The navy uses gas turbines in its Arleigh Burke class destroyers. I was just wondering what type of fuel they burn.
I believe that the ships use the same JP-5 as aircraft. Here’s a 1992 reportjustifying the switch from the previous fuel.
And the cruisers use the same General Electric LM2500 turbine engines that the destroyers do. Four of them.
They usually burn NATO F-76 aka Naval Distillate though can burn JP-5 (NATO F-44). It’s been proposed over the years to make JP-5 the ‘universal fuel at sea’ but it’s not the case. Those two fuels specs aren’t greatly different though, and specification changes since that paper have made them more similar. But still in general JP-5 is a tighter specification and fuels meeting F-76 easier to source worldwide. Sometimes ‘JP-5’ burned in ship’s engines is fuel which has fallen out of spec as JP-5 to use in a/c (possible contamination with other fuel, old, etc).
The big difference in ships’ oil fuel is between distillates like F-76 and JP-5 on one hand and heavy fuel on the other. Before and early in the gas turbine era steam warships burned a form of heavy fuel, Navy Special Fuel Oil in the USN. When gas turbine warships became predominant navies (not only USN or NATO) generally standardized on distillate in all ships, since the ‘aeroderivative’ gas turbines in warships can’t burn heavy fuel. Merchant diesel ships mainly burn heavy fuel, and some naval ship diesels could, but are also standardized on distillate, along with the few remaining steam powered naval vessels.
What happened to the triple expansion steam engines?
With apologies to the OP, I have a quick thread hijack.
Does the US Navy have any nuclear powered surface vessels that are not aircraft carriers?
They had cruisers which were, but all have been decommissioned AFAIK.
The Russians have the Kirov class, which has both a nuclear plant and an oil fired engine, simultaneously. For some strange and unknowable reason.
From Wikipedia - Nuclear submarine - Wikipedia
“All naval nuclear reactors currently in use are operated with diesel generators as a backup power system. These engines are able to provide emergency electrical power for reactor decay heat removal, as well as enough electric power to supply an emergency propulsion mechanism.”
Based on personal conventional power plant experience, the backup power generation would also make Startup easier. Without backup power, it will be cumbersome to start the nuclear system and it will take a long time.
No, Kirov class does not have a backup Diesel engine like submarines do.
It’s oil fired turbine is a part of the primary propulsion system. As it is working during normal operations.
I am offering an educated guess based on my experience with power generation.
For nuclear submarines, the engine is small (maybe in 10s of MW). Diesel engines can fit in this power range - they get complicated for large power sizes. So smaller nuclear powered ships or submarines will have Diesel engines as backup.
I am guessing the “Kirov Class” needs in the 100s of MWs. In this range Diesel Engines are not cost effective. You can put a gas turbine but it is expensive and has fuel restrictions. It’s just easier to put an oil fired boiler and use the steam from the boiler to supplement or replace the steam from the nuclear reactor as needed.
But once you have a oil fired boiler, it’s not a good idea to turn it off / on - because boilers don’t like Thermal upsets and they need a long time to startup / shutdown. So the Oil fired Boiler will produce about 100% of the power when needed and continue to produce about 30% power at a minimum because that’s the minimum turndown of a well designed boiler.
Are you sure it is a Oil fired turbine ? The LM2500 (aeroderivative) does not accept heavy oil firing. You will need a frame class turbine for that but those are bulky, heavy and difficult to operate.
I am guessing it is an oil fired boiler which makes steam which in turn runs steam turbines (probably the same steam turbine as run by the nuclear reactor).
(Not sure if this was in jest)
Warships haven’t used triple expansion steam engines for a very long time. By WWII it was quite common to have a 600PSi or 1200PSI plant driving a set of steam turbines–a conical high pressure turbine connected to a bowtie-shaped low pressure turbine via a crossover pipe.
Such configurations are still in place in the engine rooms of our nuclear powered vessels–the source of the steam is a steam generator vs. a traditional boiler, but the rest of the steam plant is pretty much the same.
Everyone else uses gas turbine engines. I was a machinist’s mate in the nuclear navy, so I have no knowledge of gas turbines, but I strongly suspect they are far simpler to operate.
A steam plant has thousands of valves and lots of complex procedures for bringing all of the various components on line (odd stuff that ordinary folks have never heard of such as “main condenser air ejectors” and “deaerating feed tank”).
Those are there because air (oxygen specifically ) is very corrosive at higher temp/ pressure common with steam systems. Those are common parts for any high pressure steam system.
The DFT is there for that reason, but the air ejectors not so.
They are there because air builds up over time in the main condenser, displacing the steam vapor that should be condensing. The main condenser operates at a vaccuum, produced by the effect of condensing steam to water. Air doesn’t condense, so all it does is reduce the vaccuum and reduce the efficiency of the steam plant, hence the need for air ejectors—small Venturi-style jet pumps driven by steam.
The last triple expansion ships were the Liberties build in WWII.
Black Coffee, navy style
There were also a lot triple expansion engine powered warships built in WWII. The Flower/Castle class corvettes and most River/Loch/Bay class frigates in the RN, US Tacoma class frigates, the standard German large minesweepers of WWII had a hybrid system of recip engines exhausting to a turbine, etc.
There were some triple expansion merchant ships built as late as the 1950’s. But I can’t think of any triple expansion warships built after WWII, not counting ships of the wartime classes which happened to be completed just after the war, or completely non-combat types owned by navies, perhaps. It’s more merchant ships if you relax it to reciprocating steam engines, including Unaflow and compound engines in paddle wheelers, etc.
I have read two explanations of the Kirov plant; originally it was thought (in NATO) to be nuclear cruise with boilers for superheated steam (PWRs produce saturated steam), but now it is thought to be a backup to the nuclear reactor. Or maybe both.
USS Long Beach and USS Enterprise, which used similar reactor plants (2 for the LB, 8 for the Big E), had 1000KW diesels. More than one. AIW prototype had a large Fairbamks-Morse opposed cylinder engine, and I am reasonably sure both ships used a similar model.
USN submarines are supposed to be able to start the reactor with just the battery, but I would not have wanted to do that.
(OP is answered, so continuing with the hijack).
Which happen to be derivatives of the GE CF6 airplane gas turbine, which powers a lot of big airliners and military aircraft such as the C-5 Galaxy and Air Force One(the two planes that have that job anyway).
And triple-expansion steam went out with the USS Texas… BB-35, not CGN-39 or SSN-775.