Diesel Automotive Engines Chapter 14

7/21/2019 Diesel Automotive Engines Chapter 14

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iesel Automotive

iesel Automotive

Enginesngines

Energy and Power TechnologyEnergy and Power Technology

TextbookTextbookChapter 14Chapter 14



As you study this

s you study this

chapter, you will learnhapter, you will learn

to:

o: Explain why the diesel engine has grown inExplain why the diesel engine has grown inpopularity as an automobile and truck engine.popularity as an automobile and truck engine.

Identify the two maor differences betweenIdentify the two maor differences between

gasoline and diesel engines.gasoline and diesel engines. !escribe the function and operation of the diesel!escribe the function and operation of the diesel

engine fuel"inection system.engine fuel"inection system. Explain the difference between multiple"plungerExplain the difference between multiple"plunger

and unit inector fuel"inection systems.and unit inector fuel"inection systems.

Identify the type of diesel engine that re#uires anIdentify the type of diesel engine that re#uires anair blower.air blower.



iesel Automotive

iesel Automotive

Enginesngines

!iesel engines ha$e!iesel engines ha$e

long been the source oflong been the source of

power for hea$y"dutypower for hea$y"duty

trucks% trains% and ships.trucks% trains% and ships.

!uring the past few!uring the past few

years% diesel enginesyears% diesel engines

ha$e become moreha$e become more

common as powercommon as powersources for automobiles.sources for automobiles.



iesel Engines in

iesel Engines in

Automobilesutomobiles

The main ad$antage of diesel engines o$er gasolineThe main ad$antage of diesel engines o$er gasolineengines is their good fuel efficiency.engines is their good fuel efficiency.

!iesel powered automobiles a$erage about &'( more!iesel powered automobiles a$erage about &'( moremiles per gallon than gasoline powered automobiles.miles per gallon than gasoline powered automobiles.

!iesel engines% howe$er% must be made larger% stronger%!iesel engines% howe$er% must be made larger% stronger%and hea$ier than gasoline engines.and hea$ier than gasoline engines.

They must withstand combustion pressures two to threeThey must withstand combustion pressures two to threetimes higher than those produced in gasoline engines.times higher than those produced in gasoline engines.

The added weight needed for strength reduces theThe added weight needed for strength reduces the

acceleration of the automobile.acceleration of the automobile. ) diesel engine of the same horsepower as a gasoline ) diesel engine of the same horsepower as a gasoline

engine is larger.engine is larger.



Types of iesel Engines

ypes of iesel Engines

There are two basic typesThere are two basic types

of diesel engines in useof diesel engines in use

today*today*

+our"stroke cycle+our"stroke cycle Two"stroke cycleTwo"stroke cycle

These engines differ in theThese engines differ in the

number of piston strokesnumber of piston strokes

re#uired to produce are#uired to produce a

power stroke.power stroke. Their methods of intake andTheir methods of intake and

exhaust are also different.exhaust are also different.



Four-Stroe !ycle iesel

our-Stroe !ycle iesel

Enginengine

+our"stroke diesel engines are $ery similar to four"stroke gasoline+our"stroke diesel engines are $ery similar to four"stroke gasolineengines.engines.

The piston tra$els from one end of the cylinder to the other fourThe piston tra$els from one end of the cylinder to the other fourtimes during each cycle.times during each cycle.

The fuel is ignited at the beginning of the third stroke of each cycle.The fuel is ignited at the beginning of the third stroke of each cycle. Intake air flows into each cylinder through intake $al$es in theIntake air flows into each cylinder through intake $al$es in the

cylinder head.cylinder head. Exhaust gases lea$e through exhaust $al$es.Exhaust gases lea$e through exhaust $al$es. These $al$es operate the same way as the $al$es in four"strokeThese $al$es operate the same way as the $al$es in four"stroke

gasoline engines.gasoline engines.

,n the intake stroke% atmospheric pressure pushes air into the,n the intake stroke% atmospheric pressure pushes air into thecylinder through the intake $al$e.cylinder through the intake $al$e.

The exhaust stroke forces burned gases out through the exhaustThe exhaust stroke forces burned gases out through the exhaust$al$e.$al$e.

!uring the compression and power strokes% both $al$es are closed.!uring the compression and power strokes% both $al$es are closed.





Two-Stroe !ycle iesel

wo-Stroe !ycle iesel

Enginengine

Two"stroke diesel engines are similar to two"strokeTwo"stroke diesel engines are similar to two"strokegasoline engines.gasoline engines.

They ha$e only two strokes per cycle.They ha$e only two strokes per cycle.

The fuel is ignited on e$ery other stroke of the piston.The fuel is ignited on e$ery other stroke of the piston. In the two"stroke diesel engine% air is forced in andIn the two"stroke diesel engine% air is forced in and

exhaust gases are forced out on a single stroke.exhaust gases are forced out on a single stroke.

-sually a blower forces air into the cylinder through-sually a blower forces air into the cylinder through

intake ports.intake ports. The incoming air pushes remaining exhaust gases outThe incoming air pushes remaining exhaust gases out

of the cylinder through an exhaust $al$e.of the cylinder through an exhaust $al$e.





Engine esign

ngine esign

The diesel engine looks much like the gasolineThe diesel engine looks much like the gasolineengine.engine.

The operations of the mechanical systems areThe operations of the mechanical systems arealso similar in both engines.also similar in both engines.

The piston and crankshaft assembly% the $al$eThe piston and crankshaft assembly% the $al$eassembly% the lubrication system% and theassembly% the lubrication system% and the

cooling system operate in the same way.cooling system operate in the same way. owe$er% diesel systems are built stronger toowe$er% diesel systems are built stronger to

withstand higher combustion pressures.withstand higher combustion pressures.



Engine esign !ontinued

ngine esign !ontinued

The two maor differences between gasoline andThe two maor differences between gasoline anddiesel engines are the way that fuel is supplied todiesel engines are the way that fuel is supplied tothe cylinders and the way the fuel is ignited.the cylinders and the way the fuel is ignited.

The diesel engine does not need an ignitionThe diesel engine does not need an ignitionsystem.system.

Compression heat ignites the fuel in the cylinder.Compression heat ignites the fuel in the cylinder.

) special fuel system supplies fuel to the cylinder. ) special fuel system supplies fuel to the cylinder.

!iesel fuel systems are $ery different from!iesel fuel systems are $ery different fromgasoline fuel systems.gasoline fuel systems.



Fuel System

uel System

In a gasoline engine% fuel is mixed with air in theIn a gasoline engine% fuel is mixed with air in thecarburetor or in the intake manifold.carburetor or in the intake manifold.

!iesel engines do not ha$e carburetors.!iesel engines do not ha$e carburetors.

,nly air flows into the combustion chamber through the,nly air flows into the combustion chamber through theintake manifold.intake manifold.

Each intake stroke completely fills the cylinder with air.Each intake stroke completely fills the cylinder with air.

/pecial de$ices inect fuel into the air inside the/pecial de$ices inect fuel into the air inside the

cylinder.cylinder. Engine power is controlled by metering the amount ofEngine power is controlled by metering the amount of

fuel inected into the cylinders.fuel inected into the cylinders.



Fuel System !ontinued

uel System !ontinued

)t idle% only a small amount of fuel is inected into each )t idle% only a small amount of fuel is inected into eachcylinder.cylinder.

The ratio of air to fuel may be 40 to 1.The ratio of air to fuel may be 40 to 1.

The ratio in gasoline engines at idle is about 1 to 1.The ratio in gasoline engines at idle is about 1 to 1. )s power needs increase% the amount of fuel inected )s power needs increase% the amount of fuel inected

increases.increases.

owe$er the amount of air remains the same.owe$er the amount of air remains the same.

Therefore% the ratio of air to fuel decreases.Therefore% the ratio of air to fuel decreases. The intake stroke always takes in enough air to burn allThe intake stroke always takes in enough air to burn all

the fuel inected during full"load operation.the fuel inected during full"load operation.



Fuel-"n#ection Systems

uel-"n#ection Systems

The main components in a diesel fuel"inectionThe main components in a diesel fuel"inectionsystem are the fuel"inection pump and the fuelsystem are the fuel"inection pump and the fuelinectors.inectors.

The ob of the fuel inectors is to inect aThe ob of the fuel inectors is to inect ameasured amount of fuel into the combustionmeasured amount of fuel into the combustionchamber.chamber.

2hen pressure is applied to the fuel% the2hen pressure is applied to the fuel% theinector opens and sprays fuel into the cylinder.inector opens and sprays fuel into the cylinder.

Combustion begins immediately.Combustion begins immediately.





!ontinuedontinued

The fuel"inection pump produces theThe fuel"inection pump produces thenecessary high fuel pressure.necessary high fuel pressure.

,n inection% diesel fuel must be under enough,n inection% diesel fuel must be under enough

pressure to offset the pressure inside thepressure to offset the pressure inside thecombustion chamber 3about 1000 psi duringcombustion chamber 3about 1000 psi duringcombustion.combustion.

If the fuel pressure were not at least as high asIf the fuel pressure were not at least as high as

the pressure in the combustion chamber duringthe pressure in the combustion chamber duringcombustion% the fuel would not inect.combustion% the fuel would not inect. Instead% pressure would leak from theInstead% pressure would leak from the

combustion chamber into the inector no55le.combustion chamber into the inector no55le.





!ontinuedontinued

The inection pump has two other functions.The inection pump has two other functions. It must regulate the amount of fuel directed to the cylinder.It must regulate the amount of fuel directed to the cylinder. It must also control the timing of the fuel inection.It must also control the timing of the fuel inection.

Engine power depends on the amount of fuel supplied toEngine power depends on the amount of fuel supplied tothe cylinders.the cylinders. The time at which inectors spray fuel into the cylinders isThe time at which inectors spray fuel into the cylinders is

ust as important. ust as important. The inection pump controls this timing.The inection pump controls this timing.

It makes sure that the inectors spray fuel ust before T!CIt makes sure that the inectors spray fuel ust before T!C3top dead center of the compression stroke.3top dead center of the compression stroke. 6y the time the fuel ignites% the piston will ha$e started its6y the time the fuel ignites% the piston will ha$e started its

downward motion.downward motion.



Fuel "n#ection

uel "n#ection

Arrangementsrrangements

The inection pump and inectors may notThe inection pump and inectors may not

be completely separate.be completely separate.

These two parts can be arranged in threeThese two parts can be arranged in threedifferent ways.different ways.

7ultiple"Plunger /ystem7ultiple"Plunger /ystem

-nit Inector /ystem-nit Inector /ystem !istributor /ystem!istributor /ystem



$ultiple-%lunger System

ultiple-%lunger System

In this system% there is a separate pumping unitIn this system% there is a separate pumping unit3plunger and a separate inector for each3plunger and a separate inector for eachcylinder.cylinder.

The plungers are all part of the fuel"inectionThe plungers are all part of the fuel"inectionpump.pump.

) camshaft inside the pump controls the action ) camshaft inside the pump controls the actionof the plungers.of the plungers.

+uel lines connect the plungers to the inectors.+uel lines connect the plungers to the inectors. The amount of fuel to be inected is controlledThe amount of fuel to be inected is controlled

at the fuel"inection pump.at the fuel"inection pump.



&nit "n#ector System

nit "n#ector System

In this system% the inection pump andIn this system% the inection pump andinector are combined into one unit andinector are combined into one unit and

are dri$en by the o$erhead camshaft.are dri$en by the o$erhead camshaft. The plunger is a part of the inector.The plunger is a part of the inector.

Pressuri5ation% timing% and metering ofPressuri5ation% timing% and metering of

the fuel all take place in the unit inector.the fuel all take place in the unit inector. )n engine with this system has one unit )n engine with this system has one unit

inector for each cylinder.inector for each cylinder.



istributor System

istributor System

In this system% a single inection pumpIn this system% a single inection pump

supplies fuel to a distributor.supplies fuel to a distributor.

The distributor directs fuel to the inectorsThe distributor directs fuel to the inectorsin the right firing order.in the right firing order.

The metering of fuel is done at the pump.The metering of fuel is done at the pump.



Fuel-"n#ection System

uel-"n#ection System

'peration

peration

!iesel engines use se$eral different inection systems.!iesel engines use se$eral different inection systems. Their operating principles are the same.Their operating principles are the same. The multiple"plunger system contains both high" andThe multiple"plunger system contains both high" and

low"pressure fuel systems.low"pressure fuel systems. The low"pressure system consists of a fuel pump%The low"pressure system consists of a fuel pump%

lines% and filters% similar to the parts in a gasolinelines% and filters% similar to the parts in a gasolinesystem.system.

These parts deli$er fuel from the tank to the fuel"These parts deli$er fuel from the tank to the fuel"

inection pump.inection pump. The high"pressure system consists of the fuel"inectionThe high"pressure system consists of the fuel"inection

pump and the inectors.pump and the inectors. These parts supply fuel to the cylinders.These parts supply fuel to the cylinders.



(low %lugs

low %lugs

6ecause there is no spark to ignite the fuel% diesel engines can6ecause there is no spark to ignite the fuel% diesel engines canbe hard to start.be hard to start.

This is especially true in cold weather.This is especially true in cold weather. +or impro$ed starting% diesels are often e#uipped with glow+or impro$ed starting% diesels are often e#uipped with glow

plugs.plugs. 8low plugs ha$e a small wire element that gets red"hot when8low plugs ha$e a small wire element that gets red"hot when

connected to an electrical source.connected to an electrical source. Each cylinder has a glow plug.Each cylinder has a glow plug. 2hen the diesel is to be started% current from the battery heats2hen the diesel is to be started% current from the battery heats

the glow plugs.the glow plugs. The glow plugs then heat the fuel as it enters the cylinders.The glow plugs then heat the fuel as it enters the cylinders. This preheating of the fuel lowers its ignition point to impro$eThis preheating of the fuel lowers its ignition point to impro$e

starting.starting.





Air )lowers and

ir )lowers and

Turbochargers

urbochargers

Two"stroke diesel engines re#uire an airTwo"stroke diesel engines re#uire an airblower.blower.

This de$ice forces air into the cylinder andThis de$ice forces air into the cylinder and

dri$es out the exhaust gases.dri$es out the exhaust gases. 2hen the piston reaches the bottom of the2hen the piston reaches the bottom of the

power stroke% the air inlet ports are unco$ered.power stroke% the air inlet ports are unco$ered. The blower forces air into the cylinder.The blower forces air into the cylinder. The air dri$es the burned gases out theThe air dri$es the burned gases out the

exhaust $al$e and fills the combustionexhaust $al$e and fills the combustionchamber.chamber.



Air )lowers and

ir )lowers and

Turbochargers

urbochargers

!ontinuedontinued

/ome modern four"stroke diesel engines use a special/ome modern four"stroke diesel engines use a specialkind of blower called a turbocharger.kind of blower called a turbocharger.

) turbocharger consists of an air impellor and an ) turbocharger consists of an air impellor and an

exhaust turbine connected to a shaft.exhaust turbine connected to a shaft. igh"pressure exhaust gases lea$ing the engine dri$eigh"pressure exhaust gases lea$ing the engine dri$ethe turbine.the turbine.

The turbine% in turn% dri$es the air impellor.The turbine% in turn% dri$es the air impellor. The air impellor forces air into the combustion chamberThe air impellor forces air into the combustion chamber

at a pressure higher than atmospheric pressure.at a pressure higher than atmospheric pressure. The action puts more air into the cylinder.The action puts more air into the cylinder. This pro$ides higher compression for greater powerThis pro$ides higher compression for greater power

output.output.





Test *our +nowledge

est *our +nowledge

uestion

uestion

1.1. 2hat factor helped2hat factor helped

diesel enginesdiesel engines

grow in popularitygrow in popularity

as an automoti$eas an automoti$e

engine9engine9

8ood +uel Efficiency8ood +uel Efficiency



Test *our +nowledge

est *our +nowledge

uestion

uestion

&.&. :ame the two maor differences between gasoline:ame the two maor differences between gasoline

and diesel engines9and diesel engines9

The way fuel is supplied to the cylinders 3fuel inectionThe way fuel is supplied to the cylinders 3fuel inection

)nd the way the fuel is ignited 3compression ignition. )nd the way the fuel is ignited 3compression ignition.



Test *our +nowledge

est *our +nowledge

uestion

uestion

;.;. 2hat is the function2hat is the function

of the diesel engineof the diesel engine

fuel inector9fuel inector9

To inect a measuredTo inect a measured

amount of fuel intoamount of fuel into

the combustionthe combustion

chamber.chamber.



Test *our +nowledge

est *our +nowledge

uestion

uestion

4.4. 2hat is the function of the glow plug92hat is the function of the glow plug9

!uring starting% the glow plug heats the!uring starting% the glow plug heats the

fuel as it enters the cylinder. Thisfuel as it enters the cylinder. This

lowers the fuel<s ignition point tolowers the fuel<s ignition point to

impro$e starting.impro$e starting.



Test *our +nowledge

est *our +nowledge

uestion

uestion

'.'. 2hich type of diesel engine re#uires an2hich type of diesel engine re#uires an

air blower9air blower9

Two"stroke cycle engine.Two"stroke cycle engine.



Any 'ther uestionsny 'ther uestions

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Diesel Automotive Engines Chapter 14