Valvetrain dynamics
A comparison between 1D model, MBD
and measurement
Tobias Winter
Hatz Diesel
Agenda
2
• About Hatz
• 1D Valvetrain dynamics – model building and results
• 3D Valvetrain dynamics – model building and ...
Hatz – the company
3
Hatz CZ
Headquarters at Ruhstorf, Germany
New Diesel, Italy
… branch offices all over the world (Fran...
Hatz – the company
4
Light-Duty-1B-Engine Family
• low fuel consumption
• reliable start-up at very low termperatures
• ti...
Hatz – the company
5
H50 engine family
• Water cooled
• Turbo charged with intercooler
• EGR, DOC  TIER IV final
• Side P...
1D Valvetrain dynamics
6
AmeSim Model for 1D dynamics
• Multiphysics approach
• Special attention to the hydraulic lash
ad...
1D Valvetrain dynamics
7
1D Valvetrain dynamics
8
Intake valve
Lift
Velocity
Acceleration
@3000 rpm
1D Valvetrain dynamics
9
Difference between designed liftcurve and dynamic liftcurve @3000 rpm
1D Valvetrain dynamics
10
Difference between liftcurves at idle speed and max operating speed
3D Valvetrain dynamics
11
Multi Body Dynamics model using Altair Motionsolve/Motionview
Flexbody
Rigid body
Part Flexbody ...
3D Valvetrain dynamics
12
Multi Body Dynamics model using Altair Motionsolve/Motionview
Contact
Joint
Connection Type
Cam-...
3D Valvetrain dynamics
13
Modeling details on the HLA and it‘s components
• Cam follower is
represented by a rigid
body
• ...
3D Valvetrain dynamics
14
Modeling details on the HLA and it‘s components
• All of the inner parts of the
HLA are represen...
3D Valvetrain dynamics
15
Results for Intake valve @ 3000 rpm
Measuring valve train dynamics
16
Testbench for measuring lift and speed (acceleration is calculated)
Measuring valve train dynamics
17
Measurement results for intake valve
Comparison
18
Comparison for intake valve @ 3000 rpm
Comparison
19
Timing deviations (according to a valve lift of 0.5mm) @ 3000 rpm in °CA
Results from Delta IVO Delta IVC
1D...
Discussion of results
20
Some additional comments on the results:
• Both simulations were conducted without measurement re...
Discussion of results
21
Some additional comments on models:
• The main advantage of the 1D approach is the detailed model...
Discussion of results
22
Improving dynamic behavior of valve train:
• Bringing more stiffness to the valve train is diffic...
Thank you for your
attention
Tobias Winter
Hatz Diesel
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Multi Body Simulation of a Valve Train, Comparison of 1D and 3D Models and Measurement

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Valvetrain dynamics can greatly influence engine characteristics such as NVH, thermodynamics and durability. Thus it’s important to gain system knowledge on the dynamic behavior at a rather early point in the design process. With the growing availability of numerical tools, such as 1D system simulation and MBD simulation accessing data on valvetrain dynamics has become more comfortable. MBD and 1D models greatly vary in terms of calculation time, model building and the ability of applying multiple physics like mechanics and hydraulics (especially important for the modeling of valve clearance compensators). Regarding the necessity of easy to use models and justifiable calculation times, at Hatz we were running a comparison between a 1D model and a MBD model regarding result quality, calculation times and model building efforts. To evaluate the results we conducted dynamic valve lift measurements on a test engine.

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Multi Body Simulation of a Valve Train, Comparison of 1D and 3D Models and Measurement

  1. 1. Valvetrain dynamics A comparison between 1D model, MBD and measurement Tobias Winter Hatz Diesel
  2. 2. Agenda 2 • About Hatz • 1D Valvetrain dynamics – model building and results • 3D Valvetrain dynamics – model building and results • Measurement of dynamic valve train behavior • Comparison between different modeling approaches and measurements
  3. 3. Hatz – the company 3 Hatz CZ Headquarters at Ruhstorf, Germany New Diesel, Italy … branch offices all over the world (France, Italy, GB, Spain, USA, Australia, …)
  4. 4. Hatz – the company 4 Light-Duty-1B-Engine Family • low fuel consumption • reliable start-up at very low termperatures • tightly arranged & low weight • high torque and output power • multi-purpose usability … Heavy-Duty-1D-Engine Family • long lasting • easy startup with crank-handle • vertical crankshaft available • multi purpose usability … 2G40/2G40H • extremely fuel economic • very good power/weight ratio • direct drive of hydraulic pumps • multi purpose usability … L/M-Series as 2, 3 & 4 Cylinder • extremely long lasting, easy to service • highly reliable due to mechanical and electronic surveillance • mutli purpose usability ...
  5. 5. Hatz – the company 5 H50 engine family • Water cooled • Turbo charged with intercooler • EGR, DOC  TIER IV final • Side PTO • 500h service intervalls • …
  6. 6. 1D Valvetrain dynamics 6 AmeSim Model for 1D dynamics • Multiphysics approach • Special attention to the hydraulic lash adjusters • No 3D setup for the rods available • Stiffness of rocker arms etc. from FEM model or analytic calculations
  7. 7. 1D Valvetrain dynamics 7
  8. 8. 1D Valvetrain dynamics 8 Intake valve Lift Velocity Acceleration @3000 rpm
  9. 9. 1D Valvetrain dynamics 9 Difference between designed liftcurve and dynamic liftcurve @3000 rpm
  10. 10. 1D Valvetrain dynamics 10 Difference between liftcurves at idle speed and max operating speed
  11. 11. 3D Valvetrain dynamics 11 Multi Body Dynamics model using Altair Motionsolve/Motionview Flexbody Rigid body Part Flexbody Rigid Body Camshaft • HLA-Housing • Pushrods • Rocker Arms • Valve • Bolt (rockers) • Bolt mounting •
  12. 12. 3D Valvetrain dynamics 12 Multi Body Dynamics model using Altair Motionsolve/Motionview Contact Joint Connection Type Cam-Follower CTC HLA-Housing  Piston Nonlinear spring HLA-Piston  Pushrod Joint Pushrod  Rocker arm Joint Rocker arm  axis Joint Rocker arm  Valve Contact Valve  seatring Contact
  13. 13. 3D Valvetrain dynamics 13 Modeling details on the HLA and it‘s components • Cam follower is represented by a rigid body • Needle bearing is represented by a stiffness value • No contact interface between cam and follower, CTC-constraint was used instead
  14. 14. 3D Valvetrain dynamics 14 Modeling details on the HLA and it‘s components • All of the inner parts of the HLA are represented by rigid bodies • Working piston is connected to the rest of the HLA by a nonlinear spring characteristic • Spring characteristic is taken from a 1D Model • But what about the damping?
  15. 15. 3D Valvetrain dynamics 15 Results for Intake valve @ 3000 rpm
  16. 16. Measuring valve train dynamics 16 Testbench for measuring lift and speed (acceleration is calculated)
  17. 17. Measuring valve train dynamics 17 Measurement results for intake valve
  18. 18. Comparison 18 Comparison for intake valve @ 3000 rpm
  19. 19. Comparison 19 Timing deviations (according to a valve lift of 0.5mm) @ 3000 rpm in °CA Results from Delta IVO Delta IVC 1D +2,7° -2,1° 3D +3,0 -3,0 Measurement +2,8 -2,2  Both modeling approaches bring good results in terms of timing deviation  3D model accuracy suffers from underestimated HLA damping
  20. 20. Discussion of results 20 Some additional comments on the results: • Both simulations were conducted without measurement results available  especially in the 3D model no tuning of contact dampings etc. was possible • Overprediction of valve lift of the 1D model was a known issue from the start, as the inclination of push rods wasn‘t taken into account (would be possible by using „planar mechanics“ library, wasn‘t available in our license package) • HLA has vital influence on the dynamic behaviour of the valve train (was a new insight for us, as this was our first engine with HLA)
  21. 21. Discussion of results 21 Some additional comments on models: • The main advantage of the 1D approach is the detailed modeling of the HLA (multiphysics) • Result quality of 3D model surely can be increased by using a 1D-3D cosimulation to give a detailed modeling of the HLA • Additional information in the 3D model (component stresses, visualization) • Calculation times of 3D model aren‘t that much longer on todays desktop workstations than those of the 1D model (~90s for 3D vs. ~4s for 1D)  3D modeling approach with a 1D cosim for the HLA seems to be best practice to access highly accurate valve train dynamic behavior. Nevertheless both approaches bring good results in terms of timing deviation
  22. 22. Discussion of results 22 Improving dynamic behavior of valve train: • Bringing more stiffness to the valve train is difficult as the HLA is the „weakest link“ • Redesign of intake cam brings improvement
  23. 23. Thank you for your attention Tobias Winter Hatz Diesel

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