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Questions and Answers
What is the unit of power in the formula P = F × t?
What is the difference between displacement and distance?
Which of the following is a scalar quantity?
What is the unit of the force in the formula P = F × t?
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Why does accelerating a 1500-kg vehicle over 1/4 mi in 7 s require more power than doing so in 5 min?
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What is the main difference between velocity and speed?
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What is the characteristic of air flow in a low-bypass engine?
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What is the purpose of mixing the hot and cold gas streams in a mixed exhaust engine?
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What is the fan ratio of a high-bypass engine?
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What is the characteristic of a non-mixed exhaust engine?
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What is the purpose of the 'cold gas stream' in a low-bypass engine?
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What is the design requirement for a high-bypass engine?
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What is the primary mechanism used by a turbojet engine to produce thrust?
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At what speed range is the turbojet or turbofan engine most widely used?
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What is the main advantage of the turbofan engine over the turbojet engine?
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What is the purpose of the turbine wheels in a turbojet engine?
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What is the primary difference between a turbojet engine and a turbofan engine?
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What is the main reason why the turbojet engine has been largely replaced by the turbofan engine?
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What percentage of airflow accelerated by the fan rotor blades is ducted past the core engine?
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What is the purpose of the duct in a ducted fan engine?
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Why do high-bypass engines and ducted fan engines produce more fan thrust than low-bypass engines?
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What is the purpose of the engine station system in maintenance manuals?
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What determines the number of designated engine stations in an engine?
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What is the name of the engine design where the fan is arranged behind the turbine and powered by a shaft from the turbine?
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What is the primary concern of gas turbine engines?
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What is the formula to calculate force in gas turbine engines?
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What is the unit of measurement for force in gas turbine engines?
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What is the definition of force in physics?
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What is the pressure measurement across the opening of a jet tailpipe in the worked example?
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What is the primary application of the physics principles in gas turbine engines?
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Study Notes
Physics Fundamentals
- Physics principles govern the action of mass or matter in jet propulsion.
- Understanding the relationships between gases and turbo-machinery is crucial for gas turbine engines.
Force and Thrust
- Force is the capacity to do work or the tendency to produce work, and is a vector quantity.
- Force can be measured in pounds.
- Thrust is the force produced by a gas turbine engine, rated in pounds of thrust.
- Formula for force: F = P × A, where F is force, P is pressure, and A is area.
Work and Power
- Power is measured in horsepower or kilowatts in reciprocating engines, but gas turbine engines are concerned with thrust.
- Thrust is often rated in combination with shaft horsepower in turboprop applications.
Displacement and Distance
- Displacement and distance are often used interchangeably, but have distinct definitions.
- Distance is a scalar quantity, measuring how far an object has traveled.
- Displacement is a vector quantity, measuring how far an object is from its origin.
Velocity and Speed
- Velocity is a vector quantity, having both speed and direction.
- Speed is a scalar quantity, without direction.
Bypass Ratios
- Low-bypass engines have a fan-to-compressor airflow ratio of approximately 1:1.
- Medium-bypass engines have a ratio of 2:1 or 3:1.
- High-bypass engines have a ratio of 4:1 to < 9:1.
- Ultra-high-bypass engines have a ratio of > 9:1.
Turbojet and Turbofan Engines
- Turbojet engines use the acceleration of airflow throughout the engine to produce thrust.
- Turbojet engines are well suited for high-speed, high-altitude operations.
- Turbofan engines are newer and more popular, with higher propulsive power at higher subsonic cruising speeds.
Engine Stations
- Engine stations are numbered locations along the axis line of the engine, following the gas path.
- Stations refer to specific locations such as the compressor inlet, compressor outlet, and turbine inlet and outlet.
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Description
Understanding the physical relationships between gases and turbo-machinery in a gas turbine engine, focusing on atmospheric air compression and acceleration.
