Post by Gregory PoonPost by DocUnderstood, but my query right now is strictly to determine what would
be coming out the exhaust manifold, as compared to what comes out with
combusted gasoline.
The process of combustion within an ICE produces CO2 and H20 (and CO
in a lean mixture), in the presence of unused air, at a very high
temperature and pressure. At very high temperatures and pressures, N2,
CO2 and H2O undergo further interesting chemistry until the exhaust
gas temperature drops to the point where no more chemistry happens.
Depending on compression ratio, fuel/air mixing ratios (lean or rich),
spark efficiencies, and combustion temperature and other parameters,
various amounts of CO2, CO, H2O, NO, NO2, partial combustion products
(and many less important products) will be discharged at the exhaust
port.
Message: the fuel burnt is less important than the combustion
proccess, in regards to combustion products.
The scientifically inclined may wish to perform a simple experiment to
demonstrate this rule. Drop some methanol down a sink drain, followed
by a match. A little bit of subdued combustion occurs in the sink
drain. Note the extremely offensive smell of formaldehyde, CH2O, due
to the incomplete combustion of methanol.
Post by Gregory PoonComplete combustion would yield H2O and CO2 (the final products of complete
oxidation of any hydrocarbons). But burning ethanol would produce less CO2
than the same amount of gasoline.
False. Ethanol has lower fuel value than gasoline so burning an
equivalent amount of ethanol will produce more CO2 than gasoline. (See
below.)
Post by Gregory PoonIt's only a matter of time before industrial ethanol becomes economically
competitive against gasoline and we'll all be running on blends (or maybe
even neat ethanol like Brazil did!)
Industrial ethanol is made by the hydration of ethylene which is made
from ethane which is a component of natural gas. Technically, a better
use of the fuel value of natural gas is to use it directly as fuel.
Economic efficiency is tied to technical efficiency. In the absence of
technical efficiency, economic efficiency is merely a delusion.
The ethanol that is currently blended with gasoline is not industrial
ethanol, it is grain alcohol. Grain alcohol is produced by farmers who
drive huge gas guzzly farm trackers. (Technical efficiency, negative;
economic efficiency, hugely negative; profit for farmers, hugely
positive.)
Ethanol may have some economic and technical value as an antiknock
additive when blended with low octane gasoline. However, only the use
of industrial ethanol makes any economic sense for this purpose.
===> Insert usual counter-argument from 'green' lobby here.
Post by Gregory PoonPost by DocPost by Gregory PoonAlso ethanol has a burn value that is only about 75% that of gasoline,
so
Post by DocPost by Gregory Poonyou need to consume more ethanol to achieve the same effect as gasoline.