Natural Gas vs Oil

It is possible to fire a steam engine with anything that burns.  However, in steam vs. diesel, the best steam engines in this country had a thermal efficiency of 9%  The French did a little better by using compounding.  The modern diesels have a thermal efficiency above 50%, so using natural gas to operate a steam engine would use 5x+ more fuel as compared to a diesel.  

Wow, 9% is much lower than I would expect. The question is whether this efficiency could be raised with modern technology and by how much. Probably not enough since it is a steam cycle where fuel combustion is used to heat the steam as opposed to a diesel where the combustion is used to create work directly.

I think this is a pretty neat topic especially given my love of the ill fated turbine steam engines at the end of the steam era.

My interest is in a different scenario. Assume fossil fuels are not available other than coal or oils too heavy to be useful for combustion. Would there be case then to resort back to steam power in modern form. Probably crazy talk but fun to think about.

S

An engineer named Porta did some great work improving the power and efficiency of steam locos:

http://en.wikipedia.org/wiki/Livio_Dante_Porta

Look for a loco named "Red Devil" on YouTube to see one of his locos in action.  There is also a pair of Garratts double heading, one of which was modified, while the other was not.  It is interesting to see the two working together.  There was a guy named Dave Wardale who worked with Porta and has written some interesting stuff about steam locos.  

The efficiency of a prime mover is limited by the temperature it works over.  The internal combustion of the diesel is very hot compared to the highest steam temperature of a steam loco, even with superheat.  The diesel efficiency went up considerably when the injectors were made to have very high pressure which atomized the fuel extremely well.  

The world is not running out of oil.  There is a huge oil field in this country which is believed to go under the Gulf of Mexico into Venezuela.  The US and Canada have huge oil, gas, and coal reserves.  

I highly DOUBT that re introducing steam power is going to be considered just because natural gas is readily available.Nick

There have been Natural gas locomotives when I was working for MK rail in the 90's, and I'm sure even before that.

Don

I wasn't proposing re introducing steam locos, just using it for those engines currently in operation. Although, just a few years ago, the British built a brand new re designed steam loco from the ground up. I don't recall what was used for fuel though.

Don

And..there are, of course, nuclear powered ships and submarines.....just a tad difficult

to sell politically, but how would they rate in efficiency, with steam power?

Considering that a nuclear reactor is just a fancy way for creating steam, the only real difference between a steam locomotive and a nuclear reactor is the type of fuel it "burns."

With a steam locomotive, you may have to refuel is several times a day. 

With a nuclear reactor, you refuel it once every 30 or more years. 

Of course, nuclear "fuel" is significantly more expensive. 

Nuclear reactors are quite large. Plus all the necessary accessories like water reservoirs, heat exchangers, and of course the steam turbine and power generation equipment. 

You cant really "turn of" or even cool down a nuclear reactor.

(That's the thing about chain reactions, they just keep going and going and going...)

 And let's not even talk about what to do if one of these thing were ever involved in a train wreck 

but how many diesels would it take to pull the same load?

Natural gas can power anything that coal, oil or nuclear can power, and probably do it more efficiently.  The problem is that natural gas cannot be carried in a bucket or barrel - it would escape into the atmosphere.  So, it must be contained in a pipeline or a compressed cylinder (or the like).  My guess is that it would take a lot of tenders to store the natural gas used to fire the boiler.

Earl.

The problem with the use of gaseous fuel in mobile applications is energy density.  To get a decent amount btu stored in mobile vehicle it needs to compressed or liquified.  LNG stands for liquified natural gas, the same way lpg stands for liquified propane gas.  Propane actually has a much higher energy density than natural gas, thus making it more valuable.  It is certainly possible to run a fire tube or water tube boiler on gas, I've had several of them under my charge for work in various pressure and capacities. (look up Scotch Marine boiler - that design is particularly well suited for gas firing and is somewhat similar to locomotive boilers) I know some narrow gauge park engines, think 15" gauge, were actually run on propane cylinders like those used on industrial forklifts.

To answer your question it can be done, but may not be practical or at least not cost effective.  You would have a significant amount of capital dollars tied up in engineering and equipment to convert a tender to either a series of small tubular tanks tied together or a large tank, either of which would likely have to be FRA approved.  Then you need a burner that can handle the gas and distribute the heat evenly to the existing firebox.  and last but certainly not least the firing system has to be able to handle the pulsating flow of draft created by a steam locomotive exhaust.  All modern systems are designed for fan powered flow of air/combustion gases.  I believe it can be done, but again may simply not be practical.  In the end it would come down to a few very basic factors. 

1. will the conversion have an acceptable return on investment?

2. Is it something that must be done in order to allow the machine to continue to operate? ( Think Baltimore smoke ordinances that required oil firing over coal)

3. Is the equipment available technically up to the real world operating environment?

just my $0.02 for the evening.

Fuels that are rich in carbon have more energy than natural gas which has 4 hydrogen atoms attached to a single carbon atom.  When a carbon is oxidized to CO2, it releases much more heat than when two hydrogen atoms are oxidized to H2O.  This is why coal is such a good fuel for stationary power plants.  It has a very high energy density.  And when the global warming fanatics are shown to be wrong, and the evidence that the earth is actually cooling off, the release of CO2 into the atmosphere will be shown to be beneficial to the plants.

Propane was successfully used in UP #57 for awhile in the early '50s,  between LA. and Las Vegas, IIRC. The effect was superior to that of Bunker C, but the danger factor across the board and the special fuel handling killed any wider application at that time.

That's a great question and brings me back to the Pennsy turbine. Not sure about fuel consumption but a relatively small turbine per the ad copy below was able to deliver about 4MW of power to the wheels. Probably at peak efficiency for the turbine. 4MW is about 5300 HP.

Does anyone know why gas turbines burning LPG, or LNG can't be used on railroads instead of diesel engines. The power companies have been using gas turbines for years to generate electricity on a comercial basis.  So why not use a gas turbine to generate electricity for traction motors instead of a diesel?  Turbines are much more efficient than reciprocating engines. Some power plants us natural gas fueled turbines then take the exhaust gas and use it to heat a boiler that produces steam that is used to generate more electricity.  The gas turbine must not have much pressure on the exhaust or it deminishes it's efficiency.

Douglas

Turbines in general have an efficiency problem at part throttle.  That was the problem with the Pennsylvania steam turbine.  Great at full throttle.  Miserable at part throttle.  Gas turbines have the same problem.  The latest data I have on gas turbines is that their efficiency is above 50% at full throttle.  Diesels provide high efficiency at part throttle which I am sure is the reason they are used for railroad locomotive.  

Diesel electrics can supply much more starting drawbar pull than steam engines.  The drawbar pull of a diesel is limited by how much current the traction motors can take, and how long it takes the traction motors to heat up. 

At 8 mph, a loco is moving at 12 feet/second.  If it is a 3000 HP loco, it can have the drawbar pull as high as 3000 * 550 ft-lb/sec/hp / 12 = 137,500 pounds of drawbar pull.  This ignores the efficiency of the alternator and traction motors.  As the speed increases, the drawbar pull is reduced. A three unit diesel with 3000 HP units would have almost half a million pounds of drawbar pull at 8 MPH.  

For comparison, a Big Boy has 135,375 lbs of tractive effort at low speed and 7000 hp at 30 mph.  

Union Pacific did build some gas turbine locos.  You can find information about them on the Internet.

A lot of great info on this and the oil vs coal thread.

Don

Many gas-turbines have been tried in a variety of locomotives, using all ranges of fuel types. All have been abandoned in favor of traditional diesel engines or overhead electric lines. 

The Union Pacific actually had  a rather large and long operating history with Gas Turbine locomotive technology . A total of 55 locomotives of three design generations were built for the railroad and they averaged over 1,000, 000 miles each in revenue service . These locomotives operated in a period from 1952 until 1969. The impetus for the design was the availability of very low cost Bunker C for use as fuel . In the end industry refining techniques improved such that there was less Bunker C available making it more expensive  and the operating economics in favor of diesel fueled locomotive.

Fuel cost per mile would be a large consideration in locomotive prime mover choice and with abundant low cost natural gas availability, a CNG electric locomotive design might prove hard to resist.

Improvements in fuel tender technology that enables all of the high pressure conversion of LNG to be contained on the tender and not in the engine are making it feasible again for modified diesel engines. UP and CN have done the most testing with BNSF close.

I suspect the cost of diesel with existing fuel supply points still make oil the fuel of choice.

There is a very interesting article about modern higher efficiency steam locomotives (including the CE-635) in the september 1985 issue of Popular Mechanics. The article starts on page 90. Link to the magazine.

I have read quite a lot about the ACE project.  Porta and Wardale were part of this project.  I think it died because the railroads backed out because the price of oil went down for a while so there was not enough competitive advantage to coal.  Also, the project didn't stay focused on a single solution.  At one point in time, they were considering a Garratt.  With the diesels getting above 50% efficiency, I don't think the ACE locomotive would now be competitive.  Porta and Wardale had made design changes to steam locos which largely overcame the problems of smoke.  Look up the Red Devil on YouTube.