2-stroke diesel is the (near) future?

Steve wrote:
> Sport Pilot wrote:
>
>
> > Diesel fuel is not conducive to high speed running. Nor is a long
> > injection period through much of the expansion phase. Yes you can
> > boost the turbocharger and the other things, but an Otto cycle
engine
> > will respond with even higher speeds. Parts failure from speed is
not
> > a problem with diesel engines, the rotating parts have to be bigger
> > than an otto engine because of the higher compression, yet the otto
> > engine will turn higer RPM's with smaller parts.
> >
>
>
> All of the above is true in the common practice of diesel design, but

> none of it is necessarily true. There is nothing FUNDAMENTAL that
limits
> a diesel to low-RPM designs only. One can build a screaming high-RPM
> diesel with light-weight rotating parts, but one would have to ask
> "why?" Gasoline engines are made high-revving in order to increase
power
> output from a small package, but diesels can develop a lot more
low-RPM
> torque through high boost because they don't detonate when "lugged,"
so
> there's no NEED to make them scream. If you need more power, don't
spin
> them faster, just boost them harder. High RPM is an aggravation, not
an
> advantage (no matter what Honda VTEC drivers think...).


Actually diesels don't really deliver that much torque at similar
speeds. Ok they do but only because the valving is timed for the
slower speeds. Many gasoline tractor engines will diliver similar
torque, but with a higher fuel consumption due to the lower compression
ratio. Diesel fuel burns slower and will knock when the injection
timing is shortened to allow higher speeds.

Sport Pilot wrote:

> Steve wrote:
>
>>Sport Pilot wrote:
>>
>>
>>
>>>Diesel fuel is not conducive to high speed running. Nor is a long
>>>injection period through much of the expansion phase. Yes you can
>>>boost the turbocharger and the other things, but an Otto cycle
>
> engine
>
>>>will respond with even higher speeds. Parts failure from speed is
>
> not
>
>>>a problem with diesel engines, the rotating parts have to be bigger
>>>than an otto engine because of the higher compression, yet the otto
>>>engine will turn higer RPM's with smaller parts.
>>>
>>
>>
>>All of the above is true in the common practice of diesel design, but
>
>
>>none of it is necessarily true. There is nothing FUNDAMENTAL that
>
> limits
>
>>a diesel to low-RPM designs only. One can build a screaming high-RPM
>>diesel with light-weight rotating parts, but one would have to ask
>>"why?" Gasoline engines are made high-revving in order to increase
>
> power
>
>>output from a small package, but diesels can develop a lot more
>
> low-RPM
>
>>torque through high boost because they don't detonate when "lugged,"
>
> so
>
>>there's no NEED to make them scream. If you need more power, don't
>
> spin
>
>>them faster, just boost them harder. High RPM is an aggravation, not
>
> an
>
>>advantage (no matter what Honda VTEC drivers think...).
>
>
>
> Actually diesels don't really deliver that much torque at similar
> speeds. Ok they do but only because the valving is timed for the
> slower speeds. Many gasoline tractor engines will diliver similar
> torque, but with a higher fuel consumption due to the lower compression
> ratio.

It depends on what you're comparing to. A lot of tractors use
normally-aspirated indirect-injection diesels, which are no comparison
to a turbocharged diesel. Or to a good normally-asipirated gasoline
engine, except in terms of longevity. Gasoline engines are hard to beat
for the *width* of their torque curve, but modern turbo-diesels do a
good job against them, and do so with better efficiency.

> Diesel fuel burns slower and will knock when the injection
> timing is shortened to allow higher speeds.
>

Higher speed requires more than just rapid injection, it also demands
higher boost pressure, which causes the fuel to burn faster without any
knock-like phenomenon. All serious diesels are turbocharged for that
reason (as well as others), and normally-aspirated diesels are limited
to very small power outputs and relatively low efficiency. You can only
get so much combustion chamber pressure through the compression ratio of
the engine- the rest has to come from forced induction. As someone
pointed out earlier, the VW TDI develops power up to 4500 RPM, which is
comparable to many gasoline engines, but it is able to do so only
because it is a turbo-diesel. As I said before, there's no reason that
building a 7000-RPM diesel isn't possible, but there's no REASON to
build one.

"Steve" > wrote

In practical terms, no one really
> wants or needs a 9000 RPM diesel, though.

Oh, I don't know. NASCAR might be interested in going diesel ! <g>
--
Jim in NC

Steve wrote:
>
> 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.

Actually, detonation can and does occur in Diesels. With today's Diesel
fuels and injection methods the fuel does not burn INSTANTLY upon
injection. The droplets are too large. The droplets tend to evaporate
from their surface area. It IS possible for unburned gases evaporated
from the fuel to exist in the chamber and detonate in local regions. The
effect is nowhere as severe as the detonation that occurs in spark
engines at times. Interesting traces made with high frequency pressure
sensors indicate these local "peaks" in combustion pressure when this
occurs. It is the cause of the "tinkling" sound that Diesels
occasionally make.

Detonation is not a full or nothing situation. Local regions can
undergo detonation even while the majority of the charge undergoes
normal wavefront burning, in either Diesel or SI.

Steve wrote:
> Sport Pilot wrote:
>
>
>> Diesel fuel is not conducive to high speed running. Nor is a long
>> injection period through much of the expansion phase. Yes you can
>> boost the turbocharger and the other things, but an Otto cycle engine
>> will respond with even higher speeds. Parts failure from speed is not
>> a problem with diesel engines, the rotating parts have to be bigger
>> than an otto engine because of the higher compression, yet the otto
>> engine will turn higer RPM's with smaller parts.
>>
>
>
> All of the above is true in the common practice of diesel design, but
> none of it is necessarily true. There is nothing FUNDAMENTAL that limits
> a diesel to low-RPM designs only. One can build a screaming high-RPM
> diesel with light-weight rotating parts, but one would have to ask
> "why?" Gasoline engines are made high-revving in order to increase power
> output from a small package, but diesels can develop a lot more low-RPM
> torque through high boost because they don't detonate when "lugged," so
> there's no NEED to make them scream. If you need more power, don't spin
> them faster, just boost them harder. High RPM is an aggravation, not an
> advantage (no matter what Honda VTEC drivers think...).
>
I would assume that use of hydrogen as a fuel would allow very high rpm
in a Diesel.

Don Stauffer wrote:

> Steve wrote:
>
>> Sport Pilot wrote:
>>
>>
>>> Diesel fuel is not conducive to high speed running. Nor is a long
>>> injection period through much of the expansion phase. Yes you can
>>> boost the turbocharger and the other things, but an Otto cycle engine
>>> will respond with even higher speeds. Parts failure from speed is not
>>> a problem with diesel engines, the rotating parts have to be bigger
>>> than an otto engine because of the higher compression, yet the otto
>>> engine will turn higer RPM's with smaller parts.
>>>
>>
>>
>> All of the above is true in the common practice of diesel design, but
>> none of it is necessarily true. There is nothing FUNDAMENTAL that
>> limits a diesel to low-RPM designs only. One can build a screaming
>> high-RPM diesel with light-weight rotating parts, but one would have
>> to ask "why?" Gasoline engines are made high-revving in order to
>> increase power output from a small package, but diesels can develop a
>> lot more low-RPM torque through high boost because they don't detonate
>> when "lugged," so there's no NEED to make them scream. If you need
>> more power, don't spin them faster, just boost them harder. High RPM
>> is an aggravation, not an advantage (no matter what Honda VTEC drivers
>> think...).
>>
> I would assume that use of hydrogen as a fuel would allow very high rpm
> in a Diesel.

But no one has come up with a completely satisfactory way to do direct
injection with a gaseous fuel, which is the same problem diesels that
run on natural gas face.

NG diesels are interesting beasts. They actually mix the gas with the
intake air and compress it like a spark-ignition engine would, setting
up the possibility of detonation, but since NG is has a very high
relative "octane" rating, it doesn't ignite until a *tiny* shot of
diesel is injected to initiate combustion. They do have to operate at
somewhat lower compression than a straight diesel, but its still in the
neighborhood of 14:1 or 15:1 which is much higher than you can achieve
with gasoline, at least on any fuel short of leaded aviation racing fuel
that is brewed up in ridiculously small (and expensive) quantities for
the Reno air racers.

The OTHER Kevin in San Diego wrote:
> On Mon, 16 May 2005 15:08:37 -0500, Steve > wrote:
>
>
>>High RPM is an aggravation, not an
>>advantage (no matter what Honda VTEC drivers think...).
>
>
> Shhhh.. Don't tell the guys at Pratt & Whitney that...

It depends... gas generator shafts need to spin fast, but the LP spool
on a PW4000 doesn't turn any faster than the engine in my car

We own a 2003 Jetta TDI and it poops out before it gets to 4500. However, it
goes uphill at 80mph gaining speed at around 2500RPM. BTW. Hp= Torque X
RPM. If your 100hp engine peaks at 2500 rpm and your 200horse engine peaks
at 7500 rpm, the 100hp engine has to develop 1.5 times more torque than your
200hp engine at the peak hp rpm.

--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478
(760) 408-9747 general and layout cell
(760) 608-1299 technical and advertising cell

www.vkss.com
www.experimentalhelo.com


"Steve" > wrote in message
...
> Sport Pilot wrote:
>
> > Steve wrote:
> >
> >>Sport Pilot wrote:
> >>
> >>
> >>
> >>>Diesel fuel is not conducive to high speed running. Nor is a long
> >>>injection period through much of the expansion phase. Yes you can
> >>>boost the turbocharger and the other things, but an Otto cycle
> >
> > engine
> >
> >>>will respond with even higher speeds. Parts failure from speed is
> >
> > not
> >
> >>>a problem with diesel engines, the rotating parts have to be bigger
> >>>than an otto engine because of the higher compression, yet the otto
> >>>engine will turn higer RPM's with smaller parts.
> >>>
> >>
> >>
> >>All of the above is true in the common practice of diesel design, but
> >
> >
> >>none of it is necessarily true. There is nothing FUNDAMENTAL that
> >
> > limits
> >
> >>a diesel to low-RPM designs only. One can build a screaming high-RPM
> >>diesel with light-weight rotating parts, but one would have to ask
> >>"why?" Gasoline engines are made high-revving in order to increase
> >
> > power
> >
> >>output from a small package, but diesels can develop a lot more
> >
> > low-RPM
> >
> >>torque through high boost because they don't detonate when "lugged,"
> >
> > so
> >
> >>there's no NEED to make them scream. If you need more power, don't
> >
> > spin
> >
> >>them faster, just boost them harder. High RPM is an aggravation, not
> >
> > an
> >
> >>advantage (no matter what Honda VTEC drivers think...).
> >
> >
> >
> > Actually diesels don't really deliver that much torque at similar
> > speeds. Ok they do but only because the valving is timed for the
> > slower speeds. Many gasoline tractor engines will diliver similar
> > torque, but with a higher fuel consumption due to the lower compression
> > ratio.
>
> It depends on what you're comparing to. A lot of tractors use
> normally-aspirated indirect-injection diesels, which are no comparison
> to a turbocharged diesel. Or to a good normally-asipirated gasoline
> engine, except in terms of longevity. Gasoline engines are hard to beat
> for the *width* of their torque curve, but modern turbo-diesels do a
> good job against them, and do so with better efficiency.
>
> > Diesel fuel burns slower and will knock when the injection
> > timing is shortened to allow higher speeds.
> >
>
> Higher speed requires more than just rapid injection, it also demands
> higher boost pressure, which causes the fuel to burn faster without any
> knock-like phenomenon. All serious diesels are turbocharged for that
> reason (as well as others), and normally-aspirated diesels are limited
> to very small power outputs and relatively low efficiency. You can only
> get so much combustion chamber pressure through the compression ratio of
> the engine- the rest has to come from forced induction. As someone
> pointed out earlier, the VW TDI develops power up to 4500 RPM, which is
> comparable to many gasoline engines, but it is able to do so only
> because it is a turbo-diesel. As I said before, there's no reason that
> building a 7000-RPM diesel isn't possible, but there's no REASON to
> build one.

Stuart & Kathryn Fields wrote:
> We own a 2003 Jetta TDI and it poops out before it gets to 4500.
However, it
> goes uphill at 80mph gaining speed at around 2500RPM. BTW. Hp=
Torque X
> RPM. If your 100hp engine peaks at 2500 rpm and your 200horse engine
peaks
> at 7500 rpm, the 100hp engine has to develop 1.5 times more torque
than your
> 200hp engine at the peak hp rpm.
>
> --
> Stuart Fields
> Experimental Helo magazine
> P. O. Box 1585
> Inyokern, CA 93527
> (760) 377-4478
> (760) 408-9747 general and layout cell
> (760) 608-1299 technical and advertising cell
>
> www.vkss.com
> www.experimentalhelo.com
>
>
> "Steve" > wrote in message
> ...
> > Sport Pilot wrote:
> >
> > > Steve wrote:
> > >
> > >>Sport Pilot wrote:
> > >>
> > >>
> > >>
> > >>>Diesel fuel is not conducive to high speed running. Nor is a
long
> > >>>injection period through much of the expansion phase. Yes you
can
> > >>>boost the turbocharger and the other things, but an Otto cycle
> > >
> > > engine
> > >
> > >>>will respond with even higher speeds. Parts failure from speed
is
> > >
> > > not
> > >
> > >>>a problem with diesel engines, the rotating parts have to be
bigger
> > >>>than an otto engine because of the higher compression, yet the
otto
> > >>>engine will turn higer RPM's with smaller parts.
> > >>>
> > >>
> > >>
> > >>All of the above is true in the common practice of diesel design,
but
> > >
> > >
> > >>none of it is necessarily true. There is nothing FUNDAMENTAL that
> > >
> > > limits
> > >
> > >>a diesel to low-RPM designs only. One can build a screaming
high-RPM
> > >>diesel with light-weight rotating parts, but one would have to
ask
> > >>"why?" Gasoline engines are made high-revving in order to
increase
> > >
> > > power
> > >
> > >>output from a small package, but diesels can develop a lot more
> > >
> > > low-RPM
> > >
> > >>torque through high boost because they don't detonate when
"lugged,"
> > >
> > > so
> > >
> > >>there's no NEED to make them scream. If you need more power,
don't
> > >
> > > spin
> > >
> > >>them faster, just boost them harder. High RPM is an aggravation,
not
> > >
> > > an
> > >
> > >>advantage (no matter what Honda VTEC drivers think...).
> > >
> > >
> > >
> > > Actually diesels don't really deliver that much torque at similar
> > > speeds. Ok they do but only because the valving is timed for the
> > > slower speeds. Many gasoline tractor engines will diliver
similar
> > > torque, but with a higher fuel consumption due to the lower
compression
> > > ratio.
> >
> > It depends on what you're comparing to. A lot of tractors use
> > normally-aspirated indirect-injection diesels, which are no
comparison
> > to a turbocharged diesel. Or to a good normally-asipirated gasoline
> > engine, except in terms of longevity. Gasoline engines are hard to
beat
> > for the *width* of their torque curve, but modern turbo-diesels do
a
> > good job against them, and do so with better efficiency.
> >
> > > Diesel fuel burns slower and will knock when the injection
> > > timing is shortened to allow higher speeds.
> > >
> >
> > Higher speed requires more than just rapid injection, it also
demands
> > higher boost pressure, which causes the fuel to burn faster without
any
> > knock-like phenomenon. All serious diesels are turbocharged for
that
> > reason (as well as others), and normally-aspirated diesels are
limited
> > to very small power outputs and relatively low efficiency. You can
only
> > get so much combustion chamber pressure through the compression
ratio of
> > the engine- the rest has to come from forced induction. As someone
> > pointed out earlier, the VW TDI develops power up to 4500 RPM,
which is
> > comparable to many gasoline engines, but it is able to do so only
> > because it is a turbo-diesel. As I said before, there's no reason
that
> > building a 7000-RPM diesel isn't possible, but there's no REASON to
> > build one.

I think most of us know that torque is only a force and you need speed
(RPM) to develop power. More speed is more power. Or was there some
other point you are trying to make?

Sport Pilot wrote:

> I think most of us know that torque is only a force and you need speed
> (RPM) to develop power. More speed is more power. Or was there some
> other point you are trying to make?
>


II think the point is that there are TWO ways that do an equally good
job of increasing power. More TORQUE is more power too.

Since power=K*Torque*RPM, the result is that if you hold the speed
constant and double the torque, you get double the power. There are
diesel engines in this world that develop 20,000 horespower at only 150
RPM. Naturally, the torque value is astronomical. No, they don't fly.
;-) They swim.