Lecture 1 - Intro Flashcards
(41 cards)
What drives the compressor, and how?
The turbine.
They are on the same driveshaft.
Sometimes through a gearbox.
What does the turbine generate power from?
Generates power from a hot, high-enthalpy exhaust (gas).
What is enthalpy?
Energy
Where do you inject your fuel into the jet engine? What happens then (in the combustion chamber)?
Combustion chamber. Temperature and enthalpy of fuel increases.
How much power is extracted from the turbine? Why?
Just enough to run the compressor, and no more.
Because one wants a high enthalpy leaving the turbine that can be converted into kinetic energy, to give thrust.
How is thrust created? (3 points).
Rate of change of momentum of working fluid.
Engine accelerates working fluid.
Results in exhaust jet having high Ek.
Momentum Thrust equation
What are 2 parts of thrust?
Momentum thrust and pressure thrust.
What is a choked nozzle?
A flow of Mach 1 in a nozzle.
Why can you sometimes have a pressure thrust?
If the nozzle is choked, and therefore flow is at Mach 1, the pressure out of the nozzle may not be atmospheric (higher, so thrust produced).
What do rocket engines carry?
Fuel and oxidant in tanks
Where are the fuel and oxidant in a rocket engine injected?
Combustion chamber.
What happens to combustion products in rocket engines?
Enthalpy release accelerates the combustion products to supersonic speeds.
How is thrust basically produced in a rocket engine?
Change of momentum
What is pumped into the combustion chamber of a liquid-fuelled engine and how?
Turbine drives pumps that pump fuel and oxidant into combustion chamber at high pressure and high volume flow rates.
How does fuel and oxidant enter the combustion chamber of a liquid fuelled engine?
Atomised in the entrance to the CC so mixed. Combustion then takes place.
What is fuel and oxidant also used for in engines?
To cool the rocket engine nozzle.
Approximate temperature of liquid fuelled engine?
2500k
Approximate nozzle exit velocities of liquid fuelled engines?
4km/s
What is the most powerful form of propulsion today?
Rocket engines
What’s one example of a difference in design between jet and rocket engines?
Jet: subsonic turbines
Rockets: supersonic turbines
What are you aiming to broadly do in a rocket engine?
Getting fuel and oxidant to highest possible pressures so that when injected into combustion chamber (where they burn), the temperatures are as high as possible to give the highest possible enthalpy.
Combustion chamber and nozzle are there to convert that into highest possible kinetic energy for highest exhaust velocity and therefore thrust.
Property of solid propellant rocket motors? (4)
- Storage of propellant?
- Propellant grains?
- Ignition properties?
- Propellant path?
Propellant is stored directly in CC of the motor.
Propellant grain forms the shape of the chamber.
Once ignited, can’t be throttled down or shut down.
Propellant burns radially outwards and gases flow axially down the engine towards nozzle.
Where are the rocket boosters in the space shuttle?
Either side of the centre tank, which contains the fuel and oxidant.
