On Mon, 14 Apr 2008 14:30:48 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
.. .
On Mon, 14 Apr 2008 00:48:23 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
...
On Sun, 13 Apr 2008 19:04:55 -0400, "Ed Huntress"
wrote:



More to do with the actual fuel composition than the actual octane
rating, wouldn't you agree?

No, they're talking about octane ratings, and you'll find the same
pattern
for gasoline and other high-octane fuels versus diesel fuel, throughout
the
literature. The issue here is the differences in performance relative to
different octane rating systems.


You will admit, will you not, that propane, ethanol, and leaded racing
fuel will have 3 very widely varying burn speeds, very different
flamability ranges, extremely differing autoignition specs, widely
disparate energy densities,just as widely disparate specific gravities
and reid vapour pressures, yet very close to the same octane?

I have no idea. Where's the data?

You want data - THAT I can give you.(Except for burn speed)

snip

I'm not sure what you're getting at here, but we've already discussed the
fact that RON and MON octane ratings don't necessarily correlate with
autoignition. The octane value for that is OI, the octane index.

The quote from which this discussion started was one that indicated that
resistance to autoignition correlates with octane rating -- and it
specifically was talking about OI. Here's the introduction from that same
abstract, which I didn't include for the sake of brevity (and also because
we'd already discussed the fact that it was OI, not RON or MON ratings, that
was being discussed):


And octane has NOTHING to do with autoignition stage one (which is
lighting the fuel in a CI engine.Otherwise deisel fuel would also have
an octane rating, like gasoline has a cetane rating.
It is only related to stage 2( if I understand the stages correctly)
autoignition in a spark ignition or homogenous mixture engine where
SOME of the fuel autoignites in an explosive manner (detonates)

ANd a HCCI engine is TECHNICALLY not a diesel cycle engine.
================================================= ====
"A homogeneous charge compression ignition (HCCI) engine has been run at
different operating conditions with fuels of different RON and MON and
different chemistries. The ignition quality of the fuel at a given operating
conditions is characterized by CA50, the crank angle at which the cumulative
heat released reaches 50% of the maximum value for the cycle. It is found
that CA50 might show no correlation with either RON or MON but correlates
very well with the Octane Index, OI defined as OI \me (1-K)RON + KMON \me
RON - KS, where K is a constant depending on the engine operating condition
and S is the fuel sensitivity, (RON MON). The higher the OI, the more the
resistance to autoignition and the later is the heat release in the HCCI
engine at a given condition."
================================================= ====

Here's a related description:

================================================= ====
(Octane Appetite Studies in Direct Injection Spark Ignition (Disi) Engines -
2005)

"The anti-knock or octane quality of a fuel depends on the fuel composition
as well as on the engine design and operating conditions. The true octane
quality of practical fuels is defined by the Octane Index, OI \me (1-K)RON +
KMON where K is a constant for a given operating condition..."
================================================= ====

snip

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