X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 23 Apr 2009 20:40:50 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-mealy.atl.sa.earthlink.net ([209.86.89.69] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3592761 for lml@lancaironline.net; Wed, 22 Apr 2009 09:41:01 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.69; envelope-from=douglasbrunner@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=S08rPH4zSF5+XC6W+BV4ddq41yyFbDoP+GqziOc8rSRffxoWiy80el4lHZyxuKsD; h=Received:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE:X-ELNK-Trace:X-Originating-IP; Received: from [74.93.196.177] (helo=DougsLaptop) by elasmtp-mealy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1Lwcga-0007Zm-4K for lml@lancaironline.net; Wed, 22 Apr 2009 09:40:24 -0400 X-Original-Message-ID: From: "Douglas Brunner" X-Original-To: "Lancair Mailing List" References: In-Reply-To: Subject: Re: [LML] Re: Ram Air Design X-Original-Date: Wed, 22 Apr 2009 09:40:06 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_005D_01C9C32E.51B1D290" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6001.18000 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 X-ELNK-Trace: ad85a799c4f5de37c2eb1477c196d22294f5150ab1c16ac00c3604e638927e74a1139d5be97b71c2c710c6386aa055c1350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 74.93.196.177 This is a multi-part message in MIME format. ------=_NextPart_000_005D_01C9C32E.51B1D290 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Why would the addition of the "trim rings" change the air flow? The trim rings extend further back into the engine compartment than the = original cowl inlet did. There was a minimal decrease in the diameter = of the cowl inlets. Believe me, I was surprised by the result as well. ----- Original Message -----=20 From: Gary Casey=20 To: lml@lancaironline.net=20 Sent: Wednesday, April 22, 2009 9:26 AM Subject: [LML] Re: Ram Air Design I assume because the inlet area is reduced if only slightly and more = likely that the smooth airflow is "tripped" by the sharp edges. In my = opinion, the "ram air" (quotes used deliberately) tube that is on most = Continental-engined Lancairs is the worst I have ever seen. The tubing = is large enough - probably too large, but the sharp leading edge = probably destroys any potential for pressure recovery. And with it = extending significantly into the cooling air inlet, those same sharp = edges have to reduce cooling air flow. What to do? One of my favorites = is to just put another air filter on the second inlet pipe and get rid = of the mechanisms in the inlet system - they worry me anyway, as the = small bits can come loose and go through the engine while the big pieces = can come loose and block the air flow completely. Use the higher = pressure in the upper cooling plenum to give most of the pressure = recovery that is possible - probably 75%. What do you do about an = alternate air source? Maybe nothing, as half of the filter area is = pointing backwards and won't be plugged with snow anyway. Or just = through away that pretty "filter" and put hardware cloth over the inlet. = My feelings about the effectiveness of K&N filters might be showing, I = suppose. At the very least just cut off the ram air tube and put a = bell-shaped entrance on it. Your idea of extending the inlet forward is = good, but as Grayhawk said, to be most effective it has to be away from = the hub. This is because the round propeller sections near the hub are = just obstructions to air flow. I put my chin inlet (bottom-inlet = Lycoming engine) close to the hub and it was a mistake, but I don't = think it hurts a lot. Take a look at some of the turbo 210's - they = have a separate ram air inlet on the outboard edge of the cooling inlet = and they have a rounded leading edge. But for your installation how do = you move it away? I'm not sure, but I know what I would do - use two = rectangular paper filters with a smooth transition from there to the = throttle body. Simple, works good, lasts a long time. It would lose = maybe 10% of what ram air could be obtained by heroic efforts, but a 10% = loss in ram pressure probably represents 1% in power, or 0.3% in max = speed. And the extra air filter area would probably give 1% more power = at takeoff and reduce the amount of dust by 90% compared to the K&N = solution. FWIW Gary Casey ES, Lycoming engine, paper filter from a turbo 402 Cessna. -------------------------------------------------------------------------= ----- Posted for "Douglas Brunner" : Recently, I installed two aluminum cowl inlets (see photo) in my = Legacy. I=20 did this largely for aesthetic reasons, but also expected that it = would=20 improve my ram air pressure. I was wrong - for reasons I don't = understand my=20 ram air MP is now less that my filtered air MP by a full inch. (My = ram air is=20 reversed because my plane had de-ice and the de-ice alternator is on = the left=20 side). =20 I have sketched a new ram air system that I hope will give me back at = least=20 1.5 or 2 inches of ram air. (see sketch). Features: 1.. The ram air inlet will be flush with the cowl inlet and well out = into=20 the air stream. 2.. A "flapper valve" to block the filter when not in use Your thoughts? =20 Any suggestions of who could fabricate this? =20 ------=_NextPart_000_005D_01C9C32E.51B1D290 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Why would the=20 addition of the "trim rings" change the air flow?
 
The trim rings extend further back into = the engine=20 compartment than the original cowl inlet did.  There was a = minimal=20 decrease in the diameter of the cowl inlets.  Believe me, I was = surprised=20 by the result as well.
----- Original Message -----
From:=20 Gary=20 Casey
Sent: Wednesday, April 22, 2009 = 9:26=20 AM
Subject: [LML] Re: Ram Air = Design

  I assume because the inlet area is reduced if only = slightly=20 and more likely that the smooth airflow is "tripped" by the sharp = edges.=20  In my opinion, the "ram air" (quotes used deliberately) tube = that is on=20 most Continental-engined Lancairs is the worst I have ever seen. =  The=20 tubing is large enough - probably too large, but the sharp leading = edge=20 probably destroys any potential for pressure recovery.  And with = it=20 extending significantly into the cooling air inlet, those same sharp = edges=20 have to reduce cooling air flow.  What to do?  One of my = favorites=20 is to just put another air filter on the second inlet pipe and get rid = of the=20 mechanisms in the inlet system - they worry me anyway, as the small = bits can=20 come loose and go through the engine while the big pieces can come = loose and=20 block the air flow completely.  Use the higher pressure in the = upper=20 cooling plenum to give most of the pressure recovery that is possible = -=20 probably 75%.  What do you do about an alternate air source? =  Maybe=20 nothing, as half of the filter area is pointing backwards and won't be = plugged=20 with snow anyway.  Or just through away that pretty "filter" and = put=20 hardware cloth over the inlet.  My feelings about the = effectiveness of=20 K&N filters might be showing, I suppose.  At the very least = just cut=20 off the ram air tube and put a bell-shaped entrance on it.  Your = idea of=20 extending the inlet forward is good, but as Grayhawk said, to be most=20 effective it has to be away from the hub.  This is because the = round=20 propeller sections near the hub are just obstructions to air flow. =  I put=20 my chin inlet (bottom-inlet Lycoming engine) close to the hub and it = was a=20 mistake, but I don't think it hurts a lot.  Take a look at some = of the=20 turbo 210's - they have a separate ram air inlet on the outboard edge = of the=20 cooling inlet and they have a rounded leading edge.  But for your = installation how do you move it away?  I'm not sure, but I know = what I=20 would do - use two rectangular paper filters with a smooth transition = from=20 there to the throttle body.  Simple, works good, lasts a long = time.=20  It would lose maybe 10% of what ram air could be obtained by = heroic=20 efforts, but a 10% loss in ram pressure probably represents 1% in = power, or=20 0.3% in max speed.  And the extra air filter area would probably = give 1%=20 more power at takeoff and reduce the amount of dust by 90% compared to = the=20 K&N solution.  FWIW

Gary Casey
ES, Lycoming engine, paper filter from a turbo 402 Cessna.





Posted for "Douglas = Brunner"=20 <douglasbrunner@earthlink.net>:

 Recently, I = installed two=20 aluminum cowl inlets (see photo) in my Legacy.  I
did = this=20 largely for aesthetic reasons, but also expected that it would =
improve my=20 ram air pressure.  I was wrong - for reasons I don't = understand my=20
ram air MP is now less that my filtered air MP by a full=20 inch.  (My ram air is
reversed because my plane had = de-ice and=20 the de-ice alternator is on the left
side).
 
 I = have=20 sketched a new ram air system that I hope will give me back at least =
1.5=20 or 2 inches of ram air. (see sketch).  Features:
  = 1.. The=20 ram air inlet will be flush with the cowl inlet and well out into =
the air=20 stream.
  2.. A "flapper valve" to block the filter when not = in=20 use
 Your thoughts?
 
 Any suggestions of who = could=20 fabricate this?  



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