Turbines
2 types of thrust augmentation
1. Afterburning2. Water Injection
Know the 5 components of after burner
1. Liner2. Fuel Manifolds (spray bars)3. Flame Holders4. IgnitersHot StreakElectric TorchCatalytic5. Variable Area Exhaust Nozzle
Strut and vanes function in exhaust system
1. Support the bearing 2. Straighten the gas flow leaving the rotating turbine.
Advantages of Axial flow compressor
1. Very High Compressor Ratios with relatively high efficiency2. Low Frontal Area (low drag)
Turboshaft %
100
How much cooling air cools hot gases in the combustion chamber?
55-75%
Turbjoet %
75
Turbofan Percent
85
Turboprop %
90
Adv of can type combustion chamber
Advantages:1. Burners are individually removable for easy inspection and maintenance2. Air-fuel patterns are easier to control during design
Adv on Annular type combustion chamber
Advantages:1. Less cooling air required (better heat dissipation)2. Light weight3. Shorter Length4. Total Fuel Combustion
Know how after burners work
Afterburners utilize the principle of the ram-jet engine, and therefore are even more effective at high airspeeds. Thrust increases as much as 100%, occur at high altitudes and airspeed. Operation - because 75% of the air processed by the gas generator is not used in the combustion process, large amounts of oxygen remain in the exhaust gas stream. Therefore, large amounts of fuel can be injected into the exhaust gases and burned.
Secondary Air:
Approximately 55% ~ 75% of the air flowing through the Gas Generator is used for cooling the hot gases through DILUTIONand by controlling the temperature of the metal components by insulating the components from the gases with a "blanket" or barrier of air between the gases and the burner wall
3 types compustion chambers
Can Through Flow Can-Annular Through Flow Annular Through Flow
Primary Function of Compressor
Compressors provide high pressure air to the combustion chamber.
Basic design of supersonic exhaust system
Convergent Divergent C-D Nozzle.
What does the turbine nozzle do?
Convert the heat and pressure energy of the gas stream into kinetic energy (Bernoulli)
Two ways ducts are rated for efficiency
Duct Pressure Efficiency Ratio Ram recovery point
Temperature affects the speed of sound in exhaust nozzle
Due to the increased temperature of the hot exhaust gasses, the speed of sound (Cs) increases.
Fan reverse and turbine reverse function
Fan Reversers - redirect the fan discharge air,and are primarily used on High Bypass Ratio Turbofan Engines. Turbine Reversers - redirect the exhaust gases leaving the gas generator. Turbine Reversers are used primarily on Turbojet Engines, but they can be used in combination with Fan Reversers on High Bypass Ratio Turbofan Engines
3 types of turbine blades
Impulse Reaction Impulse reaction
Exhaust System function in turbojet
In a pure turbojet engine, the exhaust system accelerates the exhaust gas velocity to sonic or supersonic speeds
Understand how ES works with After burner
In afterburner equipped aircraft, the exhaust duct is replaced by the afterburner system.
Major sections of GTE (5-6)
Inlet, Compressor, Diffuser, Combustion Chamber, Turbine, Exhaust
Adv and Disadv of after burner
No TIT Limits. The temperature is only limited by the amount of air that is available to burn the fuel.Provides extra thrust for takeoff, climb, and short duration bursts of speed without the need to install larger (heavier) engines D: Very High Specific fuel consumption
Constitutes a stage in an axial flow compressor
One row of rotor blades followed by one row of stator vanes
Difference between primary airflow secondary air flow in combustion chamber.
PRIMARY AIR- Of the Air flowing through the Gas Generator (combustion section) Approximately 25% ~ 35% is used to support the combustion process.
Understand how water injection with methanol works
Purpose: To restore the thrust (power) that would normally be lost during high density altitude operations. Increase thrust above normal for Purposeful operations. When water is introduced at the compressor inlet (face), the air mass is cooled resulting in an increase in density and mass flow. The density increase is a result of cooling by the high "latent heat of vaporization" (vaporizing liquid cooling of air).
Adv of centrifical flow compressor
Simplicity2. Ruggedness3. Low Cost4. High Compression Ratio per Stage ( ~ 4:1)5. Less weight6. Low starting power
Main function of inlet duct
Supply the engine with the required (Mass)airflow at the HIGHEST POSSIBLE PRESSUREwith the lowest DRAG.
What determines an exhaust system configuration?
System configurations vary, based upon the way in which "power is produced or extracted" from the engine. Do not try to determine the configuration of the exhaust system until you know the, design speed of aircraft (supersonic or subsonic), exhaust stream (kinetic energy), and (configuration type) of engine on which it is installed.
How the clam shell doors work
The Clamshell design is usually a Post-exit Reverser. During operation, two large deflectors are deployed into the exhaust stream.
What does a combustion chamber do?
The Combustion Chamber provides a structural area where efficient burning of the fuel-air mixture can take place. The function of this section is to ADD HEAT ENERGY to the flowing gases, thereby expanding (VOLUME Increases) and accelerating the gases (Pressure Increases) into the turbine section.
Subsonic exhaust function
The convergent nozzle limits the exit velocity of the gas stream to sonic speed. In supersonic configurations a convergent-divergent nozzle(C-D Nozzle) is required in order for the gas stream to achieve the necessary momentum change.
Diffuser Function
The diffuser decreases the velocity and increases the pressure of the mass airflow from the compressor. This forms a "wall of high pressure" upstream from the combustion chambers
Turbine function
The function of the turbine is to "EXTRACT" a portion of the kinetic energy and heat energy from the gas stream exiting the combustion chamber and transform it into mechanical energy.
How does an Impulse reaction blade work?
The impulse - reaction turbine utilizes both the impulse principle and the reaction principle to achieve the most efficient means of extracting energy from the gas stream. Since the velocity of the turbine blade is much higher at the tip than at the base, the relative velocity of the gas stream to the tip speed is significantly different across the blade length. High pressure available at the tip area has a secondary purpose of counteracting the tendency of centrifugal reaction.
Function of thrust reverser
Thrust Reversers serve the purpose of:- Aid in slowing the aircraft after landing-
Thrust reverser on turbo prop function
Turboprop aircraft achieve very high levels of reverse thrust by moving the propeller BLADE ANGLE INTO THE NEGATIVE PITCH ANGLE,(BETA RANGE),
Why turbofan engines and quieter than turbojet engines
Why turbofan engines and quieter than turbojet engines
What is a Dual spool gas turbine engine?
With a dual spool (or 3 spool) compressor the temperature of the air entering the high pressure compressor(s) is relatively high. This increase in temperature causes the speed of sound to increase and allows the design RPM of the HP compressor to be increased therefore increasing compressor effectiveness.
What does the exhaust plug do?
aids in preventing disturbances in the gas stream.
Which type of compressor has the lowest fuel consumption
axial
Section of the engine that has the most impact on engine
compressor
Shape of a subsonic inlet duct
divergent
Exhaust system affects performance of a high bypass turbo engine
eliminate noise with the elimination of inlet guide vanes
Source of noise form turbojet engine
he noise produced is by the high velocity exhaust gas SHEARINGthough the still air in a relatively small area
What constitutes one stage in an axial flow turbine
one set of stationary vanes called "NOZZLE GUIDE VANES", and one set of rotating blades
Thrust Augmentation
process by which the thrust produced by a jet-propulsion engine may be increased temporarily over its normal value by some secondary mean
