Bismarck's engine spaces

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Re: Bismarck's engine spaces

Post by dunmunro » Tue Nov 05, 2013 3:26 am

sineatimorar wrote:I thinkyou are reading too much into a probable 800kg weight difference. As far as a measure of efficiency of a boiler is measured, a boiler of small size that physical weighs the same as a supposed larger type suggest more internal heating surface for a given area. Therefore a boiler that is smaller, produces higher water temperatures and pressure is usually considered more efficient than a larger boiler producing lower pressure and temperature.

The efficiency of a boiler can not be directly measured in shp produced by the turbines attached to it. Shp is a direct measure of turbine efficiency not boiler efficiency so the correct argument would be to question overall turbine efficiency instead. Normally higher pressure and temperatures of the feed water, or more correctly the super heated steam that is produced by the heating of the feed water, equates to higher turbine efficiency, so what happened in this case is interesting.
You keep forgetting that KGV had 8 boilers producing ~17000shp/boiler versus 12 in Bismarck producing ~13000shp/boiler, so the SHP per boiler (and thus steam production) in KGV was 30% greater than in Bismarck. Bismarck's boilers were very heavy for their output because the pressure vessel needed to be constructed of very thick steel to handle the extreme pressures and temperatures, yet despite this they displayed much less efficiency than their RN counterparts. Theoretically, a 3 shaft turbine arrangement should be more efficient than a 4 shaft PP, of similar SHP because the 3 shaft unit will have larger, higher output, turbines that are inherently more efficient (turbine efficiency increases with output, assuming similar turbine speeds).

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Re: Bismarck's engine spaces

Post by sineatimorar » Tue Nov 05, 2013 6:46 am

From this web site dry weight is 47.5 tons wet weight is 52.8 tons. What was the weight of the kgv boiler again?

READ my last post very carefully. Shp production is via the turbines ability to change the force of the steam hitting the blades into a rotational moment / effect. Boiler efficiency is how efficiently it heats the feed water for a given surface area or heating surface. Yes there seems to be inefficiencies as a greater pressure and heat usually translates to more energy available to the turbines. As you say the British did it with less boilers so the loss has to be in the turbine design. You got me thinking now and I will refer back to my turbine / boiler design texts to see if I am missing something or if I can explain myself in a clearer manner. Something as simply a incorrect steam nozzle choices of design can completely screw up the energy transfer mechanism. One area could be the hiatus in ongoing naval development after the WW1 could have delayed developments in turbine design in Germany.
The Americans went down the same pathway as Germany and got some very extreme results in efficiency with less boilers.

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Re: Bismarck's engine spaces

Post by Thorsten Wahl » Tue Nov 05, 2013 7:56 am

Bismarck one boiler complete weight
with water 63.1 metric t,
without water 53.6 metric t(built in weight)

from Plan M I - Gewichte; Bauwerft Blohm & Voss Hamburg; Baunummer 509; Schlachtschiff "Bismarck" from April, 1st, 1940.

I think the sheer number of boilers is owed to the strive for redundancy.
3 independent powerplants each feed by two boiler rooms each of it contains two boilers.
in case of failure/damage of sub-components, the failed system could be replaced crosswise.
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Re: Bismarck's engine spaces

Post by sineatimorar » Tue Nov 05, 2013 10:38 am

After further investigation I believe this is another case of 'selective' quotation of facts. The 17,000 shp figure is reflective of a overload power settings for the kgv, while the 13,000 figure is reflective of the standard power setting for the Bismarck.

A more accurate comparison would be to quote from nominal power settings for BOTH ships. The nominal output for the Kgv is 110,000 shp which equates to 13,750 shp output from each boiler if you want to accept that analogy compared to a nominal output of 138,000 shp for the Bismarck equating to 11,500 shp per boiler. Yes it is less than kgv at the same steaming conditions.

But and it is huge but, the true measure of output relates to shp delivered at the propeller and this is where the whole argument falls apart. Each shaft of the Bismarck nominal design output was 46,000 shp per shaft compared to 27,500 shp per shaft on the kgv. That is 19,500 shp less than the Bismarck!

If we look at wartime settings you get 50,056shp for the BS and 33,500shp for Kgv, a total difference of 16,556 shp in the favour of the BS. Which explains the the 2 knt speed advantage by the way.

Remember the efficiency of a boiler is measured ONLY on it's ability to heat water to steam, that and that alone.
The unit of shaft horse power is a measure of applying a rotating work force or moment to a rotating SHAFT hence it name SHAFT horse power. Strange as it might seem this shaft is not installed in the boiler. Funny that no?

In conclusion the inefficient German boilers produced via the supposedly inefficient turbines between 16,556 inefficient shp to 19,500 inefficient shp MORE than the supposedly more efficient British ship. In any man's language the argument is 'BUSTED'

Q.E.D.

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Re: Bismarck's engine spaces

Post by dunmunro » Tue Nov 05, 2013 11:27 am

sineatimorar wrote:After further investigation I believe this is another case of 'selective' quotation of facts. The 17,000 shp figure is reflective of a overload power settings for the kgv, while the 13,000 figure is reflective of the standard power setting for the Bismarck.
17000 and 13000 are both overload figures.
A more accurate comparison would be to quote from nominal power settings for BOTH ships. The nominal output for the Kgv is 110,000 shp which equates to 13,750 shp output from each boiler if you want to accept that analogy compared to a nominal output of 138,000 shp for the Bismarck equating to 11,500 shp per boiler. Yes it is less than kgv at the same steaming conditions.
The nominal designed output of Bismarck was 111000shp but she attained 118000, IIRC. 138,000 was the original designed overload power but Bismarck achieved 150000 and Tirpitz 163000shp, according to Koop. KGV was designed for 110,000 but made 112000 on trials. PoW achieved an overload of 134000shp but this probably didn't reflect maximum possible overload.
But and it is huge but, the true measure of output relates to shp delivered at the propeller and this is where the whole argument falls apart. Each shaft of the Bismarck nominal design output was 46,000 shp per shaft compared to 27,500 shp per shaft on the kgv. That is 19,500 shp less than the Bismarck!

If we look at wartime settings you get 50,056shp for the BS and 33,500shp for Kgv, a total difference of 16,556 shp in the favour of the BS. Which explains the the 2 knt speed advantage by the way.

Remember the efficiency of a boiler is measured ONLY on it's ability to heat water to steam, that and that alone.
The unit of shaft horse power is a measure of applying a rotating work force or moment to a rotating SHAFT hence it name SHAFT horse power. Strange as it might seem this shaft is not installed in the boiler. Funny that no?

In conclusion the inefficient German boilers produced via the supposedly inefficient turbines between 16,556 inefficient shp to 19,500 inefficient shp MORE than the supposedly more efficient British ship. In any man's language the argument is 'BUSTED'

Q.E.D.
[/quote]

Again, turbines run on steam. Fewer, higher output, boilers are more efficient at producing steam than more numerous, but lower output boilers. The fact that the KM stayed with 12 boilers (of similar weight and output) in the Hipper, Scharnhorst and Bismarck classes, probably reflected an inability to design higher output boilers, forcing the need for large numbers of boilers.

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Re: Bismarck's engine spaces

Post by dunmunro » Tue Nov 05, 2013 11:44 am

Thorsten Wahl wrote:Bismarck one boiler complete weight
with water 63.1 metric t,
without water 53.6 metric t(built in weight)

from Plan M I - Gewichte; Bauwerft Blohm & Voss Hamburg; Baunummer 509; Schlachtschiff "Bismarck" from April, 1st, 1940.

I think the sheer number of boilers is owed to the strive for redundancy.
3 independent powerplants each feed by two boiler rooms each of it contains two boilers.
in case of failure/damage of sub-components, the failed system could be replaced crosswise.
Thanks. I thought the data in Koop was inconsistent regarding boiler weights for Hipper, Scharnhorst and Bismarck, and it seems that they are all actually very similar in weight.

The general trend in marine steam plants, worldwide, prior to WW2 was toward fewer, but higher output boilers and the KM seems to have lagged in this respect. I note that the proposed heavy cruiser Seydlitz would have gone to 9 boilers.

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Re: Bismarck's engine spaces

Post by sineatimorar » Tue Nov 05, 2013 11:56 am

We are basically attacking this argument from completely different directions. I will try an analogy of another human endeavour, that of car racing. We have in Australia a famous car race called the Bathurst 1000. It been around since the early to mid 1960's. Back in the early days a morris mini s coupe won the race with approximately 100 hp running into the ground the muscle car v8's with more than 400 horses under the bonnet. The result had absolutely nothing to do with engine power, but everything to do with the OVERALL PACKAGE that 100 hp was packaged in. Again YES the Wagner boiler maybe considered inferior to the British boiler using your argument.
BUT the OVERALL package in the Bismarck is clearly able to produce a greater TOTAL package using less 'wheels' in the process. As Thorten points out your argument ignore the possibility of 'Battle redundancy' been the reason. Simple put they did not have to push the possible output to a higher level as they had the space to put 12 boilers in the hull anyway. They had no need so why push it? There arrangement no matter how many boilers were used was MORE EFFICIENT IN THE OVERALL PICTURE.

Output of a boiler is measured in steam pressure and steam temperature. In both measures the Wagner boilers had a greater output flow of superheated steam than the units used in the Kgv. It is relatively easy to confirm this from a number of sources.

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Re: Bismarck's engine spaces

Post by dunmunro » Tue Nov 05, 2013 12:32 pm

sineatimorar wrote:This getting pointless, we are basically attacking this argument from completely different directions. I will try an analogy of another human endeavour, that of car racing. We have in Australia a famous car race called the Bathurst 1000. It been around since the early to mid 1960's. Back in the early days a morris mini s coupe won the race with approximately 100 hp running into the ground the muscle car v8's with more than 400 horses under the bonnet. The result had absolutely nothing to do with engine power, but everything to do with the OVERALL PACKAGE that 100 hp was packaged in. Again YES the Wagner boiler maybe considered inferior to the British boiler using your argument.
BUT the OVERALL package in the Bismarck is clearly able to produce a greater TOTAL package using less 'wheels' in the process. As Thorten points out your argument ignore the possibility of 'Battle redundancy' been the reason. Simple put they did not have to push the possible output to a higher level as they had the space to put 12 boilers in the hull anyway. They had no need so why push it? There arrangement no matter how many boilers were used was MORE EFFICIENT IN THE OVERALL PICTURE.

Most historical account place nominal output per shaft of the Bismarck at 46,000 shp each. I would be interested in obtaining the source reference for the 110,000 shp figure.
I originally commented on the size and weight of Bismarck's 12 boilers and how their output contribution, per boiler, to overall SHP was lower than in KGV and many other contemporary RN ships. The obvious conclusion is that fewer but higher output boilers would have reduced Bismarck's machinery weight and volume while increasing overall efficiency as was implemented by the RN and other navies.

HMS Hood produced more power on trials than Bismarck and Hood had 24 boilers...so does that make Hood's PP better than Bismarcks?

Read Koop's Battleships of Bismarck class, p19.

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Re: Bismarck's engine spaces

Post by sineatimorar » Tue Nov 05, 2013 1:29 pm

Sorry for the shortness of my reply I did edit somewhat to more reasonable tones.
As I said we are probably tackling this from completely different directions. While I am tackling it from the point of a boiler been solely a source of heat energy transferred by a liquid agent using the properties of H2O. You are tackling the question of efficiency via comparative look at the number of boilers required per shp. I think we are looking at the same thing using completely different, but equally accurate, point of references. You could say I am holding to the purely technical point of view on describing boiler efficiency while your argument highlights a interesting correlation between the number of boilers and shp production that is seemingly in conflict with the standard description for boiler efficiency.

I hope I am not trying to teach a steam generation engineer how to ' suck a egg' here, but I do have in-depth technical texts that deal with energy transfer inside a turbine, where I think our arguments actual meet, that I might be able image a copy of pages dealing with this to your email if you prefer. I have not as yet mastered attaching images to this forum directlly.

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Re: Bismarck's engine spaces

Post by Herr Nilsson » Thu Nov 07, 2013 2:31 pm

sineatimorar wrote:Some clarification please about problems listed

1./ Is there not some sort of braking method used in either system? I think in either case there would have to be a transition stage as you could not just apply full reverse power and expect the everything to instantly be going in the other direction. The Yanks did not seem to have an issue with it.

2./ What structural changes would have resulted in the inner shaft and prop to have been affected by rudder changes? Three shaft arrangement was never going to change.

3./ In either case the three shafts rotated or would have rotated at the same revolutions any case. Any harmonic vibrations or vibrations from interference from the other propellers is simply avoided by not setting the power output at a level that created them in the first place. I believe that is the standard operational method.

If avoidance was required by alteration to the design instead the usual practice is change propeller design between shafts.

And how does any these issues relate to overall displacement other than the general weight differences of the plant types in question.

I will again state the most mentioned reason for the lack of any turbo electric plant seems to have been a disagreement between the amount of time required for development of the design between the desired manufacture and the navy high command.

I as yet to find a more plausible suggestion.
1. No mechanical brakes were used on geared turbines. They were stopped by the reverse turbines. There were some brakes on turbo electric machineries used in other German ships. The reversing of a turbo electric system was much more complicated. The Americans used asynchronous motors while the Germans would have used synchronous.

2. The geared turbine set had a similar problem which was later criticized. It was suggested that the shipyards had to guarantee a 20% higher torque for the whole machinery than necessary for top speed.

3. I was referring to cruising speed. One generator supplies energy for all three propellers.


The Kriegsmarine memo (written after 1944), in which the 3 reasons are mentioned, states that the problem couldn’t be solved with best technology available at that time (1936) without exceeding the 42,000 tons limit of the whole ship. It also states that the turbo electric machinery should be further studied for battleship H. While all German battleships from Scharnhorst to Tirpitz were built just to match their French counterparts, H was the first one which was designed as a raider. That’s the reason why the turbo electric propulsion was finally dropped and led to the Diesel engine propulsion of the H-class.
Regards

Marc

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Re: Bismarck's engine spaces

Post by sineatimorar » Fri Nov 08, 2013 11:10 pm

Thanks for the clarification. On your third point, is that why a ' cruising turbine was fitted to the Tp? Other than range economy.

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Re: Bismarck's engine spaces

Post by sineatimorar » Wed Nov 27, 2013 11:03 pm

Further on the boiler debate. The answer is written in Battleships: Axis &Neutral Battleships of WW2 pg 292. The reason for the number of boilers is clearly stated and where the overall system inefficiencies lay. In the turbine design choice. The German units were not high pressure high speed turbines driving thru double reduction drive as in western Navies. They were high pressure low speed turbines driving thru single reduction drive. Completely different units requiring completely different number of boilers to obtain similar power outputs. Any comparison to the western navy system is like comparing the efficiency of a diesel engine to a petrol engine. Both use piston and cranks and are both engines, but are completely different systems when it comes to how they produce their power. For any comparison to be valid you would have to connect the Wagner boilers to high-speed double reduction geared turbines and then and only then would any boiler efficiency be comparable.

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Re: Bismarck's engine spaces

Post by Jogi Balboa » Sun Dec 01, 2013 3:39 pm

Bismarck class 2800 rpm and 12 boilers
King George V class 2200 rpm 8 boilers
So :?: :?: :?:

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Re: Bismarck's engine spaces

Post by tommy303 » Mon Dec 02, 2013 6:50 pm

I was under the impression that only the USN made widespread use of double reduction gearing and that everyone else used single reduction gears?

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Re: Bismarck's engine spaces

Post by Jogi Balboa » Mon Dec 02, 2013 8:39 pm

I was under the impression that British made use of low pressure and low speed turbines and so few of fuel compared to high parameter USN and German ;)

Sorry for my English :)

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