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Author Topic: Maritime Engine types  (Read 980 times)

Offline Tzoli

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Maritime Engine types
« on: February 16, 2017, 08:04:27 am »
Hi!

Nowadays and in the past few decades the combined engine types of Steam and Gas, Gas and Gas, Gas and Diesel or Diesel and Diesel are quite popular propulsion systems for the various warships classes frigate size and up. These systems are quite versatile and economical to my understanding. I also know the difference between the OR and the AND versions. But there were mixed propulsion systems during the WW2 and pre WW2 eras as well. Like the mixed Steam and Diesel propulsion of most German warships.

My question is how would these mixed systems categorized with modern Combined systems?

Like would the mixed propulsion of the H class battleship designs or the Königsberg, Nürnberg and Leipzig class crusiers categorized as COSAD? (Combined Steam And Diesel) or COSOD? (Combined Steam Or Diesel)
Eg does they need all engines running at full power to achieve the maximum speed or only with turbines they could travel at max and the Diesels were turned off?
Many of the Yamato preliminaries too featured such mixed propulsion and I'm sure 60-70.000tons could not reach it's full speed on two shafts alone out of 4 if we think about two diesel and two steam powered shafts for economical or full speed runs.

Online Jemiba

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Re: Maritime Engine types
« Reply #1 on: February 16, 2017, 09:39:51 am »
...Like the mixed Steam and Diesel propulsion of most German warships

Not quite sure about this. The H-class was never finished, so the Königsberg and Nürnberg class
were the only fighting ships combining steam and diesel propulsion, AFAIK. According to Gröner, in the Königsberg
class the system clearly was COSOD, because the Diesel engines had to be shut down before using the steam
turbines and vice versa, so actually a kind of a handicap for any situation, when combat maneuvers had to be
expected. With Diesel only, the ship was limited to the speed of about 10 knots. There was a so-called "alarm
ignition" procedure, giving steam pressure "in some minutes" (?), but this probably was pricy and this method
is mentioned as only to be used "by bypassing all safety standards"
In the Nürnberg/Leipzig class it was a kind of COSAD. The ships had 3 shafts with only the inner one driven by Diesel
engines. The outer shafts could be driven electrically to avoid drag losses, when the steam propulsion was shut
down. Full power meant steam + Diesel here.
« Last Edit: February 16, 2017, 11:15:56 pm by Jemiba »
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Offline Tzoli

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Re: Maritime Engine types
« Reply #2 on: February 17, 2017, 09:12:41 am »
So if both engine types used on the same shaft that means a COSOD type as the diesel could not provide the extra shaft horse power next to the turbine?

Online Jemiba

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Re: Maritime Engine types
« Reply #3 on: February 17, 2017, 12:19:14 pm »
Such was the arrangement on the ships of the Königsberg class, yes. There probably were
other types, were both engine types could work simultaneously on one shaft, but I'm not aware
such a type in the German navy. In the Leipzig class, the ship could use Diesel and steam turbines
simultaneously, as the Diesel engines were driving the central shaft only. If you look at the arrangement
drawings explaining all those combined engine arrangements, generally using the same shaft is meant,
I think. So in the Leipzig/Nürnberg it was a kind of a trick and I'm not sure, if it qualifies as a real COSAD
arrangement in the true sense.
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Offline Tzoli

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Re: Maritime Engine types
« Reply #4 on: February 20, 2017, 10:34:15 am »
Question would be, what arrangement to be used on the Yamato preliminaries?
Because you sure need 4 shafts to move 60-70.000 standard tons (lightest being A-140 D with 55.000tons and all diesel) and for max speed I'm not sure two shafts will be enough to go at max rotation.
I'm not an expert in water flow but probably having 3 or 4 shafts in which 2-1 or 2-2 moves at a different speeds are not helping to reach the desired speed.

Offline Tzoli

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Re: Maritime Engine types
« Reply #5 on: March 06, 2017, 08:38:34 am »
Another question:
Is there any difference if I use COSAD or CODAS arrangement? Am I suspect that the firs letter designates the main propulsion type?