Engine Design


Jim Hathaway

Member
Dec 18, 2004
311
0
111
I was wondering what benefit the mixed reciprocating engine/turbine installation gave to be used in the Olympic Class-
I am speaking versus a straight reciprocating or straight turbine installation.
I was under the impression that the installation in Laurentic was partly experimental to gain experience with turbines, it suprises me that White Star would specify it for what would become thier flagships unless there was a concrete benefit.
Was it simply conservative engineering?
Jim Hathaway
 
Dec 2, 2000
58,641
457
453
Easley South Carolina
More like economical engineering. White Star wasn't trying to compete with the Cunard speed queens, so there was no benefit to an all turbine plant. The combination reciprocating/turbine plant was just more economical.
 

Jim Hathaway

Member
Dec 18, 2004
311
0
111
Thanks, Michael, it makes sense, but still a strange installation for a production ship-
Have a great Christmas-
Jim
 
Dec 2, 2000
58,641
457
453
Easley South Carolina
Strange by our reckoning to be sure, but it made sense for White Star when what they were looking at was the bottom line. The reciprocating engines did the lions share of the muscle work with the exhaust steam being used once more to run the turbine. The result was more efficient use of the steam and a more economical ship to operate.
 

Jeremy Lee

Member
Jun 12, 2003
1,374
2
161
The Cunard engines of the Mauretania and Lusitania were much heavier and were not as economical I guess?

Titanic's engines were much less powerful, especially in terms of horsepower.
 
Dec 2, 2000
58,641
457
453
Easley South Carolina
I don't know that the turbine plant on the Mauritania and Lusitania was heavier, but it certainly had a lot more power. The *catch* is all that extra power to give you all that speed extracts a price in the fuel you guzzle down. In short, speed costs. White Star was not really interested in record breakers. What they wanted were large comfortable ships that were fast enough to carry the mails and maintain a service with weekly sailings from both sides of the Atlantic. For this purpose, 21 knot ships were plenty fast enough and were not as expensive to operate.
 

Jim Hathaway

Member
Dec 18, 2004
311
0
111
I was just able to answer my question with a paper available on-line.
The Rede Lecture by Sir Charles Parsons, in it's 3rd section has a few paragraphs about mixed powerplants using a low pressure turbine such as Titanic and Laurentic had.
In the paper he states "a slow speed turbine expands low pressure steam much furthur and more economically than any reciprocating engine. Under this system, the turbine generally is made to develop about 1/3 of the whole power.
He mentions the first combination vessel, the Otaki with twin screws driven by triple expansion reciprocating engines exhausting into a center low pressure turbine driving a screw.
Parson's paper says Otaki consumed 12% less coal than her sister driven by four reciprocating engines.
He goes of to say that Laurentic, in service realized a 14% savings of coal consumed over the same speed as her sister Megantic with a pure reciprocating engine plant.
Mauretania's turbines were of high pressure design, Titanic's was of a low pressure design operating on 9 psi exhaust steam.
The link to this paper is below-
http://www.history.rochester.edu/steam/parsons/index.html
Jim Hathaway
 
Dec 23, 2004
68
2
88
The main reason for using reciprocating engines on the Olympic Class was for economy. Reduction Geared Turbines were not an issue in 1911 and all Turbine installations were direct drive with high propellor speeds and they were heavy on steam therefore heavy on fuel compared with later designs. The disadvantage of turbines is you need a separate set to go astern. Titanic's main engines could,as with any recip. set be reversed easily and when maneovring the turbine did nothing - two large gate valves diverted steam from the recip. engines direct to the condenser.
 

Jim Hathaway

Member
Dec 18, 2004
311
0
111
Thanks, Allan,
The paper mentions reduction geared turbines, but I got the impression that it was still experimental when the paper was delivered (1911)
I printed it out, it will provide interesting reading today-
Jim Hathaway
 

Jim Hathaway

Member
Dec 18, 2004
311
0
111
Because the turbine engine was using exhaust steam from the boilers, it would be proportional to the power being produced by the reciprocating engines.
I am curious if the turbine had any provision to be throttled independently, or whether the turbine was either on line or off line.
 
Dec 23, 2004
68
2
88
It would appear that the turbine would only be operational once the two reciprocating engines had been started and exhaust steam was available. In order to take the Turbine off line two very large valves were fitted to divert exhaust steam from the LP cylinders of the reciprocating engines either a) to the condensers, or B) to the turbine. What fine control these valves allowed I have yet to research. Bedtime reading for Christmas Night!
 

Jeremy Lee

Member
Jun 12, 2003
1,374
2
161
BTW, if I remember correctly, Titanic and Olympic's engines could produce 45,000hp while Mauretania and Lusitania's could do up to 70,000hp.

A great difference!
 
Mar 22, 2003
5,831
1,104
383
Chicago, IL, USA
www.titanicology.com
The turbine was engaged when they ran the reciprocating engines at 50 rpm and greater. This corresponded to half ahead. There appears to be no throttling provision between reciprocating engine exhaust and turbine input. The piston changeover valves were either set to direct reciprocating engine exhaust to the turbine or directly to the main condensers. The reciprocating engines exhausted steam at a pressure of 9 psia. Main condensers were kept at a pressure of 1 psia with the vacuum pumps. You would not be able to keep a differential of 8 psi between turbine input and turbine output unless the changeover valves completely blocked steam from going to the main condensers when the turbine was put in operation.
 
S

Scott R. Andrews

Guest
Sam,

You are correct that there was no throttle control per se for the turbine; basically, the turbine simply responded proportionally to the amount of exhaust being received from the reciprocating engines. The changeover valves did, however, provide some limited speed control as there was an automatic override of the starting platform's turbine controls whereby the turbine's Proell centrifugal governor actuated the Brown's engine which operated the two piston valves. If the speed of the rotor reached 10% above the maximum number of revolutions dialed in by the engineerings, the piston valves redirected steam directly to the condensers until the speed dropped below the preset limit. That's about the extent of the engineer's ability to fine-tune the speed at which the turbine rotated.

Regards,
Scott Andrews
 
Mar 22, 2003
5,831
1,104
383
Chicago, IL, USA
www.titanicology.com
Yes, thanks Scott. I forgot about the governor for the turbine. They also had Aspinall governors on each reciprocating engine which worked with a Brown's engines that controlled the reciprocating engine's throttle value in case it started to race. In either case, I would consider these to be overspeed controls.
 

Jim Hathaway

Member
Dec 18, 2004
311
0
111
Thank all of you for excellent information, as to Aspinall governor, I am most familiar with prop governors for aircraft. I assume it worked on the same principal i.e. flyweights opposing tension of a speeder spring, and moving a spool valve controlling oil to the prop dome (or valve actuator)
Parson's paper I referenced in another post is answering quite a few questions for me too-
I found a copy of "Power Of The Great Liners" at bookfinder.com, it should answer more questions when it arrives.
Thanks again, you have given me more to study and become familiar with.
Jim Hathaway
 
S

Scott R. Andrews

Guest
Jim,

The Aspinall governors of the reciprocating engines didn't operate on the same principal as the familiar Watt or Proell type governors. This type of governor was usually affixed to either a pump lever or other lever driven by one of the crossheads (in Titanic's case, it was the latter, as all auxiaries were driven independant of the main engines). While a bit more difficult to explain than a centrifugal governor without the aid of diagrams and drawings, the basic concept is that there was a pair of spring-loaded pawls with a sort of floating lever positioned between them. This lever was connected by rods and bellcranks to overriding gear of the small hydraulic cylinder which actuated the throttle plate installed between the stop/manuvering valve and the high pressure receiver. The entire governor assembly oscillated with the lever, and as long as there was no sudden acceleration, all of the parts of the governor remained static in relation to one another. If the engine suddenly accelerated, as in the case of a propeller partially or completely breaking the surface, the sudden change in velocity caused one of the pawls to swing outward and catch the throttle override lever, causing the throttle plate to close until the revolutions began to drop. The device was also designed so that in the cases of really severe acceleration and/or repeated racing such as might be experienced in the case of a dropped propeller or broken shaft, the governor would lock the throttle in the closed position until the engine was stopped and one of the engineers manually reset the pawls.

Scott Andrews

PS - Aspinall also made a type of governor for turbine engines as well, though I have never seen a photo or drawing of one of these.
 
S

Scott R. Andrews

Guest
Hi Sam,

Yes, I saw that site, too, while doing a quick search to see if there was any online source I could steer Jim to for a drawing of the Aspinall governors for reciprocating engines. I've got plenty of reference material showing the recip engine type at home (I'm away visiting relatives for the holidays and have nothing available to me here), but nothing showing the Aspinall turbine engine governor. By the way, I've seen numerous other mentions of this turbine governor contemporary to the Titanic including, IIRC, the Aquitania.

Oddly, the only governor other than the typical Watt type that I've found pictures of online is the Proell, which is sort of an upside-down Watt governor. These pictures are of the earliest incarnation of the device, but they still clearly show the operating principles. The model employed on the Olympic-class ships was driven directly by a worm gear on the forward spindle of the turbine, and the fly weights were covered by a cylindrical housing with a semi-conical top. It can be made out in the "Engineering" elevation of the Olympic's engine rooms. (in profile, this thing reminds of the appearance of the carburetor and flame arrestor on the early Ford V-8's)

Scott Andrews
 

Similar threads