Yuan Class AIP & Kilo Submarine Thread

[AF-1]

Pakistan's technology/economy might grow faster than other countries in the region since partnership with China getting stronger, both at civilian and military field...
Also Pakistani ties with other big muslim nations can open doors for stronger Chinese presence and cooperation with those countries, win - win.

 

[Broccoli]

I wonder how much of the fabrication works would actually go to Pakistan or whether they're actually just assembling modules. I think it's more likely the latter considering Pakistan's technology/economy is still quite weak

Pakistan has build Agosta-class submarines in the past.

 

[antiterror13]

8 subs, 4 built in China and 4 in Pakistan.

8 Yuan class (export version) is quite a big number, especially for a country like Pakistan.

Hope other countries would order Yuan in the future, I am thinking of Indonesia, South Africa, Brazil, Argentina, Bangladesh and possibly Iran

 

[antiterror13]

Pakistan has build Agosta-class submarines in the past.

Agosta is small sub. Yuan is at least 2x bigger

 

[para80]

The size is not relevant in this regard and would only influence some basic infrastructure requirements, if that. But they are both very comparable efforts from the POV of expertise and require the same skill set. A more pertinent question would be whether Pakistan has retained the skills they applied to the Agosta-build. Any gap in construction creates such problems and the Agostas were bolted together nearly 20 years ago. Personally I wouldnt be surprised if the localised effort requires very substantial Chinese assistance.

 

[antiterror13]

The size is not relevant in this regard and would only influence some basic infrastructure requirements, if that. But they are both very comparable efforts from the POV of expertise and require the same skill set. A more pertinent question would be whether Pakistan has retained the skills they applied to the Agosta-build. Any gap in construction creates such problems and the Agostas were bolted together nearly 20 years ago. Personally I wouldnt be surprised if the localised effort requires very substantial Chinese assistance.

Size does matter for Sub construction. But I agree that it will be a lot of assistance from the close friend China

Also for China interest that Pakistan have a strong navy and sub force

 

[LCR34]

Sutton did a brief on PLAN Submarines.

 

[AndrewS]

The most powerful sterling engine is being developed and it will even get more powerful in the future.
The article hints that it can be used in sodium cooled fast reactor submarine.

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This is interesting.

I've been thinking over the design choices made by the Chinese Navy and the Japanese Navy.

The Japanese Navy was previously building Soryu submarines with 4 Stirling engines @75KWe plus diesel engines
But they switched entirely to lithium-ion batteries plus 2 1450KW diesels.
If the submarine's battery capacity is 230,000 KWh, then it would take 79hours to fully charge up the batteries with the onboard diesels whilst snorkeling.

---

And from what I can see, the 75KWe Stirling engines have the following performance figures:

Operating Depth <200metres
Oxygen (980g/KWh) + Diesel (260g/KWh). That works out as 0.8KWh/tonne of fuel.

If Lithium-ion batteries are currently at 300Wh/kg (0.3KWh/tonne), then the energy density of the batteries is still significantly less than burning a [Diesel + Liquid Oxygen] combination and turning that into electricity. However, you have to take into account other weight such as the engine used to burn the diesel and oxygen. And looking to the future, we may see lithium battery technology improve to 500Wh/kg in 10 years time, but that energy density will still be significantly lower than [Diesel + Liquid Oxygen]

---
The Yuan uses similar 75KW Stirling engines and has 4? of them.

But if 320KW Stirling engines become available that opens up some interesting possibilities. If you have 2 of these larger Stirling engines, that would be more than twice the underwater power available . I reckon sustained underwater speed could increase from 7 to 9 knots, which is significant. But more importantly, a submarine could run at run 3-5knots and still have 500KW left to charge up batteries underwater

From what I can see it takes about 6MW of power for a Soryu/Yuan to run at 20 knots for combat manoeuvres.
4 hours of combat manoeuvres would require 24MWh of batteries, and this could be fully recharged from empty whilst underwater in 48hours.

---
Alternatively, the Stirling heat engines could be used with a small reactor if development works out.

We saw a small 600KW VAU-6 reactor under development in a powerpoint from a few years ago

 

[gelgoog]

I do not see what would be the advantage of using a Stirling engine instead of a regular steam turbine in a nuclear reactor design.

In general steam turbines are smaller for the same power output and a Stirling engine won't be more energy efficient either.
Steam turbines are also way simpler to build and cheaper.

Sure, you wouldn't have water in the engine, and that might make a difference in a sodium reactor. But I think using sodium reactors in a nuclear submarine is a stupid idea in the first place. Hot sodium ignites in contact with water and even if you don't have that in the loop, it is a submarine, you are surrounded by water. The sodium would also solidify if the reactor core temperature goes down. In other words it has all the same issues the Soviet lead-bismuth reactors in the Alfas had, plus the sodium can ignite and explode unlike lead-bismuth.

If you want to use a fast reactor type why not use lead-bismuth instead of sodium? Sure, China has more experience with sodium fast reactor technology. But it is not like they don't have experience with lead-bismuth either.

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Plus it is not like their relations with Russia are that bad they couldn't get technology that way either. They are already getting Russian help with the CFR-600. They could just license the BREST-300 design and get the technology that way.

I think like you said this makes the most sense as a replacement for the existing Stirling engines on conventional submarines.

 

[BoraTas]

This is interesting.

I've been thinking over the design choices made by the Chinese Navy and the Japanese Navy.

The Japanese Navy was previously building Soryu submarines with 4 Stirling engines @75KWe plus diesel engines
But they switched entirely to lithium-ion batteries plus 2 1450KW diesels.
If the submarine's battery capacity is 230,000 KWh, then it would take 79hours to fully charge up the batteries with the onboard diesels whilst snorkeling.

---

And from what I can see, the 75KWe Stirling engines have the following performance figures:

Operating Depth <200metres
Oxygen (980g/KWh) + Diesel (260g/KWh). That works out as 0.8KWh/tonne of fuel.

If Lithium-ion batteries are currently at 300Wh/kg (0.3KWh/tonne), then the energy density of the batteries is still significantly less than burning a [Diesel + Liquid Oxygen] combination and turning that into electricity. However, you have to take into account other weight such as the engine used to burn the diesel and oxygen. And looking to the future, we may see lithium battery technology improve to 500Wh/kg in 10 years time, but that energy density will still be significantly lower than [Diesel + Liquid Oxygen]

---
The Yuan uses similar 75KW Stirling engines and has 4? of them.

But if 320KW Stirling engines become available that opens up some interesting possibilities. If you have 2 of these larger Stirling engines, that would be more than twice the underwater power available . I reckon sustained underwater speed could increase from 7 to 9 knots, which is significant. But more importantly, a submarine could run at run 3-5knots and still have 500KW left to charge up batteries underwater

From what I can see it takes about 6MW of power for a Soryu/Yuan to run at 20 knots for combat manoeuvres.
4 hours of combat manoeuvres would require 24MWh of batteries, and this could be fully recharged from empty whilst underwater in 48hours.

---
Alternatively, the Stirling heat engines could be used with a small reactor if development works out.

We saw a small 600KW VAU-6 reactor under development in a powerpoint from a few years ago

Just asking why do you think Soryu has 230 MWh of battery power? I think it is impossible. Even if its batteries have half the energy density of an EV battery and weigh 500 tons, the Soryu's total battery storage would be around 50 MWh. More realistically it should be around 30 MWh. As for why they ditched the AIP is they want Taigei to operate in open-ocean. Low-speed endurance AIP provides is of less use in that environment and AIP provides 0 extra high-speed endurance because of its low power. They ditched it for more lithium-ion batteries for higher high-speed underwater endurance and more diesel fuel for extra range.