A.A.B Engines - Tutorial Flashcards
Draw limiting cycles of ramjet. Include low and top speed limit
T-S graph.
dotted lines showing limiting cycles
What are the losses in a real ramjet
- Intake, combustor and nozzle have pressure losses
- Losses occur during combustion
- Compression and expansion are not isentropic
- Irreversibilities result in flight and exhaust Mn to be different
Discuss challenges of SR-71 has when flying at M=2 on ground level
- Ambient pressure is higher at ground level so higher friction as body moves through air
- Diffuser performance decreased due to increased pressure of atmosphere
- Shock waves could interact with ground and reflect back to aircraft causing issues
- Speed of sound is faster
Describe why rocket combustion is more controllable than scramjet combustion
Rocket:
- simple design using solid propellant as fuel
- do not need to control air intake so combustion stays the same no matter the speed
- can be used at any altitude
- can start from initial velocity of 0
Scramjet:
- must be travelling at supersonic speeds
- has to use full aircraft frame to control air intake
- blowout limit issues
- high speeds mean high heating so a lot of cooling required
- highly sensitive system
- thermal management limit
Draw scramjet design
PIC
Discuss pro’s and con’s of SABRE concept
Pros:
- Cooling inlet air means higher density
- Lower temp means lighter alloys can be applied
- Can transition between air breathing and pure rocket
- Expansioin deflection nozzle achieves altitude compensation and reduces performance losses
- Can be tested on the ground
Cons:
- It has to use cryogenic fuels
- Complex design and heat exchanger
Describe difference between pulse jet and PDEs
- Pulse jet combusts using deflagration, PDEs uses detonation
- PDEs - pressure increases significantly more during combustion
- PDEs is supersonic combustion, Pulse jet is subsonic
- Detonation transfers heat via shock, Pulse jet is conduction
Why can pulse jet start from static and ramjets can’t
Pulse jet:
require subsonic air inlet flow which is possible from static
Ramjets:
require supersonic air inlet flow for combustion
Draw T-S diagram for pulsejet
stages 3-4 entropy stays constant (vertical line)