Introduction

Question 1

What are the 2 purposes of an airplane propulsion system?

Answer 1

• Thrust balances drag (Flight at same speed)
• Thrust exceeds drag (Acceleration)

Question 1

What is a propulsion system?

Answer 1

Machine that produces thrust to push an object forward

Question 2

What is excess thrust?

Answer 2

Difference between thrust and drag

Question 3

What are the 4 major forces acting on an aircraft?

Answer 3

• Lift L (orthogonal to flight path)
• Drag D (parallel and opposite to flight direction)
• Weight W (pointed towards earth at angle q relative to L)
• Thrust T (at an angle relative to the flight path)

Question 4

What force has to be generated by the thrust for constant flight?

Answer 4

It has to be opposite in direction but equal in magnitude to the sum of D, W and L

Question 5

What is the energy conversion chain for thrust generation?

Answer 5

1. Energy source (e.g. cerosine) (bound energy)
2. Power generation (e.g. gas turbine) (net power)
3. Propulsion generation (e.g. Propeller) (propulsive power)
4. Thrust

Question 6

What are the 2 main principal propulsion systems?

Answer 6

• Propeller (mechanical acceleration)
• Jet propulsion (thermal acceleration)

Question 7

How is thrust produced in a jet propulsion system and what are the 3 energy sources?

Answer 7

• Thrust produced solely or in part by a high-speed gas exhaust (jet) from inside the engine
• Chemical, thermic or nuclear energy

Question 8

What are 5 examples of jet propulsion systems?

Answer 8

• Gas turbine (turbo-jet) engine
• Ram jet
• Pulse jet
• Rocket engine
• Turbo rocket

Question 9

What thermodynamic cycle is used in gas turbines?

Answer 9

Joule Brayton cycle

Question 10

What are the 5 stages in a turbo-jet engine and what is their purpose?

Answer 10

• Inlet: Intake of mass flow, compression by deceleration of fluid
• Compressor: Work input to compress a fluid to a high pressure
• Combustion chamber: Fuel mass flow input and ignition, heat addition leads to high temperatures
• Turbine: Work output and expansion of the fluid, work needed for the compressor
• Nozzle: Acceleration of fluid to a high velocity by the expansion of the fluid

Question 11

What are the 4 basic requirements for aero engines?

Answer 11

• Guarantee Thrust/Power in Design and Operation
• Safety
• Reliability
• Certification Requirements

Question 12

What are 9 types of turbo-jet engines?

Answer 12

• Twin-spool by-pass turbo-jet
• Triple-spool front fan turbo-jet
• Prop-fan
• Contra-rotating fan-concept
• Double-entry single stage centrifugal turbo-jet
• Single-entry two-stage centrifugal turbo-propeller
• Twin-spool axial flow turbo-propeller
• Single-spool axial flow turbo-jet
• Twin-spool turbo-shaft

Question 13

How can turbomachines be classified?

Answer 13

By flow direction:
- Axialcompressor
- Diagonalcompressor
- Radialcompressor