HEAVY-OIL ENGINES FOR MARINE PROPULSION. 
By G. C. Davison, Eso., MEMBER. 
{Read at the eighteenth general meeting of the Society of Naval Architects and Marine Engineers, held in 
New York, November 16 and 17, 1911.] 
The technical press of the world for the past two or three years has 
contained much on this subject, and at the present time general interest is 
still on the increase. This may be accounted for by the fact that we have 
a large cheap supply of liquid fuel available, and that its use for the propul- 
sion of vessels is attended by wonderful military and commercial possibilities. 
Therefore, the subject is one which is worthy of the attention of all naval 
architects and marine engineers. 
Within the past few years there have been various types of engines 
developed for the purpose of using crude oil, or fuel oil. These engines may 
be divided into two general classes—those working on the constant volume, 
or Otto cycle, and those working on the constant pressure, or Diesel cycle. 
The Otto cycle is too well known to require a description here, since it is 
the cycle used in all gasoline and gas engines. Its use is practically limited 
to volatile fuels and gases. Kerosene and the heavy hydrocarbons have 
been used to a limited extent in engines of the Otto principle by vaporizing 
the fuel oil by means of heat. But up to the present, little practical success 
has rewarded the efforts made in this line. 
The Diesel engine, on the other hand, has been a success from the first 
as a heavy-oil engine. Its use was at first limited to stationary engines. 
Success has been so marked that the increase in the output of these engines 
has been remarkable since its first development. Only in the last few years 
has it been considered as a marine engine, but it has shown itself so well 
adapted to marine propulsion that its use afloat has rapidly grown so that 
at the present time it is estimated that over 250 sea-going vessels of from 
a few hundred to several thousand tons each, are now equipped, or being 
equipped, with these engines. 
The Diesel cycle may be briefly described as follows: 
1. On the admission stroke pure air is drawn into the cylinder. 
2. On the compression stroke, the pure air is compressed to a pressure 
of about 500 pounds per square inch. Due to such a high degree of com- 
pression the air is heated to about 1,000° F. 
