High pressure and low pressure turbines

Propulsion systems, machinery, turbines, boilers, propellers, fuel consumption, etc.
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Karl Heidenreich
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High pressure and low pressure turbines

Postby Karl Heidenreich » Mon Sep 21, 2009 2:16 am

It has been brought to my attention that, at least, the British designs consist of sets of low pressure and high pressure turbines. But the logic, at least my mistaken one, is that you used them complementary. But in the British designs, let´s say, the Queen Elisabeth Class, the arragement was the following:

One low pressure ahead and one high pressure astern, in the same casing, on the inner shaft.
One high pressure ahead and one high pressure astern on the wing shaft.

In Repulse, on the other hand, we had:

Two high pressure turbines on the wing shaft
Two low pressure turbines on the inner shaft

And Hood:

All sets consisted of a high pressure and a low pressure turbine

It seems to me that the logic is that, at least in QE or Repulse designs all shafts must have the same arragement in order to have the same SHP and rpm. Isn´t it? Which is why I brough up Hood that is designed upon that logic.

Best regards,
An appeaser is one who feeds a crocodile, hoping it will eat him last.
Sir Winston Churchill

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marcelo_malara
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Re: High pressure and low pressure turbines

Postby marcelo_malara » Mon Sep 21, 2009 4:04 am

Hi Karl. In ships with direct connection between turbines and shafts (ie: no reduction) you can not match the different rotating speeds between low and high pressure sets if they are disposed in the same shaft. So commonly you have a high pressure set on one shaft, exhausting to a low pressure set on another shaft, and this duplicated to provide for four shafts. This corresponds to Repulse and the QE class before modernization. Hood introduced single reduction, in which you can connect a high pressure and a low pressure set on the same shaft, as they first are coupled to an intermediate wheel, each set with a different number of teeth to support the different rotating speeds.

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marcelo_malara
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Re: High pressure and low pressure turbines

Postby marcelo_malara » Mon Sep 21, 2009 4:09 am

Some data from Hood:

Shaft gear wheel: 392 teeth
HP turbine: 55 teeth
LP turbine: 75 teeth

From AOTS (I am sorry that Raven & Roberts is missing this data!!!)

Regards

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Karl Heidenreich
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Re: High pressure and low pressure turbines

Postby Karl Heidenreich » Mon Sep 21, 2009 12:01 pm

Marcelo:

Thanks for the info! I do believe that Raven and Roberts give for granted that the guy that it´s reading it already know that. Which in my case was not so. Now I learn something new.
An appeaser is one who feeds a crocodile, hoping it will eat him last.
Sir Winston Churchill


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