Jet Propulsion and Newton's Third Law

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Questions and Answers

What is the primary function of the convergent-divergent shape in supersonic inlets?

To maintain constant airflow velocity

To increase airflow speed before reaching the compressor

To decelerate incoming airflow to subsonic speed (correct)

To enhance fuel efficiency in engines

Which type of geometrical feature is used in supersonic inlets to adapt to varying flight speeds?

Non-adjustable inlet

Fixed plug

Movable throat (correct)

Static duct

What is a typical application of bell mouth inlet ducts?

Stationary engines on test stands (correct)

Commercial airliners during cruise

Spacecraft re-entry

High-speed fighter jets

How does the design of bell mouth inlet ducts enhance aerodynamic efficiency?

By using a convergent profile Signup and view all the answers

What characterizes the airflow through a bell mouth inlet duct?

Minimal resistance thanks to rounded shoulders Signup and view all the answers

Which of the following is NOT a benefit of using a movable throat in supersonic inlets?

Reduction of engine noise Signup and view all the answers

What is the effect of a bell mouth inlet on aircraft during ground operations?

Enhances efficiency at slow speeds Signup and view all the answers

Which statement best describes the inlet duct configuration of supersonic inlets?

Convergent shape with variable sections Signup and view all the answers

What distinguishes forward-fan engines from aft-fan engines?

Forward-fan engines have the fan mounted in front of the compressor. Signup and view all the answers

What is the bypass ratio in turbofan engines?

The ratio of incoming air that bypasses the fan to the airflow through the engine core. Signup and view all the answers

Which term refers to the comparison of thrust produced by the fan to that produced by the engine core exhaust?

Thrust ratio Signup and view all the answers

Which classification pertains to the bypass ratio?

High bypass, medium bypass, and low bypass. Signup and view all the answers

In which type of engine is the fan positioned behind the compressor?

Aft-fan engine Signup and view all the answers

What is the primary purpose of the fan in a turbofan engine?

To provide thrust by accelerating incoming air. Signup and view all the answers

Why are aft-fan engines typically used in modern commercial aircraft?

They improve aerodynamic efficiency and are quieter. Signup and view all the answers

What does a high bypass ratio indicate about a turbofan engine?

More air bypasses the engine core than passes through it. Signup and view all the answers

What is a characteristic of engines with a low bypass ratio?

Higher speed and altitude capability. Signup and view all the answers

Which component is NOT typically associated with a forward-fan engine?

Engine core located at the rear section. Signup and view all the answers

What is the primary function of a turbine in a turbojet engine?

To convert kinetic energy from hot gases into mechanical energy Signup and view all the answers

Which type of air contributes to the combustion process in a turbojet engine?

A combination of both primary and secondary air Signup and view all the answers

Which statement about the exhaust section of a turbojet is true?

Its design impacts the engine's performance significantly Signup and view all the answers

What percentage of total pressure energy is absorbed by the turbine from hot gases?

60% to 80% Signup and view all the answers

What component is included in the exhaust section of a turbojet engine?

Exhaust nozzle Signup and view all the answers

Which of the following best describes the accessory section of a turbojet engine?

It is also known as the accessory drive Signup and view all the answers

What is the role of the fuel drainage system in a turbojet engine?

To remove excess fuel and prevent pooling Signup and view all the answers

What is the composition of primary air in the combustion process?

25% to 35% Signup and view all the answers

What is the primary role of the accessory drive in aircraft?

To power both engine and aircraft accessories Signup and view all the answers

Which of the following is NOT an accessory powered by the accessory drive?

Navigation lights Signup and view all the answers

Which section of the engine includes the combustion and turbine components?

Hot section Signup and view all the answers

What is one function of the accessory drive besides powering accessories?

Housing the accessory drive gear Signup and view all the answers

The air inlet section is part of which section of the engine?

Cold section Signup and view all the answers

Which of the following components is part of the hot section?

Exhaust Signup and view all the answers

In the context of aircraft, what does the accessory drive primarily do?

Supply power to various systems Signup and view all the answers

Which of the following statements about accessory drives is incorrect?

They are only found in the hot section of the engine. Signup and view all the answers

What happens to the shock wave at the lip of the inlet as the a/c speed increases?

It forms at the lip of the inlet. Signup and view all the answers

Which inlet shape is optimized by shifting the CD duct for a/c speed?

Optimum inlet shape Signup and view all the answers

What is a disadvantage of using a ducted spinner in turboprop engines?

It has difficulty in deicing. Signup and view all the answers

Which of the following statements about ducted spinners is true?

They are heavier and harder to maintain. Signup and view all the answers

What describes a conical spinner?

It is a modified version of a streamline spinner. Signup and view all the answers

Which design is noted as the most efficient for turboprop engines?

Ducted spinner Signup and view all the answers

When comparing ducted and conical spinners, what is a typical characteristic of ducted spinners?

They provide better aerodynamic performance. Signup and view all the answers

Which characteristic is NOT associated with ducted spinners?

Easier to deice. Signup and view all the answers

Who created the toy called Aeolipile that utilized the reaction principle?

Hero Signup and view all the answers

What was the thrust produced by Frank Whittle's first successful turbojet engine?

1000 pounds Signup and view all the answers

Which German engineer designed and built the Heinkel He-178 aircraft?

Hans Von Ohain Signup and view all the answers

What type of engine did the General Electric Company develop under contract in 1941?

Centrifugal-compressor type engine Signup and view all the answers

How fast can today's commercial aircraft fly?

600 MPH Signup and view all the answers

What was the maximum thrust of the GE-1A engine developed by General Electric?

1650 pounds Signup and view all the answers

Which aircraft is known to have flown at Mach 5?

SR-71 Blackbird Signup and view all the answers

What does a rocket engine rely on for combustion?

Own fuel and oxygen Signup and view all the answers

What is one application of today's jet propulsion technology?

Faster than the speed of sound flights Signup and view all the answers

What was the first aircraft powered by a turbojet engine to fly?

Heinkel He-178 Signup and view all the answers

Study Notes

Jet Propulsion

Jet propulsion started during World War 2
Offered several advantages over piston engines including higher speed, increased reliability, and greater efficiency.
It also required less maintenance at high altitudes.
Jet engines have commercial applications in power generation and shipping industries, as well as in modern vehicles.

Applying Newton's Third Law

For every action, there is an equal and opposite reaction.
Acceleration is the action, and forward movement is the reaction.
An example of this is a squid expelling water to propel itself forward, and a balloon propelling itself forward when the opening is released.

Turbine Engine History of Jet Propulsion

Hero of Alexandria (250 B.C.) created the aeolipile, a toy that demonstrated the principle of reaction propulsion.
Dr. Sanford Moss's research applied concepts to turbo-supercharger development.
Frank Whittle created the first successful turbojet engine in 1930.
His patent application was granted in 1930, and the engine completed its first successful flight in a Gloster model E28/29 aircraft in 1939.
The aircraft produced 1000 pounds of thrust.
Hans Von Ohain, a German engineer built a jet engine installed in Heinkel He-178 aircraft, and made a successful flight in August 27, 1939, producing 1,100 pounds of thrust.

Jet Propulsion Today

Modern commercial aircraft fly at 600 mph and can carry over 400 passengers and several tons of cargo.
Commercial and military aviation use jet propulsion to propel aircraft faster than the speed of sound.
The SR-71 Blackbird aircraft can fly at Mach 5.
Concorde aircraft could fly at 2.2 times the speed of sound.
Jet Propulsion is used in both military and commercial aviation today.

Types of Jet Propulsion: Rockets

Rockets are non-airbreathing engines carrying their own fuel and oxygen for combustion.
Two main types are solid-propellant and liquid-propellant rockets.

Types of Jet Propulsion: Solid-propellant Rockets

Use a solid fuel mixed with an oxidizer.
The fuel is formed into a specific shape to promote optimum burning rate.
These rockets are commonly used to propel military weapons and provide additional thrust for takeoff of heavily loaded aircraft.

Types of Jet Propulsion: Liquid-propellant Rockets

Use fuel and an oxidizer, such as liquid oxygen
The resulting high-velocity gas jet behind the rocket provides enough thrust to propel an object.
Space shuttles utilize liquid-fuel rockets.

Types of Jet Propulsion: Ramjet

An aerodynamic duct engine.
No moving parts.
To produce thrust, a ramjet must be moving at high velocity.
In operation, fuel is injected into the engine and ignited, accelerating the air and creating thrust.
Used in some military weapons delivery systems.

Types of Jet Propulsion: Pulsejet

Similar to ramjets but features spring-loaded shutter valves in the air intake duct.
In operation, air enters the engine, fuel is injected and ignited, accelerating the air. The expanding air forces the shutter valves closed, producing thrust.

Types of Jet Propulsion: Gas Turbine Engine

The most practical form of jet engine currently in use for commercial, business, and military aircraft.
Four types: turbojet, turboprop, turboprop, and turbofan.

Types of Jet Propulsion and Components(Turbojet Engine)

Air enters the inlet duct and is compressed by the compressor.
The compressed air goes to the combustion section where fuel is added and ignited.
The heat generates expansion, which rotates the turbine.
The turbine's energy is transferred to the compressor via a common shaft.
The high-velocity exhaust gases generate thrust.
EPR measures engine pressure ratio and is used in setting the power according to given situation.

Types of Jet Propulsion and Components(Turboprop Engine)

A gas turbine engine delivering power to a propeller
Similar design to a turbojet.
The power is transferred to the propeller through a reduction gearbox.
This type is popular in business and commuter aircraft.

Types of Jet Propulsion and Components(Turbofan Engine)

Compromises the best features of turbojet and turboprop.
Includes a multi-bladed fan mounted in front of the compressor.
A portion of the intake air bypasses the core engine to increase thrust, enhance cooling, and reduce noise.
Forward- and aft-fan designs are distinguished by fan location relative to the compressor.

Types of Jet Propulsion and Components(Turboshaft Engine)

A gas turbine specifically designed to deliver power to a shaft, not for producing thrust.
This power is used to drive a propeller or other machinery.
Used in helicopters and industrial applications like electrical generator systems.

Engine Components

Air inlet section: Recovers total pressure from the airstream.
Compressor section: Forces air into the engine and increases pressure.
Combustion section: Combines compressed air with fuel, ignites the mixture, and generates heat and energy.
Turbine section: Extracts energy from the hot gases to drive the compressor and other components.
Exhaust section: Channels and directs exhaust gases to produce thrust
Accessory section/drive: Powers different engine and aircraft accessories such as generators, pumps.
Cold section: Includes the air inlet, compressor, air supply to the cabin, etc.
Hot section: Includes Combustion and gas turbine segment of the engine

Air Inlet Ducts

Forms part of the airframe.
Function: Recovers most total pressure from the free airstreams.
Function: Delivers pressure to the engine compressor.
Inlet shape raises pressure.
Inlet duct has little drag to reduce wear from friction.
Inlet cover protects the intake

Compressor Section components

Component forces air into the engine
Compressor effectiveness is measured by compressor pressure ratio
Supportive function-support combustion; supplying bleed air for cooling purposes.
The air compressor must increase the intake pressure.

Diffuser Section Components

Divergent shape used to slow the leaving compressor velocity to support combustion
Air pressure within the diffuser increases due to decrease in velocity

Combustion Section Components

Made from corrosion resistant steel
Four basic elements:
- One or more combustion chamber(s)
- A fuel injection system
- Ignition source
- Fuel drainage system
Has a primary and secondary airflow segment

Turbine Section Components

Extracts energy from hot gases post combustion
Generates mechanical energy to drive the engine compressor accessories/gearbox.
Approximately 60%to 80% of the total pressure energy from hot gasses are absorbed by the turbine

Exhaust Section Components

The design of the turbojet exhaust section has a strong influence on engine performance.
Exhaust segments: Exhaust cone, exhaust duct/ tailpipe, and the exhaust nozzle

Accessory Section Components

Known as the accessory drive
Provides power to different engine and aircraft accessories
Examples: generators, pumps such as hydraulic, fuel, and oil pumps.

Cold and Hot Section Components

Cold section: air inlet, compressor, and other pre-combustion segments
Hot section: Combustion, turbine, and exhaust

Categories of Thrust Reversers

Mechanical blockage type (clamshell)
Aerodynamic blockage type (obstruction, or cascade vanes
Various types of thrust reversers exist for various engines and situations.

Gearboxes

Known as the accessory drive
Engine's power shaft powers accessories using a set of bevel gears
Power delivery from the gearboxes provides power to the different auxiliary power and accessory segments

Engine Mount

Engine mount for different engine types may vary in construction and use different methods to support the engine

Bearings

A combination of compressor and turbine rotors on a common shaft.
Engine bearings are assigned in a critical function.
Various types of bearings are used for different situations
Special turbines engine(oil-dampened bearing) used for higher quality engines

Compressor Stall

Described as an imbalance between inlet velocity and compressor rotational speed
Occurs when compressor blade angle of attack exceeds critical angle, interrupting airflow and causing turbulence
Indication on cockpit displays may vary depending on the type of stall.

Factors Cause Compressor Stall

Flight in severe turbulent or abrupt maneuvers may cause stall
Excessive fuel flow accompanied by incompatible engine RPM and airflow may cause stall
Damage to compressor blades, stator vanes, or turbine components can cause stall

Combination Compressor

A hybrid design that combines axial and centrifugal compressors

Auxiliary Power Unit (APU)

Turbine-powered units supplying electricity, air conditioning, and other necessities when engines are off
Used in aircraft which need extra power for situations such as passengers and engine maintenance, starting, and running ground operations

Flameout

Causes of flameout: -Excessively high velocity airflow literally blows the flame out -Lean die out occurs at high altitudes when engine speed and fuel pressure are inadequate. -Rich blow out happens when rapid changes occur with a throttle movement that cause fuel temperature to fall below the combustion temperature range

Turbine Section

Component that extracts the energy from the burned fuel and air for propelling
Basic elements include Case, Stator, Shroud, and Rotor

Advantages of Turbojet Engine

Simplicity and low manufacturing costs
Low power required for initial operation
High operating efficiency across a wide range of rotation speeds
High compressor ratio (15:1)

Disadvantages of Turbojet Engine

Large frontal area
Limited stages

Advantages of Axial-flow Compressors

Ability for higher compressor ratio via further stages
Lower aerodynamic drag

Disadvantages of Axial-flow Compressors

High weight.
Low pressure rise per stage (1.25 :1)
Expensive and difficult manufacturing

Types of Compressors

Centrifugal flow compressor
Axial flow compressor

Noise Suppressors

Some released energy from combustion is converted to noise.

Older Design of Turbojet Engines

Require additional noise suppression equipment which includes devices that break airflow behind the tail cone and additional soundproofing and insulating materials.
Re-designing is required to meet more stringent new federal noise standards

Sound Intensity Measure

Sound intensity of engine noise levels are measured in decibels (dB).
A dB is the ratio of one sound to another.

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Description

Explore the fascinating history of jet propulsion, its advantages over traditional engines, and how Newton's Third Law applies to propulsion concepts. From Hero of Alexandria's early inventions to modern jet engines, this quiz covers key developments and principles in the field.