2-stroke diesel is the (near) future?

Don Stauffer wrote:

> Don Stauffer wrote:
>
>>>
>> A 4-stroke diesel is still an Otto engine. An Otto cycle engine is
>> one with four strokes, intake, compression, power, and exhaust.
>> Doesn't care whether SI or CI.
>
>
> Whoops
>
> Before everyone jumps on me, I left off an important qualification. I
> was specifically talking about cars, airplanes and highway trucks. Large
> Diesels, (stationary, large ship, etc) do run a different cycle- the
> true Diesel cycle.
>
> However, even the true Diesel cycle of larger engines is not the true
> cycle Diesel really wanted. He couldn't develop the true cycle he
> wanted (constant enthalpy), and a large Diesel comes somewhat close. A
> high speed (vehicle) engine doesn't even come close with even today's
> technology. It is pretty close to an Otto cycle, though still not
> exactly. Otto cycle has infinitesmal fraction of cycle for ignition and
> burn, while even a high speed Diesel (and even the SI engine) still
> ignites and burns over a finite angle of crank rotation. Still, the
> result, as I say is MUCH closer to Otto than the cycle Rudy had
> intended. Still makes a good engine, however :-)

I pretty much agree, although today's high-speed diesels are doing a lot
better at approchin the constant-enthalpy cycle than they used to,
thanks to being able to divorce the injection profile from crankshaft
position via electronically-controlled injection systems.

"Steve" > wrote in message
...

> I pretty much agree, although today's high-speed diesels are doing a lot
> better at approchin the constant-enthalpy cycle than they used to,
> thanks to being able to divorce the injection profile from crankshaft
> position via electronically-controlled injection systems.

Now that you mentioned it, what sort of rpm ranges are the high speed
diesels capable of?

You may remember that some years ago (just after the Arabs shut off the oil)
AVCO showed
a rather smallish (V8?) diesel that you could swap into just about any
American car of the time.
Cost was about $5000, estimated.

They claimed some rather high RPM capabilities for this engine.

Don Stauffer wrote:
> Bryan Martin wrote:
> > Not so. In the Otto cycle, the fuel and air are introduced to the
cylinder
> > during the intake stroke. In the Diesel cycle only the air is
introduce to
> > the cylinder during the intake stroke, the fuel in injected at the
end of
> > the compression stroke.
> >
> > in article , Don Stauffer at
> > wrote on 5/13/05 10:47 AM:
> >
> >
> >>A 4-stroke diesel is still an Otto engine. An Otto cycle engine is
one
> >>with four strokes, intake, compression, power, and exhaust.
Doesn't
> >>care whether SI or CI.
> >
> >
> >
> >
> In terms of the thermodynamics the fuel is immaterial. It is only a
> source of heat for raising temp and pressure. The AIR is the true
> Carnot working fluid with either a CI or SI engine. In an indicator
> diagram of the SI engine, one would be hard pressed to see the
> difference even if fuel were shut off during the induction stroke.
>
> The reason a Diesel is not a true (though close) Otto cycle is that
in
> the true Otto cycle the burning is instantaneous (or at least an
> infinitesmal number of degrees of crank rotation or percentage piston

> motion.

The Diesel is not an Otto cycle it is a completly differant cycle. The
Diesel is a constant pressure cycle where the presure is constant
through the expansion phase.

karel wrote:
> "Sport Pilot" > wrote in message
> oups.com...
> > Sooo. I oftern transpose letters, I don't proofread something as
> > triavil as usenet messages.
>
> If you consider your messages trivial, why post them?
> Anyway, I won't see them anymore. Ploink!

Only a fool assumes that someone who has trouble spelling or
pronuciation.

Don Stauffer wrote:
> Don Stauffer wrote:
> >>
> > A 4-stroke diesel is still an Otto engine. An Otto cycle engine is
one
> > with four strokes, intake, compression, power, and exhaust.
Doesn't
> > care whether SI or CI.
>
> Whoops
>
> Before everyone jumps on me, I left off an important qualification.
I
> was specifically talking about cars, airplanes and highway trucks.
> Large Diesels, (stationary, large ship, etc) do run a different
cycle-
> the true Diesel cycle.
>
> However, even the true Diesel cycle of larger engines is not the true

> cycle Diesel really wanted. He couldn't develop the true cycle he
> wanted (constant enthalpy), and a large Diesel comes somewhat close.
A
> high speed (vehicle) engine doesn't even come close with even today's

> technology. It is pretty close to an Otto cycle, though still not
> exactly. Otto cycle has infinitesmal fraction of cycle for ignition
and
> burn, while even a high speed Diesel (and even the SI engine) still
> ignites and burns over a finite angle of crank rotation. Still, the
> result, as I say is MUCH closer to Otto than the cycle Rudy had
> intended. Still makes a good engine, however :-)


You can only get so much speed when you inject the fuel through the
combustion or expansion cycle. High speed diesels get more speed by
injecting more of the fuel early. But an aircraft engine doesn't need
to turn more than 2500 RPM so we should be able to get the benifit of
the longer burn time.

"Sport Pilot" wrote ...
>
> Only a fool assumes that someone who has trouble spelling or
> pronuciation.
>

Isn't able to complete a sentence either?

Rich

Got cut off some how.

Actually I thought I had decided not to send it, and came back and some
how hit the enter key.

Sport Pilot wrote:
> karel wrote:
>
>>"Sport Pilot" > wrote in message
groups.com...
>>
>>>Sooo. I oftern transpose letters, I don't proofread something as
>>>triavil as usenet messages.
>>
>>If you consider your messages trivial, why post them?
>>Anyway, I won't see them anymore. Ploink!
>
>
> Only a fool assumes that someone who has trouble spelling or
> pronuciation.


......... what? I'm waiting for the rest. And its "pronuNciation."

Its one thing to have the occasional typo, but typing a constant run-on
of misspelled and non-punctuated text just screams "I'm a moron!" to the
world.

wrote:

> "Steve" > wrote in message
> ...
>
>
>>I pretty much agree, although today's high-speed diesels are doing a lot
>>better at approchin the constant-enthalpy cycle than they used to,
>>thanks to being able to divorce the injection profile from crankshaft
>>position via electronically-controlled injection systems.
>
>
> Now that you mentioned it, what sort of rpm ranges are the high speed
> diesels capable of?

Well, a "high speed" diesel in the usual sense is anything that turns
more than 1500-2000 RPM. So 18-wheeler diesels (Cummins N-14, DD Series
60, etc) are considered "high speed diesels" and locomotive engines are
'medium speed." Low-speed diesels are those direct-drive 3-story tall
ship engines that turn 120 RPM max and put out 25,000 horsepower.

But there are more and more small diesels that run just as fast as
gasoline engines. There's no fundamental limit thats any different than
a gasoline engine, really, but up until now there's not been a demand
for high-RPM diesels.

"Steve" > wrote

> As already stated, 2-stroke diesels really don't have a power-to-weight
> advantage over 4-strokes. They still have to have a camshaft and
> exhaust valves (they aren't like weed whacker engines, you know), so
> they don't save that weight. Plus they have to have a blower for
> scavenge air. The only area where they save weight is in that the
> connecting rod and crank can be lighter, and that only helps offset the
> added weight of the blower.

How about the fact that they have power pulses in each revolution? They
could possibly have half the displacement, and still get the same power, (or
close to it) with less weight than the double displacement 4 cycle. Yes,
the blower weight is added, but it is nice to make good power, way up there.
--
Jim in NC