Different type of lubrication systems are used in engine and specific application of each type of lubrication are addressed in this article.

Before jumping straight into the different type of lubrication systems its important to learn the basics of lubrication, properties of lubricants.

what is lubrication.

Lubrication is a method in which we introduce a lubricating medium (solid, semi viscous, liquid) between the moving parts typically to reduce friction and ultimately to reduce the wear and tear. The primary purpose of lubrication is to create a thin layer of film to prevent direct contact of moving parts resulting in preventing metal to metal contact.By reducing friction lubrication helps in reducing heat generation and damage to surface in contact, to debrief these are the function of lubrication in any engine

  • lubrication reduce friction.
  • prevent wear of running machinery.
  • protects equipments from corrosion and degradation.
  • control temperature and dissipates heat.
  • control contamination and helps contaminants to be suspended for easy separation.
  • helps in transmitting power.
  • provides a sealing medium where necessary.
  • helps in cold start or initial running of machinery by preventing direct metal to metal contact.

All of these are achieved by lubricating medium which we call as lubricant.

Type of lubricants.

lubricants can be categorised on – physical state and manufacturing style

  • Physical state – solid, semi viscous, liquids

Solid lubricants are those which are in solid physical state these are used in areas where there is little movement with heavy loads and high temperature.Some of the examples of solid lubricants are graphite, molybdenum disulphide, PTFE (polytetrafluoroethylene) also called as teflon. This type of lubrication is used where liquid lubrication may not be practical and in combination with liquid lubrication.

Semi viscous lubricants refer to mostly grease and gel like lubricants which are commonly used in pressure transmitting areas and extended lubrication interval areas.Some of the examples are aluminium, calcium, lithium based grease. This type of lubrication is used where there is requirement for little movement of the lubricant.

Liquid type lubricants are viscous fluid namely oil type lubricant. These oil are categorised based on type of manufacturing and properties and are widely used in machinery lubrication of all types. Its important to know in detail about them type of oil lubricants.

Type of oil based lubricants

Oil based lubricants can be categorised as mineral and synthetic oils

Mineral oil lubricants are those which are derived from petroleum or crude through refining process or distillation and these lubricants are generally used for normal lubrication purpose in machinery and automobiles. Mineral based lubricants are cheap and widely available still they have some limitations like limited performance under extreme pressure, lower oxidation and thermal stability, viscosity variation with temperature.

Synthetic lubricants on other hand are formulated chemically engineered base oils which are manufactured peculiarly for particular purpose. The chemical formula varies are per the requirement of the application. These type of lubricants are mainly used in hydraulic systems, high voltage electrical systems, extreme pressure and temperature regions more in aerospace and racing industries.

Having discussed about the basics of lubrication and type of lubricants its now time to for knowing the type of lubrication systems in engines.

Various type of lubrication systems

Engines are basically divided into two types 4 stroke and 2 stroke and the type of lubrication systems also varies with the design and specific application of the engines.Basically splash type and pressure type lubrication are majorly employed in there are sub types in each of them which we are going to see in detail below.

  • SPLASH type of lubrication system are where the oil is being splashed over various engine parts by the crank web like the engine liner and piston for lubrication, cooling purpose. As the crank shaft rotates the the webs which are immersed in the lubricating oil present in the engine sump being scooped up onto the liner and piston for every particular unit for lubrication. This type of lubrication system is basically employed in 4 stroke and small engines where the engine height is limited.
  • PRESSURE type lubrication system are in which the lubricant is being pumped into the engine bores and lubrication pipes through a lube oil circulating pump. This system employees dry sump and oil being circulated through the engine’s dedicated passages and bores from dedicated sump and oil the lubrication is done the oil drains back again to the sump. the oil is mainly directed to main bearing, cam shaft and its bearing, piston and crosshead.This type of lubrication is used in the 2 stroke and large engines.
  • MIST OR CYLINDER lubrication is where large engines use a dedicated oil pressurising system for lubricating the liner as the piston moves up and down. this system employees a high pressure pump with quills (holes in liner) to inject cylinder lubricating oil as the piston moves up and down.

The above mentioned are various types of lubrication systems basically present in any engine and these system employee various lubricating techniques which we are going to see in detail below.

lubrication techniques in engines.

there are some lubrication techniques being employed in the engines to ensure for proper lubrication to be carried out in engines these play a crucial role in the design aspect of any engine and lets explore them one by one

  • HYDRO STATIC lubrication- this type of lubrication systems where there is no relative motion between the two components which are to be lubricated so the system uses a high pressure pump to supply oil between the engine components. the lubricant is being stationary hence the technique is called the hydro static. we can see this type of lubrication between the journal bearing and shaft in large engines when its stopped. The effectiveness of this type of lubrication depends mainly on the pressure generated by the pumps and clearance in passages where the lubricant is being pumped for lubrication.
  • HYDRO DYNAMIC lubrication- This type of lubrication systems there is a relative motion between engine components example between the journal and the bearing when the engine is running. the pressure of the oil is being self generated by the motion of the journal being rotated and the pressure is relative to the speed of rotation hence the name is given hydrodynamic.The rotating journal makes a wedge shaped lube oil boundary between the journal and bearing which prevents direct contact.
  • BOUNDARY LUBRICATION- This type of technique is being employed where the relative motion between the components is so fast and complete separation is impossible so we try to form a thin layer of lubricant by injecting lubricant under pressure between these running components to at least reduce the friction and reduce wear and tear. This type of lubrication systems is used in piston and cylinder lubrication.
  • ELASTO HYDRODYNAMIC LUBRICATION- Elastohydrodynamic lubrication (EHL) is a lubrication regime that occurs when there is significant elastic deformation of the contacting surfaces in addition to the presence of a lubricant film. It is a specialized form of hydrodynamic lubrication that is particularly relevant in applications involving high loads, high speeds, and conformal contact between surfaces. the lubricant film is extremely thin, typically on the order of a few micrometers or less. Under the high pressures generated by the load, the surfaces deform elastically, causing the contact area to increase. This increased contact area results in a higher load-carrying capacity and better separation of the surfaces. The elastic deformation of the surfaces also affects the lubricant film thickness and pressure distribution.The formation of the lubricant film in EHL is influenced by factors such as surface roughness, material properties, lubricant viscosity, and operating conditions. The lubricant itself may undergo changes in viscosity and shear thinning under high pressures and temperatures. These complex interactions between the surfaces, lubricant, and elastic deformation give rise to the unique characteristics of elastohydrodynamic lubrication.

To summarise these are basic of type of lubrication systems and techniques we employee in any 4 or 2 stroke engines further detail can be found the links below

2 thought on “Type of Lubrication systems in 4 & 2 stroke engines”
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