80 



SOME COMPARISONS RELATING TO 



turbogenerator plant for naval work if steam is to be used as a prime mover. My change 

 comes simply and solely from a consideration of the curves of efficiency shown in Fig. 1 of 

 my plate (Plate 40). It is in spite of the erroneous claims which have been made for this 

 type of plant. This figure shows, not that the turbo-generator plant is superior at all condi- 

 tions shown, but it does show a gain in efficiency at cruising speeds which is the most used 

 condition in the Navy. To be consistent with my previous statement that such facts should 

 not be taken without a reason, some explanation for this condition should be found. I have 

 satisfied myself that a perfectly good reason exists why the turbo-generator plant should be 

 only equal or slightly inferior to the reciprocating plant at full load and superior to it at 

 cruising speeds. 



My entrance into this discussion last year was to combat some of the extravagant 

 claims made for this type of prime mover. Had these claims been correct there would 

 exist but little incentive for me with others to work in developing the oil engine for this 

 service. However, this argument proves conclusively that the efficiency of this plant is at 

 its best not over 1 1 per cent. I have shown how theory is better than practice when prac- 

 tice is carelessly used. Last year no objections could be raised to my statements that it 

 was possible to build an oil engine of from 25 to 36 per cent efficiency. 



Under these conditions I feel that while the supremacy of the turbo-generator plant, for 

 naval work alone, is fairly well demonstrated as far as the conservation of fuel is concerned, 

 the oil engine by reason of its much greater efficiency and small amount of space occupied 

 is unquestionably the superior of all the known forms of prime mover for maritime uses. 



Mr. John Reid, Member: — I would like to say a word on this subject from the 

 standpoint of the naval architect. You get certain views about electrical propulsion from 

 marine engineers, for and against, but the naval architect must look at this thing from an 

 entirely separate standpoint. I will show you by a diagram what I mean. 



fostjiori OF- £;frlosion 



I think you are aware that there is a good deal of surprise in the minds of naval archi- 

 tects as to just why certain vessels which have recently been lost through mining and sub- 

 marine activities actually went down, referring to both warships and merchant vessels. 

 One large warship which was recently lost was hit in the port engine-room. I will make a 

 small diagram of what I mean. Here is the engine-room of that ship, we will say (indicat- 

 ing on the diagram on blackboard), and there are two engine-rooms for the four sets of 

 turbine engines. The ship was hit here (indicating) by a very small bomb or mine, and this 

 bulkhead (indicating) was not damaged at all, but the water got through from one engine- 

 room to the other, and as she gradually listed over she had to be abandoned and went down. 

 Those of us who have been familiar with merchant practice are not very much surprised 



