what's it like in there

[Tmoose]

A character on a Yahoo group insists that inside his mildly supercharged British twin the mixture is "honey thick" as TDC approaches.
His concern today is specifically in the region of the spark plug gap.

There are so many modern papers concerned with intake induced tumble and swirl persisting during compression and even during combustion I have to wonder how viscous a few hundred degree F compressed gasoline/air mixture really can be.

Am I assuming things I should not/

thanks

Dan T

 

[MikeHalloran]

I have been told that at 2000 psig, air is roughly as dense as balsa wood.
That does not speak to its viscosity.

But at ~300 psi / 300F ? Room temp honey? Hard to accept.




Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

http://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html

barely 13x increase in density

TTFN
faq731-376

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[btrueblood]

From wikipedia, honey has a dynamic viscosity around 2~10 Pa-s.

From

http://www.nist.gov/data/PDFfiles/jpcrd283.pdf‎

air at 500K and 2.5 MPa (round numbers a little higher than Mike's estimates above) has a dynamic viscosity of about 27 x 10^-6 Pa-s, or about 5 orders of magnitude less than honey. In fact, even at 100 MPa or about 14,500 psi, and 1200K, it's still only about 55 x 10^16 Pa-s.

 

[ivymike]

he doesn't by chance run alternative fuels does he? molasses perhaps?

 

[Tmoose]

Only mention of fuels is that his setup runs on US regular I think, which makes me wonder how much boost/compression/open throttle it really has/sees.

 

[dgallup]

Running on nitromethane, the A/F ratio is so low the engines come close to hydraulic locking. Nothing like that with gasoline or even alcohol.

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