07/02/2003

Limits of Combustion

In the 30's a gas oil engine was common.  A spark ignition engine that ran on
diesel slime.  The pump swill was around 60 octane average and guess what -
diesel swill was around 60 octane.  This meant if you could start it, you
could run it.  In research 201 looking at farm tractors will show you dozens
of manufacturers and commercial models with would start with gasoline and run
with either slime or swill.

Diesel has much lower volatility than gasoline, making it harder to start, but
ok running.  Waukeeshaw Moters made a lot of these engines for the railroad
cars to power refrigeration and air conditioners.  There secret was a fast
heating carburetor that pre-heated the fuel enough so that it mixed to
homogeneous and burned nicely.  

About the same power and weight as a pure otto, but capable of using extremely
cheap slimey fuel.  There was a heck of a demand for these - particularly in
the extremely low profit margin region of pre-wwII agriculture.

To the current date.  Diesels dirty little secret.  Lower limit of
flexibility.  Gasoline with more than about 25% excess is not flammable.  In
fact, to burn it at 25% excess air requires high compression and a special
chamber and probably at least partial charge stratification.

If you add fuel to a diesels air stream, and its well homogeneousness, as long
as it does not reach the limit of flammability - It will NOT BURN - no matter
what the compression.  When the main charge fires by injection - the entire
charge will heat extremely rapidly and the homogeneous fuel will self ignite
and burn in a long slow homogeneous charge compression ignition.  All of that
preloaded fuel will burn in the vicinity of tdc and greatly increase the
power.

Propane - for example, can handle about 60% or more excess air so would not be
able to be used in quantity - save its about 120 octane and its compression
ignition temperature is about the same as the diesel generators.  Thus, you
can pack a diesel with about 40% propane and get instant smooth power beyond
expectation.  Big arsed clue for propane - the "knock" is almost gone and it
sounds more like a monster block than a diesel - with long power pulse sounds.

Rules permitting - and I'll guarantee they don't - you could put either a
propane or diesel fuel carb in front of the turbo and pull a sub lower limit
of explosion amount of fuel and bring the power of a diesel to very close
proximity of an otto.

Clues for this will be found after research 201 under Natural Gas Engines,
where a significant number of them use diesel injectors and pilot fuel in
place of plugs.  Depending on cost - the engine can be dynamically shifted
from a preponderance of one fuel to the other.

Stationary engine research does note do one any good if they are building a
car right?

Aftermarket, I am waiting for someone to adapt a "carburetor" to an injection
diesel and match the power of a big block.  Haven't seen it yet, but if Tom
Leone is right about the forthcoming march of diesels, we'll see a lot of
history "re-invented" and sold to the public.