TheEEStory.com

http://newenergyandfuel.com/http:/newenergyandf...

Any guess on how much continuous power might it generate ?
As for efficiency: 70 deg exhaust gas temp, that's really low for such a small unit; any guess on possible efficency ?

People have been making gas turbines this size for years and using them to power model aircraft. I believe the basis of these designs is usually a car turbocharger. They are generally started on propane then switch over to kerosene.

I don't think the outlet temperature is necessarily a good indication of its efficiency. You can lower it significantly with bypass air as is done in somewhat larger 'Trent' range of Rolls Royce turbofan engines used on many wide-bodied jets these days. From the point of view of safety, it is not a bad idea to have a low output temperature in a unit like this.

It is the turbine outlet temperature that you need to know to establish efficiency of the engine proper.

I love the idea of it!
Yes, yes!
Firebird III here we come (expect it will be electric).

This in combination with a suitable electric storage could allow light aircraft general aviation to become affordable, again.
As a charging system supplementing a smaller required electrical energy storage it would give that top-up, "extra time in your tanks".

Like Tec says it is depends on the units efficiency, as well as how long it will operate before overhaul or failure under a variety of operating/starting conditions.

It would be nice to have a compressor bleed-air port for heat/ pressurization, but probably more effective to have a separate electrical compressor/ heat source or an exhaust heat exchanger instead, given the units small size.

I'm not sure I understand what point you are making here.

simply this,

replace the ICE in small aircraft with electric, and flying for many becomes much more affordable,

for many flying is not just time in the air drilling holes,.

A micro turbine capable of recharging an electric aircraft opens up a whole lot of fun and utility, and saves a hell of a lot of cost related use/maintenance/overhaul of that gas engine.

...replace the ICE in small aircraft with electric...

I don't think this is very practicable. I don't think you can carry enough energy to stay aloft for long, and its not as if you can simply pull over when you run out of juice is is.

Wouldn't it be easier to recharge the batteries from the mains on the ground anyway? I doubt whether this thing has much of a power output, and do you really want a portable gas turbine in the cabin with you whilst flying? I don't think I'd be awfully keen on it. It will surely emit copious quantities of carbon dioxide and possibly carbon monoxide too, just for fun.

I understand too that the adapted turbochargers used as jet engines are not terribly reliable and blow up dramatically after a few dozen hours. This is hearsay. I've only seen one or two flying and they seem OK.

There is also a lunatic who straps a couple of these to his back attached to a short wing, then leaps out of planes and flies significant distances using them. I think he flew over the english channel like this some time back.

It looks ridiculous and must be a freezing cold as well as deafening experience. I don't think Airbus is worried about the potential loss of customers anyway.

WATTS?!!! HOW MANY WATTS!?

Tec,
Patience young Jedi,

fortunately most pilots are aware of the fuel and reserve requirements for safe flying, time in your tanks as we say. You perhaps are not.

"I don't think this is very practicable."
yet.
you're right of course, but that is the essence of this whole blog of B'S. Energy Storage. why most are here.

"recharge the batteries from the mains on the ground anyway?"
again what a great idea, glad you thought of it. perhaps similar to refueling on the ground. electricity much cheaper ,too.

" do you really want a portable gas turbine in the cabin with you whilst flying? "
NO except on Buffalo Joe's lockheed electra(Ice Pilots history channel?)
might raise a safety issue or two, dangerous goods etc. Do you really see this happening? I don't, anymore than putting in the cabin the APU in that dated BAE 146 I used to fly. Damned APU was always running out of oil, due small resevoir. It's not broken, it's British!
sorry TP.

"I don't think Airbus is worried about the potential loss of customers anyway."
What does this have to do with small aircraft and electric motors, used for recreation and general aviation purposes.

have a nice nap tec.
make sure you wake up on the right side of the bed, next time.

What does this have to do with small aircraft and electric motors, used for recreation and general aviation purposes.

None. It has to do with the original thread. Small jet engines.

If you can strap them onto your back and fly around, it might well affect small aviation and general aviation I'd have thought.

more to the point,
...small jet engines generating electricity...

Hey, Generic, thanks for the article! That is an interesting development.

But I'd feel more confident about what the article claimed if it didn't have such confused statements as this one:

Turbines are external combustion and can offer more thermal efficiency than internal combustion such as piston and cylinder engines.

Turbines can achieve greater efficiency than piston-powered engines do, but-- at least according to everything I've read-- internal combustion engines are more efficient overall than external combustion engines.

If external combustion engines were more efficient, we'd still be using steam engines in our automobiles.

Tec wrote:

I don't think the outlet temperature is necessarily a good indication of its efficiency. You can lower it significantly with bypass air...

Good point, Tec. Another indication that the writer of that article didn't know enough about the subject to write an authoritative report on this tech.

Heres a video of one running. It seems to be gobbling fuel at the rate of knots.

http://www.youtube.com/watch?v=ZhdZLGTP-2w

If you're interested in jet engines and how Rolls Royce produce them you may find this worth watching. Theirs are somewhat larger.

http://www.bbc.co.uk/programmes/b00t0yx9

I don't know if people outside the UK can see this. Its an unashamed plug for RR. I understand there are other - lesser - companies in the world that make something along the same lines. GEE or G I think they call themselves!

Lensman wrote:

Turbines can achieve greater efficiency than piston-powered engines do, but-- at least according to everything I've read-- internal combustion engines are more efficient overall than external combustion engines.

Well, perhaps a micro Stirling engine might be a better bet.

I would not expect high efficiency from a miniature gas turbine.

What about this?

http://web.mit.edu/newsoffice/2006/microengines...

Its pretty old now. I wonder what happened to it? Another lab. promise that didn't work out I suppose.

WalksOnDirt wrote:

Lensman wrote:

Turbines can achieve greater efficiency than piston-powered engines do, but-- at least according to everything I've read-- internal combustion engines are more efficient overall than external combustion engines.

Odd, everything I've read agrees that external combustion engines are more efficient. They are expensive and lacking in torque, though.

Not saying you're wrong, but I'd be curious to know what your source(s) of information are.

The first thing I found on the subject by Googling was this:

An internal combustion engine has higher efficiency than external combustion engine:

The efficiency of steam engine is only about 20% whereas an internal combustion engine can have efficiency up to 40%.

(source)

I presume that refers only to engines of approximately the size you find in cars and small or medium-sized trucks, because I know that some large marine (ship) diesel engines are up to about 51% efficient, and steam engines used in utility grid power plants are ~33% efficient.

Tec wrote:

Well, perhaps a micro Stirling engine might be a better bet.

I would not expect high efficiency from a miniature gas turbine.

Stirling engines are generally used in a closed cycle system (the exhaust [edit] working fluid [/edit] is recycled, not vented) and produce very limited power. It's easy to produce high efficiency in a closed cycle system, but generally speaking the power output is very limited. (Obviously not true for nuclear power plants.)

At any rate, I don't think a closed cycle system is suitable for the applications in question.

Last edited Fri, 24 Feb 2012, 2:45am by Lensman

Lensman wrote:

WalksOnDirt wrote:

Odd, everything I've read agrees that external combustion engines are more efficient. They are expensive and lacking in torque, though.

Not saying you're wrong, but I'd be curious to know what your source(s) of information are.

The first thing I found on the subject by Googling was this:

An internal combustion engine has higher efficiency than external combustion engine:

Last edited Thu, 23 Feb 2012, 7:56am by WalksOnDirt

WalksOnDirt wrote:

This link suggests that Stirling and Diesel engines are about the same. Time marches on, I suppose.

Thanks, WoD. Hmmm, I thought that a closed-cycle system like the Stirling could achieve greater efficiency than a diesel engine, but I guess that isn't true.

Last edited Fri, 24 Feb 2012, 2:39am by Lensman

The working fluid is not vented - ever - in a stirling engine so it doesn't actually have an exhaust in the sense of a gast turbine. It just needs a heat source which might need a chimney of some sort.(If you used a radioactive source like Sr₉₀ it wouldn't need an exhaust at all!)

They are extremely efficient and high power ones are perfectly feasible. Here's a 5HP one http://www.youtube.com/watch?v=XpqhX_66n18

Here's a domestic CHP system using one. It looks relatively compact to me. http://www.whispergen.com/main/technology/

I've seen a design for one where there was no rotary generator. Instead the piston contained a powerful magnet, and the cylinder incorporated coils so the power was generated directly with no rotary motion. It was designed to phase lock to mains frequency. Unfortunately I can't find the reference. Perhaps it didn't work out for some reason. That too was intended for domestic CHP and if I remember rightly would probably fit into a medium sized suitcase.

I think I'd prefer this approach to a turbine screaming away at 100,000 rpm and burning fuel like there was no tomorrow.

Lensman wrote:

BTW-- You kinda mixed up who you were quoting in your last post-- you or me.

Tec wrote:

The working fluid is not vented - ever - in a stirling engine so it doesn't actually have an exhaust in the sense of a gast turbine. It just needs a heat source which might need a chimney of some sort.(If you used a radioactive source like Sr₉₀ it wouldn't need an exhaust at all!)

Yes of course. With a small one, I'd hope a fan and ambient air might do the job.

EEasyflyr wrote:

This in combination with a suitable electric storage could allow light aircraft general aviation to become affordable, again.
As a charging system supplementing a smaller required electrical energy storage it would give that top-up, "extra time in your tanks".

Like Tec says it is depends on the units efficiency, as well as how long it will operate before overhaul or failure under a variety of operating/starting conditions.

It would be nice to have a compressor bleed-air port for heat/ pressurization, but probably more effective to have a separate electrical compressor/ heat source or an exhaust heat exchanger instead, given the units small size.

I'm told gas turbine engines HAVE been successfully used for powering aircraft. Not housed in a suitcase however, and without the generator battery and motor.

Gas turbines are internal combustion engines.
Small jets are less efficient than bigger one.

Tec wrote:

I'm told gas turbine engines HAVE been successfully used for powering aircraft. Not housed in a suitcase however, and without the generator battery and motor.

Last edited Thu, 23 Feb 2012, 9:37pm by Y_Po