[Gasification] Burning velocity

[Kevin Chisholm]

Dear Chuck

I have a problem with "burning velocity" also. :-)

A gasoline engine with a 4" stroke, running at 3600 RPM, does 60 revolutions 
per second. It thus takes 1/120 of a second for the piston to travel TDC to 
BDC. This is an average piston speed of 40 feet per second. 300 CM/Second is 
3 meters per second, or basically 10 feet per second. This is 1/4 of the 
piston speed

With "super fast hydrogen", the above numbers would suggest that it was only 
1/4 burned if it was ignited at TDC. Even if it was ignited at the start of 
the compression stroke (the equivalent to 180 degrees of spark advance), it 
would still only be 1/2 burned at the bottom of the power stroke (180 
degrees after TDC)

We all know that IC engines with 4" strokes can work at 3600 rpm, but the 
above "flame speed analysis" says they can't.

Could someone please tell me what I am missing here?

Thanks!!

Kevin
----- Original Message ----- 
From: "Charles Coronella" <coronella at unr.edu>
To: <gasification at listserv.repp.org>
Cc: <rich_bain at nrel.gov>; "Ralph Overend" <ralph_overend at nrel.gov>
Sent: Wednesday, May 10, 2006 1:41 PM
Subject: [Gasification] Burning velocity


Tom,

I don't understand why it might be useful to characterize the burning
velocity of a fuel gas.  I presume the burning velocity is a function of the
inherent homogeneous oxidation reaction kinetics.  But the rate of
combustion of fuel gases is typically limited by mass transfer
considerations, isn't it?  And that will vary greatly depending upon
combustor configuration, especially rapid mixing of fuel and oxidant.

As an academic researcher, I'm interested in identifying useful needs for
the community, but, who's going to fund it?  (US-DOE? yeah, right...)

Chuck Coronella

Date: Wed, 10 May 2006 07:04:16 -0600
> From: Thomas Reed <tombreed at comcast.net>
>
>
> BUT:  It is relatively easy to make from all other fuels which are easy
> to store and ship.  It has a high burning velocity and can burn very
> lean or very rich.  And it has very low emissions compared to all other
> fuels.
>
> The burning velocity of most fuels in air is 40-60 cm/sec.  The burning
> velocity of hydrogen is 300 cm/sec.  The burning velocity of really pure
> CO is 30 cm/sec, but a small amount of impurity makes it comparable to
> all other fuels.  So, "hydrogen rich gas" burns faster than most fuels
> with a wider combustion limit.
>
> I wish that some laboratory would undertake the task of defining the
> flame velocity and combustion limits of hydrogen rich gas.  I have one
> Dutch paper from the 1950s in my archives giving a linear dependence on
> CO-H2 content up to 300 cm/sec and some combustion limits, but we need
> more than that.
>
> Any volunteers?
>
> Yours truly,
>
> TOM REED       THE BIOMASS ENERGY FOUNDATION
>
>
>
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