Auto Material Engine

5/21/2018 Auto Material Engine

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AUTOMOTIVE MATERIALS

Prepared By: Mr. Hardik Shah


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Syllabus

1. Engines

2. The cylinder

3. The piston & piston ring

4. The camshaft & crankshaft

5. The connecting rod

6. The catalyst


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Contents

The reciprocating engine

Advantages and disadvantages of

reciprocating engines

Engine components and typical materials

Recent trends in engine technology


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The reciprocating engine

The reciprocating engine is an engine in

which one or more pistons move up and

down in cylinders which gives power to

crankshaft to rotate. The engine is the heart of a car although it

is normally hidden under the bonnet.

Another type is rotary engine.


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Basics of Reciprocating Engines

The cylinder which is closed atone end is filled with amixture of fuel and air.

As the crankshaft turns it

pushes piston. The piston is forced up and

compresses the mixture in thetop of the cylinder.

The mixture is set alight and,as it burns, it creates a gas

pressure on the piston, forcingit down the cylinder.


7/36Air-cooled Reciprocating engine


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Constructional details of Reciprocating

Engines

A cross-section of an air-cooled engine with principal parts isshown in next page.

A. Parts common to both Petrol and Diesel engine:

1. Cylinder, 2. Cylinder head, 3. Piston,4. Piston rings, 5. Gudgeon pin, 6. Connecting rod,

7. Crankshaft, 8. Crank, 9. Engine bearing,

10. Crank case. 11. Flywheel, 12. Governor,

13. Valves and valve operating mechanism.

B. Parts for Petrol engines only:

1. Spark plug, 2. Carburetor, 3. Fuel pump.

C. Parts for Diesel engine only:

1. Fuel pump, 2. Injector.


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Four Stroke Engine


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Working of Four Stroke Engines

1. Intake stroke: the intake stroke draws air and fuel intothe combustion chamber. The piston descends in the

cylinder bore to evacuate the combustion chamber.

When the inlet valve opens, atmospheric pressure forces

the air-fuel charge into the evacuated chamber. As a

result, the combustible mixture of fuel and air fills the

chamber.


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2. Compression stroke: at the end of the intake stroke, bothinlet and exhaust valves are closed. The inertial action of

the crankshaft in turn lifts the piston which compresses

the mixture. The ratio of the combustion chamber

volume before and after compression is called thecompression ratio. Typically the value is approximately

9:1 in spark ignition engines and 15:1 in diesel engines.


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3. Power stroke: when the piston ascends and reaches topdead center, an electric current ignites the spark plug and

as the mixed gas burns, it expands and builds pressure in

the combustion chamber. The resulting pressure pushes

the piston down with several tons of force.


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4. Exhaust stroke: during the exhaust stroke, the inlet valveremains closed whilst the exhaust valve opens. The

moving piston pushes the burned fumes through the now

open exhaust port and another intake stroke starts again.


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Salient Features About Engines

During one cycle, the piston makes two round trips andthe crankshaft revolves twice.

The inlet and exhaust valves open and close only once.

The ignition plug also sparks only once.

A petrol engine, whether four- or two-stroke, is called aspark ignition (SI) engine because it fires with an

ignition plug.

The four-stroke-cycle engine contains the lubricating oil

in the crankcase. The oil lubricates the crankshaft bearings and cools the

hot piston


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The two-stroke engine is similar to that of the

four-stroke-cycle engine in its reciprocatingmechanism.

It uses the piston-crankshaft mechanism, butrequires only one revolution of the crankshaftfor a complete power-producing cycle.

The two-stroke engine does not use inlet andexhaust valves.

The gas exchange is implemented byscavenging and exhaust porthole openings inthe bore wall. The upward and downward

motion of the piston simultaneously opens andcloses these portholes. The air-fuel mixturethen goes in or out of the combustion chamberthrough the portholes. Combustion takes placeat every rotation of the crankshaft.

Two-stroke Engines


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The gas exchange is implemented byscavenging and exhaust porthole openings inthe bore wall.

The upward and downward motion of thepiston simultaneously opens and closes theseportholes.

The air-fuel mixture then goes in or out of thecombustion chamber through the portholes.

After spark ignition inside chamber,Combustion takes place at every rotation ofthe crankshaft.

Working of Two-stroke Engines


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In the two-stroke engine, the space in the

crankcase works as a pre-compressionchamber for each successive fuel charge.

The fuel and lubricating oil are premixed

and introduced into the crankcase, so that

the crankcase cannot be used for storingthe lubricating oil.

When combustion occurs in the cylinder,

the combustion pressure compresses the

new gas in the crankcase for the nextcombustion.

The burnt gas then exhausts while drawing

in new gas. The lubricating oil mixed into

the air-fuel mixture also burns

Features of Two-stroke Engines


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Diesel Engine

The only difference between

diesel engine and a four-stroke

gasoline engine is:

No sparkplug on Diesel engine.Has a higher compression ratio.

(14:1 to 25:1)

Better fuel mileage.


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Diesel Engine

Intake Stroke:

Piston moves from TDC

to BDC

creating vacuum in the

cylinder Intake valve

opens allowing only

airto enter the cylinder

andexhaust valve remains

closed


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Diesel Engine

Compression Stroke

Both valves stay closed

Piston moves from BDC to TDC,

compressing air to 22:1

Compressing the air to this extent

increases the temperature inside the

cylinder to above 1000 degree F.


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Diesel Engine

Power Stroke

Both valves stay closed

When the piston is at the end of

compression stroke(TDC) the injectorsprays a mist of diesel fuel into the

cylinder.

When hot air mixes with diesel fuel

an explosion takes place in the cylinder.

Expanding gases push the piston

from TDC to BDC


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Diesel Engine

Exhaust Stroke

Piston moves from BDC to

TDC

Exhaust valve opens and the

exhaust gases escape

Intake valve remains closed


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Diesel Engine

Four Strokes of Diesel Engine


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Thepiston losesspeed at the dead-centerpoints where the

travelling direction reverses, which gives enough time forcombustion and intake as well as for exhaust.

The piston ring faces the cylinder bore wall, separated by

an oilfilm. The resulting lubrication generates low friction

and high durability. By sealingthe gapbetween the piston and the cylinder,

high compression ratio, high heat efficiency and low fuel

consumption can be achieved.

Advantages of Reciprocating Engine

It is difficult to reuse the exhaustheat.

The unbalanced inertial force may results inpiston slap

that can cause noise and vibration.

Disadvantages of Reciprocating Engine


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Engine Components


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Parts Of An Engine.

PISTON

SPARK PLUG

CAM SHAFT

VALVE

ROCKER ARM


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Components and its work

Cylinder

A cylinder is the central working part

of a reciprocating engine or pump, the

space in which a piston travels

Gray cast iron, compact graphitecast iron, cast Al alloy

Piston

its purpose is to transfer force fromexpanding gas in the cylinder to

the crankshaft via a piston rod and/or

connecting rod

Al-Si-Cu-Mg alloy


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Piston rings

Piston rings provide a sliding sealbetween the outer edge of the piston

and the inner edge of the cylinder.

The rings serve two purposes:

They prevent the fuel/air mixture andexhaust in the combustion chamber

from leaking into the sump during

compression and combustion.

They keep oil in the sump fromleaking into the combustion area,

where it would be burned and lost.

Gray cast iron, spheroidized graphite

cast iron, alloy cast iron, spring steel

and stainless steel


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Connecting rod

The connecting rod connects the piston to the

crankshaft. It can rotate at both ends so that its anglecan change as the piston moves and the crankshaft

rotates.

Carbon steel, iron base sintered metal, micro-alloyed

steel, spheroidized graphite cast iron

CrankshaftThe crankshaft turns the piston's up and down motion

into circular motion just like a crank on a jack-in-the-

box does

Carbon steel, micro-alloyed steel, Cr-Mo steel and

nodular, cast iron

Sump

The sump surrounds the crankshaft. It contains some

amount of oil, which collects in the bottom of the sump

(the oil pan).


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Camshaft

Its an internal component of valve train whichcontrols the valve operation timing with pushrod or

rocker arms or self controlling lobes.

Chilled cast iron, Cr-Mo steel, iron base sintered

metal

Valve and Valve springThe valve which allows mixture into the cylinder is

the inlet valve; the one through which the spent

gases escape is the exhaust valve. They are designed

to open and close at precise moments, to allowthe engine to run efficiently at all speeds.

Valve: Heat-resistive steel, Ti alloy, SiC ceramics.

Valve spring:Spring steel, music wire

Valve Seat: Iron base sintered metal, cast iron


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Components and its workExhaust Manifold

The exhaust manifold is the first part of your vehicles exhaust

system.

It is connected to your vehicles engine and collects your

engines emissions.

The exhaust manifold receives the air/fuel mixture from the

multiple cylinders in your vehicles engine, it completely burnsany unused or incomplete burnt gases using its very high

temperature.


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Components and its workExhaust Manifold

The manifold also houses the first

oxygen sensor in your exhaust

system to inspect the amount of

oxygen entering the system.

Once the amount of gas in one

place completely burnt, the manifoldsends the emissions into the rest of

the exhaust system.

High-Si cast iron, niresist cast iron,cast stainless steel,stainless steel

tube and sheet

C d i k


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Engine Bearings

Bearing is a device supporting a mechanical

element and providing its movement relatively to

another element with a minimum power loss.

Main crankshaft bearings

It support the crankshaft and help it rotate under inertia forces

generated by the parts of the shaft and oscillating forces

transmitted by the connecting rods. Main bearings are

mounted in the crankcase

Connecting rod bearings

provide rotating motion of the crank pin within the

connecting rod, which transmits cycling loads applied to thepiston. Connecting rod

bearings are mounted in the Big end of the connecting rod.

Camshaft bearings

It support camshaft and provide its rotation.

Al-Si-Sn and Cu-Pb alloys


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Recent trends in engine technology1. The multi-valve engine was previously limited to sports

cars and motorcycles. To obtain higher output power, thenumber of valves used in car engines has increased.

2. The multi-cylinder engine has become more widespread.

It has a smoother rotation to decrease noise and

vibration.

3. Three-way catalyst (Pt-Pd-Rh alloy) technology, usingO2 and knock sensors, has decreased the three

components CO, HC, and NOx in the exhaust gas, to

decrease environmental pollution.

4. The variable valve system has decreased fuel

consumption.

5. Decreased inertial weight and electronic control have

given improved engine performance.

6. Hybrid systems including an electric motor have reduced

fuel consumption.

Part name Material


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Part name Material

Cylinder block Gray cast iron, compact graphite cast iron, cast Al alloy

Piston Al-Si-Cu-Mg alloy

Piston ring

Gray cast iron, spheroidized graphite cast iron, alloy cast iron, spring steel and

stainless steel

Camshaft Chilled cast iron, Cr-Mo steel, iron base sintered metal

Valve Heat-resistive steel, Ti alloy, SiC ceramics

Valve seat Iron base sintered metal, cast iron

Valve spring Spring steel, music wire

Piston pin Nodular cast iron, Si-Cr steel, stainless steel

Connecting rodCarbon steel, iron base sintered metal, micro-alloyed steel,spheroidized graphite

cast iron

Crankshaft Carbon steel, micro-alloyed steel, Cr-Mo steel and nodular,cast iron

Turbo charger Niresist cast iron, cast stainless steel, superalloy

Exhaust manifoldHigh-Si cast iron, niresist cast iron, cast stainless steel,stainless steel tube and

sheet

Plain bearing Al-Si-Sn and Cu-Pb alloys

- -


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