Date post: | 05-Apr-2018 |
Category: |
Documents |
Upload: | naveen-kumar |
View: | 218 times |
Download: | 0 times |
of 15
8/2/2019 02 Medium Speed Diesel Engine
1/15
Medium Speed Diesel Engines
Defined as those having rated speeds
within the range of
300 to 1000 rev / min.
In recent years the geared multiple engine marine mainpropulsion plants have been used in certain types of ships. There
are a number,of advantages which have prompted development
of these compact power units. The developments that have taken
place for these new, higher output four stroke, main propulsiongeared units are towards high piston and engine speed, higher
mean effective pressure with high degree of turbo charging and
vee arrangement of cylinders.
8/2/2019 02 Medium Speed Diesel Engine
2/15
According to Speed.
Slow Speed Engines: 100 to 150 r.p.m.
Medium Speed Engines: 300 to 1000 r.p.m.
High Speed Engines: More than 1000 r.p.m.
8/2/2019 02 Medium Speed Diesel Engine
3/15
8/2/2019 02 Medium Speed Diesel Engine
4/15
In Diesel engines also, there is tough
competition between medium and slow speed
engines.
The worse quality of fuels available and
increase in the cost of oil has led to renewed
interest in coal-fired ships. Keeping in viewthe limited world reserves of oil, coal fired
ships seem to provide a good alternative in
2000s but at present the position of Dieselengines remains unchallenged.
8/2/2019 02 Medium Speed Diesel Engine
5/15
Compact engine room
8/2/2019 02 Medium Speed Diesel Engine
6/15
Medium speed engine shaft drive
8/2/2019 02 Medium Speed Diesel Engine
7/15
Vee type engine
8/2/2019 02 Medium Speed Diesel Engine
8/15
Medium speed engine crankshaft
8/2/2019 02 Medium Speed Diesel Engine
9/15
8/2/2019 02 Medium Speed Diesel Engine
10/15
8/2/2019 02 Medium Speed Diesel Engine
11/15
8/2/2019 02 Medium Speed Diesel Engine
12/15
8/2/2019 02 Medium Speed Diesel Engine
13/15
Friction clutches A and
B are pnuematically
controlled from some
remote positions. Gears
1,2,3 and 4 would haveto be the same size if the
gear were to be single
reduction.
8/2/2019 02 Medium Speed Diesel Engine
14/15
Advantages of medium speed engines:
(a) Low weight of engine and reduced space
requirement - In the present state of technology,
with turbo - supercharging there is about 30%,
saving in space of engine room and 300% saving in
weight compared with slow, speed diesel engineplant with comparable output. 35 kg. per h.p. for
Slow Speed crosshead engine. 12 kg. per h.p. for
Medium Speed geared unit.
(b) Low head space - The low. height of
engine room enables the shipbuilder to provide a
continuous deck which may be useful for laying out
of workshop, auxiliary engines, control. room,
stores etc. A continuous deck may prove useful for
carriage of cargo in some special type of ships.
(c) Location of engine as far aft as possible is
advantageous for best utilisation of space in the
carriage of cargo. Low machinery weight enables
the ship, light or laden, to maintain a level trim
which is hardly possible for a ship fitted with slow
speed crosshead engine.
(d) The speed of engine and propeller. shaft being
independent to each other, best designed speed can
be selected for both. A free selection of propeller
revolutions ensures maximum propeller efficiency.
(e) The medium speed
application affords possibilities of
number of combinations, such as, in
line and vee engines in single or.
multi-engine layouts. The same engine
can be used for other duties like driving
alternator or cargo pump in ports.
Multi-engine plant enhances the
reliability and safety factor. It also
combines the advantage of certain
routine work being carried out at sea.
(f) The initial cost of a geared
installation may be 30 p.c. less than that
of the conventional two-stroke
crosshead engine. The spare parts are
not only cheaper, but also easier to
handle store or transported.
(g) As the engines are worked on
clean distillate or light blended heavy
oil, the rate of wear of pistons, rings
and liners are considerably less.
8/2/2019 02 Medium Speed Diesel Engine
15/15
Disadvantages to use these engines in ship for
main propulsion purpose.
High lubricating oil consumption (1.2 gm per b.h. p.
hour as against 0. 5 gm. per b.h.p. hour in crosshead
engines).
Short service life of exhaust valves.
More maintenance work
High load on bearings needing more frequent attention
and replacement,
Very high noise level.