Engines Ch.1

Front 1

Explain the relationship between static pressure, dynamic, and total pressure

Back 1

Static pressure: the potential energy of fluid molecules at rest (pressure)
Dynamic pressure: kinetic energy of fluid molecules in motion. (velocity)
Total pressure: the sum of pressure and velocity
Tp=Ps+q
Static and Dynamic are inversely related

Front 2

State Bernoulli's Theorem

Back 2

As any incompressible fluid passes through a convergent opening its velocity increases and pressure decreases.

Front 3

Describe the behavior of subsonic airflow in a nozzle and diffuser

Back 3

Subsonic:
Nozzle: Pressure decreases, Velocity increases
Diffuser: Pressure increases, velocity decreases

Front 4

Describe the behavior of supersonic airflow in a nozzle and diffuser

Back 4

Supersonic:
Nozzle: Velocity increases, pressure decreases
Diffuser: Velocity decreases, Pressure increases

Front 5

Identify the three main sections of a gas generator.

Back 5

Compressor
Combustion Chamber
Turbine

Front 6

Describe the Brayton cycle

Back 6

Brayton Cycle: consists of four events which occur simultaneously: intake, compression, combustion, and exhaust.

Front 7

Describe the basic components and operation of the gas generator.

Back 7

Gas generator: produces the high-energy airflow necessary for creating thrust.
components
Turbofan: fan
Turboprop: prop
Turboshaft: rotor blades
components play a vital role in producing thrust

Front 8

Describe how pressure, temperature, and velocity changes through each section of a gas turbine engine.

Back 8

Inlet:
-Temperature increases
-Pressure increases
-Velocity decreases
Compressor:
-Temp increases
-Pressure increases
-Velocity increases
Diffuser:
-Temperature constant
-Pressure increases
-Velocity decreases
Burner:
-Temp increases
-Pressure decreases
-Velocity increases
Turbine:
-Temperature decreases
-Pressure decreases
-Velocity increases
Exhaust:
-Temp decreases
-Pressure decreases
-Velocity increases

Front 9

Describe gross thrust and net thrust.

Back 9

Gross thrust: a mesurement of thrust due solely from the velocity of the exhaust gases.
Net thrust: thrust that corrects for the effect of inlet airflow velocity
Net thrust=m((Vfinal-Vinitial)/time)

Front 10

Describe how atmospheric temperature effects thrust in a gas turbine engine.

Back 10

As air temp. increases, air molecules tend to move apart, resulting in decreased density, and a decrease in thrust.

Front 11

Describe how atmospheric pressure effects thrust in a gas turbine engine.

Back 11

As air pressure increases, air molecules tend to move closer together, increasing density, increasing thrust.

Front 12

Describe how altitude effects thrust.

Back 12

increasing altitude decreases thrust because a pressure drop is greater than a temperature drop.

Front 13

Describe the effect of airspeed on thrust.

Back 13

Increasing velocity decreases thrust. As inlet velocity,Vinitial, approaches the exhaust velocity, Vfinal, thrust is reduced.

Front 14

Identify the cockpit instrument that measures thrust in a typical turbojet, turbofan, turboprop, and turboshaft.

Back 14

Turbojets and Turbofans:
Engine Pressure Ratio (EPR) gauge
Propeller or Rotor Driven:
Torquemeter

Tachometer (most commonly used by pilots to determine engine performance)

Front 15

Describe the effect of Ram effect on thrust.

Back 15

Factors affecting thrust:
mass and difference of Vinitial and Vfinal
Although increasing the airspeed decreases the difference of Vinitial and Vfinal, Ram effect pushes more air through, increasing the mass and pressure, offsetting the decrease in acceleration, giving neutral thrust or a slight increase in thrust at subsonic speeds.