General Description - Man L23/30DF Project Manual

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L27/38S, L27/38
Figure 2: Cylinder liner.
The liner can thus expand freely downwards when
heated during the running of the engine. The liner is
of the flange type and the height of the flange is
identical with the water cooled area which gives a
uniform temperature pattern over the entire liner
surface. The lower part of the liner is uncooled to
secure a sufficient margin for cold corrosion in the
bottom end. There is no water in the crankcase
area.
The gas sealing between liner and cylinder head
consists of an iron ring.
To reduce bore polishing and lube oil consumption
a slip-fit-type top land ring is arranged on the top
side of the liner.
Cylinder head
The cylinder head is of cast iron with an integrated
charge air receiver, made in one piece. It has a
bore-cooled thick walled bottom. It has a central
bore for the fuel injection valve and 4 valve cross
flow design, with high flow coefficient. Intensive
water cooling of the nozzle tip area made it possible
to omit direct nozzle cooling. The valve pattern is
turned about 20° to the axis and achieves a certain
intake swirl.

General description

The cylinder head is tightened by means of 4 nuts
and 4 studs which are screwed into the engine
frame. The nuts are tightened by means of hydraulic
jacks.
The cylinder head has a screwed-on top cover. It
has two basic functions: oil sealing of the rocker
chamber and covering of the complete head top
face.
Figure 3: Cylinder head.
Air inlet and exhaust valves
The valve spindles are made of heat-resistant mate-
rial and the spindle seats are armoured with wel-
ded-on hard metal.
All valve spindles are fitted with valve rotators which
turn the spindles each time the valves are activated.
The turning of the spindles ensures even tempera-
ture levels on the valve discs and prevents deposits
on the seating surfaces.
The cylinder head is equipped with replaceable
valve seat rings. The exhaust valve seat rings are
water cooled in order to assure low valve tempera-
tures.
The seat rings are made of heat-resistant steel. The
seating surfaces are hardened in order to minimize
wear and prevent dent marks.
MAN Diesel & Turbo
1689477-8.1
Page 2 (7)
2015.11.26