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Old 10-07-2008, 08:09 PM   #31 (permalink)
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Quote:
Originally Posted by jamesqf View Post
If indeed they are inefficient, then why are so many used in utility power generation? Sure, that's at a different size scale than an auto or light aircraft turbine, but if an IC engine were indeed more efficient than a turbine, then why are these applications not using large "diesel" engines running on natural gas, instead of gas turbines?

Because it is impractical to use a 56,000 horsepower diesel engine in the power industry. The power industry also uses the gas turbine's exhaust heat to provide heat to a HRSG (Heat recovery steam generator) to make LP and HP steam to power steam turbines. This would be called a combined cycle. THEN it all becomes more efficient if you look at it as an entire power plant, rather than just a single gas turbine. It's a little more complicated than that, but hopefully you get the idea.

Other reasons for aero gas turbines is that they can cycle loads quicker than frames or coal plants and can be used for frequency control of the grid, and be available as peakers.

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Old 10-07-2008, 08:24 PM   #32 (permalink)
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Originally Posted by 99metro View Post
Because it is impractical to use a 56,000 horsepower diesel engine in the power industry.
Why is that, exactly? Ocean-going cargo ships use bigger engines: Maersk Line shipping containers worldwide

Nor do I see any real reason why a diesel exhaust couldn't drive a combined-cycle plant as well as turbine exhaust.
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Old 10-07-2008, 08:30 PM   #33 (permalink)
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Originally Posted by Big Dave View Post
People do stuff for a reason, sport.
Sure, but sometimes the reason is "well, we've always done it this way", or "it's not worth the bother of changing".

For an aviation-related example, consider winglets. NASA developed these back in the '70s, and showed that they reduced drag, but it's only in the last couple of years that most of the 737s flying over my place have begun to sport them. How come Boeing didn't put them on 20 years ago, but the airlines are doing it now?
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Old 10-08-2008, 07:41 AM   #34 (permalink)
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Turbine car:
Who Killed the Gas Turbine Car? : TreeHugger
Chrysler Turbine Car - Wikipedia, the free encyclopedia

Gas turbine cogen versus Diesel Cogen? $$$$$ (installation and maintenance), weight, diesel has a bigger footprint, GT has a better power to weight ratio, emissions are better on the GT if steam or water injected, exhaust opacity. The largest diesels are in the 50mw range. Diesels are better for emergency backup power for telephone company buildings/hospitals or water treatment plants and not running as a cogen. Although small GTs like the Allisons 501K series can be used also in simple cycle (not cogen). I have seen 850kw Garretts used as cogens in colleges running 24/7. A lot of major industry businesses will run an aero or frame unit(s) for their own production or host site, and have an agreement with the utility to buy the extra electricity. Very seldom will anybody choose to build a diesel cogen. WAY too expensive. A LOT of marine vessels are going to Gas Turbines vice diesels due to their light weight and much better power to weight ratio, also ease of maintenance.
Worldwide | Main Menu

Getting a little off topic here - sorry folks.

I worked on a couple JFS turbines used to start a 2mw Allison gas turbine. They only last about 70 starts, then they are toast. Usually the compressor fails. That little turbine reminded me of the JFS (Jet Fuel Starter). I am primarily an LM6000 person these days, hanging out at a 5x2 the past 10 years. later
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Old 10-08-2008, 07:48 AM   #35 (permalink)
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I used to work on the Navy hovercraft (LCAC) in Virginia back when they were just coming out. They had some APUs (Sunstrand/Garrett) that would be an interesting install into a Metro...similar to this:

Garrett GTP30 Gas Turbine Engine
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Old 10-08-2008, 09:10 AM   #36 (permalink)
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here is the link i saw before about the Bio-d Turbine Hybrid.
Biodiesel turbine, super capacitor, series hybrid... HUMMER! (60 MPG and 0-60 in 5 seconds) - AutoblogGreen

Maybe with the right fuel change ( Bio-d) the efficiency would offset itsself as the overall carbon offset is a little better.

The physics of turbine engines are not as versitle as an automobile engine needs to be - so that will never be the "Pusher" of the car. But it does make an interesting "charger" idea for the batteries - you could have a rapid charge capability -but you would need a Hummer to power the darn thing.

Overall - large scale is more efficient - so charging from home using the existing grid would be the best from an Overall CO point of view and allow the large scale Wind / Solar plants to address the overall CO impact.

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Old 10-08-2008, 02:44 PM   #37 (permalink)
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Quote:
Originally Posted by Doofus McFancypants View Post
The physics of turbine engines are not as versitle as an automobile engine needs to be - so that will never be the "Pusher" of the car. But it does make an interesting "charger" idea for the batteries...
Which I think has been my point all along. Once you have a plug-in system with an electric motor driving the wheels, you have a lot more options for what to use to convert fuel to electricity, because you don't need starting torque, can tolerate long warmups, etc. You can look at turbines, Stirling engines, even fuel cells. Just because "we've always done it this way" doesn't mean that there aren't better ways.
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Old 10-08-2008, 07:00 PM   #38 (permalink)
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Did you ever bother to think there might be a reason for "well, we've always done it this way" or "it's not worth the bother of changing". Do you think hundreds of thousands of engineers and managers over the years are complete blockheads?

Gas turbine engines have a huge problem, regardless of nominal efficiency. Throttle them down and they still guzzle fuel at a rate very near that used at rated power. Jet engines fuel burn at idle is about 80% of that at rated output. One of the arguments for three engine airliners was that they could taxi on the center engine with the wing engines shut off until they got near the end of the taxiway. Considering the taxi times at some airports at some times this is not a small consideration.

A gas turbine to run a Metro would be in the 20-25 kwh range. It would have to be in a series hybrid layout, charging batteries that move the car. The turbine would run in short bursts charging up the battery and then shutting off.

The Metro was a volume car, sold at a low price. How much of an increase in MPG would be required to offset a huge increase in vehicle price? I fear that is what GM is running into with the Volt. A $50,000 commuter car will be as difficult to sell as a $40,000 pickup if not worse.

There is a saying in the auto industry: “Any knucklehead could build a Ferrari or Porsche if money were no object. It takes a genius to build a Model T or VW Beetle that makes money.” Like the VW prototype that gets 200+ MPG. Nice, but it costs $100,000. Is that worth the price of changing?
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Old 10-09-2008, 01:44 AM   #39 (permalink)
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Quote:
Originally Posted by Big Dave View Post
Did you ever bother to think there might be a reason for "well, we've always done it this way" or "it's not worth the bother of changing". Do you think hundreds of thousands of engineers and managers over the years are complete blockheads?
Managers, yes. I've dealt with enough of them :-) And quite often the reason for "we've always done it this way" is simple inertia, or the not-invented-here syndrome, or some other psychological quirk.

As for the engineers, most of them are not blockheads. Some of them get working prototypes of their ideas - the winglets are a prime example - only to see them ignored by management or marketing. Engineers built working hybrid & Stirling-engined powered cars in the '70s, along with many of the other ideas mentioned here. Management and marketing gave us the SUV instead.
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Old 10-09-2008, 04:06 AM   #40 (permalink)
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Quote:
Originally Posted by jamesqf View Post
As for the engineers, most of them are not blockheads. Some of them get working prototypes of their ideas - the winglets are a prime example - only to see them ignored by management or marketing. Engineers built working hybrid & Stirling-engined powered cars in the '70s, along with many of the other ideas mentioned here. Management and marketing gave us the SUV instead.
I have absolutly ZERO experience in this field, but I've read everyones comments.
You have to admit this is a very good point. Thinking outside the box is the only way to learn new ways of "this is how it's always done".

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