wear simulation and evaluation of heavy duty exhaust valve
TRANSCRIPT
Wear simulation and evaluation of
heavy duty exhaust valve systems
in a test rig
P. Forsberg, P. Hollman and S. Jacobson
Exhaust valve?
10-20 Hz
Mechanical movement
200 Bar
Up to 10 Rpm
5 µm
~75%
Cooling
channels
Heat transfer
Parameters affecting the valve system
Wear problem
ΔVCombustion
Wear
Change of emission rates
Recession
Leakage Excessive
temperature Failure Sacramento skyranch inc.
Z.W. Yu, X.L. Xu
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
Low wear High wear
Difference in recession
900 µm
Low wear High wear
2 µm
1 µm 10 µm
Ca, S, P, Zn, C and O
Test rig
Evaluation method
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
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
0
1
2
1 10 100
TiAlNTiAlCrNAlCrN
RefCrNNE
Pol NpolNitrided
Wea
r sca
r wid
th [m
m]
Cycles x1000
Coated Valve results
TiAlN
CrN
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
“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
Oil inlet
Hot air
First test with oil inlet
0,35 ml / min
20 kN, 7 Hz,
500 000 cycles
100 µm
C
2 µm
Ca, P, S, Zn, O
Comparison between the two
tribofilms
2 µm
1 µm
• 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
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?