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

Valvetrain dynamics A comparison between 1D model, MBD

and measurement

Tobias Winter

Hatz Diesel

Agenda

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• 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

Hatz – the company

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Hatz CZ

Headquarters at Ruhstorf, Germany New Diesel, Italy

… branch offices all over the world (France, Italy, GB, Spain, USA, Australia, …)


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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

...


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H50 engine family

• Water cooled

• Turbo charged with intercooler

• EGR, DOC TIER IV final

• Side PTO

• 500h service intervalls

• …

1D Valvetrain dynamics

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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


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Intake valve

Lift

Velocity

Acceleration

@3000 rpm


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Difference between designed liftcurve and dynamic liftcurve @3000 rpm


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Difference between liftcurves at idle speed and max operating speed


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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 •


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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


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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


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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?


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Results for Intake valve @ 3000 rpm

Measuring valve train dynamics

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Testbench for measuring lift and speed (acceleration is calculated)

Measuring valve train dynamics

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Measurement results for intake valve

Comparison

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Comparison for intake valve @ 3000 rpm

Comparison

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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

Discussion of results

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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)


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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


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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

Thank you for your

attention

Tobias Winter

Hatz Diesel