August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Ricardo User Conference
Stuttgart, April 2014
SKIRT SHAPE OPTIMISATION FOR A
LIGHTWEIGHT GASOLINE GTDI PISTON
DONG YANG PISTON
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
1. Introduction
2. Case Study
3. Results
4. Conclusions
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
1. Introduction
2. Case Study
3. Results
4. Conclusions
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Gasoline Engine Development Drivers
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Gasoline Engine Development Drivers
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Gasoline Engine Development Drivers
Customer Requirement
 Fuel Economy - CO2 target commitments
☞ Light Weight & Low Friction
 Low Cost
 Durability
 Good NVH qualities
Piston Design Target
 Light Weight
 NVH & Low Friction
☞ Fitting Clearance, Pin Offset & Skirt Shape Optimisation
through PISDYN analysis
 Durability
☞ Design Optimisation through FEA Review
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
1. Introduction
2. Case Study
3. Results
4. Conclusions
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Case Study Engine
 Capacity (litre)
1
 Configuration
3 cylinder in-line
 Fuel Supply
Direct Injection
 Manifold System
Turbocharged
 Design Features
Crank Offset
 Max. Firing Pressure (bar)
120
 Max. Power (PS @ rev/min)
120 @ 6000
 Max. Torque (Nm @ rev/min)
200 @ 3000
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Case Study Engine
Data supplied by engine manufacturer
 3D FE Model for Cylinder Block
 Bore Distortion
 Peak Firing Pressure
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Demands on Cylinder Components
Data supplied by engine manufacturer
 Ability to withstand higher Pmax & thermal loading
 Lower friction
 Lower kinetic energy losses
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Aims of Study
 To optimise the skirt profile and ovality with respect to total skirt friction,
max. kinetic energy loss and max. skirt pressure
Four variables were selected for optimisation:-
1.Fitting Clearance
2.Profile Drop
3.Ovality
4.Pin Offset
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Selected Variables for Study
1. Minimum clearance
2. Pin offset
3. Profile drop
4. Ovality
Dong Yang R&D Center
0.03 – 0.07 mm
0.00 – 1.00 mm
0.40 – 0.80 mm
0.14 – 0.24 mm
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Variable combinations determined by DOE
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Variable combinations determined by DOE
Run
Clearance
Pin Offset
Profile Drop
Ovality
1
0.053
0.643
0.176
0.800
2
0.041
0.214
0.154
0.429
3
0.070
0.357
0.183
0.486
4
0.039
1.000
0.190
0.657
5
0.030
0.429
0.226
0.600
6
0.056
0.286
0.240
0.686
7
0.067
0.786
0.219
0.743
8
0.047
0.500
0.140
0.714
9
0.050
0.000
0.211
0.543
10
0.0643
0.071
0.161
0.629
11
0.0357
0.143
0.197
0.771
12
0.0329
0.714
0.169
0.514
13
0.0614
0.571
0.204
0.400
14
0.0586
0.929
0.147
0.571
0.0443
0.857
0.233
0.457
Dong Yang R&D15
Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Selected Engine Load Cases
Load Case
Engine Speed
(rev/min)
Pmax.
(bar)
Piston Temp
Bore Temp
Max. Power
6000
80
320
Hot
Max. Torque
3000
100
320
Hot
Part Load
1500
20
200
Room Temp
Idle
800
12
200
Room Temp
Result Assessment
Load Case
Weighting factor
- Friction
Weighting factor
– K.E. Loss
6000rpm
2
1
3000rpm
6
2
1500rpm
8
3
800rpm
4
4
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
1. Introduction
2. Case Study
3. Results
4. Conclusions
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Optimum Variables
Clearance
Offset
Drop
Ovality
6000
% Improvement
3000
% Improvement
0.48
1500 Part Load
% Improvement
800 Idle
% Improvement
Dong Yang R&D Center
0.4
0.15
KE Loss
Friction
Pressure
0.00558
0.653
20.3
55.6
33.6
-2.5
0.00774
0.349
18.8
53.2
34.7
10.9
0.00058
0.073
11.1
1.5
19.2
17.6
0.00012
0.053
11.0
9.0
19.1
18.0
0.57
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Predicted Skirt Pressure Pattern
Rated Power
Max. Torque
Part Load
Idle
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Dong Yang R&D Center
Engine Test Results
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Top Land Contact
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Skirt Ovality
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
1. Introduction
2. Case Study
3. Results
4. Conclusions
Dong Yang R&D Center
August 17th
Skirt Shape Optimisation for a Light Weight Gasoline GTDI Piston
Conclusions
1. The DOE approach gave a good spread of investigative cases
encompassing the bulk of the range of variables.
2. Weighting of the results with respect to friction and kinetic energy
loss focused the process on the key parameters under
investigation.
3. Correlation between the predicted and actual bedding patterns is
considered to be reasonable.
4. The benefits with respect to friction loss can only be confirmed
through extensive operating experience.
5. This approach allowed us to achieve close to final shape
optimisation at an early stage in the engine development process.
Dong Yang R&D Center