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WorksheetsGas Turbine Propulsion - Midterm Quiz 1
Total questions: 25
Worksheet time: 13mins
If the compressor delivers insufficient air pressure during startup, which operational stage is most directly affected?
Regulation of turbine inlet temperature during load
Flow of exhaust gases through the discharge system
Ignition system efficiency in the combustion chamber
Alignment of the reduction gearbox and shafting
During pre-start inspection, why is confirming the resolution of previous operational issues essential?
It increases the combustion chamber expansion ratio.
It ensures no unresolved problems compromise safe startup.
It improves lubrication system cooling water circulation.
It reduces gearbox noise and vibration during loading.
A gas turbine fails to accelerate beyond cranking speed despite proper ignition. Which component interaction should be checked first?
Air duct alignment and exhaust gas temperature sensors
Turbine exhaust pressure and air intake filtration rate
Fuel control system and combustion process coordination
Reduction gearbox lubrication and cooling water flow
What condition most likely leads to a “hot start” during turbine ignition?
Overcooling of lubricating oil during pre-lube circulation
Inadequate air filtration leading to compressor stall
Excessive fuel injection combined with slow acceleration
Delayed reduction gearbox engagement during loading
Which analysis best explains why FOD (foreign object debris) must be cleared from the intake before startup?
It prevents compressor blade damage and abnormal vibration.
It increases the bearing oil pressure during acceleration.
It ensures combustion chamber pressure remains low.
It enhances the cooling system’s heat transfer performance.
If exhaust gas temperature rises abnormally during warm-up, which action is most appropriate?
Reduce the flow of lubrication oil to slow turbine rotation.
Abort the startup sequence and inspect fuel delivery control.
Increase starting system pressure to accelerate compressor speed.
Bypass the control system to manually regulate temperature.
Why is pre-lubrication performed before rotating the gas turbine shaft?
It reduces wear and bearing friction during initial rotation.
It balances the reduction gearbox prior to power application.
It stabilizes combustion temperature before ignition occurs.
It lowers exhaust pressure to prevent compressor surge.
What does a sudden drop in oil pressure during startup most likely indicate?
An obstruction in the combustion chamber fuel nozzles
A malfunction in the lubrication pump or internal leakage
A misalignment in the propeller shaft and reduction gear
A blockage in the exhaust duct restricting gas expansion
A turbine experiences “hung start.” What system interaction most likely caused this?
Poor exhaust system sealing reducing pressure output
Misalignment in the reduction gear delaying shaft load
Starter system failure preventing compressor acceleration
Overheating of lubrication oil reducing viscosity levels
If the turbine fails to reach self-sustaining speed after light-off, which relationship should be analyzed?
Combustion pressure relative to gearbox alignment
Starter torque relative to compressor resistance
Fuel flow pressure relative to exhaust temperature
Cooling water circulation relative to bearing clearance
Which consequence results from bypassing a safety interlock during startup?
Enhanced acceleration of the turbine shaft speed
Increased risk of catastrophic equipment failure
Reduced foreign object debris within the intake
Improved fuel injection pressure in the combustor
What is the most likely reason for implementing a combustion chamber purge before ignition?
To lubricate the turbine bearings before acceleration
To increase airflow velocity and boost compressor output
To balance exhaust pressure and avoid reverse flow
To eliminate residual fuel vapors and prevent explosions
Which step most directly contributes to preventing turbine overspeed during load application?
Gradual power transmission to the reduction gearbox
Delaying ignition until full cranking speed is achieved
Running cooling pumps at maximum capacity continuously
Increasing combustion temperature before self-sustain
Which factor would most likely lead to abnormal vibration during turbine operation?
Rapid exhaust gas flow through the discharge system
Reduced fuel viscosity due to high ambient temperature
Compressor blade damage caused by foreign object ingestion
Excessive cooling water pressure within the heat exchanger
How does verifying sensor calibration contribute to safe startup?
It reduces the fuel viscosity required for proper injection.
It balances gearbox load prior to propulsion shaft rotation.
It improves combustion chamber airflow for stable ignition.
It ensures accurate feedback for automated control sequencing.
If the emergency stop system fails to engage during testing, what should be the engineer’s response?
Adjust ignition timing to lower turbine inlet temperature.
Proceed with reduced load and monitor exhaust pressure.
Suspend startup until the safety device is repaired.
Increase cooling water flow to compensate for the failure.
During a routine inspection, engineers discover condensate in turbine drains. Why must it be removed?
It can cause corrosion and disrupt combustion stability.
It reduces compressor airflow velocity and blade speed.
It improves the pressure ratio of the exhaust gas turbine.
It increases oil viscosity in the lubrication system.
Why must fuel quality and purity be verified prior to startup?
Proper cetane number reduces vibration in the turbine casing.
Fuel viscosity directly affects gearbox alignment accuracy.
Contaminants can cause unstable combustion and nozzle fouling.
Purity ensures that the exhaust system remains below design pressure.
What would be the most effective response to abnormal vibration during warm-up?
Increase lubrication oil flow to stabilize bearing temperatures.
Shut down the turbine and inspect for foreign object damage.
Reduce load to half and monitor exhaust gas temperature.
Open bypass valves to equalize pressure in the turbine casing.
If exhaust gas temperature exceeds the normal range during startup, what should be the engineer’s first action?
Engage reduction gearbox early to absorb excess energy.
Increase starting air pressure to accelerate compressor rotation.
Lower fuel pressure to delay ignition timing.
Abort the startup to prevent turbine blade overheating.
Which situation most clearly indicates a failure in the control and monitoring system during startup?
Delayed lube oil temperature rise despite pump activation
Incorrect sequence of fuel admission and ignition timing
Reduced airflow through the intake filters during combustion
Rapid acceleration of the turbine beyond self-sustaining speed
If the turbine continues to run after the emergency shutdown command is issued, which system failure should be investigated first?
Thermal expansion of turbine casing components
Main control circuit logic or actuator malfunction
Reduction gearbox lubrication bypass
Air intake filtration clogging or icing
Why is toolbox briefing critical before initiating gas turbine startup?
It accelerates the heating rate of the combustion chamber.
It increases oil flow pressure in the lubrication system.
It enhances exhaust gas velocity during load application.
It aligns the engineering team on potential risks and emergency actions.
During startup, the turbine ignites successfully but fails to transfer power to the propulsion shaft. What is the most likely cause?
Excessive exhaust gas pressure preventing turbine expansion
Malfunctioning pressure relief valves in the cooling system
Clogged air intake filters reducing compressor efficiency
Disengagement or malfunction in the reduction gearbox system
What would be the consequence of skipping the purge step before introducing fuel into the combustion chamber?
Unstable lubrication oil temperature and viscosity
High risk of explosion due to accumulated fuel vapors
Reduced turbine rotational speed during cranking
Premature engagement of the reduction gearbox
