Lubrication & Lubrication Systems

Lubrication:

It is defined as the admittance of oil between two surfaces having relative motion.

Why do we need Lubrication?

The functions of lubrication are described ahead:

• Reduce friction between moving parts.
• Reduce wear and tear of parts.
• Shock absorbing.
• To cool the surfaces in contact.

Properties of Lubricants:

Following are the properties of Lubricants:

• Viscosity  ➸  Internal resistance to flow of liquid. It is the ability of oil to resists internal deformation due to load and mechanical stresses.
• Viscosity Index  ➸  It represents the change in viscosity of oil with temperature. The greater the viscosity index, the smaller the change in viscosity with temperature.
• Flash Point Temperature  ➸  The lowest temperature at which vapor of lubricating oil will ignite when given an ignition source.
• Fire Point Temperature  ➸   It is the minimum temperature at which vapor of fluid will keep burning after the ignition source is removed.
• Cloud Point Temperature  ➸  The minimum temperature at which lubrication oil is converted from liquid state into solid state.
• Pour Point Temperature  ➸  The minimum temperature at which lubrication oil starts to flow.
• Oiliness or Film Strength  ➸  A property which enables oil to spread over and adhere to the surface of bearing.
• Anti-Corrosive  ➸  Lubricant must not corrode materials.
• Emulsification  ➸  The property of losing oiliness of lubrication oil when added with water.
• Specific Gravity  ➸  It is the measure of density of oil.

Lubricating Oil Additives:

• Detergents  ➸  By adding detergents, gum deposit due to high temperature is reduced and act as effective acid neutralizer.
• Dispersants  ➸   By adding dispersants, varnish and cold sludge deposit due to low temperature is reduced.
• Anti-Wear Additives  ➸  It reduces the wear and tear of components by strengthening oil film.
• Rust Inhibitors  ➸  Rusting can be reduced by adding rust inhibitor which act as acid neutralizer by forming protective layer.
• Viscosity Index Improver  ➸  It prevents the thinning of oil film due to the increase in temperature.
• Anti-Foam Agents  ➸  It prevents foaming of oil due to air entrapment in bubble.
• Anti-Oxidants  ➸  Reduce oxidation of oil to protect corrosion of alloy bearing.

Lubrication Systems:

First we talk about what components require lubrication? So answer is:

1. Main Crankshaft Bearings
2. Big End Bearings
3. Small End Bearings
4. Piston Rings & Cylinder Walls 
5. Timing Gears
6. Camshaft & Camshaft Bearings
7. Valve Mechanisms
8. Valve Guides and Tappets 
9. Rocker Arms

How oil circulates around different components:

Types Of Lubrication Systems:

Components of Lubrication System is described in a video given below:

There are three types of lubrication systems used which are as follows:

1. Wet Sump Lubrication System:

In the wet sump lubrication system, the bottom of the crankcase contains an oil pan or sump from which the lubricating oil is pumped to various engine components by pump.

Wet sump lubrication system is further divided into 3 types in which this topic is briefly described.

A. Splash Lubrication System:

• Used in light duty engines.
• The oil pump is used to get oil to those parts where lubrication is required.
• Splasher is used to get oil to big end bearing for lubrication by hole drawn into the connecting rod.
• The base components of Wet Sump lubrication System are pump, strainer, pressure regulator, filter and breather. 

B. Splash & Pressure Lubrication System:

• A pressure pump is used to compressed the oil and used to get oil to main and camshaft bearing.
• Splasher is used to get oil to big end bearing for lubrication by hole drawn into the connecting rod.
• The base components of Wet Sump lubrication System are pump, strainer, pressure regulator, filter and breather. 

C. Pressure Lubrication System:

• In this system, oil is transported from sump under pressure to the required areas through distributed channels.
• A hole is drilled in connecting rod from which oil is passed through main bearing to the crank-pin bearing.
• The base components of Wet Sump lubrication System are pump, strainer, pressure regulator, filter and breather. 

2. Dry Sump Lubrication System:

• In this system, oil is carried in a separate tank from which is transported to the required pump by means of oil pump.
• There is no splasher or dipper connected to the crankshaft.
• Scavenge pump is used to get the oil from required lubricating areas to the tank by passing through a filter.

3. Mist Lubrication System:

• Mostly used in 2-stroke engines where crankcase lubrication is not suitable.
• In these engines, lube oil is mixed with fuel in a ratio of 3-6% and is inducted into the cylinder by carburetor.
• The oil which strikes the crankcase walls lubricates the main and connecting rod bearings.

References:

• University notes + my knowledge.
• Videos from YouTube.
• Images from Google Images.
• Book: IC Engines by V Ganesan (4th Edition).
• Class Lectures.