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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