Topic 02 v2 - Types of Gas Turbine Engines Flashcards
The basic operating principles of a turbojet engine
Air is compressed in the compressor, burned in the combustion chamber, expands and spins the turbine which in turn drives the compressor(self-sustaining), and leaves the exhaust at high velocities.
What produces thrust in a turbojet engine?
difference in velocity in the inlet and exit
EPR
engine pressure ratio
What is engine pressure ratio
the ratio of turbine discharge pressure to the inlet air pressure
What is a spool in turbojet
when a compressor and turbine are joined on one shaft
From the compressor, the air is fed directly into the ________________. Fuel is added and the resulting mixture is ignited. The resultant increase in __________ causes a substantial increase in _____________.
combustion chambers, temperature, volume
The energy required to drive the compressor is extracted from the ___________________. The remaining energy in the gas stream acts as _________ as the gases pass to atmosphere via the ________________.
stream as it passes through the turbine, thrust, end of the jet pipe
A gas turbine engine that delivers power to a propeller
turboprop engine
Turboprop engines are similar in design to turbojet engines except that the power produced by a turboprop engine is delivered to a ________________ that spins a propeller
reduction gear system
Reduction gearing is necessary in turboprop engines because ____________________ is achieved at much slower speeds than the ____________________.
optimum propeller performance, engine’s operating rpm
Turboprop engines are used extensively in _____________________ aircraft because the combination of jet power and propeller efficiency provides good performance characteristics at speeds between ______________________.
business and commuter type, 300 and 400 miles per hour
most ____________ engines provide the best specific fuel consumption of any gas turbine engine
turboprop
The output from a turboprop engine is the sum of the ______________ developed at the turbine, and the ________________.
shaft horsepower, residual jet thrust
called Equivalent Shaft Horsepower or ESHP
sum of the shaft horsepower developed at the turbine and the residual jet thrust
ESHP
Equivalent Shaft Horsepower
In turboprop, almost all the energy in the gas stream is converted into ______________, to drive both the _____________________.
mechanical power, compressor and the propeller
A gas turbine engine that delivers power to a shaft that can drive something else
turboshaft engine
widely used as auxiliary power units and in industrial applications to drive electrical generators and surface transportation systems
turboshaft engine
Output of a turboprop or turboshaft engine is measured by ______________ rather than thrust.
shaft horse power
Most turboshaft engine incorporates a __________________.
free power turbine
Single spool, turboshaft engine has a ______________________ allowing it to be shorter, stiffer, and lighter. It does however add the requirement for a ________________ to be used in the high-pressure stage. This throws the air out radially so that it can enter the combustion chamber in the correct direction.
reverse flow combustion chamber system, centrifugal compressor
Airflow is similar to turbojet up to a point where it leaves the first stage turbine.
turboshaft engine
Turboshaft: The first stage turbine drives the __________ and the free power turbine converts any remaining energy to _____________ energy.
compressor, mechanical
Both turboprop [TP] and turboshaft [TS] engines use a _________________ to drive an output power shaft for a ______________________
gas turbine core engine, propeller or helicopter rotor
The main difference between the turboprop and turboshaft engine
- turboprop engine might also produce a fraction of its overall thrust via a hot core exhaust jet
- turboshaft engine will have a lower exhaust velocity but correspondingly somewhat higher shaft power as the tradeoff
Turboprops commonly employ a ____________________ to drive the speed reduction gear that in turn drives the ____________ at a lower rotation speed. This is typically also true for turboshaft engines, in driving the ____________ at a significantly lower rotation speed.
free power turbine, propeller, main rotor
consists of a multi-bladed ducted propeller driven by a gas turbine engine
turbofan engine
developed to provide a compromise between the best features of the turbojet and the turboprop
turbofan engine
Turbofan engines have ________________ capability yet retain some of the ________________ of a turboprop.
turbojet-type cruise speed, short-field takeoff capability
The airlines’ choice
turbofan engine
Turbofans are like ____________ but also have a large fan accelerating the air’s entry into the engine and adding to the thrust as an _______________.
turbojets, internal propeller
Engines that have the fan mounted in front of the compressor are called __________________, while turbofan engines that have the fan mounted to the turbine section are called __________________.
forward-fan engines, aft-fan engines
The inlet air that passes through a turbofan engine is usually divided into __________________. One stream passes through the ____________ while a second stream coaxially ____________.
two separate streams of air, engine core, bypasses the engine core
What is responsible for the term bypass engine?
the stream of air that bypasses the engine core in a turbofan engine
When discussing bypass engines there are three terms you must be familiar with; they are ____________________________.
thrust ratio, bypass ratio, and fan pressure ratio
A turbofan engine’s thrust ratio is a comparison of the thrust produced by the ________ to the thrust produced by the _____________.
fan, engine core exhaust
a turbofan’s bypass ratio refers to the ratio of ____________________ to the _______________________.
incoming air that bypasses the core, amount of air that passes through the engine core
Fan pressure ratio is the pressure _____________ to the pressure ________________.
leaving the fan, entering the fan
Turbofans in civil aircraft are generally divided into three classifications based on bypass ratio:
- Low bypass (1:1)
- Medium bypass (2:1 or 3:1)
- High bypass (4:1 or greater)
bypass air to engine air
Bypass Ratio
fan to engine core exhaust
Thrust Ratio
pressure leaving the fan to pressure entering the fan
Fan Pressure Ratio
unducted fan/propfan materials and increase, in percentage, in fuel economy compared to bypass turbofan engines
titanium, lightweight stainless steel, and composite materials; 15 percent
The use of ______________ reduces weight and allows safe operation at tip speeds higher than ______________.
composite blades, conventional blades
Another design encases the propfan in a conventional ____________ which can achieve Mach _____. These engines are known as ___________________.
cowl-type inlet, 0.9, ducted ultra high bypass engines
