052C/052D Class Destroyers

[charles18]

Not necessarily. I'm not a naval engineer or anything but as far as I understand it, with mechanical transmission you have two sources of noise: the transmission, and the engine, both of which can be isolated from the hull by rafts even if they are connected to each other physically. In IEP, you also have two sources of noise: the electric motor, and the engine, both of which also can be isolated from the hull by rafts. I think which one is quieter in the end is whether the electric motor is quieter or the transmission is quieter rather than the fact that IEP has two separated sources of noise. I would amateur guess that an electric motor would be quieter compared to a mass of gears grinding each other along.

In a conventional ship you have an engine -> transmission-> drive shaft -> propeller
Even if the engine and transmission is placed on rubber dampeners to reduce noise the engine vibrations will still be transmitted to the ship's hull through the drive shaft. There's no way around it.
In an IEP system there is no drive shaft.
(maybe in the shipping world the proper term is propeller shaft not drive shaft but you get the idea)

 

[Iron Man]

In a conventional ship you have an engine -> transmission-> drive shaft -> propeller
Even if the engine and transmission is placed on rubber dampeners to reduce noise the engine vibrations will still be transmitted to the ship's hull through the drive shaft. There's no way around it.
In an IEP system there is no drive shaft.
(maybe in the shipping world the proper term is propeller shaft not drive shaft but you get the idea)

In an IEP system there is absolutely still a drive shaft. You must be thinking of rim drives ("rim-driven thrusters"), that's the only way I can see how your post makes sense. I have no doubt multiple countries are working on rim drive technology for main drive propulsion but AFAIK currently this technology is only in use for small propellor systems like the ones used for pier maneuvering or used as main drives on boats, rather than as main propulsion systems for large civilian or naval vessels. Probably this is coming down the road but we are not there yet.

By way of an example of IEP, here is Daring's propulsion system (notice the drive shafts):

 

[iBBz]

In an IEP system there is absolutely still a drive shaft. You must be thinking of rim drives ("rim-driven thrusters"), that's the only way I can see how your post makes sense. I have no doubt multiple countries are working on rim drive technology for main drive propulsion but AFAIK currently this technology is only in use for small propellor systems like the ones used for pier maneuvering or used as main drives on boats, rather than as main propulsion systems for large civilian or naval vessels. Probably this is coming down the road but we are not there yet.

By way of an example of IEP, here is Daring's propulsion system (notice the drive shafts):
View attachment 146665

I'm not an expert of marine engine configurations and don't know much about their firing orders either, but I'm thinking the benefit here could be that motors are smoother because they operate at higher frequencies than ICE engines, so that produces less vibrations. Am I correct in making this assumption?

 

[Iron Man]

I'm not an expert of marine engine configurations and don't know much about their firing orders either, but I'm thinking the benefit here could be that motors are smoother because they operate at higher frequencies than ICE engines, so that produces less vibrations. Am I correct in making this assumption?

Sorry but I have no idea if that's true or not. I do know that high frequency sounds do not propagate as far in the ocean environment as low frequency sounds, so there's that. OTOH I do not know how much sound and which frequencies get mitigated better/worse by the rafts and get transmitted through the hull. I do not even know which PLAN ships actually use rafts for noise attenuation purposes.

 

[Lethe]

In an IEP system there is absolutely still a drive shaft. You must be thinking of rim drives ("rim-driven thrusters"), that's the only way I can see how your post makes sense. I have no doubt multiple countries are working on rim drive technology for main drive propulsion but AFAIK currently this technology is only in use for small propellor systems like the ones used for pier maneuvering or used as main drives on boats, rather than as main propulsion systems for large civilian or naval vessels. Probably this is coming down the road but we are not there yet.

Podded electric propulsor units are used for main propulsion on some cruise ships, ice breakers, Naval Group's Mistral LHD and Navantia's Juan Carlos LHD and its derivatives for Australia and Turkey.

 

[Iron Man]

Podded electric propulsor units are used for main propulsion on some cruise ships, ice breakers, Naval Group's Mistral LHD and Navantia's Juan Carlos LHD and its derivatives for Australia and Turkey.

Oh yes, I do recall Juan Carlos using these now. I wonder why IEP ships don't use these in general.

 

[para80]

Because pods continue to have some distinct disadvantages, when it comes to maintenance and infrastructure requirements, when something does go wrong and needs repair. Furthermore they do add draft, which has implications for relevant landbased infrastructure, although there is some nuance based on exact configurations.

 

[Zichan]

I don't think anyone is saying one of IEP's pros is being quiet. Nonetheless, you have not shown that it is particularly noisy compared to other propulsion setups.


All other things being equal, a higher length to beam ratio is better for speed. For the Daring it's 7.19, while for the 052D it's 8.94.

As for CODOG (and COGOG), it's the worst of both worlds as far as space and efficiency is concerned. And more to the point, anything less than IEP is less space and weight efficient comparatively. Back to my original statement, there isn't anything about the Type 45 that makes it inherently inferior just because it has an IEP setup; the execution of the Type 45 is clearly lacking but AFAIK it's not the IEP itself that has been at fault. Clearly surface combatants can use IEP, and IEP can make use of less power generating sources (GTs/diesels) more efficiently than anything else. It's more a matter of cost and complexity than anything else. For smaller surface combatants like FFGs and DDGs, CODLAG is perfectly suitable if cost is an issue. Meanwhile for larger ships like 055 and follow-ons that may play host to more exotic weaponry, IEP makes perfect sense. I suspect the tradeoff in the space for losing a pair of GTs and the transmission and adding electric motors for the props, generators for the remaining GTs, and +/- batteries may actually favor the latter in terms of weight and space. A hypothetical 055A with IEP could maybe even add an extra pair of UVLS on the back end as a result.

The main advantages of IEP are:
1. Fuel economy
2. Improved survivability
3. Potentially better acoustics:

FREMM and Constellation use fixed pitch propellers, whereas GT ships typically require variable pitch propellers with worse acoustics.
Removal of noise contribution from reduction gears​

4. Lower maintenance

 

[blindsight]

I'm not an expert of marine engine configurations and don't know much about their firing orders either, but I'm thinking the benefit here could be that motors are smoother because they operate at higher frequencies than ICE engines, so that produces less vibrations. Am I correct in making this assumption?

And you probably don't need a gearbox, which helps too.

 

[ACuriousPLAFan]

A ship badge which belongs to one of the 4th batch 052DG DDGs, with the pennant #126 and named after the city of Heze. Posted by 太湖XXX.