Test 2 Review Flashcards
Whats happening to the air in the diffuser?
Increase pressure
Stagnate Velocity
How do we turn potential energy, into KINETIC energy?
Fuel + Ignition into the air mixture
Where is the largest amount of kinetic energy found?
The OUTLET of the COMBUSTION chamber (Acceleration)
What makes up the single stage of a compressor?
Inlet guide vane
Rotor
Stator
What do we call the last stage stators, and what do they do?
Exit Guide Vanes
STRAIGHTEN airflow going into diffuser
Function of a compressor STATOR?
Increase pressure, decrease velocity
due to its DIVERGENT shape
What do we want CONSTANT in the COMPRESSOR? How do we get it?
Constant VELOCITY
We get it by the CONVERGENT shape from inlet to end (blades get SMALLER)
What is it called when the blade AOA exceeds the critical AOA, caused by an IMBALANCE between the INLET and ROTATIONAL velocities
COMPRESSOR STALL
What can happen if we leave a stall unchecked?
hung stall/SURGE = damage
What is a compressor surge?
huge build of of PRESSURE released quickly through the front and back of engine
When the aircraft is flying, what are the ways STALL/SURGE can occur?
airflow DISRUPTED/TURBULENT to engine
RAPID engine acceleration/deceleration
If you’re in a high power setting and you feel a stall coming, what should you do?
Decrease power
IGV
Control Bleed Valves
Variable stators
How do we fix a dirty engine?
Compressor wash (fluid/grit blast)
Turbo prop and turbo shaft use what type of compressor?
Centrifugal
Control bleed, what are do we get it from?
Mid section of Comp and diffuser
What areas do we target with compressor bleed air?
Starting engine Cabin Pressurization Cooling/Heating Engine Cooling Pressurization of reservoir Pumps ANTI ICE
What do we use ram air for?
Engine Gen. Cooling
Why do compressor blades have a twist?
for EVEN acceleration of air across the blades
What are the types of blade root designs?
Dovetail
Fir Tree
Bulb root
What are the purpose of blade root designs?
Radial movement (centrifugally)
How do we protect from axial movement?
rivet
lock wire
lock tab
What are the disadvantages of Axial Flow Compressors?
high cost
complex
high weight
What are the disadvantage of a Centrifugal Compressor?
heavy
LIMITED compression ratio
Compressor blades and discs are manufactured as a single assembly called what?
BLISK (blade integrated disk)
Differential pressure between the rotors and stators caused by the camber of the blades is called what?
Cascading Effect
What is cascade effect?
The process of involving velocity and pressure changes through several stages of compression
When replacing the fan blade, what do you do?
Replace the one 180 degrees across it
First stage of compressor stator are called what?
IGV
What is the purpose of BLADE PROFILING?
reduce THICKNESS towards the the TIP to reduce VIBRATION (nat. frreq.)
Purpose of the DILUTION HOLES?
Cools the flames before the nozzle guide vanes and turbines
What to Ceramic Matrix Composites do? (CMC)
Increases thermal efficiency = increase propulsion efficiency
What are the 2 functions of PRE SWIRL VANES?
- Reduce Velocity
2. Swirl fuel spray for better atomization = efficiency
What provides a path to spread the combustion evenly for a MULTI Can Combustor?
Flame propagation tube
What are the 3 different type of Combustion chambers?
Annular
Can-Annular
Multi Can
What type of airc. do we use a Reverse Flow Annular?
PT6 engine
Helicopter
Turboprop
What type of TURBINE for centrifugal flow compressor?
Radial Inflow
What are the 2 types of TURBINES?
Radial Inflow
Axial Flow
What is the purpose of the gas turbine?
Drive the compressor
Gearbox
Accessories
What are the 2 designs of TURBINE STATORS?
- direct air at ANGLE to TURN turbine ROTOR
2. increase velocity (CONVERGENT STATORS ONLY)
Where do we find convergent stators?
TURBINES
What are the types of Turbine Blades?
Impulse
Reaction
Impulse-Reaction
Impulse is?
Convergent stators
Reaction is?
Straight through stators
Is density DIRECTLY proportional to thrust?
Yes
What will the gas turbine do on a turboshaft/turbo prop engine?
drive the compressor
accessory
gearbox
What is the reduction gearbox driven by?
free turbine
Engine airflow stations
Tt, Pt, Ps
Purpose Vortex generators
smoothen airflow going into compressors
Advantage of modular engine design?
Reduced maintenance cost
Purpose of the holes in turbine stator/ rotor blades?
Convection/film cooling
