TERMINOLOGY Flashcards
A carbon-pile-type voltage regulator
A carbon-pile-type voltage regulator uses variable resistance to control DC generator current.
AC
AC: AC reverses direction. AC power requires less current because of higher voltage and a ground neutral system. This allows the use of smaller aircraft wiring and therefore, less weight.
ACCESSORY DRIVE
Accessory Drive:
The accessory drive is a gearbox that forms part of a gas turbine engine. Although not part of the engine’s core, it drives the accessories, fuel pumps etc., that are otherwise essential for the operation of the engine or the aircraft on which it is mounted. Accessory drives on large engines handle between 400–500 hp.
Power for the accessory drive is taken from the central shaft linking the turbine and compressor sections of the engine. This requires an internal gearbox that couples the drive to a radial driveshaft or tower shaft that drives an external gearbox.
Some of the accessories that may be driven include:
•Fuel pump
There may be a number of fuel pumps: low pressure, high pressure and also a speed-sensitive governor
•Generators, often one for engine systems and one for the aircraft
•Constant Speed Drive to maintain a constant frequency AC generator
•Lubricating oil pumps
•Hydraulic pump
•High-pressure air compressor (undercarriage actuation, etc.)
•Low-pressure air compressor (cabin air conditioning), where this is not provided by tapping engine compressor bleed air.
•Engine starter
•Tachometer sensor drives
•Auxiliary gearbox drive, to a further gearbox that may be required in some installations.
•Additional facilities are provided for a centrifugal oil breather, to separate the drive lubricating oil from the overboard breather air vent. Also access for hand-turning the engine, during ground maintenance.
ACCESSORY SECTION
The basic elements of the accessory section are:
1. The accessory case, which has machined mounting pads for the engine-driven accessories, and
2. The gear train, which is housed within the accessory case.
The accessory case may be designed to act as an oil reservoir. If an oil tank is utilized, a sump is usually provided below the front bearing support for the drainage and scavenging of oil used to lubricate bearings and drive gears. The accessory case is also provided with adequate tubing or cored passages for spraying, lubricating oil on the gear train and supporting bearings.
Accessory: (may not be considered major section in some applications)
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Accessory: (may not be considered major section in some applications)
Gear assembly, driven by high-pressure rotor shaft, which functions to drive various accessories (oil pump, fuel pump, hydraulic pump, fuel control unit, starter-generator).
AFTERBURNER SECTION
AFTERBURNER SECTION
Afterburning. or thrust augmentation. is a method used in turbojets and turbofans to increase the maximum thrust available from an engine by 50 percent or more. However, this increase comes at the expense of fuel consumption, which increases some 300 percent. Afterburner is used during instances where added thrust is required for short periods such as takeoff, increasing rate of climb, high speeds, or providing extra performance in a combat situation. A typical afterburner assembly consists of many parts such as the afterburner fuel control unit, pressurizing valve, ignition system, the afterburner duct, etc. At this time, we will concentrate on four parts: the spray bars. the flame holders, the screech liner and the variable exhaust nozzle.
AIR PRESSURE
As air pressure increases, air molecules tend to move closer together. This results in an increase in density, and therefore, thrust increases (Figure 3.1-10). For example, an aircraft that flies through the low-pressure eye of a hurricane will produce less thrust than an aircraft operating at normal ambient pressures.
AIR TEMPERATURE
As air temperature increases, air molecules tend to move apart. This results in a density decrease, and a resultant decrease in thrust (Figure 3.1-9). An engine operating in the warm temperatures near the equator will produce less thrust than an engine operating in the cold of Alaska. Thrust may vary as much as 20 percent from standard rated thrust on a hot or cold day.
AIRSPEED
AIRSPEED
In the thrust equation, the difference between the inlet and exhaust velocities plays a major role in determining thrust available. As the inlet velocity (v initial) approaches the magnitude of the exhaust velocity (v final), thrust is reduced. Therefore, if the mass of air and fuel is held constant, thrust will decrease as airspeed increases (Figure 3.1-12). This decrease in thrust due to an increase in airspeed is theoretical.
AL TITUDE
AL TITUDE
Figure 3.1-10 Pressure Effect on Thrust
As an aircraft climbs, pressure and temperature will normally drop. From the previous discussion, thrust will decrease with a pressure decrease, and thrust will increase with a temperature decrease. With an increase in altitude, however, the rate of thrust decreases because a pressure drop is greater than the thrust increase resulting from a temperature drop. This means an engine will produce less thrust as it increases in altitude (Figure 3.1-11).
Ammeter
Ammeter – An Aircraft Ammeter is an instrument installed in series with an electrical load used to measure the amount of current flowing through the load. The unit of measure is the ampere.
An ammeter is used to monitor the performance of the aircraft electrical system. The ammeter shows if the alternator/generator is producing an adequate supply of electrical power. It also indicates whether or not the battery is receiving an electrical charge.
Ammeters are designed with the zero point in the center of the face and a negative or positive indication on either side. When the pointer of the ammeter is on the plus side, it shows the charging rate of the battery.
-A minus indication means more current is being drawn from the battery than is being replaced.
-A full-scale minus deflection indicates a malfunction of the alternator/generator.
-A full-scale positive deflection indicates a malfunction of the regulator.
AMMETER
An Ammeter measures the flow of the electric current in AMPS. An ammeter is used to monitor the performance of the airplane electrical system. The ammeter shows if the alternator/generator is producing an adequate supply of electrical power. It also indicates whether or not the battery is receiving an electrical charge. **Some gouge references “Kilowatts” as the answer.
ANNULAR COMBUSTION CHAMBER
ANNULAR COMBUSTION CHAMBER
The liner of the annular combustion chamber (Figure 3.2-17) consists of a continuous, circular, inner and outer shroud around the outside of the compressor drive shaft. The liner is often called a “burner basket” or “basket” because of its shape and the many holes that allow cooling air inside. In this type of chamber, fuel is introduced through a series of nozzles where it is mixed and ignited with the incoming air.
Advantages of the annular combustion chamber include uniform heat distribution across the face of the turbine section, which aids in the prevention of heat warping or turbine blade failure. The configuration allows for better mixing of the air and fuel. It also makes better use of available space.
The disadvantages of the annular combustion chamber include that the unit cannot be removed without first disassembling the engine from the aircraft. Also, structural problems may arise due to the large-diameter, thin-wall cylinder required with this type of chamber. This type of burner is most often found on smaller engines, such as those of helicopters, where engine removal and tear down is not too difficult.
APU
Auxiliary Power Unit (APU), a small, independent gas turbine engine, provides power through a driveshaft to a gearbox that turns a backup generator. Through this generator, the APU provides electrical power and frees an aircraft from being depend on external power. The APU can also ensure aircraft power when the engine-driven generators are not operating or fail
AXIAL FLOW COMPRESSOR
ADVANTAGES 1 2 3 4 5
DIS-ADVANTAGES 1 2 3 4 5
Advantages
1. High peak efficiencies 1. 2. Small frontal area reduces drag
3. Straight through-flow, allowing for high
ram efficiency
4. Combustion efficiency is better than
centrifugal compressors (increased 2. pressure rise by increasing the number of stages)
5. With the dual/twin/split spool, starting flexibility is greater and it has improved high-altitude performance
Disadvantages
At low inlet speed, airflow will decrease in the compressor, creating a high angle of attack on the rotor blades that could lead to a compressor stall (compressor stall discussed in later chapter). High-speed aircraft may experience an inlet air temperature of 250 degrees F. because of ram effect. These high compressor inlet air temperatures cause low compression ratios (due to air density changes) and will also reduce the air supply to the rear of the compressor
Axial Flow Compressor
3. Good efficiencies only possible over a narrow rotational-speed
4. Difficulty of manufacture and high cost
5. High starting power requirements
AXIAL FLOW COMPRESSORS
ADVANTAGES
DISADVANTAGES
The axial-flow compressor’s advantages are:
• High peak efficiencies;
• Small frontal area for given airflow;
• Straight-through flow, allowing high ram efficiency; and
• Increased pressure rise by increasing number of stages, with negligible losses.
The axial-flow compressor’s disadvantages are:
• Good efficiencies over only narrow rotational speed range,
• Difficulty of manufacture and high cost,
• Relatively high weight, and
• High starting power requirements (partially overcome by split compressors).
Axial-Centrifugal Flow Compressor-
HELICOPTERS AND SMALL AIRCRAFT.
Axial-Centrifugal Flow Compressor- A third type of compressor design utilizes the combination of the axial and centrifugal flow compressor (Figure 3.2-11). The main advantage is the large pressure increase yet small size that is useful on helicopters and small aircraft.
Axial-Flow Compressors
Axial-flow compressor- forces air along longitudinal axis, into stator vanes. Stator vanes reduce rotational flow, slow velocity, & increase air pressure.
OLDER AIRPLANES.
HIGHER EFFICIENCY, HIGH COMPRESSION RATIO (15:1)
SMALL OPENING. COMPLEX, SMALL BLADES SUSCEPTIBLE TO FOD.
Axial-Flow Compressors- The term axial-flow applies to the axial (straight line) flow of air through the compressor section of the engine. An axial-flow compressor has two main elements: Rotor blades and stator vanes. Rotor blades are rotating, airfoil- shaped blades, while stator vanes are stationary airfoil-shaped blades. Each rotor and stator pair forms a stage (Figure 3.2-9). Unfortunately, the delicate blades, especially toward the rear, make this type of compressor especially susceptible to FOD. Furthermore, the number of compressor blades and vanes (which can exceed 1,000), the close fits, and the narrow range of operating conditions make the axial flow compressor both complex and expensive. For this reason, the axial flow compressor finds its greatest application where the considerations of efficiency and power outweigh cost and simplicity. The small frontal area of this design is also beneficial to high-speed aircraft due to decreased drag.
Batteries:
Batteries: two 12 volt batts in series will be 24 volt system.
BATTERY
If you lose the generator and the alternator, how is the AC bus powered?
The Battery, via an inverter (converts DC to AC)
Battery provides DC power, but it’s primarily used as a source of emergency power should the generators fail and also for starting the aircraft
Battery:
Battery: power reservoir that stores electrical energy in a chemical form. Must have lower voltage than the system to charge. Rated at amp-hours.
Bernoulli’s theorem
Bernoulli’s theorem states that as any incompressible fluid passes through a convergent opening its velocity increases and pressure decreases. Only Subsonic. It has opposite effect in Super sonic.
Bleed Air-
Bleed Air- air tapped from compressor section to used for pressurization, heating, air-conditioning, thermal anti-ice, and other systems.
BRAYTON CYCLE
THE BRAYTON CYCLE
A gas turbine engine follows a cycle of operation known as the Brayton Cycle (Figure 3.1-4). This operating cycle consists of four events which occur simultaneously: intake. compression. combustion and exhaust. It is important to note that this cycle of operation is different than the operating cycle of a reciprocating engine. Different than a reciprocating engine.
BREATHER PRESSURIZING SUBSYSTEM:
The breather pressurizing subsystem pressurizes the scavenge subsystem along with the oil tank to sea level pressure. Pressurization is provided by compressor bleed air
Burner Can (combustion chamber)-
Burner Can (combustion chamber)- outer casing, with inner liner, which contains fuel injection, ignition, & self-sustaining “fireball.” Combustion chamber ports expanding combustion gases via high-pressure turbine nozzle into high-pressure turbine rotor.
Bus ties:
Bus ties: switches or relays used to connect or disconnect buses from one another in order to isolate failed buses
Bypass air-
Bypass air- ratio of air flowing through fan to amount of air flowing through gas turbine. Higher bypass ratios yield greater fuel efficiency at low altitude.
BYPASS RATIO
The amount of air that bypasses the gas generator in comparison with the amount of air that passes through the gas generator is called the bypass ratio. This ratio ranges from about 1 to 5 or more. For example, a bypass ratio of 2 : 1 means that for every two molecules of air that travels around the gas generator, one molecule goes through the gas generator. A bypass ratio of 6 : 1 has six molecules bypassing the gas generator and one molecule going into the generator.
BYPASSED OR DUCTED AIR
This airflow that goes around the gas generator is called bypassed or ducted air.
CAN COMBUSTION CHAMBER
CAN COMBUSTION CHAMBER
The can type combustion chamber is used most frequently on older centrifugal compressor engines. The airflow is ducted to individual combustion cans that are arranged around the circumference of the burner section (Figure 3.2-16). Each burner can contains its own fuel nozzle, burner liner and casing. Primary air introduced at the nozzle supports combustion, while secondary air flows through, between, and around the liner and burner case to provide cooling.
Advantages of the can combustion chamber lie in its strength and durability, combined with the ease of maintenance. Individual units can be inspected or replaced without disturbing the rest of the engine.
Disadvantages of the can combustion chamber include poor use of space in the chamber, greater pressure loss, and uneven heat distribution to the turbine section. Since each can directly adjoins the turbine section, a malfunction of one can may lead to turbine damage due to non-uniform temperature distribution at the turbine inlet.
CAN-ANNULAR TYPE
CAN-ANNULAR TYPE
Used primarily on larger, high performance engines, the can-annular combustion chamber combines the ease of maintenance of the can type with the excellent thermodynamics of the annular type. The can-annular combustion chamber (Figure 3.2-18) consists of cans at the front where the fuel and air are mixed and burned.Since the frontal area is where most problems occur (fuel nozzle failure or “burn-through”), an engine needs the structural strength of the can along with its ability to be easily inspected or replaced. The hot gases then pass to the annular area of the chamber where they are mixed together. This design provides an even temperature distribution at the turbine inlet and eliminating the possibility of cold spots caused by nozzles clogging. It also has greater structural stability and lower pressure loss than that of the can type. Though this type of design is efficient, its disadvantage is that it is expensive.
CENTIFUGAL COMPRESSOR
ADVANTAGES
DIS-ADVANTAGES
Advantages 1. Rugged 2. Low cost 3. Good power output over a wide range of RPMs 4. High pressure increases per stage Disadvantages 1. Large frontal area required 2. Impractical for multiple stages
CENTRIFUGAL FLOW COMPRESSOR
Centrifugal-flow compressor- forces air outward, into diffuser. Diffuser slows velocity, & increases air pressure
LOWER COMPRESSION RATIO
Centrifugal flow compressor consists of three main components: an impeller (also known as the rotor inducer), a diffuser, and a manifold (Figure 3.2-8). Air enters this type of compressor near the center of the impeller. The impeller, which is driven at high speeds by the turbine, accelerates the air
outward toward the diffuser. This high
rotational speed increases airflow velocity. As
the air is accelerated outwards, it passes through
divergent passages on the impeller. This
divergence causes a pressure increase. Since the
airflow velocity and pressure is increased by
the impeller, total pressure is increased.
CENTRIFUGAL FLOW COMPRESSOR
ADVANTAGES
DISADVANTAGES
The centrifugal-flow compressor’s advantages are:Screen
• High pressure rise per stage,
• Efficiency over wide rotational speed range,
• Simplicity of manufacture and low cost,
• Low weight, and
• Low starting power requirements.
The centrifugal-flow compressor’s disadvantages are:
• Its large frontal area for a given airflow and
• Losses in turns between stages.
CIRCUIT BREAKERS
Circuit breakers provide a means to manually or automatically interrupt power. In an abnormal electrical situation such as an ‘overload’ or a short in the circuit (wires), circuit breakers automatically open (“pop out”), de-energizing the circuit which prevents damage to the component or the electrical system. It can also provide a manual control of electrical power to various components in case of troubleshooting, or replacement of components
Circuit breakers:
Circuit breakers: disconnect individual components that are drawing too much current
Circuit Breakers:
Circuit Breakers:
Electromagnetic-type may be reset immediately and rated in amperes Only trip-free circuit breakers (impossible to hold manually closed) are used in aircraft. Automatic-reset breakers are not used.
COMBUSTION/BURNER SECTION
Airflow from the compressor entering the burner section will be divided into two types: primary and secondary air. Twenty-five percent is primary air, and it is mixed with fuel for combustion. The remaining 75 percent is secondary air, it flows around the chamber and through the small holes and louvers to cool the thin walls and control the flame. This unburned air can also be used to help cool the turbine and for afterburner operation.
The burner section (Figure 3.2-15) contains the combustion chamber, and provides the means for proper mixing of the fuel and air to assure good combustion. The development of burner systems presents many challenges in the areas of thermodynamics, fluid mechanics and metallurgy. It must deliver the combustion gases to the turbine section at a temperature that will not exceed the allowable limit of the turbine blades. The chamber must also, within a limited space, add sufficient heat energy to the gases passing through the engine to accelerate their mass and produce the desired thrust for the engine and power for the turbines.
COMPRESSOR SECTION
COMPRESSOR SECTION
The primary function of the compressor is to supply enough air to satisfy the requirements of the combustion section. Specifically, the compressor increases the pressure of the airflow from the air inlet duct and directs it to the burners in the quantity and at the pressures required. A secondary function is to supply compressor bleed air to operate various components throughout the engine and aircraft
Compressor stall-
distorted inlet air exceeds the fixed pitch compressor blade’s critical angle of attack. Airflow to compressor slows or stagnates, resulting in flow reversal. Indicated with loud “bang.” Reduce power setting, reduce angle of attack, & increase airspeed to correct.
CONSTANT SPEED DRIVE CSD
Generators frequently use a Constant Speed Drive (CSD) to maintain a constant rotational input speed regardless of engine RPM. This ensures a steady voltage output.
CONSTANT SPEED DRIVES (CSDs)
CSDs are mainly used on airliner and military aircraft jet engines to drive the alternating current (AC) electrical generator. In order to produce the proper voltage at a constant AC frequency, usually 3-phase 115 VAC at 400 Hz, a generator needs to spin at a constant specific RPM (typically 6,000 RPM for air-cooled generators).Since the jet engine gearbox speed varies from idle to full power, this creates the need for the Constant Speed Drive (CSD). The CSD takes the variable speed output of the accessory drive gearbox and hydro-mechanically produces a constant output RPM.The CSD holds the speed of the generator, and the frequency of the AC constant as the engine speed varies through its normal operating range. CSDs prevent power surges or breaks.
CONVERGENT
THIS CONVERT IS VERY NARROW MINDED
The tube narrows and velocity increases and pressure decreases. At supersonic airspeeds, the airflow has an opposite effect when encountering convergent or divergent openings. As airflow approaches/reaches supersonic speeds, the airflow becomes more compressible. Since the airflow is compressible, it doesn’t follow Bernoulli’s Theorem but actually acts opposite to it. Therefore, when supersonic airflow passes through a convergent opening, the velocity decreases and the pressure increases (Figure 3.1- 2b). Conversely, when supersonic airflow encounters a divergent opening, its velocity will increase and its pressure will decrease
CREEP
Blades undergo elongation, or “creep”, as they are heated. This is a cumulative process, and excessive temperatures over long periods may result in permanent blade deformation. Deformed blades will not operate efficiently and may fail catastrophically causing severe damage and possible injury or death to personnel.
Current
Current = output volume or flow (measured in amps).
DC
DC: DC is a form of electricity that flows in one direction (we originally thought from positive to negative, hence why negative is ground). The components of a DC system are very heavy compared to their relative power outputs.
Density
Density is the mass of a substance per unit of its volume. According to the thrust equation, if the mass of airflow increases, thrust will increase. If the density of air increases, mass will increase, and therefore thrust will increase. As an aircraft operates at various altitudes and climates, the ambient air temperature and pressure will vary. These factors will affect the density of the air entering the engine, and as a result, will affect thrust.
DIFFUSER
DIFFUSER = When velocity is decreased then the pressure is increased.
When the pressure is increased and velocity is decreased, the opening is a diffuser.Only Subsonic. It has opposite effect in Supersonic.
DIFFUSER
In addition to critical aerodynamic functions, the diffuser also provides:
• Engine structural support, including engine mounting to the nacelle
• Support for the rear compressor bearings and seals
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• Bleed air ports, which provide pressurized air for:
• airframe “customer” requirements (air conditioning, etc.)
• engine inlet anti-icing
• control of acceleration bleed air valves
• Pressure and scavenge oil passages for the rear compressor and front turbine bearings.
• Mounting for the fuel nozzles.
DIFFUSER
CONVERT HIGH VELOCITY OF AIRFLOW TO HIGH PRESSURE.
As the air is thrown from the outer rim of the impeller, it is forced through divergent passages in the diffuser. The diffuser is stationary and therefore it does not add energy to the airflow. The divergent passages in the diffuser convert the high velocity airflow to high pressure. Thus, velocity decreases, pressure increases, and total pressure remains the same. The airflow then passes through the compressor manifold. which directs it to the combustion chamberThe diffuser (Figure 3.2-14) is located after the compressor, and it prepares the airflow for the burner chamber. The diffuser decreases the velocity, which gives the airflow a final pressure increase. The airflow velocity must decrease slightly to avoid blowing out the burner flame, and the increase in pressure helps combustion and fuel efficiency.
DIFFUSER
The diffuser is located after the compressor, and it prepares the airflow for the burner chamber. The diffuser decreases the velocity, which gives the airflow a final pressure increase. The airflow velocity must decrease slightly to avoid blowing out the burner flame, and the increase in pressure helps combustion and fuel efficiency
Diode is a two-element device
Diode is a two-element device that allows current to travel in one direction.
Diodes:
Diodes: one-way check valves
DIVERGENT
THIS DIVERT IS LEAVING AND OPENING UP TO NEW CONCEPTS.
The tube opens up and velocity decreases so pressure increases.
DIVIDED ENTRANCE INLETS
DIVIDED ENTRANCE INLETS
The divided-entrance inlet duct can be found in a variety of aircraft, including the AV-8 (Figure 3.2-4). While it allows the pilot to sit lower in the fuselage and reduces friction losses due to length, the divided-entrance inlet duct does present some problems.
DRY SUMP
Most aircraft employ a dry sump configuration for oil storage. In a dry sump system, the oil supply is carried in a tank located in the airframe or mounted on (but not an integral part of) the engine. With this type of system a larger oil supply can be carried and the temperature of the oil can be readily controlled. The dry sump system allows axial flow engines to retain their comparatively small diameter by arranging the oil tank and oil cooler in a manner consistent with the streamlined design of the engine
Three Subsystems of the Dry Sump System:
Pressure subsystem: supplies lubricating oil from the tank to the main engine bearings and the accessory drives.
Scavenge subsystem: removes the oil from the main bearings and accessory drives through the oil coolers and returns it to the tank, completing the oil flow cycle.
Breather pressurizing subsystem: connects the individual bearing compartments and the oil tank with the breather pressurizing valve to help minimize oil leakage
DUAL SPOOL AXIAL FLOW COMPRESSOR
Dual spool axial flow compressor- Greater flexibility and power can be achieved in the axial flow compressor through what is known as a dual spool (also known as twin or split spool) compressor. In this configuration, the compressor is divided into two completely independent rotor spools, each driven by its own turbine and drive shaft
(Figure 3.2-10). One spool is known as the low-pressure compressor, while the other is known as the high-pressure compressor.
Dynamic pressure
Dynamic pressure is the kinetic energy of fluid molecules in motion. It is a measure of the force of the fluid molecules as they move through a system. Sometimes called Velocity.
EGT- Exhaust Gas Temperature.
EGT- Exhaust Gas Temperature. Usually, main engine temperature gauge used to prevent heat damage to turbine blades or other systems. EGT (Exhaust Gas Temperature): Measured aft of the turbine section
Electric relay
A purpose of a electric relay (magnetically operated switch) is to control high-current equipment items with a small switch.
Electrical bonding
Electrical bonding is process of connecting various parts of the aircraft to prevent static electricity discharges within the aircraft structure. Also to decrease the probability of lightning damage to control hinges.
Electrical bus bar system:
Electrical bus bar system: aircraft’s electrical system is carefully organized into separate but interconnected circuits. Important circuits can be isolated from one another and supplied by alternate power sources. Redundancy is also provided.
Engine driven generators
Engine driven generators supply electric current to the electrical system and maintain a sufficient electrical charge in the battery.
Generators: engine driven, generate electricity by moving permanent magnets around a coil of wire, thereby motivating electron flow in the coil
Normally generate AC current and must produce adequate amperage to power all of the components on its circuit(s) (or load shedding)
ENGINE PRESSURE RATIO (EPR)
EPR gauge indicates the pressure ratio between the inlet and exhaust airflow.
For aircraft that rely on the propulsive power of the exhaust gases of a gas turbine engine. such as turbojets and turbofans. use a Engine Pressure Ratio (EPR) gauge (Figure 3.1-15). The EPR gauge indicates the pressure ratio between the inlet and exhaust airflow. The EPR gauge is more widely used because it automatically accounts for some of the airflow variations at the inlet.
ENGINE REVOLUTIONS PER MINUTE (RPM)
ENGINE REVOLUTIONS PER MINUTE (RPM)
One of the most obvious factors that affects the thrust output is the rotational speed of the engine. With an increase in RPM, there is an increase in thrust. However, at low RPM there is very little increase in thrust with an increase in throttle. At higher rates of revolution, a small increase in throttle setting will produce a large increase in thrust. At the lower settings, fuel consumption is high for the amount of thrust produced. normally operated at near their maximum RPM.
EPR- Engine Pressure Ratio “eeper.”
EPR- Engine Pressure Ratio “eeper.” Ratio of turbine discharge (exhaust) to engine inlet pressure (intake). EPR used to measure thrust produced, especially for takeoff, of “pressure-rated” engine.
Essential bus:
routes power to equipment required for flight safety (i.e., primary attitude gyro).
Exhaust
Exhaust
After the gas has passed through the turbine, it is discharged through the exhaust. Though most of the gaseous energy is converted to mechanical energy by the turbine, a significant amount of power remains in the exhaust gas. This gas energy is accelerated through the convergent duct shape of the exhaust to make it more useful as jet thrust - the principle of equal and opposite reaction means that the force of the exhausted air drives the airplane forward.
EXHAUST SECTION
EXHAUST SECTION
The exhaust section of the turbojet engine is constructed of several parts, each of which has its individual functions. Although the parts have individual purposes, they have one common function. They must direct the flow of hot gases rearward to cause a high exit velocity to the gases while preventing turbulence. If a majority of the gas expansion takes place in the turbine section, as in a turboprop and turboshaft, the exhaust section merely acts to conduct the exhaust stream towards the rear.
Exhaust:
Exhaust:
Accelerated exhaust gasses provide thrust. Turbojet exhaust- hot exhaust gases rip into cool atmosphere, resulting in loud wind shear. Turbofan exhaust- tapered cone & struts mix hot primary exhaust with cool bypass airflow to produce total thrust. Cool bypass air mixing with hot exhaust air, insulates/disperses hot exhaust gasses & muffles loud wind shear.
EXIT GUIDE VANES
Exit guide vanes, also known as straightening vanes, are located at the discharge end of the compressor. They are the last set of stator vanes which prepares the airflow for the diffuser by straightening the airflow to reduce the airflow turbulence as it comes off the rotational movement of the compressor
FALSE START
A “false start” occurs when compressor rpm stabilizes below normal, and the turbine temperature remains within limits
FILTER BYPASS VALVE (OIL)
The filter bypass valve allows oil to flow around the filter element, should this filter become clogged. If this occurs, the filtering action is lost, allowing unfiltered oil to be pumped to the bearings
FILTERS
Filters ensure delivery of contaminant free hydraulic fluid by preventing dust, grit and undesirable impurities from entering the system
A red differential pressure indicator button raises when differential pressure is exceeded indicating a clogged filter element
FLAME HOLDER / afterburner
flame holder (Figure 3-2.29) that is located downstream of the fuel spray bars. The flame holder provides a region in which airflow velocity is reduced and turbulent eddies are formed. This allows the proper mixing of fuel and air for combustion. These flame holders usually take the form of several concentric rings with a V cross-sectional shape.
Flameout-
Flameout- fuel/air mixture is not sufficient to sustain combustion.
FLASH POINT
The lowest temperature of a combustible substance (fuel) that would ignite with a momentarily application of a flame is its flash point. A fuel’s flash point and volatility rating are inversely related. As the fuel’s volatility rating increases, the flash point of the fuel decreases
FREE POWER TURBINE
The fan is driven by the turbine section. A free or power turbine (Figure 3.4-4), which is a turbine aft of the gas generator turbines and is not connected to the gas generator, may drive the fan. In this configuration, the fan is also separate from the
gas generator.
