Reinventing the steam locomotive

An article in the news today got me thinking about an idea I've had for ages.

http://www.bbc.co.uk/news/uk-england-23109971

Fuel is getting more and more expensive and its not going to get any cheaper. We're also increasingly aware of environment implications of burning various fuels.

Wouldn't it be great if there was a carbon neutral fuel capable of powering trains, that was almost completely clean.

Enter, the reinvented steam locomotive by CL1.

First up, what's wrong with the original concept? Well, its heavy, wasteful and stinky. Most of the energy produced by the engine is used just to move the engine itself, its fuel and its water.

It didn't matter in bygone times because the coal that powered them was abundantly available in the local area, and nobody gave any thought to the environmental impact back then. Even if it did matter, the technology was a bit limited in those days.

Why is it so wasteful? Primarily because after water has been allowed to expand as steam, it is simply vented to the air, so you have to carry enough water (weight) to keep the train moving while discarding the water into the air. Its an 'open loop'.

So what about this. Just like in a car (but on a much larger scale), you stick a radiator on the front. After some water has been allowed to expand into steam to push a piston, instead of venting to air, it vents into the heat exchanger, is condensed back into water, and goes back into the water tank. Instantly, you can reduce the amount of water you need to carry by about 90%.

It takes a lot of energy to heat water to boiling point. A lot. 4200 joules per CC per degree centigrade to be precise. So after we've re-condensed our steam back into water in the heat exchanger, we want it to condense back into its compact liquid form, but at the same time be as ready as possible to leap back into its voluminous gaseous form (steam). With a few valves and some clever electronics, we could constantly retune our heat exchanger to ensure that it doesn't shed more temperature than necessary, aiming for an output temp of around 98'C, still liquid but very ready to become steam. Instant massive reduction in energy required to heat the water.

So with that simple little modification to the original design, you theoretically end up with a very compact steam engine with a very high energy conversion efficiency.

So what about heating the water while on the move? Well now that we need much less energy to keep the water boiling, we need far less fuel, and with modern technology, we could have it burning more or less anything that burns, rather than specifically something easy to burn like coal. There's a power station near me that burns old bits of wood (literally, smashed up old bits of old doors and all sorts).

And finally, what about the smoke? A bit of engineering beyond me comes into play here, but the idea is that the exhaust gases are pumped through the water in the engine before being released. Perhaps if our heat exchanger output went to a seperate intermediate tank to the boiler, and was not under pressure, that could be the place to do it. All the particulate waste plus any water soluble gases would be locked up in the water, in the closed loop, much like how a modern car engine locks nasties in the engine oil. The exhaust gases would be hot, so you'd get the added bonus of less energy being lost, because instead of that heat being carried away into the air, it gets transferred into the water that we have to heat anyway.

Trouble is, after a while, that water would become one filthy, nasty mess, having mopped up all that smoke. It would need to be changed at intervals. What do you do with such dirty water? You pour it into the reed and willow bed that has been purpose planted to contribute to the solid fuel requirements of your new engine.

I think its brilliant

 

I was building a prototype like that to run a turbine, it was only when I was googling for an expansion vessel that I found the Germans had already built one

 

The sterling steam / external combustion engine always fascinated me. It looks really fast and efficient , but as I know of no practical applications it must have a major flaw somewhere.

 

The sterling has been around since 1816, FC , this is only a toy demo engine. There is still a lot of development going on with them . Possibly they can never reach the efficiencies of an internal combustion engine .

 

Engines that don't respond well to changes in demand aren't necessarily a bad thing. Take the diesel electric engines on modern trains. Internal combustion engines are extremely inefficient. Even with a modern engine, you can only expect about 10% efficiency at best.

But most engines have a 'sweet spot', where they are most efficient. So you spin up an engine to its most efficient speed, and have that drive an electric generator, which in turn drives an electric motor. What you get is a very efficient torque converter. The drive motor can be stuck stationary and all it means is that all of the electrical power it is consuming is is being converted to torque. Unlike, say, a car engine with a clutch, where to get the car moving from stationary without either tearing things or stalling, you have to throw surplus energy away at the clutch through friction and heat.

The downside with constant speed engines with some form of torque converter (like the diesel electric) is all the weight. You have an engine, then the weight of a dynamo/alternator, then the weight of a motor, plus some pretty hefty cabling to cope with all that current.

This is why I think my theoretical modification to the conventional steam locomotive is brilliant. You strip away the weight of the huge water tank (because its a closed loop now so the water is recirculating). You strip away the weight of the fuel pile, because you need less fuel. There's no loss from a standing start, because the pressure is there, and that pressure will become torque regardless.

 

Thanks fat controller but I simply don't have the engineering expertise to make it happen, although I have toyed with the idea of taking a cheap scrap 4 stroke engine, and some how botching the gearing to the cam to make a sort of 2 stroke with valves, which is what I reckon it would need. I.e do away with the induction and compression strokes, and have the pressurised steam push the pistons down on what would be the induction stroke (ie when the inlet valve is open), then skip direct to the exhaust stroke to let the steam go off to the heat exchanger/condenser.

Then I thought about it some more, and figured that would probably take some clever milling tools and expertise way beyond my reach. Then I also figured that while I'm convinced the idea would work, I have no idea how I'd calculate the requirements for things like the heat exchanger etc.

I'm quite happy for someone to nick my idea and make it into something. Its quite rare that the person/people that come up with the ideas actually make anything out of it. Classic example, who built the first passenger steam loco? George Stevenson right? He couldn't figure out how to get the piston to return to its start position. His idea didn't work. One of his apprentices came up with the idea of a valve on a rocker to redirect the steam. You never hear praise for George Steven's apprentice

If my idea was to get nicked and put to good use, that would do for me.