Compressor Overview and Types
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Questions and Answers

Which combination of symptoms can indicate both surge and stall in a compressor?

  • Consistent airflow and stable temperature
  • Reduced RPM and lower noise levels
  • Increased power output and decreased vibration
  • Loss of power and increase in EGT (correct)

    • Which factor is most likely to lead to compressor surge due to airflow issues?

  • Optimal engine speed and air pressure
  • High inlet temperature and reduced air velocity (correct)
  • Stable atmospheric conditions
  • Consistent throttle movement during flight

    • What mechanical malfunction can cause compressor stall as a result of airflow impairment?

  • Stable fuel control unit (FCU)
  • Excessive fuel flow control
  • Variable stator vane (VSV) failure (correct)
  • Inlet guide vane optimization

    • Which solution specifically aims to manage airflow at lower engine speeds to prevent stall?

    <p>Air bleed valve</p> Signup and view all the answers

    Which symptom is NOT typically associated with compressor surge or stall?

    <p>Consistent power output</p> Signup and view all the answers

    What factor is least likely to lead to compressor stall during flight operations?

    <p>Gradual changes in aircraft attitude</p> Signup and view all the answers

    Which malfunction could directly result in diminished fuel management within the combustion chamber?

    <p>Fuel control unit (FCU) failure</p> Signup and view all the answers

    Which component can be adjusted to alter the angles of attack to improve airflow conditions?

    <p>Variable guide vane (VGV)</p> Signup and view all the answers

    What is a potential disadvantage of using mid-span support for narrow fan blades?

    <p>Causes fan blade shingling by blocking airflow</p> Signup and view all the answers

    Which of the following factors contributes to improved aerodynamic efficiency in wide chord fan blades?

    <p>Reduced frontal area with increased flow</p> Signup and view all the answers

    What construction method is used for wide chord fan blades to achieve superior performance?

    <p>Sandwich of titanium honeycomb and titanium panels under vacuum</p> Signup and view all the answers

    What primary function do variable inlet guide vanes serve in a centrifugal compressor system?

    <p>Enhance airflow stability and control</p> Signup and view all the answers

    In the context of gas turbine engines, which type of compressor configuration is typically used for higher compression ratios?

    <p>Axial followed by a centrifugal compressor</p> Signup and view all the answers

    What is a disadvantage of using more than a single entry centrifugal compressor?

    <p>Energy loss due to airflow slowing down</p> Signup and view all the answers

    What issue arises from insufficient tip clearance in a centrifugal flow compressor?

    <p>Engine vibration leading to potential contact between parts</p> Signup and view all the answers

    How does an oversized tip clearance affect the centrifugal compressor's performance?

    <p>Reduces efficiency by allowing airflow to bypass the diffuser</p> Signup and view all the answers

    What is typically the compression ratio for an axial compressor per stage?

    <p>1.2</p> Signup and view all the answers

    What comprises the assembly of an axial compressor?

    <p>Rotating blades and stationary vanes</p> Signup and view all the answers

    Which of the following is NOT a symptom of potential stall in a compressor?

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

    What is a critical factor that could lead to surge in a compressor system?

    <p>Excessive airflow resistance in the system</p> Signup and view all the answers

    What is the primary function of the stator in an axial compressor?

    <p>To transform part of the air velocity into pressure</p> Signup and view all the answers

    In terms of mechanical malfunctions, what can excessive vibration in a compressor indicate?

    <p>Potential mechanical failure or misalignment</p> Signup and view all the answers

    What might contribute to the increased weight in a multiple-entry centrifugal compressor design?

    <p>Higher number of impellers and structural supports</p> Signup and view all the answers

    What characterizes compressor stall?

    <p>A localized condition affecting only a few stages</p> Signup and view all the answers

    Which of the following factors is primarily responsible for compressor surge?

    <p>Inconsistent airflow through the compressor</p> Signup and view all the answers

    What is a primary disadvantage of axial compressors?

    <p>Higher susceptibility to surge</p> Signup and view all the answers

    Which method is used to manage tip clearance in axial compressors?

    <p>Wearing away the blade tips through coating</p> Signup and view all the answers

    Which advantage of multi-spool engines contributes to better control of stall characteristics?

    <p>Less inertia of spools</p> Signup and view all the answers

    At the inlet guide vane (IGV), what happens to velocity and pressure?

    <p>Both velocity and pressure remain constant</p> Signup and view all the answers

    Which of the following is a sign of compressor surge?

    <p>Abrupt changes in engine performance</p> Signup and view all the answers

    What is a potential consequence of foreign object damage in an axial compressor?

    <p>Compromised mechanical design and possible stall</p> Signup and view all the answers

    What happens to velocity and pressure immediately after the 1st stage rotor?

    <p>Velocity and pressure both increase</p> Signup and view all the answers

    Which of the following contributes to higher efficiency in axial compressors?

    <p>Flow direction at discharge being suitable for multi-staging</p> Signup and view all the answers

    What is one of the primary advantages of a centrifugal flow compressor?

    <p>Wider range of stable operation between surging and choking limits</p> Signup and view all the answers

    Which factor is NOT commonly associated with compressor stall or surge?

    <p>Uniform air volume input</p> Signup and view all the answers

    What mechanical malfunction is associated with excessive energy losses in multi-stage centrifugal compressors?

    <p>Inter-stage energy loss</p> Signup and view all the answers

    Which control solution is most effective in preventing compressor surge?

    <p>Implementing variable speed drives</p> Signup and view all the answers

    What is a significant disadvantage of the double entry impeller design in centrifugal compressors?

    <p>Non-uniform air input from both ducts</p> Signup and view all the answers

    What is the typical compressor efficiency that can be expected from a centrifugal compressor with a compression ratio of 4 to 5?

    <p>80%</p> Signup and view all the answers

    Which architectural feature contributes significantly to the larger frontal area of centrifugal flow compressors?

    <p>Greater inlet duct dimensions</p> Signup and view all the answers

    What is one common symptom of compressor stall during operation?

    <p>Sudden decrease in flow rate</p> Signup and view all the answers

    What is a characteristic feature of an axial flow compressor?

    <p>Uses multiple impeller stages to compress air</p> Signup and view all the answers

    What control strategy is most appropriate for enhancing adiabatic efficiency in a compressor?

    <p>Regular maintenance checks</p> Signup and view all the answers

    What is a primary advantage of wide chord fan blades over narrow fan blades?

    <p>Fewer FOD ingestion</p> Signup and view all the answers

    Which feature is essential for preventing aerodynamic instability in narrow fan blades?

    <p>Mid-span support</p> Signup and view all the answers

    What composition is used in the construction of wide chord fan blades?

    <p>Titanium honeycomb and titanium panels</p> Signup and view all the answers

    In a centrifugal compressor assembly, what component helps manage airflow efficiency?

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

    Which of the following statements about fan blade shingling is accurate?

    <p>It causes overlapping of mid-span shrouds and reduces airflow.</p> Signup and view all the answers

    What is a primary advantage of a centrifugal flow compressor over an axial flow compressor?

    <p>Wider range of stable operation</p> Signup and view all the answers

    Which characteristic is true for a two-stage centrifugal flow compressor?

    <p>It can achieve higher compression ratios up to approximately 14:1.</p> Signup and view all the answers

    What is a disadvantage of a centrifugal flow compressor's larger frontal area?

    <p>It results in increased drag in some applications.</p> Signup and view all the answers

    What is the expected compressor efficiency for a centrifugal compressor with a compression ratio of 4 to 5?

    <p>80%</p> Signup and view all the answers

    Which of the following factors is NOT typically associated with maintaining compressor adiabatic efficiency?

    <p>Increasing rotational speed</p> Signup and view all the answers

    What is a significant drawback of using more than two stages in a centrifugal compressor?

    <p>Higher energy losses between stages</p> Signup and view all the answers

    What construction characteristic poses challenges for double entry impellers in centrifugal compressors?

    <p>Consistency in airflow distribution</p> Signup and view all the answers

    What factor primarily limits the practical number of stages in a centrifugal compressor design?

    <p>The energy losses occurring between stages</p> Signup and view all the answers

    What leads to a reduction in air velocity resulting in compressor surge?

    <p>High power operation at low air speeds</p> Signup and view all the answers

    Which mechanical malfunction is associated with an inability to control airflow in a compressor?

    <p>Variable stator vane failure</p> Signup and view all the answers

    What effect can surge or stall have on a turbine's condition?

    <p>Increased gas temperature</p> Signup and view all the answers

    Which component is designed to alleviate pressure in the high-pressure compressor area?

    <p>Bleed Valve</p> Signup and view all the answers

    What primarily mitigates the risk of surge during abrupt changes in aircraft attitude?

    <p>Implementation of split spool systems</p> Signup and view all the answers

    What can result from excessive fuel flow during sudden acceleration in a compressor?

    <p>Increased combustion chamber pressure</p> Signup and view all the answers

    What is a common consequence of sustained compressor stall or surge operations?

    <p>Smoke and flames from the exhaust</p> Signup and view all the answers

    Which solution can directly adjust the airflow angles to prevent stall in a compressor?

    <p>Variable Guide Vane</p> Signup and view all the answers

    What atmospheric condition is most likely to lead to a deficiency of air volume in a compressor?

    <p>Low altitude pressure systems</p> Signup and view all the answers

    What is the role of the Variable Guide Vane in compressor control systems?

    <p>To adjust the angles of airflow for performance</p> Signup and view all the answers

    What is a significant disadvantage of using multiple-entry centrifugal compressors?

    <p>Increased energy losses as airflow changes direction.</p> Signup and view all the answers

    Which factor is crucial for maintaining efficiency in a centrifugal flow compressor?

    <p>Maintaining an optimal tip clearance.</p> Signup and view all the answers

    What does the rotor in an axial compressor primarily do?

    <p>Impart motion to the air mass.</p> Signup and view all the answers

    How does the compression ratio in an axial compressor typically behave?

    <p>It approximates 1.2 per stage.</p> Signup and view all the answers

    What can be a direct consequence of too large a tip clearance in a centrifugal compressor?

    <p>Reduced airflow velocity entering the diffuser.</p> Signup and view all the answers

    What is a defining feature of a stage in an axial compressor?

    <p>A row of alternating stationary and rotating blades.</p> Signup and view all the answers

    What is one of the primary disadvantages of an axial compressor?

    <p>Increased mechanical complexity with multiple stages.</p> Signup and view all the answers

    What is a potential issue caused by excessive vibration in a centrifugal compressor?

    <p>Damage to the compressor components.</p> Signup and view all the answers

    What is the role of the stator in an axial compressor?

    <p>To transform air velocity into pressure.</p> Signup and view all the answers

    What effect does the addition of stages have on the overall efficiency of an axial compressor?

    <p>It decreases the overall efficiency beyond a certain point.</p> Signup and view all the answers

    What happens to the velocity and pressure at the inlet guide vane (IGV)?

    <p>Velocity and pressure remain constant</p> Signup and view all the answers

    What is a potential disadvantage of using axial compressors?

    <p>Higher susceptibility to surge</p> Signup and view all the answers

    Which statement accurately describes the behavior of velocity and pressure after the 1st stage rotor?

    <p>Velocity decreases and pressure increases</p> Signup and view all the answers

    What is the primary purpose of the stator in the axial compressor?

    <p>To direct airflow and reduce turbulence</p> Signup and view all the answers

    What is a major advantage of multi-spool engines when compared to single-spool engines?

    <p>Better control of stall characteristics</p> Signup and view all the answers

    What defines compressor surge in a compressor system?

    <p>Complete airflow breakdown in the entire compressor</p> Signup and view all the answers

    How does the mechanical design of an axial compressor compare to other types of compressors?

    <p>It is complex, contributing to higher risk of maintenance issues</p> Signup and view all the answers

    What must occur to achieve higher compressor ratios in multi-spool engines?

    <p>More stages need to be added</p> Signup and view all the answers

    Which of the following accurately describes the behavior of pressure at the first stage stator?

    <p>Pressure increases, while velocity decreases</p> Signup and view all the answers

    Study Notes

    Compressor Overview

    • A compressor is a mechanical device used to increase the pressure of a gas.
    • Different types of compressors exist, including centrifugal and axial flow.
    • Compressor performance is assessed using a performance map, considering pressure ratio, gas flow (mass flow rate), rotational speed and adiabatic efficiency (no heat loss/gain).

    Centrifugal Flow Compressor

    • Advantages: High stage pressure ratios, simple and rugged construction, less performance drop from dust, shorter length for same pressure ratio, wider stable operation range.
    • Disadvantages: Larger frontal area for given flow rate, more than 2 stages are less practical due to energy losses between stages.
    • Components: Impeller, swirl vanes, diffuser, compressor manifold.
    • Double Entry Impeller: A disadvantage needing careful design to direct air to the rear impeller, air input may not be uniform from both inlet ducts due to aerodynamic flow.
    • Two-Stage Compressor: Higher compression ratio (up to 14/1) achievable with two centrifugal stages.

    Axial Flow Compressor

    • Advantages: Smaller frontal area, flow direction at discharge is more suitable for multi-staging, higher efficiency at high pressure ratios.
    • Disadvantages: Complex mechanical design, higher possibility of surge, more prone to foreign object damage.
    • Components: Rotor (rotating blades), stator (stationary vanes), Inlet Guide Vane (IGV).
    • Stages: A row of rotating and stationary blades is called a stage. Compression ratio per stage is approximately 1.2.

    Compressor Stall and Surge

    • Stall: Localized condition, one or few compressor stages impacted by airflow disruption, affecting efficiency but may not completely stop airflow.
    • Surge: Entire compressor experiences complete airflow breakdown, due to significant pressure fluctuations.
    • Signs of stall/surge: Loss of power, vibration, RPM changes, EGT (Exhaust Gas Temperature) increase, loud noise.
    • Causes of stall/surge: Excessive power operation with low air speed; high inlet temperatures; distortion of inlet airflow causing reduced airflow velocity; excessive fuel during sudden acceleration causing increased combustion chamber pressure hindering airflow; abrupt changes in aircraft attitude; air turbulence; atmospheric conditions affecting available air; rapidly throttling the engine.
    • Mechanical Causes of stall/surge: Variable stator vane (VSV) failure, fuel control unit (FCU) failure, foreign object damage (FOD), variable exhaust nozzle failure.
    • Effect of Surge/Stall: Increased gas temperature damaging turbines; severe vibration damaging bearings; unusual loud noises; exhaust smoke/flames; loss of power.

    Solutions for Compressor Stall and Surge

    • Variable Guide Vane (VGV) or Variable Stator Vane (VSV)
    • Air bleed valve
    • Split spool
    • Variable exhaust nozzle

    Compressor Fan Blades

    • Attachment Methods: Dovetail root, solid root, fir tree root
    • Types of Fan Blades: Narrow, wide-chord

    Shingling of Narrow Fan Blades

    • Shingling is the overlapping of mid-span shrouds on fan blades.
    • A mid-span support (snubber or clapper) is necessary to prevent aerodynamic instability and blade bending.
    • A disadvantage is that the shroud blocks some airflow, impacting blade shingling.

    Wide-Chord Fan Blade Advantages

    • Fewer foreign object damage (FOD) ingestions
    • Increased aerodynamic efficiency
    • Reduced surge possibility
    • Reduced frontal area with enhanced flow per unit volume
    • Reduced noise level
    • No weight penalty

    Materials for Blades

    • Wide-chord fan blades often use a titanium honeycomb and titanium sandwich construction.
    • This design allows for superior performance without additional weight.

    Multi-Spool Engine Advantages

    • Higher compressor ratios
    • Quick acceleration due to less spool inertia
    • Less total weight due to fewer stages/smaller pools
    • Better stall characteristics control

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    Chapter 3 Compressor PDF

    Description

    This quiz delves into the fundamentals of compressors, outlining their purpose and various types such as centrifugal and axial flow compressors. It discusses performance evaluations and contrasts advantages and disadvantages of centrifugal flow compressors, emphasizing their components and operational considerations.

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