New findings about friction in combustion engines
and new test device for measurement of piston
ring – cylinder liner friction
Markus Söderfjäll
Supervisors:
Roland Larsson
Andreas Almqvist
Power cylinder unit
2
Components in the PCU
• Piston assembly
– Piston
– Piston rings
• Compression ring
• Scraper ring
• Oil control ring
• Cylinder liner
3
Losses in the PCU
Distribution of total energy
Distribution of piston ring
and connecting rod friction
Distribution of mechanical friction
Distribution of piston ring
assembly friction
PCU is responsible for
1.1-6.8% of the total
losses in a heavy duty
diesel engine
Richardson, 2000, Review of power
cylinder friction for diesel engines
4
Possible ways of reducing friction
Reduced ring tension
– Rings will conform less to liner
• Increased oil consumption
• Increased blow by
𝐹𝑓 = µ ∙ 𝐹𝑛
– Combined with reduced out of roundness
Δr
nd
2
rd
3
th
4
5
Simulation model
• FEM
• Twin land oil control ring
– Not allowed to rotate
• Reynolds equation
– Fully flooded inlet
• Luleå Mixed Lubrication Model (LMLM)
– Contact model
– Flow factors
• 3D structural mechanics model
6
Simulation model
Fh + Fc
Ph+Pc
Fh + Fc
Ph= Hydrodynamic pressure
Ph+Pc
Pc= Contact pressure
Fh = Hydrodynamic friction
Fc = Contact friction
Rt = Ring tension
Pa = Contact pressure from piston groove
Pah = Axial damping
Rt
Pa+Pah
U
Simulation parameters
•
•
•
•
•
Parabolic ring profile
Measured cylinder liner surface
Stationary cases at mid-stroke
Out of round cylinder liners
Varied parameters:
– Tangential load
– Scaled out of roundness
Order of OOR
Max amplitude [µm]
AVL Glide User’s Manual 2000
2
3
4
5
6
8
32.5
20.8
15.6
7.8
5.2
3.9
Results
-6
10
Friction force (N)
9.5
9
8.5
Average minimum separation (m)
10.5
100%
77%
55%
33%
11%
0%
8
7.5
7
6.5
6
25
30
35
40
45
50
Tangential load (N)
55
60
4.5
x 10
100%
77%
55%
33%
11%
0%
4
3.5
3
2.5
2
1.5
25
30
35
40
45
50
Tangential load (N)
55
60
9
Test rig specification
•
•
•
•
Validation of simulation model
Component test rig
Higher speeds than earlier rigs
Variable parameters
– Speed
– Temperature
– Out of roundness
• Measure friction
Test rig
• Low vibration
– First two orders cancels
Test rig
Test rig
Tack till
Contact
Markus Söderfjäll
Avdelningen för maskinelement
Luleå tekniska universitet
[email protected]
Results
Scaling
100%
80%
60%
40%
20%
0%
Required tangential force (N)
56
47.7
40.7
35.3
32
31
Total friction force (N)
16.4
13.9
11.9
10.4
9.4
9.2
Friction reduction (%)
-
15
27
37
43
44
Results
Min separation for lower land on TLOCR against OOR
bore
Ring land twist against out of round bore
Upper land
Lower land
Internal twist between ring lands
Test rig
Test rig