Aircraft Gas Turbine Engines and Systems

Flashcards from lecture notes on aircraft gas turbine engines and related systems.

Pressure regulator/ unloader valve

Works in conjunction with constant displacement pump to maintain a set pressure by diverting excess pump flowback

Shape of the inlet of a supersonic aircraft

Converging-diverging

Three types of combustion chambers

Can, Annular, and Can-Annular

Three parts does a gas turbine engine have at a minimum

Compressor, Combustion Chamber/Burner, Turbine

Gas turbine engine parts

Inlet, Compressor, Diffuser, Combustion chamber/burner, Turbine, exhaust

Negatives to a turbofan engine

Reduction of airflow to the turbines, Higher specific weight, larger frontal area, inefficient at high altitudes

Negatives to a turbofan engine

Reduction of airflow to the turbines, Higher specific weight, larger frontal area, inefficient at high altitudes

Pressure regulator/ unloader valve

Works in conjunction with constant displacement pump to maintain a set pressure by diverting excess pump flowback

Shape of the inlet of a supersonic aircraft

Converging-diverging

Three types of combustion chambers

Can, Annular, and Can-Annular

What three parts does a gas turbine engine have at a minimum

Compressor, Combustion Chamber/Burner, Turbine.

What parts can also be included in a Gas turbine engine

Inlet, Compressor, Diffuser, Combustion chamber/burner, Turbine, exhaust

What are the negatives to a turbofan engine?

Reduction of airflow to the turbines Higher specific weight, larger frontal area, inefficient at high altitudes

Units is the torquemeter measured in?

Measured in inch pounds of torque

Positives of a turboprop engine

~0% thrust from exhaust ~100% from the free power turbine. High thrust at low airspeeds and lowest TSFC

Percentage distribution of thrust for a turboshaft engine

~0% thrust from exhaust ~100% from the free power turbine

2 systems associated with a hydraulic system and what do each supply fluid pressure to?

Power Control System: Flight controls only. Utility Control System: Utility system and flight controls

2 most important considerations of designing a fuel system?

High rates of fuel flow and low atmospheric pressure

What does a fuel pump do?

Submerged in the fuel tank, it ensures an adequate supply of fuel to the engine-driven fuel pump

Volatility

Ability of a liquid to evaporate

Oil pump

Supplies oil under pressure

One stage of a compressor

rotor blade and a stator blade

Bernoulli's Equation

Pt=Ps+Pk

Hand pumps

Emergency systems

Inlet duct designed to act like a ?

diffuser

Parts of a turboprop engine

Gas generator, reduction gear box, torquemeter, and propeller

2 parts of AC

AC generator (alternator) and inverter

Advantages and disadvantages of a Can-Annular combustion chamber

Very efficient engine type. Very expensive

Relationship between viscosity and temperature?

Inversely related

What does a filter do?

Ensure the delivery of containment free hydraulic fluid

variable exhaust nozzle

Way of changing the nozzle to create a convergent-divergent shape needed for supersonic speeds

Colors of Avgas 100 and Avgas 100 LL

Green and Blue

Relationship between linear displacement and the change in force between input and output pistons of a closed system

Linear displacement is inversely proportional to the multiplied force

Order the TSFC of the all of the engines in order from lowest TSFC to highest

Turboprop, Turbofan, Turbojet

At sea level, what position is the valve in in the breather pressurizing subsystem?

Open

Explain what happens at each of the events in the Otto cycle

Ambient air density Intake: Air is entering the valve while the piston is at the bottom. Compression: The pressure is increased as the piston moves up. Combustion: Spark ignites the air and sends the piston down. Exhaust: the valve opens to release the air and start the cycle over

Where does the oil pressure relief valve bypass oil back to?

Pump inlet

3 types of compressors?

Centrifugal, axial, axial-centrifugal

Purpose of the hydraulic system

Provide mechanical advantage by multiplying force for the operations of various mechanisms

Four mechanical malfunctions that can lead to a compressor stall?

Fuel control unit, FOD

Four engine design features that can be incorporated to minimize the potential for a compressor stall

Variable inlet guide vanes, Dual/twin/split-spool compressors Bleed Valves Variable exhaust nozzle (VVFF…. Very very funky functions)

Monitor/ Secondary bus

Routes power to convenience circuits

Torquemeter assembly

Transmit and measure power output from the gas generator to the reduction gear box. Parts are the torque shaft (carries load from prop and measures twist) and the reference shaft

Purpose of the exhaust section

Direct the flow of hot gases rearward, causing a high exit velocity of the gases while also preventing turbulence

Shape of the inlet of a subsonic aircraft

Diverging shape

EPR

Engine pressure ratio. It measures the pressure ratio between the inlet and exhaust airflow

Diffuser do in an axial-centrifugal flow compressor?

Prepares the air for entry into the burner. Preheats metered fuel and cools engine lubricant as it flows from the engine

JP-4's flashpoint

-35F

Hung Start

High ITT, low RPM

magnetic chip detector

Magnetized detector to collect metal. Warning light

JP-5's flashpoint

140F and low Volatility

Alpha range

Idle to forward (plane moves forward)

Cockpit thrust measuring devices?

EPR (Engine Pressure Ratio) gauge, Torquemeter, and Tachometer

RPMs measure in the FCU

Compressor speed

bypass valve

Allows hydraulic fluid to flow in case of a clog. Filter

A diffuser ?

Converts high velocity airflow to high pressure

What do Fuses do and how are they controlled

Automatic. Circuit protection if an over-load or excessive current is flowing through something

Relief valve

Prevent excessive build up in the system. Valve opens and allows for backflow

Velocity and Pressure in a nozzle

Pressure decreases, velocity increases

Where is the oil temp gauge measuring?

oil entering engine bearing compartments

What happens during a normal start?

ITT and PRM rapidly increase then stabilize within limits

Fuel temperature sensing switch?

Tells the air cooler to open up to let fuel through to cool it further if needed heats the fuel for combustion and allows bypass of oil if no cooling is needed

Battery is used for?

Starting an engine

Coking

Carbon diposits

Parts to DC

DC generator, transformer-rectifier, and a Battery

Constant displacement pump have?

pressure regulator/ unloader valve

Turboprop engine produce its thrust?

Propeller imparts a small acceleration to large mass of air

combat rated thrust?

Thrust produced when afterburner is in operation

How can FOD cause a compressor stall?

Damages the compressor blades

Shape of an incompressible air diffuser?

Divergent

Constant Speed Drive

Hydro-mechanical linkage between the engine and the generator

Auxillary power unit

Frees the aircraft from being dependent on external power. Provides power through a driveshaft

Impeller

Accelerates air outward toward the diffuser. Velocity and pressure are increased.

variable inlet guide vane

Maintains the velocity of air for changes in speed

Turbofan engine driven by?

By a free or power turbine or by attaching the fans to the compressor

Indications of a severe compressor stall?

Loud bang, RPM decrease, ITT increase, (LRI)

Rotor blades and stator vanes

variable inlet guide vane and stator vane

Compressor stalls usually the result of

Airflow distortion or mechanical malfunction

Pressure subsystem

Provides/supplies a constant supply of oil to engine bearings and accessory gear box

Manual operation

Allows PCL to act as a throttle which regulates fuel flow

Components of a turbofan

Increases the mass of the air (because of the ducted fan)

Creep

Blade elongation as the blades are heated cooled repeatedly over periods of time

Starter Bus

Power to start the aircraft's engine

Velocity and Pressure in a diffuser

Pressure increases, velocity decreases

Turbine Temperature,pressure,velocity

Air temperature increases due to compression, pressure remains relatively constant, and velocity decreases

Where is Energy converted to?

Energy is converted to SHAFT Horsepower, free power turbine

Bleed valve

Helps to vent off excess pressure and increases airflow to the front of the compressor at low RPMs

Dual/twin/split-spool compressor

Turbine helps the plane and compressor turbine just keeps the speed constant/ normal

Squeeze film

thin film preventing metal to metal contact and dissipates heat

Wet start

Fuel air mixture does not light off initially

Tachometer

Measured in percent RPM

Pascal's Law

Pressure applied to a confined liquid is transmitted equally in all directions without a loss in pressure and acts with equal force on equal surfaces

Burner

Add sufficient heat energy to accelerate the gases to produce the desired thrust.

Fuel Control Unit

Too much fuel can cause excessive burning which leads to excessive pressure. This pressure could result in backflow to the compressor. too little fuel, flame goes out

Beta range

Idle to max reverse PCL. Plane goes backwards

FCU

Starting point for the fuel

Axial flow compressor

pressure builds as it goes from front to back of an axial flow compressor

DC generator & Annular

Unloads pressure during afterburner operation, Converts mechanical energy to electrical Most ignitors

Air starter and aircraft

Air is directed to the air turbine which accelerates the compressor. Larger PON-6 or bowser, pressure tank

RAM

As the aircraft goes faster, more and more air is being rammed into the inlet. This increases the mass and pressure of the inlet air causing better engine performance SHRIMP