Gas Turbines?

[pdf27]

Originally Posted by motion30

a turbine engine generates a lot of heat how would you deal with that?

See above - these ones seem to generate electricity roughly as efficiently as diesel generators. That means both will generate the same amount of heat per unit of energy produced.
You're probably thinking of big gas turbines, which generate a lot of heat - and a lot of power too. Cut the power output and the heat output will drop too...

[Cheechako]

I think the real question is how to collect that heat... a diesel collects it in a water mix and sends it out the back at low temp. Can a turbine live with the exhaust restriction?

regarding noise... so a turbine takes in a lot of air, compresses it, shoots it through a venturi and it exits the back at high speed right? doesnt that create alot of noise regardless of size...? Maybe not I suppose if the engineering and testing gets all the parameters right to reduce sound/harmonics and still maintain power...?

I've built exhaust parts for jet turbines down to as small as a little over 2 foot diameter. Those companies seemed to be going through a lot of those exhaust parts due to harmonic/sympathetic vibrations and heat of course....

[pdf27]

Originally Posted by Cheechako

regarding noise... so a turbine takes in a lot of air, compresses it, shoots it through a venturi and it exits the back at high speed right? doesnt that create alot of noise regardless of size...? Maybe not I suppose if the engineering and testing gets all the parameters right to reduce sound/harmonics and still maintain power...?

True where you're using the hot gas for propulsion. In this case you don't put the gas through a venturi, instead you use the hot, high pressure gas and use it to turn an extra turbine, which turns a generator. That keeps peak speed below Mach 1, and should keep the noise down.
Remember, all forms of internal combustion engine use the Suck-Squeeze-Bang-Blow cycle.
- Jet engines extract the power to do the squeeze from the bang, and the usable power from the blow cycle.
- Piston engines and turboshafts like this extract all their energy from the bang cycle, making the blow cycle a lot quieter as less energy is involved.

Originally Posted by Cheechako

I've built exhaust parts for jet turbines down to as small as a little over 2 foot diameter. Those companies seemed to be going through a lot of those exhaust parts due to harmonic/sympathetic vibrations and heat of course....

Their 70kW (100 hp) unit has a 4" exhaust, so the energy levels in the harmonics should be lower. Additionally it uses air bearings, which should help in reducing transmitted vibration.
**IF** they ever get it usable for automotive use, those problems must be solved and the reliability will be excellent. If not, it'll never be cheap enough to use anyway!

[Cheechako]

pretty interesting stuff... I see no reason the mini sholudnt work... unless maybe at some scale the density of air gets to be a problem!

[Sailmonkey]

at what point does sucking in dog hair become problematic?

[cfarrar]

Even small turbine APUs, designed to spin a generator and provide bleed air for pneumatics, have noisy exhaust. You'd need an innovative muffler - preferably underwater - before you'd be welcome in an anchorage. Oh, and the compressor intake isn't exactly quiet, either.

A real upside would be the availability of bleed air for instant cabin heating, hot water, etc. However, this introduces fire danger from a bleed air leak, so automated fire systems would be a must.

[roverhi]

The noise and exhaust of a turbine can be taken care of. Believe it was Chrysler built a few prototype turbine cars back in the '60s. Nothing came of it probably because the cost of the turbine among other things. I question whether they'll be able to get the cost down to where it would practical for the average boat owner. There will always be the cost be damned owners but that's a small group of people. Think the turbine would work best as a generator power source in a hybrid power system. Generators require the engine to run at a fixed rpm which can set up for the sweet spot in a turbine. Perfect engine for a small generator package and the can use the exhaust to blow on the sails.

[Group9]

Originally Posted by roverhi

The noise and exhaust of a turbine can be taken care of. Believe it was Chrysler built a few prototype turbine cars back in the '60s. Nothing came of it probably because the cost of the turbine among other things. I question whether they'll be able to get the cost down to where it would practical for the average boat owner. There will always be the cost be damned owners but that's a small group of people. Think the turbine would work best as a generator power source in a hybrid power system. Generators require the engine to run at a fixed rpm which can set up for the sweet spot in a turbine. Perfect engine for a small generator package and the can use the exhaust to blow on the sails.

There was nothing wrong with the turbine powered Chrysler car, either. The program just got cancelled when Chrysler got the contract to supply the same engine to be used in the M-1 Abrams tank it built for the army, and the engine and everything about it was classified as secret.

http://www.allpar.com/history/military/M1-tanks.html

http://www.allpar.com/mopar/turbine.html

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Bleed air is unlikely to be plausible - a Marine Spey produces 26,000 hp on 65 cubic metres/second of air. A 100 hp unit would consume ~0.25 m^3/sec of air (~9 cubic feet/sec), with only a small fraction of this available. These really are very small units.

Finding noise data is rather difficult - the best I can find is for Capstone, who make similar units. Their 200kW unit emits 65 dB @10m (full power).
Beta Marine say that "Our marine generating sets are manufactured with high quality marine grade acoustic housings that reduce the noise levels down to below 60dB(A). This is (at least) a further 10dB(A) reduction from our already quiet gensets", which suggests that a turbine genset probably isn't significantly noisier than the average generator. They also say that "Acoustic Canopy: a substantial, quality zintec / steel canopy with a 40mm sound insulated lining and removable panels for easy maintenance; the noise level will be less than 58dB(A) when measured at 7 metres under “free field” conditions.". To me this suggests that a gas turbine unit may even be inherently quieter than the diesel equivalent.

[model 10]

[QUOTE=roverhi;1272589 Perfect engine for a small generator package and the can use the exhaust to blow on the sails.[/QUOTE]

Surely you jest? You could blow on the sails too for all the good it would do.

[cfarrar]

Bleed air is unlikely to be plausible - a Marine Spey produces 26,000 hp on 65 cubic metres/second of air. A 100 hp unit would consume ~0.25 m^3/sec of air (~9 cubic feet/sec), with only a small fraction of this available.

There are many small APUs for commercial and military aircraft that simultaneously spin large generators and provide bleed air for air conditioning or engine starts. Some of these produce as little as 20 shp. The fuel consumption is still outrageous compared to a small diesel generator - think 20 gph instead of .2 gph! So I think what you're envisioning is something that's at least a whole order of magnitude smaller and more efficient.

[pdf27]

Not particularly envisioning - that's published data, and they aren't alone - Capstone produce several units with 25-30% thermal efficiency running on diesel fuel. Having said that, their units are enormously heavy - I suspect they're including a lot of other extraneous stuff. Their range extender unit isn't all that heavy (perhaps twice the weight of the Bladon unit), and gets similar efficiency.

[cfarrar]

Impressive: the Capstone C30 provides 29kW from about 3.2 gph of diesel fuel. That's getting close to the efficiency of a reciprocating diesel engine, with much less weight.

[pdf27]

Looking around further, Lotus have a petrol-based piston range-extender engine capable of producing electricity at 260g/kWh and weighing 200 lbs for 35kW (50 hp).

Right now that isn't suitable (diesel, not petrol/methanol is needed), but given that it's half the weight of the equivalent marine diesel and despite the lower compression ratio is getting the same fuel economy I would think that a diesel derivative should be lighter and more efficient than current units.

Thinking about it, yacht gensets for hybrid-electric use have a lot in common with UAV engine requirements - must use heavy fuel, be small and light and ideally quiet. A but of looking around did show this unit (45kW at 350g/kWh at sea level, 305g/kWh at altitude so economy could probably be improved quite easily).

There are a number of other potential units about, the problem being of course that all the really interesting technology (like this stuff from Cubewano) is coming from small companies and may never be built.

[nimblemotors]

Turbines are simple in theory, the tolerances and materials required make them very expensive, and at the RPM they run, failure is catastrophic.

Rotary engines generally are the most compact and lightweight, inexpensive, and are being used in UAVs. I've heard there are developments to use them for hybrid cars.
Low emissions is not their strong suit because of the flat and moving combustion chamber, but I've read direct injection can improve on this.