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Aeronautic Propulsion Systems > Engine Components > Flashcards

Engine Components Flashcards

1
Q

What are the 4 purposes of an intake?

A
  • Guide air
  • Set the right velocity & pressure of inlet air
  • Minimize pressure loss, low distortion
  • Static pressure rise by flow deceleration
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2
Q

What are 3 challenges of intakes?

A
  • Separation (high-pressure gradient)
  • Non-uniform or distorted flow may cause compressor surge
  • Create drag as low as possible
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3
Q

What are the 2 intake types?

A
  • Subsonic flight
  • Supersonic flight
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4
Q

What are 4 properties of subsonic intakes?

A
  • Rounded edges, relatively short arrangement
  • Low static pressure rise
  • Low total pressure loss
  • Causes distortion to fan and compressor at high incidence or cross-wind (moderate aerodynamic interaction of intake and compression components)
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5
Q

What are 5 properties of supersonic intakes?

A
  • Sharp edges, long and potentially variable arrangement
  • High static pressure rise
  • High total pressure loss
  • Causes distortion to fan and compressor at any flight
    condition (strong aerodynamic interaction between
    intake and compression components)
  • Can develop intake buzz
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6
Q

What are the 2 purposes of a fan?

A
  • Efficient thrust generation
  • High Bypass Ratio
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7
Q

What are the 6 purposes and properties of a propeller?

A
  • Convert Shaft torque to thrust
  • Turbine provides shaft power to the gas generator
  • Very large BPR between 30-100
  • Higher propulsive efficiency
  • Cruise Ma 0.4-0.6 and 0.7-0.8 for advanced configurations
  • Reduction gearbox required (increase engine weight)
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8
Q

What is the primary and secondary purpose of a compressor?

A
  • Primary: Increase pressure of air mass, delivery at
    correct velocity, temperature, and pressure
  • Secondary: Supply engine with bleed air
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9
Q

How does a compressor work?

A
  • Acceleration of working fluid
    followed by diffusion
  • Transforms kinetic energy to pressure
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10
Q

What are the 3 design targets for a compressor?

A
  • Increase stage pressure ratio (PR)
  • Increase efficiency
  • Maintain trouble free function (surge)
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11
Q

What are the 2 types of compressors?

A
  • Radial compressor
  • Axial compressor
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12
Q

What are the advantages and disadvantages of radial compressors?

A

+ Robust
+ Easier to develop / manufacture
+ High PR per stage
+ Good efficiency for a wide RPM range
+ Low weight
- Large frontal area for given mass flow
- More than two stages are not practical

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13
Q

What are the advantages and disadvantages of axial compressors?

A

+ More Air for same frontal area → Higher
thrust
+ More stages → higher PR and lower drag
+ High peak efficiencies
- High cost
- High weight
- Lower PR per stage

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14
Q

What are the 2 purposes of multi-spool design?

A
  • Increases design operation flexibility
  • Varying LPC output provides the HPC with the best inlet conditions within the limits of its design
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15
Q

What are the 4 purposes of a combustion chamber?

A
  • Prepare and burn air-fuel mixture to facilitate the addition of heat
  • Increase total temperature via intensive heat input to flow
  • Serve the engine cycle: Add heat in the core between
    compression and expansion
  • Large working range: 0,3 to 45 bar, -30 to 1750 °C
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16
Q

What are the main parts of a combustion chamber?

A
  • Outer casing
  • Inlet diffuser (HPC interface)
  • Inner casing (protect HP shaft)
  • Fuel nozzles
  • Igniters
17
Q

What are 4 important design details of a CC?

A
  • Low Mach Number entry flow
  • Fuel injection
  • Fuel/air mixing
  • Multi-zone combustion to achieve low
    emissions
18
Q

How is efficient combustion achieved?

A
  • Proper mixing
  • Stable burning
  • Cooling of hot combustion products down to an adequate level for HP turbine parts (TET limit, HPT interface)
19
Q

What are 10 design criteria for a CC?

A
  • Stable combustion process over a wide range of pressures
    and temperatures under all conditions (e.g., humidity, rain,
    hail, birds …)
  • Adequate re-light capability on the ground and at altitude
  • Low noise and avoidance of acoustic phenomena such as
    „Buzz“ and „Rumble“
  • Complete combustion (>99 %)
  • Low total pressure loss
  • Rapid quenching (rapid air addition), low pollutant emissions (NOx, Soot,
    CO, UHC)
  • Reasonable wall temperature, long parts life (controlled crack formation and
    propagation)
  • Optimum temperature distribution at the exit to permit turbine life
  • Minimum volume, length, and weight (aero engines)
  • Low design and maintenance cost
20
Q

What are 4 design goals of a CC?

A
  • Maximize heat release
  • Minimize size
    requirements
  • Reduce fuel emission
  • Emissions
21
Q

What are 3 purposes of a turbine?

A
  • Satisfy thermodynamic cycle requirements across flight envelope (altitude and Manumber)
  • Facilitate the transformation of fluidic energy to mechanical/rotational energy
  • Provide work to compressor/shaft
22
Q

What are 7 characteristics of a turbine?

A
  • Located at the back of the engine
  • Significant LPT Reynolds number effects
  • Working with extreme temperatures and pressures
  • High aerodynamic loading at the highest efficiencies
  • Complex cooling systems
  • Complex part-life requirements
  • Continued strong demand for new high-temperature materials
23
Q

What is the turbine assembly of a 2-Shaft arrangement?

A
  • Low BPR engine hence little mean radius change
    through the turbine
  • 2-stage HPT (shrouded, cooled)
  • 3-stage LPT
    (shrouded, no blade cooling)
  • HPT stage 2 is similar to IPT in a modern 3-shaft
    engine
  • LPT stator vane 1 is a special design:
    • in a transition duct, including structural struts
    • to lead through oil supply
    • to allow borescope access
    • to accommodate temperature measurement
24
Q

What are 9 general design requirements of a turbine?

A
  • Design structure to form the inner and outer main gas path
  • Lead occurring forces into the rotor and the casing
  • Have sealing against hot gas entry and cooling flow leakage
  • Quantify turbine flow capacity: fix annulus and throat areas
  • Structural integrity of components
  • Meet Creep, Oxidation, and Fatigue requirements
  • Minimize weight
  • Allow cost-oriented manufacturing
  • Allow cost-oriented repair and overhaul schemes
25
Q

What are the 6 properties that describe a nozzle?

A
  • The sensitivity of engine net thrust to nozzle performance is
    higher than to any other engine components performance
  • Therefore, maximize nozzle performance with consideration
    of cost, weight, complexity, reliability, and maintainability
  • The type of nozzle is largely determined by the combination
    of engine aircraft and mission requirements
  • Fixed conical nozzles are the simplest variant (no moving
    parts, purely converging exhaust duct)
  • They are used for subsonic transport aircraft in common or
    separate nozzle arrangement
  • Variable nozzles are applied on engines, which require a
    large variety of nozzle exit areas, mainly as a consequence
    of afterburning (area increase of 50-150% )
26
Q

What are the 3 types of nozzles?

A
  • Nozzle + Mixing
  • Separate Jets / Nozzles
  • Variable Vector Nozzle
27
Q

What are 4 properties of Nozzle + Mixing?

A
  • Used for low/medium BPR
    engines to reduce hot jet noise
  • Improved overall nozzle
    efficiency
  • Long nacelle + bypass duct
  • Moderate impact of the nozzle
    on fan and core throttling
28
Q

What are 4 properties of Separate Jets / Nozzles?

A
  • Used for high BPR engines as
    the hot jet stream is low
  • Bypass nozzle efficiency
    improved using chevron edge
  • Short nacelle + bypass duct
  • Moderate impact of the nozzle
    on fan and core throttling
29
Q

What are 4 properties of Variable Vector Nozzles?

A
  • Used for afterburner
    supersonic flight engines
  • Variable mechanism to control
    throat area and thrust vector
  • External arrangement
  • Strong impact of the nozzle on
    fan and core throttling

Aeronautic Propulsion Systems (9 decks)

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