Engines 8: Lubricants and Lubrications System

Question 1

What is the purpose of lubricants?

Answer 1

To reduce friction from metal to metal contact

Question 2

What is the purpose of a lubrication system?

Answer 2

To provide an adequate supply of clean oil to bearings and gears at the proper temperature and pressure.

1. Provide clean oil to components at proper temperature and pressure
2. Remove heat from engine
3. Remove contaminants

Question 3

Why do gas turbine engines use synthetic oil?

Answer 3

It is better suited for higher temperatures

Question 4

What are the advantages of synthetic oils?

Answer 4

• High stability at high temperatures
• Less coke deposits

Question 5

What are the disadvantages of synthetic oils?

Answer 5

• Very corrosive
• A short shelf life of 3 years

Question 6

Viscosity

Answer 6

The property of a fluid that resists the force tending to cause the fluid flow

Resistane to flow

Question 7

What is the relationship between temperature and viscosity?

Answer 7

Inverse relationship; as temperature increases, viscosity decrease.

Question 8

What are the different types of oil contamination?

Answer 8

• Metallic particles
• Corking (carbon deposits)
• Sand and dirt

Question 9

What are the types of different lubrication systems?

Answer 9

Wet sump lubrication system
Dry sump lubrication system

Question 10

What is the difference between a wet sump system and a dry sump system?

Answer 10

A wet sump system has its reservoir stored internally in the engine and a dry sump system has its reservoir stored externally from the engine

Question 11

What are the disadvantages of a wet sump system?

Answer 11

• Oil supply is limited by sump capacity
• Harder to cool the oil
• Non adaptable to unusual attitudes

Question 12

What are the advantages of a dry sump system?

Answer 12

• Temperature/viscosity can be better controlled
• Can carry a larger oil supply

Question 13

What are the three subsystems of a dry sump system?

Answer 13

Pressure subsystem
Scavenge subsystem
Breather pressurizing subsystem

Question 14

What is the purpose of the pressure subsystem?

Answer 14

Supplies oil under pressure to the engine main bearings and accessory drive gear

Question 15

What is the purpose of the scavenge subsystem?

Answer 15

To return oil from the bearings and accessory section to the oil tank and to provide cooling for the oil

Question 16

What is the purpose of the breather pressurizing system?

Answer 16

1. Minimizes oil leaks
2. Ensure proper spray patterns

This is done by ensuring that sea level pressure is maintained in the oil tank and engine bearing compartments

Question 17

How does the pressure subsystem work?

Answer 17

An engine driven pump receives oil from the oil tank and sends it through an oil filter. After the oil filter, the oil travels to the pressure relief valve. After the relief valve, the oil travels through tubing to lubricate the engine bearings and accessory gear box by being sprayed out of nozzles in the engine

Question 18

Oil Pressure Gauge

Answer 18

Displays oil pump discharge pressure

Indicates if a pump is working normally

Question 19

Oil Temperature Gauge

Answer 19

Displays temperature of oil prior to entering the engine bearings

Indicates scavenge system performance

Question 20

Oil Pressure Relief Valve

Answer 20

Limits the max pressure within the system

(Preset to relieve pressure by bypassing oil back to the inlet pump whenever pressure exceeds a safe limit)

Question 21

What is the purpose of the oil coolers in the scavenge system?

Answer 21

To reduce the temperature of the oil so it can be recirculated throughout the system

Question 22

What are the two types of oil coolers?

Answer 22

Air-oil coolers
Fuel-oil coolers

Question 23

How does an air-oil cooler work?

Answer 23

Uses ambient air, passing through its fins, to cool the oil

Question 24

How does an fuel-oil cooler/heat exchanger work?

Answer 24

Oil enters an inlet port, flows around the fuel lines, and goes out the outlet port

Question 25

How does oil bypass the fuel-oil cooler/heat exchanger if cooling is not needed?

Answer 25

Through the oil temperature regulating valve

Question 26

Oil Temperature Regulating Valve

Answer 26

Directs the flow of return oil into the fuel-oil cooler to allow cooling

Question 27

Fuel Temperature Sensing Switch

Answer 27

A switch located at the fuel exit of the fuel-oil cooler. The switch sends a signal to the air-cooler to open the doors to allow air to pass through when the fuel temperature gets too hot.