Welcome to this latest (and sadly, last) entry in the Micro Gas Turbines in Transportation series! Today, we’ll be having a quick look at micro gas turbines and their larger siblings, specifically the history of how they have been used in railroad locomotion and what the future holds for micro turbines and railroad technology. We’ll also consider the advantages and disadvantages of using them to drive trains.
Rail transportation has been around in one form or another for longer than you might think. There are examples of wheeled carts running on fixed roads and tracks that prevented any deviation being used since the 6th century BC in ancient Greece.
Up until the late 18th Century, however, railroads were rather limited in what they could be used for, since there was no way of mechanically propelling the vehicles used. Rather, these railroads relied on humans, animals, or gravity to move the carts along the tracks. This changed when in 1784, the great Scottish inventor James Watt created and patented the first steam engine locomotive which was an improvement of a steam engine designed by Thomas Newcomen. Following this invention, engineers in the UK working on different projects such as Richard Trevithick and his development of the first high-pressure steam engine would lead to the first uses of locomotive-hauled railway. His invention would be used in Wales on a short 9 mile run from an iron-works in Penydarren to the Merthyr-Cardiff canal.(2) On February 21st, 1804, the first trip took place on this railway using only steam propulsion.(2) However it wasn’t until George Stephenson’s creation paved the way for public use of steam engines like those created by James Watt on the rails, and in the coming years rail travel would play an important role not just in the United Kingdom but in the United States as well. This raises the question, where and when did turbines and turbomachinery come into play in rail travel?
Believe it or not, gas turbines in trains were being experimented with long before Frank Whittle and Hans von Ohain were designing them to take to the skies. As far back as 1861, the year that Abraham Lincoln became president of the United States, patents were being filed for a turbine that utilized ambient air mixed with combustion gasses to drive a turbine. As seen in patent 1633, Marc Antoine Francois Mennons created an engine that included all of the components needed in a modern gas turbine engine. It was called a “caloric engine” and it had a compressor (called a ventilator), combustion chamber (using ambient air and burned wood or coke), and a turbine to create work from the combustion gasses as well as a pre-heater (which he called a regenerating apparatus).(3)
It was another near-100 years before gas turbine locomotives really entered use, however. A large part of that was not just because of the need for gas turbine technology to advance, but also because there was a struggle as to how to best harness the power of the gas turbine engine to provide locomotive power. Since a gas turbine is designed to operate optimally under full load, and trains do not constantly operate at such conditions, there comes a need to transmit the power of the turbine across a wide range of loads.
One solution, which was first rolled out by Renault in France, was to use a 2 shaft turbine engine, where one turbine stage (or stages, hypothetically) would drive the compressor, and then another separate turbine shaft would drive the mechanical gearbox. This configuration is called a “free-shaft” turbine. The challenge here was that the high ratio between the speed of the turbine and the speed of the wheels required a serious transmission to transmit the power from the turbine to the wheels effectively. As a result, by the time the mechanical drivetrain for a gas turbine locomotive was implemented, the gas turbine electric locomotive (GTEL) had already been around for some time.
The GTEL was probably the most “logical” setup for a locomotive where the main powerplant was a gas turbine. It utilized a generator to generate electricity from the shaft power of the turbine, which in turn was utilized by electric traction motors that drove the locomotive itself. This setup negated the need for any complicated transmission or clutches to efficiently harness the power of the turbine. This setup was used in locomotives through the 1950’s and 60’s, most notably on the Union Pacific railway.
In both cases there were downsides to utilizing gas turbines as the primary mover or powerplant in locomotives. One of which was the fuel, which was sometimes fuel oil (also known as bunker-c in the Naval and Maritime world), notorious for its lower quality as compared to kerosene and jet fuel. Using bunker oil could accelerate wear on a gas turbine, and also meant that greenhouse gas emissions and sulfur dioxide emissions were extremely high. Additionally, the hot exhaust gas temperatures from a gas turbine made it less than ideal in certain situations, such as if it were in an enclosed area. These gas turbines were also extremely loud.
Before we move on to micro gas turbines in rail transportation, there is one more special case I want to look at where train locomotives utilized the thrust of a turbine engine as opposed to the mechanical shaft power generated by the turbine. This configuration was exceedingly rare and is known as the “turbojet train”. Unlike their other locomotive counterparts, the turbojet train incorporated the engines into the passenger car, negating the need for a separate locomotive. Additionally, turbojet trains would operate more like a commercial airliner, operating at a high travel speed and making fewer stops, which was more in line with how a turbojet efficiently operates. The United States and Soviet Union each had experimental railways where such a train could operate, with the US creating the M-497 Black Beetle, and the Soviets creating the ER22. The M-497 would set an American record for the fastest rail vehicle in July 1966, which still stands to this day. The Black Beetle utilized GE J47-19 turbojet engines that had originally been used on the Convair B-36 Peacemaker bomber.(1)
These trains were never widely used, since the need for a very straight rail line plus the narrow efficiencies and high fuel consumption that comes from simply putting turbojet engines on top of a train were not all that economical. It also goes without saying but since these trains would probably pass through residential areas like the one in the picture of the M-497, the noise complaints might also have hurt its viability. Having said all that, however, this is definitely one of the more unique ideas for rail transport to come out of the 20th century.
In almost all cases, gas turbine locomotives fell out of favor in rail transportation because of their low fuel efficiency and narrow power bands as compared to their reciprocating diesel engine counterparts. But what about micro gas turbine powered locomotives? Can they help stage a comeback for the turbine in locomotive applications?
As we have discussed and analyzed in previous articles, micro gas turbines come with their own set of pros and cons. Among the pros are a very high power to weight ratio as well as fuel diversity, longer maintenance intervals, lower greenhouse gas emissions, and lower complexity when compared to a reciprocating turbodiesel engine. Conversely, the drawbacks of running a micro turbine include a very narrow powerband, strict tolerances, higher cost of parts, the potential need for higher-grade fuels, and the potential cost of servicing the turbine when it undergoes preventative maintenance or repairs.
There is serious potential for micro turbines in hybrid power, similarly to the old generation of gas turbines where the shaft power drove a generator as opposed to being transmitted to the wheels. Thanks to advances in compressor design/development, recuperator technology, the rise of natural gas as a fuel in transportation, and a drive to lower greenhouse gas emissions, the stage is being set for micro gas turbines to start being used in locomotives either as auxiliary power or as the primary means of generating electricity. As of yet, however there does not seem to be any major R&D projects being publicized where micro gas turbines are being used in locomotives in the same way that they are in boats, airplanes, and cars. For more information on gas turbines in railroad applications, have a look at our previous article on the Birth, Fall and Resurgence of Gas Turbine Technology for Trains.
This concludes our series on micro turbines in transportation, thank you so much for following us as we walk through the different areas of transportation, and looking to see what the future holds for turbomachinery and transportation.
Want to be a pioneer for the next generation of turbomachinery in locomotives? Or do you have a concept for a micro turbine that you want to bring to life? SoftInWay can help! Reach out to us at email@example.com to discuss what you have in mind, and how we can work together to create the next generation of transportation technology.
- Abrams, A. (n.d.). Jet Powered & Other Futuristic Trains. Retrieved from Dark Roasted Blend: http://www.darkroastedblend.com/2007/01/jet-powered-other-futuristic-trains.html
- Amgueddfa Cymru — National Museum Wales. (2008, December 15). Richard Trevithick’s steam locomotive. Retrieved from National Museum of Wales: https://web.archive.org/web/20110415125004/ http://www.museumwales.ac.uk/en/rhagor/article/trevithic_loco
- Mennons, M. A. (n.d.). A new or improved construction of caloric engines. Retrieved from Espacenet: https://worldwide.espacenet.com/patent/search/family/001593795/publication/GB186101633A?q=pn%3DGB186101633A
- Morris, H., & Wetzel, D. (2007). The Flight of the M-497. First Internet Printing.