AT 262 Exam 3 (Turbine Engine Types ->

Thrust

Forward directed force from a rearward acceleration of a mass of air or fluid

Methods of producing thrust

Aerodynamic action

Jet reaction engines

Aerodynamic Action define

Lift produced along a horizontal plane

Large mass of air through small change in velocity

Jet reaction define

Mass of air heated inside the engine

Mass of air and amount it is accelerated determines thrust

Small mass of air through large change in velocity

Energy define

Capacity of a physical system to do work

Law of conservation of energy

Energy can neither be created nor destroyed, but it can be changed from one form to another

Forms of energy

Chemical

Mechanical

Electrical

Heat

Light

Nuclear

Bernoulli’s principle

Total energy in a column of moving fluid remains constant through the column

Total energy = potential energy + kinetic energy

Bryson Cycle

Constant pressure cycle f energy transformation used by a gas turbine engine

All events occur at the same time (intake, compression, expansion, power, exhaust)

Supersonic air flow components

Converging duct, diverging duct

Converging duct

Air does not speed up but compresses

Velocity decreasing

Pressure and density is increasing

Diverging ducts

Air expands

Velocity increases

Pressure and density decreases

Pressure waves types

Normal shock

Oblique shock

Expansion

Airflow through a chocked nozzle

When subsonic air flows into a converging duct or nozzle the velocity increases

Jet engine types

Non air breathing (rocket) engines

Air breathing reaction engines

Non air breathing engines

Carries all needed oxygen within their fuel

Generated heat by chemical reaction btw fuel and oxidizer

Air breathing reaction engine types

Turbojet

Turboprop

Turbo shaft

Turbofan

Pulse jet

Ramjet

Scramjet

Turbojet engine operation

Take air in through air inlet

Compresses air

Mixes air with fuel

Mixture ignited and burned

Hot gasses pass through turbine

Air forced out of specifically shaped exhaust nozzle, forming a high speed jet

Turbo shaft engines must have

reduction gear box

Turboprop engines operation

Drives a propeller

Derivative of Turbojet engine

2 methods of drive propeller

• connection propeller to compressor

• Connecting propeller to turbine separate from core engine (free turbine engine)

Propeller to compressor problems

Takes a lot more energy to start engine (longer start up)

Changing pitch on propeller affects load on turbine