Gas turbine

[dskira]

Do you think small gas turbine will have a future on a yacht?
Since they are extremly light for the power, I thouth it can be a good primer to run a generator. All that can even be on deck, so the maintenance and vents will be easy, and the electrical motor will be down below with direct shaft configuration.
I don't invent anything, it was done before.
I saw some turbine chopper second hand for sale. The good thing with turbine is you can use any fuel you can find.
Just a thought, nothing else
Cheers
Daniel

[Luckless]

One problem I've seen for most gas turbines is they tend to be extremely hungry on start up. (The M1A1 uses a turbine engine, one of the few examples I know of off hand of a mobile turbine not on a plane. It takes 8 gallons of fuel to start it before it produces power.)

It has been about 10 years since I looked at specs on them, but I remember they also had issues of dropping off in efficiency as you got smaller, and a small low powered turbine is actually more complicated than a large and powerful one. Just how much power do you need?

Generally you also put your generator inline on the same shaft as your turbine, as that is one design aspect that grants them such high levels of efficiency.

Also turbines tend to produce very loud and rather high frequency sound waves, which can be very hard to muffle as you will kill your engine performance if you produce a back pressure against the engine.

[dskira]

One problem I've seen for most gas turbines is they tend to be extremely hungry on start up. (The M1A1 uses a turbine engine, one of the few examples I know of off hand of a mobile turbine not on a plane. It takes 8 gallons of fuel to start it before it produces power.)

It has been about 10 years since I looked at specs on them, but I remember they also had issues of dropping off in efficiency as you got smaller, and a small low powered turbine is actually more complicated than a large and powerful one. Just how much power do you need?

Generally you also put your generator inline on the same shaft as your turbine, as that is one design aspect that grants them such high levels of efficiency.

Also turbines tend to produce very loud and rather high frequency sound waves, which can be very hard to muffle as you will kill your engine performance if you produce a back pressure against the engine.

I apreciate your thourough and professional comment.
I know nothing about turbine, it was exatly what I expected, a good and honnest opinion.
Thank you
Cheers
Daniel

[Submarine Tom]

Daniel,

As eluded too above, the transmission required to bring 90 000 RPM down

to a usable speed cancels out the weight advantage of the turbine.

An interesting aside, the queen ship of a fleet of three passenger only,

36 knot ferries ("CLIPPER IV") that run from here to Seattle (80 Nm) has

recently replaced the screaming turbines with diesels! I was quite

surprised.

-Tom

[hoytedow]

This thread was very informative. Thanks for the knowledge.

[FAST FRED]

The "modern" diesel has a problem in boat propulsion.

They are most efficient when very heavily loaded .

If loaded to run to the Mfg top RPM, when cruising they suck as the prop loading drops so rapidly with rpm.

A muiti speed tranny would be great for 2 common speeds and with a CPP might be able to pay its high cost , but probably never on a pleasure boat.

Electric , as in trains , is heavy and not efficient enough to pay the extreme costs of the gear , except in cruise ships with fantastic hotel loads,and AZPODS so they can dock with no tugboat bill.

What is needed is a variable DIAMETER prop (changing just pitch isn't enough).

OR an infinitely variable tranny at the same cost as a conventional tranny.

To the Drawing board!

FF

[mark775]

I have postulated this before. Step it down enough that a Synergy Drive can accept the RPM. VOILA! Continuosly variable transmission, generated electricy, heat, a boat light enough to offset the inefficiencies inherant in small turbines. I bought a wrecked hybrid Toyota Hilander at one point to test the system but the electrical was daunting and the wrecked Hilander was too valuable as a rebuild so I sold it. When people get over the current hybrid craze, I will continue with my testing.
By the way, If anyone thinks that they will bypass the surplus automotive planetary gear infinately variable transmission by buying an "electric wheel", http://technipowersystems.com/commercial-recreational-installations , guess again. These people are not very helpful and they want to make their children's college education from you, alone.
Helicopter turbines are ideal (ideal because the engines are expensive to rebuild, so they take them out and replace - not good enough for taking passengers in a flying contraption because of the flying hours but good enough for decades of trouble-free service in a boat), by the way - what engine did you find?
I have looked into micro-turbines and they are wrong for a host of reasons - http://www.microturbine.com/prodsol/products/index.asp but If you are comparing a range-extended piston ICE (30-35% efficient?) to a microturbine, then this comparison makes sense, but it should be pointed out that the Capstones do recapture waste-heat and have efficiencies up to the 40+% range for their larger turbines. With the smaller turbine size and multi-fuel operation, the application would be very compelling. All this assumes the turbine price could be competitive, which is unlikely - hence, the too-many-hour heli turbine but there is less done for you as far as heat re-capture (really making sence in northern latitudes) and the target for efficiency/ matching the right turbine to the right boat is even smaller.
Argue the efficiencies, if you will, but with the right match of boat and turbine and load the efficiencies are gained by by simply being lighter and a long TBO.
Salt ingestion means death for these, by-the-way.

[Submarine Tom]

A Bell 206 turbine puts out about 400 hp at 90 000 RPM and is about the

size of a bread box. It sucks back about 30 gallons an hour if my failing

memory serves me correctly and makes one hell of a racket.

-Tom

[Yellowjacket]

Lots of misconceptions here....

1. Turbines do emit noise if not properly installed. The noise is as noted, high frequency so it is relatively easy to address without much weight or backpressure. All you need to do is add dampening material to the ducting and make sure that the soundpath isn't totally straight and it will be very quiet.

2. Turbines do run at high speed, but not as high as some of you are thinking. The gas generator of the Bell 206 runs at 52,000 rpm, the output power turbine section runs at 33,000 rpm, which is geared down within the engine to 6,000 rpm.

3. The idea that the weight of the gearbox negates the weight advantages of the turbine is just silly. The Allison Model 250 in the Bell 206 weighs 158 pounds and that includes the gearbox to drop it down to the the 6,000 rpm output shaft speed, and the engine is rated at 420 hp. Show me ANY reciprocating engine of a similar power and output shaft speed that weighs 158 pounds and runs for thousands of hours and I will eat it.

4. A properly designed free turbine does not need a multi speed transmission or electric drive to operate in a typical high speed marine application. The power turbine acts like a torque converter and provides higher torque at low speeds. A turbine can turn a high pitch prop and still pull the boat out of the hole and run at high speeds, something that diesels have a lot of trouble doing.

5. Salt air isn't a big problem, most marine engines use a fresh water wash procedure to clean out the salt, and turbines can ingest a lot more water than a diesel without damage. This is more of an installation issue than an inherent problem.

6. Smaller turbines generally have higher specific fuel consumption than larger ones. That is changing. Expect in the not too distant future to see turbines in the 500 to 700 hp class that have fuel consumption within 10-15% of a diesel at high power.

7. Turbines burn more fuel at low power as compared to diesels, so it is more a function of how the boat is to be used that determines the suitiblity of a turbine for a given application. The higher fuel burn is partially offset by the substantially lower weight of the engine and transmission. That is, if you remove thousands of pounds of diesel engine, the boat is lighter, and at typical planing speeds will require less power to cruise, so even though the fuel consumption per horsepower is higher, the ligher weight reduces the power demand so that at some speed the turbine actually becomes more efficient that the diesel. If you look at 700 hp diesels, they weigh almost 3,000 pounds, compared to a turbine that will weigh around 250 pounds. That is a lot of weight savings. If you are moving a 50 foot hull at or over 35 kts the turbine is actually more fuel efficient.

As noted, the reliability and life of turbines far exceeds that of reciprocating engines, so in applications where they are used a lot there is a big payoff.

For conventional monohulls, depending on the fuel consumption, turbines start to make a lot of sense once you get above the 15-20m length and if you want to consistently cruise at or above 30 knots. Below that point the higher fuel consumption of the turbine makes it more difficult to justify, but there are applications where they make sense if you want to go faster (say consistently cruise at 40kts) or need to carry more payload. The larger and faster you go the more a turbine makes sense. Beyond 1500 hp (per engine) and over 30 knots cruise in a planing hull and you should be thinking turbines.

[Submarine Tom]

Yellowjacket,

I guess that's why we see so many of them around.

Here, there are about... hmm, lets see... gee... zero.

So that's a surprise. I wonder why?

-Tom

[mark775]

I am not going to pick the entire post apart because after he stated that there were "Lots of misconceptions here" he proceded to concur - only nobody said anything about a high speed marine application, and yes, brain-trust, salt air is a problem. That's why there is an installation issue.
You know, if I ever come across that way ("Lot of misconceptions around here", "I actually know something about the subject at hand unlike anybody that has commented on this thread.") would somebody give me a nudge? - because I just don't want to be an *******.

[Submarine Tom]

Well said 775, LOL

[Yellowjacket]

I am not going to pick the entire post apart because after he stated that there were "Lots of misconceptions here" he proceded to concur. only nobody said anything about a high speed marine application, and yes, brain-trust, salt air is a problem. That's why there is an installation issue.

Excuse me Mark, but how many years have you been involved in the design development and servicing of gas turbine engines?

I've been doing it for over 35 years in both aircraft and marine applications. I have been a lead turbine engine design engineer and program manager for a major turbine engine company and am currently program lead for an effort under contract to the Navy doing development work on an advanced turbine application. Before you even suggest for a moment that you have any knowledge in this area you should have the experience and the credentials to back it up. Otherwise you are, like many others on this forum, considerably outside of your experience base and are only advertising you lack of knowledge.

The original poster was trying to understand if turbines had a future in yachts. My point is that only in high speed applications do turbines make sense. If you are going to putt up and down the ICW at 5 knots go buy a diesel. If you want high speed get a turbine.

As to the issue of salt air, salt absolutely can build up on compressors, but it is also easily washed off. Most marine turbines have water washing ports installed so that a water wash solution can be introduced to the flowpath and the salt removed. It isn't a big issue, it is a maintenance item. And it can be greatly reduced with proper detail attention to the design of the installation so as to segregrate spray and keep it out of the engine inlet. Recent advances in barrier filters also allow the spray to be collected and much of the salt dried out in the filter element, significantly reducing the amout of salt entering the engine. The remaining salt that enters the engine is washed out in periodic maintenance. It is also dependent on the design of the engine, some engines are much more effected by salt air, other are not.

[Submarine Tom]

Yellowjacket,

Would you comment on why Clipper Transportation would have recently

removed the turbines from their 36 knot passenger ferries that run 80 Nm

four to six times a day and replaced them with diesels?

Also, why don't I see any turbine boats around here. There are hundreds of

internal combustion engined boats.

-Tom

[mark775]

It was obvious by your first post that you had been around turbines, Mr Anonomous "Lead engine design engineer", "for a major turbine engine company" , and equally obvious that you can be an *******. Now offer something constructive.

[apex1]

A muiti speed tranny would be great for 2 common speeds and with a CPP might be able to pay its high cost , but probably never on a pleasure boat.
FF

When will this nonsense end?

Every single time a CPP is mentioned, somebody comes out of his wood and makes the same, wrong statement.:mad:

We both Fred, had this discussion several times now, and you really should now better, now after having read all the related text!?:!:


To the Jet:

we had the Finnjet in Germany for about 30 years. She served the Lübeck Helsinki route all year round and could hold her 30kn cruising speed even in light ice conditions.
Her class was: 1A1 ICE-1A* Car Ferry A MCDK E0
She was the fastest Ferry in her entire life, and driven by two Pratt & Witney Turbines of 27.500 Kw each. The consumption was 360 tonnes in 24 hrs! For the turbines only!
She later got two diesels installed to make slower passages (especially in winter) more economical.
She had two KaMeWa CPP´s
Two years or so ago, she was wrecked in India.

Regards
Richard

[Yellowjacket]

Yellowjacket,

Would you comment on why Clipper Transportation would have recently removed the turbines from their 36 knot passenger ferries that run 80 Nm
four to six times a day and replaced them with diesels?

Also, why don't I see any turbine boats around here. There are hundreds of internal combustion engined boats.

-Tom


Tom,

I don't know enough about their application and use to venture a guess as to why they would convert to diesel, but a couple of things come to mind.

It could have to do with capacity and cost of overhaul. If they had run out the turbines they could be facing a big overhaul bill, and this is particularly true if they had already done a couple of hot section overhauls and were staring at the cost of essentially new engines. With a big tab for the turbines, they could make a case for diesels if their load factor was down and they didn't need the lighter engines. Also, some older turbines aren't that reliable, and are expensive to maintain with their hydromechanical control sysems, and the issue of support comes into it, how good was the support they were getting and how good were their mechanics? These kind of operators aren't like an airline, they just don't route in another boat...... Finally, two hour runs aren't the best thing for large turbines either. You see a lot of start/stop cycles in that usage and overhaul periods on some engines are based on stop/start cycles in addition to hours of use. I'm sure it comes down to the support and economics (and that could be short term economics as opposed to long term), they ran the numbers and made a decison.

The reason you don't see many turbines in general use is primarily because turbines cost a lot, and secondly that most yachts don't run fast enough for a long enough time for them to make sense. Most yachts putt up and down the ICW and seldom run over 15 or 20 kts outside even though the owners like to brag how fast they can run. Even big Bertrams typically cruise in the mid 20's so that they save fuel, even when they can run over 30 if they want to. At those load factors turbines burn more fuel than a diesel every time. Why spend more to burn more fuel?

While the next generation of turbines will have fuel consumption close to that of a diesel, they won't be cheap. About the smallest turbine you want to design, for a number of reasons is about 500hp, and you can buy a marine 500 hp high performance gasolline engine for about $20,000. Expect that a turbine of similar power will cost 8 or 10 times that. At 500hp per engine we are talking about roughly a 40 ft boat, and when the first cost is that much higher (and considering that they get used a dozen times a year) there isn't enough price elasticity to make it work. You still see a good number of gasoline engines in this class just because the cost is low and the boat doesn't get used that much (although buyers now are thinking resale value and buying the diesels even though they cost more than gas).

If you go bigger, and as I said, once you get over 1500 hp per engine, and if you want to go fast, turbines start to make a lot more sense. But really, ask yourself how many owners actually cruise a 75 to 80 foot boat at 35 or 40 knots and want to run about 100 gph of diesel thru each engine? The answer is really, precious few. They would rather make the salon bigger or outfit the boat with a nicer interior than have big speed. The reason there is a niche market in this power range is that if you are spending $3 mil on a boat, you can afford a $400k more to put turbines in there if you want them. The next gen of turbines will have first cost parity with diesels in this size class, so that may result in more sales, but really, how many fast eighty foot planing yachts get built each year? Not that many is the short answer.

For these reasons, while there is a niche market for a small number of big fast yachts, most of the marine applications for turbines will be in the military, where speed is life and the ability to haul butt out of a bad situation or carry a much bigger mission payload is a lot more important than the higher first cost or some wasted fuel. Patrol boats and special ops boats are where you will see them first and then they will filter down into the general public.

Will we see turbines in the 40 ft class? The answer is a few, but not many.

[Submarine Tom]

Yellowjacket,

Interesting, thank you.

-Tom

[WestVanHan]

As an aside I was fortuneate enough to go onboard the Wally 118 with a relative who knows Luca, the owner.

All I can say is stunning-I was so befuddled by it that 30 minutes later I dropped my camera into the drink.

I think there's about 16,000 hp from turbines and 800 from diesels.
From memory it uses 16 usg per mile,or about 40 litres per km at top speed.

[TollyWally]

20 some years ago a guy made a set on some herring and got the whole damn quota. He took that money and built one damn fast seiner. Triple motors if I remember correctly with the center one being a turbine. The mast folded down at speed to provide air to the engine room. That seiner did 50 mph. The fastest fishboat that ever came out of Pt. townsend, The Order Of Magnitude.

[mark775]

Atta boy! Nice post.
Tolly, Ray Wadsworth had it built. He lives here (well, Seldovia 12 miles away). The thing was a disaster. Cooked his fish, burned a $30,000 net, broke his mast, couldn't easily transform from cruise to sprint to fish, couldn't afford it. He's still around - with diesels. Yes, seiners can make some money, even today. Check out this vid http://www.youtube.com/watch?v=DV-Eju09Ios - kinda dorky but wait to the very end of the show. That's my friend Tom Stafford (F/V Infinite Glory) with 1,400 tons. This fishery is the first thing they do in a season and all of his crew quit immediately after offloading. He's building a new boat with the proceeds (that's the way seiners are!) and no turbines. Speed is incredibly important in this fishery, tho about once a year. Hard to justify those big MANs (or turbines) when you putt around 99% of the time...

[CDK]

The fast catamarans in my area are all turbine powered. I try to avoid public transport for various reasons, but the few times I went to the mainland with one of these 350+ passengers ferries, the absence of noise and vibrations kept surprising me.
There also used to be a "slow" car ferry with turbines, but after it was docked for maintenance, it never returned and was replaced by a Japanese boat.

But the original post mentioned a helicopter engine. That can never be a good idea because the amounts of air needed to keep the output section from burning out simply are not available in a boat's engine bay.

[mark775]

http://www.youtube.com/watch?v=gWSXJBE6iWY A perennial favorite, This Callan used the Italian Tencara hull - it would be smokin' fast if the output section were not burning out! The best of the vid is near the end when it imitates a router bit binding. I couldn't find the company that did the engines, but for interest, this company marinizes and does installs;
http://www.turbinemarine.com/turbine_extreme.html
One can shove more air into an engine bay than you can imagine - more air to the turbine than if it was mounted on the aft deck. Please check out scoops at end of vid.

[Yellowjacket]

But the original post mentioned a helicopter engine. That can never be a good idea because the amounts of air needed to keep the output section from burning out simply are not available in a boat's engine bay.

A helicopter turbine is simply a turboshaft engine. No different than any other turboshaft other than that some have magnesium gearboxes and you wouldn't want that in a boat. The Turbine Marine engines are surplus helicopter engines that have been marinized and they work just fine. Also some of the Vericor engines were maranized helicopter turbines, so where the engine came from isn't an issue, it is how it has been modified for marine use that is what is important.

All turbines need a lot of air to run. That is the nature of the beast. Making sure there is sufficient air without a large inlet loss is an important aspect of the turbine installation. Having too much inlet restriction will simply reduce the power available, it won't cause the turbine to burn out. No different than running the engine at altitude, where there is less air to start with.

You burn out the turbine if you run it too hot (which is easy enough to do if you are greedy or stupid and trick the fuel control) and ignore the turbine inlet temperature limits that are prescribed for the engine. If you ran a reciprocating engine above redline speed, would you expect it to last for very long?

The only bad thing about surplus helicopter engines it that they are cheap. That sounds silly, but they depress the market for new products that would be a lot better in terms of fuel consumption or reliability. With relatively inexpensive engines out there it is harder to bring new products into the marketplace. Right now it does appear that the supply of some of the Lycoming/Honeywell engines is starting to dry up and used engines as well as replacement part prices for those engines are climbing.

[TollyWally]

I didn't know that guy lived in Seldahoovia, I thought he was a Washington boy. I've always enjoyed Seldovia. It's a lot more than 12 miles away from Homer, it's a world away.

I know those herring seiners are that way about boats. There was a clan whose name escapes me now that had 3 high speed seiners built by Modutec. They bought the mold and Modutec built the boats. The only boat name I remember of the 3 was the Gore Point which I think was also a triple screw.

LOL it always had extra fuel drums lashed on deck. I have fond memories of an incident offloading in Seward. That boat came in and met the fuel truck, the skipper laughed and yelled up to the driver about being his favorite customer. While he was fueling a russian came in in their ignorant rude fashion and waked everyone at the dock. When the Gore Point left he did this tricky triple screw pirouette, got his stern right next to the russians beam and blasted him into the pilings. Didn't disturb the rest of us a bit.

[mark775]

The Cabana clan. I fished for blackmouth with Larry on the Silver Beach a couple days ago.
By the way, the one that had triples (it was the Gore Point) was hardly faster than the ones with twins. They are all three just twins now with tiny John Deeres.
'it's a world away" - kinda like Fox Island to Gig Harbor. Kick Dixie when you go by!

[powerabout]

there are a few dozen turbine pleasure boats in the US now, mainly 50' cats and as a replacement for a pair of 1000+hp big blocks they are a proposition.
Google Al Copeland Jnr, he's building a 4 engined big cat to claim the prop driven record which is about 220mph which the boat will do easily or should I say capable of..

[Jimbo1490]

A helicopter turbine is simply a turboshaft engine. No different than any other turboshaft other than that some have magnesium gearboxes and you wouldn't want that in a boat. The Turbine Marine engines are surplus helicopter engines that have been marinized and they work just fine. Also some of the Vericor engines were maranized helicopter turbines, so where the engine came from isn't an issue, it is how it has been modified for marine use that is what is important.

Yes, there have been several turboshafts 'marinized' over the years including the (somewhat hated) Lycoming T-55 (think Chinook & Bell 214B) and the (definitely hated) T-53 (think Bell 'Huhey' series and USCG Dauphins), and the venerable Pratt & Whitney PT-6, to name the more common ones


All turbines need a lot of air to run. That is the nature of the beast. Making sure there is sufficient air without a large inlet loss is an important aspect of the turbine installation. Having too much inlet restriction will simply reduce the power available, it won't cause the turbine to burn out. No different than running the engine at altitude, where there is less air to start with.

Google "Andy Granitelli Turbine Indy Cars" to see a real world case of intentional restriction of the inlet to reduce power. (Even with only 24 "^2, he was still lapping everyone, that's when Indy pulled the plug on turbines :D )


You burn out the turbine if you run it too hot (which is easy enough to do if you are greedy or stupid and trick the fuel control) and ignore the turbine inlet temperature limits that are prescribed for the engine. If you ran a reciprocating engine above redline speed, would you expect it to last for very long?

'Hot Starting' is the usual way turbines get overheated
though that is easy enough to avoid most of the time by making sure the starting battery and motor are up to snuff, and the operator allows the engine to obtain sufficient RPM before adding fuel and spark. The auto start systems avoid all this, though which is more than likely to be part of a marine installation.

Over heating through straight-up overloading is an issue with helicopters, though as the FCU will respond to an overloaded (too heavy) vehicle by adding fuel to keep RPM in range. Digital engine management (mostly) prevents this kind of thing now. Probably less of an issue with a propeller in water, especially fixed pitch.


The only bad thing about surplus helicopter engines it that they are cheap. That sounds silly, but they depress the market for new products that would be a lot better in terms of fuel consumption or reliability. With relatively inexpensive engines out there it is harder to bring new products into the marketplace. Right now it does appear that the supply of some of the Lycoming/Honeywell engines is starting to dry up and used engines as well as replacement part prices for those engines are climbing.

I bought a Allison 250 C-18 for $1200.00 (Mil. surplus auction) in 1995. It just had a slipped O-ring in the gearbox and was pulled and mothballed with only 50 hrs, TSO. A friend helped me split the gearbox and then all was good. I intended to put it in a Fiero, and had just about all the engineering worked out.

But then a guy with an airboat came along and offered $10K, and I really needed the money at the moment so...

Now there's this really cool turboshaft powered airboat that runs around on Central Florida lakes:D

Jimbo

[TollyWally]

Hell Jimbo that turned out well. Sold for a profit when you needed the $ and LOL who knows, might have saved your life. I can only imagine my life would be hanging by a thread toolin around in a turbine powered fiero. Sounds like the batmobile!

[Dave Gudeman]

Yellowjacket, you say that gas turbines are only better than diesels in high-speed applications, but what about other applications where small size, light weight and low maintenance are more important than fuel economy?

For example, Rick (http://www.boatdesign.net/forums/profile/rick-willoughby.html) is planning to build a boat with wind turbines and electric motor. If I were doing this, I would want a backup generator that is capable of driving the boat at good speed when there is no wind. But a diesel generator has several disadvantages --not only size, weight and maintenance, but also the fact that the fuel shouldn't be allowed to sit for too long. Would it be reasonable to make a very small gas turbine that runs off of propane?

I would want a fossil-fuel backup for cooking, heating, and water heating, and propane is better than diesel for those purposes. If you could run your generator off of propane, you could get by with one backup fuel system instead of two.
Also, propane has an unlimited shelf life.

You can modify a gas engine to run on propane, but the savings in weight and maintenance (over a diesel) is not that great. I'm thinking that a gas turbine engine would take up no significant weight and space and that the engine could be mostly ignored when it wasn't in use. You would expect lower efficiency but it is only for occasional use so that is not a major concern.

Just idle speculation. Any thoughts?

[Yellowjacket]

Dave,

Small simple cycle gas tubines (think of a big turbocharger with a combustor on it) are pretty inefficient. You would likely see specific fuel consumption of about .8 pounds per horsepower hour in a machine like that. With a direct drive generator on it, it will weigh about 30 pounds and imagine that turbocharger with a starter motor for a typical v8 sticking out the end of it and the whole thing spinning at 90,000 rpm. The exhaust is going to be hot (probably about 1100 degrees F) too. If making 30kw and burning somewhere around 6 gal per hour is acceptable then it can be done, but it won't be cheap, probably around $20k for a machine like that.

Small gas tubines can be pretty efficient if you use heat recovery (regenerators or recuperators) to caputre the waste heat. These tend to be bigger and more expensive so that does tend to negate the advantages of the small turbomachinery. If you look at something in the 30kw range, the turbomachinery is very small (again think like the size of a truck turbocharger) and the heat recovery package will fit in a two drawer file cabinet and the whole thing could weigh about 200 pounds. The fuel efficienty would be about 3 to 3.5 gph for 30kw (which is better than a spark ignition engine and close to that of a diesel) and expect it to cost around $30k. In terms of weight and volume, probably a lot better than you can do with a diesel of that size and if you wanted to run propane, gasoline, fuel oil, diesel, or good booze (although that would be a waste of good booze) you could do it.

Just remember that running off of propane is going to result in a pretty big tank if you are sucking 3 gph out of it. If you want less power (like 10kw) then you could get the fuel burn down to about 1 gph, but still, at 1gph and if you want to run for 10 hrs that's a pretty good size propane tank.

[dskira]

Dave,

Small simple cycle gas tubines (think of a big turbocharger with a combustor on it) are pretty inefficient. You would likely see specific fuel consumption of about .8 pounds per horsepower hour in a machine like that. With a direct drive generator on it, it will weigh about 30 pounds and imagine that turbocharger with a starter motor for a typical v8 sticking out the end of it and the whole thing spinning at 90,000 rpm. The exhaust is going to be hot (probably about 1100 degrees F) too. If making 30kw and burning somewhere around 6 gal per hour is acceptable then it can be done, but it won't be cheap, probably around $20k for a machine like that.


If it's accurate it will be worth to put the whole generator/turbine not down below but on deck protected by a superstructure. It will make the vents and salt filtering easier, as also the maintenance.
The noise can still quite high in this configuration.
As I said before, I don't know nothing about turbine.
I just try to check several solution for genset. Just pocking :p
But a lot of you knows al lot about it, thank you for all the infos.
The salt filtering, mentioned by AdHoc, can be in fact the most difficult factor since filtering will restric the air intake.
For the exaust, up in the air like a gigantic smoke stack can be the solution for the safety of the crew.
The gear box is the biggest problem I think. It is what fail the most in chopper.
Cheers
Daniel

[Yellowjacket]

A machine like this won't have a gearbox.

The alternator is on the shaft and runs at shaft speed (90k rpm). All the power comes out of the alternator. The alternator would be a permenant magnet alternator, so there are no windings rotating at that speed. The power output electronics to chop the output are pretty big and clunky, but they are pretty much state of the art. If you want DC to drive a motor or charge a battery, then they are a lot more simple. Look up Capstone turbines to get an idea of what we are talking about here. With a heat recovery system the output temperature is 600 F, hot, but not horrible, and certainly not as hot as diesel exhaust when running at full bore.

[powerabout]

Dave,

Just remember that running off of propane is going to result in a pretty big tank if you are sucking 3 gph out of it. If you want less power (like 10kw) then you could get the fuel burn down to about 1 gph, but still, at 1gph and if you want to run for 10 hrs that's a pretty good size propane tank.

Speaking of large fuel tanks...
LNG carriers have been turbine powered in the past, just burning off the boil off.
Now that gas costs lots more they are putting reliquidation plants on board and putting old slow speed engines back

[dskira]

A machine like this won't have a gearbox.

The alternator is on the shaft and runs at shaft speed (90k rpm). All the power comes out of the alternator. The alternator would be a permenant magnet alternator, so there are no windings rotating at that speed. The power output electronics to chop the output are pretty big and clunky, but they are pretty much state of the art. If you want DC to drive a motor or charge a battery, then they are a lot more simple. Look up Capstone turbines to get an idea of what we are talking about here. With a heat recovery system the output temperature is 600 F, hot, but not horrible, and certainly not as hot as diesel exhaust when running at full bore.

Thanks for the Capstone link. I didn't know that kind of turbine and utilisation existed. they don't say realy much, but I will investigate for sure by calling them.
Cheers
Daniel

[mark775]

Yes, thanks for the Capstone link!

[Yellowjacket]

Be careful with the Capstone unit with regards to marine usage. I only pointed it out to show what a unit of this size class would look like.

It has air film bearings in it that are ill suited to the marine environment (salt would kill them) and they are really best suited for stationary usage because they cannot withstand any severe impacts....

[Submarine Tom]

Here you go, a helicopter turbine propelled vessel:

http://www.rib-kali.com/kali-engine.php

-Tom

[Submarine Tom]

Here you go, a helicopter turbine propelled vessel:

http://www.rib-kali.com/kali-engine.php

-Tom

Evidently, the turbine has already been replaced by an outboard...

-Tom

[Yellowjacket]

Not at all surprised that they would do that, trying to run around England isn't a good fit for that particular turbine when you consider the higher fuel burn. It all comes down to fuel burn versus time versus installed weight.

If you look at the power to weight ratio, that particular turbine weighs about 158 pounds and provides about 300 hp at a cruise power setting, but has a specific fuel consumption of .7 pounds per horsepower hour. A 4 stroke outboard weighs 500 pounds, has 250 hp and has an sfc of aout .52 lbs/hp-hr. If you replace the turbine with an outboard, you will be burning 132 lbs/hr of fuel for 250 hp where the turbine is burning about 175. So for every hour you are running at high power the turbine is burning 42 pounds more fuel. The outboards will weigh 600 pounds, so the weight difference is on the order of 370 pounds (figuring 50 or so pounds for a prop and prop shaft and another 20 pounds for the increased tankage). If you are going to be running for more than 9 hours between fuel stops the outboards will have a lower overall propulsion system weight (engines + drives + fuel and tankage) and that is what is important here.

You might be able to make the case that the average propusion system weight will be lower with the turbine since once you start to burn off fuel the overall propusion system weight will actually be lower, and you can gain speed from that point on, but that probably isn't the biggest driver here.

As I said in an earlier post, turbines really don't make sense until you start looking at larger sizes (bigger turbines have better specific fuel consumption so the fuel burn isn't as big an issue) and you aren't trying to go all the way around England (30 hours of running). The bigger the engine, the shorter the mission and the faster you want to go the more turbines make sense.

[Submarine Tom]

Well that's certainly confusing Yellowjacket.

Can't say I really get your point.

I do wonder why they designed it with a turbine in the first place.

Here's a question you may be able to answer more clearly though:

What lead to the demise of the Bell-47? That was the name of the piston

workhorse wasn't it?

-Tom

[Jimbo1490]

There was nothing 'wrong' with a Bell 47; it was a great helicopter in its day. But many different technologies incorporated into helicopters have 'moved on', making the Bell 47 simply obsolete. One of these is engine technology. The 47's all came with piston engines from Franklin and later Lycoming. The latest Lycomings were the best, but none were very reliable or durable in a helicopter. One of the best 'service life extenders' for the Bell 47 has been the Soloy Turbine Conversion:http://www.joeyrhodes.com/greg728004.jpg

which adapted the ubiquitous Rolls/Allison 250 series engine to the Bell 47 airframe.

The other major obsolete component of the 47 was the rotor hub, which used the 'old school' type of greased ball joint bearings and passive servo type controls. The French in particular were at the forefront of replacing these with elastomeric mounting of the blades. Except with the heaviest helicopters, the entire industry has adopted this technology, making older designs less attractive due to their higher maintenance costs.

The basic form of the 47 lives on in the Aerospatiale (Eurocopter) Alouette:

http://www.army.mod.uk/images/central-panel/aac_haf_alouette_410.jpg
and Llama:

http://cdn-www.airliners.net/aviation-photos/middle/7/1/0/1337017.jpg,

both of which look superficially like Bell 47's with turbines, but in reality are much more advanced designs WRT main rotor hub and blades.

Bell wants NOTHING to do with the model 47, BTW and wishes all the remaining ones would just disappear :(

Jimbo

[Submarine Tom]

So, power to weight was the biggest issue?

[Yellowjacket]

Tom,

What I was trying to say is that a turbine, although it is a very light engine, doesn't always make sense. You have to look at the weight of the engine and fuel as a total propulsion system weight, and then see if it works for your mission. I did the quick look in about 5 minutes, and it didn't look to me at first cut that there was a pony in that pile if they are trying to run around the UK. If the mission is three hours, then a turbine would save a bunch of weight and might be a good idea. The smaller the power requirement the less turbines make sense. That's all.

As to the demise of the Bell 47, that happened directly as a result of the development of small turbine engines, specifically the Model 250 Allison engine that was developed for the Army LOH program which, although the Bell 206 lost that competition, it got the Jet Ranger program off the ground. When you look at what the payload of the 206 is (1487 pounds) compared to a 47 (482 pounds), it is obvious that the 206 is another whole world of capability compared to a 47. The 47 was really a post-WWII aircraft based on the power available at the time (150 hp recip) and they learned a lot between then and the early 60's when the 206 came along with the turbine. The fact that the 206 has been in production for over 40 years when the 47 was built for only 10 tells you something.

Bell outgrew the 47 and didn't see a future in small piston helicopters which is why Frank Robertson (who worked for Bell and saw the market for a small helo that he couldn't get Bell to build) went out and did the R22 on his own, and as they say the rest is history. There still is a helicopter that does what the 47 did, it is just called the R22 and Bell doesn't make it, although they probably wish they had listened to Frank in the first place.....

[Yellowjacket]

Bell wants NOTHING to do with the model 47, BTW and wishes all the remaining ones would just disappear :(

Jimbo

Very true, in fact I did read the other day that Bell has sold the type certificate for the 47 to Scott's Helicopter. They were one of the main support houses for the 47 and did a lot of spare parts business on that model.

They can finally wash their hands of it and to them that is a good thing. With the staute of repose in place in a few years it will be only a memory at Bell.

[Submarine Tom]

Thank you YellowJ and Jimbo, very interesting indeed.

-Tom

[powerabout]

Didnt HeliMusters in OZ have about 30-40 47's 20 years ago?

Re piston to turbine , no contest if its flying, about the only thing a piston can do is have a bit more instant grunt, no turbo lag you could say.
PS I'm a Hughes man myself..how could you ever fly in a chopper with 2 blades! after that I guess its French but I had many fantastic memories in 500's skiing in NZ, stunts that I have not yet seen in a Hollywood movie

[Submarine Tom]

Turbo lag - nothing a good pilot can't compensate for.

[Jimbo1490]

The modern helicopter airframe is the *perfect* match for a gas turbine engine. Light helicopters would never have become so popular as they are today without the gas turbine engine. That being said, it's interesting to see how the definition of 'light' vs 'utility' helicopter morphed over the years because of the turbine engine, and how the model 47 was left obsolete as a result. When the 47 was introduced, it was considered a utility helicopter, with an impressive payload. With the introduction of the 206 in the late 60's, the 47's payload was no longer impressive. Larger engines and rotor blade upgrades helped the 47 keep up somewhat; the 'Big Blade ' conversion 47's even had a greater payload than a 206B. But in the end, the 47 was a 'bare bones' airframe, VERY noisy and without a 'real' cabin. It had the old style dynamic system and an increasingly high-strung piston engine also, both negatives.

That last place the original light versions could still find commercial success was in pilot training and the heavy converted airframes all went to crop dusting. When the R-22 came along, it far cheaper to run so it made MUCH more sense as a trainer, which obviated the need for most of the 47 fleet. Advances in crop dusting airplanes obviated the need for most of the heavy conversions as well.

Bell could've done a turbine version like Soloy did, but then you're still stuck with the old rotor hub and controls. They could have transplanted the Bell 206 controls (like Soloy did) but you still have the old hub. Even replacing the hub, you still have no real cabin, which limits what you can do with the thing. And in the end it would have to compete with the Eurocopter Alouette and Llama, not something Bell would be thrilled about. The world already has all the turbine powered 'bubble' 'copters it needs, so why make more :(

Jimbo

[powerabout]

Doesnt the 206 also have a wierd engine to rotor clutch whereas the H500 has a sprag like everyone else?

[Jimbo1490]

All the helicopters (I'm aware of) powered by the RR/Allison 250 lack a clutch of any kind, as the engine is a 'free turbine' engine. The Bell 47 had a sprag clutch.

Jimbo

[powerabout]

here's one from way back
Never made it to production

[powerabout]

here's 2 of 4 in one boat
These T55's will go faster in this boat that any chopper ever did!
( ok ones out of view)

[apex1]

May I inform you peers, that the thread opener Daniel Skira decided to quit his membership on this Forum!

Repeated personal attacks by some of our well known drivel and destruction experts, made him decide to leave.

We have lost a well respected NA with a sensible hand for drawing classical beauties.

A man of good temper and a sense for harmony and nice behaviour.

It is a pity that such people are pissed off here by two or three internet rowdies.

Regards
Richard