The parts enumerated above are the essential parts of the Diesel engine. However the arrangements may differ, it is necessary that the unit include an air compressor, fuel pump, governor, camshaft and injection or fuel valve in addition to those parts generally found on an internal combustion engine.
Figure 6 represents the working diagram of a two-stroke-cycle. In Fig. 6b the air charge is compressed; in Fig. 6c the fuel is injected and the piston forced downward on the working stroke; in d the piston uncovers passages or ports in the side of the cylinder through which the exhaust gases pass. As the piston moves downward to the point A, a valve in the cylinder head opens, and a charge of pure air which has been compressed to about 10 lbs. blows into the cylinder, clearing it of all exhaust gases. At B, or before this point, the scavenging valve closes, and, as the piston moves upward, it seals the exhaust ports at the point B. Continued upward motion compresses the air charge until upper dead-center is reached whereupon the cycle is repeated.
American Diesel Engine Company.—This company was the pioneer Diesel engine company in the United States. At the present time there are many installations of the American Diesels which have been in operation for ten to fifteen years, though they have largely been replaced by units of modern design. For this reason the engine is mainly of historical interest although there is more demand for experts to adjust and repair these engines than any other. This, of course, is because the engines have been in service for such lengths of time that extensive overhauls and rebuildings are necessary.
Figure 7 is the cross-section of the American engine. Even to the inexperienced it is evident that the builders largely followed accepted gas engine designs in the general construction of this unit. The frame was of the box type and was reinforced by tension rods to absorb the working stress. The cylinders, of which there were three per engine, were cast integral with the jacket walls. The valves were located at the side of the cylinders quite like the gas engine practice of ten years ago. The box frame was entirely enclosed, though provided with side doors, and splash lubrication was used. The camshaft was carried
inside of the frame in bushed bearings bolted to the interior of the frame; the gear reduction was 2 to 1, with an idler pinion between the camshaft and the crankshaft gears. The various parts will be discussed in succeeding chapters as will also the parts of other engines.
The engine, when first introduced, was of a type unknown to the American engineer and, like all new machines, suffered at the hands of ignorant and unskilled laborers. Probably no prime mover ever experienced the manhandling accorded this oil engine. Scores of cylinder-head stud bolts were twisted off under the efforts of a brawny laborer using a 5-foot pipe wrench. As faulty as the engine was, it is highly probable that it would have been fairly successful under the attention of more skilled operators. It, however, served the useful purpose of giving many Diesel engineers experience. Later-day manufacturers should, for this reason, have a grateful feeling toward this pioneer.
Bros. Diesel company represents a reorganization of the American Diesel Engine Co. In the design of the Type B stationary engine the experience of their Swiss associates, Sulzer Bros., has been drawn upon. The engine, a view of which appears in Fig. 8, has four working cylinders, while the air compressor is mounted on the engine frame and has much the appearance of a fifth cylinder. The frame is of two-piece construction, the base carrying the shaft bearings. The upper portion of the frame rests on the base and is tied to it both by base stud-bolts and tension bolts or tie rods.
The camshaft is mounted close to the top of the cylinder and is driven by a vertical drive shaft, which also carries the governor. This is shown in Fig. 8. The camshaft is entirely enclosed, the cams working in an oil bath. Doors provide access to the various parts. The valve mechanism has incorporated with it a servomotor, which controls the injection point and the air injection pressure. The cam housing also includes the support for the fuel pumps which are driven from off the vertical cam drive shaft.