Will steam turbine locomotives such as the Chesapeake and Ohio M-1? With modern technology, could they become more reliable?
Of course they could. All the problems with all three operational steam turbines, the direct drive PRR and the electric drive N&W and C&O are all solvable, and solutions were at hand when they were removed from service. But unless coal gets less expensive and its smoke easier to avoid pollution, and diesel and alternative fuels get more expensive, this would not make economic sense,
While there may be steam turbines in the future, they won’t be coal fired. If anything they would be LNG fired with LNG being the current low cost fuel; both to secure and to burn and pass emission requirements.
As mentioned, the cost of fuel and servicing tend work against them. A different fuel source is possible and UP used it for many years with their large GTEL locomotives. Fuel costs keep rising and they faded from service.
Another issue is the rather rough ride and vibration in train service(or anything moving). Turbines operate best at high speed, and the clearances are quite tight - damaged blades reduce the efficiency of the power plant - Something that a fixed power plant does not normally see. I am sure this can be engineered as the US Navy has turbine powered warships - But I am sure the cost is quite high. The last US rail turbines I am aware of were the Rohr powered Amtrak turbos - and they are no longer in service either - High fuel costs…
Jim
A direct-drive steam turbine is hideously inefficient at startup, and at any speed lower than designed operating RPM. According to one report I read, just starting up would reduce the S1’s boiler pressure from 300# to 85#, which really stressed the boiler and led to some of the high maintenance costs that eventually sidetracked it.
The normal movement of a steam loco in freight service can only be equaled by a warship firing main battery salvoes (or absorbing damage in combat.) This impacts both the turbine and the boiler, and is one reason why water tube boilers were not very successful for locomotives of any design. Also, coal dust got into the electricals of the C&O and N&W turbines - conductive + abrasive = NOT wonderful!
Of course, steam turbines seem to have a future in rail power - but the steam will be generated in fixed boilers, possibly as the waste heat leg of combined cycle fixed-plant gas turbines fired with natural gas. The locomotives will be very straightforward electrics, probably fed by catenary carrying 60hz AC at commercial voltages.
Chuck
You are correct about direct drive on start-up. Some sort of gear-changing and robust clutch arrangement would be essential, and electric drive is a lot better. The vibration problems probably can be solved by proper spring-mass-and damping isolation mounts, easily done with electric drive, since the alternator and the turbine can be isolated as one unit, with all connections, electrical, fuel, and air, flexible. Modern metallurgy might make the problem less severe.
I think there is more to the preference for a fire tube over a water tube design in a locomotive boiler than simply the shock and vibration environment of a train. I think it has to do more with scale formation on non-condensing steam circuits.
Ships and stationary power plants condense the steam, allowing the use of highly purified water that gets reused. That purified water minimizes scale formation as well as boiler corrosion, allowing the use of water tube boilers at high steam pressure. Scale formation is particularly bad for a water tube boiler because it could block a water tube in a way to cause it to fail from overheating. At very high pressure, boiler operators have to purify the water from dissolved gasses so as to not accelerate boiler corrosion.
Steam locomotives with only a handful of historical exceptions use a non-condensing steam cycle where the water is used only once. As steam locomotives use large amounts of water, that water is maybe “softened” with chemicals to reduce scale formation, but it certainly isn’t distilled or purified to the extent possible where you reuse the water in a condensing steam cycle.
The fire-tube “locomotive-type” boiler is more tolerant of scale formation before “bad things happen”, although scale affects it too. Because of scale, you are also limited in the maximum boiler pressure.
There was something called the “Schmidt system” to get higher boiler pressure by using a closed heat exchanger loop of purified water at very high pressure, something like the heat exchange loop in a pressurized water type nuclear reactor plant. Because you were transfering heat to your high pressure boiler with this type of heat exchanger rather than directly to the flames, you could mitigate scale formation at higher pressures. Schmidt, I believe, invented the superheater, which was widely used in mainline steam power, and this sounds like his “second act”
DC electric drive is only about 80 percent efficient. Besides incurring the cost of a generator, traction motors, provision for cooling traction generator and traction motors, and an electrical cabinet with all of the switch gear to make the electrical transmission happen.
The complication and efficiency loss of electric drive was one of the knocks on the Diesel, especially the first generation Diesel in competing with steam. This is balanced against the high efficiency of Diesel engines from idle up to full load relative to eveything else.
Steam is much less efficient, and you hang an 80 percent efficient drive on it and you give back all of the efficiency gain from the superheater, which was considered a huge improvement to steam.
“Overmod” talks about something called the “Bowes drive” intended for the never-built Pennsy V1 steam turbine. I can’t find anything on the Web about it, but I am guessing it is some kind of integrated or modular electric transmission that may have somewhat higher efficiency. The Toyota Hybrid Synergy Drive on the Prius where the prime mover, a motor-generator, and a generator-motor are all connected to a planetary gear drive of the type used in an automatic transmission might be something like it. That system transmits a large fraction of torque by direct mechanical drive with the electrics being modulated to make up the difference to
A large collection of Bowes material survives at the ISM in Philadelphia; here is an online finding aid . (There is also a .pdf version for people who’d rather have a printed version.)
The original Bowes drive patent is 2465006. An improved version with variable ratios is 2715689, and a version ‘sensitive to load speed’ is 2747115. (There is also an interesting version optimized as an automobile transmission, 2732508.) I have not had the chance to get back to the Hagley to compare the description of the Bowes drive for the V1 in their collection with the features in these patents. But this will give you a good idea of the principles and the developed technology.
Bowes incidentally worked on the problems of relays subject to severe vibration or shock, and his patent addressing some of the design issues is 2636095. IIRC the problem with relays was at least as detrimental to the TE-1’s over-the-road performance as was shock to the main turbine…
As a note: there is a report on diesel torsional vibrations through this design of drive. A steam turbine drive would not have this concern.
With LNG as a relatively cheap fuel, and all the extra problems of steam, it would seem like a gas turbine would be the preferred option. I think the UP used heavy oil, which had its own problems.
About one third of the energy in a standard aero-derivative gas turbine is lost as heat in the exhaust… Around the year 2000, a number of cruise liners were built using exhaust boilers on GE LM2500 turbines and steam turbines to improve their overall fuel efficiency to well above that of diesel powered ships.
Of course, there aren’t the same vertical clearances in locomotives as in cruise liners but it might be possible to build a two unit locomotive with a gas turbine in one and the boiler and steam turbine in the other. Maybe three units with a gas tank in the third if that were acceptable…
The Russians already have gas turbine locomotives with gas tanks in one powered unit.
M636C
Early diesels with dc electric drive had 80% efficiency for the transmission. But modern ac alternator to ac motor transmissions have made a modest improvement to about 85% because the slanted-bar rotor looses far less energy in heat than the dc commutator motor armature coils. Some of the gain is lost through the magnetic power transfer across the clearance gap between the rotating bars and fixed coil pole pieces, but some of the gain is retained. If the motors were body mounted for good vibration isolation ,as required for the turbine as discussed above, clearances could be reduced and the efficiency further improved.
Sounds like the system used by EMD in the GA8 and GA12.
Railpower Industries(maker of the Green Goat) designed a 5500 HP Compressed Natural Gas powered gas turbine locomotive which would have used composite gas tanks and been able to operate without a fuel tender (unlike LNG powered locomotives). They had an artist’s conception on their website in UP colors and built a large (maybe G scale) display model in CN livery. they never got enough industry interest to justify building a demonstrator.
The locomotive would have used an Industrial Gas Turbine built by a division of Caterpillar. O.C, Cat now owns EMD, so I wonder if they have looked at the Gas Turbine locomotive concept.
However both GE and Cat are developing and
Ships have the big advantage of unlimited sea water coolant for the steam condenser. Rail mounted air cooled condensers just don’t have the same efficiency.
A couple of comments on all of the above:
LNG as fuel - tested (in diesels) and found wanting. Too little density (BTU/cubic foot) and too likely to turn a derailment into a disaster (BLEVE, anyone?)
Dual-cycle gas/steam turbine power plant
The current AC drive locomotives are 92% - 93% drive efficiency. The last generation AC-DC locomotives were up to 88% drive efficiency. The first generation DC-DC locomotives were around 82% drive efficient. That where the infamous 308 number came from. 308 is 82% of 375 from the Speed X TE / 375 = HP formula. In the current locomotives, a lot of work not only has been done in reducing electrical losses, but mechanical losses between the traction motor and axle. This not only has the effect of improving HP at the rail for a given Nominal Traction HP rating, but also improves emissions because the more efficient a locomotive is in delivering HP to the rail, the less fuel it burns in relationship to the amount of work it can do.
MY EE background told me about the improvement in efficiency for the motors and control and power distribution within the locomotive, but I did not know about improved efficiency for the mechanical coupling between motor and axle. How was this accomplished?
[quote user=“tomikawaTT”]
A couple of comments on all of the above:
LNG as fuel - tested (in diesels) and found wanting. Too little density (BTU/cubic foot) and too likely to turn a derailment into a disaster (BLEVE, anyone?)
d
LNG as a transported commodity is considered HAZMAT - Having a LNG tender coupled to the engine consist???