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Engine Operating Physics

14 days MOT/PHYM-E
Level
Foundation
Audience
  • Engineers and technical staff from design department, testing department wishing to improve their knowledge on following items: engine operation, physics of engines, components design.
Purpose
  • Upon completion of the training, participants will know the engine operating physics, under the mechanical aspects, air loading, fuel injection, ignition, exhaust gas after-treatment.
Learning Objectives
  • To calculate real flow sections in the cylinder head, in EGR circuits or any other fluid circuit.
  • To understand and apply the calculation formulae used during dyno bench tests.
  • To analyze some test results on emissions and efficiency.
  • To analyze the component damage and failure causes.
  • To understand the language and the tools used to analyze vibrations.
Ways and means
  • In every chapter: many exercises simulating real world situations.

Week 1 3.5 days
  • Engine thermodynamic operating (1.5 days)
  • History
  • Thermodynamics basic knowledge: first and second principles, engine efficiency limits. Internal energy, enthalpy, entropy. Ideal gas equation. Laplace equation. Thermodynamic cycles, Beau de Rochas cycle.
  • Compressor isentropic efficiency.
  • Engine architecture - Performance and efficiency parameters (2 days)
  • Geometric parameters: bore, stroke, volumetric ratio, timing diagram.
  • Effective mean pressure: MEP, MFP, MIP
  • Real cycle, differences with theoretical cycle.
  • Global efficiency: analysis using the 4 efficiencies and setting parameter influence.
  • Fuel/air ratio, volumetric efficiency: calculation of the main engine parameters at stabilized rpm.
  • Adaptation to the vehicle: Willans line.
Week 2 3.5 days
  • Engine mechanics (1.5 days)
  • Acyclism
  • Determine the movements of stresses due to gas pressure in the parts.
  • Stresses caused by gas pressure and inertia stresses, impact of the conrod spacing on acyclisms.
  • Acyclism consequences and solutions to limit their impact on the powertrain
  • Balancing
  • Inertia stresses caused by the rotating weight and the alternative weight.
  • Calculation of rotating and alternating inertia forces.
  • Timing: description of the different valve control types, lift law, valve timing.
  • Air loop (2 days)
  • Link between loading and performances. Fluid mechanics.
  • Air loading
  • Variable timing: presentation of the main technologies and their applications.
  • Turbocharging: operating, technology, mapping, adaptation process.
Week 3 3.5 days
  • Combustion (2 days)
  • Air and fuel. Heating value. Ignition equation. Stoichiometric quantity. Equivalence ratio. Specific energy of an air/fuel mixture. Application exercise.
  • Gasoline combustion: flame front propagation, influence of turbulence; influence of the burning rate (HLC) and of the combustion timing (CA 50) on the efficiency; exhaust gas composition depending on the equivalence ratio; calculation of specific emissions, abnormal combustions (knock, pre-ignition, rumble).
  • Diesel combustion: self-inflammation delay, pre-mixture and diffusion flames, formation of pollutants (PM, NOx, HC, CO). Common-rail injection systems; swirl number, EGR.
  • Fuels (1 day)
  • Fuels groups: fuel main required properties for engine operating (heat value, volatility), octane and cetane ratings, Diesel fuel resistance to cold, sulfur content, ...
  • Manufacturing process of fuels in a refinery.
  • Biofuels: fuels-ethanol mixtures, vegetable oils, fatty acid esters.
  • Exhaust gas after-treatment (0.5 day)
  • Structure and operating of oxidation catalysts (Diesel) and trifunctional ones (gasoline). Starting, efficiency. Ageing mechanisms. OSC (Oxygen Storage capacity). Oxygen probe. NOx traps, SCR (Selective Reduction Catalyst). Particles filtration.
Week 4 3.5 days
  • Materials - Mechanical strength (1.5 days)
  • Metallurgist basic tools: iron/carbon diagram, TTT, CCT. Characteristics of the alloy steels used in the automotive industry: cast irons, steels, alumina. Rough casting manufacturing processes. Surface treatment. Parts mechanical properties: Young's modulus, minimum yield, shear rating. Analysis of the engine major parts whose material and manufacturing process have to be chosen.
  • Part damage modes (1 day)
  • Thermal, mechanical and tribologic damages. Goodmann diagram. Stribeck curve.
  • Vibro-acoustics / NVH (1 day)
  • Waves and sound: magnitudes defining a wave, propagation mode (air, solids). NVH vocabulary: dB, dBA, harmonics, resonance ...
  • Signal creation and lock-on, analysis and interpretation (sonogram, tracking).
  • Powertrain noises and vibrations. Attenuation, isolation. Vibration impact on the surrounding parts. Line shafting vibration.