5-1 Principles of Gas Turbine Operation

 EXPLAIN Bernoulli's Equation, given dynamic pressure, static pressure, and total pressure Bernoulli's EquationTotal Pressure =Static Pressure+DynamicTP = Pressure + Velocity Bernoulli's theorem states that an any incompressible fluid passes through a convergent opening, its velocity increases and pressure decreases. For total pressure, if pressure (static pressure) increases, velocity (dynamic pressure) must decrease. DESCRIBE the behavior of airflow in a nozzle An opening that increases the airflow's velocity and decreases the airflow's pressure.Subsonic air - Convergent passageSupersonic air - divergent passage DESCRIBE the behavior of airflow in a diffuser An opening that causes pressure to increase and velocity to decrease.Subsonic-Divergent passageSupersonic-Convergent DESCRIBE the Brayton Cycle Consist of 4 cycles that simultaneously occur.IntakeCompressionCombustionExhaust Very different than the operating cycle of a reciprocating engine (Otto cycle).-Brayton cycle occurs simultaneously, Otto cycle occurs sequentially-Brayton cycle takes place throughout the gas turbine engine, Otto cycle generally takes place within a single piston DESCRIBE a gas generator Produces the high-energy airflow necessary for creating thrust.It will minimally include the compressor, combustion chamber, and turbine.Turbofan, turboprop, and turboshaft will include their respective fan, propeller or rotor blades. DESCRIBE how airflow properties change through each section of a gas turbine engine DESCRIBE engine thrust The result of many pressure, temperature, and velocity changes as airflow passes through an engineGross thrust is the measurement of thrust due solely from the velocity of the exhaust gas (such as the engine being mounted and tested)Net Thrust is Gross thrust corrected for the effect of inlet airflow velocity.Net thrust and gross thrust will be equal when inlet airflow velocity is zero and the atmospheric conditions are standard. DESCRIBE the effects of airflow properties on thrust in a gas turbine engine Air DensityIncrease in Density =increase Mass = Increase thrust TemperatureIncrease in Temperature EXPLAIN ram effect in a gas turbine engine The compressibility of airflow as velocity increases toward supersonic.Typically, as airspeed increases, thrust decreases.Net thrust = mass * (Vfinal-Vinitial)/t Sincer higher airspeed increases Vinitial thrust decreases.However, the higher airspeed causes air to be "rammed" into the inlet, increasing the mass and pressure.This offsets the decrease in acceleration and results in a neutral effect or slight increase in thrust at subsonic airspeeds. DESCRIBE the cockpit thrust measuring devices Pressure Indication GaugesFor aircraft that rely on the propulsive power of the exhaust gas turbine engine, such as turbojets and turbofans, use a Engine Pressure Ratio (EPR) gauge.The EPR indicates the pressure ratio between the inlet and exhaust airflow.It is more widely used because it automatically accounts for some of the airflow variations at the inlet (thrust available). TorquemeterUsed by a turboprop or turborotor to indicate power available.Indicates shaft horsepower available to drive a propeller or rotor. TachometerGauge most commonly used to determine engine performance.Provides crew with an indication of engine speed.Does not actually measure thrust, but gives a quick assessment of energy produce by the engineUses percent rpm (most engines 100% represents full power). Authordundane ID320636 Card Set5-1 Principles of Gas Turbine Operation DescriptionEnabling Objectives Updated2016-06-05T00:37:19Z Show Answers