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#1
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Electric motor assisted super- or turbocharger?
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. How about supplementing a centrifugal turbocharger with a high speed electric motor to create boost needed for starting and to enhance boost at low rpm? This would pretty much eliminate the turbo lag and actually help suck the exhaust out of the cylinder at low rpm. When the rpm rises, the electric motor could disengage or perhaps even work as an auxilary generator. Also, if the turbo has some problems, the electric motor could be used at full power to help the turbo to spin and create boost at least for the time it takes to land safely. Of course, the engine should be able to have enough power to stay airborne at least at low altitudes (if the load is not exeeded) even when the turbo fails completely. Links... www.turbodyne.com |
#2
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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. 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. How about supplementing a centrifugal turbocharger with a high speed electric motor to create boost needed for starting and to enhance boost at low rpm? This would pretty much eliminate the turbo lag and actually help suck the exhaust out of the cylinder at low rpm. When the rpm rises, the electric motor could disengage or perhaps even work as an auxilary generator. Also, if the turbo has some problems, the electric motor could be used at full power to help the turbo to spin and create boost at least for the time it takes to land safely. Of course, the engine should be able to have enough power to stay airborne at least at low altitudes (if the load is not exeeded) even when the turbo fails completely. Links... www.turbodyne.com |
#3
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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. |
#4
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Why is the 2 stroke diesel dead?
I know little about diesels, just the obvious, like no sparkplug. Bob |
#5
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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. |
#6
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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 |
#7
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"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. Can you fill me in on the details? |
#8
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#9
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The DeltaHawk uses both an electrically driven supercharger for starting and
low-rpm operation, plus a turbocharger for the usual stuff. "Max Kallio" wrote in message om... How about supplementing a centrifugal turbocharger with a high speed electric motor to create boost needed for starting and to enhance boost at low rpm? |
#10
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Nope, the Deltahawk uses a traditional Roots belt-driven blower for
starting and low-rpm operation. |
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