X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ms-smtp-04.southeast.rr.com ([24.25.9.103] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2202270 for flyrotary@lancaironline.net; Fri, 27 Jul 2007 09:05:38 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-103-061.carolina.res.rr.com [24.74.103.61]) by ms-smtp-04.southeast.rr.com (8.13.6/8.13.6) with SMTP id l6RD4kCS009291 for ; Fri, 27 Jul 2007 09:04:47 -0400 (EDT) Message-ID: <003201c7d04e$babfb1a0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Oil cooler inlet - what next? Date: Fri, 27 Jul 2007 09:04:55 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002F_01C7D02D.335F5560" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_002F_01C7D02D.335F5560 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Dennis, An imprecise term, but basically any core has a maximum amount of heat = it can effectively transfer from liquid to air, otherwise, we would all = use a tiny radiator and oil cooler. I would normally not try to = determine if that condition has been reached by using a core that is = assured to transferring the required BTUs from the cooler for a = specified air flow. Theoretically, you could set up a test rig so that you could pump hot = oil at a specified temperature through a core. Have sufficient airflow = (big blower?) to stabilize the oil temp at your max acceptable limit. = Then increase the oil flow/or temperature of the oil into the core as = well as the air flow to try to keep the temp at your limit. At some = point, increasing air flow will fail to keep the temperature from = climbing because the core has reached the point where it is incapable = of transferring any significant increase in heat to the air flow. I only mention it to Al, because my poor memory can not recall the size = of his oil cooler. Al, has refreshed it with the size and its plenty = big enough for his needs. So the problem appears to be air flow. Ed ----- Original Message -----=20 From: Dennis Haverlah=20 To: Rotary motors in aircraft=20 Sent: Thursday, July 26, 2007 10:11 PM Subject: [FlyRotary] Re: Oil cooler inlet - what next? Ed, How can a person determine if the oil cooler is "saturated"? =20 Thanks, Dennis H. Ed Anderson wrote: Sorry to hear your efforts produced no noticeable improvement, Al. I do have a question - what is the core volume of your oil cooler? = A stock 2 rotor color has a core area of approx 19x4/12x2 =3D 171 Cubic = Inches. That will cool a two rotor at 160 mph producing 160 Hp with an = oil BTU heat factor of 2688 BTU/min. A 3 rotor producing 1/3 more HP = (213 HP) rpm would create a corresponding rise in BTU/min to 3360. Is your core big enough to dissipate that much increase? Sorry, = I just can't remember what size oil cooler you have. =20 The reason I ask, is that if forcing more air through the core does = not decrease the oil temp - could there exist the possibility that the = core is saturated and can is simply not capable of transferring more oil = heat to the air? If that were the case, then, as you know, no amount = of additional air through the core would make any significant = difference. Ed --- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Thursday, July 26, 2007 7:06 PM Subject: [FlyRotary] Re: Oil cooler inlet - what next? Installed sheet metal 'baffle' to form new upper wall of the = diffuser as shown in the photo. The idea was to assist in maintaining = attached flow, and to block leakage through the gap at the top. The = baffle was done in 3 pieces in order to insert past the divider/supports = in the scoop; each piece is about 7 =BD" wide. There are gaps between = pieces of about 3/8 - =BD" inch. The inlet pressure probe was placed at = point "D". Test flight showed no noticeable difference in delta T on the oil. = The pressure measured at "D" was 3" H2O. Pressure behind the exit = fairing was again -3/4". The pressures at C and D (measured at = different times) are at about 6" from the inboard end of the 22" long = cooler. There may be some variation axially. Because of the gaps in = the baffle, and fitting around the end tanks, there is still some air = bypassing the cooler; but I don't know how significant. Given the 9+" = H2O dynamic pressure out in front of the scoop still indicates not good = pressure recovery. Nonetheless; it is certainly disappointing that there was no = change (within the accuracy of the temp measurements) in the effective = cooling. This suggests that the wall shape and the air leakage are not = the problem. Calculating back from the temp changes in oil and air suggest = there is only about 1000 cfm going through the cooler core. The = extrapolation of my measured data on air flow vs pressure drop across = the core suggests that at 3" H2O there should be about 2000 cfm through = the core. Because of the centrifugal blower I was using for flow tests = I was only able to get data up to about 0.6" H2O and 700 cfm. I fit the = data to Y=3Dax+bx2 using regression analysis, which gave a very good fit = up to that point; but extrapolating out to 3" may be stretching it. If = I assume the pressure drop goes as the cube of the flow velocity, the = extrapolation is considerable different - about 1330 cfm at 3" H2O. Al -----Original Message----- From: Rotary motors in aircraft = [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen Sent: Friday, July 20, 2007 10:42 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Oil cooler inlet Well; I may end up with VGs and change in upper duct wall shape. = My intention yesterday was to install VGs as a first step, test fly, = measure pressure and temps; then proceed with installing sheet metal = upper duct wall change. In deciding where to put the VGs, I looked at things with the gear = up (Photo 1). The gear door has a bump, and there is some gap around = the door. Don't know what all this does to BL. Ended up putting VG = toward the left side about 26" in font of scoop, and toward the right = side right on the gear door bump. I then spent a bunch of time trying to get the pressure measuring = tube situated. The only access is through the scoop opening, and I = can't get my hands in there; so it is very tough. Plus the tube going = in there, or along the surface in front will affect the flow behavior, = so what affect are we going to measure. Having multiple measurements = would be great; but very difficult to achieve. While doing that, I spent some time looking in there with a small = mirror. What I noted was that initial gaps above and below the cooler = (required to slide the unit in and out) had changed a bit. The cooler = is supported on pads of 'Cool-Mat' insulation. Those have compressed = just a little, so now there is very little gap at the bottom, and 1/8"+ = along the top. That is a fairly substantial leak, and the loss of = pressure at the top likely exacerbates the flow separation. I decided = it wasn't worth going to test the VGs as long as that leakage gap was = there. Taking the wing off (mostly getting it back on because of next to = impossible access to nuts), and removing the cooler looks a bit much = right now. I realized then; that by putting in a sheet metal 'false' = upper duct wall, I could extend it up into the gap at the top (photo 2), = thereby changing the shape, and (mostly) closing the gap at the top. The false wall has to be in three parts for the three openings, = and there will be gaps between because of the supporting dividers; but = it could make a substantial difference. I made the piece for the = center, and considered testing just that; but the upper gap concerns me = enough that I think I'll try to get all three fit in. Then go take a flight test. Unfortunately this combines three = changes, VGs, closing gap, and changing duct wall. I had hoped to test = these one at a time. If there is a substantial change; it will be easy = to remove the VGs to see what that effect was. Of course I'll let you know when I get some results. Oh, the price of innovationJ. Al -----Original Message----- From: Rotary motors in aircraft = [mailto:flyrotary@lancaironline.net] On Behalf Of Thomas Jakits Sent: Thursday, July 19, 2007 10:31 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Oil cooler inlet Okay, Monty thinks the emphasis is on the BL. I believe (don't know), the main-problem is the upper ductwall = shape. Even if you have perfect BL flow, the upper wall shape is still = not good and will stall the flow.=20 At the end of the game you want good flow at all speeds and be = able to close any ducts to limit excess cooling (when you hopefully get = there). Obviously BL will play a role in your installation as the intake = is rather narrow. However BL or not - BL does not mean there is no flow, just slower = and more turbulent, but still generally going towards the cooler. Aerodynamics in the duct should be much the same for laminar, = turbulent, any flow, as long as there is flow. When things stall is when flow pretty much ceases (in the stalled = area ....), no matter how well things where at the entrance. The stall in this case is rather "easy" to get, as the speed seems = rather low already. Still may be good enough if you can do away with the = stall. So I suggest to work on the duct wall first and optimize it. As suggested, with some kind of sheet, alu, fiberglass, etc. You = can curve it more and more until you peak. Maybe pinched ducts (copyright Ed!!) are not working here, but it = may as well - if they work a Ed's theory explains (energizes the = flow...) If this works, modify according to the best shape found. Then try to improve with VGs or sanding or turbolator tape. Then go for the exit - after all it is a differential pressure = game.... TJ =20 On 7/18/07, M Roberts wrote:=20 Al, I think you need to do something to energize the boundary layer. = If you can't divert it you need to put some energy into it. It is = probably getting slow and separating from the face of the duct. That is = what your data seems to indicate to me.=20 I like the shape that Thomas proposes better than what you have = now, however, I still think you will need some VG's in front of the = inlet.=20 I know it may seem counter intuitive, but turbulence may actually = help in this case. You will not get very efficient internal diffusion, = but it will be a lot better than what you have now. I don't think that = putting a turning vane will help too much without doing something to = energize the boundary layer first. You'll just have a slow thick low = energy layer, and a high energy layer separated by a turning vane.=20 It is really easy to duct tape some aluminum VG's in front of the = inlet and see what it does.=20 You may need a combination of Thomas' contour, VG's and a turning = vane. Go with the easy fix and work your way up in complexity. Monty -------------------------------------------------------------------------= - -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_002F_01C7D02D.335F5560 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Dennis,
 
An imprecise term,  but basically any core = has a=20 maximum amount of heat it can effectively transfer from liquid to air,=20 otherwise, we would all use a tiny radiator and oil cooler.  I = would=20 normally not try to determine if that condition has been reached by = using a core=20 that is assured to transferring the required BTUs from the cooler for a=20 specified air flow.
 
Theoretically, you could set up a test rig so = that you=20 could pump hot oil at a specified temperature through a core.  Have = sufficient airflow (big blower?) to stabilize the oil temp at your max=20 acceptable limit.  Then increase the oil flow/or temperature of the = oil=20 into the core  as well as the air flow to try to keep the temp at = your=20 limit.  At some point, increasing air flow will fail to keep = the=20 temperature from climbing because the core has reached the point=20 where  it=20 is incapable of transferring any significant increase in heat to the air = flow.
 
I only mention it to Al, because my poor memory = can not=20 recall the size of his oil cooler.  Al, has refreshed it with the = size and=20 its plenty big enough for his needs.  So the problem appears to be = air=20 flow.
 
Ed
 
 
 
----- Original Message ----- =
From:=20 Dennis Haverlah
Sent: Thursday, July 26, 2007 = 10:11=20 PM
Subject: [FlyRotary] Re: Oil = cooler inlet=20 - what next?

Ed,

How can a person determine if the oil cooler = is=20 "saturated"? 

Thanks,
Dennis H.

Ed Anderson = wrote:
Sorry to hear your efforts produced no = noticeable=20 improvement, Al.
 
I do have a question - what is the core = volume of your=20 oil cooler?  A stock 2 rotor color has a core area of approx = 19x4/12x2=20 =3D 171 Cubic Inches.  That will cool a two rotor at 160 mph = producing=20 160 Hp with an oil BTU heat factor of 2688 BTU/min.  A 3 rotor=20 producing 1/3 more HP (213 HP) rpm would create a corresponding = rise in=20 BTU/min to 3360.
 
   Is your core big enough to = dissipate that=20 much increase?  Sorry, I just can't remember = what size=20 oil cooler you have.  
 
The reason I ask, is that if forcing more = air through=20 the core does not decrease the oil temp - could = there  exist the=20 possibility that the core is saturated and can is simply not = capable of=20 transferring more oil heat to the air?  If that were the case, = then, as=20 you know,  no amount of additional air through the core would = make any=20 significant difference.
 
 
Ed
 
 
 
 
 
--- Original Message -----
From:=20 Al=20 Gietzen To:=20 Rotary motors in = aircraft=20 Sent:=20 Thursday, July 26, 2007 7:06 PM Subject:=20 [FlyRotary] Re: Oil cooler inlet - what next?

 Installed sheet=20 metal =91baffle=92 to form new upper wall of the diffuser as shown = in the=20 photo.  The idea was to assist in maintaining attached flow, = and to=20 block leakage through the gap at the top.  The baffle was = done in 3=20 pieces in order to insert past the divider/supports in the scoop; = each=20 piece is about 7 =BD=94 wide.  There are gaps between pieces = of about 3/8=20 =96 =BD=94 inch.  The inlet pressure probe was placed at = point=20 =93D=94.

 

Test = flight=20 showed no noticeable difference in delta T on the oil.  The = pressure=20 measured at =93D=94 was 3=94 H2O.  Pressure behind the exit = fairing was=20 again -3/4=94.  The pressures at C and D (measured at = different times)=20 are at about 6=94 from the inboard end of the 22=94 long = cooler.  There=20 may be some variation axially.  Because of the gaps in the = baffle,=20 and fitting around the end tanks, there is still some air = bypassing the=20 cooler; but I don=92t know how significant.  Given the 9+=94 = H2O dynamic=20 pressure out in front of the scoop still indicates not good = pressure=20 recovery.

 

Nonetheless; it=20 is certainly disappointing that there was no change (within the = accuracy=20 of the temp measurements) in the effective cooling.  This = suggests=20 that the wall shape and the air leakage are not the=20 problem.

 

Calculating=20 back from the temp changes in oil and air suggest there is only = about 1000=20 cfm going through the cooler core. The extrapolation of my = measured data=20 on air flow vs pressure drop across the core suggests that at 3=94 = H2O there=20 should be about 2000 cfm through the core.  Because of the=20 centrifugal blower I was using for flow tests I was only able to = get data=20 up to about 0.6=94 H2O and 700 cfm.  I fit the data to=20 Y=3Dax+bx2 using regression analysis, which gave a very = good fit=20 up to that point; but extrapolating out to 3=94 may be stretching = it. =20 If I assume the pressure drop goes as the cube of the flow = velocity, the=20 extrapolation is considerable different =96 about 1330 cfm at 3=94 = H2O.

 

Al

 

 

-----Original=20 Message-----
From: Rotary=20 motors in aircraft [mailto:flyrotary@lancaironlin= e.net]=20 On Behalf Of Al=20 Gietzen
Sent:=20 Friday, July 20,=20 2007 = 10:42 = AM
To: Rotary motors in=20 aircraft
Subject:=20 [FlyRotary] Re: Oil cooler inlet

 

Well; = I may end=20 up with VGs and change in upper duct wall shape. My intention = yesterday=20 was to install VGs as a first step, test fly, measure pressure and = temps;=20 then proceed with installing sheet metal upper duct wall=20 change.

 

In = deciding=20 where to put the VGs, I looked at things with the gear up (Photo = 1).=20  The gear door has a bump, and there is some gap around the=20 door.  Don=92t know what all this does to BL.  Ended up = putting VG=20 toward the left side about 26=94 in font of scoop, and toward the = right side=20 right on the gear door bump.

 

I = then spent a=20 bunch of time trying to get the pressure measuring tube situated.=20  The only access is through the scoop opening, and I can=92t = get my=20 hands in there; so it is very tough.  Plus the tube going in = there,=20 or along the surface in front will affect the flow behavior, so = what=20 affect are we going to measure.  Having multiple measurements = would=20 be great; but very difficult to achieve.

 

While = doing=20 that, I spent some time looking in there with a small mirror. =  What I=20 noted was that initial gaps above and below the cooler (required = to slide=20 the unit in and out) had changed a bit.  The cooler is = supported on=20 pads of =91Cool-Mat=92 insulation.  Those have compressed = just a little,=20 so now there is very little gap at the bottom, and 1/8=94+ along = the=20 top.  That is a fairly substantial leak, and the loss of = pressure at=20 the top likely exacerbates the flow separation.  I decided it = wasn=92t=20 worth going to test the VGs as long as that leakage gap was=20 there.

 

Taking the wing=20 off (mostly getting it back on because of next to impossible = access to=20 nuts), and removing the cooler looks a bit much right now.  I = realized then; that by putting in a sheet metal =91false=92 upper = duct wall, I=20 could extend it up into the gap at the top (photo 2), thereby = changing the=20 shape, and (mostly) closing the gap at the top.

 

The = false wall=20 has to be in three parts for the three openings, and there will be = gaps=20 between because of the supporting dividers; but it could make a=20 substantial difference.  I made the piece for the center, and = considered testing just that; but the upper gap concerns me enough = that I=20 think I=92ll try to get all three fit in.

 

Then = go take a=20 flight test. Unfortunately this combines three changes, VGs, = closing gap,=20 and changing duct wall.  I had hoped to test these one at a=20 time.  If there is a substantial change; it will be easy to = remove=20 the VGs to see what that effect was.

 

Of = course I=92ll=20 let you know when I get some results.

 

Oh, = the price=20 of innovationJ.

 

Al

 

 

-----Original=20 Message-----
From: Rotary=20 motors in aircraft [mailto:flyrotary@lancaironlin= e.net]=20 On Behalf Of = Thomas=20 Jakits
Sent: = Thursday,=20 July 19, 2007 10:31 AM
To: Rotary motors in=20 aircraft
Subject:=20 [FlyRotary] Re: Oil cooler inlet

 

Okay,

 

Monty thinks the emphasis = is on the=20 BL.

I believe = (don't know),=20 the main-problem is the upper ductwall shape. Even if you have = perfect BL=20 flow, the upper wall shape is still not good and will stall the = flow.=20

At the end of the game = you want good=20 flow at all speeds and be able to close any ducts to limit excess = cooling=20 (when you hopefully get there).

Obviously BL will play a = role in your=20 installation as the intake is rather = narrow.

However BL or not - BL = does not mean=20 there is no flow, just slower and more turbulent, but still = generally=20 going towards the cooler.

Aerodynamics in the duct = should be=20 much the same for laminar, turbulent, any flow, as long as there = is=20 flow.

When things stall is when = flow pretty=20 much ceases (in the stalled area ....), no matter how well things = where at=20 the entrance.

The stall in this case is = rather=20 "easy" to get, as the speed seems rather low already. Still may be = good=20 enough if you can do away with the stall.

So I suggest to work on = the duct wall=20 first and optimize it.

 

As suggested, with some = kind of=20 sheet, alu, fiberglass, etc. You can curve it more and more until = you=20 peak.

Maybe pinched ducts = (copyright Ed!!)=20 are not working here, but it may as well - if they work a Ed's = theory=20 explains (energizes the flow...)

 

If this works, modify = according to=20 the best shape found.

Then try to improve with = VGs or=20 sanding or turbolator tape.

Then go for the exit - = after all it=20 is a differential pressure game....

 

TJ

 

On 7/18/07,=20 M Roberts <montyr2157@alltel.net>=20 wrote:

Al,

 

I think you need to = do=20 something to energize the boundary layer. If you can't divert it = you need=20 to put some energy into it. It is probably getting slow and = separating=20 from the face of the duct. That is what your data seems to = indicate to me.=20

 

I like the shape = that Thomas=20 proposes better than what you have now, however, I still think you = will=20 need some VG's in front of the inlet.

 

I know it may seem = counter=20 intuitive, but turbulence may actually help in this case. You will = not get=20 very efficient internal diffusion, but it will be a lot better = than what=20 you have now. I don't think that putting a turning vane will help = too much=20 without doing something to energize the boundary layer first. = You'll just=20 have a slow thick low energy layer, and a high energy layer = separated by a=20 turning vane.

 

It is really easy to = duct tape=20 some aluminum VG's in front of the inlet and see what it does.=20

 

You may need a = combination of=20 Thomas' contour, VG's and a turning vane. Go with the easy fix and = work=20 your way up in complexity.

 

Monty

 

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