ZG

Combustion Engine Concepts

Oxygen and Combustion Chamber

  • Increasing oxygen inside the combustion chamber enhances power output.
  • Reducing air speed, while maintaining diffuser function, can impact performance.

Compressor Mechanics

  • Types of Compressors:
    • Centrifugal Compressor: Utilizes centrifugal force to compress air.
    • Axial Compressor: Air flows parallel to the axis of rotation, often more complex than centrifugal.
  • Stages of Compression:
    • Air rotates and compresses as it passes through compressor stages.
    • Each stage can consist of rotors and stators that control airflow and pressure.

Pressure Dynamics and Stages

  • Dual-stage Compression:
    • First stage compresses air by 50%, with a diffuser handling another 50%.
    • Systems may be set for high and low pressure, especially in smaller aircraft.
  • Fixed vs. Moving Parts:
    • Stators are stationary, while rotors rotate to compress air.
    • Air pressure decreases before entering the next rotor, helping maintain consistent energy output.

Compressor Performance Factors

  • Angle of Attack:
    • Blade angles must be carefully designed to prevent stalling (loss of lift).
    • Excessive angles can lead to compression stall, impacting engine efficiency and affecting the aircraft's performance.
  • Material Properties:
    • High temperature-resistant materials (e.g., titanium) are essential due to the extreme conditions in the compressor.
  • Compressor Stall:
    • Can occur due to adverse conditions (e.g., bird strikes, blockage) leading to vibrations and performance loss.

Combustion Process

  • Burning Fuel and Air Ratio:
    • An appropriate air-fuel mixture is crucial for optimal combustion efficiency.
    • Inadequate oxygen results in incomplete combustion, leading to higher exhaust gas temperatures (EGT).
  • Flame Management:
    • Controlling flame speed to avoid backflow into the turbine; maintaining stable combustion conditions is essential to prevent engine stalls.

Engine Management Systems

  • Automatic Control Mechanisms:
    • Systems may automatically adjust fuel air mixtures based on power demands to ensure stable combustion and performance.
  • Safety Systems:
    • Engines may possess mechanisms to manage excess air pressure through relief systems to prevent compressor overloads.

Additional Concepts

  • Rams Air and Engine Performance:
    • As speed increases, the engine may need mechanisms to release extra pressure, impacting efficiency.
    • Air from compressor may also be utilized for aircraft pressurization, enhancing comfort and safety.

Key Terms

  • Stator: Fixed component in compressors that help manage airflow.
  • Rotor: Spins to compress air in the compressor.
  • EGT (Exhaust Gas Temperature): Critical measure indicating combustion efficiency; high EGTs may signify too much fuel or inadequate oxygen.
  • Dynamic Stall: Condition where irregular airflow increases vibration, reducing engine efficiency.