Man B&W L35MC6-TII, Project Manual

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MAN B&W 17.05
Page 3 of 3
MAN Diesel
MAN B&W MC/MCC engines 198 59 045.2
As the deflection shape for the Htype is equal
for each cylinder the N
th
order Htype guide force
moment for an Ncylinder engine with regular fir-
ing order is:
N x M
H(one cylinder)
For modelling purposes the size of the forces in
the force couple is:
Force = M
H
/L [kN]
where L is the distance between crankshaft level
and the middle position of the crosshead guide
(i.e. the length of the connecting rod.)
As the interaction between engine and hull is at
the engine seating and the top bracing positions,
this force couple may alternatively be applied in
those positions with a vertical distance of (L
Z
).
Then the force can be calculated as:
Force
Z
= M
H
/L
Z
[kN]
Any other vertical distance may be applied, so as
to accomodate the actual hull (FEM) model.
The force couple may be distributed at any
number of points in the longitudinal direction. A
reasonable way of dividing the couple is by the
number of top bracing and then applying the forc-
es at those points.
Force
Z, one point
= Force
Z, total
/N
top bracing, total
[kN]
Xtype Guide Force Moment (M
X
)
The Xtype guide force moment is calculated
based on the same force couple as described
above. However as the deflection shape is twist-
ing the engine each cylinder unit does not contrib-
ute with an equal amount. The centre units do not
contribute very much whereas the units at each
end contributes much.
A socalled ‘Bimoment’ can be calculated (Fig.
17.05.02):
‘Bimoment’ =
Σ
[forcecouple(cyl.X) x distX]
in kNm
2
The Xtype guide force moment is then defined
as:
M
X
= ‘BiMoment’/L [kNm]
For modelling purpose the size of the four (4) forc-
es can be calculated:
Force = M
X
/L
X
[kN]
where:
L
X
is the horizontal length between ‘force points’
Similar to the situation for the Htype guide force
moment, the forces may be applied in positions
suitable for the FEM model of the hull. Thus the
forces may be referred to another vertical level L
Z
above crankshaft centre line. These forces can be
calculated as follows:
Force
Z, one point
=
M
x
x L
_____
L x L
[kN]
In order to calculate the forces it is necessary
to know the lengths of the connecting rods = L,
which are:
Engine Type L in mm
K98MC6/7 3,220
K98MCC6/7 3,090
S90MCC7/8 3,270
K90MC-C6 3,159
S80MC6 3,504
S80MCC7/8 3,280
K80MCC6 2,920
S70MC6 3,066
S70MCC7/8 2,870
L70MCC7/8 2,660
S65MCC8 2,730
S60MC6 2,628
Engine Type L in mm
S60MCC7/8 2,460
L60MCC7/8 2,280
S50MC6 2,190
S50MCC7/8 2,050
S46MC-C7/8 1,980
S42MC7 2,025
S40MCC9 1,770
S35MCC9 1,550
S35MC7 1,600
L35MC6 1,260
S26MC6 1,125