[Gasification] combustion math question (help needed)

[jim mason]

i have a math question i need worked out in regards answering the potential
efficiency (usability) of syngas related fuels in IC engines.  hopefully
someone here can help.

in figuring out the potential for reasonable operation of H2 and CO gaseous
fuels in a spark ignition IC engine, we need to allow for the higher
compression ratios that CO and H2 fuels will support.  diesel engines are
more efficient than gas engines bascially from the higher compression
ratios.  well, that and the lack of air throttling losses too.

when comparing the auto ignition temps of gasoline with CO and H2, clearly
much higher compression ratios are possible, thus higher efficiencies, which
can compensate for the reduced energy density of the biomass derived syngas.
  adding a turbo or the like to syngas engines to increase compression to
just short of the detonation compression should do much for efficiency.  but
how much i am unsure.  (and sadly i am also unsure of the math).

some data on auto ignition temps of common fuels (or how high the
compression can get before the fuel with detonate in a premixed air/fuel IC
situation, like a gasoline spark ignition engine).  most are here:
http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html

gasoline: 232C
octane: 206C
diesel: 210C
methane (nat gas): 537C
propane: 458C
ethanol: 363C
methanol: 464C
CO: 609C
H2: 500C

the question then is how high of theoretical compression can a premixed,
spark ignition engine run with each fuel before detonation will occur?  of
course this is a non-linear problem with all sorts of complicating factors,
but how does one figure the ideal case, isothermic scenario?

and the related question, what is the usual increase in effiency gain per x
multiple increase in compression ratio?

once the max theoretical compression ra
tio is somewhat known, we can figure the theroetical max power from the HHV
or LHV of the fuel at x rpm.  some common values at HHV

gasoline:

C + O2 = C02 + 393 KJ/MOL
CO + 1/2 O2 = CO2 + 283 KJ/MOL
H2 + 1/2O2 = 285 KJ/MOL (241kj/mol without H20 condensation)
CH4 + 202 = CO2 + 2H20 + 890 KJ/MOL

other values are findable here;
http://en.wikipedia.org/wiki/Heating_value
http://en.wikipedia.org/wiki/Higher_heating_value
http://www.google.com/search?q=lower+heating+value+gasoline&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

i realize this is a rather large question.  apologies ahead of time for such
a doozie.  nonetheless, any tutoring help with the math here is much
appreciated.

jim




-- 
--------------------------------------------------------------------------------
jim mason
website: www.whatiamupto.com
current project: mechabolic (http://www.mechabolic.org)
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