diseal engine

8/8/2019 Diseal Engine

1/33

Roger Krieger, GM R&D Center

THE AUTOMOTIVE DIESEL ENGINETHE AUTOMOTIVE DIESEL ENGINE

Roger B. Krieger

Powertrain Systems Research LaboratoryGM R&D CENTER

(Retired)

Adjunct Professor Engine Research Center

University of Wisconsin

Michigan State UniversityMichigan State University

College of EngineeringCollege of Engineering

Fall 2007 - ME 444


2/33


Diesel HistoryDiesel History


3/33


Lecture OutlineLecture Outline

Overview Combustion systems

Fuel injection systems

Fuel characteristics

Performance issues

Emissions control

Summary & future trends


4/33


The Diesel EngineThe Diesel Engine

.... an internal combustion engine in

which air is compressed to a temperaturesufficiently high to ignite fuel injected

into the cylinder where the combustion

actuates a piston.

Websters Dictionary


5/33


Diesel CombustionDiesel Combustion

Fuel sprayed in cylinder near TDC

Atomization, vaporization & mixing delayignition

Ignition occurs wherever conditions right

Combustion rate controlled by injectioncharacteristics (injection rate, spray angle,

injection pressure, nozzle size and shape),

chamber shape, mixture motion, & turbulence Glow plug may be used to aid cold starting

Power output controlled only by amount of fuel

injected


6/33



7/33Roger Krieger, GM R&D Center


9/33



Typical DI ChambersTypical DI Chambers

Heavy duty - 4-valve,

central injector, low swirl,

wide shallow bowlLight duty - 4-valves, central

vertical injector, high swirl,

deep narrow bowl

Spray Outline



Overview

Combustion systems



Performance issues

Pressure-volume comparisons

Emissions control





Fuel Injection SystemsFuel Injection Systems

Electronic distributor pump

Electronic unit injector (EUI)

High-pressure common rail



Electronic Distributor PumpElectronic Distributor Pump



Electronic Unit Injector (EUI)Electronic Unit Injector (EUI)



High-Pressure Common RailHigh-Pressure Common Rail

High-Pressure Pump

ECU

Fuel

Return toTank

Common Rail

Injectors

Spill

Control

Valve



Overview

Combustion systems



Performance issues

Emissions control





Fuel CharacteristicsFuel CharacteristicsFuel Property Diesel Gasoline Effect

Cetane High Low Self ignitability

Octane Low High Non self ignitability

Volatility Low High Vapor emissions

Energy/Gal 1.12xBase Base Miles per gallon

Sulfur (now) ~350 ppm ~350 ppm Particulates,catalyst poisoning

Sulfur

(future)



Overview

Combustion systems

Fuel injection systems Fuel characteristics

Performance issues

Emissions control





MAXIMUM SPECIFIC POWER & BM

COMPARISONGASOLINE vs DIESEL

0

5

10

15

20

25

30

35

40

45

50

0 1000 2000 3000 4000 5000 6000 7000

SPEED, r/mi

POWER,k

W/L&

BMEP,

bar

BMEP-GAS

POWER-GAS

POWER-DIESEL

BMEP-DIESEL


20/33


COMPARISON OF FUEL CONSUMPTIONDIESEL & GASOLINE @ 2500 r/min

BSFC vs BMEP

150

200

250

300

350

400

450

500

550

600

0 2 4 6 8 10 12 14 16

BMEP, bar

BSFC,g/kWh

Gasoline

DI-Diesel

P V Di


21/33


P-V DiagramsP-V Diagrams


22/33


BoostingBoosting

Most diesels boosted (i.e., turbocharged)

Boosting helps power & torque

Boosting helps fuel consumption Boosting facilitates torque curve shaping

Boosting helps relative package size

Boosting increases cost but is good value


23/33


Boosting SystemsBoosting Systems

Current Technologies

Waste-gate turbocharger

Variable nozzle turbine turbochargerFuture Technologies

Two-stage turbocharging systems

Electric motor driven compressor,turbine, or both

Dual range compressors with one turbine


24/33





Performance issues

Emissions control




25/33


PowerDensity

Efficiency

Driveability

Progression in European PassengerProgression in European PassengerCar Diesel Emissions StandardsCar Diesel Emissions Standards

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 0.2 0.4 0.6 0.8 1 1.2

HC + NOx (g/km)

Particulates

(g/km) EURO I (1992)

EURO II -- DI (1996)

EURO III (2000)

EURO IV (2005)

EURO V (2009)

PowerDensity

Efficiency

Driveability


26/33


Exhaust Emission ControlExhaust Emission Control

HC (challenging)

Nozzle design

Catalyst (HC & exhaust odor)

CO (less challenging)

NOx(most challenging)

Injection timing

EGR

Injection rate shaping

Lean NOx catalyst

Combustion chamber shape optimization


27/33


Exhaust Emission ControlExhaust Emission Control

Particulates (very challenging) Chamber symmetry and shape

Injection characteristics (mixing rates)

Oil control

Catalyst (soluble fraction) Particulate trap

Odor (oxidation catalyst)

Co2(global warming)


28/33


Combustion DevelopmentCombustion Development

Optimize piston bowl shape to control

spray/airflow interaction Increase combustion rate

FUEL SPRAY FUEL VAPOR

SOOT CLOUD

FUEL FILM ON WALLSWIRL DIRECTION

SPRAY ON BOWL LIP

REVERSE SQUISH


29/33


Low-Temperature CombustionLow-Temperature Combustion

Toward LTC

ConventionalCombustion

Low NOx/Soot

Region

HC/CO

1000 1400 1800 2200 2600 3000

Temperature, K

EquivalenceRatio

0

1

2

3

4

5

6


30/33


Exhaust AftertreatmentExhaust Aftertreatment

DOC

ECU

VAPORIZER

TEMPERATURE

SENSORSPRESSURE DROP

SENSOR

PARTICLE

FILTERDOC

AIR FLOWMETERTHROTTLE

EGR

VALVE

NOx

DEVICE


31/33






Performance issues

Emissions control



32/33


Summary Diesel EnginesSummary Diesel Engines

Advantages: Efficiency (most efficient prime mover) Emissions (low CO, CO2, good durability)

Very high torque and performance

Disadvantages: Emissions (more challenging to control

NOx, particulates) Higher cost

Heavier

Noise (more challenging to make quiet)

F t T dF t T d


33/33

Future TrendsFuture Trends

Factors Global warming (favors diesel)

Energy resources (favors diesel)

Government policy (low fuel tax unfavorable for diesel)

USA Truck use increasing

Car use discouraged by low fuel tax

Higher recent fuel prices and higher CAFE threat drivingsome introduction

Europe New technology (4-valve DI, common-rail injection,

particulate traps)

Diesel car sales up dramatically (currently 50% of new carmarket)

Being marketed as performance engine

diseal engine

Documents