Engine Flashcards
engine modules
cold section, hot section, turbine section, accessory section
cold section module components
inlet partical separator (IPS)
compressor
the output shaft assembly
line replaceable units (LRU)
Inlet Partical Separator (IPS)
removes foreign material from the engine inlet air, air passes through swirl vanes, directing air into a rotating pattern.
compressor
has five axial stages and 1 centrifugal stage that continuously pressurizes the combustion chamber, cools the hot section components and provides bleed air from three bleed ports at the 5th stage of the compressor case.
one port provides air to the anti ice start bleed valve the other 2 provide air to the pneumatic system and engine inlet anti-ice
Hot section Module components
gas generator (GG) turbine
stage 1 nozzle assembly
combustion liner
Power Turbine Section Module components
2-stage power turbine
exhaust frame
drive shaft assembly
C-sump housing
The power turbine converts …
gas pressure into rotational shaft energy to power the drive train
The seven thermocouple probes measure …..
the temperature of the gases between the Ng and Np turbine sections
Accessory Section Module
accessory gear box Hydromechanical unit (HMU) pressurizing and overspeed unit (POU) overspeed and drain valve (ODV) starter engine driven fuel boost pump oil filter oil cooler alternator oil and scavenge pump IPS blower fuel filter assembly chip detector oil filter bypass sensor liquid to liquid cooler oil temperature sensor fuel pressure sensor oi pressure sensor
Hydromechanical Unit (HMU)
High pressure pump - delivers fuel to the combustion chamber. The high pressure provides a precise spray pattern for good atomization. The vane pump can suction fuel from the fuel cell
Fuel flow metering/scheduling
HMU - Fuel flow metering/scheduling
LDS input
ECU/DEC/EDECU
PAS
HMU - LDS input
load demand schedule is manually adjusted by collective movements through the LDS. The collective link to this schedule proactively attempts to match engine power output to the main rotor load. This attempt is approximate and must be further adjusted by the ECU/DEC, via the torque motor
HMU - ECU/DEC/EDECU input
the torque motor acts as an interface between the ECU/DEC/EDECU and load dead schedule of the HMU. Trimming of the HMU reduces pilot load by electrically keeping Np and Nr constant (Np governing), keeping power output to the main rotor load. This attempt is approximate and must be further adjusted by the ECU/DEC, via the torque motor.
HMU - PAS input
maximum power available schedule is set by the PCL through the PAS. The PAS sets the maximum power limits that may never be exceeded by collective movement
HMU - Acceleration/decelaration fuel flow limiting
automatic mechanical function that prevents flameout due to rapid power changes. This limits the metering valve movement rate to prevent compressor stalls and engine flame out
PAS override function
the pilot may sever the DEC/EDECU to HMU interface by locking out the torque motor. Advancing the PCL to lockout mechanically blocks off the torque motors fuel control passage within the HMU. The three ECU/DEC functions have been locked out.
HMU - PAS override function
the pilot may sever the DEC/EDECU to HMU interface by locking out the torque motor. Advancing the PCL to lockout mechanically blocks off the torque motors fuel control passage within the HMU. The three ECU/DEC functions have been locked out.
HMU - Ng limiting
HMU can. mechanically compute/set the max Ng speed or it induces a physical limitation in which the metering valve is full open. Limiting depends on engine inlet temperature
Ng is limited to 103% Ng and in extreme cold conditions, less Ng is allowed. Ng governing may be entered prior to TGT limiting
Ng shutdown is the engine shutdown at 110% Ng to prevent destruction on Ng section and occurs when a mechanical Ng speed sensing mechanism stops all fuel to the engine when Ng speed reaches 110%
HMU other non fuel flow functions
Variable geometry positioning - varies the angle of attack of the inlet guide vanes
Vapor vent valve - allows pilot to manually prime the fuel system passages from the fuel cell to the HMU.
Overspeed and Drain Valve - ODV
controls the sequencing of fuel for the engine, fuel purge functions, and also the flow schedule for overspeed protection
ODV Functions
sequences fuel through the main fuel manifold to the injectors for starting acceleration and engine operation
Purges fuel from the main fuel manifold on shutdown to prevent coking
It shuts off fuel flow to prevent an engine overspeed when the overspeed system is sensed by the DEC
Shuts off fuel to prevent hot starts when activated by the hot start preventer (HSP)
Engine Alternator
supplies AC power and support all essential engine electrical functions. The alternator contains three separate sets of windings for its three functions
Alternator functions
Ignition exciter power
Ng signal to the cockpit
provides power to the ECU
Alternator Lost/Disabled
Ng signal is interrupted, loss of cockpit indications
ENG OUT warning and audio (Ng is <55%)
Complete loss of Alternator
No loss of cockpit indications % RPM 1 or 2, TRQ%, because of DEC/EDECU
ENG OUT warning and audio will occur
Overspeed protection is still available
HMU - PM CAN VETO
Pumps fuel at high pressure
Meters fuel in response to PAS, LDS, ECU (TQ motor) & engine variables
Collective pitch compensation through the LDS. When collective is moved, Ng is reset for immediate Np response
Acceleration/Deceleration fuel flow limiting prevents compressor stall and flameout
Ng limiting. Limits MTA @ low temps
Variable geometry positioning of the inlet guide vanes for optimum performance
ECU lockout. PAS override control w/ ECU ions. Pilot can bypass TQ motor inputs
Torque motor to trim Ng output. fine tune engine output. Override through lockout
Opens vapor vents for manual HMU priming, to remove air from HMU
Engine Alternator - INE
Ignition power to the exciters during start
Ng signal to the cockpit
ECU power
ODV - HOPS
Hot Start Preventer. Tells ODV to shut off fuel when TGT reaches 900C (Ng < 60%, Np < 50%)
Overspeed Protection (Np) From DEC @ 120% +/- 1%
Purges main fuel manifolds and allows back flow of high-pressure air for purging
Sends fuel through manifold to injectors for starting and operation
