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turbine vane
(rotor inlet temperature), also called TET (turbine entry
temperature) and TIT (turbine inlet temperature. In a
single-shaft engine the gas leaves the turbine at EGT
(exhaust gas temperature). In a two-shaft engine the gas
leaving the HP turbine upstream of the LP turbine firststage
stator is measured as TGT (turbine gas
temperature). Having passed through the LP turbine, the
gas is reduced to EGT.
turbine vane US term for turbine stator blade.
turbine wheel US usage for either one complete stage or
complete turbine, possibly of several stages.
Turbinlite Airborne searchlight for night interception
experiments (RAF, WW2).
turbo 1 Turbocharger.
2 Generalized prefix meaning driven by or associated
with gas turbine, eg *-supercharger, *-ramjet.
turboblower Air blower driven by exhaust-gas turbine to
sweep burnt mixture from cylinders of two-stroke diesel.
(Today also often used, esp. with diesels, to mean
turbocharger).
turbocharger Piston-engine supercharger driven by
exhaust-gas turbine.
turbofan Most important form of propulsion for all
except slow aeroplanes (say, below 600 km/h, 375 mph);
comprises gas-turbine core engine, essentially a simple
turbojet, plus extra turbine stages (usually on separate LP
shaft) driving large-diameter fan ducting very large
propulsive airflow round core engine and generating most
of thrust. For given fuel consumption generates much
more takeoff thrust than turbojet, with many times less
noise, but performance falls off more rapidly with
forward speed. A few * engines have aft fan whose blades
form outward extensions of those of the compressor
turbine.
turbofan pressure ratio This invariably means the pressure
ratio across the fan, not including any part of the
core.
turbofan-prop Turbofan driving propfan mounted
ahead of inlet and acting as fan booster stage to give jet as
well as shaft power.
turbojet Simplest form of gas turbine, comprising
compressor, combustion chamber and turbine, latter
extracting only just enough energy from gas flow to drive
compressor. Most of energy remains in gas, which is
expanded to atmosphere at high velocity through
constricting propelling nozzle. In supersonic aircraft often
fitted with afterburner.
turbojet-based combined cycle Propulsion system mating
turbojet and scramjet, with separate [not valved] flow
paths.
Turboline FS100 fuel additive to improve hightemperature
stability.
turboprop Gas turbine similar to turbofan but with extra
turbine power geared down to drive propeller. Difference
between two forms of engine is of degree only; fan of
turbofan is invariably shrouded, running inside profiled
case, while propeller (but not propulsor) is always geared
and normally operates unshrouded and unducted. In
general * has much higher bypass ratio than turbofan, and
is tailored to slower aircraft.
turbopump Pump driven by turbine turned by gas, e.g.
from rocket propellants.
turboramjet Combination of turbojet and ramjet as integrated
propulsion for supersonic aircraft. In theory
turn
afterburning turbojet or turbofan can be classed as *, but
in practice true * is large ramjet within or upstream of
which is turbojet for starting from rest and acceleration to
ramjet lightup speed. In some forms large valves or ductdiversion
doors are needed to change internal flows
between turbojet and ramjet modes.
turborocket Various combinations of gas turbine and
rocket in one engine.
turboshaft Gas turbine for delivering shaft power, eg to
power helicopter, ACV or other non-flying vehicle.
Essentially a turbofan or turboprop with fan or propeller
removed. Often can deliver power at either end, and
usually has at least one stage of speed-reducing gearbox.
turbostarter Main-engine starter driven by turbine
turned by gas from cartridge, IPN or other fuel.
turbosupercharger See turbocharger.
TURBT Turbulent.
turbulator See vortex generator.
turbulence Time-variant random motion of fluid in
which velocity of any particle, or at any point, is characterized
by wild and unpredictable fluctuations which are
extremely effective in conveying heat, momentum and
material from one part of fluid to others. Called isentropic
if rms velocity is same in all directions. US NWS defines
light * as wind varies 0–19 ft/s and moderate as 19–35 ft/s.
(5.79–10.67 ms 1 ).
turbulence cloud Cloud formed because of atmospheric
turbulence, usually distinctive layer above condensation
level about 30 mb (say, 300 m, 1,000 ft) thick in otherwise
stable air.
turbulence control structure Gigantic ‘golf-ball’ with
numerous planar porous walls attached to inlet of engine
on outdoor test to eliminate effect of wind.
turbulence number R (4) at which C d of smooth sphere
becomes 0.3.
turbulence plot Term has been used for plotting wake
turbulence behind aircraft, building or other bodies, and
also for recording geographical locations of severe atmospheric
turbulence, including CAT, over a long period.
turbulence screen Screen across wind tunnel to reduce
turbulence, usually rectilinear array of crossing sharpedged
strips.
turbulent boundary layer One that is no longer laminar,
characterized by gross random lateral motions, and
Reynolds stresses much larger than viscous; all boundary
layers become turbulent at R = 250,000+ unless surface
unusually smooth, though apart from rise in skin-friction
drag there should be no other significant effect and no
separation.
turbulent bursts Microscopic eruptions which occur
constantly over aircraft (or other) surface, beginning at
surface; responsible for most of skin-friction drag and
nearly half total aerodynamic drag.
turbulent flow Flow having turbulence superimposed on
main movement, measured as velocity increments about
all three axes expressed as fraction or % of mean flow
velocity.
turkey 1 Badly designed aircraft, especially aeroplane,
with sluggish or dangerous handling.
2 Aircraft with performance so poor as to be useless.
turn 1 Angular change of track; thus 30° * does not
mean 30° bank. See * rate.
2 Of marching column, to make abrupt individual 90°
turn, thus changing from column of route to line abreast.
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