PROGRESS IN TURBINE SHIP PROPULSION. 79 



Mr. Fr.\ncis Hodgkinson : — No, thank you, Mr. President, except to thank the Society 

 for their kind reception of this paper. ^ 



Rear Admiral Washington L. Capps, Vice-President: — I think it should be under- 

 stood that written communications will be in order later on, because some of the papers this 

 year were subject to the disadvantage of not having been printed until the very last mo- 

 ment. The printer came to my office in Washington the other day and told me that, al- 

 though all the papers were printed, he could not get them shipped by express, as the express 

 company rec|uired an order from the War Industries Board. That indicates the added diffi- 

 culty this year. These papers, it would seem, therefore, should be subject to written discus- 

 sion after the meeting. 



The President : — Written communications will, of course, be welcome on all the papers 

 presented at this meeting and may be sent in after the meeting. Mr. Emmet, would you like 

 to say something on the subject? 



Mr. William L. R. Emmet, Member of Council: — There are one or two things in the 

 paper that I wish to comment on. There is one interesting subject which suggests itself be- 

 cause of Mr. Hodgkinson's paper, and that is the question of superheat. I am, making some 

 experiments now which I think ought to be interesting, and if I get successftd and useful 

 results, I will probably report them later to this Society. 



The idea is this — that in geared ship installations the steam enters the turbine in one 

 direction, and when the ship reverses it has to go through a turbine which is operated in the 

 opposite direction. We may imagine a ship is backing and the head turbine is going at a 

 high speed in a certain direction. Steam is admitted to it to go in the other direction, and 

 the turbine may continue to turn in the wrong direction for the steam going through it. 

 Theory would indicate the production of very high temperatures under such conditions, and 

 certain evidences which have developed have shown the existence of such high temperatures, 

 which is an argument against the use of superheat in geared turbines. I think many of the 

 troubles with modern turbines generally have been incident to the act of reversing. This 

 revulsion of temperature, which occurs on highly developed surfaces, tends to produce strains 

 in the various parts of turbines, tends to enlarge the engagement of the wheels on shaft 

 and to introduce strains. 



In the experiment referred to I am using a marine turbine arranged so that it can be 

 run in two directions, the steam being applied in either direction. 



I am putting pyrometers in the steam passages which will record instantly the tempera- 

 tures produced in the act of reversing, and other conditions. 



This matter is important, becaiise it has a bearing on the relation of electric drive to gear 

 drive, that is, in the electric drive we have one direction of rotation and can use superheat 

 with impunity, whereas in the gear drive the use of superheat may not be so useful. The 

 ship Mjolner, a ship of only 1,000 horse-power, used 300 degrees of superheat, and showed 

 for a succession of voyages a performance of 38 per cent less fuel consumption than engine- 

 driven sister ships running in the same service. That is mainly due to the use of superheat, 

 and if such improvement is possible, we simply must have it. 



There is another point I want to mention in connection with this paper. I am not going 

 to enter into a discussion of the very difficult and complicated subject of different types of 



