Kristjan Peterson
Member
Why was reciprocating engine and turbine engine why wasent there just reciprocating engine?
The engines
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Michael H. Standart
Member
In a word: Economies. White Star wanted to make the Olympic class liners as cost effective as possible, so they tended to stick with well proven technologies. The reciprocating engines couldf offer some reasonable speed and the waste steam that exhausted out of the engines at 9psi still had enough punch to spin that centre turbine and that third propellor.
Had White Star been interested in building a racy speed demon as Cunard was, they would have been better off with turbines, but they weren't, so the hybrid plant was what they needed to get reasonable speed without all the higher costs.
Had White Star been interested in building a racy speed demon as Cunard was, they would have been better off with turbines, but they weren't, so the hybrid plant was what they needed to get reasonable speed without all the higher costs.
Steffen Reichel
Member
Many reciprocating engies can expand into vaccum, so give exhaust steam with negative pressure, to the condensors, but this will have a very difficult altering and ranking process and a still very smooth operation. Not a good idea for a ship propusion system, were rpm and power output isn't like in a sawmill or power plant a more constant thing.
That's why most ships steam engines don't expand to negative pessure and exhaust steam with appoximately 1 bar - 2 bar pressure.
so economically this pressure is wasted, so an turbine does not depend on expansion of the volume, it depends on dynamic speed.
So if you have a condensator behind the turbine, well, even that low pressure steam will show enogh dynamic power for turning the turbine, thus agin power is produced and can be used, the pressure isn't wasted and the all around economic of the Propulsion plant is higher.
turbines cannot alter the rpm like reciporcatin engines, but do very well in the kind they were used on Titanic.
so Titanic had a very modern propulsion plant.
sincerely
Stef
That's why most ships steam engines don't expand to negative pessure and exhaust steam with appoximately 1 bar - 2 bar pressure.
so economically this pressure is wasted, so an turbine does not depend on expansion of the volume, it depends on dynamic speed.
So if you have a condensator behind the turbine, well, even that low pressure steam will show enogh dynamic power for turning the turbine, thus agin power is produced and can be used, the pressure isn't wasted and the all around economic of the Propulsion plant is higher.
turbines cannot alter the rpm like reciporcatin engines, but do very well in the kind they were used on Titanic.
so Titanic had a very modern propulsion plant.
sincerely
Stef
Samuel Halpern
Member
Hello Steffen: Good hearing from you again. Ships with reciprocating engines only did exhaust steam from their low pressure cylinders into condensers operating well below atmospheric pressure. There were a few ships that were designed with quadruple expansion reciprocating engines where the steam was expanded in 4 stages. But many ships had only triple expansion engines. A good example of a ship with large triple expansion reciprocating engines was the USS Texas (BB35). [see http://users3.ev1.net/~cfmoore/operating%20systems/engine%20room/asne-1914excerpts/1913standardizationtableIII.htm.] The Texas had two, 4-cylinder, triple-expansion engines. Each had 1 HP (39 inches dia.), 1 IP (63 inches dia.), and 2 LP (83 inches dia.), with 48 in. stroke. They ran at 125 rpm at 21 knots. The average pressure when running at full speed were 274 psig input to HP, 90 psia into IP, and 26 psia into LP cylinders. The LPs exhausted into main condensers which kept a vacuum of about 27 inches of mercury with outside pressure of 30 inches. (That's about 1.5 psia.) At 21 knots, the cutoffs were about 77-78% on HP and IP cylinders and 66% on LP cylinders.
Steffen Reichel
Member
Hello Commander Halpern,
of course did steamer with reciprocating engines exhaust their steam to condensators, in douple, triple or quadruple expansion types only from the low pressure cylinder. But there where tug boats which have double engines or quadruple engines which have in all cylinders live or superheated steam, and all exhaust their steam direct to condensators, and some tug boats, well, had realy fast running engines.
so even more modern engines with triple expansion often did not exhaust steam below pressure.
Of couse, it's more economically, but it's difficult with a main engine running at different rounds the vacuum levels in a condensator, produced by the vaccum condensate pumps do still alter, and thus the below zero pressure in the LP cylinder will not be constant, and will have sometimes negative effects on the main propulsion engine performance. thus in fast running engines, and engines which need to adjust their speed very often, if wasn't that economically as expected.
So many tug boats and speed boats doesn't have triple expoansion engines or double expansion engines which exhaust below zero pressure.
But as larger ships get, as more economically, because those ships travel more on constant speeds, as having that stop'n go movement.
And: Many triple expansions engines can be altered down to 55% cut-off, meaning only 55% of the cylinder volume was filled with steam, the rest volume was expansion space, and as larger engines get, as better the cut off, maybe going down to less than 25% if the quite running permit. Thus only if more power was need, the cut-off was higher.
In you exaample I guess, even with a triple expansion engine at 75% cut-off it wasn't realy economical, but very powerfull.
It'sall a kind or ranking, and I guess you can't compare a military ranked engine, with a passenger ships engine ranking.
sincerley,
Steffen
of course did steamer with reciprocating engines exhaust their steam to condensators, in douple, triple or quadruple expansion types only from the low pressure cylinder. But there where tug boats which have double engines or quadruple engines which have in all cylinders live or superheated steam, and all exhaust their steam direct to condensators, and some tug boats, well, had realy fast running engines.
so even more modern engines with triple expansion often did not exhaust steam below pressure.
Of couse, it's more economically, but it's difficult with a main engine running at different rounds the vacuum levels in a condensator, produced by the vaccum condensate pumps do still alter, and thus the below zero pressure in the LP cylinder will not be constant, and will have sometimes negative effects on the main propulsion engine performance. thus in fast running engines, and engines which need to adjust their speed very often, if wasn't that economically as expected.
So many tug boats and speed boats doesn't have triple expoansion engines or double expansion engines which exhaust below zero pressure.
But as larger ships get, as more economically, because those ships travel more on constant speeds, as having that stop'n go movement.
And: Many triple expansions engines can be altered down to 55% cut-off, meaning only 55% of the cylinder volume was filled with steam, the rest volume was expansion space, and as larger engines get, as better the cut off, maybe going down to less than 25% if the quite running permit. Thus only if more power was need, the cut-off was higher.
In you exaample I guess, even with a triple expansion engine at 75% cut-off it wasn't realy economical, but very powerfull.
It'sall a kind or ranking, and I guess you can't compare a military ranked engine, with a passenger ships engine ranking.
sincerley,
Steffen
Bob Godfrey
Member
Cunarders were generally faster, so maybe they used Ferrari engines.
James Smith
Member
Bob's pulling your leg, Alyson.
Titanic didn't have Rolls-Royce engines--I'm not sure where you came up with that. (I think Rolls might currently manufacture a pod-type propulsion system for ships, but they certainly weren't doing that in 1912.)
The newer engine technology was the turbine, which Cunard used in both the Lusitania and Mauritania. As Michael says above, Titanic's reciprocating engines were slower and based on an older design, but more economical to operate.
--Jim
Titanic didn't have Rolls-Royce engines--I'm not sure where you came up with that. (I think Rolls might currently manufacture a pod-type propulsion system for ships, but they certainly weren't doing that in 1912.)
The newer engine technology was the turbine, which Cunard used in both the Lusitania and Mauritania. As Michael says above, Titanic's reciprocating engines were slower and based on an older design, but more economical to operate.
--Jim
Michael H. Standart
Member
>>Were Titanic's Rolls-Royce engines more state of the art than the Cunard line fleet?<<
As James indicated, the Titanic's engines were not made by Rolls Royce. They were built by Harland & Wolff right there at the shipyard. The engines used on the two Cunard liners were Parsons steam turbines.
As James indicated, the Titanic's engines were not made by Rolls Royce. They were built by Harland & Wolff right there at the shipyard. The engines used on the two Cunard liners were Parsons steam turbines.
Stanley C Jenkins
Member
Rolls-Royce gas turbines are used to propel most of the larger ships in the British Navy, including the aircraft carriers Invincible, Illustrious and Ark Royal.
Michael H. Standart
Member
>>Um........I think i had it confussed with the car in side Titanic and the spitfire.<<
I don't know how. The Spitfire in most of it's versions was powered by an in-line water cooled Merlin which was a piston engine. (However, it was manufactured by Rolls Royce!)
I don't know how. The Spitfire in most of it's versions was powered by an in-line water cooled Merlin which was a piston engine. (However, it was manufactured by Rolls Royce!)
Trevor Rommelley
Guest
Nope, sorry, the engines were made by Zephram Cochrane
Bob Godfrey
Member
Ismay would have appreciated that. The Titanic could have left Southampton on April 10 and arrived in New York on April 9! A Blue Riband run for sure.
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