CV-18 Fujian/003 CATOBAR carrier thread

[Max Demian]

There wasn't generator connected to the steam turbine, means they had to install auxiliary generators at the upper levels, and that moved up the centre of gravity, eroding the safety margins of the ship. (source: wiki)

Means the installation of the genset to the island is more of a cost cutting / desperate move than an example of a good design.

Can you link the source? Nimitz class has 8x8MW steam turbine generators. What you are describing sound like backup generators?

The Brits saved about 3000 cubic meters of volume by installing the turbine generators into the islands, instead into the hull. The Queen Mary 2 ocean-liner also has its gas turbines installed above deck, for similar reasons. The real downside is increased vulnerability, as there is less protection around the engines in the island than there is deep in the hull.

 

[Tam]

I have yet see accident in steam power plant !There are literally thousand upon thousand of steam power plant all over the world. In fact China built 5000MW every months before the financial crisis. What accident are you talking about NONE! You are thinking of an old boiler pre WW II A frame Modern ship boiler is compact o frame Can be removed. UNlike destroyer or Frigate you don't need to ramp up power plant in carrier !

There is no problem with piping if you designed it properly by using piping stress analysis code.You can simulate shock,vibration, thermal cycle etc. NO leak either since most of the piping are of welded construction only flanged at terminal point even then you can calculate and predict when it will leak of course you have to tighten up periodically. You must be thinking of old plant! I design power plant conventional or combined cycle I know what I am talking about
This is the picture of actual Liaoning boiler on the right!. there are 8 of them. Since they are way below of course removal is difficult
View attachment 63154View attachment 63155

Maybe for China yes, no accident. India is another story.

 

[Anlsvrthng]

Can you link the source? Nimitz class has 8x8MW steam turbine generators. What you are describing sound like backup generators?

The Brits saved about 3000 cubic meters of volume by installing the turbine generators into the islands, instead into the hull. The Queen Mary 2 ocean-liner also has its gas turbines installed above deck, for similar reasons. The real downside is increased vulnerability, as there is less protection around the engines in the island than there is deep in the hull.

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The Nimitz design has accommodated many new technologies over the decades, but it has limited ability to support the most recent technical advances. As a 2005 Rand report said, "The biggest problems facing the Nimitz class are the limited electrical power generation capability and the upgrade-driven increase in ship weight and erosion of the

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margin needed to maintain ship stability.

I think the occupied volume is less concern on the ship, the simpler/ cheaper design and manufacturing is more.

Any complex machine deep in the hull means more risk of delays and cost overruns.

 

[FireyCross]

I have yet see accident in steam power plant !There are literally thousand upon thousand of steam power plant all over the world. In fact China built 5000MW every months before the financial crisis. What accident are you talking about NONE! You are thinking of an old boiler pre WW II A frame Modern ship boiler is compact o frame Can be removed. UNlike destroyer or Frigate you don't need to ramp up power plant in carrier !

There is no problem with piping if you designed it properly by using piping stress analysis code.You can simulate shock,vibration, thermal cycle etc. NO leak either since most of the piping are of welded construction only flanged at terminal point even then you can calculate and predict when it will leak of course you have to tighten up periodically. You must be thinking of old plant! I design power plant conventional or combined cycle I know what I am talking about
This is the picture of actual Liaoning boiler on the right!. there are 8 of them. Since they are way below of course removal is difficult
View attachment 63154View attachment 63155

Indeed, it can be made reliable, but I think the point was that in the event of battle damage, the risk is higher due to the large amount of high pressure steam plumbing that would lead to greater risk to the crew and also the other systems on board. Carriers are in situation where the enemy is deliberately trying to hurt them, and having an extensive duct system of high pressure, high temperature steam is an inherent weak spot. With steam catapults this was an unavoidable risk, but thanks to EMALS, gas turbines can avoid this vulnerability, at the cost, as you say, of making re-use of the design for a nuclear version more difficult.

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I think the occupied volume is less concern on the ship, the simpler/ cheaper design and manufacturing is more.

Any complex machine deep in the hull means more risk of delays and cost overruns.

Shorter maintenance times (due to a simpler and more compact unit with fewer parts) could also be a non-trivial advantage, especially given that the Chinese carrier fleet is unlikely to match the Americans in numbers. Achieving a higher availability rate and faster turnaround rate can compensate for that.

 

[Anlsvrthng]

Shorter maintenance times (due to a simpler and more compact unit with fewer parts) could also be a non-trivial advantage, especially given that the Chinese carrier fleet is unlikely to match the Americans in numbers. Achieving a higher availability rate and faster turnaround rate can compensate for that.

True.

This pdf showing the biggest issue with the electric propulsion :

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The gas turbine is 7.5 tons, but the whole 53 MW unit is 137 tons, due to the generator weight.

On the opposite side the weight of the propulsion motor is at lest magnitude higher .


So, gas turbine-transmission-propeller combo has a magnitude smaller combined weight.

 

[Hendrik_2000]

Indeed, it can be made reliable, but I think the point was that in the event of battle damage, the risk is higher due to the large amount of high pressure steam plumbing that would lead to greater risk to the crew and also the other systems on board. Carriers are in situation where the enemy is deliberately trying to hurt them, and having an extensive duct system of high pressure, high temperature steam is an inherent weak spot. With steam catapults this was an unavoidable risk, but thanks to EMALS, gas turbines can avoid this vulnerability, at the cost, as you say, of making re-use of the design for a nuclear version more difficult.



Shorter maintenance times (due to a simpler and more compact unit with fewer parts) could also be a non-trivial advantage, especially given that the Chinese carrier fleet is unlikely to match the Americans in numbers. Achieving a higher availability rate and faster turnaround rate can compensate for that.

You are talking 2 different thing here Catapult and power plant . I don't argue about Emal since it has advantages like variable load and less jerking,less maintenance .But the steam power plant is deep in the bowel of the ships And carrier has what 7 stories ? If bomb reached the bottom of the ship then nothing can help the ship It is done kaput

 

[taxiya]

True.

This pdf showing the biggest issue with the electric propulsion :

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The gas turbine is 7.5 tons, but the whole 53 MW unit is 137 tons, due to the generator weight.

On the opposite side the weight of the propulsion motor is at lest magnitude higher .


So, gas turbine-transmission-propeller combo has a magnitude smaller combined weight.

Are you sure that the transmission (MRG and clutches etc.) system here is any lighter than combination of generator and motor in the same power range? I don't think so.

Do you have data of gearbox for similarly powered GT? Here is what I find of DDG-51. And it is only just one gearbox. It looks like this


And here LM-2500 offered to KDDX, the big box on the right side. There are going to be four of them. This does not count the clutches and gears combining two of them to drive one shaft.

 

[Anlsvrthng]

Are you sure that the transmission (MRG and clutches etc.) system here is any lighter than combination of generator and motor in the same power range? I don't think so.

Do you have data of gearbox for similarly powered GT? Here is what I find of DDG-51. And it is only just one gearbox. It looks like this
View attachment 63160

And here LM-2500 offered to KDDX, the big box on the right side. There are going to be four of them. This does not count the clutches and gears combining two of them to drive one shaft.

That is a marine diesel engine.

The generators are tricky, they looks small, even smaller than a gas turbine ,diesel generator or transmission, but actually all of the previous machine volume mainly air, and the generators / motors 90% steel and copper .

option with electrical motors :
1. Direct drive, in that case a 300 rpm motor will be 500 tons on 44 MW
2. With transmission on 3600 rpm, in that case the motor will be only 50 tons

But in the second case you can use simply the turbine-transmission-propeller chain, instead of the turbine-generator-motor-transmission - propeller.

The basic issue is the power of electrical motor / generator proportional to its rpm, so slow rotating motor is weak or extremely heavy.

 

[Anlsvrthng]

Combined electric / gas turbine propulsion . 2*4.5 MW electric motor , direct drive + 20 MW gas turbine, check the size difference.

German Navy F 125

Each motor is 40-80 tons .

 

[Deino]

Can we please come back to the carrier itself!?

https://twitter.com/i/web/status/1302520238089465857