What's the difference?
Thanks to Chris / CopCarSS for my avatar.
Norris, for turbo, the turbine is spun by gasses coming out of the cylinders at high temp and somewhat high pressure, so it is located somewhere in the exhaust manifold. The turbine drives another fan on the other end of the shaft that forces air into the intake manifold. Improves breathing.
For supercharger the fan is driven off the cam shaft, usually by a series of belts or chains. Same effect...the fan part forces more air into the piston side of the intake manifold from where the fan is spinning.
Did I respond as if I took your question too literally? Sorry if I did.
-Crandell
Why wouldn't a diesel engine builder go for supercharging over turbo charging staright away? Is the energy from the exhaust considered *free* energy?
Now there you have me. In each case, at my level of knowledge and understanding, there is a hp requirement, so whatever work you want done, and design it to do, will cost that much shaft hp. I don't know that it makes much difference whether you take the hp from the crank or from the exhaust gasses, except I would bet that the former is more "energetic" since it is direct....the crank spins quickly on acceleration, and the supercharger must spin up with it in concert. The turbo lags, and some of the gasses must bypass it. If you put a bigger turbo disk in there, will it blow more air at the other end...or will you just confound the exhaust pressure waves and create backpressures that are deleterious? I really don't know, but I suspect as much.
I'll shut up....someone else is sure to know.
P.S. - Norris, I do know that radial aircraft engines from The Big Exercise had both superchargers and PRT's (power recovery turbines) in the cases of the Double Wasp configuration and anything that came later (not exactly sure of my terms here, but you will know what I mean).
All EMDs are Supercharged to improve scavenging of the cylinders with them being a 2 stroke Design. Alco right off the bat with their 244 had a Turbocharger on them. Their 539 switcher was not however in the S series and in the Rs-1 switchers. EMD did not come out with a Turbocharged design until UP forced them to with the Omaha designed GP 20. GE always had a Turbo on them.
BLW Lima and Hamilton IIRC went the Supercharger route. Fairbanks Morse had a Turbo on them. You also need to remember this it takes ALOT of exhaust flow to spin a turbo up to speed to get the pressure needed to boost the HP these engines produce. That is why EMD went with a clutch driven Turbo below a certain RPM it behaves like a Supercharger above that it is a Turbo. However on the non-turbo models aka the Switchers and the GP-38's what they have on them is a standard Roots style Supercharger doing its normal job.
selector P.S. - Norris, I do know that radial aircraft engines from The Big Exercise had both superchargers and PRT's (power recovery turbines) in the cases of the Double Wasp configuration and anything that came later (not exactly sure of my terms here, but you will know what I mean).
creepycrank- Thanks for the explanation. Can you explain *scavenging* air a bit more please?
selectorNow there you have me. In each case, at my level of knowledge and understanding, there is a hp requirement, so whatever work you want done, and design it to do, will cost that much shaft hp. I don't know that it makes much difference whether you take the hp from the crank or from the exhaust gasses, except I would bet that the former is more "energetic" since it is direct....the crank spins quickly on acceleration, and the supercharger must spin up with it in concert. The turbo lags, and some of the gasses must bypass it. If you put a bigger turbo disk in there, will it blow more air at the other end...or will you just confound the exhaust pressure waves and create backpressures that are deleterious? I really don't know, but I suspect as much.
Hugh McInness (spelling?) wrote a nice book on turbochargers some 30 years ago - though technology has advanced since then, the basic concepts still apply.
First off, the pressure in the cylinder as the exhaust valve(s) opens is typically greater than twice ambient.. As such, it forms a sonic flow, where the flow rate is relatively independent of back pressure, so a mild increase in back pressure due to the exhaust turbine is not going to affect the engines performance - i.e. it is pretty much free energy.
To give an idea of how much power can be recovered from an exhaust turbine, the Wright Turbo-Compound engines of the 1950's typically got 30% more power for the same fuel consumption as the non-compound engines.
- Erik
The Wright Turbo Compound radials were also maintenance-intensive, which goes a long way in explaining why DC-6's lasted in service longer than DC-7's and Super Constellations (my personal favorite).
Scavenging (on a two-stroke diesel) is the process of blowing out the exhaust gases after combustion and replacing them with fresh air for the next power stroke.
edbentonFairbanks Morse had a Turbo on them
Are you sure?
All the FM locomotive applications I'm aware of were blower engines.
The FM engine was an opposed piston. I can't think of how you could have a four stroke OP engine.
On any two stroke, you need a blower to provide scavanging air. There just isn't enough oomph in the exhaust stream at low load and speed to do the job. You can do blower + turbo ala the Detroit 149, but a turbo alone won't do.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
edbenton not sure what you are referring to with your comment about ALCO. ALCO began experiments using the Buchi supercharging system on its 531 engine in the early 1930s. ALCO started turbocharging with Dr. Buchi's turbocharger in 1937. Turbochargers were first used on HH900 and later HH1000 switchers. Engines used were the 531T, 538T, and finally the 539T in 1940. ALCO experimented with the turbocharged 241 engine which led to development of the 244 engine. This is all covered in Steinbrenner's book. BTW the Dr. Buchi's turbocharger was manufactured for ALCO by the Elliott Manufacturing Company of Jeannette, Pennsylvania starting in 1940.
edbenton Alco right off the bat with their 244 had a Turbocharger on them. Their 539 switcher was not however in the S series and in the Rs-1 switchers.
Alco right off the bat with their 244 had a Turbocharger on them. Their 539 switcher was not however in the S series and in the Rs-1 switchers.
oltmanndThe FM engine was an opposed piston. I can't think of how you could have a four stroke OP engine.
Sleeve valves???
An article on FM's published in Trains sometime in the mid-60's specifically stated that no OP's in locomotive service were turbocharged.
If you could ask the UP right now if they would take turbo's off the old 40s to make more 38's you would be thrown out the door for suggesting such a thing. There is a virtual fight going on to trade old geep38's for older geep 40/39's. The reason; Fire prevention. Poorly maintained turbo units do not throw NEAR as much oil out the stack (unless your on a C45AC) as poorly maintained blower equipped units. the only maintance item on a EMD turbo is the soakback pump and filter. I've seen 4 fail in 10 years. not much of a problem. Blowers on the other hand are VERY finicky; they seem to have a life of about 5 years before the seals and bearings start leaking oil right into airbox. blowers are much cheaper to change than a 20K for a turbo and 7K for a clutch pack. vs 12K for a blower. but when you change them every 5 years and there are 2 per unit the savings just aren't there.
Tugboat TonyIf you could ask the UP right now if they would take turbo's off the old 40s to make more 38's you would be thrown out the door for suggesting such a thing. There is a virtual fight going on to trade old geep38's for older geep 40/39's. The reason; Fire prevention. Poorly maintained turbo units do not throw NEAR as much oil out the stack (unless your on a C45AC) as poorly maintained blower equipped units. the only maintance item on a EMD turbo is the soakback pump and filter. I've seen 4 fail in 10 years. not much of a problem. Blowers on the other hand are VERY finicky; they seem to have a life of about 5 years before the seals and bearings start leaking oil right into airbox. blowers are much cheaper to change than a 20K for a turbo and 7K for a clutch pack. vs 12K for a blower. but when you change them every 5 years and there are 2 per unit the savings just aren't there.
Sounds like it might be a good idea for UP to upgrade some 38-2s to GP22ECOs. It would give them better fuel economy, Tier 2 emissions, fewer power assemblies, and eliminate Roots blowers.
While not RR related as already brought up, the PRT on a R3350 radial engine 3 prts fed by 6 cylinders each adding 150hp each which is free hp. Always wandered why big engine builders haven`t tried this.
poneykegWhile not RR related as already brought up, the PRT on a R3350 radial engine 3 prts fed by 6 cylinders each adding 150hp each which is free hp. Always wandered why big engine builders haven`t tried this.
oltmannd edbentonFairbanks Morse had a Turbo on them Are you sure? All the FM locomotive applications I'm aware of were blower engines. The FM engine was an opposed piston. I can't think of how you could have a four stroke OP engine. On any two stroke, you need a blower to provide scavanging air. There just isn't enough oomph in the exhaust stream at low load and speed to do the job. You can do blower + turbo ala the Detroit 149, but a turbo alone won't do.
The Trains article mentioned elsewhere referred to stationary power plant FM 38D 8-1/8 engines that were fitted with turbochargers.
I believe these were mounted in series with the existing roots blower, which if I recall correctly was driven by the top crankshaft, and at full power absorbed much of the power from the top crankshaft.
This was analogous to the turbocharged Detroit 149 series engine, which retained the same blower arrangement as the non-turbo engine. This worked well but didn't provide the fuel economy advantages of the EMD clutch disengagement system which are significant and the only thing that allow the EMD engine to remain competitive with current four stroke engines in fuel consumption.
Interestingly, the Russians and Chinese built many hundreds more locomotives with unlicenced copies of FM 38D8-1/8 engines, and the majority of these were fitted with a turbocharger that allowed the power rating to be raised from 2400 HP for the twelve cylinder to 3000 HP. The final versions of the Russian TE-10 fitted with these engines were built up until 1990. These were four unit freight locomotives and several hundred were built.
M636C
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