15.1 - Fundamentals Flashcards
What is Entropy?
A quantitive measure of energy unavailable to do work (energy lost in a system). It always increases.
What are turbofan engines also known as?
Bypass engines
What is Boyle’s law?
The volume of a given mass of gas at a constant temperature is inversely proportional to pressure.
What is Charles’ law?
The volume of a given mass of gas at constant pressure increases 1/273 of its volume at 0°C for every 1°C rise in temperature.
What is an isobaric process?
One of constant pressure
What is an isothermal process?
One of constant temperature
What is an isochoric process?
One of constant volume
What is the equation for potential energy?
E = mgh
What is the equation for kinetic energy?
E = 1/2 mv^2
What is the equation of force?
F = ma
What is one metric horsepower equivalent to?
736watts or
736J/s (joules per second)
The power required to lift 75kg, 1 metre in 1 second
What is the equation for work done?
Work done = force x distance
What is Newton’s first law of motion?
A body at rest stays at rest unless acted on by an external force
What is Newton’s second law of motion?
The rate of change of momentum of a body over time is directly proportional to the force applied (F=ma)
What is Newton’s third law of motion?
To every action there is an equal and opposite reaction.
What is the Brayton cycle also known as?
The gas turbine cycle
What is the universal gas law?
P1 V1 P2 V2
T1 T2
What is the Brayton cycle?
The gas turbine cycle. A cycle of continuous combustion. The pressure only marginally drops during combustion. The pressure changes are caused by changes in the velocity of the air.
What does a convergent duct do to subsonic gas?
Increase velocity, decrease static pressure
What does a divergent duct do to subsonic gas?
Decrease velocity, increase static pressure
What is a choked nozzle?
The one exception to the gas flow rules. When the gas is flowing at the speed of sound (sonic velocity) just before it enters a divergent duct; it is impossible to increase the speed any further to supersonic and the nozzle is said to be choked.
Approximately how much nitrogen is in a parcel of air at sea level?
12 PSI of nitrogen
What is the equation for thrust?
F = W(Vjet - Vflight)
What is adiabatic compression?
Compression without the loss or gain of heat
Where is the diffuser located?
It’s located between the compressor section and the burner section
What is the working fluid of a gas turbine engine?
Air
What happens to air density if pressure and temperature remains constant, but humidity increases?
It decreases (less thrust can be produced)
Which law relates to the kinetic, pressure and potential energy in a fluid flow?
Bernoulli’s theorem
What is the purpose of the diffuser in a jet engine?
It increases the static pressure of the air before combustion
What is the density of gas expressed as in regards to weight and volume?
Density = Weight/Volume
What is the purpose of a waisted drive shaft?
It provides a fuse if the driven component is overloaded
What is 1 CHU equal to in ft. lb?
778 ft.lb
If the LP shaft shears, what happens to the turbine?
Turbine runaway occurs
What does Nf indicate in a free power turbine dual axial flow compressor system?
Free power turbine speed
Which section provides proper mixing of the fuel and efficient burning of the gases?
The combustion section
How is the turbine shaft usually joined to the compressor rotor of a centrifugal compressor?
By a splined coupling
What part of a jet engine has the most POTENTIAL energy?
Just before the combustion chamber
Where is the highest PRESSURE in a gas turbine?
Just after the last compressor stage, just before the burner
What part of a gas turbine engine produces the most amount of DISCREET noise?
The turbine
As an aircraft climbs, what factor IMPROVES with altitude?
The specific fuel consumption
What, on an aircraft makes an engine’s compressor stall more likely to be induced during rapid altitude changes?
Engine intakes mounted close to the fuselage
Why is a modular engine more favourable?
It provides total interchangeability of all modules
What happens to pressure, temperature and velocity of air in the turbine stages?
Temperature, velocity and pressure decrease
