Internal Combustion Engines

Presented by – Manmeet Singh Assistant Professor

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Purpose of Lubrication

Reduce the frictional resistanceProtect the engine against wear.

Serve as a cooling agent by picking up heat.

Remove all impuritiesfromthe lubricated region.

Form a seal between piston rings and the cylinder walls to prevent blowby.

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Lubrication Systems

❖ Mist lubrication system❖ Wet sump lubrication system

❖ Dry sump lubrication system

Four Stroke Engines

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Two Stroke Engines

The wet sump system is employed in relatively small engines, such as automobile engines,

While the dry sump system is used in large stationary, marine and aircraft engines.

Mist Lubrication SystemsIn two-stroke engines, the charge is compressed in the crankcase, and as such it is not suitable to have the lubricating oil in the sump.

Therefore, such engines are lubricated by adding 3 % to 6 % oil in the fuel tank itself.

The oil and fuel mixture is inducted through the carburetor.

The fuel gets vaporized and the oil, in the form of mist, goes into the cylinder through the crankcase. The main advantage with this system lies in the simplicity and low cost as the system does not require any oil pump, filter etc.

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WET SUMP LUBRICATION SYSTEMS

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In the wet sump system, the bottom of the crankcase contains an oil sump (or pan) that serves as the oil supply reservoir. Oil dripping from the cylinders and bearings flows by gravity back into the wet sump where it is picked up by a pump and re-circulated through the engine lubricating system.The types of wet sump systems used are:

1. the splash and circulating pump system2. the splash and pressure system3. the full force-feed system

SPLASH AND CIRCULATING PUMP SYSTEMD:\IDM VIDEO\DOWNLOADED\MPEONLINE - 18-SPLASH LUBRICATION.SWF.MP4

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C a m s h a f t

C o n n e c t in g r o d b e a r i n g s

M a in be a r in g

m a inb e a r in g

O ilt r o u g h s

L o w e r o il p a n

O il p u m p

O il S t r a i ne r

SPLASH AND PRESSURE SYSTEM

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C a m s h a f t

C o n n e c t in g r o d be a r i ng s M a in be a r in g

m a inbe a r in g

O il p u m p

O il S t r a i ne r

FULL FORCE FEED SYSTEMD:\IDM VIDEO\DOWNLOADED\AUTOMOTIVE BASICS - HOW ENGINE LUBRICATION SYSTEM WORKS.MP4Cam

shaft

Oil pum p

Oil Strainer

Header mainline bearing

End leakagefrom rod

connecting rod bearingMain bearing

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DRY SUMP LUBRICATING SYSTEM

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OilCooler

P ressure releasevalve

V ent

Filter B y-P ass P resuurerelief valve

Filter

S cavenging pum p

S trainer

E ngine crankcase

Oil pum p

To B earings

S upply Tank

D ry sum p

Properties of Lubricating Oil

❖The oil used in an engine must serve as a lubricant, a coolant and an agent for removing impurities.

❖It must be able to withstand high temperatures without breaking down. The oil must operate over a good range of temperature.

❖They must not oxidize on the chamber walls, piston crown or at the piston rings.

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Oilshould

have

highfilm

strength

toprevent metal-to-metal

contact

evenunder extreme

loads.

PROPERTIES OF LUBRICATING OIL

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(a)Viscosity: The lubricating oil should have the correct viscosity so that it flows easily to all the moving parts.❖If oil viscosity is too high, more work is required to pump it and to shear it between the moving parts. This results in greater friction work, reduced brake work and hence reduced power output.

❖Viscosity is highlyontemperature, withdecreasing

dependent increasing temperature.❖The fuel consumptionmay increase by as much

as 15 %.

Selecting right viscosity- Rating of Lubricating Oil

engines use high viscosity grades oil.

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❖ Lubricating

oilis

generally

rated

usingaviscosity scale established by

theSAE.Commonly used viscosity

grades are: SAE 5SAE 10SAE 20SAE 30SAE 40SAE 45SAE 50

❖The oil with lower viscosity grades is less viscous and is used in cold-weather operation. Modern high temperature, high speed, close tolerance

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RATING OF LUBRICATING OIL – VISCOSITY INDEX

❖When certain polymers are added to oil, the temperature dependency of oil viscosity is reduced. These oils have low viscosity grades when they are cold and higher as they become hot.❖As for example, SAE 10W-30 means that the oil has a grade 10 when it is cold (W stands for winter) and 30 when it is hot. ❖Commonly used oils in this category are:

SAE 5W-20

SAE 10W-40

SAE 5W-30

SAE 10W-50

SAE 5W-40

SAE 15W-40

SAE 5W-50

SAE 15W-50

SAE 10W-30

SAE 20W-50

Rating of Lubricating Oil

(b)Specific Gravity: This property is of little importance except as an indicator of weight and volume. The specific gravity of oil varies from 0.85 to 0.96.

(c)Pour Point: It indicates the temperature below which the lubricating oil loses its fluidity and will not flow or circulate in the system. This characteristics of the oil is important at low temperature.

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Rating of Lubricating Oil(d) Oxidation Stability: Oxidation stability of an oil is its resistance to oxidation. Due to oxidation, oil forms deposits on the piston rings, and thereby loses its lubricating property. Some inhibitors are used to counteract these tendencies.(e) Acidity andNeutralizationlubricating oil should

have low

Number:The

acidity. The

neutralization number is a measure of acidic or alkaline contents of oil.(TAN Number)(f) Oiliness: Oiliness is responsible for the boundary layer of molecules that can adhere or cling to a metal surface and provide lubrication after most of the oil gets displaced or squeezed out.

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CLASSIFICATION OF LUBRICANTS

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• Animal• Vegetabl

e• Mineral• Syntheti

c

Types of Lubricating Oil

Q Vegetable oils have been used in the past, especially for racing car engines. The main advantages of these oils are their high film strength, and they have a good lubricity.

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Q Later, speciallyformulatedhave replaced theiruse

mineral in

oils high

performance engines. Mineral oils are most readily available and cost effective. They readily respond to additives, and can be produced in a wide range of viscosities. The main disadvantage lies with its wax content that affects cold performance and can clog filters.

ANIMAL LUBRICANTS

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• Lubricants with animal origin:– Tallow– Tallow oil– Lard oil– Neat’s foot oil– Porpoise oil

• These are highly stableat

normaltemperatures

• Animallubricants

may notbe

usedforinternal

combustionbecause

theyproduce fatty

acids.

VEGETABLE LUBRICANTS

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ofmineral

• There are threeclassifications lubricants:– Solid, Semisolid, Fluid

• Examples of vegetable lubricants are:– Castor oil, Olive oil, Cottonseed oil

• Animal and vegetable oils have a lower coefficient of friction than most mineral oils but they rapidly wear away steel.

Mineral Lubricants• These lubricants are used to a large

extent in the lubrication of aircraft internal combustion engines.

SYNTHETIC LUBRICANTS

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• Because of thehigh

operatingtemperatures of gas-turbine

engines,itbecame

necessaryto

developlubricants

whichwould retaintheircharacteristics at temperatures

that cause petroleum lubricants to evaporate and break down.

• Synthetic lubricantsdo

notbreakdown easily and do

notproducecoke or other

deposits.

Additives

❖ Corrosion and Rust Inhibitors

❖ Anti-foam Agents

❖ Detergent-Dispersants

❖ Pour Point Improvers

❖ Oiliness and Film-strength Agents 21

Conclusions

In order to minimize friction between the moving parts and hence wear, lubrication system in an engine plays a significant role. The lubrication system is designed to deliver clean oil at the correct temperature and pressure to every part of

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theengine.

Lubricating

oil canbesupplied to the various engine

components by a splash system or by a pressurized system or a by a combination of both. In two-stroke engines, oil is mixed with the fuel itself.