Presentation onBasics of Diesel Engines

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INDEXA] Heat Engine

Stroke CyclesDefinitions

B] Diesel Engine Systems1. Air System 2. Lubricating System3. Cooling Systems 4. Fuel System 5. Governing System6. Valve Mechanism7. Exhaust system8. Starting system

C] Basic Components of Diesel Engine

Basics of Diesel Engines

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Basics of Diesel Engines

What is an engine?An engine is a device for converting stored

energy into useful work. Engines are chiefly used to turn the wheel and

shafts of machines (e.g.machinery in factories, cars and other

vehicles, locomotive).

- Heat Engine

Heat engine

Most engines today use fossil fuels as an energy source.

These engines are known as heat engines because when fossil fuels are burned, i.e. heat energy in the form of hot expanding gases are produced.

O xygen

Fuel

Ign iter

C O M B U S T IO N P O W E R/ W O R K

Fuel

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How do heat engines work?The essential part of a heat engine is a cylinder in which a piston moves up and down. (This is known as a reciprocating movement.)

In a heat engine, fuel is burned in the cylinder thus producing got expanding gases. The rapid expansion of hot gases creates pressure in the cylinder which pushes the piston downwards. Since most machinery works with a rotary (circular) movement, the up and down (reciprocating) stroke of the piston is converted into a circular movement with the help of a crankshaft.

C irc ular M o tio

n

Heat Engine

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Heat Engine

Heat engines can be classified according to :

a) The type of fuel they use ( e.g. Petrol Engines, Diesel Engines, Heavy Fuel Engines, Steam Engines.

b) Whether the fuel is burned outside or inside the engine.

In External Combustion engines (e.g. steam locomotives), the fuel is burned separately in the furnace of a boiler which produces the steam.

The steam then enters the cylinder and moves the piston.

In Internal combustion engines (e.g. petrol and diesel engines) the hot expanding gases are produced by burning the fuel inside the cylinder of the engine so that less energy is lost. These engines are generally smaller and more efficient than steam engines.

E xte rnal C o m b us tio n

In te rnal C o m b us tio n

Classification of Heat Engines

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Heat Engine - Diesel Engines

Diesel engines, like petrol engines are internal combustion engines. The first diesel engine was 'also designed by a German engineer, called Rudolph Diesel, in 1892. Diesel used the same 'Four stroke Otto cycle' as in petrol engines. But instead of using an electric spark to ignite the fuel as in petrol engines, he made use of the high compression ratio of gases in his design to heat the air.

Diesel realised that the more air is compressed the hotter it becomes, and if it is compressed very rapidly, it will ignite spontaneously without needing an electric spark to set it off.

In a diesel engine, air in the cylinder is compressed to a very high degree, thus raising its temperature. The oil is then injected as a fine atomised spray into the hot air of the cylinder where it ignites with out the need of a spark. Diesel's first engine, exploded and nearly killed him, but by 1897 he had made a successful producing 25 h.p.

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Diesel and Petrol Engines - a comparison

a) A diesel engine is heavier than a petrol engine

because it has to withstand higher pressures.

b) A diesel engine has no carburetor.

c) A diesel runs on heavier (and cheaper) oil

which

the petrol engine cannot use.

d) The efficiency of a diesel engine is about 35%

compared to about 25% for the petrol engine.

(The efficiency of an engine is the energy

output divided by the energy input, multiplied

by 100 to make a percentage.)

Heat Engine - Diesel Engines

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Basics of Diesel Engines

- Four Stroke Cycle

Most diesel engines are based on original design.

In these engines, four strokes of the piston are

required for one complete cycle, during which the

crankshaft rotates twice.

Power is only produced during one of these strokes.

1. S tro ke 2. S tro ke 3. S tro ke 4. S tro ke

Intake C ompress ion Power E xhaust

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Suction stroke

1. Intake valve remains open during

the entire intake stroke.

2. Piston travels from TDC to BDC.

3. Due to partial vaccum created by the piston

travel, air rushes in.

4. Exhaust valve remains closed during this period.

E xhaustVa lve

InletVa lve

Basics of Diesel Engines

- Four Stroke Cycle

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Compression stroke

1. Both inlet and exhaust valves remain closed.

2. Piston travels from BDC to TDC.

3. The entrapped air is compressed causing air

temperature to rise to about 560 ºC.

4. Fuel is injected in atomized condition into

the hot air where it ignites.

5. Combustion of fuel generates heat and gases.

The rapid rise in temperature and pressure in

the combustion chamber pushes the piston to

BDC.

Exhaus tValve

In letValve

Basics of Diesel Engines

- Four Stroke Cycle

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Power stroke

1. Due to high temperature and pressure in the

combustion chamber, piston is pushed from

TDC to BDC. This is also called as "Useful

Work Done".

During this stroke both valves remain closed.

Exhaus tValve

In letValve

Basics of Diesel Engines

- Four Stroke Cycle

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Exhaust stroke

1. Intake valve remains closed.

2. Exhaust valve remains open during the entire

stroke.

3. Piston travels from BDC to TDC.

4. Exhaust gases are expelled out.

E xhaus tValve

In le tValve

Basics of Diesel Engines

- Four Stroke Cycle

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Valve Overlap PeriodDuring a brief period, when the exhaust stroke is coming to an end the intake stroke is commencing, both the intake the exhaust valves are open. This is essential in the four stroke cycle of the combustion engine.

E xha us tVa lve

In le tVa lve

a) It allows air to rush in from the intake port and forces any remaining burnt gases out of the exhaust port in a scavenging operation, so that the combustion chamber is clean and ready for a fresh charge of clean air.

b) It cools the exhaust valve cone and the piston crown which are subjected to high temperatures.

Basics of Diesel Engines

- Four Stroke Cycle

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Some smaller engines have a power stroke once in two strokes.

In these engines the crankshaft turns around once every cycle.

2nd S troke1s t S troke

Basics of Diesel Engines

- Two Stroke Cycle

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Basics of Diesel Engines

- Definitions

What is Horse Power?A Unit for measuring power. It is the rate at which work is done. One unit of horse power equals 75 kpm/s or 75 kg/m/sec (metric)What is BHP? BHP is the net power available at the crankshaft of the engine. This is total power less frictional and other losses.What is Bore & Stroke ?Bore : The Internal diameter of the cylinder liner.Stroke : The distance the piston travels up and down inside the cylinder from TDC to BDCTDC = Top Dead CentreBDC = Bottom Dead Centre

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What is compression Ratio ?

A ratio expressing the extent to which a charge of air is compressed.

It is a relation between the Swept Volume (Vs) and the Clearance Volume (Vc) and is determined at follows:

Basics of Diesel Engines

- Definitions

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Air system

Lub. oil system

Cooling system

Fuel system

Governing

system

Exhaust system

Valve

mechanism

Starting system

Respiratory System

Circulatory

System

Excretory System

Digestive

System

Mental System

Urinary System

Nervous System

Initiative

Basics of Diesel Engines

- Systems Comparison

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Basics of Diesel Engines

- Air Systems

For satisfactory combustion, an engine requires

approximately 3000 liters of fresh, clean oxygen to

burn one liter of fuel.

This can be ensured by :

The location of the power house.

Engine ventilation.

Air cleaner maintenance.

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Basics of Diesel Engines

- Air Systems

AIR SYSTEM COMPONENTS

1. Air Cleaner.

This filters the air before inducting it into the

engine.

There are two main types :

a. Oil bath type.

Known as the scrubber type of cleaner, this is

used for light and medium duty. Efficiency is

approximately 98.7% at recommenced air flow

and will reduce at a low air flow level.

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b. Dry type

Known as the baffle type of cleaner. This is

generally used for light to extra heavy duty

work. Efficiency is approx. 99.8% at all

operating conditions. Air Cleaner performance

comparison oil bath versus dry type

2. Air Inlet Manifold

This directs clean air to the cylinder for

combustion. The opening depends on engine

application and fitment on equipment i.e. G.E.

side, center or F.W.E.Opening

Basics of Diesel Engines

- Air Systems

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Maintenance Procedure forDry Type Air Cleaner

Service the dry type air cleaner only

when it is choked. Choking is indicated by

the air restrictor indicator OR by sluggish

engine performance. Check the restrictor

indicator daily. If the indicator band shows

‘RED', clean the filter elements as follows :

Basics of Diesel Engines

- Air Systems

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Maintenance Procedure for Dry Type Air Cleaner

1a. Remover the outer element only.

(Never clean the inner / safety element).

1b. The element should be cleaned with

compressed air from inside to outside, under

controlled air pressure as shown. The compressed

air pressure should not exceed 3 kg/cm2. Always

clean from inside to outside. The cleaning nozzle ID

should be more than 8 mm.

Basics of Diesel Engines

- Air Systems

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1c. Never clean from outside to inside.

1d. Clean it from inside to outside. The cleaning

nozzle should be held 25 to 30 mm away from the

inside surface of the element. Keep a distance

between the nozzle and the element.

Basics of Diesel Engines

- Air Systems

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Maintenance Procedure for Dry Type Air Cleaner

2a. Where two elements are provided in the filter,

only service the outer element.

2b. Never remove and clean the inner element i.e.

the safety element. The safety element should be

replaced every three replacements of the outer

elements. Never clean the safety element. Always

replace it at recommended intervals.

Basics of Diesel Engines

- Air Systems

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2c. After cleaning, check the element for any tear

or damage by passing as inspection lamp.

2d. Check for any holes using the electric bulb

test. In case you see a hole, replace the element.

Clean the filter housing with a water moistened

cloth.

Basics of Diesel Engines

- Air Systems

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Maintenance Procedure for Dry Type Air Cleaner

3a. Check the vaccuator valve for damage, replace

the same immediately.

3b. Before refitting the element and assembling

the filter; Check the sealing gasket of the element.

3c. Check for proper adhesion between end plate

of the element & the sealing ring. Ensure that the

rubber washer of the wingnut is good and is in

position. Remember dust is the greatest enemy of

your engine.

Basics of Diesel Engines

- Air Systems

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Maintenance Procedure for Dry Type Air Cleaner

3d. Reset the choke indicator, and start the engine. If the choke indicator band shows ‘RED' again, replace the outer element.

3e. Don't : Clean the filter element by thumping or banging. This will damage the element and cause dust to pass inside the engine. Wash the filter element with soap and water.

Check the sealing gasket of the filter housing and cover. N.B. : For extremely dusty site conditions, please contact nearest KOEL Service Dealers / KOEL Area Office for further guidelines if any.

Basics of Diesel Engines

- Air Systems

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Precautions : Frequent cleaning leads to drop in the dust holding

capacity, weakening of the air filter media and ruptures.

This, in turn, could result in serious damage to the engine

because of entry of dust in the system. Inner element should never be cleaned but always replaced. The useful life of inner element is equivalent to three changes

of the outer element or one year of continuous service,

whichever occurs first.

Basics of Diesel Engines

- Air Systems

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For satisfactory combustion, an engine requires approximately 3000 liters of fresh air to burn one liter of fuel.For satisfactory performance, the engine must have :

Fresh, Cool, Clean and sufficient Air :

This can be ensured by the :

1) Proper location.

2) Good ventilation.

3) Good Air cleaner maintenance.

Basics of Diesel Engines

- Air Systems

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An engine is said to be healthy if it has,

Good CompressionThe temperature of the induced air when entrapped andcompressed in the combustion chamber is about 540 0C to 560 0C.

Good CombustionFuel is sprayed in atomised condition to ensure proper ignition of fuel. Burning temperature is about 1425 0C.

Clean ExhaustThe exhaust system is clean and light brown in colour and the exhaust back pressure is within the permissible recommended limits.

Basics of Diesel Engines

- Air Systems

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1) Pre cleaner assembly

2) Dust collector

3) Oil bath

4) Primary element

5) Secondary element

6) Oil

Basics of Diesel Engines

- Oil Bath Air Filter

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The engine's lubricating system is designed to :

Reduce friction

Cool

Seal

Scavenge

Dampen shocks

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Basics of Diesel Engines - Lubricating System

Where the temperature variation between minimum and maximum is very wide, multigrade oils should be used. Also multi-grade oil is better than mono-grade oil.

Example : SAE 20W40 is a multi-grade oil and can be used where atmospheric temperature is between -5° C to 45° C and above. (Which is applicable to normal Indian climatic condition.)

KOEL recommends to use K-Oil which confirms to the following specifications :

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Basics of Diesel Engines - Lubricating System

a. Pressure LubricationUsually by an engine mounted lubricating oil pump pressure lubrication is achieved. The pump can be of the plunger type, gear type or "G" rotor type.

Used to lubricate the crankshaft, main bearings and journals, connecting rod large and small end bearings, camshaft journals, rocker assembly, turbocharger, etc.

a

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Basics of Diesel Engines -Lubricating Methods

b. Splash Lubrication

This is done by oil thrown by the high speed rotating components of the engine, such as the crankshaft. Used to lubricate crankshaft, liners, piston and gear train.

c. Mist LubricationLubrication by oil droplets which are formed oil fumes. Used to lubricate the valve rockers of small single cylinder engines.

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Basics of Diesel Engines -Lubricating Methods

Lube Oil Circuit HA1. Oil SumpThe oil sump is usually fitted on the lowest part of the engine. It is provided with a drain plug to enable oil draining. Oil sumps are of two types :Standard Sump - for stationary applications.Deep sump - for industrial automotive applications.

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Basics of Diesel Engines -Lubricating System Components

Lub. Oil Circuit R10401. Oil SumpThe oil sump is usually fitted on the lowest part of the engine. It is provided with a drain plug to enable oil draining. Oil sumps are of two types :Standard Sump - for stationary applications.Deep sump - for industrial automotive applications.

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Basics of Diesel Engines -Lubricating System Components

2. Dipstick

The dipstick measures the quantity of oil in the sump. It is usually grooved with low and high markings to help users maintain the correct oil level in the sump.

CAUTION :

Oil level to be checked when the engine is in cold condition.

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Basics of Diesel Engines -Lubricating System Components

3. Oil strainer and suction tube

This is fitted to the suction end of the oil in the pump. It is taken from the sump by the suction tube-cum-strainer. The strainer prevents large impurities entering the pump and damaging it.

4. Lubricating oil pump

It helps to circulates oil around the engine's components under pressure.

5. Oil Filter (Std).Filters micro particles to avoid damage to bearings, journals and other components. Oil filter element is to be replaced during every oil change.

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Basics of Diesel Engines -Lubricating System Components

While changing the filter element ensure the followings :

1. The big opening of the filter element is on the top.

2. Check for the spring & washer correctly placed in

their positions ( washer to be fitted on the top of the

spring ) Another is of cartridge type Lub. oil filter.

6. Pressure regulating Valve

Regulates lub. oil pressure within the system.

Usually preset, it cannot be adjusted.

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Basics of Diesel Engines -Lubricating System Components

Basics of Diesel Engines - Cooling System

Cooling is required :-to dissipate heat not utilized by the engine to develop power, and to prevent over heating.-for temperature regulation.

A diesel engine converts the chemicals energy stored in the fuel into mechanical energy. unfortunately, not all the ignited diesel is converted into mechanical energy. In fact only part of the stored energy is converted into useful energy. The rest produces waste heat. This heat must be removed to avoid damaging the cylinders & other engine parts by over heating.

Air Cooled Cooled by a forced draft of air and thus are known as directly cooled engines.

A liquid coolant is used as the medium of cooling. Liquid cooled engines are known as indirectly cooled engines.

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Types of liquid cooling.

a) Run through systemUsed on small pump sets, where cold water is continuously passed through the engine.

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Basics of Diesel Engines - Cooling System

b) Thermosyphon system

Used on engines without a radiator.

c) Closed loop systemPressurized system through a radiator/heat exchanger.

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Basics of Diesel Engines - Cooling System

a. Water cooled engines1. RadiatorThis unit comprises of a core of tubes and fins the core is sandwiched between the top and bottom header tank. Water passing through the tubes is cooled as the tubes come in contact with the cooler outside air which is forced over the tubes and fins by a radiator fan. KOEL recommends to use radiator coolant like K-Cool to give better performance & life for your engine.

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Basics of Diesel Engines - Cooling SystemComponents

2. Radiator cooling fan.Normally engines mounted & driven. Two types of fans are available.

The Puller or Sucker type sucks cold air from outside through the radiator and cools the hot water of the engine. This type of fan is used for automotive or traction purpose.

The Pusher type of fan pushes or forces the air from the engine room to the atmosphere through a radiator and cools the hot engine water. Used on stationary engines.

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Basics of Diesel Engines - Cooling SystemComponents

3. Water Pump

The water pump is normally engine mounted and engine driven through the fan belt. It delivers cool water from the radiator to the engine water jacket. the impeller is an open type with vanes, which when rotated, forces coolant to the engine's jacket by centrifugal action.

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Basics of Diesel Engines - Cooling SystemComponents

4. Thermostat : Why thermostat is required ?A thermostat is a device that maintains a steady temperature over a period of time. A thermostat is required to :Bring up the engine's operating temperatures fast. Maintain temperatures within the recommended limits even when the engine is operating on different loads and speeds Reduce the wear and tear of engine components.The thermostat is mounted on the water outlet side. When the coolant is cold, the path to the radiator is blocked by the thermostat valve and water is recycled back to the engine. When the water warm-sup to a predetermined temperature, the valve opens the passage to the radiator & at the same time closes the short circuits to the engine. Water is now routed through the radiator for cooling before it returns to the engine.

Closed Condition

Opened Condition

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Basics of Diesel Engines - Cooling SystemComponents

b. Air-cooled enginesAir is forced through the cylinder heads and liners by the blower. In air-cooled engines the heads and liners have cooling fins through which the area of contact is increased. Air comes in contact with the fins, absorbs a substantial amount of heat and takes it away from the engine.

1. BlowersRadial Fan - Used on single cylinder engines, and normally mounted on the engine's flywheel. Generally made from sheet metal/plastic.

Axial Fan - Used on multi-cylinder engines & normally driven by the engine fan belt arrangement. Generally these are die-cast.

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Basics of Diesel Engines - Cooling SystemComponents

2. CowlingA covering designed to :Direct equal volume and pressure of air to the important hot parts of the engines that require cooling.Ensure that all air supplied is used to us its maximum air loss.

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Basics of Diesel Engines - Cooling SystemComponents

Out of the 100% fuel supplied to the fuel system,

only 11 to 12 % is used for combustion. The balance

is returned to the fuel tank through the return line.

Fuel system components : Fuel Circuit

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Basics of Diesel Engines - Fuel SystemComponents

1. Fuel tank

To store an adequate quantity of fuel for at least 8 hours of operation.

2. Fuel filter

To filter micro particles present in the fuel and prevent damage to the injection pump and injectors.

3. Fuel feed pump

To draw fuel from the service tank and deliver it under pressure to the fuel injection pump.

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Basics of Diesel Engines - Fuel SystemComponents

6. Bleed valveTo maintain the prescribed fuel pressure in the fuel pump reservoir to facilitate the filling of the pump barrel within a stipulated time. excess fuel is returned to the service tank through the valve.7. Button filter / Swivel typeIt is provided in the inlet benjo of feed pump and should be cleaned regularly. Choke of button filter may lead to engine not taking load.

4. Fuel injection pumpTo pump a metered quantity of fuel from the fuel tank to the injector at the correct time.

5. Fuel InjectorTo inject fuel into the cylinder under high pressure in an atomised state for ignition. The proper combustion is not achieved because of incorrect pressure and incorrect spray pattern of fuel in combustion chamber.

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Basics of Diesel Engines - Fuel System

A governor is a device to automatically control engine speed.Governing is required to :- Maintain engine speed within the permissible speed limits.- Prevent over speeding of the engine when suddenly unloaded.- Prevent stalling of the engine at low idling speed.Class Of GoverningClass A - 1-D. G. sets used in computer and satellite centers ( isocronous to 2%)

Class A - 2- For std. D.G. set operation ( up to 4.5%).

Class B-For variable speed governing as in automotive applications ( from 6 to 8%)

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Basics of Diesel Engines - Governing System

Types Of Speed Governors

(a) Mechanical

Widely used for D.G. sets and

automotive applications.

(b) Pneumatic

For automotive and traction applications.

(c) Hydraulic

For close governing of D.g. sets up to zero

percent droop.

(d) Electronic

For zero percent droop and applications

requiring a quick response.

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Basics of Diesel Engines - Governing System

Types Of Governing :

a) HIT & MISS Type:

Earlier engines were governed by missing a

complete engine cycle.

b) QUANTITY Governing: Where Fuel & Air ratio is

constant & intake to the engine is regulated by a

carburetor butterfly /slide valve. Ex : Petrol Engine.

c) QUALITY Governing: Where air to engine remains

constant for a given speed & fuel to the engine is

regulated thus changing quality of charge

supplied to the combustion chamber of an engine.

Ex : Diesel Engine.

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Basics of Diesel Engines - Governing System

Basics of Diesel Engines - Exhaust System

The exhaust system :- removes hot gases into the atmosphere.- reduces the exhaust noise level

Components1. Exhaust Manifold :

This guides the exhaust gases smoothly from the engine to a common exhaust pipe without much back pressure.

2. Exhaust Silencer: Reduces the exhaust noise of the engine to an acceptable level, without causing unnecessary back pressure.

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Three types of silencers are available :1. Standard Acoustic Silencer :

for commercial use.2. Residential Silencer :

to further reduce the noise level.3. Spark Arrestor Type Silencer :

specially used where there is a possibility of an explosion of fire due to sparks from the exhaust.

3. Exhaust PipeDirects hot gases into the atmosphere

harmlessly.- Material of pipe- Total length of pipeline ( Including Silencer )Maximum number of 90 degrees bends.MS ERW ( Mild Steel Electric (Resistance Welding

)15 meters 4 nos.

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Basics of Diesel Engines - Exhaust System

Black Smoke This indicates improper combustion. This could be due to :- choked / wrong air cleaner.- defective fuel injection equipment.- choked exhaust system or wrong size exhaust pipe.

Exhaust Smoke The general condition of a diesel engine can be determined by the type of smoke it emits. ( This can be termed " The pulse of the engine" ). A healthy engine emits brown smoke. And if you look at the area surrounding the exhaust outlet, it will appear hazy, with barely visible smoke. However, if the engine emits black, blue, white or grey smoke, this is a signal that something is wrong.

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Basics of Diesel Engines - Exhaust System

Blue SmokeThis is emitted when oil begins to burn in the combustion chamber.Possible causes :- Excess oil in bath type air cleaner.- Excess oil in the sump.- Excess lub. oil pressure.- Worn piston rings or liners.- Worn valve steam or valve guides.

White SmokeIndicates the presence of water in the combustion chamber due to :- Cracked cylinder head- Cracked or damaged liner- Water in diesel- Burnt/damaged cylinder head gasket White smoke is dangerous specially when emitted by a water cooled engine, as it can lead to a hydraulic lock and extensive damage to the engine.

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Basics of Diesel Engines - Exhaust System

Grey SmokeThis smoke is a combination of the Blue and White smoke.This smoke indicates that the engines requires a major check up and possible overhauling.

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Basics of Diesel Engines - Exhaust System

The valve mechanism is the nerve centre of the engine. It ensures the precise operation of the valves in a controlled sequence to achieve maximum volumetric efficiency and scavenging of combustion gases, and injection of fuel at the precise time so that the engine can give optimum output.Components

Gear train

To rotate the camshaft at half the crankshaft speed

and to work the engine mounted pumps.

Camshaft

To determine the opening and closing of valves

precisely by converting a rotary motion into

a reciprocating motion.

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Basics of Diesel Engines - Valve Mechanism

TappetsFollow the camshaft lobes and transmit movements to the valve rocker. Accept the push rod ball end side.

Push rodsThe link between the tappets and valve rockers to transmit motion.

Valve rocker assemblyTransmits motion from camshaft to valves

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Basics of Diesel Engines - Valve Mechanism

An engine is required to be cranked to be started . Once it starts and develops its own power it operates on its own. Methods presently used for starting an engine are :1. Hand starting2. Electric starting3. Compressed air starting Hand Starting :This method is used on small engines where the efforts to rotate the engine is not very much.

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Basics of Diesel Engines - Starting System

Electric Starting :On multi-cylinder medium horse power engines the electric starting system is widely preferred. This is a DC system and works on a battery. The advantage of the system is its simplicity and effectiveness. The system comprises of the battery which stores the electric current & a starter which is a high torque unit to overcome the high compression of the engine.Compressed Air Starting :This type of starting is normally used on large slow and medium speed engines. The main advantage of this system is that the starting torque is very high as it has to take care of the large rotating and reciprocating mass of the big engines.

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Basics of Diesel Engines - Starting System

BASIC COMPONENTS OF DIESEL ENGINEPart : Crank case ( Heavy Duty Cast Iron )

C rankc as e

C am B us h

M ain B earing C ap T hrus t W as her

Function Rigid base & foundation for

the Engine. To store lub oil. To support crank-shaft &

other engine parts. Dipstick hole is also drilled in

the crankcase. It should be cooled &

lubricated & should transmit less noise outside.

Constructional Features Oil Passages are drilled inside the

Cr. case for lubrication of main brgs, camshaft journals, & inter mediate gear.

Cr. case is open from bottom side & is closed by oil sump.

Main brg bores are bored with the bearing caps in position to ensure longitudinal alignment.

Cam bore is also bored in Crank case for camshaft journal.

It is subjected to severe mechanical & thermal stresses.

Remarks

Cr. Cases for 2, 3, 4 & 6 Cylinder are identical in design except for the length.

During engine overhaul following points are to be considered.

Ensure correct undersize bearings are given.

Replace main brg cap bolts.

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BASIC COMPONENTS OF DIESEL ENGINEPart : Crank shaft ( Forge steel )

Function

Transforms reciprocating motion into circular motion.

It is called a crank shaft because it is made with cranks or throws (an offset Portions of the shaft) with a rod journal machined. This throw determines the stroke of the crank shaft.

A crankshaft is composed of the Crankpins, crankwebs, crank journals, & driving ends.

Constructional Features

A crank pin together with the two crank arms on opposite sides of it is frequently referred to as a " Crank throw “

In multi cylinder engines crankshaft rotates & centrifugal force acts on crankarms, crankpin & part of the rod which leads to unbalanced rotating force which would cause the engine to vibrate if no means are provided to balance it. Thus balance weight are normally provided to counter act these forces.

A crankshaft must resist bending moments & torque & any stresses due to vibration & offer adequate area for the bearing surfaces.

Remarks

Whenever crankshaft is removed for grinding pin or journal check for

Bal. wt to be numbered from either FWE or G.E Side.

Bal. wt bolt to be replaced.

After grinding ensure proper fillet radius. This is special alloy steel suitable for surface hardening process.

C rank P in C ranks haft

C rank J o urna lO il H o le

B alanc e W eig ht

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BASIC COMPONENTS OF DIESEL ENGINEPart : Cylinder Block ( cast iorn )

Function

Support for cylinder & other engine parts.

Passage for cooling medium.

Constructional Features

Cylinder is located in Cyl. block which provides water jacket area for liner.

For Water circulation from block to Cyl. head, one Ferrul is fitted with 'O' ring in Cyl. block.

Remarks

Whenever you are replacing either liner or block ensure that proper seat is taken between liner & block to prevent water leakage.

Also ensure if copper shim is also fitted with the cyl. block which will prevent water leakage between cyl. head & block.

C ylind er B lo ck S h im(B etw een C rankcas e & B lo ck)

C ylind er B lo ck

P late Typ e C o o ler

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BASIC COMPONENTS OF DIESEL ENGINEPart : Cylinder liner. ( Specially alloy cast iron or malleable C.I. )

C o p p er S tim

C ylind er L iner ‘O ' R ing

C ylind er L iner

Function

To form the combustion space & chamber where power is generated.

Cyl. liners are fitted in the cyl. block with rubber 'O' rings in between the block & liner for water Sealing.

To dissipate a part of the heat to the cooling system, either air or water.

Constructional Features

They Centrifugally cast. Precision bored & honed to have a glossy finish to minimise frictional losses & ensure proper sealing & compression.

Liners are basically or two types :

Wet Types :- When the outer surface is directly in contact with water. Rubber rings are provided to prevent water leakage.

Dry Type :- Outer surface not in contact with water.

Remarks

By using liners, it reduces the cost of repairs by replacing only liners. Normally on all KOEL engines we use wet type liners.

CAUTION :-

By using duplicate or spurious liners leads to problems like high lub. Oil consumption & fast liner wear.

Genuine liners are honed which ensured proper lubrication.

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BASIC COMPONENTS OF DIESEL ENGINEPart : Piston ( Aluminium Alloy )

P is to n A s s ly

In ternalC irc lip

P is to nP in

P is to n

P is to n R ing S et

Function

It supports for rings & gudgeon pin.

During normal engine operation the piston is subjected to temp. about 650 - 7000C.

Guiding & supporting the piston within the Cylinder liner is the piston skirt. (Bottom part of the piston below ring area. )

Piston rings are fitted into the ring grooves to reduce power loss due to blowby.

Constructional Features

It has to work under extreme temp. Variation many times through its normal functioning.

Slightly tapers towards the head in order to take care of complete mixing of air & fuel sufficient & desired expansion.

The piston top of the combustion chamber is designed to achieve

Adequate turbulance.

Complete mixing of fuel & air.

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BASIC COMPONENTS OF DIESEL ENGINEPart : Connecting Rod ( Specially Alloy steel like an 'I' beam. )Function

To transmit power developed in the Combustion chamber to the camshaft by linking it with the piston.

Constructional Features

Large end is spilt into two parts to make ease in fitment.

Due to typical 'I' shape or 'H' shape resists the twisting action & at the same time reduces the weight.

A connecting rod must be able to resist the compression loads between the small end & the big end bearing.

Remarks

Connecting rods are basically two types :

Mass balanced con. rod.

W/O mass balanced pad con. rod.

After undersizing big end bearing caps, pl. ensure that all the caps are Undersized for same size.

S .E . B us h

C o nnec ting R o d

B ig E nd B earing s

C o n. R o d B o lt (H ig h Tens ile b o lt)

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BASIC COMPONENTS OF DIESEL ENGINEPart : Cam-Shaft ( Special Alloy Steel )

Function

To transmit opening & closing of inlet & exhaust valve with the help of Push Rods. So that from air enters & exhaust gas leaves the cylinder according to the position of the piston. The timing is done through gears mechanism.

Constructional Features

It has cam lobs, slightly raised machined areas to open & close valves through Push Rods.

It has cam journals. It has thrust washer to adjust end play. It has a gears at one end to receive drive from the Crank-Shaft. It rotates at half the Crank-Shaft RPM.

C am S haft

C am J o urnalC am L o b e

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BASIC COMPONENTS OF DIESEL ENGINEPart : Cyl. head ( Cast Iron or Aluminium Alloy )

C ylind er H ead

C ylind er H ead G as ket

E xhaus t Valve

In let Valve

Function

Forms the top cover of combustion chamber.

It is fastened on top of cyl. block by cyl. head studs & nuts or bolts.

It Provides passages for air inlet & exhaust gases.

Supports nozzle.

Passage for water cooled engine.

Pre combustion Chambers.

Constructional Features

The face is finish & ground to obtain a gas tight joint, when it is placed on a block.

Two ferruls are fitted with rubber 'O' Rings in cyl. head bottom for Push Rods & to drain out the oil in the sump.

Remarks

Cyl. head needs to be lapped, whenever compression leakage is reported or Steel Gasket needs to be replaced.

Whenever cyl. head is removed ensure that all rubber 'O' rings are also replaced. (Because rubber gets deformed by applying torque ).

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BASIC COMPONENTS OF DIESEL ENGINEPart : Fasteners. - Bolts, nuts, Studs. ( steel ) Dowel Pins

Function

Holding adjacent parts rigidly of the engine.

To ensure correct & proper alignment of parts.

Constructional Features

All the fasteners particularly bolts of con. rod, balance weight & main brg cap are all high tensile fasteners which are subjected to severe working conditions.

Remarks

All bolts are graded as some make of bolt 8.8. (which is Tensile strength of the bolts.)

During engine overhaul, all high tensile fasteners should be replaced.of parts.

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