X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 50 [XX] (67%) RECEIVED: IP not found on home country list (33%) RECEIVED: Received headers not consistent with Yahoo! "FROM:" Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 30 Mar 2007 10:46:23 -0400 Message-ID: X-Original-Return-Path: Received: from web34907.mail.mud.yahoo.com ([209.191.68.186] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with SMTP id 1951766 for lml@lancaironline.net; Fri, 30 Mar 2007 06:48:24 -0400 Received-SPF: none receiver=logan.com; client-ip=209.191.68.186; envelope-from=n103md@yahoo.com Received: (qmail 29759 invoked by uid 60001); 30 Mar 2007 10:47:33 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:Date:From:Subject:To:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-ID; b=Ag7hCPr+hJIDv+4KMz+uucXOs4p7GEK81m9BCzdyYJ46JBdeLNEJtGRFzRaKalmhdYG1KDz+xpJkhi4iyjSakpdsBxnyOnDR/V7exMUth1h1TLzdlhLYjI4lNRZrd/zbumLxnv8x1cYzTX9M3Zspnrig8JcLLtPpZBwxkQCnKTc=; X-YMail-OSG: .k4WQR8VM1krg6RFYUjElAek.kbkRu.3.mKNYdL6AmdEnPB.WUSSM6qclNKd323QvYLhTQPBhPimZnkO4vSY97CakQg41C.co1LW5JrNo3WtSspGo9NA_GhsyQ-- Received: from [202.57.156.14] by web34907.mail.mud.yahoo.com via HTTP; Fri, 30 Mar 2007 03:47:33 PDT X-Original-Date: Fri, 30 Mar 2007 03:47:33 -0700 (PDT) From: bob mackey Subject: RE: [LML] Thielert Diesel Centurion 4.0 X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-41280107-1175251653=:25859" Content-Transfer-Encoding: 8bit X-Original-Message-ID: <85839.25859.qm@web34907.mail.mud.yahoo.com> --0-41280107-1175251653=:25859 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit George says: > OK… but that means that the bulk internal combustion gas temperatures are a lot higher. > > And that means that you get a LOT more BTU’s transferred into the cylinder head. > > And, as everybody with some diesel experience is aware - - they tend - - as a > result to use rather large radiators. > > Because that heat has to be dissipated - - - some way. > There is an assumption in here that is worth questioning. Heat transfer rates from the combustion gases to the piston and cylinder do indeed increase with gas pressure and temperature *difference* between the gas and surface. The solution to the problem is simple... increase the temperature of the surface to match that of the gases. How to do that? Thermally insulate the surface. That's the idea behind ceramic coatings for the piston crown, combustion chamber, and valve faces. The insulator needs to be able to run hot on one side, and cool enough on the other side to 1) not melt or weaken the metal 2) not burn or polymerize the oil 3) not transfer so much heat that the benefits of high compression are lost to cooling drag. If that is worked out, then engine BSFC improves, and cooling losses are reduced. Just as in a gas turbine, the cooling drag is minimized by allowing the hot section to actually run hot. High temperature, high strength alloys, and insulating ceramics are the key to an efficient aircraft diesel engine. FWIW, Aluminum is just about the worst material to use in a diesel head: low strength at high temperatures, high thermal conductivity, poor fatigue life, etc. The argument that "...heat has to be dissipated - - - some way." really boils down to "because we let the heat get into the aluminum, we need to get it back out before the piston melts." --------------------------------- Bored stiff? Loosen up... Download and play hundreds of games for free on Yahoo! Games. --0-41280107-1175251653=:25859 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: 8bit
George says:
 
> OK… but that means that the bulk internal combustion gas temperatures are a lot higher.
>
> And that means that you get a LOT more BTU’s transferred into the cylinder head.
>
> And, as everybody with some diesel experience is aware - - they tend - - as a
> result to use rather large radiators.
>
> Because that heat  has to be dissipated - - - some way.
>
 
There is an assumption in here that is worth questioning.
Heat transfer rates from the combustion gases to the piston and cylinder
do indeed increase with gas pressure and temperature *difference* between
the gas and surface. The solution to the problem is simple... increase the
temperature of the surface to match that of the gases.
 
How to do that?
 
Thermally insulate the surface.
 
That's the idea behind ceramic coatings for the piston crown, combustion chamber,
and valve faces. The insulator needs to be able to run hot on one side, and cool
enough on the other side to
1) not melt or weaken the metal
2) not burn or polymerize the oil
3) not transfer so much heat that the benefits of high compression are
   lost to cooling drag.
If that is worked out, then engine BSFC improves, and cooling losses
are reduced.
 
Just as in a gas turbine, the cooling drag is minimized by allowing the
hot section to actually run hot. High temperature, high strength alloys, and
insulating ceramics are the key to an efficient aircraft diesel engine.
FWIW, Aluminum is just about the worst material to use in a diesel head:
low strength at high temperatures, high thermal conductivity, poor fatigue life, etc.
The argument that "...heat  has to be dissipated - - - some way." really boils
down to "because we let the heat get into the aluminum, we need to get it
back out before the piston melts."
 
 

Bored stiff? Loosen up...
Download and play hundreds of games for free on Yahoo! Games. --0-41280107-1175251653=:25859--