Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 855456 for flyrotary@lancaironline.net; Tue, 05 Apr 2005 09:07:17 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.res.rr.com [24.74.185.127]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j35D6S0W029863 for ; Tue, 5 Apr 2005 09:06:29 -0400 (EDT) Message-ID: <002c01c539e0$49f86400$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Cooling Inlet Areas/Bernie's RV9 Date: Tue, 5 Apr 2005 09:06:32 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0029_01C539BE.C2AB41A0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0029_01C539BE.C2AB41A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I agree, Al. =20 I also made essential those points in my response the Rules of Thumb. I would probably enlarge the intake area a bit from the current 28 sq = inch to around 36 sq inches to take care of those Hot days. I'll have = to wait for that 95F day since last summer I spent waiting for prop and = gearbox redo and did not get to test the intakes in the hottest months. = However, I have now flow with the reduced inlet for actually over two = years and while temps to get elevated (200F on oil and 210F on coolant) = on a high power climb, I find that acceptable given that my cruise temps = are ideal between 170-180F. I agree that prop wash and perhaps external = diffusion plays a role as well. Canards clearly have a different = configuration to deal with. Fuel flow actually shows greater that 180HP, but I like being a bit = conservative in any claims in that area. I have had fuel flow of 20 gph = on a cold day and with that denser air. Based on comparison with CAFE = test (very credible) of a fixed pitched prop 180HP Rv 6A of the same = weight my performance is at least as good in speed and better in climb. = But again those are based on what I observe from my flight/engine = instruments not what I would consider hard data. The bottom line is I agree with Al, no one should get too carried away = with my results. I am experimenting and pushing the limits because = they only way you truly know where/what the limits are is to exceed them = (hopefully by not too much). As I have said several times I consider = the 28 sq inches a minimum and I believe (correctly or not) that it = works because the diffuser ducts are reasonably efficient and I do have = a larger than "rule of thumb" out-let area. =20 Perhaps Al, is correct and I am not producing 180 HP, but then I have a = hard time understanding where my 120 lbs overweight RV gets its = 1600-1800 fpm rate of climb otherwise. But, I do agree with Al that = what works for an engine producing 160HP may (will?) not work for an = engine producing 200HP. If it does, then you have too much cooling = capacity for the 160 HP installation and probably more cooling drag than = necessary. Also remember that if your installation is not exactly like the one you = may be borrowing ideas from, then yours is a different installation and = the variable values may not be the same, the interaction and/or = cumulative effect may not be the same, and therefore your results may = not be the same. Onward, get more of those rotaries flying! Its getting tiresome seeing = the same old rotary aircraft at Sun & Fun, need to have new blood show = up. Going out to fly and see what the newly tuned prop does before switching = to manifold #6 Ed . ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Tuesday, April 05, 2005 1:02 AM Subject: [FlyRotary] Re: Cooling Inlet Areas/Bernie's RV9 Before we get too carried away by Ed running with a lot less intake = area than the 'rule-of-thumb' suggests; keep in mind that there are = other variables, and there are some simple laws of physics. The 'rules = of thumb' assume ability for sustained high power with outside air temps = of 90 - 100F. It also assumes an air temp increase through the rad of 40-50F. If = you can achieve higher temp increase, then you can adjust down the flow. = The law of physics is that the air has a known specific heat; i.e., the = amount of heat it will absorb per degree of heat up. Knowing how much = heat you have to dissipate, it tells you directly how much flow you = need, and knowing how fast you are going tells you directly how big an = opening you need to get that much air. When the intakes are up front = behind the prop you get some benefit from 'external diffusion' in front = of the cowl, and perhaps some improved flow from the prop wash. Having more outlet area then the 1.4 factor may also reduce require = inlet area a bit, but at the expense of drag. Ideally you would like to = use some remaining pressure to accelerate the exit air to near free = stream velocity, the larger the outlet the slower the exit air, the more = drag. I would suggest that with 28 sq. in. of intake a.) Ed could not do = sustained full power climb from low altitude on a 95F day, b.) he is = getting greater than 50F air temp increase through the rads, and c.) he = is actually generating less than 180 hp because fuel flow estimate will = give you a max, which is not actually achieved in a rotary because of = unburned fuel burning/going out the exhaust port. I expect he may agree with a. and b. but never c. J; right Ed?=20 Clearly the 'rules-of-thumb' give you more inlet area than needed at = cruise on an average day. That's why cowl flaps are good. Al > Al Gietzen wrote: > > > Doug; > > > > I agree with your 'rule-of-thumb' numbers. My analysis came up = with > > coolant inlet area in sq. in. of 1/3 the HP (.33) for climb out on = a > > 90F day. It assumes a 120kt climb speed for my Velocity. I used = 45% of > > that additional for the oil cooler. Assumes scoop efficiencies of = 85% > > or better. > > > > Al > > > > > Second, even if cooling can get out, if it can't get in, it can't = be > > there to cool the heat exchangers. Rule of thumb: 0.3 sq. in. of > > cowling inlet air opening per HP. 200 HP x .3 =3D 60 sq. in. Note: = This > > assumes a reasonably shaped inlet cowl which has been discussed = online > > often. IMHO: Berni's plane inlet shape and inlet cowl is fine, but = I > > question his inlet opening _area_. > > > snip > > > Don't mean to start another stream of threads on an old subject, = but > > we sweated over this one for 3 months and 3 systems and one might = save > > a lot of time by comparing ones system to these simple "works = great" > > rules of thumb which are the result of LOTS of technical and > > experimental work. > > > > Doug Dempsey > > > > N6415Q and RV7 in process > > > > Colorado, USA > > > > Don't won't do demean or dismiss your experimental work in any way, = but > Ed is running with half the inlet area, and unless something has = changed > with his new found power, he'd doing just fine. Just to be sure that > we're all talking apples, I can confidently quote him at 28 in^2 = inlet > for coolant, which I believe is half of what you recommend above. > Reality isn't meeting theory at eye level here, and everyone will be > much better off if we know why. > > -- > This is by far the hardest lesson about freedom. It goes against > instinct, and morality, to just sit back and watch people make > mistakes. We want to help them, which means control them and their > decisions, but in doing so we actually hurt them (and ourselves)." > I am running with 28 sq inches of total inlet area, much more outlet = area than Doug mentions and not producing 200HP continuos. My best = estimate based on fuel flow is I produce around 180HP perhaps a bit more on a = cooler morning. I agree apples and oranges get compared frequently. But, rules of = thumb are just that - generally a place to get started. I don't think = anyone would say that a rule of thumb means the "optimum" for a specific installation. Just good enough. I have a rule of thumb that says = given enough surface area and airflow you WILL cool. Not too helpful though = and certainly does not address the cooling drag you may impose. I mean if = your rule of thumb says you have to have sufficient area to let the hot air = out and sufficient inlet to let the cold air in - well, OK, I can buy that = - but not too useful. If you put numbers to it like Doug has done that = becomes more useful but is not the final answer. For some of us, rules of thumb are simply a gore to understand what's = behind them. How did they come about, what do they mean? To others they are = a heaven - sent- answer that does not require listening to or reading = this sort of stuff {:>). So I am not certain we need to necessarily even attempt to explain = Rules of Thumb, they are simply a starting point that experience has shown = will work (most of the time). Ed A >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0029_01C539BE.C2AB41A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 I agree, = Al.  
 
 I also made essential those = points in=20 my response the Rules of Thumb.
 
I would probably enlarge the intake = area a bit from=20 the current 28 sq inch to around 36 sq inches to take care of those Hot=20 days.  I'll have to wait for that 95F day since last summer I spent = waiting=20 for prop and gearbox redo and did not get to test the intakes in the = hottest=20 months.  However, I have now flow with the reduced inlet for = actually over=20 two years and while temps to get elevated (200F on oil and 210F on = coolant) on a=20 high power climb, I find that acceptable given that my cruise temps are = ideal=20 between 170-180F.  I agree that prop wash and perhaps external = diffusion=20 plays a role as well.  Canards clearly have a different = configuration to=20 deal with.
 
Fuel flow actually shows greater that = 180HP, but I=20 like being a bit conservative in any claims in that area.  I have = had fuel=20 flow of 20 gph on a cold day and with that denser air.  Based on = comparison=20 with CAFE test (very credible) of  a fixed pitched prop 180HP = Rv=20 6A  of the same weight my performance is at least as good in=20 speed and  better in climb.  But again those are based on = what I=20 observe from my flight/engine instruments not what I would consider hard = data.
 
The bottom line is I agree with Al, no = one should=20 get too carried away with my results.  I am experimenting and =  pushing=20 the limits because they only way you truly know where/what the limits = are is to=20 exceed them (hopefully by not too much).  As I have said several = times I=20 consider the 28 sq inches a minimum and I believe (correctly or not) = that it=20 works because the diffuser ducts are reasonably efficient and I do have = a larger=20 than "rule of thumb" out-let area. 
 
Perhaps Al, is correct and I am not = producing 180=20 HP, but then I have a hard time understanding where my 120 lbs = overweight RV=20 gets its 1600-1800 fpm rate of climb otherwise.  But, I do agree = with Al=20 that what works for an engine producing 160HP may (will?) not  work = for an=20 engine producing 200HP.  If it does, then you have too much cooling = capacity for the 160 HP installation and probably more cooling drag than = necessary.
 
Also remember that if your installation = is not=20 exactly like the one you may be borrowing ideas from,  then yours = is a=20 different installation and the variable values may not be the same, the=20 interaction and/or cumulative effect may not be the same, and therefore = your=20 results may not be the same.
 
Onward, get more of those rotaries = flying! =20 Its getting tiresome seeing the same old rotary aircraft at Sun & = Fun, need=20 to have new blood show up.
 
Going out to fly and see what the newly = tuned prop=20 does before switching to manifold #6
 
 
Ed .
 
 
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Tuesday, April 05, 2005 = 1:02=20 AM
Subject: [FlyRotary] Re: = Cooling Inlet=20 Areas/Bernie's RV9

Before we get too = carried away=20 by Ed running with a lot less intake area than the =91rule-of-thumb=92 = suggests;=20 keep in mind that there are other variables, and there are some simple = laws of=20 physics.  The =91rules of thumb=92 assume ability for sustained = high power=20 with outside air temps of 90 =96 100F.

 

It also assumes an air = temp=20 increase through the rad of 40-50F.  If you can achieve higher = temp=20 increase, then you can adjust down the flow.  The law of physics = is that=20 the air has a known specific heat; i.e., the amount of heat it will = absorb per=20 degree of heat up.  Knowing how much heat you have to dissipate, = it tells=20 you directly how much flow you need, and knowing how fast you are = going tells=20 you directly how big an opening you need to get that much air.  = When the=20 intakes are up front behind the prop you get some benefit from = =91external=20 diffusion=92 in front of the cowl, and perhaps some improved flow from = the prop=20 wash.

 

Having more outlet = area then the=20 1.4 factor may also reduce require inlet area a bit, but at the = expense of=20 drag.  Ideally you would like to use some remaining pressure to=20 accelerate the exit  air to near free stream velocity, the larger = the=20 outlet the slower the exit air, the more drag.

 

I would = suggest=20 that with 28 sq. in. of intake a.) Ed could not do sustained full = power climb=20 from low altitude on a 95F day, b.) he is getting greater than 50F air = temp=20 increase through the rads, and c.) he is actually generating less than = 180 hp=20 because fuel flow estimate will give you a max, which is not actually = achieved=20 in a rotary because of unburned fuel burning/going out the exhaust=20 port.

 

I expect = he may=20 agree with a. and b. but never c. J; = right Ed?=20

 

Clearly = the=20 =91rules-of-thumb=92 give you more inlet area than needed at cruise on = an average=20 day.  That=92s why cowl flaps are good.

 

Al

 

> Al Gietzen wrote:

>

> > Doug;

> >

> > I agree with your = =91rule-of-thumb=92 numbers.=20 My analysis came up with

> > coolant inlet area in sq. in. of = 1/3 the HP=20 (.33) for climb out on a

> > 90F day. It assumes a 120kt climb = speed for=20 my Velocity. I used 45% of

> > that additional for the oil = cooler. Assumes=20 scoop efficiencies of 85%

> > or better.

> >

> > Al

> >

>

> > Second, even if cooling can get = out, if it=20 can't get in, it can't be

> > there to cool the heat exchangers. = Rule of=20 thumb: 0.3 sq. in. of

> > cowling inlet air opening per HP. = 200 HP x=20 .3 =3D 60 sq. in. Note: This

> > assumes a reasonably shaped inlet = cowl which=20 has been discussed online

> > often. IMHO: Berni's plane inlet = shape and=20 inlet cowl is fine, but I

> > question his inlet opening=20 _area_.

> >

> snip

>

> > Don't mean to start another stream = of=20 threads on an old subject, but

> > we sweated over this one for 3 = months and 3=20 systems and one might save

> > a lot of time by comparing ones = system to=20 these simple "works great"

> > rules of thumb which are the = result of LOTS=20 of technical and

> > experimental = work.

> >

> > Doug Dempsey

> >

> > N6415Q and RV7 in = process

> >

> > Colorado, USA

> >

>

> Don't won't do demean or dismiss your=20 experimental work in any way, but

> Ed is running with half the inlet area, = and=20 unless something has changed

> with his new found power, he'd doing = just fine.=20 Just to be sure that

> we're all talking apples, I can = confidently quote=20 him at 28 in^2 inlet

> for coolant, which I believe is half of = what you=20 recommend above.

> Reality isn't meeting theory at eye = level here,=20 and everyone will be

> much better off if we know = why.

>

> --

> This is by far the hardest lesson about = freedom.=20 It goes against

> instinct, and morality, to just sit = back and=20 watch people make

> mistakes. We want to help them, which = means=20 control them and their

> decisions, but in doing so we actually = hurt them=20 (and ourselves)."

>

 

I=20 am running with 28 sq inches of total inlet area, much more outlet=20 area

than Doug mentions and  not producing = 200HP=20 continuos.  My best estimate

based on fuel flow is I produce around 180HP = perhaps a=20 bit more on a cooler

morning.

 

 I agree apples and oranges get = compared=20 frequently.  But, rules of thumb

are just that - generally a place to get=20 started.  I don't think anyone

would say that a rule of thumb means the = "optimum" for=20 a specific

installation.  Just good enough.  = I have a=20 rule of thumb that says given

enough surface area and airflow you WILL = cool. =20 Not too helpful though and

certainly does not address the cooling drag = you may=20 impose.  I mean if your

rule of thumb says you have to have = sufficient area to=20 let the hot air out

and sufficient inlet to let the cold air in = - well,=20 OK, I can buy that - but

not too useful.  If you put numbers to = it like=20 Doug has done that becomes

more useful but is not the final=20 answer.

 

For some of us, rules of thumb are simply a = gore to=20 understand what's behind

them. How did they come about, what do they=20 mean?  To others they are a

heaven - sent- answer that does not require = listening=20 to or reading this

sort of stuff {:>).

 

So I am not certain we need to  = necessarily even=20 attempt to explain  Rules

of Thumb, they are simply a starting point = that=20 experience has shown will

work (most of the time).

 

Ed A

 

 

 

 

>>  Homepage: =20 http://www.flyrotary.com/

>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html

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