Engine Performance and Combustion

4 credits

Course Purpose

There is much confusion as to what really governs, and ultimately limits, internal combustion engine performance. There are fundamental, theoretical limits imposed by thermodynamics and chemical kinetics. There are regulatory limits invoked by emission, noise and safety constraints. Then there are practical limits imposed by manufacturing capabilities and cost. Often these constraints compete with one another. Making intelligent choices about the directions to pursue in new designs, approaches to achieve operational criteria, or energy converters to achieve the requisite power, requires a sound understanding of the fundamental operation of the engine.

This course is designed to provide that fundamental understanding. As the energy conversion process is rooted in the chemical reaction occurring in the cylinder, the combustion process will serve as the foundation of study. The course starts with establishing the difference between heat engines and chemical processes. From this basis, the course proceeds to analyses for the important phenomena associated with the energy conversion process and how these processes are impacted by engine characteristics.

Course Objectives

  • Understand theoretical and practical limits of maximum engine performance.
  • Analyze engine combustion phenomena from a fundamental thermo-chemical perspective, including effects of mixture preparation strategy, in-cylinder charge motion.
  • Understand in-cylinder pollutant formation mechanisms, abatement strategies and aftertreatment systems and their implications.
  • Identify coupling between a single control input and the remainder of the engine system.
  • Compare and contrast mixture preparation strategies.
  • Compare and contrast alternative energy conversion strategies.

Topics

Heat Engines versus Chemical Conversion Processes

  • Thermodynamics of heat engines
  • Thermodynamics of chemical reactions
  • Fundamental limits of heat engines and chemical processes
  • Typical partitioning of fuel energy for engine applications

Thermodynamic Equilibrium

  • Thermodynamic principles of equilibrium
  • Calculation of equilibrium composition
    • adiabatic flame temperature
  • Heat release analysis
  • Time to reach equilibrium
  • Equilibrium concentration versus regulated emissions

Chemical Reactions and Chemical Kinetics

  • Systems of chemical reactions
  • Chemical rate equations
  • Characteristics times: chemical, flow, engine
  • Ignition and extinction

Flames

  • Premixed and non-premixed
  • Flame propagation
  • Flame fluid interactions
    • effects of turbulence
  • Mass burn rate: engineering models

Applications to Spark Ignited and Diesel Engines

  • Premixed engines: flame propagation
  • Heterogeneous combustion
    • spray phenomena
    • air-fuel mixing limits

Alternative (non-flame) Energy Conversion Processes

  • HCCI, CAI, MK, etc.
  • Fuel cells

Fuels

  • Global fuel resources, alternative fuels
  • Energy content and important physical and chemical characteristics, trace compositions
  • Well-to-wheels and well-to-tank assessment

Emissions

  • Sources of CO, HC, NOx and particulate matter
  • Unregulated emissions
  • The engine and the atmosphere
    • smog and ozone
  • Phenomenological and detailed approaches to assessing emissions
    • differences in emissions for different energy release processes
  • Strategies for reducing emissions
  • Fundamental and practical limits

Aftertreatment Approaches

  • Three-way catalysts
  • Lean aftertreatment systems
    • SCR systems
    • traps
    • regeneration
  • Particulate traps
  • Importance of engine exhaust composition

Integration

  • Connection between "typical" engine control parameters and combustion emission phenomena
    • variable valve actuation
    • in-cylinder geometry
    • manifold design
  • Heat transfer
  • Case studies