[Vwdiesel] More Power From Insulation (Science Again)

[Shirley, Mark R]

Mark I, I did not know you were schooled in engineering..  
Yes, it was I who posted about the SAE papers on this subject.  I have read
every paper on this subject up to about 2000.  The general consensus was, that
TBC's do not show appreciable increase in specific output, and this mostly due
to a net loss in VE because of intake charge heating.  Those of you into the
racing scene may be aware of a fellow named Dave Williams in Arkansas, who 
put a fully TBC coated 4 cylinder gas engine together a while ago.  He noted
some strange things:  Power nearly same as non-TBC'd engine, total insensitivity
to timing advance, and no heat from the heater.  On a diesel engine that already
has a difficult time producing enough waste heat to run a heater core, it might
not make sense to do this to an engine that will spend significant time in 
northern climates.

As I stated on several other forums, TBC's make sense only from a durability standpoint,
where engine longevity is of paramount concern.  IE, you have an engine that
is stressed beyond it's normal operating parameters, and you use the TBC's to crutch 
it.


> -----Original Message-----
> From: Mark Shepherd [mailto:mark at shepher.fsnet.co.uk]
> Sent: Sunday, February 13, 2005 8:39 PM
> To: vwdiesel at vwfans.com
> Subject: [Vwdiesel] More Power From Insulation (Science Again)
> 
> 
> Ok it's not the weekend (for me now) but this science thread
> is not entirely OT
> A few weeks ago I queried whether we could 'insulate' the
> piston face and ignition chamber to reduce some of the 30%
> energy losses to the coolant.
> Loren kindly pointed me to a site that provides coatings for
> engine chambers.
> But quite frankly I was disappointed with what their site
> was showing in terms of enhances in performance. The % gains
> (if any) were minimal. I found the graphs very superficial
> and didn't show thickness of coating etc and was only done
> for one engine. The graph on the retail is different to the
> one in 'bulk' and has silly errors.
> I surmise that if the chamber area is 'insulated'
> sufficiently then one could arguably start the diesel
> without glowplugs as the temp rise without losses by
> compression is of the order of 1000 deg F.
>  I aim to show that chamber heat losses can be reduced to a
> significantly with a thin barrier film.
> The following is some mathematics that I have run through to
> see the predicted effects:
> Aluminium has a thermal conductivity of 230ish W/mC  (The
> units are a little confusing because its W/(m x m) @1m
> thickness. Different books write it differently [not to
> mention BTU's CHU's Calories etc]. Oops )
> Now most ceramics are of the order of 0.5W/mC
> 
> Thus using 'ball park' estimates.
> Losses through piston face might be 230/0.01m is 23,000W per
> 1sq m of piston face and 1 deg C temp gradient.
> If we were to coat the face to 1mm thickness with a ceramic.
> 0.5/0.001 or 500W.
> Adding inverses (which is equivalent to adding capacitances
> in series) we get 489W/mC
> This shows that heat losses can be reduced 46 fold through a
> 10 mm ally wall.
> If we settle for a 1/ 20 and we know that the bulk of the 30
> % energy loss of an engine, into the coolant is via the head
> and piston face; (hence the bountiful water cooling in the
> head and the oil squirters aiming at the pistons).
>  The power gains (or fuel economy increase) ought to be
> significant.
> Of the 30% or so heat losses down the exhaust how much do we
> claw back via the turbo?
> These figures tumbling round my head makes me wonder why the
> improvements shown by the industrial coatings company are
> somewhat pathetic. Was it Mark Shirley who mentioned SAE
> papers not showing much gain.Can we have more info?
> Mark-The-Miser-UK
> 
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