Power and Work Formulas in a Gas Turbine Engine

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Questions and Answers

What is the unit of power in the given formula?

foot-pounds per second

joules per hour

newton-meters per minute

foot-pounds per minute (correct)

What is the formula for power when work is substituted into it?

Power = Force × Velocity

Power = Force × Distance × Time

Power = Force × Displacement × Time

Power = Force × Distance / Time (correct)

What is the unit of distance in the given formula?

meters

feet (correct)

inches

yards

What is the unit of time in the given formula?

minutes Signup and view all the answers

What is the alternative formula for power derived from the given formulae?

Power = Force × Velocity Signup and view all the answers

What is the power required to hoist a 2500-lb engine a height of 9 ft in 2 min?

5625 foot-pounds per minute Signup and view all the answers

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

To generate a substantial portion of the total thrust Signup and view all the answers

What is the main advantage of turbofan engines over turbojet engines?

Improved fuel efficiency Signup and view all the answers

What is the characteristic of turbofan engines that allows them to retain short-field takeoff capability?

High bypass ratio Signup and view all the answers

What is the difference between forward-fan and aft-fan engines?

The mounting location of the fan Signup and view all the answers

What happens to the inlet air that passes through a turbofan engine?

It is divided into two separate streams of air Signup and view all the answers

Why are turbofan engines commonly used in commercial airliners?

For their fuel efficiency and turbojet-type cruise speed capability Signup and view all the answers

What is the relationship between pressure and velocity in a venturi according to Bernoulli's theorem?

Pressure is inversely proportional to velocity Signup and view all the answers

What is the significance of Bernoulli's theorem in a jet engine?

It is one of the basic principles of operation Signup and view all the answers

What is the total energy of a particle in motion according to Bernoulli's theorem?

Constant at all points on its path Signup and view all the answers

What is the sum of static and dynamic pressure in a venturi?

Total pressure Signup and view all the answers

What are the two forms of energy that describe the propulsive power of a jet engine?

Potential and kinetic Signup and view all the answers

What is the purpose of energy in a gas turbine engine?

To perform useful work Signup and view all the answers

What is the primary source of kinetic energy in an aircraft?

Its velocity and fuel Signup and view all the answers

What happens to the kinetic energy of an aircraft when it lands?

It is released as heat by the brakes Signup and view all the answers

What is the formula for kinetic energy?

1/2 mv^2 Signup and view all the answers

What is the law of conservation of energy?

Energy can neither be created nor destroyed Signup and view all the answers

What is an example of potential energy?

A fully charged battery Signup and view all the answers

What is the thrust of an engine?

Kinetic energy Signup and view all the answers

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

Enhanced thrust production Signup and view all the answers

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

To compress air Signup and view all the answers

What is the main difference between a turbojet engine and a turbofan engine?

The efficiency at subsonic cruising speeds Signup and view all the answers

What is the result of the heat generated by the burning fuel in a turbojet engine?

The air expands and flows towards the rear of the engine Signup and view all the answers

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

To drive the compressor 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

Study Notes

Formulae for Power and Work

Power formula: P = W / t
Work formula: W = F × D
Substituting work formula into power formula: P = F × D / t
Simplified power formula: P = F × v, where v is velocity

Worked Example

A 2500-lb engine is hoisted 9 ft in 2 min, requiring a certain amount of power

Turbofan Engines

Turbofan engines have turbojet-type cruise speed capability and short-field take-off capability
Fans produce 30%–90% of total thrust, depending on bypass ratio
Nearly all present-day airliners use turbofan engines due to fuel efficiency
Fan can be mounted to front (forward-fan engine) or back (aft-fan engine) of compressor

Bernoulli's Theorem

"The total energy of a particle in motion is constant at all points on its path at a steady flow"
In a venturi, pressure is inversely proportional to velocity
Significance: basic principle of operation of a jet engine

Potential and Kinetic Energy

Energy is used to perform useful work in a gas turbine engine
Potential energy: stored energy due to position (e.g., water behind a dam or fuel)
Kinetic energy: energy possessed by a body due to its motion
Kinetic energy formula: KE = 1/2 mv^2, where m is mass and v is velocity
The thrust of the engine is kinetic energy

Conservation of Energy

"Energy can neither be created nor destroyed"
The law of conservation of energy applies to turbojet engines

Turbojet Engines

Turbojet engines use acceleration of airflow to produce thrust
Suitable for high-speed, high-altitude operations due to enhanced efficiencies
Basic operating principles: air enters through inlet duct, is compressed, mixed with fuel, and ignited, then exits engine at high velocity, producing thrust

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Description

This quiz covers the formulas for power and work in the context of a gas turbine engine, specifically for CASA Part 66 training. It involves substituting the work formula into the power formula.