Originally Posted by
esa-aardvark
So Tourist, what is the benefit of gas turbines which appear
not to work reliably (*6) ?
Ah, you were serious.
Ok,
1. They are very reliable. The gas turbine is not the problem on the T45. I will stick my neck out and say that gas turbine engines are more reliable than piston engines as a general rule. If you tried to get the similar performance from a diesel engine that you get from a gas turbine, the diesel will have more failures. Look at aero engines. Astonishingly reliable.
2. The diesel engine in that freighter took a very long time to get that freighter up to the 25kt speed you quote. Warships have a requirement to be very much quicker both in top speed and in acceleration and deceleration. The power to weight and size ratio of a gas turbine is vastly superior along with much faster response times.
3. Due to the way drag works in displacement vessels, very simplistically without going into Froude numbers etc it is easier to get a long ship to a high speed than a short ship. A diesel engine that could get a relatively short warship to 30+ kts would take up most of the ship.
https://en.wikipedia.org/wiki/Hull_speed
Incidentally, that freighter may have once done 25Kts in a trial, but what speed did it actually bimble around at? I'm guessing no faster than 18kts, probably around 15kts?
That is the speed range most ships traverse the world at, and that is the speed diesels excel at.
4. You mention maintenance. Gas turbine units can be swapped out through specifically designed routes in the ship. The Spares are carried on RFAs. Good luck with that on a freighters vast Diesel engine.
Plus you need more than 1 engine for redundancy etc.
Ask yourself why warship designers all over the world are not using diesel engines.
Is it because they are all idiots, or is it perhaps slightly less simplistic than you imagine?
Note that steam powered warships were just as quick (many slightly quicker) and nearly everybody (super carriers and big subs aside, they stuck with steam!) moved from steam to gas turbine once they became available.