. I went from about 50% of the intake  "accepting" the string, to what I'd estimate as about 80% now accepting the  string in the intake. Still not perfect, but I'm still playing with it, too.  What I have seen in terms of engine cooling has been dramatic, though.

  

 I need to dig up the Lo-Presti info and take a look at it. That's about the  fifth time somebody has mentioned that name to me.

 

An A&P friend of mine stopped by my shop yesterday and I showed him  what I was doing. He's also a glider pilot and amateur aerodynamicist. We  also discussed exit cooling flow. The trigear has a rather large triangle shaped  reinforcing piece on the nosegear leg just below and outside the line  of the cowl. This triangle is flat to the relative wind, probably worse at climb  angles, and I would reckon that it causes some disturbance right where the  cooling air from the cowl is trying to exit. Whether or not that is  interfering with my cooling flow remains to be determined, but it sure looks  like it could use a fairing to split the flow, hopefully accelerating it and  causing a low pressure area in that region. It stands to reason that cleaning up  this area with a fairing might help create a bit of suction and aid cooling  flow, too.

  

 Graham said: I wonder if your turbulator is helping keep the flow  attached over the 

whole of the outside of the cowl?

  

 I'm thinking you are correct in your assessment there, Graham. I think  "re-exciting" the flow is indeed causing it to stay attached. FWIW, I've  done some tuft testing on my wings and I seem to have laminar flow at least as  far back as the hinge line of the aileron. The wing tip is much cleaner than I  anticipated, too. There are very few modern sailplanes that get this level of  laminar flow that far back on the wing. Shaw and Dykins are obviously  genius'.

  

 I don't have enough knowledge on the subject to really know one way or the  other how internal duct pressure is related to flow, but my tests seem to  indicate that there is either no relationship, or the relationship is inverse.  If you think about it, restricting the flow would cause higher pressure,  just as it does when you put your finger on the end of a running garden hose.  The pressure increases, but the flow decreases. That seems to be what is  happening here.

  

 Regards,

  

 John  Lawton

Whitwell, TN (TN89)

N245E -  Flying



See what's n="_blank">Make AOL Your Homepage.

  [quote][b]

ami(at)mcfadyean.freeserv
Guest

Posted: Wed Oct 03, 2007 12:42 pm Post subject: Jab cooling

John,

 You could also try:

 "An investigation of the aerodynamics and cooling of horizontally opposed  engine installation" 

 SJ Miley. SAE 1977.

 Which contains velocity ratio investigations for a number of different  nostril shapes, including 'LoPresti' style.

  

 Duncan Mcf.

 [quote]   ---

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