The Burmeister and Wain Two-Stroke Cycle Engine

The INSTITUTE of MARINE ENGINEERS

Founded 1889. Incorporated by Royal Charter, 1933.

The Burmeister and Wain Two-Stroke Cycle Engine

SESSION 1936 Vol. XLVIII. Part 10.

President: The Hon. Alexander Shaw

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The Burmeister and Wain Two-Stroke Cycle Engine.

READ

By Dr. H. H. BLACHE. On Tuesday, October 20th, 1936, at 6 p.m.

Chairman: Mr. R . Rainie , M.C. (Vice-Chairman of Council).

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Synopsis.

MARINE engine construction especially with regard to the evolution of new types of main engines, is referred to as probably being subjected to more difficult conditions than any other form of machinery construction. Tribute is paid to those shipowners whose progressive policy leads them to adopt new types of propelling machinery.

The details of the B. & IV. two-stroke double-acting Diesel engine are described. Present designs make fullest use of experience gained from running and building of many engines during the six years which have elapsed since the “Amerika”, which was the first vessel fitted with this type of engine, was put into sendee.

The various parts of the engine are described seriatim, including cylinder covers and liners, main tie bolts, pistons, piston rings, piston rod stuffing box, eccentric driving gear for exhaust piston valves, governor, gear for reversing and manoeuvring, also that for fuel pumps, scavenge blowers, cooling of liner and cover, etc. Then the singleacting, two-stroke, trunk piston engine is similarly described. The latest methods of making cast steel crank webs receive brief reference, and the thrust blocks of the B. & W. type receive special mention, as do lubrication problems generally.

Comparisons are made between the B. & W. four-stroke cycle engine and the B. & W. two-stroke engine. The characteristics of the engine as regards reliability receive special mention, and a few general remarks are made regarding marine Diesel engines. The paper concludes with a brief reference to the present trend of steam and Diesel machinery.

Members of this Institute will surely agree with the author that the problem presented by the designing of new types of engines for marine work is far from easy. In addition, shipowners generally order their new tonnage for delivery in the shortest possible time. The machinery must be ready for installation immediately the vessel has taken the water, and no excuses are accepted even if, for some unforeseen reason, it is desirable to prolong the test bed trials. A short basin trial—usually disturbed by frequent stoppages due to ships passing —followed by a one-day trial trip is, as a rule, all the time which is at the disposal of the technical experts. Then, without delay, the vessel has to go on her maiden voyage, at full power, in order not to lose a charter or keep enlisted passengers waiting.

Otherwise the former might result in a heavy monetary loss to the owner, and the latter have its sequel in articles in the daily press, unfavourable both for owner and engine builder. Marine engineers employed on technical developments are the first to pay tribute to the enterprise and progressive policy which characterise those leaders of shipping companies who have not hesitated to adopt new types of engine, as these gradually were introduced during the last quarter of a century. Amongst these may be named the following:—

(1)—Twin-screw single-acting four-stroke crosshead type for m.v. “ Selandia ” (the first ship fitted with B. & W. Diesel engines).

(2)—Twin-screw four-stroke trunk-piston type for passenger vessels.

(3)—Single-screw four-cycle long-stroke crosshead types and twin-screw trunk engines for tramps.

(4)—Twin-screw four-stroke double-acting crosshead types for passenger liners aggregating from 10,000 to 20,000 b.h.p.

(5)—Single- and twin-screw double-acting two-stroke crosshead types for combined cargo and passenger liners, aggregating from 3,000 to 30,000 b.h.p.

(6)—Single- and twin-screw single-acting two-stroke trunk-piston types for passenger vessels and fruit carriers, aggregating from 1,800 to 8,000 b.h.p.

Although it is undoubtedly of great advantage to carry out exhaustive trials on the test bed should the time be available, the conditions under which a

marine plant works on board ship are of such a special nature that prolonged running experience at sea is necessary to ensure the attainment of the desired high standard.

Sea-going engineers, together with the technical staffs of engine works, are of great assistance to the designer of new engine types. These men, from youth, are trained to carry out engine overhauling under difficult conditions both at sea and in harbour, to enable scheduled sailings to be maintained.

Circumstances corresponding to these, it is safe to state, are not to be found in any other branch of engineering.

In touching upon the factors which have their effect upon the design of marine engines, the varying conditions in shipping and their consequent influence upon the shipbuilding industry may be mentioned. In periods when trade is brisk the demands of shipowners are probably three times the normal. These demands react upon shipbuilders and marine engineers who are bound to keep pace. The additional work thus requires increases of staff, and often also extensions to shops and equipment involving large financial obligations. In corresponding periods of slackness, shipowners bury their building programmes, although they manage to keep their ships in service, or at the most lay-up a few of them. Thus the variations in the conditions for shipping are not so great as for shipbuilding, where the industry is liable to periods of complete idleness, which may occur with suddenness and at an unpredictable point in time.

Shipyards, in turn, are better able to cope with these variations than marine engine works, as the capital invested in shipyards is comparatively small in relation to the production, large parts of a ship being purchased either ready for use or in a semifinished state. Marine engine works, on the other hand, and in particular those building Diesel engines, must by reason of the special materials used, be capable of manufacturing the complete machinery. This necessarily implies costly shops. In lean times it therefore becomes exceedingly difficult suddenly to reduce general costs. A contributory factor in this is the utmost importance of retaining the technical staff during such periods of idleness. A sound technical staff, gathered together and trained during many years, can hardly be overrated. It is at least as important a factor for meeting demands of production as are the site, buildings, machine tools, cranes and all other equipment in which the proprietors’ capital is invested.

These, in fact, are valueless without a proper technical staff. The general public, the banks, financiers and others are very liable to overlook these principles, so simple and obvious to engineers. Shipyards and marine engine works being an absolute necessity for the maintenance of shipping —and through it of many other industries and trades—ought to receive proper support during periods of critical depression, coming, as these often do, suddenly and unforeseen. In these respects shipbuilding and marine engineering" are without a parallel in other branches of industry.

The characteristic features of the Burmeister & Wain four-stroke single- and double-acting Diesel engines were described in the author’s paper read before the Institution of Engineers and Shipbuilders in Scotland in April, 1925. The later developments in the design of the four-stroke engine, including the B. & W. topping-up supercharge system, were described in the author’s paper read before the Institution of Naval Architects in July, 1931. (This paper also referred to the B. & W. two-stroke single- and double-acting Diesel engines.)

Since then no advances of any importance have been made in the design of the four-stroke Diesel engine. On the other hand, a great deal of experience has been gained during this period with the B. & W. two-stroke engine, resulting in important improvements and in the simplification of the design, all of which are incorporated in current contracts.

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