response 1 of 49:

Sep 17 22:34 UTC 2003

The crankshaft picture is pretty neat - it looks like a standard engine
diagram, then I notice the ladder-rungs going down the interior spaces, then
I notice the little tiny guys on top...

response 3 of 49:

Sep 18 04:46 UTC 2003

grassolean.com is a harder than usual site to read.
  
try:   http://www.montanagreenpower.com/   instead

response 5 of 49:

Sep 18 16:47 UTC 2003

One of Rudolph Diesel's early engines got 75% thermal efficiency (it is
claimed in the literature). Sulzer built a single-cylinder, two-stroke,
reversible (!), diesel engine with a bore of one meter, which developed
1.47 megawatts, in 1911. (Sulzer was a marine engine developer and
manufacturer. There is a history of diesel engine development at
http://members.shaw.ca/diesel-duck/library/other/prime_movers.htm,
including some pictures of these early big engines

response 7 of 49:

Sep 18 19:52 UTC 2003

Trivia: The little engines that are used on radio-controlled aircraft
are tiny two-stroke diesels.

response 9 of 49:

Sep 18 20:34 UTC 2003

No, they are carburetted two-stroke engines. The air and fuel are mixed
prior to entry into the cylinder. Diesel engines compress only air, and
inject the fuel during expansion. Compressed air intake occurs during the
latter part of the expansion stroke, when it also scavenges the exhaust
out exhaust valves.

response 11 of 49:

Sep 18 22:56 UTC 2003

How loud can these big engines get?  How far away can you feel this thing
starting up?

response 13 of 49:

Sep 19 14:05 UTC 2003

I don't think so; that'd be too complex.  I guess if you want to be
picky they're "compression ignition" engines.

response 15 of 49:

Sep 19 19:34 UTC 2003

While we're on the topic, here's a two-stroke, radial *aircraft*
turbodiesel that looks pretty neat: http://www.zoche.de/

The two-stroke offers some nice smoothness and simplicity advantages over a
four-stroke.  They're using a pneumatic starting system that sounds pretty
interesting, too.  It looks like they have 2-, 4-, and 8-cylinder versions
planned.

Engines like this are rapidly starting to look like the wave of the future
for general aviation in Europe, where avgas is hugely expensive compared to
jet fuel.  There are several companies starting to produce aircraft diesels
in various configurations.  Besides this one, I've seen pictures of
prototypes for a horizontally-opposed 4-cylinder, four-stroke, aircooled
engine and an inline 4-cylinder, four-stroke, watercooled engine.  The
latter is based on an automotive design.  Water-cooling is starting to get
some attention in aircraft applications again after being abandoned for
years.  (The standard joke was that using a watercooled engine in an
airplane made about as much sense as using an aircooled engine in a
submarine.)

response 17 of 49:

Sep 19 22:29 UTC 2003

Still, Diesel should consider himself lucky.  No one ever refers to the
regular type of spark-ignition engine as an "Otto engine".

response 19 of 49:

Sep 20 04:12 UTC 2003

Re #5:  I doubt that very much, as the entropy created by combustion
alone would limit efficiency to less than that.

Re #6:  Great page.  What the heck do they use to *crank* that thing?

response 21 of 49:

Sep 20 14:27 UTC 2003

Re #12:  No, "knock" is the ignition of the fuel-air charge
from overtemperature before the flame front reaches it.  This
happens more or less all at once, and causes a shock wave.
Knock causes large acoustic waves inside the cylinder, which
disturb the stagnation layer near surfaces and transfers a lot
more heat to them than they're designed for.  Sustained heavy
knock tends to be accompanied by things melting or otherwise
being destroyed.

"Dieselling" in a carbureted car after the ignition is turned
off is actually hot-spot ignition.  Hot-spots (heated tubes,
glow plugs) predate both spark and compression ignition IIRC.
This means that model airplane engines share kinship with the
earliest, most primitive internal combustion engines.

Re #15:  Zoche doesn't appear to have anything flying.  For a
product closer to reality, try http://www.deltahawkengines.com

Re #17:  Depends if you're in the technical end of the industry
or not.  Nomenclature matters when you're talking odd cycles;
Otto-Atkinson, anyone?

Re #0, I'm curious about the lack of modern technical refinements
in that engine.  For instance, the pistons are oil-cooled.  Why
cool them, when modern ceramic materials could reduce or eliminate
the need for cooling?  The heat not lost to the head and piston
would help drive expansion, but much of it would come out in the
exhaust.  This means that there would be a considerable excess
of power available from the turbocharger, and that excess could
be tapped to push the crankshaft harder.

If you can get 50% efficiency from the diesel section, and another
25% from the gas turbine (not unusual IIRC), that's 62.5%.  Probably
not an insignificant savings if you can get it, so why not?

Last, the engine produces 4.27 horsepower per liter.  If my SHO did
as well, its 3.2 liters would muster 13.7 horses.  I'm impressed. ;-)
(Actually, I am.  At 102 RPM it is producing 1876 joules/liter/rev.
Assuming 210 horsepower at 7000 RPM, my SHO only yields 420 J/l/rev.)

response 23 of 49:

Sep 22 06:32 UTC 2003

Re #22:

The theoretical maximum efficiency for an Otto cycle engine is

        Nth = 1 - r^( 1 - k ).

For any k > 1, including air (k == 1.4), as r increases without bounds,
Nth approaches 1. So an engine can theoretically have any efficiency
that is less than 100%. 75% thermal efficiency would require a compression
ratio of approximately 32 to 1. Normal diesel engines are typically
around 16 to 1, and a bit higher.

A 32:1 engine sounds plausible. It would be necessary to cut in half the
top-dead-center head clearance volume, increase the wall thickness and|or
the material strength by a factor of 2.639 (2^1.4), and also increase
the injector operating pressure by a factor of 2.639. The compression
temperature ratio would also increase, by a factor of 1.392 (2^0.4).

There is, however, little point to it, since this would more than double the
mass of the engine per cylinder displacement, and a 16:1 compression ratio
already affords a theoretical maximum of 67% (89% of the efficiency of the
32:1 engine).