THE DESIGN OF AN OIL ENGINE. 31 
fuel pump so that the fuel valve will open, starting a stream of injection air into the 
cylinder, and at the same time the discharge from the fuel pump will take place, 
delivering the fuel charge directly into the stream of moving air where it will be 
broken up and delivered into the cylinder in the form of a suitable spray. By this 
method one of the obstacles to heavy fuel will be overcome. From the time the 
pump begins to deliver its charge the fuel will not be allowed to come to rest. In 
this way the fuel valve can be simplified in its design and the question of a deli- 
cate proportioning of parts to suit a special type of fuel will be done away with. 
It will be possible with a little experience to vary the pressure of the injection air, 
giving an additional saving. This, however, will be a matter of adjustment pos- 
sible while the engine is in operation. Even if this be ignored, the gain through the 
use of heavy fuel, not practical in the present types of fuel-feeding arrangements, 
will be made without any counteracting loss. The fuel valve of this arrangement 
consists simply of two passages, each controlled by a separate needle valve. These 
valves are worked from one tappet rod and the air valve must be opened first, with 
the opening of the fuel valve being timed to the delivery of the fuel by the pump. 
In this way a stream of air will be started and the oil delivered into this air, and 
then the air will continue to flow for a short time after the delivery of the fuel in 
order to clean the passage to the cylinder so that the valve may not be clogged. 
The fourth figure is an enlargement of the fuel and air delivery events. The 
duration of the opening of the valves and of the pump strokes can be controlled as 
well as the timing of those events. At first thought this seems to be quite a compli- 
cation, but on closer obseryation this complication is shown to be nothing but what 
exists in every automobile engine. Certainly, if it is advisable to vary the timing 
of the spark on an automobile engine for the sake of speed control, it is not out of 
place to contemplate a similar modification in an expensive plant where the effi- 
ciency gain will be a great factor. Again we have several elements here. It would 
be impractical to have the elements all under individual control. It will be possible, 
however, to have a connection between the fuel-pump control and the fuel-valve con- 
trol so that one lever will regulate all. This would be similar in idea to the present 
method of changing the cut-off on all cylinders of a compound steam engine from 
one lever, and at the same time with a provision for varying the cut-off of the sep- 
arate cylinders at will. 
STARTING. 
This is the first thing to be done with the engine and has been the last to re- 
ceive consideration. The reason is that the time under the starting cycle is very 
short, and the matter of efficiency is not worth considering. By efficiency is meant 
the thermal efficiency. It is a matter of efficiency whether the engine will start or 
not. It becomes a matter of efficiency if it be shown how the engine can be run 
for an appreciable time on the energy which can be stored in a compact form avail- 
able for instantaneous use. This is a matter of practical utility rather than of ther- 
mal efficiency. That the matter of thermal efficiency does come into this considera- 
tion is only incidental. 
