Plan Type 095/096 Nuclear Submarine Thread

Hendrik_2000

Brigadier
I think one 20MW class generator is enough. As I mentioned in post #29, for comparison Virginia class is around the same displacement of 093 and probably 095, it has 30MW shaft power. 40MW would make a sub of that dimension even faster but also noisier. 30MW is good enough. 20MW class is in reality more than that. If my guess in post #29 is close to reality, it is 27MW flat shaft power with max power being 29MW in a dash. That is exactly where Virginia is, and very likely where PLAN wants to be.

Another thing is the room/footprint. 2 means double the weight and footprint, something the sub can not afford.
I am not so sure about that most nuclear power plant run between 50MW to 100 MW Don't forget this is a big boat 7000 ton almost one and half of Type 54 ships. That is why they need compact genset to save on space and this is the first time too since previous boat propeller are connected directly to ST via gear reducer. Nuclear sub require high reliability which almost impossible with single turbine. Single point failure. You can calculate that
http://www.world-nuclear.org/information-library/non-power-nuclear-applications/transport/nuclear-powered-ships.aspx

India launched its first nuclear submarine in 2009, the 6000 dwt Arihant SSBN, with a single 85 MW PWR fuelled by HEU (critical in August 2013) driving a 70 MW steam turbine. It is reported to have cost US$ 2.9 billion and was to be commissioned in 2016. The second and slightly larger Arihant-class SSBN, the INS Aridaman is being built at the Ship Building Centre in Visakhapatnam, and was due to be launched in 2018 and commissioned by 2022. It will have a more powerful reactor. Another three Arihant-class vessels launched by 2023 and then six SSBN twice the size of Arihant-class and six nuclear SSNs are planned, the latter being approved by the government in February 2015. The SSNs will be a similar size to Arihant-class SSBN and powered by a new reactor being developed by BARC. India is also leasing an almost-new 7900 dwt (12,770 tonne submerged) Russian Akula-II class nuclear attack submarine for ten years from 2010, at a cost of US$ 650 million: the INS Chakra, formerly Nerpa. It has a single 190 MWt VM-5/OK-659B (or OK-650B) PWR driving a 32 MW steam turbine and two 2 MWe turbogenerators.

Sturgeon class has 2 steam turbine connected to single propeller
Model of USS Sturgeon (SSN-637)
http://americanhistory.si.edu/subs/const/anatomy/attacks/index.html

Nuclear-powered Fast Attack Submarine Sturgeon was the first of a 37-boat class commissioned from March 1967 to August 1975. She was 292 feet (89 m) long and displaced 4,762 tons submerged. Her crew numbered 107. Power came from a single S5W (Submarine, Model 5, Westinghouse) pressurized-water nuclear reactor driving two steam turbines connected to a single propeller shaft. Sturgeon could make better than 20 knots (37 km/hr) on the surface, over 25 knots (46 km/hr) submerged (the exact figure remains classified).
 
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taxiya

Major
Registered Member
I am not so sure about that most nuclear power plant run between 50MW to 100 MW Don't forget this is a big boat 7000 ton almost one and half of Type 54 ships. That is why they need compact genset to save on space and this is the first time too since previous boat propeller are connected directly to ST via gear reducer. Nuclear sub require high reliability which almost impossible with single turbine. Single point failure. You can calculate that
http://www.world-nuclear.org/information-library/non-power-nuclear-applications/transport/nuclear-powered-ships.aspx

India launched its first nuclear submarine in 2009, the 6000 dwt Arihant SSBN, with a single 85 MW PWR fuelled by HEU (critical in August 2013) driving a 70 MW steam turbine. It is reported to have cost US$ 2.9 billion and was to be commissioned in 2016. The second and slightly larger Arihant-class SSBN, the INS Aridaman is being built at the Ship Building Centre in Visakhapatnam, and was due to be launched in 2018 and commissioned by 2022. It will have a more powerful reactor. Another three Arihant-class vessels launched by 2023 and then six SSBN twice the size of Arihant-class and six nuclear SSNs are planned, the latter being approved by the government in February 2015. The SSNs will be a similar size to Arihant-class SSBN and powered by a new reactor being developed by BARC. India is also leasing an almost-new 7900 dwt (12,770 tonne submerged) Russian Akula-II class nuclear attack submarine for ten years from 2010, at a cost of US$ 650 million: the INS Chakra, formerly Nerpa. It has a single 190 MWt VM-5/OK-659B (or OK-650B) PWR driving a 32 MW steam turbine and two 2 MWe turbogenerators.

Sturgeon class has 2 steam turbine connected to single propeller
Model of USS Sturgeon (SSN-637)
http://americanhistory.si.edu/subs/const/anatomy/attacks/index.html

Nuclear-powered Fast Attack Submarine Sturgeon was the first of a 37-boat class commissioned from March 1967 to August 1975. She was 292 feet (89 m) long and displaced 4,762 tons submerged. Her crew numbered 107. Power came from a single S5W (Submarine, Model 5, Westinghouse) pressurized-water nuclear reactor driving two steam turbines connected to a single propeller shaft. Sturgeon could make better than 20 knots (37 km/hr) on the surface, over 25 knots (46 km/hr) submerged (the exact figure remains classified).
I am not sure why you think 27MW (29MW max) is small. Are those big numbers thermal output of the reactor? The 27MW that I am talking about should not to be confused with the reactor's thermal power. One should multiply the figure like 27 by 20% (old) or 30% (new) to get shaft power which is the output of the turbine drive shaft, another 98% will give the electricity.

That is why there are many designations as MWt (thermal) and MWe (electricity) or SHP (shaft horsepower).

Your example of Nerpa is a good example, 190 MWt to 32MW (shaft) which is 16.8% (old), then COULD be translated to around 30MWe (depending on how good the Soviet was in electrical generators). Note, this 32 MW shaft is to drive this huge (13 000t) sub to max. 35 knots, while Virginia and 095 are much smaller (7000 to 8000t) and neither USN nor PLAN is obsessed to speed. So as I said, max 30MWe is what PLAN want.
 

Hendrik_2000

Brigadier
Commercial power plant efficiency is around 30% or lower But nuclear power plant for submarine are special breed to save on space they have to generate High BTU steam to give a smaller turbine so efficienty should be higher than cpommercial plant
I don't know where you get that 16% from The figure 32MW for Nerpa or Chakra could be for single turbine
If you calculate 190MWt X 0.33 X0.98=60 MWe/2=30MWe
Because Arihant which is 6000 Ton need 70 MW turbine

Nuclear
http://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/

The efficiency of nuclear plants is little different. On the steam turbine side they use the Rankine thermodynamic cycle with steam temperatures at saturated conditions. This gives a lower thermal cycle efficiency than the high temperature coal fired power plants. Thermal cycle efficiencies are in the range of 38 %. Since the energy release rate in nuclear fission is extremely high, the energy transferred to steam is a very small percentage - only around 0.7 %. This makes the overall plant efficiency only around 0.27 %. But one does not consider the fuel efficiency in nuclear power plants; fuel avaliabity and radiation losses take center stage
 

taxiya

Major
Registered Member
Commercial power plant efficiency is around 35% or lower But nuclear power plant for submarine are special breed to save on space they have to generate High BTU steam to give a smaller turbine so efficienty should be higher than cpommercial plant
I don't know where you get that 16% from The figure 32MW for Nerpa or Chakra could be for single turbine
If you calculate 190MWt X 0.33 X0.98=60 MWe/2=30MWe
Because Arihant which is 6000 Ton need 70 MW turbine

Nuclear
http://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/

The efficiency of nuclear plants is little different. On the steam turbine side they use the Rankine thermodynamic cycle with steam temperatures at saturated conditions. This gives a lower thermal cycle efficiency than the high temperature coal fired power plants. Thermal cycle efficiencies are in the range of 38 %. Since the energy release rate in nuclear fission is extremely high, the energy transferred to steam is a very small percentage - only around 0.7 %. This makes the overall plant efficiency only around 0.27 %. But one does not consider the fuel efficiency in nuclear power plants; fuel avaliabity and radiation losses take center stage
Because you said
the INS Chakra, formerly Nerpa. It has a single 190 MWt VM-5/OK-659B (or OK-650B) PWR driving a 32 MW steam turbine
190 MWt to 32MW (shaft) which is 16.8%
 

taxiya

Major
Registered Member
Does not make sense because typical nucler power plant efficiency is 30% 32 Mwt is single turbine they need 2
Commercial power plant efficiency is around 30% or lower But nuclear power plant for submarine are special breed to save on space they have to generate High BTU steam to give a smaller turbine so efficienty should be higher than cpommercial plant
I think it is a mistake to assume everything military to be one grade higher than civilian. The technology is the same and developed by the same people. The difference is military will use highly enriched fuel to be compact in size and last longer without refueling than the civilian counterpart.

The efficiency (the 20 or 30%) of converting heat energy/power to mechanical energy/power relies on the steam turbine and the loop of transferring steam, NOT related to the capacity of the reactor to generate heat.

Besides, the American S8G reactor has something around 20%, not much better than what the Russian did 16.8%. I found something here http://www.alternatewars.com/BBOW/Nuclear/US_Naval_Reactors.htm and I quote
S8G
Power: 220 MWth or 60,000 SHP
Reactor Compartment Dimensions: 42 feet in diameter, 55 feet long; 2,750 tons Uses: SSBN 726 Ohio Class (1 reactor) Notes: Natural-circulation/Forced Circulation reactor. At low power levels, coolant is allowed to circulate via heat differential. At higher power levels, pumps kick in.
220 MWt to 60,000 SHP (44.7MW shaft), that is 20%
 

Hendrik_2000

Brigadier
I think it is a mistake to assume everything military to be one grade higher than civilian. The technology is the same and developed by the same people. The difference is military will use highly enriched fuel to be compact in size and last longer without refueling than the civilian counterpart.

The efficiency (the 20 or 30%) of converting heat energy/power to mechanical energy/power relies on the steam turbine and the loop of transferring steam, NOT related to the capacity of the reactor to generate heat.

Besides, the American S8G reactor has something around 20%, not much better than what the Russian did 16.8%. I found something here http://www.alternatewars.com/BBOW/Nuclear/US_Naval_Reactors.htm and I quote

220 MWt to 60,000 SHP (44.7MW shaft), that is 20%
No the mechanical cycle is actually higher 36% but you have to combine it with the heat efficiency of nuclear to generate steam as the article that I quoted clearly said. So the overall efficiency is 27 to 30% in commercial nuclear power plant.
The thermal efficiency of a conventional nuclear power station is around 33%. Therefore, to generate 1,000 MW of electrical power (MWe) in a nuclear plant it is needed around 3,000 MW of thermal power from the fission reaction.
efficiency in electricity generation - Eurelectric
www.eurelectric.org/Download/Download.aspx?DocumentID=13549

Actually 1 SHP=0.7457 KiloWatt so it should be 21% and definitely better than 16%
It could be that nuclear submarine overall efficiency is lower than commercial nuclear due to the specific requirement of nuclear submarine like this

Current U.S. naval reactors are all pressurized water reactors, which are identical to PWR commercial reactors producing electricity, except that:
  • they have a high power density in a small volume and run either on low-enriched uranium (as do some French and Chinese submarines) or on highly enriched uranium (>20% U-235, current U.S. submarines use fuel enriched to at least 93%,[3] compared to between 21–45% in current Russian models, although Russian nuclear-powered icebreaker reactors are enriched up to 90%),[citation needed]
  • they have long core lives, so that refueling is needed only after 10 or more years, and new cores are designed to last 25 years in carriers and 10–33 years in submarines,
  • the design enables a compact pressure vessel while maintaining safety.
  • Submarine lower efficiency.JPG
 
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taxiya

Major
Registered Member
No the mechanical cycle is actually higher 36% but you have to combine it with the heat efficiency of nuclear to generate steam as the article that I quoted clearly said. So the overall efficiency is 27 to 30% in commercial nuclear power plant.
The thermal efficiency of a conventional nuclear power station is around 33%. Therefore, to generate 1,000 MW of electrical power (MWe) in a nuclear plant it is needed around 3,000 MW of thermal power from the fission reaction.
efficiency in electricity generation - Eurelectric
www.eurelectric.org/Download/Download.aspx?DocumentID=13549

Actually 1 SHP=0.7457 KiloWatt so it should be 21% and definitely better than 16%
It could be that nuclear submarine overall efficiency is lower than commercial nuclear due to the specific requirement of nuclear submarine like this

Current U.S. naval reactors are all pressurized water reactors, which are identical to PWR commercial reactors producing electricity, except that:
  • they have a high power density in a small volume and run either on low-enriched uranium (as do some French and Chinese submarines) or on highly enriched uranium (>20% U-235, current U.S. submarines use fuel enriched to at least 93%,[3] compared to between 21–45% in current Russian models, although Russian nuclear-powered icebreaker reactors are enriched up to 90%),[citation needed]
  • they have long core lives, so that refueling is needed only after 10 or more years, and new cores are designed to last 25 years in carriers and 10–33 years in submarines,
  • the design enables a compact pressure vessel while maintaining safety.
  • View attachment 45140
You just answered the question
Actually 1 SHP=0.7457 KiloWatt so it should be 21% and definitely better than 16%
It could be that nuclear submarine overall efficiency is lower than commercial nuclear due to the specific requirement of nuclear submarine like this
I suspect that the seemingly lower Soviet figure of 16% than the American 21% was MAYBE to prolong the burn time of the fuel to avoid cutting open the sub for refuel considering the lower enrichment of Soviet subs. That means the Soviet reactors were running at a lower capacity than their designed full capacity 190MW. So their steam turbine is as efficient as the Americans. In other words, Soviet put a "more than enough" reactor in the sub to mitigate the less enriched fuel.
 

Hendrik_2000

Brigadier
BTW I found the formula to calculate the power requirement of bluff body with 10m Dia or Beam moving thru saltwater with speed of 28.5 mile/hr or 17 knot . Assuming no friction. Of course this is not right but just to get the idea of power requirement Type 93 or 95 supposed to have 11 m beam. It is definitely larger than 30 MW if you add the friction, 30 knot speed, power for utility, desalination,HVAC etc
So going back to original argument those genset are about the right size for nuclear submarine QED
Type: nuclear-powered attack submarine
Displacement: 7,000 tonnes (submerged)[1]
Length: 110 m[1]
Beam: 11 m[1]
Draft: 7.5 m[1]
Propulsion: Pressurized water nuclear reactor
Speed: 30 kn[1]
Submarine calc.JPG
 
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