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New Combustion Developments in Diesel Engines

New Combustion Developments in Diesel Engines

3 days
MOT/COMBD-E
Sessions
This course is not scheduled.
Who should attend?

Audience

    • Engineers and technical staff who have to optimize Diesel engine combustion.

Level

  • Advanced
  • To understand, in Diesel engines:
  • the role of the injection system and of aerodynamics in the cylinder on the air-fuel mixture
  • the mechanisms of the mixture inflammation, of combustion and of pollutants formation
  • the influence of the engine tuning parameters on performances, efficiency and emissions
  • the turbocharger behavior.
Learning Objectives
  • To be able to organize a series of tests and to analyze the results in order to optimize:
  • the combustion system (injection system, internal aerodynamics, combustion chamber geometry)
  • the engine tuning parameters (advance, injection pressure, multi-injections, exhaust gas recirculation).
Course Content

Fuel jet inflammation

0.5 day

  • Diesel engine history.
  • Diesel combustion stages. Self-inflammation delay, basic knowledge on cold flames, influence of the different temperature, pressure, air-fuel ratio, residual gas parameters. Pre-mixture flame and diffusion flame combustions. Soot formation and oxidation mechanisms, nitrogen oxides and carbon monoxide formations.
  • Jet structure during combustion.

Diesel combustion

1.5 days

  • Optimization situation of diesel combustion system during the design process.
  • Pollutants formation in heterogeneous combustion: particles, nitrogen oxides, unburnt hydrocarbons, carbon monoxide.
  • The three phases of combustion. Noise. Pre-injection and post-injection.
  • Injectors jets behavior: introduction rate, jets penetration and atomization, cavitation, injection jets overlap; optimization of the injector jets set, bowl shape and dimensions, swirl.
  • Exhaust gas recirculation (EGR): effect on combustion, EGR cooling, interest of low pressure EGR.
  • Full load performances: limiting parameters, cylinder head thermodynamic resistance; supercharging, interest of a variable geometry turbocharger.
  • Start and cold start. Glow plug and post-glow plugs.
  • Combustion optimization at dyno bench: injector jets positions, influence of injection advance and of low-load and high-load EGR, injection pressure, supercharging pressure. Combustion system evolutions.
  • Practical exercises on dyno bench test results interpretation.

Aerodynamics - Swirl generation & measurement

0.25 day

  • Interference between the swirl and the squish.
  • Influence on the air-fuel mixture and on combustion.
  • Defining the swirl number and the cylinder head permeability. Bowl shape in the piston.

Injection systems

0.25 day

  • Injectors nozzles, injector holes flow rate coefficient, hydraulic flow rate.
  • Exercise: determining a hydraulic flow rate.
  • Common-rail injection systems technologies: solenoid control (balanced or unbalanced electrovalve), piezo-electric control, 2-way and 3-way valves, direct piezo control, pressure amplification systems.

Homogeneous charge compression ignition (HCCI)

0.5 day

  • Operating principle, interest, examples of developments.
  • Critical points: operating area without NOx formation, HC and CO emissions, high load operating, combustion control.
  • Technologies to be implemented to optimize the concept as a whole: combustion system, exhaust gas after-treatment, engine control (acting on the exhaust gas recirculation, the turbocharger, the inlet temperature, the variable timing).
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