Aviation Lubrication Systems Chapter 9

Chapter 9: Lubrication

• This chapter discusses lubrication systems in jet engines, referencing Rolls Royce 1996
• Introduction
  • Facts on lubrication systems
  • Requirement of lubrication systems
  • Types of oil systems
  • Operation of oil systems
  • Components of oil systems
  • Important facts on oil systems
  • Recap

Introduction Lubrication System

• The lubrication system is needed for lubrication and cooling of parts like gears, bearings, and splines
• The system must collect foreign matter—if left in a tank, housing, or gearbox—and protect components made from non-corrosion resistant materials without significant deterioration

Purpose of Turbine Engine Lubrication

• Lubrication reduces friction and wear
• Cleaning removes metal particles to prevent further damage
• Cooling prevents material degradation and seizure
• Oil damping reduces vibration

Requirements of Aviation Lubricants

• Low volatility reduces evaporation at high altitude
• Anti-forming characteristics ensure positive lubrication
• High flash point minimizes ignition risk
• Wide temperature range ensures proper operation across various temperatures
• Excellent film strength ensures cohesion and adhesion, while a high viscosity index ensures viscosity retention during heating

Types of Oil System

• Discusses various types of oil systems, likely including wet sump and dry sump. (Further detailed information about these follows)

Wet Sump Lubrication System

• The oldest design, rarely used in modern engines
• Oil is contained within an engine sump, submerging lubricated parts in oil

Dry Sump Lubrication System

• Used in most modern turbine engines
• Consists of pressure system to deliver oil, scavenge pumps to return it, and a breather vent
• Oil is delivered to parts by a pressure pump and returned by scavenge pumps

A Full Flow Type Oil System (Dry Sump)

• Achieves desired oil flow rates based on maximum RPM
• Excess oil returns to the supply pump via a pressure relief valve
• Pump size is determined by maximum engine speed requirements

Operation of Oil System

• Overall view of a full flow lubricating system, including components like oil pumps, filters, sensors, tanks and more.

• Operation (Supply): Oil flows through filters to a heat exchanger, then to a cooler, and across a manifold to various engine parts. If pressure is too high a relief valve returns it to the tank.

• Operation (Scavenge Line): Oil is removed from components, then through a filter, then through a sensor and into the tank.

• Operation (Breather Line): Oil mist is removed from the breather air, which is vented overboard.

Components of Oil System

• Details of common components:
  • Oil Tank
  • Pressure & Scavenge Pumps
  • Pressure Relief Valves
  • Fuel Oil Heat Exchanger / Oil Cooler
  • Air Oil Heat Exchanger
  • Deoiler / Centrifugal Breather
  • Magnetic Chip Detectors
  • Filters

1. Oil Tank

• Typically mounted on the engine or in the external gearbox
• Provisions for draining and replenishment
• Sight glass or dipstick for manually checking oil level

2. Oil Pump Assembly/Oil Pump

• Gear pumps: Pair of meshing steel gears in an aluminum casing, used for delivering oil under pressure and/or returning oil to the sump

• Other pumps: Vane type, etc

• Oil pumps are crucial for efficient engine operation

• Pump drive shafts don't have weak shear points; ensuring continuous oil supply, regardless of damage.

• Supply and scavenge pumps are often integrated within an assembly

3. Pressure Relief Valve System

• Controls oil flow to bearing chambers by limiting pressure
• Uses a spring-loaded valve to return excess oil to the tank or pump inlet, when pressure exceeds a predetermined design value

4. Fuel-cooled Oil Cooler / Air-cooled Oil Cooler

• Transfers heat from oil to fuel / air to reduce oil temperature
• Multiple tubes carry fuel alongside oil streams directed by baffle plates
• Uses either fuel or air as a cooling medium

5. Air/Oil Heat Exchanger

• Facilitates heat transfer between oil and air

6. Centrifugal Breather

• Removes oil mist from breather air through centrifugal force

7. Magnetic Chip Detector

• Catches ferrous metal particles to prevent bearing damage
• Using magnetic plugs, or chip detectors,
• Designed for removal during inspection for condition monitoring purposes.

8. Filter

• Prevents foreign matter from circulating through the system
• Coarse strainers at oil tank output or prior to oil pump inlets prevent damage
• Fine pressure filters catch very small particles that could block oil jets.

8. Electronic Cleaning of a Cleanable Filter

• Traditional solvent cleaning is still frequently used.

Important Facts on Oil System

• Most modern turbine engines use synthetic oils (e.g., Mobil jet type II oil, Exxon 2380)

• Oil tanks are typically checked 10 minutes after shutdown

• Oil levels are tracked on sight glasses, gauges or LED screens

• Specific values of low oil pressure / high temperature trigger an immediate engine shutdown

Recap

• Covers the need for lubrication, the basic principles/purposes of engine lubrication,
• distinctions between wet and dry sump systems, hot oil tank full flow diagram with component operations,
• critical facts concerning oil systems that cause engine shutdowns

This quiz covers Chapter 9 on lubrication systems in jet engines, focusing on their importance, types, and operational aspects, referencing Rolls Royce 1996. Learn key facts about the requirements and components of aviation lubrication to enhance engine performance and reliability.