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Old 03-13-2007, 09:48 PM   #11
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Mostly Emissions

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Originally Posted by repete86 View Post
I just did come calculations and found that a container ship going 30 mph will get .00687 mpg! Sounds like container ship companies need to start coming here for pointers.
What places like the Port of Long Beach, CA are asking for is a limit on the emissions while at port. A lot of times the ships have to wait in a queue before entering the port area, and just simply idle for hours. Also, the emissions from these engines spew all kinds of particulates and NOx into the bay and blow into the populace. The trouble is: ships from all over the world are hard to regulate. Low-Sulphur fuel and a better catalyst filtration system would be great.

But, as mentioned by Ryland, the MPG per ton is also an important consideration. That's why it's more efficient to ship the containers on land via a Diesel-Electric trainset than one truck per container.
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Old 03-13-2007, 10:20 PM   #12
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Aeromod?
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Originally Posted by FormulaTwo
I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 04-04-2007, 08:47 PM   #13
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Opposed piston diesel

When it comes to opposed piston diesels I have really admired this one too.

http://en.wikipedia.org/wiki/Napier_Deltic

This is a clever bit of work.

Ernie
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Old 10-25-2007, 05:58 AM   #14
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Originally Posted by Sludgy View Post
I've seen HUGE Fairbanks-Morse opposed piston engines driving water pumps at the Charles River Dam in Boston. These engines have a simply outstanding 40% thermodynamic efficiency (base on the LHV of fuel) when turbocharged.

Here's a company making a smaller version:

http://www.dieseltech.cc/product.htm

The engine was designed for airplanes, so it's very light compared to most diesels.
Just curious. Why would anyone use a diesel engine on an airplane? Gas turbines are every bit as efficient these days (40+%), produce MUCH more HP/lb, are quieter, are vibration-free, and require MUCH less maintenance than a reciprocating engine.
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Old 10-25-2007, 09:35 AM   #15
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Originally Posted by BluEyes View Post
nucking futs!

If you want to see a massive diesel though, google worlds most powerful diesel or something like that. They're BIG guys used in commercial tanker ships. Turn at 100rpm making ungodly horsepower and torque and have something like 50% thermal effeciency in cruise mode.
And the bigger ones even have staircases built in the crankcases for servicing... crazier still is the fact they can burn the bunker sludge they are fed.
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Old 10-25-2007, 02:01 PM   #16
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Originally Posted by StorminMatt View Post
Just curious. Why would anyone use a diesel engine on an airplane? Gas turbines are every bit as efficient these days (40+&#37, produce MUCH more HP/lb, are quieter, are vibration-free, and require MUCH less maintenance than a reciprocating engine.
For general aviation anyhow, gas turbine engines in the form of turbo-props are cool, but use WAY more fuel than their av-gas burning counterparts.

A 320 ci engine burning av-gas can cruise at around 7 gph (maybe better even). Most gas turbine engines are eating something like 20+ gph.

And as far as I understand, most gas-turbine engines use Jet-A fuel - which is interchangeable with diesel.

If Lycoming made a diesel engine for GA, people could fill up with diesel or Jet-A, both of which are typically cheaper than 100LL.
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Old 10-25-2007, 03:20 PM   #17
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Originally Posted by DaX View Post
And as far as I understand, most gas-turbine engines use Jet-A fuel - which is interchangeable with diesel.

If Lycoming made a diesel engine for GA, people could fill up with diesel or Jet-A, both of which are typically cheaper than 100LL.
Or WVO. AFAIK, turbines can burn just about anything... Here's something about dropping a V10 TDI in a flying contraption of some sort.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 10-26-2007, 01:39 AM   #18
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Originally Posted by DaX View Post
For general aviation anyhow, gas turbine engines in the form of turbo-props are cool, but use WAY more fuel than their av-gas burning counterparts.

A 320 ci engine burning av-gas can cruise at around 7 gph (maybe better even). Most gas turbine engines are eating something like 20+ gph.

And as far as I understand, most gas-turbine engines use Jet-A fuel - which is interchangeable with diesel.

If Lycoming made a diesel engine for GA, people could fill up with diesel or Jet-A, both of which are typically cheaper than 100LL.
Then again, there are a couple of considerations here as far as efficiency. A 320ci engine like that found in a Cessna 172 produces a meager 160HP. But even a low-powered turboprop produces at least a few hundred HP - rarely under 500HP. These engines also tend to power larger and heavier planes. So given all these factors, fuel consumption is going to be higher. But it is SPECIFIC fuel consumption that matters. In other words, how many gallons of fuel per hour are you burning per hundred HP?

There are other factors as well. One MAJOR factor is the age and design of the engine. Early gas turbines were HORRIBLE when it came to fuel consumption. A typical early turborop/jet had an eficiency of around 15% (or so). So a plane using such an engine would tend to be a fuel hog. And since turbines last a long time, there are certainly ALOT of these older, less efficient ones running around out there. But even newer turbines can be guzzlers simply because a manufacturer might continue to build an older design. These older turbine designs tend to be cheaper to produce, since (1) there is no need to engineer a new engine, and (2) they use less exotic materials and less precise tolerances. They may guzzle. But at least they are reliable and proven. So the design continues to be produced. And these cheaper turbines tend to be used on lower powered turbines used on smaller and cheaper planes.

Speaking of low power turbines, another factor that reduces efficiency is the use of radial flow turbines/compressors vs axial flow. Radial flow engines are inherently MUCH less efficient than axial flow engines. And, as with older designs, radial flow engines are cheaper to produce. So they tend to find their place in ALOT of general aviation applications.

On the other hand, larger turbines used in airliners, like the GE CF6-80 series, are VERY efficient - around 40%. While it is hard to say how well the efficiency would scale down to a smaller size, it is certainly true that MUCH higher efficiency is possible even on smaller engines with design improvements. On the other hand, it would increase cost, which is probably why such improvements are generally not made.
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Old 10-26-2007, 05:51 AM   #19
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On the other hand, it would increase cost, which is probably why such improvements are generally not made.
You hit the nail on the head there - this is why consumer turbine engines typically use two stage centrifugal compressors. Even a TRS-18 uses a centrifugal compressor, but does have an axial turbine.

I do understand your argument about SFC, and it is true. I was just mentioning that you will be pressed to find a turbine that produces such small amounts of power. The airplane I'm building will use the O-320 engine that produces only 160 hp and will not break a sweat to see 180 mph. I do agree though, that GA engine technology is decades (over 50 years) old - it's time for a new breakthrough, and maybe someone developing a reliable, inexpensive, low operating cost turbine engine is the ticket.

The main reason we don't see tons of people running around in GA with turbine engines (and why companies aren't building them) is cost. The cost to own one is high, and the cost for repairs / parts is high. I work for a company that repairs gas turbine engines, and when I started, I was blown away with sticker shock. Companies don't bat an eye to buy an $85,000 part that you can hold in your hands. Service bulletins are often published with ways to increase engine efficiency even small amounts and the parts lists totals well over $1 million per engine. Granted, we are talking about 40K to 90K lb-thrust engines here. Even still, the TRS-18 parts are not cheap by any means.
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Old 10-26-2007, 07:05 AM   #20
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I do agree though, that GA engine technology is decades (over 50 years) old - it's time for a new breakthrough, and maybe someone developing a reliable, inexpensive, low operating cost turbine engine is the ticket.
Actually, it is not only GA engine techology that is old. It seems like virtually ANYTHING that is not either a commercial jet or an electric power plant uses antiquated and inefficient gas turbine designs. It is probably only because electrical utilities and airlines have so much money and are able to push engine manufacturers for more efficient turbines that such turbines exist (for instance, the GE LMS100 power generation turbine, which makes 100MW with 46% efficiency).

On the other hand, microturbines are a recent, interesting development. These small turbines often have power outputs of 100KW or less, yet have efficiency ratings in the 30s - despite using centrifugal turbines and compressors. They do, however, use regenerators (which heat the compressor outlet with the turbine outlet). And this is typically not seen in aircraft engines due to the size and weight. They are typically used for generators, but might even work well in cars. But ultimately, fuel cells are probaby a better idea for cars.

Of course, the REAL solution with turbines is materials that can take higher temperatures. As you probably know, increasing the pressure ratio increases power output (this is one area where centrifugal compressors fall short - they can't support higher pressure ratios). But higher pressure ratios make for higher turbine firing temperatures, which tends to melt turbines. Ceramics havebeen looked at for some time for this purpose. But they still tend to break. Oh, well.
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