Electric motor assisted super- or turbocharger?

Max Kallio wrote:
2-stroke diesels need compressed air for starting the engine, so the
turbo (exhaust driven centrifugal supercharger) is out of a guestion
and it produces very little boost at low rpm anyhow.

Modern large 2-stroke Diesels (EMD 710 series for example) have a
mechanical drive to the turbocharger which spins it at low power
settings and it acts as a mechanical blower. As power settings come up
and exhaust volume increases, the turbine takes over and operates the
supercharger. Much more efficient than converting mechanical power to
electrical then back to mechanical again.

Don Stauffer wrote:

Why not just have a small compressed air pump driven by gears from
crankshaft or camshaft, with a tank to store a few "starts" full of
compressed air? Seems like an easier fix than an electric driven
compressor.



People should really study up on some of the things that have been done
with turbo- and super-chargers for the past 60 years before getting
carried away. For the last 20 years, for example, virtually all EMD
locomotive engines (2-stroke diesels) have used a hybrid
mechanical/turbo supercharger. At low power settings and during
starting, a sprag (overrunning clutch) spins the turbocharger from the
engine's own gear train, just like the old Roots blowers used to be
turned. But when the power is increased, the turbine takes over and
spins the compressor faster than the engine's drive, so the overrunning
sprag releases and the turbo is fully powered by exhaust.

Proven, simple, no silly mechanical-electrical-mechanical conversions to
go through. But the 2-stroke diesel is dead anyway. Conventional
4-stroke turbo-diesels are the present (except for ever-decreasing
production of EMD 710 engines) and the future of diesel power.

wrote:

Jimmy 371 - supercharged but not likely turboed.

Actually the Jimmy 371 is a naturally aspirated engine. The piston
covers the intake opening in the cylinder wall before the exhaust valves
close. The Rootes Blower is there to improve exhaust scavenging not for
supercharging. The GMC 2 stroke cycle diesels generally are not
supercharged even though they have a Rootes Blower. If they also have a
Turbo then they are supped. I've probably missed something here. My
experience is with working on GM 2 stroke cycle diesels in power boats.

Gary Thomas

wrote:

"Max Kallio" wrote in message
om...

2-stroke diesels need compressed air for starting the engine, so the
turbo (exhaust driven centrifugal supercharger) is out of a guestion
and it produces very little boost at low rpm anyhow.


Unfortunately, I avoided the opportunity to learn about these engines. My
father ran some
3 cylinder 2 stroke diesels in earth moving equipment some years ago and was
very happy with them. I believe they were turbocharged, but am not certain.
They may have started with a pony engine but again am not certain.


Almost certainly Detroit Diesel 3-71 engines. There are millions of X-71
series engines still in use (X denotes the number of cylinders, and
there may also be a "V" in the designation: a V-12-71 denotes a V-12
with each cylinder displacing 71 cubic inches; a V-6-92 denotes a V6
with 92 cubic inch cylinders). Detroit Diesel is no longer producing any
of the 2-stroke series new, but they still support them and probably
will for another 20-30 years because there were so many built from ~1930
to ~2000.

In most earthmoving applications, the 3-71 was not turbocharged, but all
x-71 engines were supercharged with a roots blower (they won't run
without it, being 2-stroke engines). Pony engine start was common on
equipment made in the 40s and 50s, but electric start was almost
universal by the 60s, with compressed-air start being common on marine
and fixed engines.

Why is the 2 stroke diesel dead?
I know little about diesels, just the obvious, like no sparkplug.

Bob

Bob wrote:

Why is the 2 stroke diesel dead?
I know little about diesels, just the obvious, like no sparkplug.

Bob


High emissions and lower fuel efficiency compared with competitive
4-stroke diesels

In order to get emissions down, a 2-stroke diesel engine has to be
"overblown" so that an excess of fresh air is pushed through the
cylinder to drive out the exhaust gasses fully, but doing that wastes
mechanical power. So solving the emissions problem aggravates the
efficiency problem and vice-versa. And also, 2-stroke diesels have a
lot higher lubricating oil consumption rate than similar 4-strokes, and
that aggravates emissions too.

The EMD 710 is the only remaining locomotive 2-stroke, and is being
phased out by the EMD 4-stroke "H-series" engine. Detroit Diesel was the
biggest maker of 2-strokes for trucks, earthmovers, yachts, etc. and
they stopped 2-stroke production several years ago. And its been over 20
years since many 18-wheelers used Detroit 2-strokes anyway.
Fairbanks-Morse still builds their opposed-piston 2-strokes for a few
Navy applications and for stationary applications (flood control pumps,
backup generators, etc.) and will probably continue to do so, but that's
a pretty small market segment.

Since 2 NGs are aviation related, that is one area where the 2-stroke
*might* hang on longer because of its weight savings, but its ultimately
probably doomed there also.

Steve wrote in :

Bob wrote:

Why is the 2 stroke diesel dead?
I know little about diesels, just the obvious, like no sparkplug.

Bob


High emissions and lower fuel efficiency compared with competitive
4-stroke diesels

In order to get emissions down, a 2-stroke diesel engine has to be
"overblown" so that an excess of fresh air is pushed through the
cylinder to drive out the exhaust gasses fully, but doing that wastes
mechanical power. So solving the emissions problem aggravates the
efficiency problem and vice-versa. And also, 2-stroke diesels have a
lot higher lubricating oil consumption rate than similar 4-strokes, and
that aggravates emissions too.

The EMD 710 is the only remaining locomotive 2-stroke, and is being
phased out by the EMD 4-stroke "H-series" engine. Detroit Diesel was
the
biggest maker of 2-strokes for trucks, earthmovers, yachts, etc. and
they stopped 2-stroke production several years ago. And its been over
20
years since many 18-wheelers used Detroit 2-strokes anyway.
Fairbanks-Morse still builds their opposed-piston 2-strokes for a few
Navy applications and for stationary applications (flood control pumps,
backup generators, etc.) and will probably continue to do so, but
that's
a pretty small market segment.

Since 2 NGs are aviation related, that is one area where the 2-stroke
*might* hang on longer because of its weight savings, but its
ultimately
probably doomed there also.



exspecially since they are testing at least one rotary diesel, very much
lighter and quieter for unmaned small reconasinst planes. KB
--
ThunderSnake #9 Warn once, shoot twice
460 in the pkup, 460 on the stand for another pkup
and one in the shed for a fun project to yet be decided on