FUEL NOZZLES. WATER INJECTION Fuel fuel nozzles used on low-compression en gines show much similarity of design. Unlike the Diesel nozzle, there is but little attempt to thoroughly atomize the fuel charge as it leaves the nozzle tip. The chief use, apparently, for the nozzle is its service as a check valve to cut off the fuel supply as soon as the pump ceases to inject the charge. Since all low pressure engines actually vaporize the fuel before it is consumed, it is not absolutely necessary that the oil be atomized, but there is no doubt that the vaporization and combustion are more or less dependent on the degree of atomization.
In the nozzle, as in the fuel pump, a quick-closing and abso lutely tight valve is necessary. Many of the poor economy records of this type of oil engine are due to the inefficient nozzle valves.
Closing, as it does, during an infi nitesimal fraction of a second, it requires a tight valve to prevent some drops of oil from leaking past the seat.
Little Giant Oil Engine Nozzle.— Figure 319 is a cross-section of the nozzle used by the Chicago Pneumatic Tool Co. In this nozzle a single ball valve, spring-loaded, serves as the check and assists in giving a snappy cut-off to the fuel charge at the moment the pump reverses its stroke. The oil, in issuing around the ball valve, enters the nozzle-tip passage through the small opening in the spring guard. No effort is made to secure a breaking up of the fuel in the nozzle, and consequently the charge strikes the hot plate on the piston in a fairly solid stream.
A ball valve, after the seat is but slightly cut, will leak more rapidly than a poppet valve. With this fact in mind the engineer should frequently check the valve's condition. To do this, the nozzle can be unscrewed from the head. It should then be screwed onto the oil line and the pump given a few sharp strokes.
If the valve leaks, the oil leaves the nozzle without any decided pressure behind it, and the cut-off of the pump is not evidenced by an instantaneous cessation of the oil flow. It is necessary
that the nozzle be held horizontal to enable the ball valve to rest on its seat.
Muncie Oil Engine Fuel nozzle, Fig. 320, also makes use of a ball valve. The ball in this instance is provided with a spring-loaded cage. The nozzle is screwed into the top of the cylinder-head casting in a vertical position. In operation, the fuel pump injects a charge of oil into the nozzle. The oil pressure forces the ball B downward against the resistance of the spring-loaded cage C. The oil flows around the ball and then through the side ports into the cage which has a central cavity D. The oil, as it leaves the cage, is forced out through the small nozzle opening. This opening is approximately inch in di ameter. As soon as the pump reverses its stroke, the spring snaps the ball against its seat. While the entire nozzle is filled with oil during the period of combustion in the cylinder, there is but a small amount below the ball valve. This small quantity usually drips out into the cylinder.
When the oil used is of an asphaltum base, the spring and cage are prone to carbonize, destroying their effectiveness. When the cage is free and in proper working condition, it emits a sharp click at each pump injection. This "clicking" can be heard by placing the ear against the nozzle's outer end. If no rhythmic click is heard, the nozzle should be taken off and the carbon deposits removed by soaking in strong lye. The nozzle tip opening often cakes up. This can be removed with a sharpened darning needle. Care should be exercised that the opening is not enlarged during the process of cleaning.
If the ball valve leaks, a small hardwood stick should be placed squarely against the ball and given a sharp blow with a light hammer. After long use, the cage wears until its clearance is more than the M2 inch which is standard. In such event a thin sheet-steel washer can be cut and placed between the cage and nozzle tips.