International Shipbuilding Progress

This article reviews the present situation in the field of turbo-blowers for 2-stroke diesel engines. The author first presents some theoretical considerations to outline the problems with which the designer of turbo-blowers for 2-stroke diesels is confronted mainly in view of the required pressure gradient between the turbine and compressor and attention to the surging limit. He then describes the two supercharging principles employed: constant pressure with scavenging pumps in series with the turbo-blower, and pulse operation with pumps in parallel, discussing their advantages and drawbacks, and finally deals with engine design, test and operating results.

This paper deals with the effect on resistance of hull roughnesses, including the effect of structural roughnesses on all-riveted and all-welded shells and of paint and other local roughnesses which frequently occur.

It is shown that the calculated reduction in resistance due to the elimination of structural roughnesses is in good agreement with conclusions based on ship trial data.

The paper also shows the marked variation in the effect of structural roughness on large ships compared with small ships and suggests that the modern flush-welded ship with a good paint finish on top of clean bare steel will have a resistance considerably above that of a perfectly smooth surface.

Significance of shipbuilding in relation to steelmaking.

The manufacturing process: Acid process. Basic process. Refining in the openhearth furnace. Teeming and the ingot stage. Treatment of the ingot.

Plate rolling: Two-high mill—roughing and finishing. Three-high plate mill. Four-high reversing plate mill. Continuous mills. Rolling-mill drives. Features of the rolling operation. Finishing operations. Mechanical testing.

Properties of ship plate: Chemical. Physical and metallurgical. Directional.

The growth of welding in shipbuilding—Brittle fracture—The development of improved steels.

The properties of water as a lubricant are discussed and the problems of practical hydrodynamic lubrication with water are shown to be capable of solution.

From this basis, two general marine bearing applications are considered, the first involving large relatively low-speed bearings, and the second smaller high-speed bearings. For bearings in the first category, such as stern-tube and A-bracket bearings, it is common practice to use water as the lubricant, but it is shown how such bearings may be considerably improved in the light of water-lubrication research, and full scale tests culminating in service in a warship are described.

For smaller high-speed bearings, in which at present the lubricant is almost universally oil, it is suggested that in many cases considerable advantage would be gained by using water-lubrication. To illustrate the feasibility of this, the development of water-lubricated journal and thrust bearings suitable for a main turbine is described, together with the operation of a turbine with such bearings, and the practical implications of this work are discussed.