The undisputed economy of the Diesel-type engine using heavy fuel oil is recognized, as no other power-generating unit of today shows better thermal efficiency. It is the result of the direct application of fuel in working cylinders. Transmission processes, such as the burning of fuel under a boiler to produce a working agent which must be carried to the prime mover, are less economical. The various factors which enter into a comparison between steam and heavy-oil installations are illustrated.
The subject is treated in a more or less elementary manner. The diagrams and sketches are intended to explain the working principles of such examples of two and four-cycle engines as are now in actual operation in cargo ships, these being of the single-acting type. Double-acting and opposed-piston-type engines have been built and are being tried out.
The working processes of two-cycle and four-cycle engines are illustrated and described in some detail, inclusive of critical comment. The working scheme of a four-cycle single-acting marine Diesel engine, shown diagrammatically, is followed through, covering the subjects of starting air, compression, fuel oil, lubricating oil, crankcase and fuel-valve design, valve gears and reversing, fuel pumps and Diesel-engine-driven auxiliaries on modern ships. A lengthy review of the development possibilities for engines of this type is then presented and a plea is made that the practical man cast his lot in with those who are trying to make our merchant marine permanent.