# Jet Propulsion

Topics: Jet engine, Turbofan, Ramjet Pages: 13 (1296 words) Published: April 6, 2013
Jet Propulsion

Bhawesh

Lesson Objectives
 After

to:

this lesson students should be able

Define what a jet engine is
Describe how Newton’s laws apply to jet or
rocket engines
List examples of jet engine applications
List some key points in the history of jet
propulsion
engines

Definition of a Jet Engine
 An

engine that burns fuel and uses the
expanding exhaust gases to turn a turbine
and/or produce thrust

 The

concept of thrust is based on the
principle of Newton’s Third Law

Newton’s Third Law
 For

every action there is an equal and
opposite reaction

 An

example of this is a spray nozzle on a
garden hose

Newton’s Second Law
F=M x A
 Newton’s

second law states - The
force of an object is equal to its mass
times its acceleration

 The

force of the spray nozzle is equal
to the mass of the water multiplied by
the acceleration of the water when it
comes through the nozzle

 This

is the same principle used in rocket
and jet engines

Newton in Practice
Schematic of a rocket engine

Drawing Courtesy of Understanding Flight

Where are jet engines used?
Commercial Airliners – Boeing 757

Where are jet engines used?
Business and personal jets - Learjet

Where are jet engines used?
Military Bombers

B-52 “Stratofortress”

B-2 “Spirit”

Photo Courtesy of www.af.mil

Where are jet engines used?
Military Fighters
F-15 “EAGLE”

F-22 “Raptor”

Photo Courtesy of www.af.mil

Where are jet engines used?
Helicopters - Apache

Photo Courtesy of www.army.mil

Where are jet engines used?
M-1 Abrams Tank

Photo Courtesy of www.army.mil

Where are jet engines used?
Tractor Pulling

Photo Courtesy of gasturbine.pwp.blueyonder.co.uk

Where are jet engines used?
Speed boats

Photo Courtesy of gas-turbines.com

History of Jet Engines
 Invented

in the 1930’s
 Co-invented by Dr. Hans von Ohain
(German) and Sir Frank Whittle (British)
 Developed their ideas separately and at
the time knew nothing of the other’s work

History of Jet Engines
 Germans

were the first to utilize the jet
engine as a military tool
 The jet powered ME-262 was the first jet
powered airplane to see combat
 It had a top speed of 540 mph

Photo Courtesy of Stormbirds.com

History of Jet Engines
 The

SR-71 “Blackbird” set the current speed and
altitude record for a jet powered aircraft in 1961

 Its

top speed is still classified but is in excess
of 2,200 mph

Photo Courtesy of NASA

 High

power to weight ratio
 No reciprocating parts

Less parasitic power loss – no need to
constantly accelerate and decelerate
pistons
Less required maintenance

 The

high speeds and high operating
temperatures make designing and
manufacturing gas turbines complex
from both the engineering and
materials standpoint
 These complexities lead to a higher
price
 Jet engines do not produce high
torque levels, which is why they aren’t
used in automobiles

Review Questions

Describe how a rocket or jet engine produces
thrust
How do Newton’s laws relate to jet engine
operation
Give some examples of jet engine
applications
When and where were jet engines developed
What are some advantages of jet engines
What are some disadvantages of jet engines

Types of Jet Engines

Lesson Objectives
 After

to:

this lesson students should be able

List the six different types of jet engines
Describe how each type of engine propels
the vehicle it is used in
each type

Six different types of jet
engines
 Turbojet
 Turbofan
 Turboshaft
 Turboprop
 Pulsejet
 Ramjet

X-15 with ramjet engine

Photo Courtesy of NASA

Turbojet Engine
 Thrust

produced by gasses...