A different kind of train

So I read the article on "How Diesel Locomotives Work" from Howstuffworks and basically came to the conclusion that the limiting factor in the power generation comes from the low rpm of the diesel engine.

But in the case of passenger travel, most of the locomotive models by GM and EMD aren't even designed specifically for such purposes thereof.

I also read an article about the finger-pointing going on between Amtrak and Bombardier, the latter of which is a Canadian company designing a newer 5000 HP locomotive based on 'jet turbine' technology. It seems to be a revival of the old Union Pacific designs of the 1950s that were eventually decommissioned because of the rising price of bunker C oil.

Is jet turbine the only way to pack enough power density into a locomotive? I mean, most of the railways in North America aren't electrified because of the demographics so we have to adapt to make this technology feasible.

Suppose you put a really powerful radial engine with an electric generator. Then that would avoid the efficiency problems from the jet-turbine design because it can be turned on and off more readily at stations.

 

Log in or Sign up to hide all adverts.

Facial,

Single-Unit prime mover diesels are up to 6000 HP now.

http://www.answers.com/main/ntquery...rtab=2222_1&sbid=lc03a&linktext=EMD SD90MAC-H

Turbines are very expensive and complex compared to diesels.

Why do you assume a radial engine is any better than a diesel? Large diesels can have thermal efficiencies as high as 43% - which is much better than most spark ignited gasoline engines. A big factor when producing that much power for long amounts of time.

The limiting factor with any large reciprocating engine is stress in (strength of) engine components. Think of how much the pistons weigh and how many times they change directions in a second. That's a lot kinetic energy which translates to a lot of stress in the connecting rods.

There are diesel engines in ships and as prime movers in power plants that produce 20 or 30 thousand horsepower but they'll have engine speeds of 400 rpm or so.

Still make a sh_t load of power!

 

Log in or Sign up to hide all adverts.

How about a fuel cell that uses hydrogen to get the electric motor to pull the train?

 

Log in or Sign up to hide all adverts.

Fuel cell technology is just not there yet. Still very big physically for reletively low amount of power output.

EMD's 2-stroke diesels are hard to beat.

 

What happens when fuel is so high priced that only the rich will be able to pay for it? What also happens when we pollute ourselves to death with emmissions from diesel and gas? Hydrogen should be given a fast track to implementation quickly.

 

Economic inertia is the main problem. We have a petroleum-based world. But once fossil fuel gets costly enough the big oil companies will have to really start the push to move to alternate fuels like hydrogen.

The way I understand it now, hydrogen's limiting factors are:
- not easy to store (very explosive in a fuel tank)
- takes a fair bit of energy to produce it... and where does THAT energy come from?

 

Nuclear power can give us the power to make hydrogen,

 

the only good train is a "power train" ... that and the dagafeed... which I think is a train also.

 

LOL... gotta applaud the Dagafeed.

So perhaps the 2-stroke diesel is the most efficient around.

I have another idea.
Since making mechanical gearboxes directly to connect to wheel axles is deemed impractical, why not use a planetary gearset from the slow output of the diesel engine that doesn't have too many gears (like 10-15) and instead connect it to the electric motor? I just h8 the rpm limitations that come from such a powerful engine as this.

A larger rpm input to the motor results in better electrical conversion and higher voltage, right?

 

But your gearset idea still doesn't change the speed the engine runs at.

You can certainly transmit large quantities of power through a gear set but losses are sizeable because of the physical size of the parts needed to handle that much power.
Also the gear set would be very costly to make and impractical. This is why large amounts of power are often transmitted electrically in very large machines.

It's all a matter of scale. The 200 - 600 hp diesels that run on-highway trucks are all driving mechanical transmissions because it makes sense to do so. Generators are too big and heavy for that application even though they'd be more efficient in power transmission.

To answer your last question, you can control the output voltage of the generator through construction of the generator (# of windings). So for a diesel operating at say 1800 rpm (common gen. speed) you could construct a generator to make any voltage that is convenient (480V in the USA, or 600V in Canada for example).

In general you are right, the higher the voltage the lower the current for a given amount of power. By limiting the current you limit resistance losses (heat) in the conductors.

The efficiency of the generator is a function of a number of factors but typically a large commercial generator that would be coupled to a large diesel engine experiences about 95% efficiency when running full load.

Of course, DAGAFEED would have an efficiency of over 1.0 (a thermo-dynamic impossibiliy) but the laws of physics don't apply to DAGAFEED!

 

People should design a diesel-powered passenger locomotive that goes beyond 140 mph, because our demographics don't make electrification feasible on the most stretches of Amtrak routes. It ashames me that only electric trains such as the TGV ICE or Shinkansen can run at super-high speeds like 220mph and above, and what? the speed record for a diesel is roughly the same as a steam-powered? It doesn't make sense.

So to begin with, what needs to be attacked besides the engine? I suppose the axle friction of the wheel can be addressed somewhat. And the streamlining- definitely streamlining the nose more.

People need the idealism of DAGAFEED. Rofl

 

Aerodynamic drag increases as a squared function with velocity. You need a LOT more power to get a marginal increase in speed as you get going faster and faster.

It's a real benefit if you can create the energy needed remotely and then have a system to retrieve it and a relatively light-weight motor to deliver it onboard the train. (read: electricity)

Otherwise you have the weight & bulk of the diesel engine (or turbine), fuel, generator, and traction motors all onboard the train.

This is why high speed trains are generally electric. It's just good engineering sense.

And yeah, magnetically elevating the train so that there is no friction lost to the wheels/rails is pretty cool but lifting a 6,000,000 kg freight train would consume a lot of power.

 

IMO, trains are just outdated. They're dangerous, inefficient, and slow. The only reason why thier use is continued is because:

1. There are some places only accessable by train and it would be more expensive to build a road...

2. All the rails are already built, and the government would be criticized greatly for disallowing thier usage...

3. It provides a more direct route for the transfer of goods.

 

tell that to europe, trains are a bloodline there. I used to be able to hop on a train station in my town there, and go ANYWHERE in europe on either traditional rail cars or high-speed ICE trains. I didn't even pay that much, as opposed to if I drove there.

But then again, we're talking the same people that don't mind driving Smart cars (cars smaller than Minis, no joke). Over here in America, not only is the land area huge, but people buy cars of compensating sizes and use them all the damn time, even if the local metra rail can get them there faster and cheaper. It's more materialistic over here, unfortunately.

Plus, in the near future, and assuming projects to create syntheticly produced fuel oils fall through, all-electric train systems might not be a bad way to get around, or go cross country. no bathroom breaks, no filling the tank, just relaxation as you crank along at 100+mph non-stop from new york to los angeles.

 

Trains can move a lot of heavy material much more efficiently than a corresponding number of highway trucks. Two massive locomotives vs. a couple hundred 6-cylinder diesel truck engines.

Plus, getting those semis off the road would make the highways safer for motorists.

 

^^^Such is the reason why freight lines are operating to this very day.

California is pondering its own highspeed rail line, and I am in full support of it. The demographics make the project economically possible, and would serve as a great benefit to inhabitants of the southland/bay area like myself.

 

Then, why is it that I never see diesel locomotives streamlined like the Shinkansen 500 series? Doesn't that reduce the coefficient of drag a lot (decreasing the a in the ax^2), especially eliminating it for the lower speeds of a diesel?

I would suppose that the enormous of weight of a diesel does pose a challenge, but then again I would say that tweaking all sorts of aspects concerning friction (MoS, teflon, graphite superlubricity ?), efficiency (on-board superconductors/refrigeration), and power density (flywheels, capacitors ?) would be a better investment for a new kind of super-fast diesel locomotive for a budget under 14 billion dollars (which is the estimated cost of California's proposed line) is a much better bet, don't you think?

 

BTW Flunch, are you the author of the HowStuffWorks article? Just curious. No offense if you aren't.

 

Facial - no I'm not.

The reason north american diesels locomotives aren't very streamlined is probably because they don't move fast enough to make it worth while. Also there is no effort made to make the train a seemless, smooth body like there is for a high speed passenger train. The gaps between cars will add a measureable amount of drag too. (There are 2 types of aerodynamic drag, pressure and frictional). There will be a big difference in drag between say 60 mph and 200 mph for the same body moving through air.

I still say the best bet for a super-fast train is to produce the power at a stationary plant and transmit it to the train (via electricity) so you only need motors and not the extra weight of the power-producing equipment aboard.

 

Thank you for giving me a good laugh. Recently I have begun using the train for my commute to work. Here is a pros and cons comparison for a week.
Car
Total transit time: 9 hrs 10 minutes.
Discretionary time: Zero
Exercise time: Zero
Cost : £40
Safety: 1 chance in 500,000 of a fatal accident
Train
Total transit time: 7 hrs 30 minutes.
Discretionary time: 4 hrs 10 minutes (i.e. relaxing on train reading a book)
Exercise time: 2 hours (i.e. walking to and from office)
Cost : £32.50
Safety: 1 chance in 6,000,000 of a fatal accident

Dangerous? Inefficient? Slow? I rather think not.