large engine vibration analysis using a modular modelling

Large engine vibration analysis using a modular modelling approach

Dr.-Ing. Jochen Neher

Mechanics, Engine Structure

16th, October, 2018

Dr. Alexander Rieß

Mechanics, Power Train

Marko Basic

AVL-AST d.o.o. Croatia

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Large engine vs. car engine

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Agenda short

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1 Motivation

2 Established vibration analysis disciplines

3 Virtual Engine approach

4 Modular modelling

5 Reorganised interaction

6 Next steps

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Motivation 1

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Structural Requirements

Operational Safety Comfort Aspects

Vibration analysis is essential for both requirements

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Established vibration analysis disciplines

2

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Torsional Vibration Calculation (1D)

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Conceptual design crankshaft, crank star,

firing order sequence

Vibration damper and flywheel selection to

minimize torsional stress

Vibration analysis of ship propulsion

according to classification societies

Transient Load Cases: stochastic misfiring,

power fluctuations, grid events

1D Torsional Vibration Calculation(TVC):

Transient and Steady state

0

200

0 500 [°]

p [b

ar]

gas pressure curve

pe cyl, pmax cyl, ε,

1 8

3 6

2 7

4 5

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Cranktrain Simulation

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Crankcase Vibration Simulation

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Conceptual design for crankcase, oilpan,

foundation frame, charging unit

Basis for strength analysis of main and attached

components

Efficient for complete engine series

Scope

Shell model approach

zy

x

Shell free cut at cranktrain

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Engine Mounting Simulation

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Engine-plant integration

Comfort requirement

Special load cases (earthquake, shock)

Standard: Rigid body approach

Single stage mounting 2 stage mounting

F z

F y

F x

M y M z

M x

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Airborne Noise Simulation

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Comfort requirement

Component optimization

Automated FEM Workflow

fK

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Structure Borne Noise

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Comfort requirement

Combination of analytics,

simulation, measurements

Forced excitation

(low frequency approach)

v =

Y *

F

SBN Engine

Mounting

Stiffness Excitation

Force F

FE

M Model

Unitary

Excitation Admittance

Y

F =

c *

x

SBN

Frame

Mounting

Stiffness

Foundation

Stiffness

v =

v *

f

SBN

Foundation

De

cis

ion

Limit

2DOF

Check

Compliance

Modifications

Mo

un

ting

De

sig

n

Vib

ratio

n

Asse

ssm

en

t

De

sig

n

Mo

dific

ation

F0 v0

v3F3

ZF

m2

c2

m1

c1

v2F1

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Limitations

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Established vibration analysis disciplines focus on specific problems

Interaction of engine components simplified strongly (e.g. crankshaft-crankcase)

efficient, flexible

Combination of vibration analysis disciplines relevant e.g. for

2-stage-mounted engines

Structure Borne Noise

New engine technologies different engine behavior (e.g. 7th eo 12V)

Different expert tools - obstacle for knowledge exchange between engineers

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Virtual Engine approach 3

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Virtual Engine (AVL Excite)

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Project with AVL Croatia

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Inspiration

Pilot, AVL Workflow

Rollout, MAN Workflow

Pilot, MAN

Implementation

2018

2016

2015

2017

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Virtual Engine - workflow

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Nodes:

>6,000,000

Elms:

>5,000,000

Structural matrices

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Virtual Engine example: Axial bearing - setup

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Initial EXCITE model

Standard spring/damper

MAN disciplines

HD (squeeze effect only)

EXCITE model - Update

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Virtual Engine example: Axial bearing - results

Initial Update

Updated AVL significantly improved correlation of simulation and measurement

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Virtual Engine example: Axial bearing - results

Initial Update Velocity RMS – Horizontal Velocity RMS – Horizontal

Improved vibration behavior of crankcase due to updated axial thrust bearing

Nominal speed

Complete speed range

Magnitude – Velocity - Horizontal

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Virtual Engine example: Axial bearing

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- Bearing behavior with significant impact on crankcase vibration

- Cranktrain EHD (established MAN discipline) showed detailed bearing behavior

- Implementation in Excite, simplified

- Good result

Benefit:

- Identified design sensitivity

- In cranktrain MBS and crankcase FEM (MAN disciplines), this effect is not visible

- Virtual engine + experience => benefit

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Virtual Engine example: Unbalance mass - setup

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Crankshaft modified by adding mass on flywheel bolt node:

EXCITE with unbalance: m=50kg (0.17% of total mass)

RBE2 element with added CONM2 mass

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Virtual Engine example: Unbalance mass - results

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1st Engine Order

1st Engine Order

1st Engine Order

1.5th Engine Order

Significant influence on engine motion. Lower influence on crankshaft motion.

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Virtual Engine example: Unbalance mass - results

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EXCITE w/o unbalance

EXCITE with unbalance

Operation deflection shape

Nominal speed

1st engine order

Strain – directly from EXCITE

Low influence on strain Significant influence on motion

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Virtual Engine example: Unbalance mass

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- TVC: Not relevant. No bending. Inertia not effected significantly

- Crankcase FEM: Mounting not considered in detail, difference just at 1 frequency

- Mounting calculation: Only rigid body modes considered (mostly(!), this is sufficient)

- Measurement: Balancing is expensive, difficult to distinguish between elastic and rigid modes!

- Virtual Engine shows influence in detail, also at higher frequencies

- ODS enables overall engine behaviour evaluation; frequency (order) analysis being particularly beneficial

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Experience at MAN

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Launch phase still ongoing at MAN, close collaboration with AVL

Software improvements implemented by AVL (functions, interfaces)

Virtual engine …

is a platform for different vibration disciplines improved exchange

supports a better understanding of the engine behavior

virtual engine benefits from established disciplines (efficient modelling, experience, validation)

established disciplines benefits from virtual engine (interaction)

will not replace established disciplines in the near future at MAN

validation with measurements not always satisfying, overall engine simulation remains a challenge

sometimes replaces testing

Currently, time to model is too long action required “modular modelling”

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Modular modelling

4

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Crankcase intersection modelling for 6-10L

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Base TC@CCS

+1cyl

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Crankcase intersection modelling for 6-10L

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Power Unit without liner ANSYS ACT

assembly conversion to

mass point

right inertia properties,

position in cog of

assembly, only attaching

location need

Engine Assembly Engine Section CS

Engine Section Mid

Engine Section CCS

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Alignment of models for different disciplines

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Crankcase

10L crankcase vibration model

Ansys macro

30V skeleton

10L skeleton

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Crankshaft intersection modelling for 6-10L

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Parametrized CAD

3D crankshaft

Generator

e.g. 10L crankshaft

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Alignment of models for different disciplines

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Crankshaft with identical meshes for different MBS solver

192 362 Nodes

111 150 Elements

Cranktrain simulation

Virtual Engine

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Parameterized AVL Excite model (by AVL)

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AVL Excite, engine template

Definition of approx. 300 parameters

Values defined via case table

Excel with Makros case table input

Parameters

Gas pressure curve

Calculation of bearing stiffness parameters

Automated checks

8

1

Case Set Name "Case Set 1"

Joint Type of MB NONL

Config of Engine

Param. Name for Excite Unit

Crank Train Globals General Data Engine Speed Engine_Speed rpm

Engine Speed Initial Engine_Speed_Init rpm

Number of Cylnders Num_Cyl ""

Bore Bore mm

Stroke Stroke mm

Excite parameter specification

Maintenance

Run CheckerExport casetable

Reset Cell Color

Protect This Sheet

Unprotect This Sheet

Home Input data Cylinder pressure ThresholdStiffness Technical Help

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Reorganised interaction

5

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CAD

Coupling

Engine Frame

Alternator

Ship

Foundation

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Next steps

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Next steps

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Proceed with AVL Excite launch, collaboration with AVL

Workflow validation for component (crankcase) optimization in FEM (frequency domain)

FEM excitation analytical vs.

FEM excitation with AVL Excite results

Structure Borne Noise

interaction engine ship underwater noise

evaluation of necessary modelling depth for ship excitation

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All data provided in this document is non-binding.

This data serves informational purposes only and is especially not guaranteed in any way.

Depending on the subsequent specific individual projects, the relevant data may be subject to changes and

will be assessed and determined individually for each project. This will depend on the particular characteristics

of each individual project, especially specific site and operational conditions.

Disclaimer

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Thank you very much!

Dr.-Ing. Jochen Neher

Head of Mechanics, Engine Structure

+49 821 322-2976

jochen.neher@man-es.com

16th, October, 2018