1 © Wärtsilä
Investigation of the lubrication conditions in bearings of large two-stroke diesel engines
GT-SUITE ConferenceFrankfurt, 09.11.2009
François Terrettaz, Dr. Wilfried SchifferWärtsilä Corporation
2 © Wärtsilä
Content
1. Introduction / purpose of investigation
2. Wärtsilä two-stroke diesel engines
3. Lubrication, crosshead and crank pin bearings
4. Model and simulation requirements
5. Simulation of previous generation engines
6. Simulation of new generation engines
7. Summary
8. Next steps
3 © Wärtsilä
1. Introduction / purpose of investigation
Purpose
• simulation of the unsteady lubrication conditions for crosshead and crank pin bearings of large two-stroke engines with GT-SUITE
To be considered• acceleration of oil due to movement of knee lever and ConRod• crank angle based resolution of crosshead and crank pin bearings solution
using appropriate boundary conditions in oil grooves and pockets
• fast motion of crosshead pin
• pressure pulsation in pipes and bores of oil circuit
-> interaction between oil circuit and bearings(crosshead and crank pin)
4 © Wärtsilä
1. Introduction / purpose of investigation
Simulation results
• oil consumption of crosshead and crank pin bearings• oil pressure at entry of crosshead and crank pin bearing over one revolution
-> to be used as boundary conditions for EHD-calculations• risk of cavitation in oil pipes and bores• efficiency of different supply systems (-> telescopic pipe or knee lever)
5 © Wärtsilä
2. Wärtsilä two-stroke diesel engines
• Crosshead engine
• Welded crank casing
• Semi-build crankshaft
• Power range 5’800 to 80’080 kW
• Speed range 61 to 137 rpm
• Number of cylinders 5 to 14 (in-line)
• Bore range 0.48 to 0.96 m
• Stroke range 1.8 to 3.375 m
• Stroke-to-bore ratio 2.60 to 4.17
• Weight range 171 to 2’300 tons
6 © Wärtsilä
2. Wärtsilä two-stroke diesel engines
Output [kW]Output [bhp]
100’000
80’000
60’000
40’000
20’000
10’000
8’000
6’0004’000
6’000
8’000
20’000
80’000
60’000
50’000
30’000
10’000
40’000
60 70 80 90 100 120 140
Engine speed [rpm]
RTA68T-B
RTA84T-D
RTA84C
RTA58T-B
RTA48T-B
RTA72U-B
RT-flex60CRTA62U-B
RTA52U-B
RTA96CContainer vessels
RTA84T-DTanker vessels
RTA84T-D
RTA48T-B
Bulk carrier vesselsRTA48T-B
7 © Wärtsilä
2. Wärtsilä two-stroke diesel engines
7RTA48T-B
power 10185 kWmass 225 tlength 7.6 mwidth 4.8 mheight 9.0 m
10RTA96C
power 57200 kWmass 1760 tlength 20.6 mwidth 7.5 mheight 13.5 m
8 © Wärtsilä
2. Wärtsilä two-stroke diesel engines
9 © Wärtsilä
pump
supply pipe
main gallery
knee lever
crosshead
connecting rod
crank pin bearing
crosshead bearing
3. Lubrication, crosshead and crank pin bearings
main gallery
knee lever(2 articulated pipes)
crosshead bearing
crank pin bearing
10 © Wärtsilä
4. Model and simulation requirements
Crosshead bearing
Crank angle based resolution ofbearing solution using Mobility method
• accurate bearing forces, including forces generated by pressure in large oil pockets
• accurate crosshead pin displacement
• oil flow rate according to Martin equation
11 © Wärtsilä
4. Model and simulation requirements
Crank pin bearing
Crank angle based resolution ofbearing solution using Mobility method
• accurate bearing forces, including force generated by pressure in oil grooves
• accurate crank pin displacement
• oil flow rate according to Modified Martin equation (s=0.6)
12 © Wärtsilä
4. Model and simulation requirements
Knee lever (at engine full speed)
acceleration: ± 300 m/s2
Acceleration Pressure
pressure: ± 1.7 bar
-2.0
-1.0
0.0
1.0
2.0
3.0
0 90 180 270 360
Crank Angle [deg]Pr
essu
re [
bar]
-400
-300
-200
-100
0
100
200
300
0 90 180 270 360
Crank Angle [deg]
Acc
eler
atio
n [m
/s2 ]
Centre of 1st. pipe of knee lever
Centre of 2nd. pipe of knee lever
Oil Acceleration
13 © Wärtsilä
4. Model and simulation requirements
ConRod bore (at engine full speed)
-200
-150
-100
-50
0
50
100
150
0 90 180 270 360
Crank Angle [deg]
Acc
eler
atio
n [m
/s2 ]
Oil Acceleration (at Centre)
acceleration: ± 150 m/s2
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
0 90 180 270 360
Crank Angle [deg]Pr
essu
re [
bar]
Acceleration Pressure
pressure: ± 2.5 bar
14 © Wärtsilä
4. Model and simulation requirements
Coupling: pin movement oil pressure
DATAFIL211 07. Jan 99 11:10low oil pressure
0
1
2
3
4
5
6
7
8
9
10
0 30 60 90 120 150 180 210 240 270 300 330 360crank angle [deg]
oil s
upp
ly p
ress
ure
[bar
]
X-head pressure before leverX-head pressure after lever
Speed: 100 %Power: 10 %
Displacement of crosshead pin:
• fast motion in vertical direction
• engine load (= speed) dependant
• huge influence on oil flow rate
• influence on instantaneous pressurein oil bores close to crosshead andcrank pin bearings and reciprocal
prediction of orbital path and oil flow rate as accurate as possible
Pressure at Entry ofCrosshead Bearing (meas.)
-0.3
-0.2
-0.1
0.0
0.1
0.2
0 30 60 90 120 150 180 210 240 270 300 330 360
Crank Angle [deg]
Vert
ical
Dis
pl. [
mm
]
Pin Displacement (simul.)
Crank Angle [deg]
Oil
Pres
sure
[ba
r]
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5. Simulation of previous generation engines
to Crankpin Bearing
low pressure main gallery
high pressure main gallery
• separate oil system for crosshead and crank pin bearing
• 10 12 bar bar feed pressure
• small volume for main gallery
• pressure in main gallery influenced by each crosshead
-> pressure not constant
-> oil circuit must be fully modelled
16 © Wärtsilä
5. Simulation of previous generation engines
Results for 50% loadCrosshead pressurebefore lever
Crosshead pressureafter lever
GT-SUITE Simulation
0
2
4
6
8
10
12
14
16
18
Oil
pres
sure
[ba
r]
Crosshead pressure before lever
Crosshead pressure after lever
DATAFIL 123 0 7 Dec 1 998 15:05high oil pre ss u re
0
2
4
6
8
10
12
14
16
18
0 30 60 90 120 150 18 0 210 240 270 3 00 330 360
crank angle [de g]
oil s
upp
ly p
ress
ure
[ba
r]
o il p ressure be fo re ma in bearingX-head pres sure be fo re leverX-head pres sure a fte r leverp is ton c oo l . press. a fte r lev er
Speed: 100 %Pow er: 50 %Measurement
Crank angle [deg]
Oil
pres
sure
[ba
r]
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5. Simulation of previous generation engines
Oil consumption crosshead + crank pin bearing
0.0
1.0
2.0
3.0
4.0
5.0
0 10 20 30 40 50 60 70 80 90 100Engine Load [%]
Lub.
Oil
Con
sum
ptio
n [m
3 /h/c
yl] Measurement
GT-SUITE Prediction
18 © Wärtsilä
6. Simulation of new generation engines
to Crankpin Bearing
main gallery
• single oil circuit for almost all engine components
• 5 bar feed pressure
• big volume of main gallery, many sub-volumes connected
• constant pressure
• pressure pulsations fully damped
19 © Wärtsilä
6. Simulation of new generation engines
Oil pressure (at full load)
Crosshead pressurebefore lever
Crosshead pressureafter lever
GT-SUITE Simulation
0
1
2
3
4
5
6
7
8
9
10
Oil
pres
sure
[ba
r]
Crosshead pressure before lever
Crosshead pressure after lever
DATAFIL186 05. Jan 99 10:44low oil pressure
0
1
2
3
4
5
6
7
8
9
10
0 30 60 90 120 150 180 210 240 270 300 330 360
crank angle [ deg]
oil s
uppl
y pr
essu
re [b
ar]
X-head pressure before leverX-head pressure after lever
Speed: 97 %Pow er: 90 %
Measurement
Crank angle [deg]
Oil
pres
sure
[ba
r]
20 © Wärtsilä
6. Simulation of new generation engines
0.0
1.0
2.0
3.0
4.0
5.0
0 10 20 30 40 50 60 70 80 90 100Engine Load [%]
Lub.
Oil
Con
sum
ptio
n [m
3 /h/c
yl] Measurement
GT-SUITE Prediction
Oil consumption crosshead + crank pin bearing
21 © Wärtsilä
6. Simulation of new generation engines
Comparison oil consumption at full load with result for previousengines
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Lub.
Oil
Con
sum
ptio
n [m
3 / h
/ Cyl
]
Measurements
GT-SUITE Prediction
5 bar Feed Pressure 12 bar Feed Pressure
22 © Wärtsilä
7. Summary
Oil flow rate prediction• at full load good compliance between simulation and measurement• at part load correct trend• below 40% load oil flow rate prediction is less accurate• Martin equation used for crosshead bearing• modified Martin equation (s=0.6) used for crank pin bearing
Pressure at entry and exit of knee lever• new generation engines (-> constant pressure in main gallery):
- calculated pressure in line with measurement- oil acceleration in knee lever and ConRod is correctly taken into account- crosshead / crank pin bearing behaviour accurate
• previous generation engines (-> fluctuating pressure in main gallery):
- agreement between calculation and measurement less good
23 © Wärtsilä
8. Next steps
• simulation of lubrication conditions using a telescopic pipe instead of knee lever
• prediction of cavitation risk in crosshead and crank pin bearing
• simulation of other engines components-> axial damper at free end of crankshaft
• implement oil lubrication pressure as result from GT-SUITE simulation for EHD calculations of crosshead and crank pin bearings
24 © Wärtsilä
The end
Thank you for your kind attention
Thanks to GAMMA Technologies and in particular
to Jon Harrison for excellent support !!