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INTERNAL COMBUSTION ENGINES ADDIS ABABA UNIVERSITY INSTITUTE OF TECHNOLOGY

SCHOOL OF MECHANICAL AND INDUSTRIAL ENGINEERING DIVISON OF THERMAL AND ENERGY CONVERSION By Desta Lemma (BSc, MSc)

The first fairly practical engine 1860 by J.J.E Lenoir

Plug in hybrid electric vehicle

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CHAPTER ONE
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Contents

Why we study about engines Definition of engine Definition of heat engine Heat engine and classification

Internal combustion ngine External combustion engine

Historical development of IC engines

Why we study about heat engine?

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Engines are one of the greatest achievement of the 20 century, that makes human life easy

Automobile Airplane Agricultural mechanization Petrochemical and mechanical technologies

Engines are the foundation for the development of many other important inventions Internal-combustion engines are expected to remain the dominant power source for vehicles at least for the next 20 years Improvement in energy efficiency and emission reduction are still possible

Why We Study about Heat Engines?

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ARE HEAT ENGINES BOON OR BANE?

OR
Greatest invention since the wheel Made transportation easy! Made life easy! Increased pollution Increased fossil fuel consumption Increased congestion on roads

Why We Study about Heat Engines?

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Whether we like it or not. CAN WE DO WITHOUT IT? Do we have viable alternatives?

THINK

As of today we have no answer May be for at least 20 years more! SO WE ARE STUCK WITH IT!

Definition of Engine
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Engine
is

a device which transforms one form of energy into another form. of the engines convert Thermal Energy into Mechanical Work and therefore they are called Heat Engine.
Thermal Energy Combustion Heat Engine Mechanical Energy

Most

Fuel Energy

Definition of Heat Engines

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Any device that is capable of converting Thermal energy into Mechanical energy (work). Heat is generally generated by chemical reaction, typically from combustion of all sorts of fuels Conversion of the available thermal energy into mechanical energy is governed by laws The transfer of thermal energy is accompanied with Q dS= the entropy transfer
T

heat

What is Heat engine ?

hot reservoir TH work impossible cyclic heat engine hot reservoir, TH entropy heat heat work

cold reservoir, TC

Types of Heat Engines

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Heat Engines can be broadly classified in to two categories

Internal

Combustion Engine (IC Engine) External Combustion Engine (EC Engine)

Heat Engines Classification

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How EC differs from IC ?

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The burning of fuel takes place outside the engine. A working fluid is utilized to transfer heat of combustion to the engine where in this heat is transformed into mechanical energy. A common example of this type is the steam power plant employing a boiler and a turbine Such an arrangement is not generally desirable for mobile power plants, since it entails the use of heavy and bulky heat exchangers, as well as the transportation of the supply working fluid.

Steam Power Plant (EC Engine)

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Gas Turbine Engines (IC Engines)

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Turbo-Jet

Turbo-Prop

Turbo-Fan

How IC differs from EC ?

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The combustion of a fossil fuel occurs in a combustion chamber in the portion of the engine which converts heat to mechanical energy The expanding gases drive the engine directly The products of combustion are rejected back to the atmosphere. There is no necessity for an intermediate heat transferring apparatus, thus eliminating the need for heavy and bulky heat exchangers and the necessity of transporting the working fluid.

Basics of Internal Cobustion Engine

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The internal combustion engine (IC) is a heat engine that converts chemical energy in a fuel into Mechanical energy. Chemical energy of the fuel is first converted to thermal energy by means of combustion or oxidation with air inside the engine. This thermal energy raises the temperature and pressure of the gases within the engine, and the high-pressure gas then expands against the mechanical mechanisms of the engine.

Basics of Internal Cobustion Engine

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This expansion is converted by the mechanical linkages of the engine to a rotating crankshaft, which is the output of the engine. The crankshaft, in turn, is connected to a transmission and/or power train to transmit the rotating mechanical energy to the desired final use. For engines this will often be the propulsion of a vehicle (i.e., automobile, truck, locomotive, marine vessel, or airplane).

Internal combustion engine

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IC engine

Historical Development of IC Engines

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1860: The first fairly practical IC engine was invented by J.J.E. Lenoir (1822-1900)

a single-cylinder, double-acting horizontal engine, with two power strokes per revolution Induction of a mixture of coal gas and air exhaust of the burnt mixture were controlled by slide valves ignited by a "jumping spark" ignition system

During the next decade, several hundred of these engines were built with power up to about 4.5 kW (6 hp) and efficiency up to 5%.

Historical Development of IC Engines

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Otto-Langen Engine In 1867, the Otto-Langen engine, with efficiency improved to about 11%, was first introduced, and several thousand of these were produced during the next decade. This was a type of atmospheric engine with the power stroke propelled by atmospheric pressure acting against a vacuum

The fuel consumption was about half that of the Lenoir Engine. The main features of the engine were a

long vertical cylinder, Heavy piston and Racked piston rod

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Otto- Langen Engine

Nicolaus A. Otto (1832-1891)

Eugen Langen (1833-1895)

Otto- Langen Engine

Historical Development of IC Engines

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Otto Engine
In 1876, to overcome the shortcomings of low thermal efficiency and excessive weight, Otto proposed an engine cycle with four piston strokes:

an intake stroke, a compression stroke before ignition, an expansion or power stroke where work was delivered to the crankshaft, and an exhaust stroke.

His prototype four-stroke engine first ran in 1876.

Historical Development of IC Engines

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Four-stroke I.C engine ( Nicolaus Otto in 1877) Mode operation

Downward intake stroke coal-gas and air enter the piston chamber, Upward compression stroke the piston compresses the mixture, Downward power stroke ignites the fuel mixture by electric spark, and Upward exhaust stroke releases exhaust gas from the piston chamber

Historical Development of IC Engines

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Karl

Benz and Gottlieb Daimler gasoline engine

In1883, Karl Benz and Gottlieb Daimler, built an engine, where gasoline is induced into the induction air through a surface carburetor For the first time people succeeded in using liquid fuels. A large step was done toward the automobile with this, because liquid fuel needs less space than gaseous and can be transported more easily

Historical Development of IC Engines

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Two-Stroke
1880, Sir Dugald Clark developed the first two-stroke internal combustion engines where the exhaust and intake processes occur during the end of the power stroke and the beginning of the compression stroke. It reduces or even replace the complicated valve mechanism led to invention of the two stroke engine. The need for less number of strokes than four strokes and that performs the same power as the Otto engine

Historical Development of IC Engines

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Diesel Engine
1892: The German engineer Rudolf Diesel (1858-1913) outlined in his patent a new form of internal combustion engine. His concept of initiating combustion by injecting a liquid fuel into air heated solely by compression permitted a doubling of efficiency over other internal combustion engines. Much greater expansion ratios, without detonation or knock, were now possible.

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Diesel engine: Mode of operation

Suction stroke: Pure air gets sucked in by the piston sliding downward. Compression stroke: The piston compresses the air above and uses thereby work, performed by the crankshaft. Power stroke: The piston gets moved downward due to high pressure and temperature upon combustion and performs work to the crankshaft. Expulsion stroke: The burned exhaust gases are ejected out of the cylinder through a second valve by the piston sliding upward again.

1.

2.

3.

4.

Historical Development of IC Engines

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Wankel (Rotary Engine) (1929)

Operate in four stroke principle Advantages:

High power output More reliable Simple structure and less moving parts Lower production cost Lighter and higher speed Air-fuel mixing problem High hydrocarbon emissions Less fuel efficiency Sealing difficulty

Disadvantages :

Historical Development of IC Engines

Current Engine Challenges

Limited energy supply Global warming effect Environmental protection (Less pollutant emissions)

Historical Development of IC Engines

Currently, five technologies that make IC engine better are

Clean diesel Direct injection Cylinder deactivation Turbocharger Variable valve timing

The IC engine will remain the dominant power source for vehicles until 2050 if it is assisted by

Technology advancement Infrastructure Less manufacture cost

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Classification of IC Engines

Engines can be classified according to the following criterias

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Application Basic Engine Design Operating Cycle Working Cycle Valve/Port Design and Location Fuel Mixture Preparation Ignition Stratification of Charge Combustion Chamber Design Method of Load Control Cooling

Classification of IC Engines
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1. APPLICATION

Automotive Locomotive Light Aircraft Marine Power Generation Agricultural Earthmoving Home Use Others

Classification of IC Engines
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2. BASIC ENGINE DESIGN

I. Reciprocating
(a) Single Cylinder (b) Multi-cylinder
i. ii. iii. iv. v.

In-line H, U,V,W & X Radial Opposed Cylinder Opposed Piston

II. Rotary (a) Single Rotor (b) Multi-rotor

Classification of IC Engines
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Position & Number of Cylinders

Classification of IC Engines
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a.

Single Cylinder
-

Engine has one cylinder and piston connected to the crankshaft.

b.

In line
-

Cylinders are positioned in a straight line, one behind the other along the length of the crankshaft. They can consist of 2 to 11 cylinders or possibly more. In-line four cylinder engines are very common for automobile and other applications. In-line engines are sometimes called straight. (e.g. Straight six or straight eight).

Classification of IC Engines
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c. V Engine
- Two banks of cylinders at an angle with each other along a single crankshaft.
- The angle between the banks of cylinders can be anywhere from 15 to 120, with 60-90 being common. V engines have even numbers of cylinders from 2 to 20 or more.

Classification of IC Engines
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d.

Opposed Cylinder Engine

-

Two banks of cylinders opposite each other on a single crankshaft (a V engine with a 180V). These are common on small aircraft and some automobiles with an even number of cylinders from two to eight or more. These engines are often called flat engines (e.g., flat four).

Classification of IC Engines
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e. W Engine
-

Same as a V engine except with three banks of cylinders on the same crankshaft. Not common, but some have been developed for racing automobiles, both modern and historic. Usually 12 cylinders with about a 60 angle between each bank.

Classification of IC Engines
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f. Opposed Piston Engine - Two pistons in each cylinder with the combustion
chamber in the center between the pistons.

A single-combustion process causes two power strokes at the same time, with each piston being pushed away from the center and delivering power to a separate crankshaft at each end of the cylinder. - Engine output is either on two rotating crankshafts or on one crankshaft incorporating complex mechanical linkage.

Classification of IC Engines
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g. Radial Engine - Engine with pistons positioned in a circular plane around the central crankshaft. - The connecting rods of the pistons are connected to a master rod which, in turn, is connected to the crankshaft. - A bank of cylinders on a radial engine always has an odd number of cylinders ranging from 3 to 13 or more.

Classification of IC Engines
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Radial Engine

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Classification of IC Engines
Wankel (Rotary Piston Engine)

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Classification of IC Engines
3. OPERATING CYCLE

Otto (For the Conventional SI Engine) Atkinson (For Complete Expansion SI Engine) Miller (For Early or Late Inlet Valve Closing type SI Engine) Diesel (For the Ideal Diesel Engine) Dual (For the Actual Diesel Engine)

Classification of IC Engines
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4. METHOD OF INCREASING INLET PRESSURE (POWER BOOSTING)

1.

Naturally Aspired No intake air pressure boost system

2.

Supercharger
Intake air pressure increased with the compressor driven off of the engine crankshaft.

Classification of IC Engines
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3.

Turbocharged
- Intake air pressure increased with the turbine-compressor driven by the engine exhaust gases.

Classification of IC Engines
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4.

Crankcase Compressed
-

Two Stroke cycle engine which uses the crankcase as the intake air compressor. Limited development work has also been done on design and construction of four stroke cycle engines with crankcase compression.

Classification of IC Engines
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5. VALVE/PORT DESIGN AND LOCATION Design

1. 2. 3. 4. Poppet Valve Rotary Valve Reed Valve Piston Controlled Porting

Location
1. 2. 3. 4. The T-head The L-head The F-head The I-head: (i) Over head Valve (OHV) (ii) Over head Cam (OHC)

Classification of IC Engines
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According to the arrangement of the intake and exhaust valves, whether the valves are located in the cylinder head or cylinder block.

L-HEAD
The intake and the exhaust valves are both located on the same side of the piston and cylinder. The valve operating mechanism is located directly below the valves, and one camshaft actuates both the intake and the exhaust valves

Classification of IC Engines
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I-HEAD The intake and the exhaust valves are both mounted in a cylinder head directly above the cylinder.

This arrangement requires a tappet, a pushrod, and a rocker arm above the cylinder to reverse the direction of valve movement. Although this configuration is the most popular for current gasoline and diesel engines. It was rapidly overhead camshaft. superseded by the

Classification of IC Engines
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F-HEAD
The intake valves are normally located in the head, while the exhaust valves are located in the engine block. The intake valves in the head are actuated from the camshaft through tappets, pushrods, and rocker arms. The exhaust valves are actuated directly by tappets on the camshaft.

Classification of IC Engines
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T-HEAD-

The intake and the exhaust valves are located on opposite sides of the cylinder in the engine block, each requires their own camshaft.

Classification of IC Engines
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6. FUEL
1.Conventional
(a) Crude oil derived (i) Petrol (ii) Diesel

3. Blending 4. Dual fueling

2. Alternate
(b) Bio-mass Derived (i) (ii) (iii) (iv) Alcohols (methyl and ethyl) Vegetable oils Producer gas and biogas Hydrogen

Classification of IC Engines
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7. MIXTURE PREPARATION
1. 2.

Carburetion Fuel Injection

(i) Diesel (ii) Gasoline (a) Manifold (b) Port (c) Cylinder

Classification of IC Engines
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8. BASED ON TYPE OF IGNITION

1.

Spark Ignition (SI)

The engine starts the combustion process in each cycle by use of a spark plug.

2.

Compression Ignition (CI)

The combustion process in a CI engine starts when the air-fuel mixture selfignites due to high temperature in the combustion chamber caused by high compression.

Classification of IC Engines
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9. BASED ON ENGINE CYCLE

1.

Four-Stroke Cycle A four-stroke cycle experiences four piston movements over two engine revolutions of each cycle Two-Stroke Cycle

2.

A two-stroke cycle has two piston movements over one revolution for each cycle

Classification of IC Engines
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10.
1.

METHOD OF LOAD CONTROL

Throttling

2.

To keep mixture strength constant Also called Charge Control Used in the Carbureted SI Engine Fuel Control

3.
-

To vary the mixture strength according to load, used in the CI Engine Combination Used in the Fuel-injected SI Engine.

Classification of IC Engines
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11. COOLING
1.

Direct Air-cooling Indirect Air-cooling (Liquid Cooling) Low Heat Rejection (Semi-adiabatic) engine.

2.

3.

Basic Engine Componenets

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Major Engine Parts

Cylinder Block Cylinder Head Crankshaft Camshaft Timing Chain Bearing shell Oil pump Water pump Fly wheel

Valves Valve Springs Pistons Connecting Rod Piston Ring Cylinder sleeve Inlet manifold Exhaust manifold Rocker Arm

Basic Engine Componenets

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IC Engine construction
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Engine construction can be broken down into two categories:Stationary parts and Moving parts Stationary parts
The stationary parts of an engine include
o o o o

Cylinder block, Cylinders, Cylinder head or heads, Crankcase, and the exhaust and intake manifolds.

These parts furnish the framework of the engine. All movable parts are attached to or fitted into this framework.

Stationary part
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Cylinder Block

Backbone of the engine. Supports / aligns most other components. Contains: Cylinders Coolant passages Oil passages Bearings One-piece, gray cast iron

Stationary part
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Cylinders

Cylindrical holes in which the pistons reciprocate. May be: Enblock Liners

Wet liners Dry liners

Cylinder bore diameter of cylinder

Stationary part
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Cylinder Head

Seals the top-end of the combustion chamber. Head bolts and head gasket ensure air-tight seal of the combustion chamber. Contains the valves and the intake and exhaust ports. Contains oil and coolant passages. One piece castings of iron alloy

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Stationary part
Crankcase

The crankcase is that part of the engine block below the cylinders. It supports and encloses the crankshaft and provides a reservoir for the lubricating oil Contains a place starting motor for mounting the oil pump, oil filter,

The lower part of the crankcase is the OIL PAN, which is bolted at the bottom. Is used as a reservoir for collecting and holding lube oil

Moving Components
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Moving parts contains three groups according to their motion

Reciprocating only (pistons and valves) Reciprocation & rotary (connecting rods) Rotary only (crankshafts and camshafts)

Moving Components
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Piston

Forms the moveable bottom of the combustion chamber. Lightweight but strong/durable

Piston Rings Oil ring and air ring Transfer heat from piston to cylinder Seal cylinder & distribute lube oil Piston Pin Pivot point connecting piston to connecting rod

Moving Components
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Connecting Rod

Connects the piston to the crankshaft Converts reciprocating piston motion to rotary motion at the crankshaft. Drop-forged steel

Moving Components
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Crankshaft

Works with connecting rod to change reciprocating motion of the piston to rotary motion Transmits mechanical energy from the engine to drives camshafts, generator, pumps, etc. Made of heat-treated steel alloys.

Moving Components
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Flywheel

Rotating mass with a large moment of inertia connected to the crankshaft of the engine. The purpose of the flywheel is to store energy and furnish a large angular momentum that keeps the engine rotating between power strokes and smoothes out engine operation.

Moving Components
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Valve Train

Controls flow into and out of the combustion chamber.

Time and Duration

Components (for OHV) Camshaft Valve tappets Push rods Rocker arm Valves Valve springs Valve rotators Valve seats

Moving Components
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Camshaft & Cams

Used to time the addition of intake and exhaust valves Operates valves via pushrods & rocker arms

Driven by gear (or chain) from the crankshaft. 2:1 crankshaft to camshaft gear ratio.
Lift Nose

Base circle

Cam Profile

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Moving Components
Valves

Each cylinder will have: Intake: open to admit air to cylinder (with fuel in Otto cycle) Exhaust: open to allow gases to be rejected Valve nomenclature Head Margin Face Tulip Stem

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ENGINE NOMENCLATURE

Engine Nomenclature
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Cylinder Bore (B)

The inside diameter of the cylinder, and is measured in mm. The area of circle diameter equal to the cylinder bore The linear distance, measured parallel to the axis of the cylinder, between the extreme upper and lower positions of the piston , measured in mm.

Piston Area (A)

Stroke (S)

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Engine Nomenclature
Dead Centers

The potion of the working piston at the moment when the direction of piston motion reversed at either end of the stock

Top Dead Center (TDC) or Inner Dead Center (IDC) -:

when the piston is a farthest distance from the crankshaft

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Engine Nomenclature

Bottom Dead Center (BDC) or Outer Dead Center (ODC):- when the piston is
nearest to the crankshaft

Displacement Volume (Vd)

The nominal volume swept by the working piston when traveling from one dead center to the other

Vd = A L= /4(B2L)

Engine Nomenclature
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Clearance Volume (Vc)

The nominal volume of the combustion chamber above the piston when it is at TDC is the clearance volume. It is the ratio of the total cylinder volume when the piston is at the BDC, VT , to the clearance volume vc
VT VC + VS = VC VC V =1 + s V C

Compression Ratio (r)

r=