Lubrication Part 1 - Aircraft Gas Turbine Engines #22

Summary

The script discusses the multifaceted role of lubricants in engines, emphasizing beyond reducing friction. It details how lubricants remove impurities, prevent corrosion, cool bearing surfaces, and serve as hydraulic fluid. It outlines two engine lubrication systems: the pressure relief valve system, which controls oil flow and pressure, and the full flow system, which operates without a pressure relief valve for direct oil supply. The script also covers the components of these systems, including oil pumps, filters, relief valves, and coolers, highlighting their functions in maintaining engine efficiency and longevity.

Takeaways

• 🔧 Lubricants in engines serve multiple purposes beyond reducing friction, including cleaning, cooling, and protecting engine components.
• 🧼 The oil filter plays a crucial role in removing dirt and impurities from the oil to prevent damage to engine bearings and blocks.
• 🛠️ Engine bearings, made of steel, are protected from oxidation through a coating of oil, which also minimizes corrosion within the engine.
• 🌡️ Lubricants help in cooling the bearing surfaces, especially near turbines, by transferring heat to the oil cooler and dissipating it into the atmosphere.
• ⚙️ Some engines use engine oil as a hydraulic fluid for functions like controlling the pitch of propeller blades in turboprop engines.
• 🔄 Gas turbine engines have a self-contained recirculation system where oil is distributed and returned to the tank by pumps.
• 💧 The pressure relief valve system controls oil flow to bearing chambers by diverting excess volume back to the pump inlet, maintaining constant pressure.
• 🔧 The full flow system allows direct supply of oil to feed jets without a pressure relief valve, using smaller pumps due to less oil volume.
• 🚫 The oil differential pressure switch and low oil pressure warning switch are safety features that alert ground crews and pilots to potential issues.
• 🛢️ The oil tank, whether separate or part of the engine, must have provisions for oil supply and a method to determine its contents, such as a sight glass or dipstick.

Q & A

What is the primary reason for using a lubricant in an engine?

The primary reason for using a lubricant in an engine is to reduce friction between moving parts.

Why is it necessary to have a lubricant even in a perfectly clean engine?

Even in a perfectly clean engine, small amounts of dirt or impurities can find their way inside, and a lubricant is needed to remove this dirt from the oil to prevent damage to bearings or blocks.

How does the oil keep the engine clean?

The oil keeps the engine clean by carrying contaminants in suspension within the lubricant to the oil filter, where they are removed.

What role does the lubricant play in preventing corrosion in the engine?

The lubricant minimizes corrosion inside the engine by providing a liberal coating on steel components, which would otherwise oxidize.

How does the lubricant assist in cooling the engine's bearing surfaces?

The lubricant takes heat away from the bearing surfaces and transfers it to the oil cooler, where it is dissipated into the atmosphere.

What additional function does the lubricating oil serve in some turboprop engines?

In some turboprop engines, the lubricating oil acts as a hydraulic fluid, controlling the pitch of the propeller blades.

What are the two basic recirculating systems in a gas turbine engine?

The two basic recirculating systems in a gas turbine engine are the pressure relief valve system and the full flow system.

How does the pressure relief valve system control the oil flow to the bearing chambers?

The pressure relief valve system controls the oil flow to the bearing chambers by diverting any excess volume back to the inlet of the pump, thus maintaining a constant pressure over the whole engine speed and oil temperature ranges.

What is the purpose of the torque meter pump in the lubrication system?

The torque meter pump is used to boost engine oil pressure to a figure higher than normal system pressure, primarily to balance the axial thrust of the helical gears within the propeller reduction gear.

How does the full flow lubrication system differ from the pressure relief valve system?

The full flow lubrication system allows the oil pressure pump to supply the oil feed jets directly without a pressure relief valve, which allows for the use of smaller pressure and scavenge pumps due to less oil volume being passed.

What is the function of the deaerator tray in the oil system?

The deaerator tray removes air bubbles from the oil as it flows back into the tank, ensuring the oil's effectiveness is not compromised by air entrainment.