The Gas Turbine Engine Part 2

Question 1

Name the component:

This component has two purposes:

1. To convert heat and pressure energy to dynamic energy
2. Turn the gas flow to impinge on the turbine blades at the correct angles.

Answer 1

Nozzle Guide Vanes

Question 2

Name the type of turbine:

These are by far the most common and consist of a stationary section usually called the turbine nozzle and containing guide vanes and nozzle guide vanes which direct the flow of hot gases onto the turbine blades at a suitable angle.

Answer 2

Axial flow turbine

Question 3

Name the type of turbine:

This type is used sometimes on smaller engines and is suitable for use over a small speed range. They work at a fairly high level of efficiency and have the advantages that they are simple and rugged and relatively cheap and easy to manufacture. They work in a similar manner to centrifugal compressor in reverse; the hot gases flowing in at peripheral nozzles to enter the turbine in an inward radial flow exerting a force on the turbine blades and then exiting the engine in an axial direction.

Answer 3

Radial inflow turbine

Question 4

Name the type of turbine:

The type of turbine that use blades of the bucket type.

And the inlet gas flow from the guide nozzles remains unchanged.

Answer 4

Impulse turbine

Question 5

Name the type of turbine:

This type utilises an aerofoil shaped blade, the reaction is much the same.

Answer 5

The reaction turbine

Question 6

Name the type of turbine:

To obtain an even power distribution along the length of the blade it is common practice to employ an impulsive section near the root of the blade changing gradually to a reaction section near the tip.

Answer 6

Reaction impulse turbines

Question 7

The high rotational speeds of the turbine blades results in a phenomenon known as -

A condition in which the blades actually -

Answer 7

blade creep

Stretch due to increased temperatures and centrifugal force.

Question 8

The type of blade mounting which results in better control over gas flow and anti-vibration damping -

Answer 8

Shrouded blades

Question 9

The type of blade mounting which results in less heat being transferred to the disc resulting in lower disc temperatures -

Answer 9

Unshrouded blades

Question 10

One stage on a turbine engine means?

Answer 10

A single rotor disc

Question 11

The exhaust system of a turbine engine consist of three parts:

Answer 11

1. The exhaust Cone
2. The jet pipe
3. The propelling nozzle

Question 12

The purpose of the exhaust cone is to -

Answer 12

stabilise the velocity of the exiting high speed gas flow, maintaining turbulence.

Question 13

The jet pipe is a -

Answer 13

short duct which minimises frictional losses, and is routed to the propelling nozzle.

Question 14

The purpose of the propelling nozzle is to -

Answer 14

increase the momentum of the gases to increase thrust by converting the pressure energy of the gases to kinetic energy

Question 15

which propelling nozzle type:

this nozzle works on the venturi principle; the reduction of area converts pressure energy to kinetic energy; the velocity increases reaching the speed of sound in relation to the exhaust gas temperature at the nozzle exit at which point the nozzle referred to as “choked”. Any further increase in velocity, without an increase in exhaust gas temperature, would result in the development of a normal shock wave, which will immediately result in subsonic flow and a reduction in thrust.

Answer 15

The convergent nozzle

Question 16

which propelling nozzle type:

This type of system is used on engines with an engine pressure ratio(EPR) which is capable of producing exhaust gas velocities which may exceed mach 1 at the nozzle. This enables maximum conversion of energy in the exhaust gas to kinetic energy and, consequently, thrust. As it enters the divergent section the gas accelerates towards the open exit and the reaction to this velocity causes a pressure force acting against the inner wall of the nozzle which increases thrust.

Answer 16

The convergent-divergent nozzle

Question 17

The BPR is?

Answer 17

The ratio of amount of air that is bypassed around the engine core, to the air that passes through the engine core.

Question 18

The turbine type that includes reduction gears?

Answer 18

The turboprop

Question 19

The disadvantage of the fixed shaft turbo-prop engine is the load imposed on the engine by the propeller. During the start this load would result in excessive turbine temperatures in the engine; similarly as the engine develops higher powers the propeller can only be used to transform this power into thrust after the engine has spooled up. This problem is generally overcome by designing the propeller so that it can be selected to very low blade angles called -

Answer 19

Ground Fine Pitch

Question 20

The very fine pitch setting used in ground fine is potentially dangerous in flight because if the propeller blades ever reached this angle in-flight the resulting -

Answer 20

drag would be catastrophic

Question 21

An excellent way of overcoming the problems of the fixed shaft turbo-prop is by the use of a -

This a turbine stage, usually the third or low pressure turbine which is only connected -

The propeller is therefore free to run at its best RPM without affecting -

Answer 21

free turbine

mechanically to the propeller reduction gear.

The engine