Is that due to the use of turbines over a reciprocating engine - or just the sheer scale (efficiency goes up as the size of the plant does)?
That doesn't seem significantly different from steam or diesel, though, where multiple power units and driven wheels can still be employed. The advantage of electric I suppose is that the driving gear can be very compact - so you can make the power units do other useful things, too.
cheers
Jules
Modern steam engines do not have to stop for water. They can be oil fuelled
Differing systems are under test - 3 in the USA alone. The technology has not settled. Many have all the equipment in the train, others have some in the track. Many are planned around the world. Once settled, standard track and cars can be built in bulk lowering costs. In the UK the main problem is land costs as they require new track. Some can be cheaply elevated on top of existing tracks.
Maglevs. Here they are. They are used in Germany, China and Japan, and one was used for 12 years in Birmingham:
That's the kiss of death, then if you think it's any good.
Hmm, I thought some of the larger ones had automatic stokers - I'm sure that could be adapted for smaller engines, too these days.
The curse of a small crowded island, I suppose - over here it seems to be a very efficient way of getting goods from A to B. It's not uncommon to see trains with three engines and over 200 wagons (and there are no overhead bridges on a lot of routes, so shipping containers stacked one atop the other are a frequent sight).
Some of the fuel consumption figures claimed by the freight companies are pretty impressive - presumably because steel-on-steel is low friction, and these are from routes with no stop-starting and flat gradient all the way.
cheers
Jules
And the answer is "of course we bloody can" not only possible, but possible to do much better than it was in the past. We don't because 7% thermal efficiency is a joke.
A cursory look at the numbers shows just how much energy goes into boiling water into steam, vs. heating the steam afterwards. So although a higher superheat temperature makes for a more efficient steam plant, there's simply no way to be really efficient without a condensor in the cycle.
Condensors are big and heavy. They're universal in stationary steam turbines and with marine engines (piston or turbine), but just too clumsy for locomotives. There have been almost no condensing steam locomotives (a couple of large US locos) where this was done for efficiency rather than for recycling water use in arid climates, or reducing exhaust in tunnels.
A little-known steam engine was the Cornish cycle engine: a slow- moving beam engine that was the final evolution of Newcomen's design and still being built into the 20th century (Dorothea Quarry). Examples, such as the Bull engine at Kew, can still be seen working. Although "obviously" an "obsolete" concept, because these were condensing engines and very carefully thought out thermodynamically, they're surprisingly efficient.
Indeed. Which is why so many steam locomotives did do this, in later years - particularly the French (paired steam-heated feedwater heaters as visible drums behind the chimney) and the Italians (Franco-Crosti system, with a flue-gas fired preheater).
British locomotive design tried this too, with the Crosti boilered
9Fs. However efficiency implies extracting heat from the flue gases right down to low temperatures, where these gases start to produce an acidic condensate. The 9Fs showed useful efficiency improvments and fuel savings, but the maintenance costs from corrosion couldn't be justified.Fluidised bed combustion, high-pressure water tube boilers, trip valvegear etc. would all improve efficiency. In the '70s there was a study by Queen Mary College, London, into just such a locomotive design. But without condensing, it still can't make enough difference
- just too much energy went into boiling that water.
If you care about this stuff, Semmens' "How Steam Locomotives Really Work" is an excellent guide, both as an approachable read and also because they aren't scared to use numbers.
Mostly the fact that you can superheat te steam to get teh working temperautre up and use maissive condensers to get it down again.
The max efficiency of a heat cycle engine is IIRC - and its a long tome ago - something like T2 -T1 all over T0, where T1 is peak heat, T2 is exhaust heat, and T0 is either absolute zero, or the temperature you started with.Which is why IC engines beat steam. Air gets up to several thousand at combustion, although it comes out pretty hot too.
And low C of G.
:-)
Abersystwtyth to Porthcrawl :-)
Oh? think again.
The WHOLE of wales is heavily subsidised..
Its only makes money because of it.
That's probably the grossest case.
Whereas the main lines are paying the government as are the commuter=20 services for the privilege of running them.
The whole franchise business is a complete and utter mess: Viz=20 stagecoaches complaint to DofT reported in yesterdays telegraph.
I happen to know a director of a major train company. He said that if=20 you buy in one away a ticket from York t oLondon with the east coast=20 mainline lot, it will cost tyou around =A3200. OTOH there is a company - =
North East Trains? opereating out of somewhere else who are a subsidised =
local north eastern LOCAL servive, so they run trains from somewhere=20 else VIA York and charge 30 quid, basically to process the ticket. They=20 don't need passengers - they are paid to run trains, not carry passengers= =2E
Its typical Nu Laber bollocks.
some trains are profitable, so sell them to the highests bidder.. Some are not, so define them as a social service, and subsidize them=20 heavily. But dont prevent them competing directly with core mainline=20 business.
And anyway pretty well all the services I'm talking
I was thinking mainly of those. Underground.
As far as I am concerned London stops about at Chelmsford, Harlow=20 Stevenage St Albans, Slough, Guildford, Crawley and Maidstone anyway..so =
you can define intra urban as the whole london suburbia bit.;-)
If the services show up as cheaper than by car, then they are ipso facto cost effective. But heavily subsidised services should be given a very hard look at. Running a tow car diesel rail car 4 times a day up and down a single track line is utter crap really.
Same as many bus services. The average rural bus is worse than a 2 up car, and a lot worse than a full taxi.
There is an extent to which the roads are heavily subsidised, but its a lot less per passenger mile than rural branch lines.
Labour is cheap, and a railwaymans job is still better than starvation. Railway economics threw out steam largely because of the huge maintenance costs involved. Plus the need for vast turntables (the Roundhouse) and a lot of marshalling yards for freight (trains of coal from wales to where it was needed) in prime areas for development.
Its the same reason they threw out piston engined aircraft: Jet's dont need so much servicing.
Someone will have figures on e.g. a Wright radial versus a modern turbofan.
Just to clean the fire tubes in a boiler usually meant opening the loco front, letting it cool down for several hours, and then pushing things down the boiler tubes..then recoal, refire and wait a couple of hours for the kettle to boil..get stuck at signals just before a big pull, and off goes the safety valves..
Nope. Steam is the best way to run a big static engine with a predictable power draw. Its a nightmare for mobile plant.
Its all buried in archives. I've still got manuals for many 60's cars.
Well its like these repro WWI and WWII fighters that are coming out..do you REALLY want an airframe that was lucky to survive 4 hours in combat? And was built with that in mind? engines that probably had an MTBF of less than 2 hours..No, not really. And teh temptation to bolster the known weaknesses is vast..lets balance the engine, use forged conrods, better seals, modern oils, kevlar cables etc etc.
And 100 hours between major overhauls ;-)
The hell it is - the money pipe stops dead at Cardiff, about two blocks past the Welsh Office.
A simplification that only works if there isn't a phase change. So for water / steam cycles, it doesn't really mean much, other than an upper limit you can't possibly reach.
No there isn't.. they have replaced the original iplayer with something that isn't as good just so they can keep a very noisy minority quite!
The new iplayer doesn't have as much high quality stuff to download and needs far more CPU power to run it.
He must have read a good site for a change.. maglev is the obvious solution if superconductors are available.
Pretty well everything he recommends involves lots of 'ifs'.
Please eff off you are a plantpot.
Please eff off you are a plantpot.
The UK is not crowded. Only 7.5% of the land mass is settled. The UK has land surplus.
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