Jet Trains of Tomorrow With New Techology?

Trains Magazine General Discussion
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This, says Dr Lior, eliminates the need for the two sets of static blades. That means an OCN engine can be built more cheaply with fewer components. It would also need to be only half the size of a conventional jet of similar power, says Dr Lior. The engine would use at least 25% less fuel and, he claims, its emissions of carbon dioxide and nitrogen oxide would be cut by three-quarters because of its unique ignition properties.

http://www.economist.com/node/16909889

Being largely ignorant of Physics and Mechanical Engineering, is there an expert in the house?

Given the historic hype and failure to embrace turbine locomotives, would this make any difference? High output efficiency versus fuel consumption at rest comes to mind as an issue. Would this design address the economics of universal applications?

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Turbine engines have and will be in the near future fuel hogs unless operated at high altitudes. I highly doubt there is one in the railroad’s near future.

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Turbines work most efficiently at full RPM, at idle or low RMP they just eat up tremendous amounts of fuel.

UPs experiment with the Big Blows didn’t end because the turbine failed to do or perform as promised.

It ended because the fuel used, #6 fuel oil, ended up becoming more expensive than they wanted to pay, (other industrial uses cut into the supply, raising the cost) the infrastructure to service the turbine also became less cost effective than wanted, (ya can’t run over to the gas station and fill up on #6 heating oil) and the traffic pattern in the area where they could most efficiently be used changed.

A turbine would make sense in freight service if it was used in a manner that best allowed it to perform to its full potential, that is a high speed non stop run with a huge train.

Anything else is a waste of the turbines efficiency.

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Recuperation solves the part load fuel consmption problem with gas tubines. CNG or LNG also solves a fuel cost problem . Diesels won’t work on pure natural gas. The best turbines for lcomotives are aircarft derivitive. They have never been recuperated because they don’t need to be in airplanes. Another poinnt, gas turbines do not not need to be left idling. They will go from shutdown to full power in 90 seconds. Don’r get me srarted-

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How about intermodal service on transcon routings? Put a backup motor on the unit to keep air pressure when the turbine is shut down.

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Another factor that caused the demise of Union Pacific’s Big Blow was the noise – the only place they could be used was out across the desert because they were as loud as a 747 on takeoff.

In one video I have the narrator says there were many cities they could not be ran into without being arrested because of the noise level they emitted.

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Amtrak’s RTL turbos were not that much louder than diesels (the gas turbines themselves were smaller units than the UP GTELS had)…

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I remember them as being almost stealthy quiet.

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The MIT Press recently published a book by Vaclav Smil entitled Prime Movers of Globalization. It discusses the contributions that diesel engines and gas turbines have made toward a global economy. There is almost no discussion of railroads (because they don’t span continents); however there is a tremendous amount of information about the use of those two forms of propulsion in other applications.

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The RTL’s used aircraft derivitive gas turbines, one 850 kW (1139 hp) in each power car. One of these was later replaced with a 1200 kW (1609 hp) unit for improved fuel economy. The large unit could handle the whole train with the smaller unit fired up just for accelearation, at least that was the intent. The RTLII used two 1609 hp gas turbines. The RTL’s were quiter than any diesel. There was a venturi in the exhaust pipe which helped ventilate the engine compartment but also added volume to the exhaust, reducing noise as well as temperature.

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The idea sounds intriuging and the question comes to mind why haven’t the gas turbine manufacturers thought of this before, or better yet, why haven’t the air forces thought of this before?

From what I remember about gas turbines from graduate school is they are constant speed machines, and they are most efficient at full throttle; in fact there is very little difference in the fuel consumption from full throttle to low speed.

Considering that the Union Pacific stabled 30 gas turbine electric locomotives, and it used them in freight service for nearly 20 years I would hardly consider them as experimental, especially since they were highly reliable. The gas turbine locomotives were rated at aywhere from 8500 to 10,000 horsepower. When the gas turbine locomotives first went into service in the early 1950’s their horsepower was equivalent to four or five diesel freight locomotives. But one of the resons they were phased out was higher horsepower diesel freight locomotives such as the GE U 50C (5000 horsepower) and the DD 40 (6600 horsepower) became available.

Gas turbines were also used to power passenger trains, the United Aircraft Turbotrains and the ANF-Frangeco/Rohr Turboliners which were not as relable as the Union Pacific’s gas turbine electric locomotives.

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The only thing that is relevant about the UP’s turbines is that they did what they were supposed to do. All the tales about noise even if true, are totally irrelevant. They were a spectacular case of bad timing. They first gas turbine generator was in 1939 so the technology was in it’s infancy. Their existance was dependent on a fuel that was changing from a byproduct to a premium feedstock due to the introduction of new petroleum cracking technology.

The noise will always be there and it’s not the exhaust alone. You could remove the exhaust noise entirely and the noise from the turbine itself is well beyond the threshold for ear protection. And J. piers i will differ with you on the startup . An aircraft engine is designed with as little mass as possible which allows the entire engine to heat up rapidly. A locomotive engine or powerplant engine does not have to fly and benefits from the rigidity and vibration damping properties of increased mass. This makes it very hard to go to operating temperature rapidly without uneven expansion of the engine which results in high maintainence and short life. In short it is best suited to constant full power operation.

The UP turbines would have been much better engines 10 years later but the fuel situation was still changing. They would best be compared running on the same fuel and in that light they don’t stand a chance.

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re: this OCN engine. They say they need a bigger partner to develop it. If it had any promise wouldn’t their respective governments be interested? If Israel and Russia aren’t big enough then who is?

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Bombardier built one on their own. They took it on a tour of the USA and Canada. They couldn’t sell a single one. It now lives in a museum.

http://transportation.bombardier.com/en/1_0/1_10/1_10_3_4_5.jsp?menu=2_3

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an orbiting combustion nozzel turbine has one problem that is not addressed in any posts. What kind of materials are going to be used in the combustion chamber??. It will be really hot in the chamber. On present this generation turbines the turbine inlet temp is limited to about 975 degrees C. with cooling airflow around the combustion chamber. 975 is about 300 degrees hoter than the B-727, DC9 aircraft;s JT-8s . How much hotter is it in the actual combustion chamber with a rotating turbine???*

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Are turbines better at direct drive hydraulic or electro-motive transmission?

What kind of gear reduction has to be achieved for each mode, and what are the advantages of each?

I was surprised to learn that many turbine locomotives were direct drive hydraulic and not electro-motive.

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@ aegrotatio :

H****ydraulic torque converter plus geared transmission have mainly been used to save mass . Torque converters have a profile of efficiency that declines with increased relative difference of input and output rpm (to keep torque converter working near range of best efficiency in automobile industry the trend is towards ever more speeds in automatic transmissions) . In contrast to earlier applications of electric ‘torque conversion’ and transmission , present-day synchronous motors , besides being perfectly suitable for electronic anti-slip control and providing an inherently elegant engineering solution for transmission of power from primary engine to powered axles in trucks - by electricity instead of mechanical gears and drive shafts - are much lighter , more compact and more powerful at the same time , which would ideally suit a gas turbine as primary engine because of its potentially higher output as compared with a diesel engine . As has been noted by others before , aspects of fuel and thermal efficiency generally tend to favor the diesel engine , however if it were for exceptionally high demands of power ou

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To Juniatha: It’s interesting you mention engine-to-drive energy conversion using electricity. The French Saint-Chamond medium tank of World War One did exactly that. It was a lot easier to drive the tracks with electric motors than it was to build a complicated mechanical transmission system to do the job. It made the tank very easy to drive. Also, in the 1940’s the Public Service Trolley system of New Jersey ran what they called ASV’s, or All Service Vehicles. These were buses that ran on electric motors powered by gasoline engines, or from overhead trolley wires as needed. Looks like there’s nothing new about hybrid vehicles! And of course the great French liner “Normandie” was a turbo-electric design. Steam turbines generated electricity to power the propeller shafts, again much easier to build than a complicated gearing system.

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First off, as a former airline pilot I can say that there was one inaccuracy in this thread - earlier someone said turbines become more efficient at altitude - that is incorrect. Aircraft are more efficient at high altitude because the air is thinner so there is less resistance - in actually there is also less power coming out of the turbine.

Turbines product the most power at sea level and cold temperatures. The colder the better. Really, it comes down to air density, or something called density altitude. Increase the density altitude and you will get less power out of the turbine.

So why aren’t turbines used on RR’s? Well, they are a LOT more expensive than diesels. And FYI there are aircraft that run on diesel engines too. However, turbines have a much higher power to weight ratio than diesel engines do.

Basically, in any internal engine you have 4 phases - intake, compression, combustion, and exhaust (such, squeeze, bang, and blow).

In a diesel, these 4 all happen sequentially. Hence a 4 stroke engine. In a turbine, the 4 happen all simultaneously and continuously. Therefore, your power to weight ratio is a lot higher.

Also, FYI for measuring power in turbine, there are a number of different factors, typically it’s measured by either the TIT (turbine inlet temperature), ITT (inter-turbine temperature), EGT (exhaust gas temperature), or N1 speed (low pressure turbine speed percentage). The limiting factor in any turbine is the TIT, turbine inlet temperature. Depending on the manufacturer of the turbine, max continuous TIT’s are typically 900-1000 degrees C.

TIT is also was makes a turbine efficient - the hotter the TIT, the more efficient it is. But you can only make it so hot until you get metal distortion, so really it’s a materials limitation.

But, as I mentioned earlier turbines are a LOT more expensive than diesels. For aircraft, that makes sense. Weight is a big issue in aircraft, so airliners need a power sour

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Add to that , that on railroads, dust and metal fragments are a BIG issue, with amount of air a turbine uses, its hard to filter the intake air.

The dust and particles, do significant damage to the turbines, and severly shorten Turbine life.