Compressor Stages and Rotor Blades
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Questions and Answers

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

  • To reduce the air velocity before it enters the combustion chamber. (correct)
  • To mix the air with fuel before it enters the combustion chamber.
  • To increase the static pressure before it enters the combustion chamber.
  • To increase the air velocity before it enters the combustion chamber.

    • What determines the Angle of Attack (AOA) of the compressor blade?

  • Static pressure and air density.
  • Inlet air velocity and compressor rpm. (correct)
  • Compressor surge and aerofoil design.
  • Fuel control sensors and compressor stall.

    • What happens when a single compressor blade or stage stalls?

  • It is said to have stalled. (correct)
  • The entire compressor stalls.
  • The engine shuts down.
  • The engine experiences a surge.

    • What is the result of a compressor stall?

    <p>An imbalance between two vector quantities.</p> Signup and view all the answers

    What can cause engine damage and a loud audible noise?

    <p>Compressor surge.</p> Signup and view all the answers

    How can inlet designs reduce the chance of an intake-induced stall?

    <p>By careful design.</p> Signup and view all the answers

    What is the primary task of an axial compressor?

    <p>To raise air pressure</p> Signup and view all the answers

    What is the result of the airflow as it passes through the rotor blades and stator vanes?

    <p>Increased air pressure and relatively constant air velocity</p> Signup and view all the answers

    Why does the space between the rotor shaft and the stator casing gradually decrease from front to rear in an axial flow compressor?

    <p>To maintain a constant air velocity as air density increases with each stage of compression</p> Signup and view all the answers

    What is the advantage of higher compressor pressure ratios in a gas turbine engine?

    <p>Increased thermal efficiency</p> Signup and view all the answers

    What is the compressor pressure ratio of a single stage in an axial flow compressor?

    <p>1.25:1</p> Signup and view all the answers

    Why are multiple compressor stages needed in an axial flow compressor?

    <p>To increase air pressure ratio</p> Signup and view all the answers

    What is the primary function of the stator vanes in a compressor stage?

    <p>To convert kinetic energy to potential energy</p> Signup and view all the answers

    What determines the velocity present in each stage of the compressor?

    <p>The speed of the rotor</p> Signup and view all the answers

    What is the typical material used to make rotor blades?

    <p>Stainless steel alloy or titanium alloy</p> Signup and view all the answers

    What is the purpose of the rotor blades in a compressor stage?

    <p>To move air rearwards through each stage</p> Signup and view all the answers

    What is a blisk in a compressor rotor?

    <p>A one-piece blade and rotor unit</p> Signup and view all the answers

    What is the trend in modern turbine engine design regarding blisks?

    <p>Applying blisk technology to many smaller fans, compressor rotors, and stators</p> Signup and view all the answers

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

    <p>To control airflow in the compressor</p> Signup and view all the answers

    When are internal VBVs fully open?

    <p>At low and intermediate speeds</p> Signup and view all the answers

    What is the purpose of the variable vane system in a gas turbine engine?

    <p>To reduce airflow into the compressor</p> Signup and view all the answers

    What controls the operation of the variable vane system?

    <p>Fuel pressure</p> Signup and view all the answers

    What happens to the variable stator vanes as the compressor speed is reduced?

    <p>They move towards a closed position</p> Signup and view all the answers

    What is the benefit of the variable vane system in a gas turbine engine?

    <p>Prevention of airflow blockage in the rear stages</p> Signup and view all the answers

    What is the primary advantage of fan blades without stabilizing support shrouds?

    <p>Increased mass airflow</p> Signup and view all the answers

    What material is commonly used for the leading edge sheath of fan blades?

    <p>Titanium</p> Signup and view all the answers

    What is the purpose of moment weighing of fan blades?

    <p>To balance the blade's mass distribution</p> Signup and view all the answers

    What type of fan blades are becoming the top choice for new high/ultra-high bypass engines?

    <p>Swept fan blades</p> Signup and view all the answers

    What is the unit of measurement for the moment weight of a fan blade?

    <p>Grams per millimetre</p> Signup and view all the answers

    What is the benefit of integrating a computer with the mechanical system of blade moment weighing?

    <p>To automate the blade distribution process</p> Signup and view all the answers

    Study Notes

    Compressor Stages

    • Each rotor consists of a set of blades fitted into a disc, which moves air rearwards through each stage.
    • The speed of the rotor determines the velocity present in each stage, and with increased velocity, kinetic energy is transferred to the air.
    • Stator vanes are placed to the rear of the rotor blades to receive the air at high velocity and act as a diffuser, changing kinetic energy to potential energy (pressure).

    Rotor Blades

    • Rotor blades are aerofoils fitted into the disc and move air rearwards through each stage.
    • Rotor rpm determines airflow axial velocity through each stage.
    • Blades are normally made from stainless steel alloy or titanium alloy.
    • Discs are made from nickel steel alloy or titanium alloy.

    Blisks

    • Some compressor rotors have one-piece blade and rotor units called blisks.
    • Blisks are commonly used in small turboprop and turboshaft engines.
    • Forged blisk technology is being applied to many smaller fans, compressor rotors, and stators, and to some turbine components.

    Axial Flow Compressor Operation

    • A single stage in an axial flow compressor can produce a compressor pressure ratio of approximately 1.25:1.
    • High compressor pressure ratios are obtained by adding more compressor stages.
    • The task of an axial compressor is to raise air pressure rather than air velocity.
    • Each compressor stage raises the pressure of the incoming air while the air's velocity is alternately increased, then decreased as airflow proceeds through the compressor.

    Compressor Pressure Ratio

    • The compressor pressure ratio of a gas turbine engine is an extremely important design consideration.
    • The higher the compression, the more remarkable the advantage to the operating cycle in terms of thermal efficiency.
    • The diffuser is known as the point of highest pressure in the gas turbine engine.

    Compressor Stall and Surge

    • Compressor aerofoils experience an infinite variety of AOAs and air densities, and controlling the angle of attack (AOA) is a design function.
    • Compressor stall is an imbalance between the two vector quantities of inlet air velocity and compressor rpm.
    • When a single compressor blade or stage stalls, it is said to have stalled. When the entire compressor stalls, it is known as surge.

    Fan Blade Design

    • The latest high-bypass engines have low-aspect-ratio fan blades, known as wide chord blades.
    • Swept fan blades are now becoming the top choice for all new high/ultra-high bypass engines among leading manufacturers.
    • Low-aspect-ratio fan blades, without mid-span shrouds, produce a higher mass airflow.

    Fan Blade Replacement

    • With the introduction of the large fan blade, moment weighing of blades has assumed a greater significance.
    • The moment weight of a blade is identical to the unbalance effect of the blade when installed into a disc.
    • The recorded measurement of blade moment weights enables each blade to be distributed around the disc so that these unbalances are cancelled.

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    Description

    Learn about the components and functioning of compressor stages, including rotor blades and stator vanes, and how they work together to transfer energy and increase pressure.

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