COOLING AND LUBRICATION OF ENGINES

Presented by:MD. AZHAR SHERIFFDEPARTMENT:-MECHANICAL ENGINEERING

INTRODUCTION COOLING OF ENGINE

The purpose of the Engine Cooling System is to prevent the overheating of vehicle’s engine. With engine combustion reaching extremely high temperatures, the resulting heat needs to be dissipated.

LUBRICATION OF ENGINE Lubrication is the process or technique employed to reduce friction between, and wear of one or both, surfaces in proximity and moving relative to each other, by interposing a substance called a lubrication.

PRINCIPLEPrinciple Cooling of Engine

Most Internal Combustion (I.C) engines are fluid cooled using either air cooled or a liquid cooled run through a heat exchanger (radiator) cooled by air. In Marine engines and some stationary engines have ready access to a large volume of water at a suitable temperature.

Principle Lubrication of Engine

• Primary purpose is to reduce friction between moving parts.

• No metal to metal contact occurs – cushioning (soften the effect of an impact on).

• Friction & Abrasive wear held to a minimum.• To absorbs shocks.• To form a good seal between piston rings and cylinder

walls.• To acts as cooling medium.• Clean the engine parts.

CONSTRUCTION Construction of Cooling Engine (Air cooled Engine)

Fig:- Air cooled Engine

Cooling Fins

Construction of Cooling Engine (liquid cooled Engine)

Lubrication of Engine

WORKINGAir Cooled Engine:-

In air cooled system a current of air made to flow past the outside of the cylinder barrel ,outer surface area which has been considerably increased by providing cooling fins.

The amount of heat dissipated to air depends upon : (a) Amount of air flowing through the fins. (b) Fin surface area. (c) Thermal conductivity of metal used for fins.

Liquid Cooled System• A liquid is circulated

around the cylinders and absorb heat from the cylinder walls and cylinder head.

• Coolant absorbs heat as it passes through the engine and also lubricates the water pump.

• Hot coolant enters the radiator in which the heat is passed on to air that is flowing through the radiator.

Working of lubricantLubrication is an art of admitting a lubricant (oil, grease, etc.) between two surfaces that are in contact and in relative motion. The purpose of lubrication in engine is to perform one or several of the following function:-•To reduce friction and wear between the moving parts and thereby the energy loss and to increase the life of engine.•To provide selling action e.g. the lubrication oil helps the piston rings to maintain an effective seal against the high pressure gasses in the cylinder from leaking out into the crankcase.•To cool the surface by carrying away the heat generated in engine components.•To clean the surface by washing away carbon and the metal particles caused by wear.

Lubrication of Engine Components In the reciprocating engine there are many surfaces in the

contact with each other and therefore they should be lubricated to reduce friction. The principal friction surfaces requiring lubrication in an internal combustion engine are :-

• Piston and cylinder • Crankshaft and their bearings• Crank pin and their bearing• Valve gear

Types of Lubrication system The function of lubrication system is to provide sufficient quantity of cool, filtered oil to give positive and adequate lubrication to all the moving parts of an engine. The various systems used for internal combustion engine may be classified as:-

(i) Wet lubrication system

(ii) Dry lubrication system

(i) Wet 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 a pump. After lubrication these parts, the oil flow back to the sump by gravity. Again it is picked by a pump and re-circulated through the engine lubricating system. The main types of wet sump lubrication system are

• splash lubrication system.• Pressure lubrication system.• semi pressure lubrication system.

(i) Dry Lubrication System

In this system, the supply of oil is carried in an external tank. An oil pump draws oil from the supply tank and circulates it under pressure to the various bearing of the engine. Oil dripping from the cylinder and bearing into the sump is removed by the scavenging pump which in turn the oil is pass through a filter, and is fed back to the supply tank. Thus oil is prevented from accumulating in the base of engine. The capacity of the scavenging pump is always greater than the oil pump. In this system a filter with a bypass valve is placed in between the scavenging pump and the supply tank. If a filter is clogged, the pressure relief valve opens permitting oil to bypass the filter and reaches the supply tank. A separate oil cooler with either water or air as the cooling medium, is usually provided in the dry sump system to remove the heat from the oil.

Fig:-Dry lubrication system

Properties of lubricants The duties of the lubricant in an engine are many and

varied in a scope. The lubricant is called upon to limit and control the following:

• Friction between the component and metal to metal contact

• Overheating of the component• Wear of component• Corrosion • Deposit

APPLICATIONS• Lubricants are used for Automotive Engine oils,

tractors, marine and agricultural etc.,• All types of bearings use the lubricants to reduced

the friction.• Most useful lubricants includes hydraulic oil, air

compressor oils, gear oils, bearing and circulating system oils, steam and turbine oils etc.,

ADVANTAGESAdvantages of Cooling:-• The advantages of using liquid cooling over air cooling

include water's higher specific heat capacity, density, and thermal conductivity.

• A liquid cooled engine produces more power/torque than an air-cooled one.

• A liquid cooled engine, since cooled by liquids, maintains a better control temperature.

• Air-cooled engines are nosier and somewhat harsh than liquid cooled engines.

Advantages of Lubrication:-• Higher oil film strength with some synthetics.• Higher viscosity index.• improved engine reliability due to consistent oil

pressure.• Having the pumps external to the engine makes them

easier to maintain or replace.

DISADVANTAGESDisadvantages of Cooling:-• At low engine temperature the starting of the engine

becomes difficult.• The liquid cooling system is costlier as it has more

number of parts.• Air cooled engines comparatively it is less efficient.• Air cooled system is generally used in small engines.• Cooling fins under certain conditions may vibrate and

amplify the noise level.

Disadvantages of Lubrication:-• Cause heavy exhaust smoke due to burning of

lubricating oil.• Forms deposit on piston crown and exhaust port which

affect engine efficiency.• Requires a thorough mixing for effective lubrication.

This requires either separate mixing prior to use of some additive to give the oil mixing characteristic.

CONCLUSION Cooling:- A cooling system must be provide not only to prevent

damage to the vital parts of the engine(due o high temperature), but the temperature of these components must be maintained within the certain limits in order to obtain maximum performance from the engine.

Lubrication:-In order to minimize friction between the moving parts and hence wear, lubrication system in an engine. Is designed to deliver clean oil at the correct temperature and pressure to every part of the engine.

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