Untitled Quiz

Thermal Efficiency and Compression Ratio

• Increasing compression ratio leads to higher thermal efficiency.
• This means the engine converts more fuel energy into useful work.

Specific Fuel Consumption (SFC)

• SFC is a measure of how much fuel an engine consumes per unit of power produced.
• Lower SFC indicates better fuel efficiency.

SFC and Aircraft Speed

• Higher aircraft speeds can lead to increased SFC due to factors like drag and air density.

Compressor and Turbine Efficiency

• Degradation in compressor and turbine efficiency can occur due to fouling, wear, or damage.

Thrust and Altitude/Temperature

• Thrust decreases with increasing altitude due to lower air density.
• Thrust also decreases with increasing temperature due to reduced air density.

Adiabatic Compression

• Adiabatic compression is a process where no heat is exchanged with the surroundings.
• Achieving high adiabatic compression efficiency contributes to higher engine efficiency.

Maximum Fuel Flow Control

• The engine's fuel control system limits fuel flow to prevent over-speeding, protecting the engine.

Thrust Formula

• Thrust = Mass flow rate of air * (Exit velocity - Inlet velocity) + (Exit pressure - Ambient pressure) * Nozzle area

Momentum Thrust

• Momentum thrust is generated by the acceleration of air through the engine, increasing its velocity.

Shock Wave Formation

• Nozzle reaches Mach 1, creating a shock wave, when the pressure in the jet pipe exceeds ambient pressure by a factor of 1.4:1.

Pressure Thrust

• Pressure thrust is generated by the difference in pressure between the jet pipe and the ambient air.
• A convergent-divergent nozzle is typically needed to fully utilize pressure thrust.

Thrust Units

• Thrust is measured in units of force, commonly in pounds (lbs) or Newtons (N).

Pressure Thrust vs. Momentum Thrust

• Pressure thrust is generated by the pressure difference, while momentum thrust is due to velocity change.
• Passenger aircraft engines prioritize momentum thrust, making pressure thrust negligible.

Temperature and Thrust

• Decreased air temperature can decrease thrust due to lower air density.

Altitude and Thrust

• Thrust decreases with increased altitude, even at constant airspeed and RPM, due to lower air density.

Ram Effect and Thrust

• At higher airspeeds, ram effect increases thrust by compressing the air entering the engine.

Forward Speed and Thrust

• Increasing forward speed without ram effect can slightly decrease thrust due to increased drag.

Flat Rated Thrust

• Flat rated thrust refers to a consistent thrust output across a range of operating conditions.

Altitude and Pressure/Temperature

• Pressure decreases exponentially with altitude, while temperature decreases at a slower, linear rate.

Air Density and Thrust

• Thrust directly correlates with air density. Higher density air provides more mass for acceleration.

Ambient Temperature and Thrust

• Higher ambient temperatures reduce air density, limiting maximum thrust achievable at a given throttle setting.

Kink Point

• Kink Point in a turbine engines' operating chart is a point where an increase in fuel flow results in a plateau in thrust and significant increase in turbine exhaust temperature.

Take-Off Thrust Rating

• Take-Off Wet Thrust/SHP is used only during take-off operations utilizing water injection.

Emergency Thrust Rating

• Maximum Continuous (MC) Thrust/SHP is limited by engine temperature and can be used by the pilot during emergencies with no time limit.

Primary Thrust Rating

• Turbine engines are primarily thrust rated based on Take-Off Dry Thrust/SHP, representing maximum thrust available without water injection.

Take-Off Dry Thrust/SHP vs. Take-Off Wet Thrust/SHP

• Take-Off Wet thrust includes thrust generated by water injection, leading to higher thrust potential than Take-Off Dry Thrust.

Normal Climb Thrust Rating

• Maximum Continuous (MC) Thrust/SHP should be used for normal climb to cruising altitude.

Thrust Rating Limitations

• Take-Off Dry Thrust/SHP is limited during take-off operations.

Engine Power Rating Purpose

• Engine power ratings are used in certification and operational procedures to ensure safe and efficient performance.

Turbojet Engine Description

• A turbojet engine compresses air, burns fuel, and expands hot exhaust gases to generate thrust.
• It is characterized by direct exhaust of high velocity gases, resulting in a low bypass ratio.

Multi-Spool Design

• Multi-spool design in jet engines allows for the independent control of different compressor and turbine sections, improving efficiency and performance.

Bypass Air

• In bypass engines, a portion of air is bypassed around the core engine and mixed with the exhaust to improve efficiency.
• This bypass air contributes to lower noise levels and higher efficiency compared to turbojet engines.

Ram Jet Basics

• Ram jet engines rely on the compression of air by the high-velocity flight of the aircraft.
• They are typically used at high speeds where the ram effect is sufficient for compression without a compressor.

Turbo-Shaft Engine

• Turbo-shaft engines are similar to turboprops but do not have a propeller.
• They use the turbine shaft to generate power for a gearbox, which drives a rotor or other mechanical device.

Newton's Law of Motion and Propulsion

• Newton's Third Law of Motion (action-reaction) is fundamental to propulsion.
• Explains how the ejection of a high-velocity stream of exhaust gas produces an equal and opposite force (thrust) that moves the aircraft forward.

Turbo Fan Engine Arrangement

• High bypass turbo fan engines typically employ a dual-spool arrangement, with one spool for the fan and another for the core engine.

Gas Turbine Engine for Helicopters

• Turbo-shaft engines are best suited for propelling helicopters.
• They efficiently generate power to drive the main rotor, providing lift and control.

Turbojet Engine Characteristics

• Turbojet engines are not known for their high bypass ratios and low noise levels as those features are characteristic of turbofan engines.

Multi-Spool Engines

• Multiple spools in gas turbine engines allow for:
• Independent optimization of compressor and turbine stages, minimizing engine weight and improving efficiency.
• Better control over airflow through different stages, maximizing performance across different speeds and altitudes.