Turbine Engine Fundamentals

These flashcards cover key concepts, definitions, and explanations related to turbine engine fundamentals and their various systems.

What describes the requirement of Reliability in Turbine Engines?

Ensured by manufacturer testing and monitored procedures.

What is the role of a Convergent-divergent Duct in Turbine Engines?

It causes an increase in gas velocity, creating propelling nozzle thrust.

How is Kinetic Energy defined in relation to Turbine Engines?

Dynamic pressure (pressure from moving fluid).

Which factor is NOT a reason for why Thrust is needed for flight?

To overcome aircraft weight.

What describes the principle of Pressure Energy in Turbine Engines?

Static pressure (pressure of an unmoving fluid).

What is Newton's 3rd Law of Motion?

To every action, there is an equal and opposite reaction.

What is Newton's 2nd Law of Motion?

Force = mass × acceleration.

What must we understand to comprehend jet engine propulsion?

The laws of Physics for Masses & Gases.

What describes the requirement of Durability for Turbine Engines?

Engine lasts long before overhaul.

What is meant by Operating Flexibility in Turbine Engines?

Operate seamlessly from idle to full power.

How is Total Energy measured in Turbine Engines?

Measured by a Pitot tube.

What is the Engine Pressure Ratio (EPR)?

The comparison between engine exhaust pressure and compressor inlet pressure.

What does the Brayton Cycle represent?

Combustion is a continuous cycle.

What does the Otto Cycle represent?

Combustion is an intermittent cycle.

Which engines are considered Thrust producing?

Turbojet and Turbofan engines.

What separates the airflows in a Turbofan engine?

Primary (core) and secondary (bypass) air.

What are the two categories of Turbine Engine types?

Non-air-breathing (rocket) & air-breathing reaction.

Do Non-air-breathing engines carry their own oxidizers?

Yes, rockets carry oxidizer.

Is a Turbojet a jet engine with an output shaft driven by the turbine section?

False; that describes a turboshaft.

Which engines are Torque producing?

Turboprop and Turboshaft.

What are the separate turbines in a Turbofan Jet Engine responsible for?

Driving a fan to produce thrust.

What is 'Ram Recovery' in the context of air inlets?

Convert velocity to pressure at compressor face.

What is the primary purpose of stator blades in axial flow compressors?

Direct air to the next rotor stage.

What is the function of air inlets in gas turbine engines?

Deliver air to the compressor at optimal velocity and pressure.

What do the blades in the compressor section consist of?

Stator and rotor blades form divergent passages.

How do reciprocating engines differ from turbine engines?

Reciprocating = Otto; Turbine = Brayton.

What factor does NOT affect airflow through a turbine engine?

Throttle position in the flight deck.

What are common methods of rotor blade attachment?

Solid root, dovetail root, fir tree.

Where is warm air bled from to prevent inlet/IGV icing?

From the Compressor.

What is the primary function of compressors in gas turbine engines?

Provide high-pressure air for power and services.

What is referred to as the Compressor pressure ratio?

The ratio of inlet to outlet pressure of a turbine engine.

Where is the diffuser located in a gas turbine engine?

Between the compressor and combustion section.

What is the main pollutant in gas turbine exhaust?

Oxides of nitrogen (NOx).

What is the primary function of the diffuser in the combustion process?

Reduce velocity, increase pressure of compressor discharge air.

What is the purpose of tertiary airflow in combustion?

Cool gases for the turbine.

What are the perforations in the combustor liner designed for?

Flame distribution.

Which arrangement is NOT a basic arrangement of combustion chambers?

Axial-flow system.

What percentage of airflow is tertiary?

40% (cooling/film).

What combustion chamber system is known for its shorter length and efficient emissions?

Annular system.

What is the typical air/fuel ratio for efficient burning?

15:1.

What percentage of primary airflow is used for combustion?

20%.

How is thrust primarily obtained in a turboprop engine?

90% propeller, 10% residual jet.

Why is active blade tip clearance control important?

To maintain the smallest possible positive clearance.

What is the purpose of shrouds at turbine blade tips?

Minimize gas leakage; allow thermal expansion.

What advantage does cast Nimonic alloy provide to turbine blades?

Corrosion resistance and high-temperature strength.

Where is the impulse section located on a turbine blade?

At the root.

How is turbine blade casing expansion with temperature controlled?

By a cooling air supply system automated by FADEC.

What is the primary purpose of the turbine assembly?

Drive the compressor section.

Which blade attachment allows movement for thermal expansion?

Fir Tree.

Which exhaust section produces maximum thrust for turbojet engines?

Exhaust section.

What are the three types of turbine blades?

Impulse, Reaction, Reaction-Impulse.

What does 'creep' mean in turbine blades?

Continuous extension under load/heat.

What type of bearing handles only radial loads?

Roller bearing.

What is the purpose of a secondary air seal?

To prevent oil fires, reduce wear, improve cooling.

Which system provides cooling air to the bearings?

Lubrication system.

Which bearing can handle both radial and axial loads?

Ball bearing.

What type of seal self-machines for tight clearances?

Abradable seal.

What creates pressure to force oil toward the bearing across the primary seal?

Screwback seal.

What provides cooling and lubrication for engine bearings?

Oil jets.

What type of seal allows shaft rotation while retaining oil?

Labyrinth seal.

What is a characteristic of a fixed pitch propeller?

Has only one pitch setting.

Which Newton's law explains propeller thrust?

Newton's 3rd law.

What is the primary function of a propeller?

Convert engine torque into thrust via rotating blades.

How do turboprop turbines differ from other gas turbines?

Turboprop includes additional stages for enhanced energy extraction.

What is the typical shaft horsepower range for turboprop engines?

500–2,000 shp.

What is the core functionality of the Gas Generator in a turboprop?

Air intake, diffusers, combustors, turbines to drive compressor.

What does the reduction gear assembly in a turboprop do?

Reduce engine rpm to propeller speed.

What is the key difference between fixed and free turbines?

Mechanical connection of power turbine to gas generator.

What are the main components of a turboprop engine?

Compressor, combustors, turbine, exhaust nozzle.

What common feature is found in the reduction gear assembly?

Propeller brake to prevent windmilling when feathered.

How are turboshaft engines typically rated?

Shaft horsepower (shp).

How is a free turbine typically driven?

By exhaust gases (not mechanically linked to gas generator).

What is a common application of turboshaft engines?

Helicopters and APUs in large aircraft.

What do gimbal and flanged couplings function as?

Torque reaction points.

How is turbine speed controlled?

By adjusting fuel flow.

What component reduces speed from high rpm to rotor speed in turboshafts?

Main rotor gearbox.

Which part of the turboshaft is driven by the engine turbine?

The output shaft.

What are the stages of the Allison 250 compressor section?

Two-stage axial and two-stage centrifugal.

What gearing is needed at turboshaft output drive?

Reduction gearing.

What is the role of couplings in turboshaft engines?

Allow independent movement of engine and rotor gearbox.

What is critical for fine balancing in turboshaft engines?

Minimization of vibration.

Which engines share similar principles/designs with turboshafts?

Turboprop engines.

What does the free turbine contribute to operation?

Enabling optimal speed management.

What does the reduction gearbox do in the Allison 250?

Reduce turbine rpm for rotor/blades.

What material is used mainly in Thomas coupling?

Steel discs.

What is the primary difference between turboshaft and turboprop engines?

Turboshaft delivers shaft power for non-propulsive uses.

What does the combustion section in the Allison 250 engine consist of?

Single reverse-flow stainless steel combustor.

What is the primary function of the turbine section in the Allison 250 engine?

Houses bearings for radial support.

What gear train is used in the Rolls Royce Gem Engine?

Two-stage epicyclic gear train.

Which component compresses air and sends it to the combustor?

Compressor section.

What does 'Engine Cold Soak' refer to?

APU inactive in cold temps for extended time.

What services do APUs generate power for?

Pneumatics, Electrical, Hydraulic.

From which stages is Engine Bleed Air Supply taken?

Both HP and IP stages.

What are sources of hot pressurized air for the bleed system?

Engine, APU, Ground air source.

Where is the Allison-Signal APU located on Boeing 777?

In the tail cone with rear side exhaust.

What does the Air/Oil Heat Exchanger do?

Cools lubrication oil.

What start methods exist for APUs?

All are correct: Electric 28 VDC, Pneumatic starter ~22 psi, Main engine air.

What does the Air Bleed Leak Detection System logic entail?

A detected duct leak closes that duct.

Where is the location of the 777 APU fuel system and pump?

Left wing, DC pump fuels the APU.

What is NOT a valve close condition for Engine Bleed Air Supply System?

Cabin pressure loss.