wear simulation and evaluation of heavy duty exhaust valve
TRANSCRIPT
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Wear simulation and evaluation of
heavy duty exhaust valve systems
in a test rig
P. Forsberg, P. Hollman and S. Jacobson
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Exhaust valve?
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10-20 Hz
Mechanical movement
200 Bar
Up to 10 Rpm
5 µm
~75%
Cooling
channels
Heat transfer
Parameters affecting the valve system
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Wear problem
ΔVCombustion
Wear
Change of emission rates
Recession
Leakage Excessive
temperature Failure Sacramento skyranch inc.
Z.W. Yu, X.L. Xu
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Current trends changing the valve
system parameters
Reduced amount of combustion residues
increased metal/metal contact
0
8
Euro III
0 0.36 0.15 0.10 0.02
PM [g/kWh]
NO
x [g
/kW
h]
7
5
4
3
2
1
6
Euro I
Euro II
Euro IV
Euro V
Euro VI US - EPA
•Temp
•Pressure
Increased
Performance and
Lifetime
Tougher demands on emission
Japan
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Low wear High wear
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Difference in recession
900 µm
Low wear High wear
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2 µm
1 µm 10 µm
Ca, S, P, Zn, C and O
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Test rig
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Evaluation method
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Reference Valve Reference Valve seat insert
1 000 8 000
30 000 100 000
1 000 8 000
30 000 100 000
Example of result in dry air
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Evaluation of coated valves in dry
atmosphere
Reference
Polished reference
Nitrided
Polished Nitrided
Nitrided Eatonite
CrN
AlCrN
TiAlN
TiAlCrN
Stellite F: Co, Cr, Ni, W
Coated on polished
Stellite F
Crutonite: Fe, Ni, Cr
All tested against Winsert VSI: Fe, Cr, Mo, V
Test Parameters: 20kN, 7Hz, Heater ~750C
Hot air ~500C
Ts = ~200C, Tv ~420C
Eatonite: Fe, Cr, Ni
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0
1
2
1 10 100
TiAlNTiAlCrNAlCrN
RefCrNNE
Pol NpolNitrided
Wea
r sca
r wid
th [m
m]
Cycles x1000
Coated Valve results
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TiAlN
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CrN
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Conclusions from the coated
valve tests
• Stellite F too weak to support the thin
hard PVD coatings at these parameters
• Before failure the PVD coatings show
potential
0
8
Euro III
0 0.36 0.15 0.10 0.02
PM [g/kWh]
NO
x [g
/kW
h]
7
5
4
3
2
1
6
Euro I
Euro II
Euro IV
Euro V
Euro VI
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“From the literature it is clear that the main
contributor to ash emissions from diesel engines
is the lubrication oil” – P.Tornehed Thesis 2010
Different compositions found in exhaust particles
CaSO4
Zn2P2O7
ZnMg(PO4)2
Zn3(PO4)2
MnO
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Oil inlet
Hot air
First test with oil inlet
0,35 ml / min
20 kN, 7 Hz,
500 000 cycles
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100 µm
C
2 µm
Ca, P, S, Zn, O
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Comparison between the two
tribofilms
2 µm
1 µm
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• The test rig works very well!
• The oil particles/mist builds up a protective tribofilm
on the valve surface that protects the surfaces and
reduces the wear to a minimum in the test rig in a
similar way that we can see from real engine
specimens
• The high friction forces is the major contributor to
wear of the valve sealing interface
Conclusions from the first oil test
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Future work
0
8
Euro III
0 0.36 0.15 0.10 0.02
PM [g/kWh]
NO
x [g
/kW
h]
7
5
4
3
2
1
6
Euro I
Euro II
Euro IV
Euro V
Euro VI
•Build up of tribo film for different parameters
•Tear down of the tribo film?