Gas turbine power units

sarabande

sarabande

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apologies for starting a separate thread, but following Beadle's opening shot about fuel types, I ferreted around and it seems there is renewed interest in gas turbines as power plants for trucks.

http://www.ttengines.com/homeflash.html

is from Turbine Truck Engines who have some seriously advanced models available for trucks.

Given their advantageous power / weight ratio (<2lbs/hp) , and the lower costs and consumption of the fuel, what IS stopping development in the boat world (apart from the out and out racing fraternity, of course !)
 
Probably the cost of the fancy alloys needed to withstand the high temperatures plus the fact that weight isn't critical in a cruising boat unlike an aircraft. Possibly, also, it may difficult to downsize gas turbines to 20-40 bhp output because tolerances become so fine.
 
From what I recall the Rover motor company tried to produce a gas turbine powered racing car in the sixties. The two problems they encountered was:-

1. The time lag between opening the throttle and the power coming through. This meant when negotiating a corner the driver would throttle back and brake then before coming out of the corner the throttle was applied again, and hope to god that the car was out of the corner when the power surged again. This long lag time would be less of an issue for a cruising boat.

2. The other problem was the exhaust. Again you do not get many people walking past the exhaust on a boat.

However The more recent gas turbines are efficient because they are triple spool engines with high bypass ratios. Which will make them expensive to produce, and what to do with the high bypass.
 
Most cars have much more power than that let alone trucks.

The problem with motor vehicles is that turbines have a considerable lag and lack the flexibility of a petrol engine. A diesel, particularly a truck engine has a much narrower power band than a petrol engine and so are more easily replaced by a turbine. Leyland experimented with a turbine powered truck in the 1960s - dunno what happened with it. Probably they went on strike.

But here it is:-

http://www.roadtransport.com/blogs/big-lorry-blog/2008/06/one-of-six-built-the.html

Suppose the other issue would be tax - the fuel consumption costs in when you pay the ludicrous levels of tax se have on petrol and diesel. Doubtless if people started using kerosene as road fuel that too would quickly be taxed to the point where it ceases to be economic.

In the small quantities used in power boats it probably would'nt be picked up on the Cyclops' radar.

EDIT

I must learn to type faster
 
"The more recent gas turbines are efficient because they are triple spool engines with high bypass ratios. Which will make them expensive to produce, and what to do with the high bypass. "

This is used in aircraft engines where the by-pass flow provides thrust. In a mechanical application you would simply omit the fan and use the power that the fan absorbs as output power (SHP)

I think.
 
The third spool was added to increase the compression ratio of the engine from approx 14-1 up to 20-1. The reason is that the thermodynamic efficiency of an engine is closely related to it's compression ratio. Which is the main reason why diesel engines are more efficient than petrol.
 
As I understand it turbines have a much greater fuel consumption than reciprocating engines.
( triple spool engines with high bypass ratios is applicable to jet engines on aircraft but not to turbo shaft engines) In turbo shaft they may have 2 spools ie free turbine for power output and one for driving the compressor.

Yes gas turbines are very difficult to down scale to 40 HP. The smallest gas turbo shaft on aircaft is still around the 300 HP. Even at that size the compressor must run at 50000RPM to get the compression using centrifugal comperessors. Like wise the turbines rotate at similar speeds.

So turbo shaft engines are very successful in aircraft because they function well at high altitude with thin air. Even then they are not good for fuel consumption at low altitude. They are good in helicopters for high power to weight ratio despite high fuel consumption.

Some years back there was an American company promoting conversion of Beech Kingair PT6A turbine aircraft to a highly turbocharged piston petrol engine for better fuel consumption.
I don't imagine it was as good as promoted but does point to fuel consumption being a problem in turbines.

They are used successfully in war ships where the primary power comes from diesel but with one or 2 gas turbine of several thousand horsepower that can be cranked up fairly quickly when needed for huge increase in total power with little weight. But with huge fuel consumption penalties.

They didn't mention that when the HMAS Adelaide was despatched to rescue Tony Bullimore in Southern Ocean that they also despatched a fuel supply ship to refuel the Adelaide so it could get home. Having wasted all its fuel in gas turbines to get down there in a hurry.

Likewise a few years back I went to Isle of Wight on hovercraft. I was intrigued to find it running on diesel engines. Fuel consumption being more important than the added weight,

Gas turbines will burn almost any fuel. However I was also intrigued to find at the airport that diesel ground power units were run on Jet A1 (Kerosene) fuel drainings from the aircraft. I don't know if they added oil for more lubrication of pumps etc.

I don't think we will see gas turbines in boats or cars in the near future. Perhaps in trucks but I can't see that being popular either. olewill
 
McClaren tried a GT in a road car, years ago. It was scrapped for one reason, a GT doesn't provide any engine braking, so the brakes constantly cooked.
I think the same problem would still exist today, even with modern Ceramic or Carbon Fibre brake Rotors.
 
Rover´s gas turbine version of their road car used to be in the science museum (still is?) and they also fitted a 160bhp unit to a BRM chassis for Le Mans. Lotus nearly won the Indy 500 until a small bearing failed.Used one in F1 too. Lag and brakes were always the prob. More interesting for us was a workboat with a smaller outdrive I saw at the LBS in the 60s. Cost and consumption (esp. if taxed) will always favour diesels. Those russian hydrofoils also use diesels (noisey ones too) a clear case for a light powerfull GT. The Boeing Jet foils in the channel were GT-didn´t last long either.
Andrew
Re engine braking: I believe it is no longer taught in driving as our brakes are so much better than the 60s minis et al. I learned on. I don´t think F1 cars with their carbon brakes use the engine to slow down. And most automatic cars don´t either.-A
 
salt air and the alloys used in most GT are not compatible.

there have been small gts with limited output, I recall one used in a portable fire pump, and doubt that was much more tan 50 bhp.

The noise is very intrusive.

exhaust is still a problem in boats. I recall that the GT patrol boats used to have to dock using their diesel loiter engine. On one occassion in Gt Yarmouth when they neded to run up their GT alongside, they asked a yacht astern to move, and the response was very obnoxious, so they achieved a wet start (which is where some unburnt fuel is ejected from the exhaust during the start process, and then ignites) which did not do te boat astern a lot of good!
 
i used to work on solar turbines, made in san diego CA, they used to make tiny turbines as a matter of course. the 4000 hp ones i worked on were smaller than a 16 cylinder cat engine which wasnt that big!
Stu
 
see my previous post, solar gas turbines, 4000 hp driving gennys and hi pressure pumps, 50 miles offshore angola, and i know most production platforms and drill rigs use gas turbines, so what is the prob with alloys and sea air?
stu
 
some rather sweeping statements there old boy, went on board hms sheffield in the 70s, 2 olympus engines, same as concord were main power, didnt see any diesel propulsion engines.
stu
 
[ QUOTE ]
see my previous post, solar gas turbines, 4000 hp driving gennys and hi pressure pumps, 50 miles offshore angola, and i know most production platforms and drill rigs use gas turbines, so what is the prob with alloys and sea air?
stu

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Nothing - if they are designed for it!

Plus your air intakes are much higher (thus less spray)
 
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We used to use portable gas turbine fire pumps on warships,dont know anything techy about them exept they were dam noisy.

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Those are the ones I was referring to!

They replaced an Infernal Combustion Engined pump in the early 70s. That engine was identical with the engine in the old 3-in-1 walers.
 
Gas turbines have very little torque thats why they run at 50-60,000 rpm and are geared down, turbines like to run at a constant rpm and aren't suited to a vehicle which requires the use of a gearbox with different ratios. Also the problem is how to transmit the power to a gearbox via a clutch or torque converter to move off from stationary when its idle speed up around 15-20,000rpm.
Volvo Flygtmotor dabbled with them in the 80's for vehicle applications but nothing has been heard of them since.
The other problem is that turbines are governed by 'start cycles' between overhaul, so you don't stop and start them frequently like a conventional engine. And if they experience a 'hot start' as did our firms Eurocopter when the turbine temp exceeds a set limit then the engine has to be inspected, which in ours cost around £70,000 to be rebuilt.
 
Back in the sixties I had a brief involvement with Rover Gas Turbines and once went for a ride as passenger in one of their development cars round the Solihull test track. The engine IIRC was rated at 150 hp and consisted of a gas generator unit and a completely separate power turbine coupled to all 4 wheels. there is no need for a conventional multi-ratio gearbox, I can't remember what arrangement there was for reverse. The moving off technique was to hold the brakes, rev the gas-generator to about 50,000 rpm and release the brakes. The effect was akin to being shot from a catapult, most of the circuit was just a blur! The problems were high fuel consumption, and massive discharge of hot gas. There were plans to develop heat exchangers to reduce these drawbacks. Soon afterwards, Rover abandoned this work and it moved to the east coast as a small separate company, mainly government funded I think, the interest being multi-fuel military engines. At the time I remember seeing in the workshops the Le Mans car and a lorry. There might even have been a plan for a turbine engined Rover 2000.
 
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