M15.01 Fundamentals Flashcards
What is the formula for force?
Mass time acceleration
In newtons
What is the formula for weight?
Mass time acceleration due to gravity
In newtons
What is work?
Work is done when an object is moved over a distance. It is force multiplied by distance
Force = force times distance
In Nm or joules
What is power?
Power is the rate of work
Power = work divided by time
In Watt
What are the two forms of mechanical energy
Potential
Kinetic
What is the formula for potential energy?
PE=mgh
What is the formula for kinetic energy?
KE = 1/2mV squared
What is Newtons first law?
Newton’s first law of motion is called the law of inertia. It states:
A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an unbalanced external force
What is newtons second law?
Newton’s Second Law
Newton’s second law of motion is the interplay between force and motion and allows us to analyse the motion of any object. Newton’s second law states:
That the acceleration produced in a mass by a force acting on it is directly proportional to the force and inversely proportional to the mass
What is Newtons third law?
Every action has an equal and opposite reaction. This means that no matter what the circumstances, when one object exerts a force on a second object, the second must exert an equal and oppositely directed force on the first
How does a gas turbine increase the velocity of the air?
To obtain the increased air velocity …
The pressure energy is increased
Addition of heat energy
Final conversion back to kinetic energy in the form of a high velocity jet efflux
What combustion process does a gas turbine work under?
Heating at constant pressure (Isobaric)
What is the name of a constant pressure process?
Isobaric
Wha t is the name of a constant temperature process?
Isothermal
What is the name of a constant velocity process?
Isochoric
hat are the disadvantages of a piston engine?
The performance of piston engines decreases at higher altitudes and they can be too large for the aircraft because the ratio of weight and power decreases with the size of the piston engines. Therefore, piston type engines are only used on very small aircraft
What principles do jet engines work under?
Reaction
How can air pressure be increased in a gas turbine?
Mechanically by use of a compressor or thermally by increasing the volume of air when a fuel / air mixture is burned or heated.
Engines use both of these mesures
What determines thrust in a gas turbine?
Mass of the ambient air which is accelerated, the other is the quantity of the acceleration itself
How is the airs acceleration determined?
By knowing the difference between the outlet velocity of the air at the jet nozzle compared to the inlet velocity
What are the four factors that create changes to an engines thrust?
The ambient air pressure
The air temperature
The operation altitude
The airspeed of the aircraft
What happens with high altitudes with relation to thrust production?
The colder air temperatures at higher altitudes give a small increase in thrust, but the decrease in thrust is greater because the decrease of air density is much bigger
Explain the effects of airspeed on thrust
As air speed increases, thrust decreases, this is because the difference between the efflux and the intake velocity decreases.
However This is somewhat negated by the fact that as airspeed increases so does the ram effect. the increased ram effect increases the thrust.
Therefore these effects are in fact a combination of the two.
On a turbo fan engine how do the fan propel the air?
High airflow to a relatively low outlet velocity
