Power and Work Formulae in Gas Turbine Engine

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Questions and Answers

What is the formula for power?

Power = Work × Time

Power = Work / Time

Power = Force × Distance / Time (correct)

Power = Force / Time

If an engine requires 500 foot-pounds of work per minute, how much power does it require?

500 foot-pounds per minute (correct)

250 foot-pounds per minute

1000 foot-pounds per minute

5000 foot-pounds per minute

What is the unit of measurement for Power?

Newtons per minute

Foot-pounds per second

Foot-pounds per minute (correct)

Joules per minute

If a 2500-lb engine is to be hoisted a height of 9 ft in 2 min, how much power is required?

1125 foot-pounds per minute Signup and view all the answers

What is the formula for Work?

Work = Force × Distance Signup and view all the answers

If the force required to hoist an engine is 2500-lbs, and the distance is 9 ft, what is the work done?

22500 foot-pounds Signup and view all the answers

What is the formula for velocity?

Displacement / Time Signup and view all the answers

What is acceleration defined as in physics?

A change in velocity with respect to time Signup and view all the answers

What is the SI unit for acceleration?

Metres per second squared Signup and view all the answers

What is velocity in the context of a gas turbine engine?

The flow velocity of the gas throughout the engine Signup and view all the answers

What is the difference between the velocity of the two aircraft in the diagram?

Their directions are different Signup and view all the answers

Why is velocity a vector quantity?

Because it has magnitude and direction Signup and view all the answers

What is the main concept behind Newton's Third Law of motion?

Action and reaction forces are always equal and opposite in magnitude. Signup and view all the answers

What is the result of accelerating a mass of air backwards in a jet engine?

An equal and opposite force is produced that moves the aircraft forward. Signup and view all the answers

What is the main principle behind Bernoulli's Theorem?

As air velocity increases, pressure decreases. Signup and view all the answers

What is the purpose of a venturi in relation to Bernoulli's Theorem?

To create a narrowing in a tube where air velocity increases and pressure decreases. Signup and view all the answers

What happens to the pressure inside the balloon as it deflates, according to Newton's Third Law?

The pressure inside the balloon decreases, causing an equal and opposite force to react. Signup and view all the answers

How do Newton's three laws of motion relate to each other?

They are inseparable and take place simultaneously. Signup and view all the answers

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

To compress air before combustion Signup and view all the answers

What is the main advantage of turbojet engines in high-altitude operations?

Enhanced efficiency due to lower air density Signup and view all the answers

What is the purpose of the turbine wheels in a turbojet engine?

To drive the compressor blades Signup and view all the answers

What is the main difference between turbojet and turbofan engines?

Turbofan engines are designed for subsonic cruising speeds Signup and view all the answers

What is the primary purpose of the bypass feature in a turbofan engine?

To allow for higher turbine temperatures Signup and view all the answers

At what speed range is the turbojet or turbofan engine most widely used?

From 450 mph up Signup and view all the answers

What percentage of thrust is produced by the fan in a high bypass fan engine?

Up to 80% Signup and view all the answers

What is the characteristic fan ratio of an ultra-high bypass engine?

9:1 or greater Signup and view all the answers

Which of the following engines is an example of an ultra-high bypass engine?

CFM LEAP Signup and view all the answers

What is a characteristic of a ducted fan engine?

It uses a twin- or triple-spool configuration Signup and view all the answers

What is the advantage of the turbofan engine?

Higher performance and better fuel economy than turbojets and turbo-props Signup and view all the answers

What is the bypass ratio of the P&W 1000G geared fan engine?

12.5:1 Signup and view all the answers

Study Notes

Power and Work

Power formula: P = F × D / t, where P = Power in foot-pounds per minute, F = Force, D = Distance/Displacement in feet, t = Time in minutes
Power can also be related to velocity: P = F × V, where V = Velocity

Velocity

Velocity formula: V = D / t, where V = Velocity, D = Displacement, t = Time
Velocity is a vector quantity
Important in a gas turbine engine, particularly in controlling engine operating temperatures and resultant thrust

Acceleration

Defined as a change in velocity with respect to time
Typical units: feet per second per second (fps/s), miles per hour per second (mph/s), and meters per second squared (m/s²)

Newton's Third Law

"For every action, there is an equal and opposite reaction"
Illustrated through the example of a deflating balloon, where the air escaping the balloon creates an equal and opposite force that propels the balloon forward
Applies to all forms of jet propulsion, including turbojet engines

Bernoulli's Theorem

States that as air velocity increases, pressure decreases, and as velocity decreases, pressure increases
Illustrated through the example of a venturi, where air velocity increases as it passes through a narrowing in a tube, resulting in decreased pressure

Turbojet Engine

Uses the acceleration of airflow throughout the engine to produce thrust
Well-suited for high-speed, high-altitude operations
Basic operating principles:
- Air enters through an inlet duct and is compressed
- Fuel is added and ignited in the combustor section
- Heat generated by combustion causes compressed air to expand and flow towards the rear of the engine
- Air exits the engine at a much higher velocity than the incoming air, producing thrust

Turbofan Engine

Developed for subsonic cruising speeds
Has become the most popular power plant for commercial and business jets
Greater propulsive power at higher subsonic cruising speeds
Replaced the turbojet engine due to its higher efficiency

Turbofan/Bypass Engines

Consists of a multi-bladed ducted propeller driven by a gas turbine
Produces most of its thrust from the fan (up to 80%)
Fitted to large commercial jets

Ultra-High Bypass Engine

Has a fan ratio of 9:1 or greater
Requires a larger fan diameter and a geared fan
Examples: CFM LEAP, RR Trent 1000, P&W 1000G geared fan
Produces up to 90% of its thrust from the fan

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Description

This quiz covers the formulae for power and work in the context of gas turbine engine, including the substitution of work formula into power formula.