SS awe ye 
THE DESIGN OF AN OIL ENGINE. 29 
He went so far as to propose the use of coal in a pulverized form in his engine. 
While the use of coal in the engine is of very doubtful value, the use of all grades 
of fuel oil is unquestionably practical. How to utilize these low-grade fuels is very 
important. 
We buy fuel by bulk, and it is practically true that all fuel oils have the same 
calorific value. The point to be considered is that when a heavy fuel is bought by 
bulk, although the calorific value per pound is somewhat less than for a high-grade 
fuel, the calorific value per gallon is greater. Since we buy the fuel by the gallon 
this is what interests us. 
Again, in order to protect the development of the engine against being checked 
by the rising price of the fuel oil, it is very essential to be able to use the same fuels 
as are used under the steam boilers. If this be done, since the oil engine has an 
efficiency of not far from three times that of the steam engine, the steam engine 
can be driven back to the use of coal before the oil engine can be seriously affected 
by the rise in the price of fuel. 
Having shown the extreme desirability of the use of this low-grade fuel, next 
in order is the study of means for using it with good results. There seems to be one 
means which has already been proven in the steam plants, that is, to heat the slow- 
flowing fuels before feeding to the fuel pumps and fuel valves, and to do away with 
the jackets on the fuel valves while changing the design of the valves so that this 
can be done without serious trouble. As far as the operation of the engine is con- 
cerned, the heavy fuel, when thus treated, is in every way the equal of the gas oil. 
For this reason it becomes of the utmost importance that the treatment of the fuel, 
preparatory to spraying, be studied with the utmost care. 
For all practical purposes it can be stated that the Baume of asphaltum base 
- fuels will increase one degree for each increase of 15° F. in temperature. With 
this change in Baume there is also a change in viscosity. This change is needed to 
make extreme low grades of fuel oil available. It will not be sufficient to simply 
heat the fuel oil; it must be kept hot till after the oil spray is formed. This means 
that the water jacket must be omitted from the design of the fuel valve, a step which 
has already been adopted by some engine builders. The only excuse for a water 
jacket on the fuel valve is to prevent combustion in the fuel valve. This can be 
prevented by a change in the design of the fuel valve, and better results will be 
had from this new type of valve. 
In suggesting anything new in an engineering line the reason must be looked 
for to explain why this has not been done before. It is not safe to say that a rea- 
son does exist. Only too often the new idea has never been tried on account of a 
lack of inventive or imaginative ability rather than on account of too great an un- 
derstanding of the obstacles confronting the designer. In this case there seems to 
be no obstacle in the way of building a universal oil engine. By this term is meant 
an engine which will use all grades of fuel without changing any of the parts of the 
engine. For instance, it might be possible to design an engine with several inter- 
changeable fuel valves, so that as the type of fuel was changed a suitable type of 
