Boat Forum / Building / December 2006

Fuel efficiency?  Who wants fuel efficiency? Most people will never
thimk about fool efficiency.

The first demonstration Diesel engine built burned biodiesel -peanut
oil.

During the industrial revolution, the triple expansion steam engine
revolutionized steam power. Double the power or more for the same fuel.
Why do we not see triple or even double expansion internal combustion
gas generation engines, with efficient, fully combusted, cool exhaust,
filtered and deacidified?

If engines used water injected to increase the second fuel charge
expansion by steam generation, they would possibly contribute to
replacing the evaporative part of the ecological water cycle lost to
deforestation of paved areas. The exhausted water might well fizz,
containing some of the CO2 cast off in today's engines, so the water
might well concentrate acid if recycled.  If this unavoidably corroded
engines, it could be cast off to decompose the ground nearby, entombing
the CO2 thought to be so harmful to the air. If the roadway contained
limestone, the acid would be neutralised, as it would if the engine's
water recycler contained consumable limestone / calcium sand.

The hot exhaust from the primary / combustion cylinder would go into
the expansion stroke of the larger secondary cylinder, and with water
injected into the hot gas turning to 1700 times the volume of water
vapor, and metered so that when the secondary exhaust valve opened, the
pressure drop cooling effect would condense the water, scavenging the
heat lost to single expansion engines and discharging cool, wet
exhaust. The water might be recyclable in a blown air cooled muffler /
condenser / filter.  Such an engine would need no catalytic converter.
Close control and timing might well cushion the bottom of the secondary
expansion piston's cycle if the water vapor condensed just before
bottom dead centre and the opening of the secondary exhaust valve. The
secondary cylinder would have no compression phase, it's exhaust valve
open to allow the repositioning of the secondary piston to top dead
center and aspiration.  The primary cylinder exhaust valve closes,  hot
water is injected into the secondary exhaust cylinder, evaporates,
expands, and helps drive the secondary piston down. It may be that the
secondary cylinder needs no intake valve, relying only on the exhaust
valves of the primary and secondary cylinders for it's aspiration.

The secondary cylinder would be larger than the primary and the
expansion ratio would be different from the primary compression ratio,
being calibrated against timing and water expansion parameters. A
computer would control water injection.

"Modern" i.c. engines lose much of the fuel energy in hot exhaust and
water cooled blocks, let alone incompletely combusted CO gas.  This
energy, if recovered,  might save 50% or more of the energy lost, about
33% increase in efficiency.

I cannot see why the same principal would not work in a diesel ignition
engine.

Such an "internal steam engine" could reduce the consumption and price
of fuel. I guess that's why we haven't heard of it.

One difficulty is that an otto cycle (four stroke) only produces
exhaust every second revolution, so the secondary expansion cylinder
might want to be geared 1:2, or it's valve(s) timed to acommodate that
fact, or with an intermediate pressure vessel between the cylinders.
It's exhaust valve would close every second revolution, timed to the
exhaust of the primary exhaust stroke.  A two stroke engine would not
need such complication, but it's secondary piston crank angle would be
offset so as to lengthen the primary power stroke to a full 1/2
revolution power / expansion stroke, as opposed to the common 1/4
revolution power stroke.

Another huge saving in fuel efficiency could be promoted at home, a
reversible air conditioner / heater might get used more to heat than to
cool over the course of a year, saving considerable heating fuel cost,
if mainly only during the spring and fall..  Why have we not heard of
it?

Terry K