X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 17 Feb 2013 14:16:22 -0500 Message-ID: X-Original-Return-Path: Received: from nm36.bullet.mail.ne1.yahoo.com ([98.138.229.29] verified) by logan.com (CommuniGate Pro SMTP 6.0.1) with ESMTPS id 6067841 for lml@lancaironline.net; Sat, 16 Feb 2013 23:52:19 -0500 Received-SPF: none receiver=logan.com; client-ip=98.138.229.29; envelope-from=chris_zavatson@yahoo.com Received: from [98.138.90.52] by nm36.bullet.mail.ne1.yahoo.com with NNFMP; 17 Feb 2013 04:51:44 -0000 Received: from [98.138.89.164] by tm5.bullet.mail.ne1.yahoo.com with NNFMP; 17 Feb 2013 04:51:44 -0000 Received: from [127.0.0.1] by omp1020.mail.ne1.yahoo.com with NNFMP; 17 Feb 2013 04:51:44 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 785826.88669.bm@omp1020.mail.ne1.yahoo.com Received: (qmail 75726 invoked by uid 60001); 17 Feb 2013 04:51:44 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Rocket-MIMEInfo:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=GdvioNuURJmWjJoM1ha+vCsQ/65qKFbHMUpCoCJCg3Wa/wEZiUa9WFnByd/6nSfT0ZnatVm0lPZVfAoJ5kRs8098Cqs8zskhEa/P0rWnNIGrqokFEFPhRuWEDVzvT+Qs0H1BzyW0vulot6r5p7A7VxHHJIVKqwY/1/lha20E03s=; X-YMail-OSG: 2h4UK1gVM1mcVXvXBmuRj3qNCfoUfqMwQIqyGmPaBEk0W9g 6yWtoWPO_I8QdYLJ5Uacymx46drO0EaW1oUzVeohzFat6VES_6hw1I_SiY0e R_66fmV_tc0ArMV9R8TY9aRWC_K4GFbrWIT4v.ZeMQEd_pWmx.6iSYn7oYAb F.PQ7ZyOKPrcriMb2oG6dUaQx7hw2VN.9vd4vzQYO8uu0N_Sv89tkmiH27sd B0rb7OHY27OelETDCyJONCkU.EBpmhSD.VLRnWm_5t6n3BGlXDwp.IHJ3k2H ZkiFjCFstt6p_XTnu23sH5KK_fi363_lkIIpyfi6cIJN1AHJT5VeiHxah.oN TsOzWxIlx22BXCZBY5GV9vq9_RHFb_V.AIlQC4NTdvVqEturxtkkOLnQ4Urn SKQZUxSgj9XV0pciQhcTb6P1QZTcG00HenYR1RSJ2lIk.V5LrZx5i3vLdAkp fjqzKY.gaQXFDY1hUvzA2o9UXpv51rhmdVeYBRIjU0xFE_c4fPVG7DEvVWHJ yvv85B2QcU3VGsonzBvIMSJqcg5STK72c4Y6tLOxeu.236UkkHt0IM6G1MgX tO14tKW1aukTDaTz25IIjbCLdwA-- Received: from [76.246.32.109] by web121606.mail.ne1.yahoo.com via HTTP; Sat, 16 Feb 2013 20:51:44 PST X-Rocket-MIMEInfo: 001.001,wqAKR2FyeSxldCBhbApJIHRob3VnaHQgSSB3b3VsZCBhZGQgYSBmZXcgY29tbWVudHPCoHdpdGggcmVzcGVjdCB0byBzb21lwqAzMjAvMzYwIHVuaXF1ZSBpc3N1ZXMuwqAgCsKgCiJNb3N0IExhbmNhaXIgaW5sZXRzIGFyZSBvdmVyc2l6ZSBhbmQgdGhlIHZlbG9jaXR5IGdvaW5nIGluIHRoZSBpbmxldCBpcyBwcm9iYWJseSBoYWxmIHRoZSBmcmVlIHN0cmVhbSB2ZWxvY2l0eS4iCsKgCkV2ZXJ5IExhbmNhaXIgbW9kZWwgYWZ0ZXIgdGhlIDMyMC8zNjAgc2F3IGEgZ3JlYXRseSBpbmNyZWFzZWQgaW5sZXQgc2kBMAEBAQE- X-Mailer: YahooMailWebService/0.8.133.508 References: X-Original-Message-ID: <1361076704.28119.YahooMailNeo@web121606.mail.ne1.yahoo.com> X-Original-Date: Sat, 16 Feb 2013 20:51:44 -0800 (PST) From: Chris Zavatson Reply-To: Chris Zavatson Subject: Re: [LML] Re: IV (not IVP) Intake pictures X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="1458340343-501037941-1361076704=:28119" --1458340343-501037941-1361076704=:28119 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable =A0=0AGary,et al=0AI thought I would add a few comments=A0with respect to s= ome=A0320/360 unique issues.=A0 =0A=A0=0A"Most Lancair inlets are oversize = and the velocity going in the inlet is probably half the free stream veloci= ty."=0A=A0=0AEvery Lancair model after the 320/360 saw a greatly increased = inlet size in terms of in^2 per hp.=A0 Even visually the 320/360 inlets "lo= ok" small.=A0 When I measured the actual=A0mass flow=A0in the inlet, it was= very near free=A0stream velocity.=A0=A0That means there is no pressure rec= overy ahead of the inlet at all.=A0 This goes a long way to explaining why = many of the little two-seaters run on the warmer side.=0AIf the inlet size = is to remain this small, the design approach needs to emphasize a different= set of parameters.=A0 All of a sudden internal flow control becomes super = critical.=A0 This means proper internal inlet radii and diffusers to contro= l flow expansion.=A0 The upper limit of what is possible in terms of pressu= re recovery is much reduced over what=A0can be achieved with external press= ure recovery.=A0 This less than optimum pressure recovery is traded against= cleaner external flow.=A0 The tiny inlet with a 1.0 inlet velocity ratio w= ill merely carve out a section of the oncoming air mass and leave the rest = undisturbed.=0AAll of the points=A0Fred made=A0regarding flow=A0down stream= of the inlets apply here just the same.=A0=A0The negative consequence are = perhaps just amplified.=A0 Leaks, for example,=A0increase the total flow vo= lume. Since the inlet velocity=A0in these tiny inlets is already extremely = high, leaks serve only to drive the inlet velocity to unmanageable levels -= and losses.=0AUnfortunately many of the old studies on GA engine cooling= =A0do not provide much useful information for really small inlets as=A0they= =A0require many=A0features=A0behind the inlet to be controlled as well.=A0 = Studies that merely change inlet size will easily conclude that inlet veloc= ity ratios above 0.7 are suicidal.=A0 At least=A0one researcher added notes= in the text stating that "better results could perhaps be obtained with th= e use of diffusers..."=0AThus the success of small inlets remains very much= =A0tied to the details of each implementation.=0A=A0=0AChris Zavatson=0AN91= CZ=0A360 std 1,400 hrs (lock-up free)=0Ahttp://www.n91cz.net/ =0A=0A_______= _________________________=0A From: Gary Casey =0ATo: = lml@lancaironline.net =0ASent: Thursday, February 14, 2013 5:36 AM=0ASubjec= t: [LML] Re: IV (not IVP) Intake pictures=0A =0A=0APaul,=0ANeedless to say= , this is a complex and difficult subject. =A0You are right in that if you = could get a high velocity airflow directed at the cylinder it would likely = be more efficient than slowing the air and then speeding it back up again t= o go over the fins. =A0But, the likelihood of getting all the right jets of= air to blow in all the right places is almost zero. =A0So the alternative = is to slow the air down to a very low velocity and then allow it to "bath" = the cylinders with air, the velocity picking up where the area between the = fins is least. =A0But that's not to say that the bigger the plenum the bett= er. =A0Inside large plenums you can bet there are high velocity jets and wh= irlwinds everywhere. =A0So it's a matter of degree. =A0Most Lancair inlets = are oversize and the velocity going in the inlet is probably half the frees= tream velocity. =A0That means that fully 3/4 of the kinetic energy is gone = before the air gets into the plenum, hopefully converted to pressure energy. =A0Then some more gets lost swirling around in the plenum= , probably not converted to pressure. =A0Most engine-mounted plenums I have= seen are probably half to 3/4 of the volume of the cowl plenum, so I think= there isn't much to be gained by using the cowl as the plenum. =A0But the = cowl is free and weighs nothing (it's already there), so most people use th= e cowl. =A0You could design a minimum-volume plenum, but that gets you back= to my first comment.=0A=0AAs you would guess, more data is better, and mor= e confusing than less, so sure, measure the lower cowl area as well. =A0And= several places in the upper with a pitot tube. =A0The static pressure meas= urement in the upper mostly tells you whether or not the inlets are efficie= nt and not a lot about leakage. =A0After all, the engine itself is likely t= he biggest "leak" and other leaks are small by comparison. =A0So they won't= affect the plenum pressure by enough to detect.=0A=0AAll just my opinions,= of course!=0AGary=0A=0AFred: the whole explanation is contrary to what I b= elieved. =A0It seems the best solution is to provide a large reservoir for = the stream to enter, settle, then be fed down through the cylinders. =A0I w= ould have thought feeding the high speed flow onto the cylinder might be mo= re efficient but I can imagine how that would leave hot spots or low pressu= re areas inside the cowl.=0A=0AI'm still a little confused as to why the la= rger reservoir is needed unless it is simply to assist slowing the flow and= providing more even coverage of the cylinders. =A0 =A0 =A0A plenum is a sm= aller reservoir and I'm guessing the lower losses of a plenum are dramatic = compared to losses in a normal cowl?=0A=0ASo, given your summary, if a plen= um is not used, the best method for measuring the seal of a typical cowl wo= uld be differential pressure measurements from pitot at inlet to static ins= ide the cowl? =A0If I measure static pressure within the cowl at a certain = airspeed, can I make a stab at the losses in the cowl from the seals by mea= suring airspeed or do I need to measure static at the bottom cowl area as w= ell?=0A=0APaul=0ALegacy --1458340343-501037941-1361076704=:28119 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
 
Gary,et al
I thought I wou= ld add a few comments with respect to some 320/360 unique issues.=  
 
"Most Lancair = inlets are oversize and the velocity going in the inlet is probably half th= e free stream velocity."=
 
Every Lancair model after the 320/360 sa= w a greatly increased inlet size in terms of in^2 per hp.  Even visual= ly the 320/360 inlets "look" small.  When I measured the actual m= ass flow in the inlet, it was very near free stream velocity.&nbs= p; That means there is no pressure recovery ahead of the inlet at all.  This goes a long way to explaining why many of the little two-<= span id=3D"misspell-5" class=3D"mark">seaters run on the warmer side= .
If the inlet size is to remain this small, the design approach = needs to emphasize a different set of parameters.  All of a sudden int= ernal flow control becomes super critical.  This means proper internal= inlet radii and diffusers to control flow expansion.  The upper limit= of what is possible in terms of pressure recovery is much reduced over wha= t can be achieved with external pressure recovery.  This less tha= n optimum pressure recovery is traded against cleaner external flow.  = The tiny inlet with a 1.0 inlet velocity ratio will merely carve out a sect= ion of the oncoming air mass an= d leave the rest undisturbed.
All of the points Fred made&nb= sp;regarding flow down stream of the inlets apply here just the same.  The negative consequence are perhaps just amplified. = ; Leaks, for example, increase the total flow volume. Since the inlet = velocity in these tiny inlets is already extremely high, leaks serve o= nly to drive the inlet velocity to unmanageab= le levels - and losses.
Unfortunately many of the old studies on GA engine cooling=  do not provide much useful information for really small inlets as they require many f= eatures behind the inlet to be controlled as well.  Studies that = merely change inlet size will easily conclude that inlet velocity ratios ab= ove 0.7 are suicidal.  At least one researcher added notes in the= text stating that "better results could perhaps be obtained with the use o= f diffusers..."
Thus the success of small inlets remains very much tied to the details of each imple= mentation.
 
Chris Zavatson
N91CZ
360 std 1,400 hrs (lock-up free)
From: Gary Cas= ey <casey.gary@yahoo.com>
T= o: lml@lancaironline.net
Sent: Thursday, February 14, 2013 5:36 AM
Subject: [LML] Re: IV (not IVP) Intake pictures

=0A
Paul,
Needless to say, this is a complex an= d difficult subject.  You are right in that if you could get a high ve= locity airflow directed at the cylinder it would likely be more efficient t= han slowing the air and then speeding it back up again to go over the fins.=  But, the likelihood of getting all the right jets of air to blow in = all the right places is almost zero.  So the alternative is to slow th= e air down to a very low velocity and then allow it to "bath" the cylinders= with air, the velocity picking up where the area between the fins is least= .  But that's not to say that the bigger the plenum the better.  = Inside large plenums you can bet there are high velocity jets and whirlwind= s everywhere.  So it's a matter of degree.  Most Lancair inlets are oversize and the velocity=0A going in the inlet is prob= ably half the freestream vel= ocity.  That means that fully 3/4 of the kinetic energy is gone before= the air gets into the plenum, hopefully converted to pressure energy. &nbs= p;Then some more gets lost swirling around in the plenum, probably not conv= erted to pressure.  Most engine-mounted plenums I have seen are probab= ly half to 3/4 of the volume of the cowl plenum, so I think there isn't muc= h to be gained by using the cowl as the plenum.  But the cowl is free = and weighs nothing (it's already there), so most people use the cowl.  = ;You could design a minimum-volume plenum, but that gets you back to my fir= st comment.

As you would guess, more data= is better, and more confusing than less, so sure, measure the lower cowl area as well.=0A  And several places in = the upper with a pitot tube.=  The static pressure measurement in the upper mostly tells you whethe= r or not the inlets are efficient and not a lot about leakage.  After = all, the engine itself is likely the biggest "leak" and other leaks are sma= ll by comparison.  So they won't affect the plenum pressure by enough = to detect.

All just my opinions,= of course!
Gary

Fred: the whole explanation is contrary to what= I believed.  It seems the best solution is to provide a large reservo= ir for the stream to enter, settle, then be fed down through the cylinders.=  I would have thought feeding the high speed flow=0A onto the cylinde= r might be more efficient but I can imagine how that would leave hot spots = or low pressure areas inside the cowl.

I'm still a= little confused as to why the larger reservoir is needed unless it is simp= ly to assist slowing the flow and providing more even coverage of the cylin= ders.      A plenum is a smaller reservoir and I'm guessing = the lower losses of a plenum are dramatic compared to losses in a normal co= wl?

So, given your summary, if a plenum is not use= d, the best method for measuring the seal of a typical cowl would be differ= ential pressure measurements from p= itot at inlet to static inside the cowl?  If I measure static p= ressure within the cowl at a certain airspeed, can I make a stab at the los= ses in the cowl from the seals by measuring airspeed or do I need to measur= e static at the bottom cowl area as=0A well?

Paul<= /div>
Legacy


 
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