How Jet Engines Work

Introduction

• Speaker: Jake O'Neal, creator of Animagraffs
• Focus: Explanation of jet engines, specifically the turbofan design

Turbofan Design

• High-tech propeller inside a duct (diffuser)
• Driven by a gas generator

The Core

• Function: Gas generator creating high-pressure gas to power a turbine
• Sections:
  • Compressor
  • Combustor
  • Turbine

Compressor

• Purpose: Compressed air leads to a more powerful combustion reaction
• Mechanism:
  • Occurs in stages
  • Air is forced into a narrower chamber
  • Each stage consists of a spinning rotor and stationary stator vanes
  • Rotor blades swirl air, stator vanes increase air pressure
• Stages: 4 low-pressure, 10 high-pressure

Combustor

• Process:
  • Air mixed with fuel and ignited
  • Releases high-powered gas
• Design: Annular (ring-shaped) combustor
• Components:
  • Inlet nozzles coupled with fuel injectors create an even mix
  • Ignitor plugs, similar to car spark plugs, ignite the mixture
• Operation: Continuous combustion as long as air and fuel are supplied

Turbine

• Powered By: Exhaust gases from the combustor
• Functions:
  • Turns the fan
  • Powers compressor stages
• Conditions: Turbine fins get extremely hot, requiring cooling air from compressor and special coatings
• Exhaust Cone: Shapes and accelerates exhaust, covers sensitive parts

Fan

• Early Design: Turbojets - all air flows through the core
• Modern Design: Turbofans - portion of air enters core, powers fan
• Bypass Air:
  • Air not entering core
  • High bypass engines move large air volumes at slower speeds (310-620 mph)
  • High efficiency but larger engine size

High Bypass Engines

• Applications: Commercial airliners, military transport
• Benefits: Quieter due to surrounding fast core exhaust with slow bypass air

Low Bypass Engines

• Used in military fighter aircraft
• Features: Compact, high power-to-weight ratio, supersonic and afterburner capabilities
• Trade-offs: Poor noise control, high fuel consumption

Afterburner

• For high-performance engines
• Adds additional fuel into the jet pipe
• Purpose: Second combustion stage
• Usage: Short bursts during takeoff, climb, combat
• Exhaust Nozzle: Adjustable for maximum acceleration, avoids back-pressure