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Introduction to combustion concepts


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Combustion Engines Finland

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Introduction to combustion concepts

  1. 1. Introduction to engine combustion concepts Professor Martti Larmi March 21, 2019
  2. 2. Introduction to engine combustion concepts Contents • Engine Combustion Basics • Basic Combutions Regimes in Engines: SI, CI, HCCI • Optical Visualization examples • Advanced Combustion Regimes: DF, PPC, SpCCI, SG, RCCI
  3. 3. Engine specific issues in combustion Engine combustion basics Highly transient phenomenon. Combustion timing and duration are most are important for the efficiency. Concepts ”Heat release”, ”Rate of heat release” and ”Combustion efficiency” are used to indicate chemical energy conversion to heat. Heat is the further converted to mechanical work with ”process efficiency”, resulting in the thermal efficiency of the engine.
  4. 4. Cylinder pressure and heat release graph as function of crank angle Basshuysen & Schäfer Internal Combustion Engine Handbook Engine combustion basics
  5. 5. Basic combustion regimes Premixed flame propagation, stoichiometric or lean charge controlled by turbulence. Low efficiency, knock, pumping losses, large speed range. Three way catalyst and particulate filter. Low reactivity fuel preferred. Low temperature combustion, lean and/or diluted charge, controlled by combustion chemistry, highest efficiency, combustion control is challenging. Low emission levels due to low local temperatures and homogenous charge, easy premixing of fuel preferred. Diffusion combustion, lean charge, controlled by mixing, high efficiency, moderate speed range, spray physics in main role. High NOx and PM emissions, DPF and SCR, high reactivity fuel preferred. SI combustion CI combustion HCCI combustion
  6. 6. Most common way of optical diagnostics is observe combustion though a transparent piston. Optical combustion diagnostics Liner Piston Extension 45° Mirror Protection Glass Cylinder Head CCD Camera Mechanical Shutter Common Rail Aalto University Optical Diagnostics
  7. 7. Premixed flame propagation driven by turbulence SI combustion
  8. 8. Combustion driven by the fuel spray induced mixing CI combustion
  9. 9. Combustion controlled by chemical reactions HCCI combustion
  10. 10. Advanced combustion regimes Dual Fuel (DF) combustion, premixed flame is ignited by a ”diesel” pilot, lean charge, high efficiency, low NOx emssions Spark Controlled Compression Ignition (SpCCI), spark and premixed flame initializes HCCI Partially Premixed Compression combustion (PPC, PCCI or PCI) Spark ignited ultra lean burn (Spark Gas, SG) combustion with prechamber Reaction Controlled Compression combustion (RCCI) with two different reactivity fuels for combustion control Low reactivity fuel compression ignition with a pilot fuel (Gas diesel, GD)
  11. 11. Lean burn gas combustion and a diesel pilot Dual Fuel combustion
  12. 12. Lean charge gasoline HCCI ignited by a richer premixed flame SpCCI Mazda Skyactive Mazda
  13. 13. Wärtsilä SG as an example Prechamber in SI engines Wärtsilä
  14. 14. Reactivity controlled compression ignition. Fuels: early injected (premixed) iso-octane and direct injected n-heptane - RCCI
  15. 15. Conclusions Engine combustion basics • There are three basic combustion concepts SI, CI and HCCI. Several advanced concepts exist with focus on high efficiency and low emission levels. • Combustion timing and duration are most are important for the efficiency. • Low combustion temperatures and lean and dilute conditions are essential for low emission level. • There is still plenty of room for combustion development of engines.
  16. 16. Acknowledgements • Richard van Basshuysen and Fred Schäfer: Internal Combustion Engine Handbook • Sandia National Laboratories, Mark Musculus • US DOE, Gurpreet Singh • Aalto University, Research Group of Energy Conversion • Wärtsilä • Mazda