X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 22 Dec 2009 07:50:16 -0500 Message-ID: X-Original-Return-Path: Received: from web57501.mail.re1.yahoo.com ([66.196.100.68] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with SMTP id 4034799 for lml@lancaironline.net; Tue, 22 Dec 2009 07:21:35 -0500 Received-SPF: none receiver=logan.com; client-ip=66.196.100.68; envelope-from=casey.gary@yahoo.com Received: (qmail 48657 invoked by uid 60001); 22 Dec 2009 12:20:59 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=0SFvF5SGzbpvYJcE9VnsAjpahw8GY+CmriZlwEAva8Mwvq6cpV9S/nl45mZtKvUN9XrP2Y8Synecc5BMnpOt/xHYRWKPHugkW8PbAXT5xZJCUFAwTDc9R6u1IOk5WyrbMp9fkBNcLPejscz0fFqxoF3pkZQsas2Uae0JRAyNbBg=; X-Original-Message-ID: <637895.48034.qm@web57501.mail.re1.yahoo.com> X-YMail-OSG: 2xCvgukVM1m63rbFhM85htj.RdLAtRLtKRwxikhgQ_nWJJeXHXIUEm.Ctoob8B3UuVUKgYDlFrxKUsvRXcLA69ZYCPQscFKYc__Dq3_hqsG6AsO0wM_.phT7PnJdFkG.q_bXd4wWR9A.kRsRC3wDCnmDiW7ZH84SZcM4knVqyDCHUwbhnUUxYerFTCtjSX0kTn._cRTw9r7LZFNRFOpB9TEueNfrphegbZxeXNbjN6gC8yfWG9HOud1d9LaOkkBttiRNBJSvPofFNQULG3KfMbJXpSVtTS5coBXXFqVNEns- Received: from [97.122.191.52] by web57501.mail.re1.yahoo.com via HTTP; Tue, 22 Dec 2009 04:20:59 PST X-Mailer: YahooMailRC/240.3 YahooMailWebService/0.8.100.260964 References: X-Original-Date: Tue, 22 Dec 2009 04:20:59 -0800 (PST) From: Gary Casey Subject: Re: io-550 vs. tsio-550 differences? X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-2053377142-1261484459=:48034" --0-2053377142-1261484459=:48034 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable I agree with George, the difference of his and my position is based on the = assumption of operating conditions, not the technology itself. I was assum= ing "turbonormalized" carried with it the assumption that the operator woul= d use "traditional" power settings. Most naturally-aspirated engines will = have a sea level WOT manifold pressure of maybe 29 inches, so operating at = 30 is already ever-so-slightly higher. Most traditional methods shown in P= OH's and, as I have observed, used by many, if not most, pilots utilize a c= ruise of 75% of max power. For an engine rated at 2700 rpm at sea level, t= hat equates to a setting of something like 2400rpm and 24 inches. I made t= he (incorrect?) assumption that "turbonormalized" means the pilot will cont= inue to use approximately the same settings, but use the turbocharger to ma= intain those settings at altitude. That's probably the most conservative a= ssumption - and one that matches my own past experience, limited as it may be. George assumes that essentially all operators will take full a= dvantage of the capability of "modern" turbonormalizing systems, which are = apparently dramatically improved compared to traditional approaches, and op= erate the engine at almost full power regardless of altitude. I say "almos= t" because LOP operation will result in a loss of maybe 5 or 10% compared t= o ROP operation that would presumably be used for takeoff. I suppose rpm c= ould be reduced to drop the noise level, but the manifold pressure would pr= esumably remain at some maximum. Incidentally, I see no substantial differ= ence in the compression ratio of "modern" engines compared to "traditional"= (NA or TN)engines - 8.5 to 9.0 seems to have been the norm for many years.= And what about that takeoff from Centennial at 110F? Yup, the non-afterc= ooled engine will suffer in that condition. But how often is one likely to= take off from a "hot AND high" airport? I've never seen Centennial at 110, but that doesn't mean it can't happen there or somewhere else. Ma= ybe Flagstaff or Durango.=0AGeorge also suggests that "modern" pilots will = operate "modern" TN systems in the maximum performance mode all the time (3= 0 inches manifold pressure). For the specified 4-hour flight this would in= clude a climb at 1,000 fpm up to 18,000 to be followed by a descent at 500 = fpm all the way to the ground. Really? For most reasonably heavy aircraft= this would entail climbing at Vy, but I find myself, when pointed where I = want to go, climbing at a speed of at least 20 knots faster than Vy, result= ing in a lower climb rate. After all, I want to get where I'm going, not j= ust get high. and then I find myself starting the descent early and to sav= e fuel descend at less than 500 fpm and I spend some time maneuvering at lo= w altitude before landing. And, unless the aircraft is equipped with an el= ectronically-controlled oxygen system, Many fuel stops will also result in = a visit from the (expensive) oxygen cart. And George maintains that pretty= much all operation will be at 18,000, so I guess that includes westbound against headwinds. = But maybe I'm as old-fashioned as I look :-).=0AGary, not TN, but always LO= P, thanks to George=0A=0A=0A=0A=0A________________________________=0AAh.. I= think I see the problem. How much time is spent at 30 =E2=80=9C MAP ? I= n the fleet of well over 1,500 turbonormalized airplanes that TAT supports= - - - the amount of time in cruise that is spent at 30=E2=80=9D MAP is = very close to 100% of climb and cruise. Essentially everything but descent= and landing. But it is not spend at 30 gph. It is spent at about 16.5 to= 17.5 gph. Essentially, WOTLOPSOP.=0A =0AAnd, the climbs are more typi= cally 15 to 18 minutes, not 30 minutes. And the portion of a 4 hour fligh= t that will be spent at altitude at 30=E2=80=9D WOTLOP will be around 3 ho= urs. And a very large percentage of those owners fly those aircraft at alt= itude a large percentage of the time.=0A =0AIn short, the current generati= on turbonormalized aircraft are very very different from the low compress= ion engine operations at reduced manifold pressures that you are referring = to and which I spent thousands of hours pursuing back in the 1960s, 70s and= 80s .=0A =0A =0A =0A>> At lower manifold pressures the higher inlet temper= atures are not as detrimental as they are at full power, where they limit t= he power output. In other words, 25 inches with a 150F inlet might be equi= valent in power - and nearly equivalent in efficiency - to 24 inches at 100= F inlet. <<=0A =0AI can tell you that it has been more than 13 years since = I deliberately operated a turbocharged engine at 24 or 25=E2=80=9D in crui= se, or at anything less than 29.x =E2=80=9C MAP in cruise. That is a ter= rible waste of a good engine and turbocharger to do that!=0A =0A =0A>> Anot= her thing to be aware of - the inlet air temperature does not exactly match= the temperature of the inlet charge as it is trapped in the cylinder, whic= h is, after all, what counts. Tests I have seen show that the charge is he= ated about halfway to the cylinder temperature. If the cylinder temp is 30= 0F and the incoming charge is 100 the resulting charge temperature is about= 200. Increase the inlet temp from 100 to 200 and the trapped charge will = be at 250, only 50 higher. While no one is truly an average operator, my = point was that chasing the optimum performance at 18,000 feet may not be wo= rth the cost and development expense. Depends on your goals. All flights = involve operation below 10,000 feet while a limited number involve operatio= n above 18,000. <<=0A =0AIf you are operating the airplane WOTLOP at 8000 f= eet, on a hot summer day, a good intercooler will drop the induction air= temperature around 80d F. That may mean the induction air temp is down= around 80dF rather than up around 160dF. That provides a huge margin in = protection from detonation - - even when operating at lower altitudes.=0A = =0A =0A>> When flying my TR182 on a lot of cross-countries I flew between 1= 2 and 15 a lot, but flew above 18,000 only a couple of times in 5 years. L= ike in the drug commercials, these comments are directed only at turbonorma= lized nonpressurized oxygen-equipped aircraft operated in non-commercial en= vironments. Oh, yeah - and by "average" resource-limited owners :-) <<=0A= =0A>>I'm not sure I agree with George when he says that "Intercoolers have= large benefits - - - even at sea level." In this case the turbo is produ= cing negligible pressure, so the temperature rise is dependent only on the = heat picked up going through the turbo and the small compression heating wh= en the turbo has to overcome its own flow restriction. This is also true w= hen cruising at less than 10,000 feet at reduced manifold pressure. Is the= added weight, cost and aerodynamic drag more of a detriment than the cooli= ng is a benefit?=0AGary <<=0A =0AConsider this example: Non intercooled. = Denver/Centennial. August. 110dF on the runway. Full power takeoff. = 30=E2=80=9D MAP. =0A =0AAsk yourself what the induction air temperature is = with a typical compressor operating off its design point at about 60-65% e= fficiency ?=0A =0AThen ask if you would like to have an intercooler, or not= ? =0A =0AThen try the same thing at Durango.=0A =0ARegards, George=0A=0A= =0A --0-2053377142-1261484459=:48034 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
I agree with George, the difference of his and my = position is based on the assumption of operating conditions, not the techno= logy itself.  I was assuming "turbonormalized" carried with it the ass= umption that the operator would use "traditional" power settings.  Mos= t naturally-aspirated engines will have a sea level WOT manifold pressure o= f maybe 29 inches, so operating at 30 is already ever-so-slightly higher. &= nbsp;Most traditional methods shown in POH's and, as I have observed, used = by many, if not most, pilots utilize a cruise of 75% of max power.  Fo= r an engine rated at 2700 rpm at sea level, that equates to a setting of so= mething like 2400rpm and 24 inches.  I made the (incorrect?) assumptio= n that "turbonormalized" means the pilot will continue to use approximately the same settings, but use the turbocharger to maintain thos= e settings at altitude.  That's probably the most conservative assumpt= ion - and one that matches my own past experience, limited as it may be. &n= bsp;George assumes that essentially all operators will take full advantage = of the capability of "modern" turbonormalizing systems, which are apparentl= y dramatically improved compared to traditional approaches, and operate the= engine at almost full power regardless of altitude.  I say "almost" b= ecause LOP operation will result in a loss of maybe 5 or 10% compared to RO= P operation that would presumably be used for takeoff.  I suppose rpm = could be reduced to drop the noise level, but the manifold pressure would p= resumably remain at some maximum.  Incidentally, I see no substantial = difference in the compression ratio of "modern" engines compared to "tradit= ional" (NA or TN)engines - 8.5 to 9.0 seems to have been the norm for many years.  And what about that takeoff from Centennial at 110F?=  Yup, the non-aftercooled engine will suffer in that condition.  = ;But how often is one likely to take off from a "hot AND high" airport? &nb= sp;I've never seen Centennial at 110, but that doesn't mean it can't happen= there or somewhere else.  Maybe Flagstaff or Durango.
Georg= e also suggests that "modern" pilots will operate "modern" TN systems in th= e maximum performance mode all the time (30 inches manifold pressure). &nbs= p;For the specified 4-hour flight this would include a climb at 1,000 fpm u= p to 18,000 to be followed by a descent at 500 fpm all the way to the groun= d.  Really?  For most reasonably heavy aircraft this would entail= climbing at Vy, but I find myself, when pointed where I want to go, climbi= ng at a speed of at least 20 knots faster than Vy, resulting in a lower cli= mb rate.  After all, I want to get where I'm going, not just get high.  and then I find myself starting the descent early and to s= ave fuel descend at less than 500 fpm and I spend some time maneuvering at = low altitude before landing.  And, unless the aircraft is equipped wit= h an electronically-controlled oxygen system, Many fuel stops will also res= ult in a visit from the (expensive) oxygen cart.  And George maintains= that pretty much all operation will be at 18,000, so I guess that includes= westbound against headwinds.  But maybe I'm as old-fashioned as I loo= k :-).
Gary, not TN, but always LOP, thanks to George
<= br>

<= span class=3D"Apple-style-span" style=3D"font-weight: normal; ">

Ah.. I t= hink I see the problem.  How much time  is spent at 30 =E2=80=9C = MAP ?  In the fleet of well over 1,500  turbonormalized airplanes= that TAT supports  - - - the amount of time in cruise that is spent a= t 30=E2=80=9D  MAP is  very close to 100% of climb and cruise.&nb= sp; Essentially everything but descent and landing.  But it is not spe= nd at 30 gph.  It is spent at about 16.5 to 17.5 gph.   Esse= ntially,   WOTLOPSOP.

=  

 

In short,  the current generation  turbonormalized  aircraft a= re very very different from the low compression engine operations at reduce= d manifold pressures that you are referring to and which I spent thousands = of hours pursuing back in the 1960s, 70s and 80s .

 <= /i>

 

 

>> At lower manifold pressures the higher inlet temperatures are n= ot as detrimental as they are at full power, where they limit the power out= put.  In other words, 25 inches with a 150F inlet might be equivalent = in power - and nearly equivalent in efficiency - to 24 inches at 100F inlet= . <<

=

 <= /p>

I can tell you that it has been more than 13 years since I deliberat= ely operated a  turbocharged engine at 24 or 25=E2=80=9D in cruise,&nb= sp; or at anything less than 29.x =E2=80=9C MAP in cruise.   That= is a terrible waste of a good engine and turbocharger to do that!

 

 

>>&n= bsp;Another thing to be aware of - the inlet air temperature does not exact= ly match the temperature of the inlet charge as it is trapped in the cylind= er, which is, after all, what counts.  Tests I have seen show that the= charge is heated about halfway to the cylinder temperature.  If the c= ylinder temp is 300F and the incoming charge is 100 the resulting charge te= mperature is about 200.  Increase the inlet temp from 100 to 200 and t= he trapped charge will  be at 250, only 50 higher.  While no one = is truly an average operator, my point was that chasing the optimum performance at 18,000 feet may not be worth the cost and development expen= se.  Depends on your goals.  All flights involve operation below = 10,000 feet while a limited number involve operation above 18,000. <<

 

If you are operating the airplane WOTLOP at 8000 feet,  on a hot s= ummer day,  a good  intercooler will drop the induction air tempe= rature around 80d F.     That may mean the induction ai= r temp is down around 80dF rather than up around 160dF.   That provides a = huge margin in protection from detonation - - even when operating at lower = altitudes.

 

 

>> When flying my TR182 on a lot of cross-countries I flew between 12= and 15 a lot, but flew above 18,000 only a couple of times in 5 years. &nb= sp;Like in the drug commercials, these comments are directed only at turbon= ormalized nonpressurized oxygen-equipped aircraft operated in non-commercia= l environments.  Oh, yeah - and by "average" resource-limited owners := -)  <<

 

>>I= 'm not sure I agree with George when he says that "Intercoolers have large ben= efits  - - - even at sea level."  In this case the turbo is produ= cing negligible pressure, so the temperature rise is dependent only on the = heat picked up going through the turbo and the small compression heating wh= en the turbo has to overcome its own flow restriction.  This is also t= rue when cruising at less than 10,000 feet at reduced manifold pressure. &n= bsp;Is the added weight, cost and aerodynamic drag more of a detriment than= the cooling is a benefit?

Gary <<

Consider thi= s example:  Non intercooled.   Denver/Centennial.  Augu= st.  110dF on the runway.   Full power takeoff.   = 30=E2=80=9D MAP. 

&n= bsp;

Ask yours= elf what the induction air temperature is with a typical compressor operati= ng off its design point at about  60-65% efficiency ?

 

Then ask if you would like to have an in= tercooler, or not ? 

 

Then try the same thing at Durango.

 

Regards,&nbs= p; George

 

<= /span>
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