WinGD X72DF, Руководство по установке

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Marine Installation Manual 2021-08 6-2
6 Engine Dynamics
6.1 External mass forces and moments
X72DF
6.1 External mass forces and moments
The external mass forces and moments are the resulting forces and moments pro -
duced by reciprocating and rotating masses of the running gear (i.e. the engine's
main oscillating masses) that are transmitted to the surrounding vessel via the
foundation. Therefore, this does not consider forces and moments that are pro
-
duced by combustion forces (see section 6.2,

6-6 ). The external mass forces
and moments depend on the design of a specific engine and the engine speed.
The engine power has no influence on the external mass forces and moments.
Figure 6 - 1 External mass forces and moments
Figure 6 - 1 shows the mass forces and moments generated by the engine. How -
ever, where possible these are neutralised. If not, cyclical generation of the ex -
ternal mass forces and moments may lead to unwanted and disturbing vibrations
throughout the vessel. This highlights the importance of using countermeasures
that balance out the generated mass forces and moments where possible.
6.1.1 Balancing of mass forces and moments
Forces
With a regular firing order of evenly distributed crank angles, an engine will in -
herently balance the summation of all vertical (F
V
) and horizontal (F
H
) free
forces. Sometimes the firing order is designed to be irregular, i.e. unevenly dis -
tributed crank angles, to optimise the overall vibration characteristic of a specific
engine type. Regardless, the resulting mass forces are considered to be negligible.
First order moments
First order mass moments (M
1V
and M
1H
) can be reduced to acceptable levels by
introducing standard counterweights, fitted to the ends of the crankshaft. In spe -
cial cases non-standard counterweights can be used to reduce either vertical
(M
1V
) or horizontal (M
1H
) first order mass moments as required.
Standard counterweights fitted to the ends of the crankshaft reduce the first order
mass moments to acceptable limits. However, in special cases non-standard
counterweights can be used to reduce either M
1V
or M
1H
.
SM-0030
Resulting first order vertical mass force
Resulting first order horizontal mass force
Resulting second order vertical mass force
Resulting fourth order vertical mass force
First order vertical mass moment
First order horizontal mass moment
Second order vertical mass moment
Fourth order vertical mass moment
F
1V
F
1H
F
2V
F
4V
M
1V
M
1H
M
2V
M
4V
+
F
1V
, F
2V
, F
4V
F
1H
M
1V
, M
2V
, M
4V
M
1H
+
-