SECTIONAL TRANSACTIONS.— G. 359 



The advantages of heavy-oil engines over petrol engines include : improved fuel 

 consumption, especially at low loads, as determined by weight, and still more by 

 volume ; use of a cheaper fuel — under present market conditions ; relative absence 

 of fire risk ; greatly reduced fouling of the lubricating oil. Against these are some- 

 times urged the disadvantages of higher maximum pressures and lower mean effective 

 pressures in the cylinder. 



Development has proceeded along three main lines which are determined by the 

 methods in which the fuel is brought into contact with the air supplied for combustion. 

 These are (a) direct injection of the fuel into a simple combustion chamber ; (b) injec- 

 tion of the fuel into an ante-chamber in which combustion begins, the consequent rise 

 of pressure there causing the fuel to be forced into the main combustion chamber, 

 where combustion is completed ; (c) compression of the air into a cavity in the com- 

 bustion chamber, either in the piston or cylinder head, injection of the fuel being 

 arranged to take place into the air, escaping from the cavity at high velocity at the 

 beginning of the expansion stroke. 



These three main methods are discussed in detail and comparisons are made 

 between them from the points of view of performance, mechanism of combustion, and 

 the necessary accessories. 



Other suggested types of engines using heavy oils are also described. 



In conclusion, a general comparison of existing engines is made. 



Discussion. 



Afternoon. 



Visit to Portishead Power Station. Tea by invitation of Bristol 

 Corporation Electricity Department. 



Visit to Avonmouth Docks. 



Friday, September 5. 



Presidential Address by Sir Ernest W. Moir, Bt., on The Interde- 

 pendence of Science and Engineering, with some examples. (See p. 119.) 



Discussion (Sections G, I) on Air Pressure Variations encotintered in 

 Engineering Works and their Physiological Effects. (Sir Ernest 

 Moir, Bt., Prof. Sir Leonard Hill, F.R.S., Capt. G. C. C. Damant, 

 C.B.E., Mr. R. H. Davis). 



Sir Ernest Moir, Bt. — The subject of the discussion is of verj- great importance 

 in the furthering of engineering and allied enterprises. There is a need for the full 

 light of science to be brought to bear on the use of air, reduced in volume by mechanical 

 means and so increased in pressure, in connection with the construction of works of 

 utility. 



The effects of compressed air on man working either in a diving dress or at more 

 or less air-tight shafts, tunnels, foundations, caissons, etc., have occupied the thoughts 

 of physicists, engineers and medical scientific research workers for many j-ears. 



The object of this discussion is to get as much useful knowledge as possible from 

 those having experience in the handling of such pressures, the control of staffs and 

 workers who labour under its influence, and the prevention of injury to them. 

 Furthermore, to gain knowledge of the best way to use even higher densities of air 

 with safety and thus permit operations that in the past would have meant permanent 

 injurj' or death to those who attempted to use it. 



In the presidential address, references are made to some of his experiences, and 

 the introduction of recompression in a medical air lock, and further light will be thrown 

 on the subject by those taking part in the discussion, especially by Sir Leonard Hill 

 who has already made a great study of the problem, by Captain Damant whose 

 achievement in recovering gold from the Laurentic is well known, and by Mr. R. H. 

 Davis who, with his firm, has developed a special diving apparatus for making descents 

 greater than have ever before been made. 



