Turbine Engine Compressor Section

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is an advantage of a centrifugal flow compressor?

Higher weight

Complex construction

Lower ruggedness

Light weight (correct)

What is the purpose of the diffuser in a centrifugal flow compressor?

To increase the air's velocity

To provide a divergent duct for air to accelerate

To provide a divergent duct for air to slow down and increase in static pressure (correct)

To distribute air to the combustion section

What is a benefit of a single-sided impeller in an aircraft installation?

Increased engine weight

High mass airflow

Benefit from ram effect and less turbulent air entry (correct)

Narrower overall engine diameter

What is a characteristic of a dual-sided impeller design?

Narrower overall engine diameter Signup and view all the answers

What is the purpose of the compressor manifold in a centrifugal flow compressor?

To distribute air to the combustion section in a turbulence-free condition Signup and view all the answers

What is a disadvantage of a dual-sided impeller design?

It does not receive the full benefit from ram effect Signup and view all the answers

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

To increase the pressure of the air entering the combustor Signup and view all the answers

What is the result of the compression process in a turbine engine?

A conversion of kinetic energy to potential energy Signup and view all the answers

What is the principle of maximum compression in a turbine engine compressor?

Maximum compression with minimum temperature rise Signup and view all the answers

What causes the temperature rise in the compressor of a turbine engine?

Compression and friction Signup and view all the answers

What is the advantage of having a lower temperature air entering the combustor?

A higher temperature rise during combustion Signup and view all the answers

What is the typical velocity of air flowing through some compressors?

120-150 m/s Signup and view all the answers

What is the purpose of stator vanes in an axial flow compressor?

To decrease the velocity of air coming off the rotor and raise its pressure Signup and view all the answers

What is the primary material used for constructing stator vanes?

Stainless steel alloy Signup and view all the answers

What is the function of variable stator vanes?

To maintain airflow directed at the correct angle to the succeeding rotors Signup and view all the answers

What is the shape of stator vanes?

Aerofoil Signup and view all the answers

What is the purpose of the external ring in variable stator vanes?

To rotate the vane to close it as rpm is reduced Signup and view all the answers

What is achieved by contact and wear between the profile tip and abradable compressor casing?

Zero clearance Signup and view all the answers

What happens to the engine fuel consumption if the pressure ratio for a given mass airflow and thrust increases?

It decreases Signup and view all the answers

What happens to the engine weight as the strength of materials is increased?

It increases Signup and view all the answers

How is the compressor pressure ratio typically calculated?

By dividing the compressor discharge total pressure by the compressor inlet total pressure Signup and view all the answers

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

To supply the first stage of compression Signup and view all the answers

What happens to the velocity of the airflow as pressure builds in the rear stages of the compressor?

It decreases Signup and view all the answers

What is the approximate relationship between the inlet and outlet velocities of the compressor?

They are approximately the same Signup and view all the answers

What is the primary function of the compressor bleed system in a gas turbine engine?

To dump unwanted air at low and intermediate speeds Signup and view all the answers

At what rotational speeds is the compressor bleed system typically closed?

High rotational speeds Signup and view all the answers

What is the purpose of bleeding away air in the rear stages of the compressor at low speeds?

To prevent piling up of air molecules Signup and view all the answers

What is typically used to dump unwanted air in smaller engines?

Sliding band Signup and view all the answers

What is the relationship between compressor pressure ratio and the need for systems controlling the stall margin?

The higher the pressure ratio, the greater the need for stall margin control Signup and view all the answers

What type of control is typically used for stall/surge bleed valves on modern engines?

Variable operation with FADEC control Signup and view all the answers

Study Notes

Compressor Section

The compressor section supplies air to the combustor and converts fuel energy and mechanical work into potential energy.
Compression occurs through the acceleration of a working fluid followed by diffusion, resulting in a pressure rise.
The primary purpose of the compressor is to increase the pressure of the air entering the engine inlet and discharge it to the diffuser and then to the combustor section at the correct velocity, temperature, and pressure.
Compressor efficiency is based on the principle of maximum compression with the least temperature rise.

Temperature Rise in the Compressor

Temperature rise in the compressor is caused by compression and friction.
The colder the air entering the combustor, the greater the rise in temperature during the combustion process.

Axial Flow Turbojet

Axial flow turbojet compressors must flow air at a velocity of 120-150 m/s (400-500 ft/s) and raise its static pressure 20-60 times in a short engine length.

Centrifugal Flow Compressors

The centrifugal flow compressor is the oldest design and is still in use today.
Advantages of centrifugal flow compressors include:
- Light weight
- Ease of construction
- Ruggedness
A centrifugal flow compressor assembly consists of:
- An impeller rotor
- A diffuser
- A manifold

Impeller

The impeller is usually made from aluminum alloy or titanium alloy and can be either single- or dual-sided.
The diffuser provides a divergent duct in which the air spreads out, slows down, and increases in static pressure.
The compressor manifold distributes the air in a turbulence-free condition to the combustion section.

Stator Vanes

Stator vanes are the stationary blades located between each row of rotating blades in an axial flow compressor.
Stator vanes act as diffusers for the air coming off the rotor, decreasing its velocity and raising its pressure.
Stator vanes also help prevent swirling and direct the flow of air coming off each stage to the next stage at the appropriate angle.

Variable Stator Vanes

Some stator vanes can be variable in angle, similar to inlet guide vanes.
Variable stator vanes can be used to maintain airflow directed at the correct angle to the succeeding rotors.

Compressor Pressure Ratio

The compressor pressure ratio is determined by measuring the total pressure after the last stage of compression and dividing it by compressor inlet total pressure.
The compressor pressure ratio can also be described in terms of pressure ratio per stage.

Compressor Taper

As pressure builds in the rear stages of the compressor, velocity tends to drop in accordance with Bernoulli's principle.
Velocity rises and falls through the successive stages of the compressor, but maintains approximately the same inlet and outlet velocity.

Compressor Bleed System

The compressor bleed system automatically dumps away unwanted air to prevent aerodynamic disturbance.
The system is used in some engines at low and intermediate speeds to maintain the correct airflow and pressure ratio.
The compressor bleed system is typically scheduled closed at high rotational speeds.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Learn about the compressor section in a turbine engine, its functions, and how it supplies air to the combustor.