List any 4assumptions made in thermodynamic analysis of CI engine Combustion process ?

 Here are four key assumptions commonly made in the thermodynamic analysis of the CI (Compression Ignition) engine combustion process:


🔧 1. Ideal Gas Behavior

  • The working fluid (air or air-fuel mixture) is treated as an ideal gas, obeying the ideal gas law:

    PV=nRTPV = nRT
  • This simplifies analysis by ignoring real gas effects.


🔧 2. Combustion is Modeled as a Heat Addition Process

  • Combustion is not analyzed in chemical detail; instead, it is modeled as external heat addition to the system (as in air-standard cycle analysis).

  • Chemical reactions are not explicitly solved.


🔧 3. Uniform Pressure and Temperature (Quasi-Steady or Lumped System)

  • The pressure and temperature inside the combustion chamber are assumed to be uniform at each crank angle.

  • This neglects spatial variations and assumes a homogeneous combustion process.


🔧 4. No Heat Loss or Friction (Air-Standard Cycle Assumption)

  • The system is often assumed to be adiabatic, with no heat loss to cylinder walls, and no friction.

  • This simplifies the first law of thermodynamics and focuses on ideal performance.


✅ Summary Table:

Assumption Purpose
Ideal gas behavior Simplifies thermodynamic equations
Combustion = heat addition Avoids complex chemical kinetics
Uniform pressure and temperature Allows single-zone analysis
No heat loss or friction Ideal cycle comparison

These assumptions help create a theoretical model that provides insights into engine performance, efficiency, and combustion behavior, though actual engine conditions are more complex.

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