Ideal PLAN submarine

You have an excellent point about the ratio of increased engine power, fuel storage, with larger sizes vs. drag. But of course, you do know that some of the largest aircraft are not that exactly fast.

Yes, weight only affects acceleration but to "dash" is actually one of the most important survival factors for a ship, and for a sub. One of the reasons why warships use gas turbines is because they can "dash" faster.

AIP research has concentrated on small subs for some reason, rather than start with something bigger, and only lately we have begun to push the boundaries of size upward. For that matter, we also don't see extremely large diesel subs going around.

And Planeman, what are you trying to do? Send the sub into space?

Studying Ami's point, it is very true that the requirements for power density is higher on smaller platforms. It is true for ships, true for aircraft and especially true even for automobiles (hence why countries that develop smaller cars also develop engine technologies to get a higher HP per weight ratios.) Of all the ship propulsion systems available today, remarkably enough, it is the diesel engine that offers the highest power density, short of using a gasoline engine.

Of course the converse to this issue is that weight has a tendency to cascade. Which means once a component in the system have increased weight, all that other things that are needed to support that component have to be strengthened which also causes an increase in weight. And these things cause other things to increase their weight and so on. Thus it becomes easy to end up with something heavier than you planned for.

If your technology is slightly behind the curve, a bigger submarine would provide less demands in power density for power plants, and the size itself provides better margins that could absorb errors in design and manufacture.

Of course, this leads us to another issue, which is cost. Bigger is more expensive for a sub---the hull is the most expensive part of it, with all the highest grade of steel and the precise, careful welding that goes into it. The bigger the hull, the more work that has to go into it. Large double hulls can be prohibitively expensive---Soviet adoption of these designs have nothing to do with classic Soviet philosophies of simplicity and ease of mass production. But rather, exploiting one advantage they have---cheap labor. China currently has the advantage of cheap labor, but you still need high skills to go with it, which means you will still end up paying a premium. Even now in China, salaries are going up in the most developed areas with the highest skillsets.

xiansu said:

I wonder if a conventional submarine could use a small gas turbine in a turbine-electric drive setup. The thermal efficiency rating of a small gas turbine with heat recovery system could be higher than 40%, probably approach 50%. This should be very close to what a diesel engine can achieve. The operational advantage of a much quieter gas turbine should outweigh the small penalty in maximum range, especially if the sub was designed for a more defensive role in smaller waters.

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norfolk said:

It would certainly be wonderful if we could get an engine fit for an SSK with the performance of a gas-turbine, but we're going to have to wait a while for technology to progress a long way yet. But a gas turbine is certainly quieter than a diesel (which is why ASW escorts usually have them). The problem for a gas turbine is that it just sucks up too much fuel compared to a diesel when surfacing running - as you mentioned that there would be a range penalty - (not to mention that the subs IR signature would go off the scale). That said, maybe there's a way around some of these problems.

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That's exactly what we are looking at using HTGR systems. The reactor heats up gas which will in turn run a gas turbine.

The problem is that the gas may be irradiated as a result, and the gas would in turn irradiate the turbine.

The idea is not too dissimilar from using a BWR or Boiling Water Reactor, which had already gone into a number of power plant designs. Like HTGR, you have a direct coolant circuit between the reactor and the turbine. So far we have not seen radioactive turbines as a result, so the potential danger of HTGR might be overblown.

If you are concerned about radioactivity on the turbine, the hot gas circuit can go into a heat exchanger to produce steam, so you have another stage. However, with two circuits, you lose the advantage of efficiency and simplicity, and this removes the advantage over traditional PWR setups.

The problem of using Helium gas, is that gas, being much less dense, has a much lower molecular crossection to capture heat before the heat is radiated away. Water captures heat much better. Liquid metal does it even more better, which is why at some time ago, there was experimentation to use liquid Lead, as in the Soviet Alfa class submarines, and to use liquid Sodium like in the USS Seawolf. But these metals are highly toxic, and you get a problem when the reactor shuts down (the coolant solidifies). So obviously you can't use liquid metal.

The thing about gas though, once its heated up, it retains the thermal energy better than steam, and that's where the efficiency of a gas turbine comes from.

The final option is something called Magnetohydrodynamic drive. I'm not sure if the spelling is right. The whole idea of MHD is to convert the energy directly from a reactor into electricity. No turbines, nothing. That would guarantee you the highest efficiency ever.

In an MHD, the reactor heats up some metal into liquid, and in the process, excites the electrons in that liquid metal creating a magnetic field. The liquid metal passes through what is basically a dynamo, and the magnetic field of the flowing liquid metal induces the electrons on the bundled wires to move---the same principle as an electric generator.

But then again, as you notice, there is a problem about using liquid metals as reactor coolants.

Sun-Tzu Class super-cavitating SC-SSK (layout idea 2)

That's a rocket propelled sub, Planeman?

Anyway, on a more serious note. Here are some direct evidence that the Chinese are working on a sub propulsion using an HTGR feeding a closed Brayton cycle turbine.



Power, power density and efficiency optimization for a closed cycle helium turbine nuclear power plant

Lin-Gen ChenCorresponding Author Contact Information, E-mail The Corresponding Author, a, Jun-Lin Zhenga, Feng-Rui Suna and Chih Wub
a Faculty 306, Naval University of Engineering, Wuhan 430033, PR China
b Department of Mechanical Engineering, US Naval Academy, Annapolis, MD 21402, USA
Received 15 August 2002; accepted 11 December 2002. ; Available online 11 February 2003.



Abstract

The performance of a closed cycle helium turbine nuclear power plant for submarine propulsion is optimized in this paper. The power output, power density (ratio of power output to maximum specific volume in the cycle) and thermal efficiency of the cycle are derived. The maximum power, power density and efficiency are obtained by searching for the optimum heat conductance distribution among the hot side heat exchanger (intermediate heat exchanger), cold side heat exchanger (precooler) and recuperator for fixed total heat exchanger inventory with respect to the corresponding optimization objectives. The optimum results are compared with those reported in recent references for the conceptual design of a closed cycle helium turbine nuclear power plant for submarine propulsion. The numerical example shows that the method herein is valid and effective.

Author Keywords: Helium turbine cycle; Power; Power density; Efficiency; Optimization; Optimum heat conductance distribution




Power optimization of an irreversible closed intercooled regenerated brayton cycle coupled to variable-temperature heat reservoirs

Wenhua Wanga, Lingen Chena, Corresponding Author Contact Information, E-mail The Corresponding Author, E-mail The Corresponding Author, Fengrui Suna and Chih Wub
aNaval University of Engineering, Faculty 306, Wuhan 430033, PR China
bMechanical Engineering Department, U. S. Naval Academy, Annapolis, MD 21402, USA
Received 28 June 2004; accepted 27 August 2004. Available online 18 October 2004.



Abstract

In this paper, power is optimized for an irreversible closed intercooled regenerated Brayton cycle coupled to variable-temperature heat reservoirs in the viewpoint of the theory of thermodynamic optimization (or finite-time thermodynamics (FTT), or endoreversible thermodynamics, or entropy generation minimization (EGM)) by searching the optimum intercooling pressure ratio and the optimum heat conductance distributions among the four heat exchangers (the hot-and cold-side heat exchangers, the intercooler and the regenerator) for fixed total heat exchanger inventory. When the optimization is performed with respect to the total pressure ratio of the cycle, the maximum power is maximized twice and the double-maximum power is obtained. Further, as the optimization is performed with respect to the thermal capacitance rate matching between the working fluid and the heat reservoir, the double-maximum power is maximized again and a thrice-maximum power is obtained. In the analysis, the heat resistance losses in the four heat exchangers, the irreversible compression and expansion losses in the compressors and the turbine, the pressure drop loss in the piping, and the effects of finite thermal capacity rate of the three heat reservoirs are taken into account. The effects of the heat reservoir inlet temperature ratio, the total heat exchanger inventory and some other cycle parameters on the cycle optimum performance are analyzed by a numerical example. The optimum results are compared with those reported in recent reference for the conceptual design of a closed-cycle intercooled regenerated gas turbine nuclear power plant for marine ship propulsion. The numerical example shows that the method herein is valid and effective.

Keywords: Thermodynamic optimization; Finite-time thermodynamics; Brayton cycle; Intercooled; Regenerated; Finite thermal capacity rate; Power optimization

The Russians appear to have a similar thoughts on a large double hulled conventional, though with a nuclear alternative.





Oops - Russians post 'secret' sub plan on web

By Adrian Blomfield in Moscow
Last Updated: 2:31am BST 13/09/2007

Foreign spies in Russia have been handed an unexpected gift by officials in the town of Sarov who accidentally posted details of a new top secret submarine on the local administration’s website.
# Russia stunned by Vladimir Putin's premier choice

The embarrassing leak followed what was supposed to be a confidential meeting between the commander of the secret submarine and officials in the closed town, which is home to Russia’s main nuclear research facility.
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Instead, overly assiduous officials wrote a press release that covered the meeting in minute detail, not only naming the prototype vessel’s commander as Capt Sergei Kroshkin but even revealing the project’s code number: 20120.

Other technical and tactical specifications were also given, including the submarine’s water displacement of 3,950 tonnes.

It was not until the story was dutifully picked up by local newspapers that officials noticed the slip.

The offending press release has now been removed from the website, and Russia’s navy, defence ministry and armament manufacturing industry have all denied the existence of project 20120.

Military analysts who have studied the data suggest the new craft, also named the Sarov, is similar in appearance — although much larger — to the fabled Soviet Kilo Class “Turbot” submarine, acknowledged as one of the quietest vessels in the world.

Leading Russian newspaper Kommersant said the leaked details suggested that the 20120 contained technology radically different from any other submarine in service.

It hypothesised that the Russian navy had revived, perhaps successfully, a Soviet era plan to install a small nuclear reactor on a diesel powered submarine — making it capable of patrolling underwater without surfacing for 20 days.

Current Russian submarines have to surface at least once every three or four days.

The revelations are the latest sign of Russia’s rapid rearmament.

The country’s defence budget has quadrupled since Vladimir Putin, the Russian president, came to power in 2000.

Earlier this year, Russia launched its first new-generation nuclear submarine since the Cold War while yesterday generals said they had successfully tested the world’s largest non-nuclear vacuum bomb — a device they christened “the Father of all Bombs”.

Still toying with the super-cavitating concept SSK.


(The internal arrangement is a German mid-90's Type-209-1400 design - it is merely representitive of a typical SSK layout. Obviously the details would be more like Chinese SSKs)

The raised foredeck houses a second large caviatation generator which covers the mast and retracts when not in use.

Evolved......

Added 10m plugs both forward and aft of sail to accommodate 8 x missile tubes forward (3 x 3 minus 1 - space used for torpedo transfer chute). The rear plug accommodates an AIP unit, and both plugs are used to increase the cells. The torpedo room is moved to the bottom deck.

The rear has also been redesigned to have a single ducted propeller and the rocket pack is fin-top mounted to ease reload when surfaced.

Planeman, your last design---the version with the pump jet---I like a lot better. I wasn't very intrigued with a supercavitating sub.

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Here is an article on China working on a magnetohydrodynamic drive.



Google translation.

Europe said that the Chinese submarine sprinkler new MHD not detectable (1)
2007-09-20 08:33:34 - The small and medium】 【View comments
The Chinese Navy has a pair of media experts said: China will be created in the next update of "sprinkler magnetic fluid" powered conventional submarines. This raises the NSL, including submarines international community's attention. The European facial is more famous "International Association of Naval Submarine League."

Europe said the new Chinese water MHD impossible to detect submarines
Data for: China superconducting magnetic fluid model submarine

They often include the participation of States in the Navy, the Navy's submarine construction and development of research and analysis. Following their New China "sprinkler magnetic fluid" dynamic analysis of conventional submarines.

A Chinese naval research institutions officials recently said: "China engaging in the preparation of the fourth generation of conventional submarines, will use magnetic fluid waterjet propulsion technology." Chinese officials expected to display the submarine design model is very similar to its appearance in the construction of 214 German submarine. Water jet propulsion technology in Europe has just begun in the early application. The Chinese navy's move, stating that they must begin to follow a more "international submarine design" trend. But for the Navy, will face a new test.

Facial Institute of Asian Development Advisory retired Navy declared: "The new submarine's first PLO and the European advanced submarine technology, in the same type of mode, the submarine on their design and manufacturing capacity in the rapid increase"

He said: "The Chinese Navy recently bought a group of Russian production of submarine-launched anti-ship cruise missiles, these missiles to be used" yuan "class and their" Song-class "improved models. This is done in the test. Mainly for their third generation of submarines to experiment. "

John said: "China has already begun developing the new 214 submarine similar to the German Navy used" a new active / passive confrontation underwater torpedo system (NAPTC). But there was no information indicating that these technologies are likely to come from the German Navy. But using magnetic fluid waterjet propulsion technology will greatly increase their new submarine underwater survival and combat anti-submarine detection capabilities. The current "Song-class" submarine, China can achieve the "minimum risk of being detected." New yuan-class submarines, can be described as "hard-detection capabilities." Their third-generation submarines, can be seen. These submarines will be used more deep waters. And are not detectable stage. "

He said: "MHD waterjet propulsion submarine technology, is the number of European naval submarine manufacturer of advanced technology, the initial begun to use the power of the latest technology submarine technology. France, Germany Navy in this area has very advanced development capabilities. In recent facial, the "international submarine technology discussion of research and development ", Chinese experts have made our presentation was shocked. Although the EU is also implementing "the arms embargo on the export" policy. However, that the Chinese Navy already has its own development of this new submarine technology capabilities. This makes us feel more surprises. So Personally, I believe that they have the submarine manufacturing technology, this is totally out of China's own invention and the creation of. "

Here are the three alternatives for a near future "ultimate" sub. The technologies are currently not in a practical state today, but can be so in the not too distant future.

1. All fuel cells, no diesels.

2. Pebble bed HTGR reactor, with helium gas feeding a closed loop Brayton cycle gas turbine. No steam generation stage period.

3. Probably the most radical. A liquid metal cooled reactor that is generating electricity directly (look ma, no turbines or generators) using magnetohydrodynamic princples, with the superheated magnetized liquid being used to induce electricity over coils. The electricity is then used to magnetize supercooled wire coils for a magnetohydrodynamic propulsion.