Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

The De La Vergne Oil Engine (Type HA)

In the small four stroke cycle De La Vergne Oil Engine, the fuel is injected into a heated vaporizer during the suction stroke in such a way that the vapor and intake air do not form a mixture in the cylinder proper. On the return stroke of the piston, the compression of the pure air takes place which forces the air into the vaporizer and into intimate contact with the oil vapor. This forms an explosive mixture which ignites and forces the piston outwardly on the working stroke. The release and scavenging are performed in a similar manner to that of a four stroke cycle gas engine. Both the inlet and exhaust valves are of the mechanically operated poppet type, and as both the inlet and exhaust gases pass through the same passage, the entering air is heated to a comparatively high temperature.

The injection pump receives the fuel from a constant level stand pipe or tank, located near the engine and injects the fuel into the vaporizer through a spray nozzle. The vaporizer is a bulb shaped vessel that is connected with the cylinder through a short post and really forms a part of the combustion chamber. Since no water jacket surrounds the vaporizer, it remains at a high temperature and vaporizes the oil at the instant of its injection. Because of the residual gases remaining in the chamber, ignition does not occur until air is forced through the passage by the compression. The air inlet valve and the fuel injection valve are opened at the same instant by a cam lever that also operates the pump.

On the compression stroke, the air which is at a pressure of approximately 75 pounds per square inch enters the vaporizer, and ignition occurs, partly because of the increased heat due to the compression and partly because of the supply of additional oxygen. Internal ribs provided in the vaporizer greatly increase the heat radiating surface and add to the thoroughness with which the atomized oil is vaporized. Since no mixture of air and fuel takes place in the cylinder proper, sudden changes in the load do not affect the ignition of the charge as the heated surfaces are surrounded with comparatively rich gas under all conditions.

Before the engine is started, the vaporizing chamber is heated to a dull red heat by means of a blast torch in order to vaporize the oil for the first stroke. As soon as the engine is running, the lamp is cut out and the temperature is maintained by the heat of the successive explosions. The combustion attained by this method is very complete even with the heaviest fuels, and whatever carbon deposit is formed occurs in the vaporizer from which it is easily removed. The contracted opening of the vaporizer passage effectually prevents the solid matter from working in the bore or valves.

A Porter-type fly ball governor maintains a constant speed at varying loads by regulating the quantity of fuel supply to the vaporizer, the air intake remaining constant. A by-pass valve, controlled by the governor divides the oil supplied by the pump, into two branches, one of which leads to the spray nozzle and the other to the supply tank. In the case where all of the oil is not supplied to the vaporizer because of a light load, the by-pass valve will return the surplus to the tank, thus maintaining a constant pressure at the spray nozzle.

When operating under ordinary loads, the governor opens only the small inside valve which regulates the amount of oil injected into the vaporizer. But should the engine speed up, due to a sudden change in the load, the governor will not only open the small valve but also the large concentric valve, in which case all of the oil will return to the tank. The makers guarantee the following speed variation limits under the different loads.

Ordinary Variation	2½	per cent.
Full load to one-quarter load	4	per cent.
Full load to no load	5	per cent.