Topic 02 - Types of Gas Turbine Engines

Question 1

The basic operating principles of a turbojet engine

Answer 1

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.

Question 2

What produces thrust in a turbojet engine?

Answer 2

difference in velocity in the inlet and exit

Question 3

EPR

Answer 3

engine pressure ratio

Question 4

What is engine pressure ratio

Answer 4

the ratio of turbine discharge pressure to the inlet air pressure

Question 5

What is a spool in turbojet

Answer 5

when a compressor and turbine are joined on one shaft

Question 6

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 _____________.

Answer 6

combustion chambers, temperature, volume

Question 7

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 ________________.

Answer 7

stream as it passes through the turbine, thrust, end of the jet pipe

Question 8

A gas turbine engine that delivers power to a propeller

Answer 8

turboprop engine

Question 9

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

Answer 9

reduction gear system

Question 9

Reduction gearing is necessary in turboprop engines because ____________________ is achieved at much slower speeds than the ____________________.

Answer 9

optimum propeller performance, engine’s operating rpm

Question 10

Turboprop engines are used extensively in _____________________ aircraft because the combination of jet power and propeller efficiency provides good performance characteristics at speeds between ______________________.

Answer 10

business and commuter type, 300 and 400 miles per hour

Question 11

most ____________ engines provide the best specific fuel consumption of any gas turbine engine

Answer 11

turboprop

Question 12

The output from a turboprop engine is the sum of the ______________ developed at the turbine, and the ________________.

Answer 12

shaft horsepower, residual jet thrust

Question 13

called Equivalent Shaft Horsepower or ESHP

Answer 13

sum of the shaft horsepower developed at the turbine and the residual jet thrust

Question 14

ESHP

Answer 14

Equivalent Shaft Horsepower

Question 15

In turboprop, almost all the energy in the gas stream is converted into ______________, to drive both the _____________________.

Answer 15

mechanical power, compressor and the propeller

Question 16

A gas turbine engine that delivers power to a shaft that can drive something else

Answer 16

turboshaft engine

Question 17

widely used as auxiliary power units and in industrial applications to drive electrical generators and surface transportation systems

Answer 17

turboshaft engine

Question 18

Output of a turboprop or turboshaft engine is measured by ______________ rather than thrust.

Answer 18

shaft horse power

Question 19

Most turboshaft engine incorporates a __________________.

Answer 19

free power turbine

Question 20

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.

Answer 20

reverse flow combustion chamber system, centrifugal compressor

Question 21

Airflow is similar to turbojet up to a point where it leaves the first stage turbine.

Answer 21

turboshaft engine

Question 22

Turboshaft: The first stage turbine drives the __________ and the free power turbine converts any remaining energy to _____________ energy.

Answer 22

compressor, mechanical

Question 23

Both turboprop [TP] and turboshaft [TS] engines use a _________________ to drive an output power shaft for a ______________________

Answer 23

gas turbine core engine, propeller or helicopter rotor

Question 24

The main difference between the turboprop and turboshaft engine

Answer 24

- 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

Question 25

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.

Answer 25

free power turbine, propeller, main rotor

Question 26

consists of a multi-bladed ducted propeller driven by a gas turbine engine

Answer 26

turbofan engine

Question 27

developed to provide a compromise between the best features of the turbojet and the turboprop

Answer 27

turbofan engine

Question 28

Turbofan engines have ________________ capability yet retain some of the ________________ of a turboprop.

Answer 28

turbojet-type cruise speed, short-field takeoff capability

Question 29

The airlines’ choice

Answer 29

turbofan engine

Question 30

Turbofans are like ____________ but also have a large fan accelerating the air’s entry into the engine and adding to the thrust as an _______________.

Answer 30

turbojets, internal propeller

Question 31

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 __________________.

Answer 31

forward-fan engines, aft-fan engines

Question 32

The inlet air that passes through a turbofan engine is usually divided into __________________. One stream passes through the ____________ while a second stream coaxially ____________.

Answer 32

two separate streams of air, engine core, bypasses the engine core

Question 33

What is responsible for the term bypass engine?

Answer 33

the stream of air that bypasses the engine core in a turbofan engine

Question 34

When discussing bypass engines there are three terms you must be familiar with; they are ____________________________.

Answer 34

thrust ratio, bypass ratio, and fan pressure ratio

Question 35

A turbofan engine's thrust ratio is a comparison of the thrust produced by the ________ to the thrust produced by the _____________.

Answer 35

fan, engine core exhaust

Question 36

a turbofan's bypass ratio refers to the ratio of ____________________ to the _______________________.

Answer 36

incoming air that bypasses the core, amount of air that passes through the engine core

Question 37

Fan pressure ratio is the pressure _____________ to the pressure ________________.

Answer 37

leaving the fan, entering the fan

Question 38

Turbofans in civil aircraft are generally divided into three classifications based on bypass ratio:

Answer 38

- Low bypass (1:1) - Medium bypass (2:1 or 3:1) - High bypass (4:1 or greater)

Question 39

bypass air to engine air

Answer 39

Bypass Ratio

Question 40

fan to engine core exhaust

Answer 40

Thrust Ratio

Question 41

pressure leaving the fan to pressure entering the fan

Answer 41

Fan Pressure Ratio

Question 42

unducted fan/propfan materials and increase, in percentage, in fuel economy compared to bypass turbofan engines

Answer 42

titanium, lightweight stainless steel, and composite materials; 15 percent

Question 43

The use of ______________ reduces weight and allows safe operation at tip speeds higher than ______________.

Answer 43

composite blades, conventional blades

Question 44

Another design encases the propfan in a conventional ____________ which can achieve Mach _____. These engines are known as ___________________.

Answer 44

cowl-type inlet, 0.9, ducted ultra high bypass engines