Engine Glossary

afterburner - The afterburner is a second chamber which afterburing (or
reheat) is a method of augmenting the basic thrust of an engine to improve the
aircraft takeoff, climb and (for military aircraft) combat performance.
Afterburning consists of the introduction and burning of raw fuel between the
engine turbine and the jet pipe propelling nozzle, utilizing the unburned oxygen
in the exhaust gas to support combustion. The increase in the temperature of
the exhaust gas increases the velocity of the jet leaving the propelling nozzle
and therefore increases the engine thrust. This increased thrust could be
obtained by the use of a larger engine, but this would increase the weigh and
overall fuel consumption.
ambient - The condition of atmosphere existing around the engine, such as
pressure or temperature.
ampere - A unit of measurement of current flow.
compressor - The compressor is the first component in the engine core. The
compressor squeezes the air that enters it into smaller areas, resulting in an
increase in the air pressure. This results in an increase in the energy potential
of the air. The squashed air is forced into the combustion chamber. The normal
parts of a compressor include: compressor front frame, compressor casing with
stator vanes, a rotor with rotor blades and a compressor rear frame.
axial flow compressor - The direction of the flow of compressed air is parallel
to the spool axis.
centrifugal flow compressor - The direction of the flow of compressed air
discharges outward at 90 ° to the spool axis.
The centrifugal compressor consists of a rotating impellor, a fixed diffuser and a
manifold which collection and turns the compressed air.
centrifugal force - The outward force an object exerts on a restraining agent
when the motion of the object is rotational.
Centrifugal flow turbojet: A turbojet engine with a centrifugal compressor
rather than an axial flow compressor.
centripetal force - The inward force a restraining agent exerts on a an object
moving in a circle. It is equal to, but opposite to the the centrifugal force.
combustion chambers - The purpose of the combusting chamber is to provide
a stream of hot gas that releases its energy to the turbine and nozzle sections
of the engine. There are three types of combustion chambers:
can type chamber - Chambers are arranged around the engine and the air is
delivered into ducts in each chamber. Each chamber has an inner flame tube. All the tubes are interconnected which allows each tube to operate at the same
pressure. The early axial flow compressor engines used this type of chamber.
The burners are arranged in a circular fashion around the engine. Each
chamber has a separate flame tube although they are all interconnected. Each
tube operates at the same pressure which provides identical operating
conditions.
can-annular chamber - This type was a combination of the can and annular
type chambers. A number of flame tubes are fitted inside a common air casing.
The airflow comes from the main chamber to the secondary flame tubes found
within.
annular chamber - This type of combustion chamber consists of a single
concentric flame tube surrounding the spools. This is the most efficient use of
the space available to the airflow. The main advantage of the annular
combustion chamber is that for the same power output, there is up to 25 %
reduction in the weight. As a single large combustion chamber, the combustion
process is more evenly distributed in the tube.
combustor - A chamber where air is mixed with fuel and ignited. In the
combustor the air is mixed with fuel and then ignited. This process results in
high temperature, high energy airflow. The fuel burns with the oxygen in the
compressed air, producing hot expanding gases.
compressed air - The air that is heated pushed through the combustor
compressor - fan or a pump, the first component in the engine core. The
compressor squeezes the air and pushed it forward to the combustor.
drag - The force that resists the motion of the aircraft through the air.
diffuser - air intake methods, in a variety of shapes to create different effects on
the intake of the air.
density - mass per unit volume. Engine thrust depends on density of the air: the
higher the density, the more thrust.
engine cycle - induction, compression, combustion, and expansion of air with
the result of thrust being created.
fan - The fan is the first component in a turbofan. The fan pulls air into the
engine. The large spinning fan sucks in large quantities of air. It then, speeds
the air up and splits it into two parts. One part continues through the "core" or
center of the engine, where it is acted upon by the other engine components.
The second part "bypasses" the core of the engine, instead traveling through a
duct that surrounds the core to the back of the engine where it produces much
of the force that propels the airplane forward.forces of flight - lift, drag, gravity, thrust
gas generator - the combination of the compressor, combustion chamber and
the turbine where the airflow has been compressed to a gas.
gas turbine - the turbine converts gas energy into mechanical work to drive the
compressor which is linked by a rigid shaft. (Sometimes used as the equivalent
of jet engine)
gravity - The force that pushes an object. An engine works to create enough
thrust to help lift the airplane and counteract the force of gravity.
horsepower - a unit of power equal to 33,000 ft.-lb of work per minute.
hypersonic - Very fast speed of flight. 3500 - 7000 MPH or Mach 5 to Mach 10.
The space shuttle travel this fast once it is in space..
impeller - The impeller is a part the compressor. It is designed to impel the
airflow within the compressor.
inertia -The opposition of a body to have its state of rest or motion changed.
inlet duct - The inlet duct supplies the engine with the airflow at the highest
possible pressure. Normally, an inlet duct needs to be straight and smooth and
in order to provide airflow through the duct to the compressor and it needs to
deliver the airflow with an even pressure.
jam acceleration - rapid movement of the power lever, calling for maximum rat
of engine rotor-speed increase.
jet engine. Any of a class of reaction engines that propel aircraft by means of
the rearward discharge of a jet of fluid, usually hot exhaust gases generated by
burning fuel with air drawn in from the atmosphere. The aircraft engine provides
a constant source of thrust to give the airplane forward movement. This gives
the plane an ability to sustain flight
jet silencer - a device used to reduce and change the low frequency sound
waves emitting from the engine's exhaust nozzle, to high frequency and thus
reducing the noise level.
kinetic energy - temperature of gases causes an increase in the amount of
energy in the gas.
lift - A force that pushes an object up. The lift is created by the wings of a plane.
mach number - a number that identifies the speed of an airplane by the
number of times faster than the speed of sound. mass - The amount of matter contained within a substance.
mixer - The nozzle may be preceded by a mixer, which combines the high
temperature air coming from the engine core with the lower temperature air that
was bypassed in the fan. This results in a quieter engine than if the mixer was
not present.
momentum - The tenacity of a body to continue to move after being placed in
motion.
nozzle -The nozzle is the exhaust duct of the engine. The energy depleted
airflow that passed the turbine, in addition to the colder air that bypassed the
engine core, produces a force when exiting the nozzle that acts to propel the
engine, and therefore the airplane, forward. The combination of the hot air and
the cold air are expelled and produce an exhaust which causes a forward thrust.
ohm - a unit that measures resistance to electrical current flow, and is equal to
volts divided by amperes.
pressure of gas - pressure equals force divided by unit area.
propulsion - The energy used to propel or drive forward an airplane.
power -The rate of doing work ;work per unit of time.
ram - The amount of pressure buildup above amient pressure at the engine's
compressor inlet, due to forward motion of the engine through the air - air's
initial momentum.
ram ratio - The ratio of ram pressure to ambient pressure.
ram recovery - The ability of an engine's air inlet duct to take advantage of ram
pressure.
regime - An aircraft speed category.
rpm - Revolutions per minute
shock wave - The sound waves that form in front of an airplane which act as a
barrier. The plane breaks through this barrier and causes a loud noise or sonic
boom.
sonic speed - Speed of sound, about 760 miles per hour.
sound barrier - A great increase in drag that is caused when an airplane's
speed approaches the speed of sound. When a plane travels the speed of
sound the air waves gather together and compress the air in front of the plane
to keep it from moving forward. specific heat - The ratio of the thermal capacity of a substance to the thermal
capacity of water.
speed of sound - The rate at which sound waves travel. This is about the
speed of 750 MPH. The air waves gather together to act as a force on the
moving airplane. When the force is broken, the airplane is said to be breaking
the sound barrier.
stable operation - A condition where no appreciable fluctuation, intentional or
unintentional, is occurring to any of the engine's variables , such as rpm,
temperature, or pressure. Sometimes called steady state operation.
stationary mode - A time where engine parameters do not change ( for
example: cruising flight)
subsonic speed - A speed less than the speed of sound. 100 - 350 MPH.
Some smaller planes use this speed, like the crop dusters and the seaplanes
which land on small lakes.
supersonic - A speed which is moving faster than the speed of sound. 760-
3500 MPH Often known as mach 1 to Mach 5. The Concorde is an example of
this regime.
temperature - It is a measure of the kinetic energy of the molecules and shows
how the heat of the air.
thermocouple - A pair of wires made of two dissimilar metals, joined at one
end, across which a DC voltage is produced at the other end when one end is
warmer than the other.
thrust -A force created by the engines to push an airplane through the air.
thrust, gross - The thrust developed by the engine, not taking into account any
presence of initial-air-mass momentum.
thrust, net - The effective thrust developed by the engine during the flight,
taking into consideration the initial momentum of the aircraft speed mass prior
to entering the influence of the engine.
thrust reverser - A device used to partially reverse the flow of the engine's
nozzle discharge gases and thus create a thrust force in the opposite to normal
direction.
thrust ,specific fuel consumption - The fuel that the engine must burn per
hour to generate 1 LB of thrust.
thrust, static - Thrust developed by engine, without any initial air-mass
momentum due to engine's static state.torque - A force, multiplied by its lever arm, rotating at right angles to an axis.
transient mode - Conditions that may occur briefly while accelerating or
deceleration, or while passing through a specific range of engine operation. A
time of rapid change.
transonic -350 to 750 MPH. This speed category is the most common one
used for commercial jets.
turbine - The high energy airflow coming out of the combustor goes into the
turbine, causing the turbine blades to rotate. This rotation extracts some energy
from the high-energy flow that is used to drive the fan and the compressor. The
gases produced in the combustion chamber move through the turbine and spin
its blades. The task of a turbine is to convert gas energy into mechanical work
to drive the compressor.
vector - A line that, by scaled length, indicates magnitude, and whose
arrowhead represents direction of action.
volt - A unit of measure of electrical force. It is a function of the flow current
(ampere) and the amount of resistance to flow (ohm) present.
watt - A unit that measures power and is equal to voltage multiplied by
amperes.
work - A force acting through distance.