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Virginia class submarine PJ

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  • Virginia class submarine PJ

    The pump-jet propulsion of a submarine has long been a secret, as various aspects of the submarine's parameters can be deduced from the structure of the propellers. Here are some close-ups of the Virginia submarine's pump-jet , and with these photos, you can even restore the thrusters to their true form. I guess the pump-jet thrusters of the Virginia class submarine will not be very different from those of the Seawolf class submarine, so the structure of the pump-jet of the Seawolf class submarine can also be inferred from these photos.

    In these photos below you can clearly see the stator and rotor (propeller) of the PJ, with the rotor in the back and the stator in the front. The number of blades of the stator is uncertain, while the number of blades of the rotor (propeller) is 7.

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    The following picture may seem critical: by looking at the PJ you can even infer the number of blades of the stator. We can see the cover cloth covering the PJ, probably because of the wind, which makes the stator's blades protrude through the cover cloth.

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    The picture below is of the USS Connecticut, and my presumed propeller is not yet installed. By referring to USS Jimmy Carter's PJ, although the cover is covered, you can see that there is a "bulge" at the end of the cover, which is the end extension of the propeller, if there was nothing there, the cover would not be in this position, but would hang down by gravity.

    USS Connecticut:

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    USS Jimmy Carter:

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    In summary: The Virginia class submarine has the rotor at the rear and the stator at the front. The number of rotor blades is 7, and the number of stator blades I guess is at least 10 or more, maybe 16 or 18, similar for the Seawolf class submarines.

    V
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  • #2
    Sam. Can you say, with absolute assurance, that there is not another set of stators aft of the screw?

    David
    Resident Luddite

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    • #3
      Click image for larger version  Name:	Screenshot_20220325-001607_Chrome.jpg Views:	0 Size:	37.6 KB ID:	160305
      Last edited by redboat219; 03-24-2022, 09:30 PM.
      Make it simple, make strong, make it work!

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      • #4
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        Make it simple, make strong, make it work!

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        • #5
          Originally posted by He Who Shall Not Be Named View Post
          Sam. Can you say, with absolute assurance, that there is not another set of stators aft of the screw?

          David
          Sorry, I'm not an expert in this area, everything is just speculation, I think there isn't a set of stators behind the propeller, I might as well explain my analysis process. I divided the parts into A (the stators in front of the propeller and its deflector); B1 (the propeller) and B2 (the extension behind the propeller); and C (the large deflector).

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          So according to the picture, I think the installation order is: first install part A, then install part B (B1 and B2 I think are a whole), and finally dock part C with part A.

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          About whether there is a set of stators after the propeller, this question I have thought about before. If there is a set of stators after the propeller, then this set of stators needs to be fixed on the B2 part, which seems to be difficult, B2 with a certain curvature, and it seems to be smooth, if this set of stators set on the B2 part, it does not seem to be reasonable. That's why I think B1 and B2 are a whole component that rotates together. If there is a set of stators after the propeller, I think this set of stators should be a whole with B2, that is, B1 and B2 are separate parts. But according to the photos, the "invisible" stators are not fixed with B2.

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          V
          Last edited by Sam Victory; 03-24-2022, 08:52 PM.

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          • #6
            The stator of the "front stator" pump-jet thruster can make the water flowing into the rotor at the rear of the submarine produce pre-spin, which can play the role of uniform incoming flow and improve the rotor inlet conditions, thus improving the propulsion efficiency of the submarine and reducing the noise of the propulsion device; however, the propulsion efficiency of the rotor is slightly lower. The "rear stator" pump-jet thruster has a relatively high rotor propulsion efficiency because the stator can recover some of the rotor's rotational energy from the rotor wake. Most submarines use the "front stator" pump-jet thrusters, while torpedoes use the "rear stator" pump-jet thrusters.

            HMS Astute:

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            V

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            • #7
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              • #8
                Here is a old drawing of the Royal Navy S & T class SSN Pump jet. It shows no stators aft on this British boat. Would the American boats be similar? I wager to guess yes. Same math & physics apply. Stators aft would be more efficient flow - true, Why they appear on torpedoes with their limited stored energy. But with nuclear power in the case of a SSN/SSBN providing energy for the life of the boat essentially, the added complexity becomes unnecessary for any small efficiency gained in my opinion These blades on the rotor were fixed, but in dry dock the blade pitch could be varied. This illustration shows 18 blades.. The follow on Astute design images above suggest 11 blades. And the Virginia SSN' 7 blades. Probably carbon fiber to eliminate any resonating and replicable

                Steve
                Last edited by Albacore 569; 06-13-2022, 11:33 PM.

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                • #9
                  Click image for larger version

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ID:	162359And it looks like there is always an exception. Stators aft of propulsor on the French Le Triumphant SSBN's Model reflect reality, modelers speculations of a sensitive area, or misinformation? It maybe the habit of the French sometimes looking at a engineering problem differently, and their love for elaborate engineering? The Rubis SNN (French SNA) boats have stators forward of their propellors or experimented with pre stators to manage flow too. Below a 1/100 scale model in the Paris Maritime Museum.
                  Last edited by Albacore 569; 06-14-2022, 01:04 PM.

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                  • #10
                    Please refer to these written by this guy:

                    Originally posted by Sam Victory View Post
                    The stator of the "front stator" pump-jet thruster can make the water flowing into the rotor at the rear of the submarine produce pre-spin, which can play the role of uniform incoming flow and improve the rotor inlet conditions, thus improving the propulsion efficiency of the submarine and reducing the noise of the propulsion device; however, the propulsion efficiency of the rotor is slightly lower. The "rear stator" pump-jet thruster has a relatively high rotor propulsion efficiency because the stator can recover some of the rotor's rotational energy from the rotor wake. Most submarines use the "front stator" pump-jet thrusters, while torpedoes use the "rear stator" pump-jet thrusters.

                    HMS Astute:

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                    V
                    It is not surprising that some submarines have the stator behind the rotor and some have the stator in front of the rotor, obviously this is not uniform. Both have their own merits, for example the Seawolf class submarine has its stator behind the rotor, making it excellently silent, while some European country subs such as HMS Astute have its stator in front of the rotor.

                    Comment


                    • #11
                      Focusing back on the subject - The Virginia Class SSN's. Its seem clear the Virginia PJ's lack stators aft or the propulsor.

                      Steven

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                      • #12
                        OK. I've followed this thread from the start. Are you guys just flogging the topic to death or is anyone going to make a break, dash to the shop and, BUILD THE ****ING THING!???....

                        Enough verbal blather and 'research'. BUILD SOMETHING. Even if its only a paper mock-up.... BUILD SOMETHING!

                        Christ on a cracker!... nothing is getting done!

                        David
                        Task Master
                        Resident Luddite

                        Comment


                        • #13
                          Damn, Dave, I felt this one across then internet, and I wasn’t even logged in here.
                          Of the 40,000 men who served on German submarines, 30,000 never returned.”

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