2-stroke diesel is the (near) future?

On Wed, 25 May 2005 09:37:53 -0500, Don Stauffer
> wrote:

wrote:
>
>>
>> One BIG factor is being forgotten here. The diesel is turboed. This
>> makes it roughly equivalent to an 8 liter engine at about 6psi boost.
>> Any combustion engine produces power in proportion to the amount of
>> air consumed. On a diesel it does not necessarily "consume" all the
>> air that goes through it - but the maximum power output is definitely
>> limitted by how much air can be put through it. A turbo can eisily
>> double the amount of air an engine pumps through it at a given speed.
>>
>> Running an engine at double the speed also increases the amount of air
>> going through the engine - not quite double due to reduced volumetric
>> efficiency at speed.
>>
>> Double the CFM gives double the horsepower, before factoring in
>> frictional losses and / or pumping losses.
>>
>> A naturally aspirated diesel engine generally produces less HP per
>> unit of displacement, but more torque at low RPMs due in part to less
>> pumping loss (no air throttle)
>>
>SOME diesels are turboed. Many are not. Some Diesels are normally
>aspirated. Some are supercharged with geared chargers. Some are
>turboed. It is by far an overgeneralization to claim that all Diesels
>are supercharged, even more so to say they are all turbo-supercharged.


The post being replied to was comparing a turbo cummins to a gas
engine.

Nobody ever said all diesels are turboed.

Morgans wrote:

> "Steve" > wrote
>
>
>>I believe that if you look at modern diesels currently being produced
>>and sold, you'll find virtually NONE rated at more than 50-60 horsepower
>>that are not turbo-supercharged. And equally few that are strictly
>>mechanically blown (the Detroit Diesel 2-strokes are no longer in
>>production). The VAST majority are, indeed, turbo-supercharged.
>
>
> Not true of some of our school busses that were produced in the past 5 or so
> years. They make up for the lack of super or turbocharging with more cubic
> inches.

I say AGAIN... what percentage of the market is that? Tiny. And they
only TRY to make up with more cubic inches- a DT466E would run rings
around them.

"Steve" > wrote

> I say AGAIN... what percentage of the market is that? Tiny. And they
> only TRY to make up with more cubic inches- a DT466E would run rings
> around them.

I was not taking issue with the tiny percentage concept. I did take issue
with the following, and the NONE

>>I believe that if you look at modern diesels currently being produced
>>and sold, you'll find virtually NONE rated at more than 50-60 horsepower
>>that are not turbo-supercharged.

Not a big deal to me, one way or the other. I always found the non turbo
buses under powered, compared to their turbo brothers.
--
Jim in NC

mastic 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.
>
> Wrong. Mr Otto invented the four stroke cycle and it is named after
> him. The fuel or when it's introduced has nothing to do with it, Otto
> refers to the cycle.

SO? He didn't mention fuel in the part you snipped. Diesel is a
differant cycle named after Mr. Diesel.

mastic wrote:
>>1. Desiel injection timing is differant than on an Otto engine. The
>>fuel is injected during the intake cycle on the Otto engine and the
>>fuel is injected during the ignition cycle on the Desiel.
>
>
> An Otto engine is any four stroke engine, diesel, gasoline, LPG makes
> no difference.


And there is no "ignition" stroke. BTW, it is not ignition, or intake,
or combustion "cycle". There is only one cycle in either a four stroke
cycle or two stroke cycle engine. What is different is the number of
strokes in a cycle. Cycle means repeating operation. A two-stroke
cycle engine repeats its operation every two strokes, a four-stroke
repeats every four strokes.

I believe if we must shorten the terms then four-stroke and two-stroke
are better terms, because in both cases we are talking about what
happens in one cycle, not in two or four CYCLEs.

Sport Pilot wrote:
>
> mastic 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.
>>
>>Wrong. Mr Otto invented the four stroke cycle and it is named after
>>him. The fuel or when it's introduced has nothing to do with it, Otto
>>refers to the cycle.
>
>
> SO? He didn't mention fuel in the part you snipped. Diesel is a
> differant cycle named after Mr. Diesel.
>

Actually, today's Diesels can operate over several cycle types. Modern
high speed Diesels as used in cars are closer to the Otto cycle than
they are to Rudolph's cycle. In his original engine the fuel was
supposed to be injected at a rate to create a constant combustion
temperature or a constant pressure. This really would take a feedback
of temperature or pressure during the combustion stroke, and was- and
is- extremely hard to do. The slower the speed of the engine, the
better current Diesels approach the intended Diesel cycle, as seen on an
indicator diagram. The indicator diagram on high rpm Diesel auto
engines look a lot like the diagram of an Otto cycle.

There are people developing Diesel systems using closed loop pressure
sensing to adjust fuel injection rate, but to my knowledge no Diesel car
or truck engine using this feature has ever made it to production.
Current production Diesels use open loop injection, so it is a hybrid
cycle, somewhere between true Otto and true theoretical Diesel.

mastic wrote:
> "MJC" > wrote:
>
> >
> >"Andrew P." > wrote in message
> link.net...
> >> Wandering aimlessly about the Web, I heard Sport Pilot say:
> >> > You have most of it right. Some things you have wrong,
> >> >
> >> > 1. Desiel injection timing is differant than on an Otto engine. The
> >> > fuel is injected during the intake cycle on the Otto engine and the
> >> > fuel is injected during the ignition cycle on the Desiel. On the
> >> > Desiel the fuel injection cycle starts just before TDC and ends well
> >> > after TDC. The fuel ignites as soon as it hits the hot air.
> >> >
> >> etc., etc. --- SNIP ---
> >>
> >> It's Diesel, not "Desiel".
> >>
> >> --
> >> Andrew P.
> >
> >Well if you're going to get picky, it's "Auto" engine, not "Otto" engine.
> >
> >MJC
> >
> Picky, picky, picky. It's not an Otto engine as such. Otto is used to
> refer to the standard four stroke cycle because Otto was good enough
> to invent the four stroke cycle.
> So our friend was incorrect when he said:
>
> >1. Desiel injection timing is differant than on an Otto engine. The
> >fuel is injected during the intake cycle on the Otto engine and the
> >fuel is injected during the ignition cycle on the Desiel.
>
> An Otto engine is any four stroke engine, diesel, gasoline, LPG makes
> no difference.

Completely wrong, the Otto cycle has nothing to do with four stroke
engines. Don is right its not four cycle, I used it incorrectly. The
Otto and Diesel cycles are actually refering to the thermodynamics
chart of temperature pressure and volume, they invented their cycles on
paper and books, the engines we use are only close approximations. The
two stroke ignition engine uses the Otto cycle as it is has the four
phases of intake, compression, power, and exhaust, and the pressure is
not constant. The Diesel two stroke is a Diesel cycle because it also
includes the same phases and the fuel burns at a fairly constant
pressure.

Here is an animated link showing the differances of the Otto and Diesel
cycles.

http://www.ulb.ac.be/sma/testcenter/...osedcycle.html

Notice the near instant burning in the example gives very nearly a
constant volume, in actual practice some compression is going on at
this time.

Also during a Diesel cycle it is hard to maintain a constant pressure,
it would actually drop off, especially near the end of the down stroke.

Sport Pilot wrote:
>
> Completely wrong, the Otto cycle has nothing to do with four stroke
> engines. Don is right its not four cycle, I used it incorrectly. The
> Otto and Diesel cycles are actually refering to the thermodynamics
> chart of temperature pressure and volume, they invented their cycles on
> paper and books, the engines we use are only close approximations. The
> two stroke ignition engine uses the Otto cycle as it is has the four
> phases of intake, compression, power, and exhaust, and the pressure is
> not constant. The Diesel two stroke is a Diesel cycle because it also
> includes the same phases and the fuel burns at a fairly constant
> pressure.
>

I guess I'd quibble with the statement that the Otto cycle has nothing
to do with four-stroke engines- it was the first successful cycle to
incorporate four strokes. yes, there are other four stroke cycles, but
the Otto cycle is still by far the most common. There have been several
other four-strokes, several two-strokes, at least on six stroke- I
suspect several also.

New IC engine designs are among the most numerous US patents. Just
because something is patentable, of course, does not make it good or
successful, and most of these patents were for approaches that offered
insufficient advantages.

BTW, as I understand the new Miller cycle, I don't consider it a truly
new cycle- just a clever mod on the Otto. I don't consider the Otto
cycle to require valve openings at closings at the top or bottom dead
center, exactly.

Don Stauffer wrote:
> Sport Pilot wrote:
> >
> > Completely wrong, the Otto cycle has nothing to do with four stroke
> > engines. Don is right its not four cycle, I used it incorrectly. The
> > Otto and Diesel cycles are actually refering to the thermodynamics
> > chart of temperature pressure and volume, they invented their cycles on
> > paper and books, the engines we use are only close approximations. The
> > two stroke ignition engine uses the Otto cycle as it is has the four
> > phases of intake, compression, power, and exhaust, and the pressure is
> > not constant. The Diesel two stroke is a Diesel cycle because it also
> > includes the same phases and the fuel burns at a fairly constant
> > pressure.
> >
>
> I guess I'd quibble with the statement that the Otto cycle has nothing
> to do with four-stroke engines- it was the first successful cycle to
> incorporate four strokes. yes, there are other four stroke cycles, but
> the Otto cycle is still by far the most common. There have been several
> other four-strokes, several two-strokes, at least on six stroke- I
> suspect several also.
>
> New IC engine designs are among the most numerous US patents. Just
> because something is patentable, of course, does not make it good or
> successful, and most of these patents were for approaches that offered
> insufficient advantages.
>
> BTW, as I understand the new Miller cycle, I don't consider it a truly
> new cycle- just a clever mod on the Otto. I don't consider the Otto
> cycle to require valve openings at closings at the top or bottom dead
> center, exactly.

The confusion is that Otto invented the first four stroke engine and
called it the Otto cycle, not because of thermodynamics but because he
put it in a motorcycle. However the thermodynamic cycle can be
reproduced with a two stroke engine. Its just that the intake and
exhaust cycle's are much shorter.