THE AUTOMOTIVE DIESEL ENGINE

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THE AUTOMOTIVE DIESEL ENGINE
Michigan State University College of
Engineering Fall 2007 - ME 444

• Roger B. Krieger
• Powertrain Systems Research Laboratory
• GM RD CENTER
• (Retired)
• Adjunct Professor Engine Research Center
• University of Wisconsin

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Diesel History
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Lecture Outline

• Overview
• Combustion systems
• Fuel injection systems
• Fuel characteristics
• Performance issues
• Emissions control
• Summary future trends

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The Diesel Engine
.... an internal combustion engine in which air
is compressed to a temperature sufficiently high
to ignite fuel injected into the cylinder where
the combustion actuates a piston.
Websters Dictionary
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Diesel Combustion

• Fuel sprayed in cylinder near TDC
• Atomization, vaporization mixing delay ignition
• Ignition occurs wherever conditions right
• Combustion rate controlled by injection
  characteristics (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

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Lecture Outline

• Overview
• Combustion systems
• Fuel injection systems
• Fuel characteristics
• Performance issues
• Emissions control
• Summary future trends

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Typical DI Chambers
Spray Outline
Heavy duty - 4-valve, central injector, low
swirl, wide shallow bowl
Light duty - 4-valves, central vertical injector,
high swirl, deep narrow bowl
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Lecture Outline

• Overview
• Combustion systems
• Fuel injection systems
• Fuel characteristics
• Performance issues
• Pressure-volume comparisons
• Emissions control
• Summary future trends

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Fuel Injection Systems

• Electronic distributor pump
• Electronic unit injector (EUI)
• High-pressure common rail

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Electronic Distributor Pump
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Electronic Unit Injector (EUI)
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High-Pressure Common Rail
Common Rail
Spill Control Valve
Injectors
Fuel Return to Tank
ECU
High-Pressure Pump
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Lecture Outline

• Overview
• Combustion systems
• Fuel injection systems
• Fuel characteristics
• Performance issues
• Emissions control
• Summary future trends

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Fuel Characteristics
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Lecture Outline

• Overview
• Combustion systems
• Fuel injection systems
• Fuel characteristics
• Performance issues
• Emissions control
• Summary future trends

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P-V Diagrams
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Boosting

• 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

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Boosting Systems

• Current Technologies
• Waste-gate turbocharger
• Variable nozzle turbine turbocharger
• Future Technologies
• Two-stage turbocharging systems
• Electric motor driven compressor, turbine, or
  both
• Dual range compressors with one turbine

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Lecture Outline

• Overview
• Combustion systems
• Fuel injection systems
• Fuel characteristics
• Performance issues
• Emissions control
• Summary future trends

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Progression in European Passenger Car Diesel
Emissions Standards
Efficiency
Power Density
Driveability
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Exhaust 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

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Exhaust 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)

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Combustion Development

• Optimize piston bowl shape to control
  spray/airflow interaction
• Increase combustion rate

FUEL SPRAY
FUEL VAPOR
REVERSE SQUISH
SPRAY ON BOWL LIP
SOOT CLOUD
FUEL FILM ON WALL
SWIRL DIRECTION
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Low-Temperature Combustion
Low NOx/Soot Region
Conventional Combustion
Toward LTC
0 1 2 3 4 5
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Equivalence Ratio
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Exhaust Aftertreatment
ECU
EGR VALVE
AIR FLOW METER
THROTTLE
DOC
PARTICLE FILTER
NOx DEVICE
DOC
VAPORIZER
TEMPERATURE SENSORS
PRESSURE DROP SENSOR
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Lecture Outline

• Overview
• Combustion systems
• Fuel injection systems
• Fuel characteristics
• Performance issues
• Emissions control
• Summary future trends

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Summary 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)

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Future 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
  driving some introduction
• Europe
• New technology (4-valve DI, common-rail
  injection, particulate traps)
• Diesel car sales up dramatically (currently 50
  of new car market)
• Being marketed as performance engine