2-stroke diesel is the (near) future?

Yea me two! 90% spelling accuracy on Usenet is what should be
acepted without comment! My opinion.

Sport Pilot wrote:
>
>
> A compression ignition engine is not always a Diesel engine. Not sure
> if Mr. Diesel invented comprssion ignition, but they used to be common
> for model aircraft. Though called Diesel's modelers are often reminded
> they are not really Diesel's.
>

Good point. I think Rudy did indeed invent compression ignition. And
the old Ford Proco engine designs were virtually Diesel cycle engines
even though they had spark ignition. In fact, that idea seemed like a
really good one to me, and I would like to know why it never went
anywhere. Was the injection system just to complicated for production?

Walt K. wrote:
> actually, the model (glo-plug) engines are *NOT* Diesel, nor are they
> compression ignition... they closely resemble hot-bulb ignition, since
> the platinum wire in the glo-plug does remain red-hot during engine
> operation...
>
> Sport Pilot wrote:
>
>>
>>
>> A compression ignition engine is not always a Diesel engine. Not sure
>> if Mr. Diesel invented comprssion ignition, but they used to be common
>> for model aircraft. Though called Diesel's modelers are often reminded
>> they are not really Diesel's.
>>
No, Sport Pilot had it right. There are BOTH glow plug and Diesel model
airplane engines (actually, there are also si gas engines). The Diesel
ones do NOT have a glowplug, and run on Diesel fuel. It used to be so
strange to see a guy carrying his engine back to pits, flipping the prop
and hearing the engine sputter and cough and run a few seconds. The glow
engines needed a starting battery.

These engines are, nor never were, all that popular, but they have been
around for half a century. In fact, there is one company that makes
modified heads to convert a number of models of glow engine into "Diesel".

Smitty wrote:
> In article .com>,
> "Sport Pilot" > wrote:
>
> > HELLO! It's just the friggin usenet! Most of us don't even know
who
> > we are talking too. Some of us have more important things to do,
such
> > as correspondance on a 10 million dollor project. You bet that
baby
> > gets proofread, spell checked, grammer checked, proofread, maybe
ask a
> > co worker to proofread it, see what I missed, etc.
>
> Hello? You mean "to," (a preposition and therefore a word with which
you
> ought not end a sentence, anyway) "correspondence," "dollar," and
> "grammar?" I'm not picking on you, particularly, but the pervasive
> ignorance of spelling, grammar, punctuation, homonyms, sentence
> construction, ad infinitum, makes me ****ing sick. And it isn't just
> usenet, it's everywhere, even in your ten million dollar report,
because
> your computer can't fix everything and your coworkers are as
apathetic
> as you are. We're becoming a nation of ignorant idiots. I think
that's a
> bad thing, and a dangerous one. If we knew as little about airplanes
as
> we did the English language, and flew them as carelessly as we write,

> we'd all be dead by now.


Ass I said I really don't care. In fact your anger only make sme want
to make mroe miostakes. So i have not coreected any typos at all in
this one.

>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.

Thought I had responded to this before, but cannot find it.

There IS a fundamental reason diesels do not turn as many revolutions
as a gas engine. Injecting the fuel throught most of the expansion
cycle prevents speed, but does give a constant push. You could shorten
the injection so that the end of the injection is closer to TDC, but
then it would be more of an otto cycle. If you put too much fuel at or
near TDC then you would have the same problem as an otto engine with
high compression and low octane fuel. Diesel fuel is not high octane.

Luke Scharf > writes:

> Steve wrote:
> > 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.
>
>
> When I was reading about the Volkswagen TDI engine, I vaguely remember
> coming across someone who said that the redline of that engine was set
> by the speed which which the burning fuel expanded.

My '01 180 bhp Audi 2.5 tdi V6 has a redline of 4500 rpm.

>
>
> Sounds rather fundamental to me - but, then again, I'm a computer guy.
>
> -Luke

Thomas

Don Stauffer > writes:

> Sport Pilot wrote:
> > 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.
> >
>
>
> True, but even 2500 rpm is a high speed Diesel. When we speak of low
> speed Diesels, those are like the big ship and stationary engines that
> run maybe 800 rpm max.
>

I once had the opportunity to visit the engine room of one of the big
ferries cruising between Sweden and Finland. It had four engines and
two props.

The idle speed was 100 rpm and full speed was 150 rpm.

I could not hear any difference between 100 and 150 rpms. But then I
never knew what noise came from the propulsion engines. There were a
lot of other helper engines making a lot of noise.

The props were geared 2:1, so they did 75 rpms at full speed.

Thomas

Thomas Tornblom wrote:
> Luke Scharf > writes:
>
>
>>Steve wrote:
>>
>>>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.
>>
>>
>>When I was reading about the Volkswagen TDI engine, I vaguely remember
>>coming across someone who said that the redline of that engine was set
>>by the speed which which the burning fuel expanded.
>
>
> My '01 180 bhp Audi 2.5 tdi V6 has a redline of 4500 rpm.

That's about where the one on the Jetta was -- right around 4500 rpm.
The displacement on the Jetta is only 1.6 liters, though... I wonder
what dimensions are similar to make the smaller engine redline at the
same speed?

When I got to the redline, the engine seemed to politely refuse to go
any faster. Not like the screaming tantrum I'm used to from my
run-of-the-mill gas engines as I open the throttle.

I dig diesels. :-)

-Luke

Morgans wrote:

> "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.


The blower also takes away a significant chunk of crankshaft power. The
blower has to do the same net work as those "non power" strokes in a
4-cycle diesel because its doing the same job- expelling burnt mixture
and bringing in fresh air. You can't get something for nothing.

This is all old-hat. 2-stroke diesels have been in widespread use since
Winton developed the basic foundation for what became both the EMD and
Detroit Diesel 2-stroke engine architecture back in the 1920s. 2-strokes
became very simple to service and reliable, but they rarely won on
either fuel efficiency or total power output per unit weight. That's why
you find 2-strokes in locomotives and ships where weight doesn't matter
(or is a benefit), but they all but disappeared from on-road
applications by the end of the 1970s and DID completely disappear by the
turn of the century.

Luke Scharf wrote:

> Steve wrote:
>
>> 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.
>
>
> When I was reading about the Volkswagen TDI engine, I vaguely remember
> coming across someone who said that the redline of that engine was set
> by the speed which which the burning fuel expanded.
>
> Sounds rather fundamental to me - but, then again, I'm a computer guy.
>
> -Luke

In almost ALL real-world engines, the actual limit is set by the point
at which some mechanical component would fail. The engine's torque *may*
drop off well before the mechanical failure point if it can't ingest
enough fuel or air at high speed. In the case of a diesel, you can
pretty much increase the burn rate to as high as the mechanical parts
can tolerate by increasing turbocharger boost (and injection rate to
match). Since detonation isn't possible (no fuel exists in the cylinder
until combustion is supposed to begin anyway) the only limits to boost
pressure are mechanical in nature. In practical terms, no one really
wants or needs a 9000 RPM diesel, though.