Valve Stem Stuffing-box.—The gland of the valve stem stuffing-box is rather weak, while the stuffing-box is very shallow.
The air will blow out along the stem, and in tightening the gland stud-nuts the ears of the gland will invariably bend. If the stuffing-box were deeper, enough packing could be inserted to withstand the air pressure. The only available remedy is the substitution of heavier glands, enabling more pressure to be exerted on the nuts. The packing used is vulcanbestos and wears away rapidly. In renewing the packing, the rings should be soaked in oil for at least twenty-four hours. When in use, the valve stem must be lubricated frequently to maintain the packing in a pliable condition. The fuel valve disk, which lies between the valve seat and the cylinder, carbonizes very heavily when a a low gravity fuel is burned. A lye solution will loosen this deposit,.
Type t Diesel.—The fuel valve of this Diesel, with its rocker mechanism, appears in Fig. 114, while Fig. 115 gives a view of the lower part of the same valve. The valve con sists of a cast-iron body with an extension which carries the spring, a needle valve and an atomization device. The body or cage rests in a bushing, which is pressed into the cylinder head, and is held by two studs. The needle valve a is enclosed along the lower part, which is in the cage, by a bushing or barrel b.
This bushing rests, at its base, on the atomizer cone and is prevented from lifting by a coil spring at the top.
As is seen in Fig. 115 there is a space, between this bushing and the cage wall, which serves as the air and fuel cavity. The fuel charge flows down the passage A and enters the fuel cavity above the atomizer disks: The disks are several plates containing small perforations and are so placed as to stagger these holes.
The oil, by its own weight, is forced to pass through these openings and fills the intricacies between the plates as well as the space around the needle valve seat. The air enters the cavity d above the oil level. When the needle valve is opened by the valve rocker, the air, which is at a pressure much higher than that existing in the engine cylinder, forces the oil charge into the combustion space. The oil, as it is broken up, passes from disk to disk, and is mixed with the air which is•flowing toward the cylinder. The emulsion is further increased as the air and oil issues through the single small opening in the atomizer tip f. This continues as
long as the needle valve is open; this valve is closed at the proper time by the fuel cam, and the small amount of fuel still left in the atomizer flows down around the needle valve seat. This insures a small charge of oil which will enter the cylinder at the next valve opening ahead of the air and produce ignition. With the usual fuel oil the fuel charge is able to pass through the disks under the influence of its own weight. When the valve opens, the oil is forced into the cylinder in front of the air. Since this oil is fairly light, it ignites even though poorly broken up. A heavy oil behaves quite differently. Its viscosity is such that the fuel does not readily flow through the disks but rests above them. The air must force the oil through the atomizer and, in so doing, thoroughly nebulize the charge. This type, then, has the advantage of offering a mixing and atomizing effect in inverse ratio to the gravity of the fuel; the actual degree of combustion in the cylinder is fairly constant, regardless of the nature of the oil.
Adjustments—Fuel Passage.—The fuel passage in the body of the valve cage is equipped with an aluminum rod which stands vertically; the rod moves with the vibration of the engine, thereby keeping the fuel line free from stoppage due to dirty or thick oil. Even with this precaution, the fuel line does collect dirt and should be flushed out with kerosene on the occasion of removal of the valve and cage.
• Nozzle Tip and Disks.—The fuel cage tip has a single central perforation which gradually fills up with tarry deposits, as do also the atomizer rings or disks. These can be cleaned with kerosene or lye water. • Needle Valve.—The needle valve is of steel and will corrode when the fuel oil contains any acid or sulphur. If the cor rosion is slight, the valve should be polished with emery paste and, if possible, burnished with a cloth buffing wheel. The buffing of the stem seems to retard the rate of corrosion. The valve seat is at an angle of 30 degrees with the axis of the needle valve. This angle, which gives an angle of 60 degrees to the valve end, is such that there is a wedging action each time the valve seats. This serves to effectually seal the valve but causes scores on the bearing surface in event any grit has settled on the valve.