Modern Steam

[Yew]

As you know, there are few steam locos that ever run on mainline track (ie not heritage) But, if a loco where designed today, using modern materials and processes. Would you have somthing that could go up against deisel/electric units

 

[deltic1989]

Like Tornado you mean? or are you getting at something different. For me steam is less economical than electric/deisel simply because of the amout of people involved in starting, running and , shutting down a steam loco. It would be lovely to see mainline service steam again but it was expensive in the 60's and as far as i know nothings changed. (I do stand to be corrected though)

 

[LexyBoy]

You mean design a steam engine from scratch using modern technology?

IIRC "traditional" steam locos at the end of the era were reaching around 7% thermal efficiency. Locomotive engineers did experiment with designs with high pressure boilers which do give higher efficiency, but only had limited success (though some did see regular service).

The 5AT project aims to design an improved loco - they hope for 14% efficiency. There's quite a bit of detail on the website.

I'm not an engineer but it could be that the most efficient design would have a smaller boiler designed to run a series of turbines (high, medium, low pressure) to generate electricity at a constant rate. This would be stored by a small battery or flywheel to provide enough power for acceleration (and allow regenerative braking). This would then run electric motors (which are extremely efficient).

I don't know about the boiler design but would imagine it would use finely dispersed fuel (assuming we're using coal or oil) with air being pumped in to ensure full combustion.

Such a loco need not take long to start up - it could run from an auxiliary electrical supply initially to rapidly reach boiling point and could be operated with only a driver just as a diesel can.

 

[TDK]

As you know, there are few steam locos that ever run on mainline track (ie not heritage) But, if a loco where designed today, using modern materials and processes. Would you have somthing that could go up against deisel/electric units

There wouldn't be any point designing a steam loco as it would never be as efficiant as a diesel and cost too much money to both manufacture and run.

 

[w1bbl3]

I'm not an engineer but it could be that the most efficient design would have a smaller boiler designed to run a series of turbines (high, medium, low pressure) to generate electricity at a constant rate.

I don't know about the boiler design but would imagine it would use finely dispersed fuel (assuming we're using coal or oil) with air being pumped in to ensure full combustion.

I assume that your aware you've just described the basic generating principles of a modern coal fired power station.. pulverise the coal and feed it into the combusters with high pressure air create supercritical dry steam drive a turbine set to produce electricity, run the hot used steam into a heat exchanger to preheat ready for the next cycle.

 

[E&W Lucas]

There wouldn't be any point designing a steam loco as it would never be as efficiant as a diesel and cost too much money to both manufacture and run.

The major advantage of steam over diesel and electric traction is actually lower build cost. It is a far simpler machine after all. However, that fails to recognise that all the infrastructure necessary to operate steam traction is long gone, as is the skill base to operate and maintain it on a large scale.

Sadly, any idea of the reintroduction of steam is a fantasy.

 

[jopsuk]

Pretty sure we've had this discussion on here before- you've got the huge inefficiency of having to carry around vast quantities of water, much of which has to be heavily insulated lest it radiate away energy.

 

[Yew]

Just to clarify, im not saying reissue ing old locos (like a new A4 class) but totally new designs, ceramic insulated boilers (maybe even vaccum insulated?) maybe a heat pump for a motor (take heat from the surrounding area, and use it to heat the boiler) steam turbines (maybe a multiple expansion like outlined above)

use modern lightweight materials to give a better power to weight ratio (anything from aluminium, to carbotanium)

 

[LexyBoy]

I assume that your aware you've just described the basic generating principles of a modern coal fired power station.. pulverise the coal and feed it into the combusters with high pressure air create supercritical dry steam drive a turbine set to produce electricity, run the hot used steam into a heat exchanger to preheat ready for the next cycle.

Indeed. Power stations of course run a closed cycle with no water loss, which wouldn't be possible in a loco since it would be impractical to provide the cooling needed to re-condense all the water. It might be possible to drastically reduce the amount of water needed by using air cooling and heat pumps to cool the steam. The problem with heat pumps is that they become less efficient the larger the temperature differential - and in the end you still need to shed an awful lot of heat to your surroundings, which is not an easy task when there is only air as a sink.

Just to clarify, im not saying reissue ing old locos (like a new A4 class) but totally new designs, ceramic insulated boilers (maybe even vaccum insulated?) maybe a heat pump for a motor (take heat from the surrounding area, and use it to heat the boiler) steam turbines (maybe a multiple expansion like outlined above)

use modern lightweight materials to give a better power to weight ratio (anything from aluminium, to carbotanium)

Certainly all these things would help - and modern insulation is very efficient and lightweight - but as jopsuk says, inevitably you'll have to carry a lot of extra weight around - more than a comparable diesel (which only has to carry fuel and generator) and much more than an electric (which only needs a transformer). In the context of a heavy freight train, this additional weight is not going to have much impact on performance, but it will on a passenger train.

Turbines would be the way to go for higher efficiency (which would necessitate electrical rather than mechanical transmission), but I think the weight of such a machine would limit its application in this country at least. Something that might be on its side though could be emissions regulations (bizarrely) - it is possible to get much more thorough combustion in a furnace than in an internal combustion engine, so particulates and NOx would be reduced (depending on the fuel obviously).

Oh, and if you wanted to make a nuclear powered train, steam would be the way to go

Edit: This page might be of interest. Note that most of the disadvantages are related to using mechanical transmission rather than intrinsic to the turbine - though of course the comparison is to other steam locos rather than modern traction.

 

[jopsuk]

you're still not going to get round simple facts:
You need to cart around large amounts of water- this adds weight. Addtional weight is not going to be helpful
Very roughly, the energy content of a kilo of diesel fuel is around double that of a kilo of high grade coal. This is a real killer.

 

[Yew]

you're still not going to get round simple facts:
You need to cart around large amounts of water- this adds weight. Addtional weight is not going to be helpful
Very roughly, the energy content of a kilo of diesel fuel is around double that of a kilo of high grade coal. This is a real killer.

who said anything about coal, deisel, gas, anything (wood even) ? and large amounts of water? how about condensors, and using a flash boiler?

 

[gordonthemoron]

most locos in Poland are powered by coal

coal is turned into electricity in power stations and used to run the trains

 

[LexyBoy]

who said anything about coal, deisel, gas, anything (wood even) ? and large amounts of water? how about condensors, and using a flash boiler?

Indeed, with a turbine a flash boiler would be suitable, meaning only a small amount of hot water involved. LNG has about the highest energy content of the normal fuels, ~55 MJ/kg compared to ~48 MJ/kg for diesel and ~24 MJ/kg for coal. Wood isn't great at ~18 MJ/kg, unless of course you plan to collect it en-route from the lineside.

Condensors will certainly help both in saving weight and energy (the condensate will be close to boiling point), but you're really limited by how much heat you can lose purely by convection and radiation - this is why power stations have several massive cooling towers (with evaporative cooling) for each chimney stack...

Let's say our loco is rated at 2.2 MW (~3000 hp). At an efficiency of 20% - around three times better than existing steam locos - that means 1.76 MW of waste heat. The actual calculations required are rather beyond me but given that the temperature differential between the steam (just over 100 C) and outside (say 10 C) is relatively small, the cooling effect will be small and thus require an enormous area and/or heavy, large fan systems or heat pumps.