Module 2

Question 1

cExplain Turbojets

Answer 1

1. Air is compressed in the compressor
2. Burned in the combustion chamber,
3. Expands and spins the turbine which in turn drives the compressor (self-sustaining),
4. leaves the exhaust at high velocities.

Question 2

What are types of gas turbine engine

Answer 2

1. Turbojet
2. Turboprop
3. Turboshaft
4. Turbofan

Question 3

It is the ratio of turbine discharge pressure to the inlet air pressure.

Answer 3

Engine Pressure Ratio

Question 4

When a compressor and turbine are
joined on one shaft, the unit is called a
‘____________’.

Answer 4

spool

Question 5

Explain the Airflow through turbojet

Answer 5

From the compressor, the air is fed
directly into the combustion chambers.Fuel is added and the resulting mixture is ignited. The resultant increase in temperature causes a substantial increase
in volume.

The energy required to drive the
compressor is extracted from the stream as it passes through the turbine. The remaining energy in the gas stream acts as thrust as the gases pass to atmosphere via the end of the jet pipe.

Question 6

It is a gas turbine engine that delivers
power to a propeller.

Answer 6

turboprop

Question 7

In terms of design, what is the difference of a turboprop and a turbojet engine?

Answer 7

the power produced by a turboprop engine is delivered to a reduction gear system that spins a propeller

Question 8

_______________ is necessary in turboprop engines because optimum propeller performance is achieved at
much slower speeds than the engine’s
operating rpm.

Answer 8

Reduction gearing

Question 9

Reduction gearing is necessary in turboprop engines because optimum propeller performance is achieved at
much____________ than the ________________.

Answer 9

slower speeds
engine’s operating rpm

Question 10

Turboprop engines are used extensively in_________ and _____________ type aircraft because the combination of _____________ and __________________ provides good performance characteristics at speeds
between ___________________

Answer 10

business
commuter
jet power
propeller efficiency
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

What is the sum of of the shaft horsepowerdeveloped at the turbine, and the residual jet thrust.

Answer 12

Equivalent Shaft Horsepower

Question 13

Explain airflow through turboprop

Answer 13

The output from a turboprop engine is
the sum of the shaft horsepower
developed at the turbine, and the
residual jet thrust. This is called
Equivalent Shaft Horsepower or
ESHP.

In turboprop, almost all the energy in
the gas stream is converted into
mechanical power, to drive both the
compressor and the propeller.

Question 14

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

Answer 14

turboshaft

Question 15

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

Answer 15

turboshaft engines

Question 16

turboshaft engines are widely used as __________________-and in ________________________ to drive electrical generators and surface transportation systems.

Answer 16

auxiliary power units
industrial applications

Question 17

Most of these engines incorporate a free power turbine

Answer 17

turboshaft

Question 18

_________________ has areverse flow combustion chamber system allowing it to be shorter, stiffer, and lighter.

Answer 18

Single spool, turboshaft engine

Question 19

Single spool, turboshaft engine add the requirement for a _________________ to be used in the high-pressure stage.

Answer 19

centrifugal compressor

Question 20

This throws the air but radially so that it can enter the combustion chamber in the correct direction.

Answer 20

centrifugal compressor

Question 21

The airflow through a turboshaft is similar to turbojet up to a point where it leaves the __________________.

Answer 21

first stage turbine

Question 22

In a turboshaft, the ______________drives the compressor and the ____________________ converts any remaining energy to mechanical energy.

Answer 22

first stage turbine
free power turbine

Question 23

Both ________________and ________________ engines use a gas turbine core engine to drive an output power shaft for a propeller or helicopter rotor

Answer 23

turboprop [TP] and turboshaft [TS]

Question 24

Both turboprop [TP] and turboshaft [TS] engines use a gas turbine core engine to drive an _____________ for a _____________ or___________

Answer 24

output power shaft
propeller
helicopter rotor

Question 25

The main difference between the TP and TS is that ___________________________________________________________________________________________________________________________________________________________________

Answer 25

a TP engine might also produce a fraction of its overall thrust via a hot core exhaust jet, while a conventional TS engine will have a lower exhaust velocity but correspondingly somewhat higher shaft power as the tradeoff

Question 26

TPs commonly employ a _________________ to drive the speed reduction gear that in turn drives the propeller at a lower rotation speed.

Answer 26

free power turbine

Question 27

TPs commonly employ a free power turbine to drive the ________________ that in turn drives the ____________ at a lower rotation speed. This is typically also true for TS engines, in driving the main rotor at a significantly lower rotation speed.

Answer 27

speed reduction gear propeller

Question 28

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

Answer 28

turbofan engine

Question 29

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

Answer 29

Turbofans

Question 30

Turbofans were developed to provide a compromise between the best features of the _______________ and the _______________.

Answer 30

turboprop turbojet

Question 31

What similarities do turbofan engines share with both turbojet and turboprop engines?

Answer 31

Turbofans have "turbojet-like cruise speeds" and "turboprop-like short-field takeoff capability"

Question 32

It is the airline's choice

Answer 32

turbofan

Question 33

Turbofans are like Turbojets but also have a _____________ accelerating the air’s entry into the engine and adding to the thrust as an internal propeller.

Answer 33

large fan

Question 34

Engines that have the fan mounted in front of the compressor are called _____________

Answer 34

forward-fan engines

Question 35

turbofan engines that have the fan mounted to the turbine section are called _________________.

Answer 35

aft-fan engines

Question 36

The inlet air that passes through a turbofan engine is usually divided into _______ separate streams of air. One stream passes through the_________ while the second stream _________________

Answer 36

Two engine core coaxially bypasses the engine core.

Question 37

It is this bypass stream of air that is responsible for the term ______________-.

Answer 37

bypass engine

Question 38

It is this ______________that is responsible for the term bypass engine.

Answer 38

bypass stream of air

Question 39

When discussing bypass engines there are three terms you must be familiar with; they are _________________, ____________________, ___________________

Answer 39

thrust ratio, bypass ratio, and fan pressure ratio

Question 40

A ____________________ is a comparison of the thrust produced by the fan to the thrust produced by the engine core exhaust.

Answer 40

turbofan engine's thrust ratio

Question 41

A __________________ refers to the ratio of incoming air that bypasses the core to the amount of air that passes through the engine core.

Answer 41

turbofan's bypass ratio

Question 42

__________________- is the pressure leaving the fan to the pressure entering the fan.

Answer 42

Fan pressure ratio

Question 43

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

Answer 43

Low bypass Medium bypass High bypass

Question 44

what are the ratios of these classifications? 1.Low bypass 2. Medium bypass 3. High bypass

Answer 44

1. 1:1 2. 2:1 or 3:1 3. 4:1 or greater

Question 45

ratio of bypass air to engine air

Answer 45

bypass ratio

Question 46

ratio of fan to engine core exhaust

Answer 46

thrust ratio

Question 47

the ratio of pressure leaving the fan to pressure entering the fan

Answer 47

Fan Pressure Ratio

Question 48

These new designs utilize titanium, lightweight stainless steel, and composite materials to surpass the fuel economy of several high bypass turbofan engines by more than 15 percent.

Answer 48

unducted fan

Question 49

What materials are used in unducted fans to improve fuel economy?

Answer 49

Titanium, lightweight stainless steel, and composite materials

Question 50

By how much do these unducted fans surpass the fuel economy of high bypass turbofan engines?

Answer 50

15%

Question 51

The use of________________ reduces weight and allows safe operation at tip speeds higher than conventional blades.

Answer 51

composite blades

Question 52

Another design of unducted fan encases the ____________ in a ________________________________which can achieve ___________. These engines are known as __________________________

Answer 52

propfan conventional cowl-type inlet Mach 0.9 Ducted ultra high bypass engines.