Key Points of the lubrication system for aviation piston engines
The key points of the lubrication system for aviation piston engines mainly include the following aspects:
First, the function of the lubrication system
The main task of the lubrication system of an aviation piston engine is to continuously supply a sufficient amount of clean lubricating oil of appropriate viscosity to all the friction surfaces of the engine, ensuring that the components are well lubricated and cooled. This reduces the frictional power loss of the engine, lessors the wear of the components, and prevents overheating of the components, thereby enhancing the engine's power. Extend the service life of the engine and ensure its normal operation. In addition, lubricating oil can prevent rusting of engine parts, enhance the airtightness between the expansion ring and the inner wall of the cylinder, and improve the working efficiency of the engine.
Second, the composition of the lubrication system
The lubrication system of an aviation piston engine is typically composed of a lubricating oil tank (or oil collection pool), oil supply pump, lubricating oil filter, lubricating oil radiator, return oil pump, foam eliminator, magnetic plug and indicating instruments, etc.
Third, the working principle of the lubrication system
Lubricating oil circulation
When the engine is running, the lubricating oil in the oil tank is drawn by the oil supply pump, pressurized in the oil pump and filtered through the oil filter before being sent to the engine.
Lubricating oil enters the sliding bearings of the crankshaft, connecting rod, camshaft (or CAM disc), and gears through a dedicated oil circuit for lubrication.
The lubricating oil can also further enter the large end bearing of the connecting rod to lubricate the cylinder wall, piston and other parts.
After lubrication, the lubricating oil, under the stirring effect of the machine parts, mixes with the gas inside the casing (such as air, lubricating oil vapor and exhaust gas, etc.) to produce a large amount of foam, which then flows back to the oil collection pool at the bottom of the casing.
The lubricating oil is drawn out by the return oil pump, passes through the foam eliminator to eliminate foam, and then is cooled by the lubricating oil radiator before flowing back to the lubricating oil tank, completing one cycle.
Lubricating oil pressure and temperature control
The lubricating oil pressure gauge sensor is located on the oil circuit after the oil supply pump outlet, and is used to measure the lubricating oil pressure after being pressurized by the oil pump.
The sensor of the lubricating oil temperature gauge is installed on the oil circuit before the oil supply pump inlet or on the return oil circuit to measure the inlet or return oil temperature of the lubricating oil.
The temperature of the lubricating oil can be controlled within an appropriate range by adjusting the opening degree of the air damper of the lubricating oil radiator and changing the circulation volume of the lubricating oil.
Fourth, lubrication method
Aviation piston engines generally adopt a combination of multiple lubrication methods for the lubrication and heat dissipation of components, mainly including:
Pressure lubrication
The lubricating oil, after being pressurized by the oil pump, flows along a dedicated oil circuit to each friction surface for lubrication.
It is suitable for friction surfaces with heavy loads, such as crankshaft journal and bearings, camshaft journal and bearings, etc.
Splash lubrication
Lubrication is achieved by splashing lubricating oil onto the friction surfaces through rotating parts with higher rotational speeds (such as crankshafts, etc.).
It is mainly used for the working surfaces of parts such as the cylinder wall with relatively light loads and the CAM, tappet, valve stem and rocker arm of the valve train.
Jet lubrication
The lubricating oil, after being pressurized by the oil pump, is sprayed in a certain direction from special oil holes onto the friction surfaces of the machine parts for lubrication.
For instance, in some engines, the lubrication between the cylinder and the piston is achieved through injection lubrication.
Fifth, daily maintenance and troubleshooting
Keep the lubricating oil clean
Add lubricating oil as per the standard to prevent debris from entering the system.
Regularly check the amount and quality of the lubricating oil, and replace the lubricating oil and filter element in a timely manner.
Pay attention to the change in the amount of lubricating oil
After the flight, carefully check the lubricating oil level and add it in time.
If a significant increase in the consumption of lubricating oil is found, the cause should be analyzed in a timely manner and eliminated.
Keep the engine's vent hole unobstructed
Prevent excessive pressure inside the casing, which may cause oil leakage at the casing joints and seals.
Correct use of the engine
The operation should be gentle. After starting the cold engine, warm up the machine, and before stopping, cool it down.
Regularly disassemble and inspect the lubricating oil filter screen and the main oil filter
Analyze the working condition of the engine and promptly identify and handle potential problems.
Thoroughly clean the components of the lubricating oil system
When a wear fault occurs in the components of the lubricating oil system, a thorough cleaning of the engine lubricating oil system components, the lubricating oil radiator and hoses, etc. should be carried out to prevent metal shavings or impurities from depositating in the system pipelines.
Sixth, Summary
The key points of the lubrication system for aviation piston engines involve multiple aspects, including the function, composition, working principle, lubrication methods, as well as daily maintenance and troubleshooting of the lubrication system. Only by fully understanding and mastering these key points can the normal operation of the lubrication system of the aviation piston engine be ensured, and the safe and reliable operation of the engine be guaranteed.
