NIFE Engines Exam Questions and
Answers 100% Pass
Static pressure - ✔✔PRESSURE-potential energy of a fluid at rest
Dynamic Pressure - ✔✔VELOCITY-KE of fluid molecules in a system
In a closed system - ✔✔total pressure is constant
Bernoulli's Theorem - ✔✔as any incompressible fluid passes through a convergent
opening, its velocity increases and pressure decreases
Subsonic Nozzle - ✔✔-Pressure decreases
-Velocity increases
-convergent
Subsonic Diffuser - ✔✔-Pressure increases
-Velocity decreases
-divergent
Supersonic Nozzle - ✔✔-Pressure decreases
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,-velocity increases
Divergent
Supersonic Diffuser - ✔✔-Pressure increases
-Velocity decreases
-Convergent
3 main sections of a gas generator - ✔✔- compressor
-combustion chamber
-turbine
Brayton cycle - ✔✔4 events occur simultaneously (intake, compression, combustion,
exhaust)
ICCE - ✔✔Intake
Compression
Combustion
Exhaust
Otto Cycle - ✔✔reciprocating engine's cycle
-events occur sequentially
Gross Thrust - ✔✔measurement of thrust solely from the velocity of the exhaust gases
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,-stationary engine
-manufacture provided rating at std conditions 29.92 in hg and 15 C
Net Thrust - ✔✔thrust that corrects for the effect of inlet air flow velocity
Net thrust = - ✔✔m *((Vfinal - Vinitial)/t)
Factors that affect Thrust of a gas engine - ✔✔-Temperature
-Pressure
-altitude
-Engine RPM
-RAM Effect
Altitude - ✔✔Overall thrust decreases with altitude because the drop in pressure has a
greater impact upon overall thrust then the temp drop
Above 36,000 ft - ✔✔temperature stabilizes no longer offsetting pressure therefore
thrust more rapidly decreases above 36,000ft
Atmosphere pressure - ✔✔as altitude increases, pressure decreases
airspeed - ✔✔as mass is held constant, thrust decreases with increasing airspeed
Engine RPM - ✔✔an increase in RPM will increase thrust
-lower RPM little thrust increase with throttle increase
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, -higher RPM large thrust increase with small throttle
RAM effect - ✔✔at higher airspeeds more air molecules are rammed into inlet
increasing mass
-constant at subsonic speeds
-supersonic speeds greatly increase thrust with RAM effect
Thrust Measurement devices - ✔✔-Engine Pressure Ratio (EPR)
-Torquemeter
-Tachometer
Engine Pressure Ratio (EPR) - ✔✔-Turbojets/turbofans
-indicates the pressure ratio between inlet and exhaust airflows
Torquemeter - ✔✔Turboprop/Turboshaft
-propeller or rotor driven
-indicates shaft horsepower available to drive
-ft-lbs torque
Tachometer - ✔✔-Most commonly used gauge
-engine rotation speed
-Calibrated in percent RPM **
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Answers 100% Pass
Static pressure - ✔✔PRESSURE-potential energy of a fluid at rest
Dynamic Pressure - ✔✔VELOCITY-KE of fluid molecules in a system
In a closed system - ✔✔total pressure is constant
Bernoulli's Theorem - ✔✔as any incompressible fluid passes through a convergent
opening, its velocity increases and pressure decreases
Subsonic Nozzle - ✔✔-Pressure decreases
-Velocity increases
-convergent
Subsonic Diffuser - ✔✔-Pressure increases
-Velocity decreases
-divergent
Supersonic Nozzle - ✔✔-Pressure decreases
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,-velocity increases
Divergent
Supersonic Diffuser - ✔✔-Pressure increases
-Velocity decreases
-Convergent
3 main sections of a gas generator - ✔✔- compressor
-combustion chamber
-turbine
Brayton cycle - ✔✔4 events occur simultaneously (intake, compression, combustion,
exhaust)
ICCE - ✔✔Intake
Compression
Combustion
Exhaust
Otto Cycle - ✔✔reciprocating engine's cycle
-events occur sequentially
Gross Thrust - ✔✔measurement of thrust solely from the velocity of the exhaust gases
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,-stationary engine
-manufacture provided rating at std conditions 29.92 in hg and 15 C
Net Thrust - ✔✔thrust that corrects for the effect of inlet air flow velocity
Net thrust = - ✔✔m *((Vfinal - Vinitial)/t)
Factors that affect Thrust of a gas engine - ✔✔-Temperature
-Pressure
-altitude
-Engine RPM
-RAM Effect
Altitude - ✔✔Overall thrust decreases with altitude because the drop in pressure has a
greater impact upon overall thrust then the temp drop
Above 36,000 ft - ✔✔temperature stabilizes no longer offsetting pressure therefore
thrust more rapidly decreases above 36,000ft
Atmosphere pressure - ✔✔as altitude increases, pressure decreases
airspeed - ✔✔as mass is held constant, thrust decreases with increasing airspeed
Engine RPM - ✔✔an increase in RPM will increase thrust
-lower RPM little thrust increase with throttle increase
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, -higher RPM large thrust increase with small throttle
RAM effect - ✔✔at higher airspeeds more air molecules are rammed into inlet
increasing mass
-constant at subsonic speeds
-supersonic speeds greatly increase thrust with RAM effect
Thrust Measurement devices - ✔✔-Engine Pressure Ratio (EPR)
-Torquemeter
-Tachometer
Engine Pressure Ratio (EPR) - ✔✔-Turbojets/turbofans
-indicates the pressure ratio between inlet and exhaust airflows
Torquemeter - ✔✔Turboprop/Turboshaft
-propeller or rotor driven
-indicates shaft horsepower available to drive
-ft-lbs torque
Tachometer - ✔✔-Most commonly used gauge
-engine rotation speed
-Calibrated in percent RPM **
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