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
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).
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.