Man B&W S50MC-C8-TII Project Manual page 320

MAN B&W
As the deflection shape for the Htype is equal
for each cylinder the N
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 /L [kN]
H
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
Then the force can be calculated as:
Force = M /L [kN]
Z H Z
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 = Force
Z, one point
Xtype Guide Force Moment (M
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):
Σ
'Bimoment' = [forcecouple(cyl.X) x distX]
in kNm
MAN B&W MC/MCC engines
order Htype guide force
th
/N [kN]
Z, total top bracing, total
)
X
2
The Xtype guide force moment is then defined
as:
M = 'BiMoment'/L [kNm]
X
For modelling purpose the size of the four (4) forc-
es can be calculated:
Force = M
where:
L is the horizontal length between 'force points'
X
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
above crankshaft centre line. These forces can be
). calculated as follows:
Z
Force
Z, one point
In order to calculate the forces it is necessary
to know the lengths of the connecting rods = L,
which are:
Engine Type
K98MC6/7
K98MCC6/7
S90MCC7/8
K90MC-C6
S80MC6
S80MCC7/8
K80MCC6
S70MC6
S70MCC7/8
L70MCC7/8
S65MCC8
S60MC6
MAN Diesel
/L [kN]
X X
M x L
_____
= [kN]
x
L x L
L in mm
Engine Type
3,220 S60MCC7/8
3,090 L60MCC7/8
3,270 S50MC6
3,159 S50MCC7/8
3,504 S46MC-C7/8
3,280 S42MC7
2,920 S40MCC9
3,066 S35MCC9
2,870 S35MC7
2,660 L35MC6
2,730 S26MC6
2,628
17.05
Page 3 of 3
Z
L in mm
2,460
2,280
2,190
2,050
1,980
2,025
1,770
1,550
1,600
1,260
1,125
198 59 045.2