9 LMS Pete Schaldenbrand

Peter Schaldenbrand, LMS North America2008 Testing Expo

Understanding Fuel Economy and NVH trade-offs with Effective Use of Rotating Machinery AnalysisLMS International

2 copyright LMS International - 2005

Outline

Engine design challenges and NVH trends

The NVH testing process

Advanced NVH engine analysis techniques:Order trackingCrank angle analysisTorsional vibration analysis

Conclusion


Engine Development Challenges

High fuel efficiency / powerBetter combustionLower size/weight

Improve durability Structural integrity

Compliance to legislationExhaust emissionsNoise legislation

ComfortNVHDrivability

Engine Design Polygon

Cost

Noise & Vibration

Drivability

DurabilityEmissions

Power

Emissions and Power are priority design drivers

Is expected to be designed for

infinite life

Are differentiators (and market entry requirements for low end engines)

Investments driven by Emissions and Fuel Consumption


NVH Calibration …while meeting emissions and fuel consumption targets

Noise:Certification to PBNSound quality

VibrationsRelate to mechanical phenomena

• Piston dynamics• Valve dynamics• Torsional vibrations

Relate to Combustion process• Combustion profile• Misfire

Durability testingEndurance test of componentsInfinite life check

Simultaneously taking into account:Controls and ECU strategiesTransmission and drivability objectivesCore engine fuel consumption, performance and emisions objectives

Noise

Transmission

Electronics

DurabilityVibrations

Core engineSpecificaitions


NVH basic modelReceiver = Transmission x Sources

Test Process Flow

OperationalPerformance

ReceiverStructuralProperties

Operating Loads

Transmission Sources= x

▪ Noise▪ Vibration ▪ Stress▪ Fatigue

▪ Modal characterisitcs▪ Intertia/Mass▪ Fluid (Air) Properties

▪ Forces ▪ Moments

= xNoise

Structural Modes

CombustionMechanical dyn.Fluids flowUnbalance…


Powertrain NVHMechanical & combustion noise, structure & air-borne

Air

Bor

neA

ir B

orne

Stru

ctur

e B

orne

Stru

ctur

e B

orne

ExcitationExcitation

IsolationIsolation TransferTransfer VehicleVehicleInterior NoiseInterior Noise

ΣΣ

Acc

elSP

LSP

LA

ccel

harmonic pattern

Acc

el

dB/N

dB

discrete frequencies

SPL

SPL

chassis dynamics

tran

sfer

func

tion

dB/d

B

2nd order excitation

spectrum shape

discrete frequencies

2nd order excitation

Body Noise TF

level & linearity

spectrum shape

mount character-

isticsDyn

amic

st

iffne

ss

Trans-mission

Loss

harmonic pattern

Acc

el


Engine Testing Process Methodology

Phase 1: Benchmark current statusHarmonic analysis – ODS Psycho-acoustics – Source localisation

Phase 2: Engineering cycle - DiagnosisContribution of sources to receiverStructural characteristics Mechanical dynamicsCombustion analysis

Phase 3: Engineering cycle – Evaluation of alternativesEvaluate contributions (sources and paths)Evaluate structural modificationsEvaluate mechanical changesEvaluate combustion changes

Phase 4: Validation of design modificationSame tools as in phase 1


Fast identification of harmful noise & vibrationsOrder tracking

Traditional approach – gives good overview of NVH issuesNo need for high pulse per revolution tacho signalIdentify normal and abnormal engine vibrations in different operating conditionsDifferentiate between Orders and Resonances

0 .0 0 1 5 0 0 .0 0H zC y lin d e r s :1 : - Y ( C H 8 )

1 8 0 0 .0 0

2 9 0 0 .0 0

rpm

Tach

o1 (T

1)

3 7 .3 e - 9

3 2 6 e - 6

Ampl

itude

g

4 620 .5

1 8

1 3 3 4

A u to Po w e r C y lin d e r s :1 : - Y W F 1 1 0 [1 8 0 0 .9 - 2 8 9 1 .3 r p m ]


Crank-angle analysis - Relating to root-causes Combustion N&V

Relate measurements to crank angle

Combustion pressure profile

Analyse combustion-stabilityEngine knockNon-or irregular ignition

Synchronised measurement of ECU parameters Cross-check modification impacts on combustion performance (P-V, IMEP)Immediate estimation on sound characteristics based on combustion pressure and structural characteristics

141.25 22387.21Octave 1/3

Hz

-50.00

0.00

dBg

-50.00

0.00

dB g

A L

/

Engine/eartransfer function

Combustion P 1/3 Octave content Driver ear noise


Crank-angle analysis - Relating to root-causes Mechanical N&V

Investigate irregular impacts and timing Piston slap, croak, ticking,Valve dynamicsTorsional vibrations

RequirementsAngle domain1-720 pulses per rev

Relate measurements to crank angle


Example of piston mechanical noise

RattlingSpeed range: 2500-3500 rpmAngle range: -2 to 3 degreesLoad range: 20-40%Sound: clear metallic patteringFreq range: 2.5 - 5 kHz

CroakingSpeed range: 1000-2200 rpm Angle range: 0 – 30 degreesLoad range: 10-50%Sound: Dull, diesel like hollow soundFreq range: 1.2 - 2.5 kHz


Parallel frequency and angle domain analysisGated processing

Wavelet or Short time Fourier transformRelating angle position events to frequency contentCylinder to cylinder comparisonCycle to cycle comparison

Gate 1: After TDC Gate 2: Before spark

Tracked evolution of maximum and

angle of max versus RPM


Valve dynamics

Use laser vibrometer or induction probes for displacementAccelerometers, Mics, and strainHigh speed encoder (e.g. 720 ppr)Motored operation

Track design target metrics:valve opening durationvalve lift, velocity, acceleration vs. time or crank anglefloat (measured vs. theoretical & float vs. angle)bounce (measured vs. theoretical & bounce vs. angle)angular position for dynamic valve openangular position for dynamic valve closepre-lift lossapparent pre-lift losskinematic closing lifttotal lift lossvalve seating velocity


Torsional vibrationsBelts & pulleys analysis, Gear train rattle & whine, Transmission error

Multiple tacho channelsOnline torsional vibration calculationOnline calculations:

belt slip %stretchtransmission errorbelt/chain linear displacement, velocity, accelerationshaft angular displacement, velocity, accelerationshaft relative angular displacement, velocity, acceleration (between 2 shafts)

Gears:Visualisation of angular looseness / clearance between gearsGear flank testing/certificationTransmission error % calculation

Torsional vibrations if not managed can lead tohigher fuel consumption and decreases in performance

as well as rattle & whine NVH problems


Predictive analysis of Engine/Driveline Torsional VibrationModel and Verification

Torsional vibration in driveline with automatic gearbox will create increased fuel

consumption and lower comfort

Full engine/driveline was Full engine/driveline was modeledmodeled for predictive for predictive

analysis analysis using MBSusing MBS

Verification measurementsVerification measurements were were

done to validate approachdone to validate approach


Predictive analysis of Engine/Driveline Torsional VibrationVerification Measurements

•• 4 microphone signals4 microphone signals•• 120 acceleration 120 acceleration

signalssignals•• 9 9 torsionaltorsional vibration vibration

signalssignals

33rdrd order order torsionaltorsional vibration at flywheel vibration at flywheel measured vs. predictedmeasured vs. predicted

Campbell Campbell torsionaltorsional vibration pulleyvibration pulley


ConclusionFollowing the Green trend

“Eco-friendly” market requirements are driving major engineering challenges

Clean sheet redesign or improvement of existing platformsIncreasing need for efficient multi-attribute testing

Systematic engine testing with Advanced NVH analysis technology platforms like LMS Test.Labprovide a means to accurately capture and understand the processes influencing fuel consumption as well as NVH

Order tracking for overview pictureCrank-angle analysis for multiple root-causes identificationTorsional vibration measurement for gears, blets, transmission dynamics

Noise

Transmission

Electronics

DurabilityVibrations

Core engine

Engineering challenges Complex systems Multi-attribute Testing systems

Systematic/ Efficient methodologies

Peter Schaldenbrand, LMS North America2008 Testing Expo

Thank you

Documents

9 LMS Pete Schaldenbrand