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Internal Combustion Engines

ME:402331Chapter 1

Introduction To Internal Combustion Engines

Dr.Mohammad Al-Tarawneh





ENGINE CLASSIFICATIONS



1. Types of Ignition

(a) Spark Ignition (SI)

(b) Compression Ignition (CI)

2. Engine Cycle

(a) Four-Stroke Cycle

(b) Two-Stroke Cycle

An SI engine starts the combustionprocess in each cycle by use of a sparkplug.

self-ignites due to high temperature in thecombustion chamber caused by highcompression.

A four-stroke cycle experiences four pistonmovements over two engine revolutions for each cycle.

A two-stroke cycle has two pistonmovements over one revolution for eachcycle.



3. Valve Location (a) Valves in head (overhead valve)

also Called I Head engine.

(b) Valves in block (flat head)

(c) One valve in head (usually intake)and one in block, also called F Headengine





4. Basic Design

(a) Reciprocating

(b) Rotary

5. Position and Number of Cylinders of Reciprocating Engines

(a) Single Cylinder

(b) In-Line

(c) V Engine

d) Opposed Cylinder Engine.

(e) W Engine.

(f) Opposed Piston Engine.

(g) Radial Engine.





6. Air Intake Process(a) Naturally Aspirated.

(b) Supercharged.

(c) Turbocharged.



Supercharger



Turbocharger



7. Method of Fuel Input for SIEngines

(a) Carbureted.(b) Multipoint Port Fuel Injection. One or more injectors at each cylinder intake.(c) Throttle Body Fuel Injection. Injectors upstream in intake manifold.

8. Fuel Used(a) Gasoline..

(b) Diesel Oil or Fuel Oil.(c) Gas, Natural Gas, Methane.(d) LPG.

(e) Alcohol-Ethyl, Methyl.(f) Dual Fuel. There are a number of engines that use a combination of two or more fuels. Some, usually large, CI engines use a combination of methaneand diesel fuel. These are attractive in developing third-world countriesbecause of the high cost of diesel fuel. Combined gasoline-alcohol fuels



8. Fuel Used(a) Gasoline &Combined gasoline-alcohol fuelsGasohol (Common fuel consisting of 90%gasoline and 10% alcohol)(b) Diesel Oil or Fuel Oil.(c) Gas, Natural Gas, Methane.

(d) LPG.(e) Alcohol-Ethyle, Methyle.(f) Dual Fuel. There are a number of enginesthat use a combination of two or more fuels.Some, usually large, CI engines use acombination of methane and diesel fuel.These are attractive in developing third-worldcountries because of the high cost of diesel

fuel.



Engine classifications

9. Application(a) Automobile, Truck, Bus.(b) Locomotive.

(c) Stationary.(d) Marine.(e) Aircraft.(f) Small Portable, Chain Saw, Model Airplane.

10. Type of Cooling(a) Air Cooled.(b) Liquid Cooled, Water Cooled.



Cross-section of four-stroke cycle SI engine showing engine components



(A) block, (B) camshaft, (C) combustionchamber, (D) connecting rod, (E)

crankcase, (F) crankshaft, (G) cylinder, (H)exhaust manifold, (I) head, (J) intake

manifold, (K) oil pan, (L) piston, (M) pistonrings, (N) push rod, (0) spark plug, (P)

valve, (Q) water jacket.

ENGINE COMPONENTS



Four-Stroke SI Engine Cycle





First Stroke: Intake Stroke or Induction : The piston travels fromTDC to BDC with the intake valve open and exhaustvalve closed. This creates an increasing volume in thecombustion chamber, which in turn creates a vacuum.The resulting pressure differential through the intake

system from atmospheric pressure on the outside tothe vacuum on the inside causes air to be pushed intothe cylinder. As the air passes through the intakesystem, fuel is added to it in the desired amount bymeans of fuel injectors or a carburetor



2. Second Stroke Compression Stroke:

When the piston reaches BDC, the intake valvecloses and the piston travels back to TDC with allvalves closed. This compresses the air-fuelmixture, raising both the pressure and

temperature in the cylinder. The finite timerequired to close the intake valve means thatactual compression doesn't start until sometime aBDC. Near the end of the compression stroke,the spark plug is fired and combustion is initiated.



3. Combustion

Combustion of the air-fuel mixture occurs in avery short but finite length of time with the pistonnear TDC( nearly constant-volume combustion).

It starts near the end of the compression strokeslightly bTDC and lasts into the power strokeslightly aTDC. Combustion changes the

composition of the gas mixture to that of exhaustproducts and increases the temperature in thecylinder to a very high peak.



4. Expansion Stroke

Expansion Stroke or Power Stroke With allvalves closed, the high pressure createdby the combustion process pushes the

piston away from TDC. This is the strokewhich produces the work output of theengine cycle. As the piston travels from

TDC to BDC, cylinder volume is increased,causing pressure and temperature to drop.



5. Exhaust Blow down : Late in the power stroke, the exhaust valve is opened

and exhaust blow down occurs. Pressure andtemperature in the cylinder are still high relative tothe surroundings at this point, and a pressuredifferential is created through the exhaust system

which is open to atmospheric pressure. This pressuredifferential causes much of the hot exhaust gas to bepushed out of the cylinder and through the exhaustsystem when the piston is near BDC. This exhaustgas carries away a high amount of enthalpy, which

lowers the cycle thermal efficiency. Opening theexhaust valve before BDC reduces the work obtainedduring the power stroke but is required because of the finite time needed for exhaust blow down.



6. Exhaust Stroke By the time the piston reaches BDC, exhaust

blow down is complete, but the cylinder is stillfull of exhaust gases at approximatelyatmospheric pressure. With the exhaust valveremaining open, the piston now travels fromBDC to TDC in the exhaust stroke. This pushes

most of the remaining exhaust gases out of thecylinder into the exhaust system at aboutatmospheric pressure, leaving only that trappedin the clearance volume when the pistonreaches TDC. Near the end of the exhauststroke bTDC, the intake valve starts to open.



open, so that it is fully open by TDC whenthe new intake stroke starts the next

cycle. Near TDC the exhaust valve starts toclose and finally is fully closed sometime

aTDC. This period when both the intakevalve and exhaust valve are open is called

valve overlap.

6. Exhaust Stroke



Summery OF STROKES



Two-Stroke SI Engine Cycle



1. Combustion

With the piston at TDC combustion occursvery quickly, raising the temperature andpressure to peak values, almost at

constant volume.



2. First Stroke: Expansion Stroke or Power Stroke

Very high pressure created by thecombustion process forces the pistondown in the power stroke. The

expanding volume of the combustionchamber causes pressure andtemperature to decrease as the pistontravels towards BDC.



3. Exhaust Blowdown

At about 75° bBDC, the exhaust valve opensand blowdown occurs. The exhaust valvemay be a poppet valve in the cylinder

head, or it may be a slot in the side of thecylinder which is uncovered as the piston

approaches BDC. After blowdown the

cylinder remains filled with exhaust gas atlower pressure.



Poppet Valve

Poppet valve is springloaded closed, andpushed open by camaction at proper time incycle. Most automobileengines and other

reciprocatingengines use poppetvalves. Much lesscommon are sleevevalves and rotaryvalves. Components

include: (A) valveseat, (B) head, (C) stem,(D) guide, (E)spring, (F) camshaft, (G)manifold.



Intake and Scavenging

When blowdown is nearly complete, at about 50°bBDC, the intake slot on the side of the cylinder isuncovered and intake air-fuel enters under pressure. Fuel is added to the air with either a

carburetor or fuel injection. This incomingmixture pushes much of the remaining exhaustgases out the open exhaust valve and fills thecylinder with a combustible air-fuel mixture, a

process called scavenging. The piston passesBDC and very quickly covers the intake port andthen the exhaust port (or the exhaust valvecloses).



Second Stroke: Compression Stroke

With all valves (or ports) closed, the

piston travels towards TDC and compressesthe air-fuel mixture to a higher pressure

and temperature. Near the end of thecompression stroke, the spark plug is

fired; by the time the piston gets to TDC,combustion occurs and the next engine

cycle begins.



Two-Stroke CI Engine Cycle

The two-stroke cycle for a CI engine is similar tothat of the SI engine, except for

two changes. No fuel is added to the incoming air,so that compression is done on air only. Insteadof a spark plug, a fuel injector is located in thecylinder. Near the end of the compressionstroke, fuel is injected into the hot compressedair and combustion is initiated by self-ignition



Specifications of the Engine

1996 General Motors L67 3800Series II spark ignition, four-strokecycle, overhead valve, 3.8 liter, V6

engine. This supercharged enginehas two valves per cylinder andhas power and torque ratings of

240 hp (179 kW) at 5200 RPM and280 Ibf-ft (380 N-m) at 3600 RPM.



Specifications of the Engine

General Motors Northstar VB engine used in 1995Cadillac automobiles. This four-stroke cycle,spark ignition, 32 valve, double overhead cam

engine has a 4.6 L displacement and multipointport fuel injection. If the cooling system of thisengine has a leak, the automobile can be drivenat moderate speed for up to fifty miles without

coolant fluid, without damage to the engine.Copyright General Motors Corp., used withpermission

H b id C



Hybrid Cars

-Mix between gasoline-powered car and anelectric car

-Rising fuel costs and better designs are makinghybrids more and more competitive

-Incremental cost more than standard equivalentis about $2,000-$3,000

-U.S. Energy Policy Act of 2005 provides a taxcredit of up to $3,400 for owners of hybrid

cars to help make hybrids morecompetitive

H b id



Hybrids

•The gasoline engine can be turned off atstop signs, doesn’t need to be on at alltimes.

•Key components of the car like the air-

conditioning can run off the battery

•The best hybrids have made fueleconomy gains of 30-80% while

maintaining, and sometimes, increasinghorsepower with no decline in weight or size

Hybrids



Hybrids

Hybrids have smaller, more efficient gasengines

Regenerative breaking—hybrid carscapture some of the energy usually lost

through heat when a car breaks andstores it in the battery



History of HEVs

Evolution of HEVs

1997 – first modern HEV introduced inJapan:

Toyota Prius (on left below)

1999 – first modern HEV sold in U.S.:Honda Insight (on right below)

What Is a Hybrid



What Is a HybridElectric Vehicle (HEV)?

The combination of an internal

combustion engine (ICE) with one or

more electric motor/generators and a

battery pack An HEV uses less gasoline because the

electric motor does some of the work.

An HEV reduces air pollution and

improves U.S. energy security by using

less foreign oil.



Basic Components of HEVs



How HEVs Work

HEVs offer the efficiency of electric-poweredvehicles without having to recharge by usingconventional engines and fuels. Efficiencies are gained from motor down-sizingand regenerative braking

Inherent flexibility allows use for numerousapplicationsHEV Efficiency Three key factors: Regenerative braking

Engine size Vehicle weight &aerodynamic design



HEV Efficiency

Three key factors:

Regenerative braking Engine size

Vehicle weight &

aerodynamic design

ff



HEV Efficiency

Engine size = may be smaller than in aconventional

vehicle

Engine is sized to accommodateaverage load – not peak load

Vehicle weight/aerodynamic design:

Built using special lightweight materials Uses advanced aerodynamics to reducedrag



Regenerative Braking

Recaptures kinetic energy normally lost asheat during braking Kinetic energy = energy of motion Electric motor acts as a generator whenbrakesapplied Converts kinetic energy to electrical energy,stored in batteries It becomes potential energy – available for use No system is 100% efficient

HEV d Ai P ll ti



HEVs and Air Pollution

Decreased fuel consumption results in reducedvehicle emissions Ability to operate with smaller, more efficientmotor maximizes emission managementstrategies Result is reduction of harmful pollutants in

atmosphereHEVs in Transportation Increasing gasoline pricesare making HEVs veryattractive to consumers HEVs are alreadyavailable today, and their use will become morewidespread as productionpicks up

H b id R li bilit



Hybrid Reliability

Hybrids have some of the highest safety

ratings of all vehicles

High-voltage system contains many

safety features

Battery charge is computer controlled –

extends battery life

Batteries under warranty for 100,000

miles, is your engine?

H b id R li bilit



Hybrid Reliability

The cost of maintenance is reduced due

to operation of hybrid technology

Regenerative braking reduces wear on

brakes

Idle stop extends engine life

Electric accessories reduce load onengine

HEV Ad t



HEV Advantages

Reduced fuel consumption

Excellent gas mileage

Fewer tailpipe emissions

Lighter batteries than electric vehicles

Regenerative braking system storeselectrical energy in

batteries Uses less fuel to recharge batteries





Hybrid structure

Figure 3. Parallel hybrid car Figure 4. Series hybrid car

electric motor

fuel tank

engine

batteries

transmission

electric

motor

transmission

generator

engine

fuel tank

batteries



Current Models of HEVs

More manufacturers are designing andmarketing hybrid vehicles•Chevrolet Tahoe Hybrid

•Honda Accord Hybrid•Honda Civic Hybrid

•Ford Escape Hybrid

•GMC Silverado Hybrid

•GMC Sierra Hybrid

•Toyota Prius

•Toyota Highlander Hybrid

•Lexus 400h

C t M d l f HEV



Current Models of HEVs

Lexus GS 450h Lexus 600h

Mazda Tribute Hybrid

Mercury Mariner Hybrid

Saturn Aura Green Line

Saturn VUE Green Line

Chevrolet Malibu Hybrid

GMC Yukon Hybrid

T t P i H b id



Toyota Prius Hybrid



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