Parts I Have Missed

Question 1

What is the purpose of lubrication

Answer 1

No answer!!!!!!!!!

Question 2

What are the two stages of lubrication

Answer 2

Boundary - condition bordering on seizure
Film - as rotation commences oil pressure will keep the surfaces apart

Question 3

What is friction?

Answer 3

Friction is the resistance to movement felt when one surface is moved across another surface.

Question 4

What can friction generate?

Answer 4

Friction can generate heat and cause considerable wear between parts.

Question 5

What factors affect the amount of friction generated?

Answer 5

The amount of friction depends
surface finish,
material,
relative operating speed,
surface loading.

Question 6

How do lubricants affect friction?

Answer 6

Lubricants reduce friction by introducing a wetting agent between moving surfaces.

Question 7

What is the purpose of a lubricant?

Answer 7

The purpose of a lubricant is to prevent surfaces from touching, thereby eliminating friction and wear.

Question 8

What are the two basic phases of lubrication?

Answer 8

The two basic phases are Boundary Lubrication and Film (hydro-dynamic) Lubrication.

Question 9

What occurs during Boundary Lubrication?

Answer 9

In Boundary Lubrication, the oil film is reduced to almost nothing, bordering on seizure.

Question 10

What occurs during Film Lubrication?

Answer 10

In Film Lubrication, oil pressure keeps the surfaces apart, supporting the shaft.

Question 11

What is the lubrication requirement for gas turbine engine shafts?

Answer 11

Shafts are supported in lightly-loaded bearings and require quick flowing, low viscosity oil.

Question 12

Why is cooling important in gas turbine engines?

Answer 12

Cooling is crucial to prevent excessive heat from being transmitted to engine components.

Question 13

What is a requirement for oil in turbo shaft engines?

Answer 13

The oil must withstand high pressure across the gears and bearings.

Question 14

What is a requirement for oil during start-up?

Answer 14

The oil must be thin to enable a rapid rise in RPM without blowing seals.

Question 15

No question

Question 16

What type of oil is used in gas turbine engines?

Answer 16

The GTE oil is a synthetic oil (OX–).

Question 17

What are the characteristics of GTE oil?

Answer 17

highly corrosive,
reacts with natural rubber compounds,
withstand high temperatures ,
injurious to the human body.

Question 18

How does GTE oil behave in a gas turbine system?

Answer 18

The oil does not become contaminated by the product of combustion, making frequent oil changes unnecessary.

Question 19

What is the oil consumption rate in gas turbine engines?

Answer 19

The oil consumption rate is low, allowing for a compact oil system that is integral to the engine.

Question 20

What are the two types of oil systems in gas turbine engines?

Answer 20

Gas turbine engines may have a ‘dry sump’ system with a separate oil tank or a ‘wet sump’ system where oil is contained in the sump.

Question 21

How is oil circulated in gas turbine engines?

Answer 21

Oil is circulated through the engine by a pump and is normally returned to the tank or sump by one or more scavenge pumps.

Question 22

What are the main bearings in gas turbine engines?

Answer 22

The main bearings support the turbine and compressor assemblies and usually consist of roller and ball bearings.

Question 23

What are the uses of roller and ball bearings?

Answer 23

Roller bearings are used for radial and axial loads, while ball bearings are used for axial or thrust loads.

Question 24

What is the purpose of squeeze film bearings?

Answer 24

Squeeze film bearings minimize vibration by reducing the effect of dynamic loads transmitted from rotating assemblies to the bearing housings.

Question 25

How do squeeze film bearings work?

Answer 25

They have a small clearance filled with feed oil between the outer track of the bearing and the housing, modifying the radial action of the rotating assembly.

Question 26

What benefits do squeeze film bearings provide?

Answer 26

They reduce the vibration level of the engine and the possibility of damage by fatigue.

Question 27

What are the various types of seals used to prevent oil migration?

Answer 27

The types of seals include Carbon, Brush, Lip, and Labyrinth.

Question 28

Which seals rely on physical contact with the rotating assembly?

Answer 28

Carbon, Brush, Lip

Question 29

How do Labyrinth seals function?

Answer 29

Labyrinth seals use cooling air directed inwards to prevent oil escape from the bearing surface.

Question 30

What types of seals are commonly found in lubrication systems?

Answer 30

Common types include thread and continuous groove (labyrinth) seals, as well as ring, hydraulic, and carbon seals.

Question 31

What is the latest type of seal used?

Answer 31

The latest type of seal is the brush seal, which consists of a static ring of wire bristles against a hard ceramic coating on the rotating shaft.

Question 32

No question !!!!

Answer 32

Ahhh

Question 33

What are the two main methods of lubricating and cooling main bearings?

Answer 33

1. Oil Mist 2. Oil Jet

Question 34

What is the Oil Mist lubrication method?

Answer 34

Compressed air is used to atomise the oil at nozzles adjacent to the bearings, assisting in cooling. The air can later be separated from the oil.

Question 35

What is the Oil Jet lubrication method?

Answer 35

Oil jets are placed close to the bearings and directed into the clearance spaces, protected against blockage by thread type filters. This method is controllable and reliable.

Question 36

What is the purpose of an oil system?

Answer 36

To provide storage facilities for an adequate supply of oil and to deliver it to various parts of the engine at a suitable rate for efficient lubrication and cooling.

Question 37

What are the two types of oil systems traditionally used in gas turbines?

Answer 37

1. Recirculatory system 2. Expendable (Total loss) system

Question 38

What is a Recirculatory Oil System?

Answer 38

In this system, oil is distributed and returned to the oil tank by pumps.

Question 39

What are the two types of Recirculatory systems?

Answer 39

1. Pressure Relief Valve System 2. Full Flow System

Question 40

Are Expendable oil systems commonly used?

Answer 40

No, expendable systems are now very rarely used.

Question 42

What is a Pressure Relief Valve Recirculatory System?

Answer 42

It is a lubrication system where the flow of oil to bearings is controlled by a relief valve that limits maximum pressure in the feed line.

Question 43

How does the pressure relief valve operate in relation to engine speed?

Answer 43

As the oil pump is driven by the engine, the pressure rises with spool speed. Above a predetermined speed, the relief valve opens to allow excess oil to return to the tank.

Question 44

What happens to oil pressure at higher engine speeds in a Pressure Relief Valve system?

Answer 44

It ensures a constant oil pressure by allowing excess oil to spill back to the tank.

Question 45

What is the effect of the pressure relief valve setting on oil pressure?

Answer 45

The pressure at idle and max RPM is less than optimum.

Question 46

What distinguishes a Full Flow Lubrication System from a Pressure Relief Valve system?

Answer 46

The Full Flow Lubrication System does not use a pressure relief valve and allows pump delivery to supply oil feeds directly to bearings.

Question 47

What is the advantage of a Full Flow Lubrication System?

Answer 47

It allows the use of smaller pumps designed to supply sufficient oil at maximum engine RPM.

Question 48

What are the advantages of a Full Flow System

Answer 48

Provides a suitable oil flow At a Suitable pressure Can be Used in All engine speed

Question 49

What components are included in the typical oil system?

Answer 49

OIL TANK, PRESSURE PUMP, PRV, FILTER, CHECK VALVE, FINE FILTER, ENGINE

Question 50

What does the spur gear type pump do?

Answer 50

Builds system pressure to PRV setting.

Question 51

What is the purpose of the pressure pump?

Answer 51

Maintains system pressure.

Question 52

What does the filter do in the oil system?

Answer 52

Collects debris from the pumps and gears.

Question 53

What does the check valve prevent?

Answer 53

Prevents oil flooding into the engine whilst stopped.

Question 54

What does the fine filter protect?

Answer 54

Protects the oil jets.

Question 55

What components are protected by the oil jets?

Answer 55

Front-Centre-Rear Bearings, Accessory Drives and Gear Trains.

Question 56

Where are labyrinth seals used?

Answer 56

They are used in the reduction gearbox.

Question 57

What is the function of the scavenge pumps?

Answer 57

Collects large FE particles and returns oil to the tank via cooler.

Question 58

How does the oil cooler work?

Answer 58

Air or fuel cooled, with a bypass to protect the matrix.

Question 59

How many pressure pumps are typically used?

Answer 59

Normally there is only one pressure pump.

Question 60

What determines the number of scavenge pumps needed?

Answer 60

The number of areas that need to be fed oil.

Question 61

What is the capacity relationship between scavenge pumps and pressure pumps?

Answer 61

Scavenge pumps will have a larger capacity than pressure pumps.

Question 62

Where is a magnetic plugs in the oil system?

Answer 62

To be located in each return line.

Question 63

What is the effect of aeration on oil volume?

Answer 63

It causes a greater volume of oil due to air absorption.

Question 64

What are two ways to remove air from the oil?

Answer 64

Using baffles or a centrifugal breather.

Question 65

What are baffles in the oil tank?

Answer 65

They are plate arrangements that separate air from oil.

Question 67

What is a centrifugal breather?

Answer 67

A rotating component driven from the accessory gearbox.

Question 68

How does the centrifugal breather work?

Answer 68

The returning oil/air mix enters the component and runs over de-aerator segments that are spinning.

Question 69

What is the function of the de-aerator segments in a centrifugal breather?

Answer 69

They use centrifugal action to separate the heavier oil from the air.

Question 70

What happens to the separated oil in a centrifugal breather?

Answer 70

The oil drains back down into the tank.

Question 71

What happens to the air in a centrifugal breather?

Answer 71

The air is vented to atmosphere.