powertrain nvh analysis - nvhskeylab.com

Wolfgang SCHWARZ

AVL France

Public

POWERTRAIN NVH ANALYSIS

From Engine via Transmission to the Entire Drive Line

Wolfgang SCHWARZ | AST France | 20 février 2017 | 3Public

• Introduction

• Review of numerical analysis methods for powertrain NVH

• Root cause analysis – piston impact noise

• Transmission & driveline noise analysis

• NVH of electric & hybrid drive lines

• Conclusion & Outlook

CONTENT


INTRODUCTION AND MOTIVATIONNVH GENERATION AND TRANSFER PROCESS

0 200 400 600 800 1000 1200 1400 1600 1800 2000

2000

3000

4000

5000

6000

7000

0

10

20

30

40

50

60

70

Sporty

Powerful

Frequency - Hz

En

gin

e S

pee

d -

rp

m

Inte

rio

r N

ois

e L

evel

- d

BA

Frequency

En

gin

e S

peed

NVH is to a high extend subjective

Subjective

Assessment

(Customer)

Source /

Excitation

Mechanism

Amplification /

Damping,

Transfer

Response,

Result &

Assessment

Objective

Assessment

(Legislation)

Trade Offs with:

• Power Generation, Performance

• Fuel Consumption and Emissions

• Temperature and Thermal Management

• Packaging and Weight

• Durability

• Costs

• …Sporty

e.g. oil level / viscosityefficiency rattle!


Modern powertrain noise and vibration (NV) investigation in the development process or during trouble shooting is a combination of experimental and simulation investigations.

In simulation in recent years main focus was set on three major targets:

Model complexity and completeness for the target frequency range ( 0 to

3.5-5 kHz)

Consideration of all main excitation mechanisms and excitation sources (combustion, crank train, valve and timing drive, piston secondary motion, transmission noise, fuel system, auxiliary parts and drives, orifice noise, …)

Efficient and stabile numerical algorithms (FEM, MBD, BEM/iFEM/WBT, …)

By that, the total response of the virtual powertrain is already comparable to the overall noise level of the real powertrain (differences of local surface velocity levels in the range of 3 to 5 dB).

INTRODUCTIONNUMERICAL NV INVESTIGATION


NVH GENERATION AND TRANSFER PROCESS AND ROOT CAUSE DETECTION

Microphone position

structural response

Internal force path (transfer function)

Transfer

Source /

Excitation

Mechanism

Response

External force path / radiation (transfer

function)

Accelerometer position

excitation source , mechanisms and

driving parameters

Microphone array

radiated air

borne noise “What” is?

Target: “Why” and “How to improve”? Requires Link between Response,

Transfer and Source / Driving Parameters


• Introduction






CONTENT


NVH MULTIBODY SIMULATION APPROACH

Characteristics

Elastic/rigid bodies interacting via non-linear joints

Vibrating, rotating and oscillating elastic structure parts represented by condensed FE models (CMS)

Various contact models up to highly complex thermo elasto-hydrodynamic joints including mixed lubrication

Non-linear transient forced vibration analysis in time domain

Excited by external forces

Typical number of master degrees-of-freedom (DOFs) 500 – 5.000 and much more in certain cases.

Gas Pressure

VT&TD Excitations

Piston Slap

Excitation Forces and Moments

Radial Slider Bearing,

Axial Thrust Bearing,

Piston / Liner Contact,

Rotational Coupling, ...

Nonlinear Bearing

Forces and Moments

calculated due to

Actual Dynamics of

Parts

Vibrating

Structure Parts

Vibrating, Rotating,

Oscillating PartsMBS solver

+ possibly other excitations coming from fuel injection system etc.


NVH ANALYSIS USING FEM AND MBS GENERAL WORKFLOW

CAD Data

Generation of FE Models for Separate Bodies

Verification of FE Models - Modal Analysis

Matrix Preparation (i.e. Condensation)

Reduced Stiffness and Mass Matrices

Dynamic Calculation with Multi-Body Solver Considering

all relevant Excitations for Entire Operating Range

Simulation with Condensed System

Durability Investigation

Calculation of Structural

Stresses

Evaluation of Motion Quantities

Extraction of Boundary Conditions for FEM Analysis

Durability

evaluation

FEM

Fatigue

Evaluation

MBS

Pre-

Processing

FEM

Structure borne

noise

Noise Radiation Evaluation

Calculation of Surface

Velocity Levels

Noise

Radiation

Vibrating and

moving

components

Vibrating

structures

Condensed

system

Noise

radiation

Joints and Connections


Comprehensive Simulation Model Fully elastic; oil film bearings

COMBUSTION NOISE- ROUGHNESS

NVH ANALYSIS - BASICS

EHD

bearings

All parts

flexible

Measured

Cylinder Pressure

Engine Mount

Dynamic StiffnessEngine Mount

Dynamic Stiffness

Engine Mount

Dynamic Stiffness

TVD Dynamic

Stiffness & DampingEHD

bearings


Powertrain NVH Assessment

Installation on powertrain test bed

Application of sensors

Close to main bearing (excitation correlation)

Engine surface (flexible part correlation)

Data acquisition

Data evaluation and comparison to simulation

NVH ANALYSISSIMULATION MODEL VERIFICATION


Sensor Position x, y, z

NVH ANALYSISSIMULATION MODEL VERIFICATION


Variety of methods exist:

Modal Contribution Analysis

Transfer Path Analysis

NVH Source Identification

NVH ANALYSISROOT CAUSE ANALYSIS

Cam cover


Target: Identification of the contribution of all main excitation mechanisms for certain regions and frequency ranges

Stepwise activation of different excitations

EXCITATION SOURCE RANKINGDETECT MAIN CONTRIBUTING EXCITATION

Excitation Level #1

Gas Force

Excitation Level #3

as #2 Timing Drive

added

Excitation Level #2

Gas Force,

Piston Slap


PERFORMANCE ATTRIBUTES (PA) DRIVEN DEVELOPMENT PROCESS AND TARGET SETTING

PA selection & target

definition

Results evaluation

Evaluation of PA

against the target

Status check & history review

Request design

change if PA target is not

achieved

Speed [rpm]

Acc

eler

atio

n [

g]

Target

Design progress

PA update

Virtual

Release


• Introduction






CONTENT


Stroke

Lateral

Tilting

Axial

Rotation

Bending

EXAMPLE FOR PERFOMANCE ATTRIBUTEPISTON NOISE EXCITATION INDEX

Main driving parameters: Gas pressure, mass and inertia of

the piston, piston skirt geometry and stiffness, lubrication

condition between piston and liner, running clearance,

damping effect of the ring pack, pin and crankshaft offset

Primary Motion Secondary Motion Tertiary Motion


NUMERICAL INVESTIGATION IN PISTON NOISE

Measured or Pre-

calculated Transient

Gas Pressure

3D FEM

Piston

Measured Liner

Profile (Cold

Conditions)

Calculated

Thermal

Deviation

Frequency

Structural response on

Measurement Locations

(for Validation)

Acce

lera

tio

n

MBD ModelApproach:

• Multi-body dynamic

• Flexible structures for engine model and crank train

• 3D piston model

• Elasto-hydrodynamic piston-linear surface contact (mixed lubrication)

EHD piston-

linear contact

Piston Dynamics

and Impact

Analysis


RESULT EVALUATION OF SIMULATION AND EXPERIMENT

1496_Fiat_Piston_Slap_Time\1496_Fiat_Piston_Slap_KS Time 02.vas_fly Page - 1500 Time 100%thomanns - 25.07.2012 / 14:50:34

Project:

Measurement:

Testsite:

Condition:

FIAT PISTON SLAP (Giulietta 1.6 JTDM)

Structural Vibration Analysis

Acoustic Chassis Dynamometer

1500 rpm - 100 % Load

v122_1 Cylinder block lhs cyl. 4 top

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

Baseline Condition

v122_2 Cylinder block rhs cyl. 4 top v122_3 Cylinder block rhs cyl. 4 bottom

v122_4 Cylinder block rhs cyl. 3 mid

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

v122_5 Cylinder block rhs cyl. 3 bottom v122_6 Cylinder block lhs cyl. 3 mid

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e v122_7 Cylinder block lhs cyl. 3 bottom v122_9 Cylinder block lhs cyl. 3 top v122_10 Cylinder block lhs cyl. 3 l iner mid

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

0 120 240 360 480 600 720Crank Angle - deg

-900

-600

-300

0

300

600

900

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e v122_11 Cylinder block rhs cyl. 3 liner mid v122_12 Cylinder block lhs cyl. 4 l iner mid

0 120 240 360 480 600 720Crank Angle - deg

-900

-600

-300

0

300

600

900A

ccele

ratio

n - m/s²(Lin

ear)

Spitz

e

0 120 240 360 480 600 720Crank Angle - deg

0

3

6

9

12

Pre

ssure

- M

Pa(

Lin

ear)

Spitz

e

Cylinder 1

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ratio

n - m/s²(Lin

ear)

Spitz

e

31

32

33

3

4

41

42

Cyl #3 Cyl #4Cyl #3 Cyl #4

Root Cause Identification:

Evaluation of structural response

at identical positions

Development of a „piston slap

index“

Acce

lera

tio

n [m

/s2

]

Bad Good

I4 2500rpm / motored condition

Identical Evaluation Points

(Simulation (Approach #2) & Measurements)


PISTON NOISE EVALUATIONMETHODS AND INDICES

PNRI

Piston Noise

Response Index

General structure

borne noise

casescases

ExperimentSimulation / Approach

• Simulation of different piston variants (profile, clearance, pin offset) for various operating conditions

• EHD contact between piston skirt and liner

• Accelerations on outer engine surface up to 3.5 kHz considered

• Calculation of a Piston Noise Response Index (PNRI)


Crank Angle Based Piston Slap Evaluation of Filtered Vibration Signal

• Use direct acceleration signals, preferable taken from surface vibration in upper area of engine block

• Filter signal in frequency band 1 to 3.5 kHz

• Calculate rms value of filtered signal in critical time window (60° CA to 120° CA re firing TDC)

• This evaluation procedure is applicable for both, simulation and experiment in identical way, and therefore allows direct comparison.

definition of a „Piston Slap

Index“, characterizing piston

slap effect on engine noise

110501070

5010

toandto

to

SlapAccrms

AccrmsF

PISTON NOISE RESPONSE INDEX PNRI

Apply normalization

1496_Fiat_Piston_Slap_Time\1496_Fiat_Piston_Slap_KS Time 02.vas_fly Page - 1500 Time 100%thomanns - 25.07.2012 / 14:50:34

Project:

Measurement:

Testsite:

Condition:

FIAT PISTON SLAP (Giulietta 1.6 JTDM)

Structural Vibration Analysis

Acoustic Chassis Dynamometer

1500 rpm - 100 % Load

v122_1 Cylinder block lhs cyl. 4 top

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear)

Spitze

Baseline Condition

v122_2 Cylinder block rhs cyl. 4 top v122_3 Cylinder block rhs cyl. 4 bottom

v122_4 Cylinder block rhs cyl. 3 mid

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear )

Spitze

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear)

Spitze

v122_5 Cylinder block rhs cyl. 3 bottom v122_6 Cylinder block lhs cyl. 3 mid

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear)

Spitze

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear )

Spitze

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear)

Spitze v122_7 Cylinder block lhs cyl. 3 bottom v122_9 Cylinder block lhs cyl. 3 top v122_10 Cylinder block lhs cyl. 3 l iner mid

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear)

Spitze

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear )

Spitze

0 120 240 360 480 600 720Crank Angle - deg

-900

-600

-300

0

300

600

900

Accele

ration

- m/s²(Lin

ear)

Spitze v122_11 Cylinder block rhs cyl. 3 liner mid v122_12 Cylinder block lhs cyl. 4 l iner mid

0 120 240 360 480 600 720Crank Angle - deg

-900

-600

-300

0

300

600

900

Accele

ration

- m/s²(Lin

ear)

Spitze

0 120 240 360 480 600 720Crank Angle - deg

0

3

6

9

12

Pre

ssure

- M

Pa(

Lin

ear)

Spitze

Cylinder 1

0 120 240 360 480 600 720Crank Angle - deg

-600

-400

-200

0

200

400

600

Accele

ration

- m/s²(Lin

ear)

Spitze

Accele

ration

[m

/s2]

Isolate effect of other cylinders

Identify /

isolate piston

induced noise

index


0 (idle) 0.3 0.66 1 (WOT)

load

„noisy“

„silent“2500rpm

1000rpm

0 (idle) 0.3 0.66 1 (WOT)

load

1000rpm

PISTON NOISE RESPONSE INDEX PNRIEXAMPLE

Measurement Simulation

I4 Gasoline Engine 2.5 liters / 2 Design Variants:

Baseline (“noisy” piston)

„Silent“ low running clearance

Different load cases idle and part load

2 engine speeds

Warm engine condition (80degC CWT)

Good agreement

between simulation and

measurement

„noisy“

„silent“

2500rpm

1000rpm

2500rpm

2500rpm

1000rpm


• Introduction






CONTENT


Main Applications

Gear Noise (Rattle, Whine,

Hammering)

Drive Line Vibrations

Low and High Frequency Effects

Stationary and Non-Stationary

Operating Conditions (Run-up, Tip-

in / Back-out, Clutch Activation)Frequency [Hz]

Shuffle

Clonk

Boom

Chatter

Rattle

Whine

Whoop

1 10 100 1000 10000

Shudder

Humming

Excitation Noise

Gear Whine

Prediction

Gear Rattle

Prediction

UNDERSTAND NVH-PHENOMENA IN TRANSMISSIONS AND DRIVE LINES


TYPICAL TRANSMISSION NVH PROBLEMS

Gear Rattle(unloaded gear rattle)

Gear Whine(singing, whistle)

Heartbeat Noise(harshness)

Engine-Transmission Interaction

Target: A common model approach depicting all phenomena


NVH SIMULATION OF TRANSMISSIONSGEAR RATTLE / DEFINITION AND CAUSE

Torque Flow

Loose gears

– unloaded

gears

Repeated impacts (contact change between driving/backlash flank) caused by movement of free parts (loose gears, synchronizer rings) within their active backlash

Important driver is torque fluctuation from engine

Moderate impacts result in a broad band excitation of the surrounding structures

Rattle

Gear Rattle


‚Rattle‘

Mdrag

ɪ

oil

Oil mist

Drag Torque / Oil Resistance

Torque Fluctuation

Housing FlexibilityShaft Flexibility

Roller Bearings

Damping in BacklashGear Contact Model

Backlash

EHL

Friction

Transfer

GEAR RATTLE - INFLUENCES AND REQUIREMENTS FOR SIMULATION

DMF

Torque Converter

Clutch

Pendulum Damper

Torque Isolation


GEAR RATTLE OF AN DIESEL ENGINE GEARBOX

Without Speed

Fluctuation

With Speed

Fluctuation

Gear Rattle

Measurements:

Measured with and without

speed fluctuations

influence on rattle clearly

visible

Simulation:

A calculated response at

gearbox housing shows

same speed and frequency

range where gear rattle

noise phenomena occurs

No gear whine noise since

tooth mesh stiffness

assumed as constant.

No gear rattle w/o

speed fluctuation


NVH SIMULATION OF TRANSMISSIONSGEAR WHINE / DEFINITION AND CAUSE

Torque Flow

Caused by periodic fluctuations in gear mesh (Transmission Error) due to

Geometrical insufficiencies (e.g. manufacturing inaccuracies, tolerances)

Elastic deflections under load

Manifested as a narrow banded, tonal noise at meshing frequency + harmonics and modulation

Engaged

gears

Gear Whine

mesh stiffness variation

number of teeth in contact


TRANSMISSION ACOUSTIC SIMULATIONGEAR WHINE

1st gear mesh order

2nd gear mesh order

(first harmonic)

fe

fe- fl

fl

Frequency

Vib

ratio

n fe+ fl

Main torsional frequency of crank

train (low order); e.g. 0-300Hz

Main meshing

frequencyModulated

frequencies

Manifested as a narrow banded (=tonal) noise

Engagement (main meshing) frequency (fe) +

Harmonics + Sidebands (modulation)

Annoying character

Critical when amplified by natural frequencies of

transferring / responding structures (e.g.

gearbox housing)


GEAR WHINEINFLUENCES AND REQUIREMENTS

‚Whine‘

edge loading

w/ lead crowning

Housing Flexibility

Shaft Flexibility

Roller Bearings

Friction

Transfer

Tooth Corrections and

Modifications

change of

backlash,

contact point

and contact

stiffness

Change of contact stiffness

Misalignment and

edge loading effects

Gear Contact Model

Full-elastic Gear Wheel Body

Real profile

3D Multi-flank contact


3rd

Gear

(z1/z2=36/45)

3000 rpm

1800Hz=

36th

Order

(1st meshing)

2nd

Order

(engine)

72th

Order

(2nd meshing)

1800 Hz = 36th Order

(1st meshing)

1800 Hz = 36th1785 Hz

1785 Hz

1815 Hz

1815 Hz

1800 Hz = 36th

1800 Hz =

1st Meshing

Order

Sideband

(36 + 2)th

Sideband

(36 – 2)th

GEAR WHINE TRANSFER - FROM GEAR MESH EXCITATION TO SOUND PRESSURE


Reduction transmissions of airplanes (e.g. turboprops)

Transmissions of trains (bogies)

Industrial and wind power transmissions

Axle transmissions (e.g. trucks, busses, construction)

Transmissions in electric drives

Picture reference: AVL or examples from internet

APPLICATION AREAS

The herein discussed approach and methodology are generic and applicable to all types of transmissions

Transmissions of tractors and construction equipment

Automotive – passenger car & trucks (MT, AMT, AT, DCT, CVT) & electrification

Simple two or multiple step transfer gear boxes


EXAMPLE TRANSMISSION NVHTRACTOR APPLICATION GEAR WHINE

Torque Flow

Simulation Model

MicrophonPosition

Dynamic Transmission Error

“bad”“good” – higher total nominal

Contact Ratio due to higher

overlap

dyn.

transm

issio

n e

rror

[mm

]

Mic 5

Mic 6


EXAMPLE TRANSMISSION NVHTRACTOR APPLICATION GEAR WHINE

Torque Flow

Simulation Model

MicrophonPosition

Dynamic Transmission Error

“bad”“good” – higher total nominal

Contact Ratio due to higher

overlap

dyn.

transm

issio

n e

rror

[mm

]

Mic 5

Mic 6

„SOL1 / good” „SOL 2 / bad”

SPL Sound Pressure Level [dB]


EXAMPLE TRANSMISSION NVHBUS REAR AXLE GEAR WHINE

Differential with

Hypoid Gear

Reduction at Side Shafts by

Planetary Gear Stages

Simulation Model


EXAMPLE TRANSMISSION NVHBUS REAR AXLE GEAR WHINE

Surface Velocity

Level [dB]

Sound Pressure

Level [dB]

1800 rpm / 3rd Octave Band 1250Hz Simulated Noise

Mic. 1

1m

Mic.1

1150 rpm

Mic.1

1800 rpm

Mic.1

2600 rpm

Gear whine

orders


• Introduction






CONTENT


Simulation Model (Multi-body dynamics)

Max. Angle Motion

of Tensioner Arm

ΔF Fast-Slow

Fo

rce

[N

]

High Force

Time [s]Time [s]

An

gle

[d

eg

]BELT DRIVEN STARTER-GENERATOR (BSG)BELT DYNAMICS DURING ENGINE START

Wheel

WheelSA

GearbxEngine

Durability Issues at

Crankshaft Front End

Time [s]

To

rqu

e [

Nm

]

Starter-Alternator Torque

Different Start-Ramps


FULL ELECTRIC DRIVELINEELECTRICAL AND MECHANICAL NOISE


ELECTRO-MAGNETIC EXCITATION AND TRANSFER TO MECHANICAL SYSTEM

FEM magnetic fieldRadial, tangential & bearing

forces mapped to FEM

(frequency domain).

Ripple torque Multi-body Dynamic

Driveline, whine, etc.

Export excitation in

frequency domain

Coupled simulation excitations

in frequency domain (forced

response analysis)

Torque and bearing forces to MBS,

calculate eccentricity

Ele

ctr

ical N

ois

e

Mech

an

ical N

ois

e

PWM Harmonics

0

-20

-40

-60

20

40

60

Isa Isb Isc

0.3 0.32 0.34 0.36 0.38 0.4

Time (s)

0

20

40

60

80

100

Tem_IM4

Electrical + Mechanical


Electromagnetic excitation Electromagnetic excitation

+ Mechanical

ELECTRICAL AND MECHANICAL NOISE OF FULL ELECTRIC DRIVELINE


• Introduction






CONTENT


• Complete powertrain models can be used in early development phase to predict complex NVH phenomena

• Simulation of the entire acoustic function chain with detailed physics provides the ability to understand cause and effect

The importance of considering and simulating transmission NVH within the entire development process increases by new requirements for efficiency and electrification

For many phenomena, it is important to consider transmission NVH simulation also in conjunction with the engine and powertrain

SUMMARY AND OUTLOOK

Further potential can be found in:

Further refinement of the models (e.g. damping, synchronization / shifting maneuvers, beveloid-and hypoid gears) and increase accuracy

Electro-mechanical interaction - effect of magnetic excitation and control

Acceleration of the process lead time

Extend and enhance interaction and combination with measurements (e.g. interior noise prediction)

Meaningful assessment and subjective evaluation directly from the simulation

powertrain nvh analysis - nvhskeylab.com

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