Bessemer Oil Engine Fuel Nozzle.—Figure 324 is a cross section of the nozzle used with the Bessemer engine. In this design no nozzle tip is used. The oil, as it leaves the nozzle, is in the form of a cone. The lift of the valve A is so slight as to cause the cone of oil to be of infinitesimal thickness. In assem bling the nozzle, the valve spring should be compressed inch. This gives the spring enough tension to cause the valve to have a very snappy action. After repeated regrindings the valve may seat so deeply as -to cause a shoulder at the nozzle end. This shoulder prevents the oil from issuing in a cone and must be removed. To do this the nozzle should be ground on an emery wheel until the shoulder disappears.
Mietz and Weiss Oil Engine Fuel Nozzle.—This nozzle, a cross-section of which appears in Fig. 325, makes use of two check valves and a nozzle tip. The method of regrinding the valves is the same as used on any similar nozzle.
Care of Fuel Nozzles.—The successful operation of a low pressure oil engine depends, to a great extent, on the action of the fuel nozzle. The check valves must not leak and must close and open rapidly.
At least once every thirty days, if the engine is in constant service, the nozzle should be removed and cleaned. Kerosene or strong lye water is by far the best cleansing agent to use. The interior of the nozzle should be inspected and all coke or carbon deposits completely removed.
After cleaning the nozzle, it should be connected to the pump line, although not inserted into the cylinder, with the tip removed. Kerosene should be supplied to the pump, and a pint or so should be forced through the discharge line and the nozzle. This will cleanse the line and nozzle of any small particles of grit or dust. The tip should then be screwed into the nozzle.
To check the nozzle valve action, the pump should be given several vigorous strokes to remove all air. As soon as the pres sure builds up in the line, which is evidenced by the "pull" of the pump handle, the pump should be given a few short quick strokes. If the nozzle valve does not shut off the oil, or if the tip drips oil, it is proof that the valve is leaking.
In regrinding the valve, as already mentioned, a paste of emery flour and vaseline should be used. A sparing amount should be placed on the valve, spreading it over the entire valve seat. Turn the valve, while grinding, with the fingers only, or with a light screw-driver. To avoid forming grooves on the valve face, the valve should be lifted frequently and given a forward and back ward motion, never completely rotating it.
In operation, after replacing the nozzle, the engine occasionally refuses to fire. This, in most cases, is due to the fuel pump and nozzle being air-bound. To relieve this, the line should be dis connected at the nozzle and the pump worked by hand until a solid stream of oil appears. The nozzle should be filled with kero
sene, which should be poured in slowly to allow the air to be displaced.
As to the efficiency of the nozzle, much depends on its location in the cylinder or combustion-chamber walls. If the nozzle is in a vertical position, opening upward into the cylinder, prac tically no drops of oil will enter the cylinder after the valve cuts off. On the other hand, the oil remaining in the nozzle tip, above the valve, will tend to vaporize, and, if it is a heavy oil, it will leave a tarry residue which will choke up the tip. If the nozzle opens downward into the cylinder, it will clear itself of all excess oil, resulting in a fairly open nozzle tip. But this position allows the excess oil to drip into the cylinder. If the pump and nozzle valves leak, oil will drip during the entire stroke. When placed horizontally in the head or combustion-chamber walls, the nozzle seems to give the best results.
Water Injection.—Originally, water was injected into the cylinder for the purpose of preventing preignition, and it un doubtedly accomplishes this object. In those engines in which the fuel is injected early in the compression stroke, the use of water is absolutely imperative to keep the compression pressure below the preignition temperature. In the early days of low pressure engines, if the compression pressure rose above 60 pounds the engine would wreck itself if the supply of water was cut off.
With more modern designs of this engine the injection of fuel occurs much later; in some engines the injection is almost at dead-center. In these engines the elimination of preignition is but a- secondary result of the use of water. The principal use of water injection is the control of the temperature of the hot bulb or combustion chamber.
It is very apparent that with a given size bulb the total amount of heat that the bulb will absorb is dependent on the amount of heat it will radiate. If it receives more heat than it can give up to the cooling jacket and the outside air, then it will show an increase in temperature. The result is that on low loads, if the bulb is of a size suitable for full load, the temperature of the bulb becomes so low as to preclude successful ignition of each fuel charge. If the bulb be designed for half-load conditions, at full load the temperature of the bulb becomes so great as to cause preignition even though the fuel be injected as late as 20 degrees ahead of dead-center. The size of the bulb cannot profitably be altered at each load change, and water injection does serve to control the temperature of the bulb. By designing the bulb to be of ample size to vaporize the fuel at low loads the water can absorb the excess heat developed under full-load conditions.