1. Oil Bearing Calculations in Ship
Diesel Engines Using MotionSolve
Steen Cosmus Thaning
Senior Research Engineer
LDD1 / MAN-DK
© MAN Diesel <1>

2. MAN Group
Globally active supplier of vehicles, engines and machinery
Approx. €15,5 billion in sales, over 55,000 employees in 120 countries
Four leading business areas
Commercial Vehicles
Trucks Buses
Engines Services
Diesel Engines Industrial
2-stroke 4-stroke Propulsion Services
Turbochargers Services Packages
Contracting
Logistics
Service
Turbomachinery platform
Compressors Turbines
Reactors Services
© MAN Diesel <2>

3. MAN Diesel Group
Locations in Europe
Employees worldwide: 7,500
Great Britain
MAN Diesel Ltd. Denmark
After-sales services Frederikshavn
MAN Diesel A/S,
Two- and four-stroke engines,
propellers and propulsion
Copenhagen
packages, after-sales
Holeby services
Stockport
Rostock
Hamburg
Colchester
Villepinte/Paris
France Czech Republic
Augsburg Velká Bìteš PBS Turbo s.r.o.
MAN Diesel SAS Saint-Nazaire
Turbochargers
Four-stroke engines, after-
sales services
Germany
MAN Diesel SE
Status: 12/05
Headquarters, four-stroke
engines, turbochargers,
after-sales services
© MAN Diesel <3>

4. Low-speed Licensees
China Croatia Japan
HHM 1980 Uljanik 1954 Mitsui 1926
DMD 1980 Split 1967 Makita 1981
YMD 1989 Hitachi 1951
CMD 2007 Kawasaki 1923
STX 2007
JAD 2007
ZJCME 2008
ZHD 2008
RPM 2008 Korea Poland
Hyundai 1976 Cegielski 1959
Doosan 1983
STX 1984
Russia Vietnam
Bryansk 1959 Vinashin 2004
L/1442-5.11/2009.08.06 (LL/JBB) © MAN Diesel

5. Introduction: The Product
Large Two-Stroke Diesel Engines
Two-stroke
10K98MC-C Crosshead
and Turbo charged
6S35MC Low speed, 61-250 RPM
Bore from 26 to 108 cm
Stroke from 0.98 to 3.45 m
Engine height from 5 to 16 m
4 to 14 cylinders
Engine weight from 32 to 2800
tonnes
Engines range from 2.100 to
132.000 BHP
Continuous demand for cost
reduction
Reliability is crucial
© MAN Diesel 5

6. © MAN Diesel <6>

7. Illustration of crankshaft revolutions
© MAN Diesel <7>

8. Motionsolve
Crankshaft to bedplate interface
Traditional crankshaft to bedplate interface
Crankshaft dynamics are evaluated with few boundary conditions to bedplate. The
dynamics are calculated in frequency domain on a discrete model. Inhouse build
The interface to the bedplate is handled by a 3D FEM Elasto Hydrodynamic oilfilm
calculation program. Forces and rotations of journal are used as input. Inhouse build
New approach
• Two major non-linearities from the bedplate behaviour and from the oilfilm are
included into the main-bearing calculation. FEM–model time-domain.
© MAN Diesel

9. Motionsolve
Basic model
Piston and connecting rod and
crankshaft is made from flexible bodies
Translational joint
Linear stiffness bushings
Variable stiffness of bedplate
Redistribution of load from movement of crankshaft inside bearing clearance
© MAN Diesel

10. Motionsolve
Forces
Gasforce applied at piston from
curve interpolation and function
AZU which returns unwrapped
angle.
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11. Motionsolve
Forces
Non-symmetric thrust bearing
Load approx. 500 tons
Revolution dependent torque at
aftend of engine
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12. Motionsolve
Stiffness variation of bedplate
Stiffness of bedplate varies with
load angle.
FEM contact analysis has been
made to give variation curve in
vertical and horisontal direction.
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13. Motionsolve
Forces of bushings without oil interface
nonlinear main bearing stiffness.
Force response in horisontal and
vertical direction of bushing is
calculated with regard to actual
deformation size and angle.
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14. Reynolds Equation
1 ∂ ⎛ h3 ∂p ⎞ ∂ ⎛ h3 ∂p ⎞ ω ∂h ∂h
⎜ ⎟+ ⎜ ⎟= +
r ∂θ ⎝ 12η ∂θ ⎠ ∂z ⎝ 12η ∂z ⎠ 2 ∂θ ∂t
2
h : Oil Film Thickness (Distance between bearing surfaces)
ω : Sliding velocity of bearing surface Air
Oil
p : Pressure in bearing Journal
η : Viscosity
Shell Y
∂h : Inclination of bearing surface X
θ
∂θ Z
∂h : Squeeze of bearing surface (dynamics)
∂t
ω
© MAN Diesel

15. Model Considerations
Simplifications to Reynolds Equation
Assume Short width bearing theory applies
1 ∂ ⎛ h3 ∂p ⎞ ∂ ⎛ h3 ∂p ⎞ ω ∂h ∂h
⎜ ⎟+ ⎜ ⎟= +
r ∂θ ⎝ 12η ∂θ ⎠ ∂z ⎝ 12η ∂z ⎠ 2 ∂θ ∂t
2
Half Sommerfeld solution applies
p ≥ 0 for ϕ1 ≤ θ ≤ ϕ2 where ϕ 2 = ϕ1 + π Y
p = 0 otherwise
Result θ X
Z
Model can be set up analytically
ω
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16. Coupled Calculation
Oil Film vs. Structure
Fx Fy
VFOSUB
(MAN-BEAST) x y dx/xt dy/dt
© MAN Diesel 16

17. Motionsolve
Application of user subroutine
User subroutine is included by a DLL
Calling of user subroutine
Width radius,clearance,viscosity,angular velocity and
deformation and velocity
Oil film calculation subroutine VFOSUB
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18. Motionsolve
Results for 11 cylinder engine
Journal movement
Inside clearance
MB3
Bedplate movement
MB10
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19. Motionsolve
The loading of engine structure
Main bearing loads along with other loads
are used to optimise the engine structure
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20. Motionsolve
Conclusive remarks
• A model of the interface between crankshaft mechanism and
bedplate structure has been made in MOTIONVIEW.
• Takes into account the variable stiffness of bedplate as well as the
redistribution of load from the movement of crankshaft journal inside
the clearance.
• Model will improve the Elastohydrodynamic evaluation of mainbearings and
thereby make loading of the bedplate structure more accurate.
© MAN Diesel

21. © MAN Diesel < 21 >