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2-stroke diesel is the (near) future?



 
 
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  #21  
Old May 13th 05, 04:52 PM
Steve
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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.


  #22  
Old May 13th 05, 05:40 PM
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"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.


  #24  
Old May 13th 05, 06:13 PM
Sport Pilot
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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.

  #25  
Old May 13th 05, 06:17 PM
Sport Pilot
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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.

  #26  
Old May 13th 05, 08:51 PM
Richard Isakson
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"Sport Pilot" wrote ...

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


Isn't able to complete a sentence either?

Rich


  #27  
Old May 13th 05, 09:23 PM
Sport Pilot
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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.

  #28  
Old May 13th 05, 11:17 PM
Steve
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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.


  #30  
Old May 13th 05, 11:39 PM
Morgans
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"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

 




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