09III/09IV (093/094) Nuclear Submarine Thread

[Hendrik_2000]

Look at this equation since h1=h2 the potential energy cancelled out Now rearranging the equation
P1-P2=1/2Rho(V1sq-V2sq) P1-P2 is the one that cause the cavitation is depend only on the speed V1.V2 there is no potential energy here
1 and 2 refer to 2 different time

 

[Hendrik_2000]

I believe Quickie is correct that the onset speed of cavitation is higher the deeper you go. I have read Tom Clancy's "SSN" and non-fiction "Submarine", in which he goes on to explain this phenomenon and how it applied to the Los Angeles class. Not a technical source, but I doubt Clancy made up the physics. His earlier work is imho rather well researched.

I think you confuse cavitation and detection The submarine may dive deeper but that is not to avoid cavitation but to hide in different temp layer of water. Water layer of different temp form boundary and echo is bounced back at the boundary of different layer

 

[MrCrazyBoyRavi]

I think you confuse cavitation and detection The submarine may dive deeper but that is not to avoid cavitation but to hide in different temp layer of water. Water layer of different temp form boundary and echo is bounced back at the boundary of different layer

nice logic.

 

[Totoro]

What palpable indications are there to "prove" that the natural circulation around reactor for submarines was for 093 class? I keep reading the translated paragraph and it seems just as likely that it was meant for the class coming after 093. Certainly there doesn't seem to be enough info to settle that question as some see it one way and some see it the other way. I personally assumed it was the 095 class because i read Henri K's comment about 095 having natural circulation. If 093 already had it, it woudln't really have been mentioned.

Then again, as we said, it's not a black or white issue. Sub A can maybe use natural circulation at 12 knots while sub B may use it at 24 knots.

 

[Blitzo]

What palpable indications are there to "prove" that the natural circulation around reactor for submarines was for 093 class? I keep reading the translated paragraph and it seems just as likely that it was meant for the class coming after 093. Certainly there doesn't seem to be enough info to settle that question as some see it one way and some see it the other way. I personally assumed it was the 095 class because i read Henri K's comment about 095 having natural circulation. If 093 already had it, it woudln't really have been mentioned.

Then again, as we said, it's not a black or white issue. Sub A can maybe use natural circulation at 12 knots while sub B may use it at 24 knots.

I think reading only the paragraph #994, then one could be partly excused to think that it may be referring to a new submarine -- though I think you'd be pretty hard pressed to suggest that considering the entire article (

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) that was linked does talk about the "second generation nuclear submarine" as having natural circulation cooling.

Then there's also Hendrik's post #1000 which seems to be from guancha, which further goes forward to say that the revelation means 093 and 094 have natural circulation coolling but that being the first generation of natural circulation cooling it is expected that future submarines will likely improve on it. It is worth noting that all this seems to be the speculation from guancha, but the author is working off the same information we are -- i.e.: the clear statement of the "second generation nuclear submarine" having natural circulation cooling. Interestingly the original guancha article seems to have been deleted, but I was able to find a version elsewhere

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relevant part

093型核潜艇

观察者网军事评论员表示，拥有大质量导弹发射能力的我国第二代核潜艇，应当就是094型弹道导弹核潜艇，装备12枚巨浪-2潜射导弹。早年中国第一代核潜艇在噪音控制水平上由于技术限制，事实上是非常糟糕的。处于航行状态的核潜艇不可能采用常规潜艇那样关闭主发动机降噪的方式来关闭核反应堆，使用静音的电动机来驱动。如果核反应堆不具备自然循环能力，为了保证安全，反应堆的主泵是不能关闭的，这会导致潜艇在不需要进行高速航行的时候出现不必要的噪声来源。而具备自然循环能力的反应堆，在一定功率值以下时，不需要开启主泵就能维持反应堆一回路的正常运转，保证反应堆安全的同时为潜艇输出所需要的推进和发电功率。

而核潜艇的日常巡航过程中，不会经常处于非常高的航速，如果反应堆具备自然循环能力，那么潜艇的大部分航行时间都可以处于一个较低的噪声状态。同为我国第二代核潜艇的093型核潜艇与094采用了一样的动力系统配置，曾有传言称，该型潜艇在国际海域曾表现出远超过西方国家想象的降噪水平，这其中降噪贡献最大的应当就是该型艇的核反应堆具备自然循环能力。

当然，093和094的反应堆毕竟只是中国研发的第一种具备自然循环能力的船用反应堆，在设计和技术水平上与国际先进水平相比尚有不足，不开启主泵状态下的反应堆输出功率所能提供的航速相比美国的“海浪”和“弗吉尼亚”差距还很明显。不过值得期待的是，中国下一代核潜艇必将使用具备更强自然循环能力的核反应堆，甚至达到国际先进水平。

====


So going back to what this means for 095, well I think it's really hard to argue that the contents of the article are talking about a new submarine that is under development. Instead I think it is pretty obvious they are talking about a submarine that had already been developed, which is also in the consistently repeated "second generation" of nuclear subs. That can only really mean 093/094.

Going back to Henri K's post, well I think his post (on April 12) and the Chinese award article (April 21) are not really related. Henri K's post talks about the new production facility at Huludao where he speculates partly on the 095 and what it may have, including VLS and natural circulation cooling, where natural cooling circulation would've been an expected feature on 095 anyway.
However, on April 21, that Chinese science/technology award article was released, showing coincidentally that whaddaya know, 093 actually already had natural circulation cooling all along.

So I think it's just partly happy coincidence that these two articles came out at about the same time (though the Chinese award article obviously is much greater in stature than Henri K's write up, as good quality as his content is), and it's also partly common sense to speculate that 095 would've had natural circulation cooling before we knew that 093 had it as well.


Therefore, based on the Chinese article, the way we should interpret 095's status is that it will likely feature a further improved implementation of natural circulation cooling than what is on 093.

 

[Totoro]

Thanks for the article. This is the first time I noticed it and read it. I concur, if the article is genuine, it does read as if 093 already used natural circulation cooling. To an unknown degree, but that is besides the point.

If true, what that suggests is also interesting: That 093 or 093a at least, should be pretty quiet when at low speed, probably as quiet as improved LA class but possibly even a bit quieter. At higher or medium speeds 093 should also use pumps so that would then bring it to same level as LA class.

What other sources of noise are there? Machinery not being put on rafts. We don't know about 093 for sure, but it seems very unlikely 093 doesn't have that feature as it is something pretty much known from 1970s.

Precise machinery made with very tiny tolerances. Due to computers which lead to better computer controlled milling, 093 should even be somewhat better than LA class here, as it is unlikely even US had better solutions in 1980.

Skewback propeller - both sides have it, and it also depends on computer power and computer controlled sensors to test the fine details of performance. Again, 093 should not be behind iLA in this regard either, considering the time LA was made in.

Size seems to be pretty much the same. Size would allow for more of insulation material and better rafting of the machinery. Even more so, due 20+ years of computer advancement, it is not unimaginable that automation is on 093's side, meaning less berthing space needed, meaning more space inside the same volume available for other things like insulation.

So with natural circulation cooling added on top of all that, something that i cant find as a feature on LA class and something that articles about its reactor seem to talk about as if it was omitted due to politics, it would appear as perfectly plausible that 093a (a least, with several more years of improvements) is near or even a bit ahead of improved LA when it comes to low speed noise that was in service in 1990s.

Whether that holds true today still is a matter of said LA boats being further improved mechanically. To my knowledge, they still have the same reactor, but perhaps it is plausible that they received brand new other machinery and propeller, perhaps some even after the year 2000, which would then reduce their noise levels further.

It will be interesting to follow the western naval related media after this newsbit, regarding their possible stance changes when it comes to 093 noise levels.

 

[antiterror13]

Would 093/095 double hull make it nosier than Western single hull SSN ?

 

[KIENCHIN]

What other sources of noise are there?

The Chillers in the US subs are custom built and is extremely quiet when compared to commercial ones. Commercially available chillers, the best available at the moment is at best 80 plus db at part load and much higher at full load.

 

[zaphd]

Look at this equation since h1=h2 the potential energy cancelled out Now rearranging the equation
P1-P2=1/2Rho(V1sq-V2sq) P1-P2 is the one that cause the cavitation is depend only on the speed V1.V2 there is no potential energy here
1 and 2 refer to 2 different time

There is an elementary mistake in your algebra. Discard the potential energy component, move P2 to the left and .5rhoV1sq to the right and you get P1-P2=1/2Rho(V2sq-V1sq). Also you are assuming P1 and P2 stay the same.

Say we choose P1 is the static pressure of the water before it interacts with the propeller and P2 is the static pressure at the part of the propeller where cavitation would happen. V1 is the speed of water before it interacts with the propeller, which can fairly be said to be zero. Correspondingly, V2 is the water speed over the propeller at the point where cavitation is most likely to happen. We now have P1-P2=1/2Rho*V2sq

Let P2 stay constant at the limit pressure where cavitation begins to happen, and increase P1 by going deeper, where there is greater hydrostatic pressure. This means the right side of the formula grows too, and you can have a larger V2 (aka water speed over the propeller) without decreasing the minimum static pressure P2 below a limit where you have cavitation. With a greater V2 you can now have a greater propeller rpm, and correspondingly greater submarine speed.

It's worth mentioning that despite this example supporting my claims, the Bernoulli equation is not the end all be all of hydrodynamics and reality is more complicated.

I think you confuse cavitation and detection The submarine may dive deeper but that is not to avoid cavitation but to hide in different temp layer of water. Water layer of different temp form boundary and echo is bounced back at the boundary of different layer

I doubt it. Clancy describes thermal layers separately. All I can do is point you to the source. I am not an expert on hydrodynamics, though I have played around with Bernoulli and Navier-stokes equations in a university level course in theoretical mechanics.

 

[Hendrik_2000]

There is an elementary mistake in your algebra. Discard the potential energy component, move P2 to the left and .5rhoV1sq to the right and you get P1-P2=1/2Rho(V2sq-V1sq). Also you are assuming P1 and P2 stay the same.

Say we choose P1 is the static pressure of the water before it interacts with the propeller and P2 is the static pressure at the part of the propeller where cavitation would happen. V1 is the speed of water before it interacts with the propeller, which can fairly be said to be zero. Correspondingly, V2 is the water speed over the propeller at the point where cavitation is most likely to happen. We now have P1-P2=1/2Rho*V2sq

Let P2 stay constant at the limit pressure where cavitation begins to happen, and increase P1 by going deeper, where there is greater hydrostatic pressure. This means the right side of the formula grows too, and you can have a larger V2 (aka water speed over the propeller) without decreasing the minimum static pressure P2 below a limit where you have cavitation. With a greater V2 you can now have a greater propeller rpm, and correspondingly greater submarine speed.

It's worth mentioning that despite this example supporting my claims, the Bernoulli equation is not the end all be all of hydrodynamics and reality is more complicated.


I doubt it. Clancy describes thermal layers separately. All I can do is point you to the source. I am not an expert on hydrodynamics, though I have played around with Bernoulli and Navier-stokes equations in a university level course in theoretical mechanics.

I think you confuse the terminology of static pressure and I do to. The static pressure above the submarine should be called potential energy
It is eliminated since at T1, T2 it is at the same height. So the height of the column doesn't come into picture here. I use Bernouli to simplify the argument I am aware actually the blade is more like Aerofoil but it is the same process

What they meant here is the static pressure at point of contact inside the control volume. Assuming you can shrink yourself small enough and can be inside the control volume. That is the pressure that you see or feel if the propeller is accelerated

P1-P2 is the unknown variable here and.the speed is the known variable Just to show that rotaion create vacuum therefore it function as vacuum pump!

It is terminology because the -1/2 RhoV2 is called velocity pressure and it is negative

As to Tom Clancy thing if that is the case why nation spend billion in research and make all effort to hide the propeller and instituted Cocom to prevent sale of CNC. Russia use the skull drudgery to get the CNC machine? When to avoid cavitation all you have to do is dive deeper

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