Why are steam locos so inefficient?

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Moonraker

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I was reading an article today on the development of steam locos and was surprised by the efficiency figures quoted. In 160 years of development, from the Rocket, steam loco efficiency improved from 2 % to around 6%. The best figure achieved was a meagre 11% by Chapelon in France.

So my question is, why are steam locos so bad? Where does all the wasted energy go?

Peter
 
Moonraker said:
I was reading an article today on the development of steam locos and was surprised by the efficiency figures quoted. In 160 years of development, from the Rocket, steam loco efficiency improved from 2 % to around 6%. The best figure achieved was a meagre 11% by Chapelon in France.

So my question is, why are steam locos so bad? Where does all the wasted energy go?

Peter
Click to expand...

Mostly heat loss.

However, I saw a news article recently about the Meiningen loco works in Germany, where they were building Steam Locos with Oil Firing and Insulated Boilers. This is where the boiler for A1 Loco Tornado was constructed.

Because of this insulation, it was easier and quicker to prepare a Loco for running the following day, as it had retained the heat within the boiler. Oil firing also helped for ease of preparation and was much cleaner than coal.

Unfortunately, I can't find this article so as to post a link....

So maybe
 
Moonraker said:
I was reading an article today on the development of steam locos and was surprised by the efficiency figures quoted. In 160 years of development, from the Rocket, steam loco efficiency improved from 2 % to around 6%. The best figure achieved was a meagre 11% by Chapelon in France.

So my question is, why are steam locos so bad? Where does all the wasted energy go?

Peter
Click to expand...
Firstly the loco has to carry a fair amount of water around as well as the fuel. This reduces the overall efficiency somewhat.
If you are just considering the thermal efficiency of the steam plant, compromises in the design of locos need to be made to suit the loading gauge and the fact that they are subject to a fair amount of vibration and shock loads. Optimum efficiency would be reached, I think, working continuously at near maximum output. It is unusual for a locomotive to do that as much of the time it would be cruising along the level, coasting downhill or even stopped at signals. Devices to improve economy such as feedwater heaters and condensers were tried on locos but in most cases the improvement in overall efficiency was more than canceled out by their initial cost and increased maintenance costs.
In contrast power stations use steam turbines running continuously at near maximum output, have much more space for big boilers and their static nature and economies of scale make feedwater heaters, condensers etc. viable.
 
A lot of the loss is up and out the stack. All those beautiful plumes are wasteful.
 
Moonraker said:
I was reading an article today on the development of steam locos and was surprised by the efficiency figures quoted. In 160 years of development, from the Rocket, steam loco efficiency improved from 2 % to around 6%. The best figure achieved was a meagre 11% by Chapelon in France.

So my question is, why are steam locos so bad? Where does all the wasted energy go?

Peter
Click to expand...


tac is quite right, but the longer answer is that steam engines, like petrol engines or even gas turbines, belong to the thermodynamic class of 'heat engines'. They turn the fuel to heat and use some of the 'energy' to produce motion. The rest of the 'energy' is discarded as exhaust. Its a bit of a simplification, but the major cause of inefficiency in a steam engine is the exhaust. If you think about domestic gas central heating boilers, the modern efficient variety are the condensing type, where the exhaust is cooled to retain the 'energy' within the boiler instead of discharging it to atmosphere.

Other losses include 'energy' retained in incompletely burned fuel, boiler & firebox heat loss, and steam leaks. In addition, a reciprocating piston is mechanically inefficient at producing circular motion.

I'm not sure that 11% was the best ever achieved in a steam locomotive. I suspect that much better values were obtained in experimental US designs, but my own steam experience is with non-motive turbines.

Don
 
Moonraker said:
I was reading an article today on the development of steam locos and was surprised by the efficiency figures quoted. In 160 years of development, from the Rocket, steam loco efficiency improved from 2 % to around 6%. The best figure achieved was a meagre 11% by Chapelon in France.

So my question is, why are steam locos so bad? Where does all the wasted energy go?

Peter
Click to expand...
Others have answered the direct question, but if you are interested in getting greater detail, have a look for a copy of "Dropping The Fire", published in 1999 by Irwell Press in association with the (UK) National Railway Museum (ISBN 1 871608 899). Lots of detailed information about why the steam locomotive fell from grace rapidly after World War 2. Were you aware, for example, that British Rail was having to import suitable coal for steam locos by 1960?
 
One other problem with a steam loco is the heavy weight which must be hauled about just in the component parts. There is lttle scope for weight saving to improve fuel economy.
 
There are a lot of factors to take into consideration before condemning a steam loco as being inefficient.For instance,how long does a steam engine last compared to electric or diesel,well maintained ,100 years?.How much damage to the track is caused by electric and diesel compared to steam,a lot more,I know.On top of that,steam is much easier to maintain and build also much more beautiful in motion.
 
Interestingly the steam engine itself is a very efficent drive.
The attribute of steam to expand like nearly no other gas without a chemical burning reaction makes the drive effective. Good locos are constructed to go with steam expansion, not just with steam filling.
Powerplants use steam turbines, because no other medium offers the attributes to carry the energy efficiently.
With the volume, the fact of beeing stationary, a highly detailed optimizing of mechanics and steamflow gives such plants an efficiency of 70-80 %

The problem with railroads is, that u need power 1.) mobile and 2.) with very changing effort.
That was always a problem and is till now. Not just with steamers. The only reason of creating a diesel-electric loco is the fact that the diesel can start from "0" velocity. Electric drives are good to controll. The efficiency of a diese-electric loco is bad comparing to a hydraulic geared one.
Diesels have a bit better efficiency than petrol-engines, but that was never the fact why they were used.

To give another example that may relativate the 11-13 % of a steamer is to take an average otto-engine of a average mass-producted car in the 1990´s. The efficiency is just about 30-32 % on the engine, and only 20-23% at the wheels.

So, the steam engines ARE not that bad.

There are several things to look at:
Heatloss IS a major problem, but not just in the exhaust! Bad isolation of the boiler and the way how the coal-energy is changed into water-stroed energy is ineffective. Surely the whole construction isnt capable to save heat in exhaust. Therefore some cunstructions tried to change this and use more of the heat. Think about overheated steam and double-heaters like the franco-crosti-construction.

Another, also mentioned main matter is the mass that has to be moved. Neither the heavy boiler nor the knietic losses on piston, steering and rods are useful for an effective drive.

The need of changing interatomic-energy in heat by burning, takeing this heat and store it in water, making it to steam by taking it out of storage and then change it first into kinetic linear energy in the pistons and then kinetic spinning energy with the rods is a very long way to go and therefore filled with losses.

The fact that this has to be mobile on a frame and wheels doesnt make it better.

the German 52 8055 was modernized by the Ing. Roger Waller from Swizzerland.
With this project he proved that with some changes on an old steamer, u can make it much more effective.

Really modern steamers are a bit better, because they have a better harmony with the new effords and techniques used nowadays.
How far he brought the efficiency til now i do not know.


So, when steamers died, there were some trys to rescue them....but in most cases, u need 2 man personal and the whole, free-running and just slighty-lubricated, mass-moving piston-drive is no construction to go into a future.

All efforts to hold the steam on the rails came too late and therefore were done just "half-hearted".

It was -to go further- that miserable wars that always cut down all efforts to bring the steamers a future:

not the efficiency was a question. Not the amount of burned coal. Not the costs of crew.
The only things that were interesting was: simplicity in construction and operation. To have as many locos as possible, easy to repair and made of less material.

They just had to move.

Reliable.

When the war was over, there was a bunch of those simple locos, and when they were used down, the time of steam was over.
In the 1920´s we had much more elegant and effective locos then in the 1950´s.



long posting...sorry


Frank
 
In "The Red Devil and Other Tales from the Age of Steam", David Wardale quotes some figures from E.S.Cox as 14% clinder efficiency, 72% boiler efficiency, and 90% final drive efficiency for an overall 9% efficiency. He does also make some comments that the maximum efficiency does not occur at typical operating conditions. Later David says that by using modern engineering know-how it should be possible to raise the efficiency to over 16% which is comparable to diesel and electric traction. Engineering knowledge of fluid dynamics has come a long way since computers become avalable. Do a search on "Modern Steam" to turn up a lot more on the subject.
 
I just read the Wikipedia article on steam engines which covers the whole topic pretty well.

The fact that quadruple expansion engines were used in ships makes one realise how much energy is wasted up the funnel in a single expansion locomotive.

Peter
 
Nodrog1826 said:
Gizzy said:
Moonraker said:
I was reading an article today on the development of steam locos and was surprised by the efficiency figures quoted. In 160 years of development, from the Rocket, steam loco efficiency improved from 2 % to around 6%. The best figure achieved was a meagre 11% by Chapelon in France.

So my question is, why are steam locos so bad? Where does all the wasted energy go?

Peter
Click to expand...

Mostly heat loss.

However, I saw a news article recently about the Meiningen loco works in Germany, where they were building Steam Locos with Oil Firing and Insulated Boilers. This is where the boiler for A1 Loco Tornado was constructed.

Because of this insulation, it was easier and quicker to prepare a Loco for running the following day, as it had retained the heat within the boiler. Oil firing also helped for ease of preparation and was much cleaner than coal.

Unfortunately, I can't find this article so as to post a link....

So maybe
Click to expand...

Gizzy
This maybe what you were refering to...

http://www.youtube.com/watch?v=hm9aj0fbxS0&feature=related
Click to expand...

Thanks Nod, that's the one?

I'd even forgotten it featured Kirsty Wark, the thinking man's crumpet....
 
And having watched this Youtube clip again, I now realise it was Sulzer Winpro in Wintertur, Switzerland, and not the Meningen Workshops in Germany, as I thought before.

It's an age thing....
 
Efficient - who mentioned efficient?

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These pics from:-

http://www.dself.dsl.pipex.com/MUSEUM/LOCoLOCO/diesair/diesair.htm < Link To http://www.dself.dsl.pipe...CO/diesair/diesair.htm

David
 
the diesel-air loco is one of the first big-block-diesels at all.
The problem the constructors had was to bring the diesel-power to the wheels up from zero-velocity.
Later the diesel-electric drive was invented for that.
for Horsepower up to about 3000 u can use hydraulic gears, what is an expensive to build but fine to drive alternative to the diesel-electric construction.

So, he diesel-air loco was the first try to use airpressure as a fitting between diesel-block and wheel.
mainly pure steam-technique was used on the airside, and so it was no wondering that it didnt work well: air hasnt the attribute of expanding like steam has.

At that time, thefirst hydraulic transmissions for small diesels were constructed, and in the end it didnt take long to have a bigger one. the V140 may be the first german loco to be named hydraulic big block diesel.

the diesel-air loco was just a test.


Frank
 
I have a series of DVD's that shows in Switzerland they put a pantograph on a tank loco to get steam from the overheads. Now all I have to do is remind the bloke I lent them to that I want them back!
 
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