Emilys

Question 1

How do you increase thrust of an turbo jet?

Answer 1

• Increase Mass flow rate
  -Increase exit speed

Question 2

Why is it better to increase mass flow rate rather then exit speed to get more thrust?

Answer 2

Because propulsive efficiency decreases with speed increase

Question 3

Which way round rotor stator in turbine vs compressor?

Answer 3

Compressor- rotor then stator
Turbine- Stator then rotor

Question 4

What advantages do centrifugal compressors have over axial compressors?

Answer 4

Can produce a large pressure rise for lower mass flow applications

Question 5

Why are turbines normally more efficient then compressors

Answer 5

Easier to get air from high to low pressure/ temp then low to high

Question 6

What needs to be kept in mind when designing inlets?

Answer 6

Needs to keep the air as uniform as possible

Question 7

What is Augmentation?

Answer 7

Temporary increase of thrust

Question 8

Examples of Augemenation?

Answer 8

Liquid injection and afterburning

Question 9

What happens in liquid injection (a method to increase thrust temporarily)

Answer 9

spray water methanol mix during take off and climb- increases mass flow rate

Question 10

What happens in after burning (a method to increase thrust temporarily)

Answer 10

Burn additional fuel as its being ejected- doesn’t matter if temp goes up too much as there are no moving parts that can melt

Question 11

What advantages and disadvantages does a gear box add to a two spooled turbo fan?

Answer 11

• Fan can go slower while last turbine goes faster to extract maximum energy,
  but lots of losses in the gear box

Question 12

In a compressor what does a rotor do in terms of speed and pressure

Answer 12

increases axial speed doesn’t change pressure

Question 13

In a compressor what does a stator do in terms of speed and pressure

Answer 13

decreases axial speed increases pressure

Question 14

in the stator of the compressor is there a temperature change?

Answer 14

no

Question 15

What happens if reaction turns negative

Answer 15

Compressor acts like a turbine

Question 16

if de haller criteria is too low what do you do?

Answer 16

lower temp change

Question 17

What does 50% reaction mean?

Answer 17

Half the pressure change done with velocity in stator then half done by rotor with actual pressure change.

Question 18

What are the advantages and disadvantages on having more compressor stages

Answer 18

Advantage weighs less
But if each stage has to do too much then diffusion factor increases and means boundary layers more likely to seperate, efficiency drops.

Question 19

What is the amount of blades in a stage called

Answer 19

pitch

Question 20

What effect does having a bigger pitch have

Answer 20

less blades but thicker and more likely to separate boundary layers

Question 21

With a centrifugal compressor how do you increase mass flow

Answer 21

make it double sides with a double inlet

Question 22

Out of axial and centrifugal compressors which is better at dealing which bird strikes

Answer 22

Centrifugal

Question 23

What does the power input factor contain?

Answer 23

friction not realted to flow

Question 24

Out of axial and centrifugal compressors which is better at dealing with big mass flows

Answer 24

axial

Question 25

What do you need to conserve in the conbuster

Answer 25

pressure

Question 26

How do you try not to loose pressure in a conductor?

Answer 26

slow down speed

Question 27

Is is better to have laminar or turbulent flow in a combustor?

Answer 27

Turbulent so there is sufficient mixing

Question 28

Describe tubular combustor system?

Answer 28

a circle of combustion chambers

Question 29

What are the advantages and disadvantages of a tubular combustor system?

Answer 29

Robust, easy to test just a section of it

Bulky and heavy

Question 30

Describe a annular combustor system

Answer 30

donut shaped combustor

Question 31

Why is an annular combustor better/worse then a tubular?

Answer 31

Light, minimum pressure loss,
but less strong and also have to test the whole thing at the same time

Question 32

How is a turbo annular

Answer 32

less pressure loss but less compact and requires cooling

Question 33

How do you want fuel to be sprayed out of spray

Answer 33

As fully developed spray not dribble

Question 34

What are the disadvantage of growing biofules

Answer 34

Take field space away from food and also kinda emits the same amout

Question 35

Why is kerosene great?

Answer 35

Stable at a wide range of temp
Highly calorific

Question 36

How can you tell the difference between turbine and compressor blades in terms of area?

Answer 36

in a turbine it minimised the area whereas in a compressor it increases the area at the tip

Question 37

Where in the turbine experiences the highest stress?

Answer 37

The root- gets the hottest

Question 38

What kind of flow gets the most cooling?

Answer 38

Turbulent

Question 39

Impingement tubes what are they and how do they promote cooling

Answer 39

High pressure air, goes through small holes

Question 40

What is passage cooling and how does it promote cooling

Answer 40

Long passage ways of air from cooler part of system piped through channels designed to make it turbulent.

Question 41

What is film cooling?

Answer 41

Using fuel from internal cooling and can pump it in a way to create a fiom between gases and the blades metal surface

Question 42

What is the problem with loads of cooling things

Answer 42

expensive to build and also film cooling can disrupt flow and make it less efficient