p&e development -jlr lecture 2011

Gasoline Base Engine Development for Performance and Fuel Economy

Matthew McAllister – Jaguar Land Rover Gasoline Engines

Birmingham University Lecture - 2011 1

Introduction


Introduction

Contents

• The Development Process

• Performance Theory

• Fuel Consumption Theory

• Development Tools


• Development Tools

• Summary

The Development Process




“How does base engine design & development fit into the company structure?”

Vehicle

Body&Exterior Chassis Interior Systems Powertrain Electrical


Systems Transmissions Base Engines

Design

Calibration

Development


Responsibilities

Engine Design

• Design components on CAD

• Manage all aspects of component delivery (suppliers, cost,

weight, manufacture, package)

Engine Development


Engine Development

• Manage all aspects of verifying design of components &

systems

• Focus on function and attributes


The System Engineering “V”

Vehicle Level

Start Job1


System Level

Component Level

Define Design Verify


System Engineering – DEFINE

• Set targets at customer level and then cascade down to component level

e.g. Customer level target: 0-60mph < 6.2sec

0-60mph time

Vehicle Aero Tractive Effort Vehicle Mass Traction

Vehicle Level

System Level


Vehicle Aero Tractive Effort Vehicle Mass Traction

T/M FDR T/M Efficiency Engine Torque

Displacement

Engine Technology

Compression Ratio

Int & Exh System

System Level

Sub-systemLevel

ComponentLevel


System Engineering - DESIGN

Design Guidelines

Corporate/Legal Requirements

Manufacturing Requirements

Recycling Requirements


Component Attribute Targets(from cascade)

Quality & Durability Targets

Cost & Weight Targets

Packaging Constraints New Design

Vehicle Level

Durability

Hot/Cold Climate

Performance/NVH

CAE

System Level


System Engineering – VERIFICATION


System Level

1-D Engine simulation

Engine dynamometer testing

NVH CAEComponent Level

Rig Testing

Component CAE (e.g.

FEA/CFD)


The System Engineering “V”

Vehicle Level

Start Job1


System Level

Component Level

Define Design Verify


Build Phases

1. Mule Demonstrator (often reworked/modified existing

hardware)

Design

Verify

ManufactureOptimise


hardware)

2. Attribute Demonstrators (first dedicated prototypes, non

production process)

3. Confirmation Prototype (final prototypes, should be

production process & off production tool)

4. Production Verification (off production line at production

rate)

Base Engine P&E


Base Engine P&E

P&E Attributes

Engine P&E

Incorporates:

•Engine Performance

•Engine Fuel Consumption (Economy)

•Engine Emissions


P&E typically considered separate to Mechanical or NVH

Development and in some companies part of Calibration

department

P&E Attributes

Performance & Fuel Consumption Challenge


Source: COMMISSION OF THE EUROPEAN COMMUNITIES - SEC(2007) 1723

Performance Theory

Possible Scenario

• Existing engine with following specification:

-2.6L V6 – 180bhp

-Fixed intake manifold

-Intake variable cam timing

-10:1 compression ratio


-10:1 compression ratio

-6000rev/min peak power speed

• What is required to increase power to 200bhp without

increasing displacement?

Performance Theory

2

)/( AFQVNPower

airHVdvolumetricsionfuelconver ××××××=

ρηη


2

Performance Theory

2

)/( AFQVNPower

airHVdvolumetricsionfuelconver ××××××=

ρηη

Air Mass TrappedVolumetric Efficiency

(manifold & port ∆P, tuning)

Intake System LossesFuel-Air Ratio


2

Thermal efficiencyHeat losses

Mechanical losses

Pumping losses

Mixing

Ignition efficiency

Engine Speed Fuel EnergyDisplacement

Performance Theory

Displacement

• Power ~ proportional to displacement

• Often easiest way of achieving power

increase but increases fuel economy,

engine mass and package requirements

• Can limit maximum engine speeds0

100

200

300

400

500

600

700

0 1 2 3 4 5 6 7 8Displacement [litres]

Po

we

r [h

p]


• Can limit maximum engine speeds

Engine Speed• Power is “rate of doing work”, therefore

proportional to engine speed

• Requires changes to engine design to

ensure volumetric efficiency does not drop

• Can involve significant costs to achieve

durability

Displacement [litres]European Gasoline Engines 2007

0

20

40

60

80

100

120

4000 5000 6000 7000 8000

Max Power Speed [rev/min]

Sp

ecific

Po

we

r [h

p/L

]

European Gasoline Engines 2007

Performance Theory

Intake lossesPerformance vs Intake Loss

194

196

198

200

202

204

206

208

Pow

er

[bh

p]

Hig

h p

erf

orm

an

ce

typ

ical fa

mily

ca

r


• Minimize losses – rule of thumb: 1.2% power / 10mbar

intake ∆P increase

• Minimize detrimental tuning effects as a result of layout

AIS CFD 194

10 20 30 40 50 60

Intake Loss [mbar]

Hig

h p

erf

orm

an

ce

Performance Theory

Volumetric Efficiency - ∆ ∆ ∆ ∆P

• Minimize pressure losses (throttle

sizing, manifold runner R/D,

manifold detail design, managing

interfaces, surface finish, port

design, valve design, valve seat

design)

RD

R/D


design)

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.1 0.2 0.3 0.4 0.5

Valve Lift/Diameter

Flo

w C

oe

ffic

ien

t

Port flowThrottle ∆P (CFD)

Performance Theory

Volumetric Efficiency – Intake Tuning

• Objective: maximise mass of air trapped at specific

speeds or across speed range by harnessing wave and

inertial tuning effectsPLENUM

Runner

Cylinder

Depression Wave

Reflected Pressure Wave

• WAVE tuning –

dependent on intake cam

period & runner length


PLENUM

Runner

Cylinder

Reflected Pressure Wave

period & runner length

• Inertia tuning – inertia of air column in runner/port continues

charging process past piston BDC - dependent on runner

diameter, volume and intake valve closing time

Performance Theory

110%

130%

150%V

olu

metr

ic E

ffic

ien

cy [

%]

150

200

250

To

rqu

e [

Nm

]

Typical production I4 performance curve…

Closed Valve Tuning


50%

70%

90%

0 1000 2000 3000 4000 5000 6000 7000

Engine Speed [rev/min]

Vo

lum

etr

ic E

ffic

ien

cy [

%]

0

50

100 To

rqu

e [

Nm

]

Primary tuning

Secondary Tuning

Performance Theory

Volumetric Efficiency – Optimum Runner Lengths

• Theoretical optimum runner length vs engine speed:

1500

2000

2500

Op

tim

um

Ru

nne

r L

eng

th [m

m]

Intake Length

Exhaust Length


0

500

1000

1500

2000 3000 4000 5000 6000 7000


Op

tim

um

Ru

nne

r L

eng

th [m

m]

Performance Theory

Volumetric Efficiency – Exhaust Tuning

• Objective: maximise extraction of residuals by harnessing

wave tuning effects in exhaust / minimise negative tuning

effects between cylinders

• Limited opportunity in modern passenger vehicles as

design is dominated by emissions requirements (catalyst)

and under-bonnet package Log Manifold


and under-bonnet package

Cylinder

Collector

Blow-down pulse

Cylinder

Collector

Reflected extraction wave

Log Manifold

4:2:1 Manifold

Performance Theory

Fuel Air Ratio (1/AFR)

• Maximum performance at ~12:1-13:1 AFR (Power

Enrichment)

• AFR settings at higher engine speeds generally dictated

by component (e.g. exhaust valves, turbine, catalyst)

protection requirements


Engine speed

Load

λ=1 (AFR~14.6:1)

(for max. catalyst eff.)

PE - AFR~13:1

-4%

-3%

-2%

-1%

0%

10 11 12 13 14 15AFR

% P

erf

orm

ance d

egra

datio

n

Performance Theory

Thermal Efficiency

Friction:

• At max power speed friction is approximately 15% of brake power

• 10% reduction in friction � 1.5% increase in power

• Not only contact friction – need to Typical SI engine heat

balance at peak power


• Not only contact friction – need to consider windage / inter-bay breathing

Heat losses:

• At max power ~22% of fuel energy lost in heat transfer to air/oil/coolant

• 10% reduction in heat loss � 8% increase in power (!)

Brake power

28%

Exhaust

enthalpy

50%

Coolant/oil

15%

Ambient

7%

balance at peak power

Performance Theory

Thermal Efficiency

Exhaust Back Pressure – 3 effects:

1.Increases pumping work to expel charge

2.Reduces amount of fresh charge induced

3.Increases knock sensitivity (ignition retard from optimum)

Performance vs Exhaust Back Pressure208


194

196

198

200

202

204

206

208

200 300 400 500

Exhaust Back Pressure [mbar]

Po

wer

[bh

p]

Hig

h p

erf

orm

ance

fam

ily c

ar

Performance Theory

Thermal Efficiency

Ignition Efficiency:

• Objective – operate ignition

at MBT (Maximum advance for

Best Torque)

• Good resistance to 340

360

380

400

420

0102030

MBT DBL

To

rqu

e [N

m]


• Good resistance to

detonation (detail chamber

design, head cooling)

• Key parameters:

compression ratio & fuel RON

(trade-off with fuel economy)

0102030Ignition [°btdc]

Engine speed

Loa

d

WOT

Knock limited IGN MBT IGN

Engine speed

Loa

d

WOT

Knock limited IGN MBT IGN

Performance Theory

Robustness…

• It is not enough simply to demonstrate performance under

ideal homologation conditions (low temperature, high RON

fuel, best build condition)

• Also need to consider

worst case…


• Need to understand

sensitivities to these

parameters and ensure

adequate performance

under all conditions to

avoid customer

complaints

Performance Theory

Back to performance optimisation scenario …

• 200bhp = 11% increase

• Increasing engine speed to 6600rev/min at constant

volumetric efficiency would deliver ~10% = 198bhp

• Increasing compression ratio to 11:1 would deliver ~2-3% =

4bhp = 202bhp (providing engine is not knock limited)


4bhp = 202bhp (providing engine is not knock limited)

• To deliver good volumetric efficiency at higher engine

speed will require re-optimised runner length

• May need to consider variable geometry manifold to not

sacrifice too much low speed performance

Performance Theory


•2.6L, 180BHP

160

200

240

280

To

rqu

e [

Nm

]


0

40

80

120

160

1000 2000 3000 4000 5000 6000 7000


To

rqu

e [

Nm

]

BASELINE

Performance Theory


•2.6L, 198/202BHP – but poor driveability

160

200

240

280

To

rqu

e [

Nm

]

BASELINE


0

40

80

120

160

1000 2000 3000 4000 5000 6000 7000


To

rqu

e [

Nm

]

BASELINE

INCR ENG SPD

INCR CR

Performance Theory


•2.6L, 202BHP – Optimised Torque Curve

160

200

240

280

To

rqu

e [

Nm

]

BASELINE

INCR ENG SPD


0

40

80

120

160

1000 2000 3000 4000 5000 6000 7000


To

rqu

e [

Nm

]

INCR CR

TWIN STAGE

MANIFOLD

Fuel Consumption Theory

Fuel economy break-downLog P

Gross EfficiencyFuel required to generate GIMEP

Pumping work


Log P

Pumping work

PMEP

Log V

Net IMEP = GIMEP + PMEP (-ve)

BMEP = Net IMEP - FMEP

Pumping workFuel “lost” to pumping work

Friction workFuel “lost” to friction work

Brake work

induction

exhaust


Maximize Gross Efficiency (1)

• Maximize compression

ratio (trade-off with low

speed / low RON / high

air temp performance)-4%

-2%

0%

2%

4%

6%

8%

10%

9:1 10:1 11:1 12:1 13:1 14:1Compression Ratio

ch

an

ge

in

BS

FC

Theory

Reality


• Minimize heat transfer

(surface to volume ratio,

charge motion, coolant

temperature)

Compression Ratio

-3%

-2%

-1%0%

1%

2%

3%

0.90 0.95 1.00 1.05 1.10Bore/Stroke Ratio

Ch

an

ge

in

ηη ηηth

erm

al


Maximize Gross Efficiency (2)

• Ensure complete burn (good atomisation, complete mixing)

• Ensure optimum spark efficiency (resistance to knock, fast

burn, correct calibration)

40%

Incre

ase i

n F

uel

Co

nsu

mp

tio

n

MBT


0%

10%

20%

30%

0 10 20 30 40Ignition Timing [°btdc]

Incre

ase i

n F

uel

Co

nsu

mp

tio

n

MBT

(opt eff)


Minimize Pumping

Pumping Reduction Routes:

1.Charge dilution (stratified DI / lean

homogeneous / EGR)

2.Reduction of trapped volume (very

early or very late intake valve closing)

Log P

PMEP


3.“Down-sizing”

�With all these approaches the volume of trapped air is

reduced requiring the manifold pressure (MAP) to be raised,

i.e. throttle to be opened further, to recover the lost mass �This reduces the pumping work

Log V

Old MAP

New MAP


Dilution by air (Stratified Direct Injection)

Example: MB 3.5L V6 DI


• Significant fuel economy potential 5-15% depending on

engine size/application

• BUT major emissions compliance challenge involving

complex and expensive after-treatment system (maybe not

possible beyond EU5 in Europe and ever in US?)

• Benefit diminishes significantly for smaller engines


Reduction of trapped volume

Example – BMW Valvetronic


• Pumping benefit achieved by virtue of controlling load

(mass trapped) through variable valve lift/duration instead

of throttle

• Limited fuel economy benefit (2-5%) due to reduced

combustion efficiency - particularly at light load (effective

compression ratio reduced, poor charge motion)

• Expensive technology and major manufacturing challenge


Minimize Friction• Typical friction break-down vs engine speed for SI engine:

40%

60%

80%

100%F

ricti

on

Bre

ak-d

ow

nValvetrain

Coolant Pump +Unloaded Alternator

Oil pump

Piston group & con-rod


0%

20%

1000 2000 3000 4000 5000 6000


Fri

cti

on

Bre

ak-d

ow

n

Piston group & con-rodbearings

Crankshaft

• For drive-cycle fuel economy (below 3000rev/min) focus

should be on reduction of valvetrain and piston friction

• A 10% reduction in piston friction could reduce part load fuel

consumption by ~1%

1) Higher Compression Ratio (no knock limitation)


Based on fuel consumption theory just presented what are the two main reasons for the improved fuel consumption of Diesel vs. Gasoline engines?


2) Minimized pumping work (load control through level of dilution with air, qualitative vs. quantitative load control)

Compression Ratio

22.520.017.515.012.510.07.5

Diesel

Gasoline

Each symbol represents up to 3 observations.

Application of Fuel Consumption Theory


Application of Fuel Consumption Theory

Fuel Consumption – CO2 challenge for manufacturers

How to make vehicles that comply with the EU Legislative framework:

• From 2012 to 2019 a vehicle mass based CO2 limit will be applied to all new vehicles.

• How to address this in a cost effective manner, whilst maintaining key vehicle attributes?

Options available:

• Vehicle level optimisation for increased efficiency:


• Vehicle level optimisation for increased efficiency:

• Advances predominantly aimed at reducing weight and aerodynamic drag.

•Powertrain level:

• Mild or micro hybrid technologies.

• Full hybridisation.

• Technologies aimed at reduced friction, pumping and increased combustion efficiency.

�Gasoline engines downsizing and boosting – focus of our paper.

Fuel Consumption – Downsizing and Boosting

•Presented at IMechE Internal Combustion Engines: Performance, Fuel & Emissions Conference - Dec 09

•Paper title: Future gasoline engine downsizing technologies – C02 improvements and engine design considerations. Authors: M.J.McAllister & D.J.Buckley.

• Downsizing - The principle behind this approach is to de-throttle the engine to reduce pumping work by making the displacement and/or number of cylinders smaller.


• Boosting – provides a means of increasing the specific performance of the downsized engine, thus maintaining the power and torque of the engine it replaces, typically with a supercharger, turbocharger or combined boosting systems.

�� Gasoline engine downsizing and boosting offers manufacturers significant CO2 reductions without major vehicle modifications such as those required by full hybrid technologies.

Fuel Consumption – Challenges of downsizing

• Robust DI combustion system.

• An advanced boosting system.

• Emissions countermeasures.

• Effective integration of downsized engines with complementary CO2

reduction strategies.

• Refinement.

• Customer acceptance of smaller engines.


• Customer acceptance of smaller engines.

�� The above challenges are considerable due to competing

attributes. Customer acceptance is a problem that requires more

than just an engineering solution!

Fuel Consumption – CO2 benefits of engine downsizing

0

5

10

15

20

25

% C

O2 r

ed

uctio

n

SC

TC

4L V8

3.5L V6

3L V6

2.4L I42L I4

Deviation from the trend line is due to BMEP resolution in

the fuel map analysis


0

0% 10% 20% 30% 40% 50% 60% 70%

Level of Downsizing [%]

• For a >10% CO2 benefit a significant level of downsizing is necessary (35%) requiring a change in architecture, i.e. V6 vs. V8 or I4 vs. V6.

• A moderate level of downsizing (e.g. 4.5L SC vs. 5L NA) does not yield a meaningful CO2 benefit (<3%).

• Difference between boosting systems is small compared to overall downsizing effect so other factors will be decisive (e.g. transient response, emissions etc.).

P&E Development Tools


P&E Development Tools

Overview

P&E Specific Tools

Level Virtual Real

Vehicle • Vehicle performance and FE

simulation

• Drive cycle FE and emissions

testing

• Performance testing

Engine • 1-Dimensional Gas Exchange

Modelling

• Combustion Modelling

• Single-cylinder engine testing

• Multi-cylinder engine testing


• Combustion Modelling

Component • CFD flow modelling

• Friction modelling

• Flow bench testing

CAE

Steady State CFD – Port Flow

• Allows detailed “desktop” optimisation of port design for

flow / charge motion prior to evaluation on flow bench test

Pressure

Inlet


Ports

Bell MouthValve

Seats

Pressure Outlet

Chamber

& Tube

CAE

Steady State CFD – Intercooler Flow Distribution


CAE

1-D Simulation

• 1-D Simulation (Ricardo WAVE) used to analyze the

dynamics of pressure waves, mass flows, and energy

losses in the engine intake and exhaust

• Engine intake & exhaust geometry broken down into 1-

dimensional components (ducts and junctions)

• Mass, momentum and energy conservation equations


• Mass, momentum and energy conservation equations

solved for each sub-volume to obtain solution

• Used to predict key engine operating characteristics, e.g.

volumetric efficiency, torque, mass flows, etc.

CAE

WAVE 1-D model – SC V8

A-bank

Catalyst


Airbox

SC & IC

B-bank

Exhaust Manifold

B-Bank Exhaust System

CAE

WAVE 1-D vs Test Data CorrelationT

orq

ue

WAVE model

Test Data


1000 2000 3000 4000 5000 6000


To

rqu

e

CAE

Advantage of 1-D simulation

1. Time – possible to run multiple simulations 24/7

2. Cost – conducting engine testing is expensive (test facility, tester,

engineer, fuel, maintenance), 1-D simulation only requires 1 engineer and 1 PC

3. In-depth understanding – with 1-D simulation detailed

information of pressures, temperatures, mass flows, etc. is available


information of pressures, temperatures, mass flows, etc. is available throughout the engine and at every point in the cycle

Disadvantages

1. Need for correlation to existing test data

2. Model does not always behave like real engine

3. 1-D approximation of complex 3-D geometries

Testing

Engine Dynamometer

• Durability & functional testing

• Steady state & transient dynamometers

• High/low temperature capabilities


Testing

Typical dynamometer instrumentation

1. Thermocouples � e.g. coolant, oil, intake air temperature

2. Pressure transducers � e.g. oil gallery, boost pressure

3. Fuel flow (mass/volumetric) � used to infer air mass flow

4. Emissions analyser � O2, CO, CO2, HC, NOx

5. Smoke meter (Diesel, GDI)


6. Fluid flow meters � e.g. engine or intercooler coolant flow

7. Combustion analyser � used to measure cylinder

pressures and calculate IMEP, PMEP, burn data

8. EMS break out equipment � to control engine settings

9. Automated testing controller � to schedule automated

testing and interface with dyno & EMS

10. Knock monitoring equipment � audio/visual

Testing

Key Challenges

• Maximum utilisation of dynamometers – expensive

investment

• Efficient processing of (ever) increasing quantities of test

data – up to 250 data channels per test point

• Increased use of design of experiments and data

modelling


modelling

• Increased use of automated testing

• Increased awareness of the statistical nature of test data

Testing

Rapid Prototype Parts

> key technology in enabling

reduced development time

• SLA – Stereolithography

–3D CAD model is converted into a series of 2D slices (~0.1mm thick). Laser cures photosensitive resin in a tank layer by layer


photosensitive resin in a tank layer by layer

• Laser Sintering

–Similar principal to SLA but very thin layers of heat fusible powder are repeatedly deposited. Laser sinters the fresh powder to form a new layer.

• Applications: intake manifolds, air

induction systems, moulds for casting,

etc.

Summary


Summary

Summary

Overview

• Methodology used in vehicle/engine development –

System Engineering “V”

• Fundamental performance and fuel consumption theory

• Overview of tools used in development


Future Challenges

• Dramatic fuel consumption / CO2 reduction required

• More stringent emissions legislation

• Higher performance (?)

• Reduced development time

• Lower cost (?)

225 mph Bonneville Speed Record

BonnevilleMaster.mov


2010 Jaguar XK GT2


Thank You

p&e development -jlr lecture 2011

Documents