TOPIC 1
lNTERNAL COMBUSTlON ENGlNE
The engine is a mechanial arrangement which converts chemical energy into mechanigal energy.
The chemigal energy is contained in the fuel that is supplied to the engine, and is released in the form of heat as the fuel is burnt within the engine; this is referred to as combustion.
The resulting gases become very hot and so reach a very high pressure within the cylinders of the engine. It is this high pressure that is used to force the piston down the cylinder to operate the engine.
Most automotive engines have a number of gylinders. A small car engine might have as few as two, while a large truck engine might have as many as twelve Similar actions take place in all cylinders. ”Internal” means inside, “combustion” is the act of burning.
The internal combustion engine burns fuel internally. The engine is basically a container in which fuel and air is plaged. The fuel/air mixture is ignited and burnt. As the mixture burns it expands rapidly and pushes an internal component to give drive to the machine.
Basic Elements Of an Engine
Action within the cylinderThe basic part of an engine are the cylinder, the piston, the connegting rod, and crankshaft. The piston commonly casting from aluminium alloy, is a sliding fit in the cylinder. It carries piston rings which provide a gas tight seal against the gylinder walls.
To summarize, the internal combustion engine is a device which converts heat energy into mechanical energy to do work.
Compression. The piston is being pushed into the cylinder to compress the air fuel mixture or the air. The mixture consists of tiny particles of fuel (petrol), each surrounded by air. This forms a combustible mixture.
The piston is being pushed into the cylinder to compress the air and the air temperature will increase dramatically, it will be able to burnt fuel (solar).
Compression
Combustion. The piston has been pushed almost to the top of the cylinder and the air fuel mixture or the air has been compressed into a small space. This space is referred to as the combustion chamber because this is where the burning of the mixture takes place. The air fuel mixture is ignited.by a spark at the spark plug. The hot air is injected fuel (solar) by Injector to favor fuel into the combustion chamber
Combustion.
Power. The pressure of the burning gases forces the piston down the cylinder, and this action provides the power to operate the engine.
Power
These actions occur within the cylinder of a petrol engine. A mixture of air and fuel or the air enters the cylinder and the piston moves upwards to compress it; the compressed mixture is ignited in the combustion chamber and the piston is forged downwards. These actions are repeated over and over to enable the engine to operate, although.many more parts are needed to make a complete engine.
The connecting rod and crankshaft change reciprocating motion to rotary motion.
Reciprocating to rotary motion
The up and - down movement of the piston in its cylinder is called reciprocating motion, and for this reason, piston engines are sometimes referred to as reciprocating engines.
The piston has straight line motion and this must be changed to rotary or turning motion so that parts of the engine will rotate. A connecting rod and crankshaft are used for this purpose.
The connecting rod connects the piston to the crankshaft. The crankshaft is a 'cranked' or bent shaft, with a crank for each cylinder. Each crank has a crank pin which provides a surface for the bearing in the lower end of the connecting rod. This allows the crankshaft to rotate freely within the end of the connecting rod.
The connecting rod is made with a removable cap, which is bolted to the end of the connecting rod. This is needed so that the connecting rod can be installed on the crank pin.
Arrangement of piston, connecting rod and crankshaft.
The piston is held to the upper end of the connecting rod by the piston pin. This passes through an eye in the connecting rod and allows a wrist - like action to take place as the crankshaft rotates and the piston moves up and down.The parts of a piston, connecting rod and crankshaft are shown assembled and dismantled in figure below
Part of a crankshaft, and a piston and connecting-rod assembly.
Piston Strokes
The actions of a piston in a cylinder are divided into strokes. A stroke occurs when the piston moves either from the top to the bottom of the cylinder, or from the bottom to the top of the cylinder.
The top of the piston stroke is known as top dead center (TDC), and the bottom of the stroke as bottom dead center (BDC). At each of these positions, the piston virtually stops and changes its direction of travel.
Piston Strocke Positions
It can be seen then that :An internal combustion engine is a device which converts chemical energy contained in the fuel, to heat energy by the process of combustion, to mechanical energy.
It is called on internal combustion engine because the combustion, or burning of the fuel takes place inside the engine, within the cylinders.
The operation of the pistons, connecting rods and crankshaft is the means by which the heat energy, generated by burning of fuel, is converted to mechanical energy.
These same parts also change reciprocating motion, that is up and down, or backwards and forwards, into rotary motion, or spinning
Engines are named by the fuel which they burn, petrol or diesel, and the number of piston strokes which make up a full cycle, two or four.
Written Activity #2
Answer all of the following questions.
1. What is the purpose of an engine?
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2. Why do we call petrol and diesel engines "internal combustion" engines?
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3. "Internal" means what?
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4. "Combustion" means what?
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5. Name the points in the following diagram
6. What do you call straight line, or up and down motion?
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7. What do you circular or spinning motion ?
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8. What are the main parts of an engine which changes straight line movement into spinning movement.
1. -------------
2. ------------------
9. What do you call the movement of a piston from the top of a cylinder to the bottom of the cylinder?
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10. What do the letters T.D.C. and B.D.C stand for ?
1. --------------------------------------------
2. --------------------------------------------
TOPIC2
ENGINE CYCLES
Cycles of Engine Operation
A cycle is a series of events that repeats itself over and over. Engines have an operating cycle and each cycle consists of a number of piston strokes. In four-stroke engines, the cycle has four piston strokes, but in two-stroke engines, only two piston strokes are needed for a cycle.
Most automotive engines are four-stroke engines, although some large diesel engines operate on the two-stroke principle. Some small engines, such as those fitted to lawn motor, are two-stroke, while others are four-strokes. Some motor cycles have four-stroke engines, most small bikes have two- stroke engines.
The complete cycle for an engine, whether it is a two-stroke or a four-stroke, requires an air fuel mixture to be taken into the cylinder with the certain ration number is state as AFR ( Air Fuel Ration), combustion to take place, burning gases to expand and apply force to the piston, and finally, the remains of the burnt gases to be exhausted from the cylinder
Four Stroke Cycle
For a four-stroke cycle, also known as the otto cycle after its inventor, the engine has valves in the cylinder head at the top of the cylinder. These are opened and closed at the correct times by the actions of the cams on the camshaft. The valves admit the fuel mixture and exhaust the burnt gases.
Petrol Engine
The diagrams is showed the sequence of the four strokes of a petrol engine. These are :
Intake stroke. The intake stroke commences at TDC (Top Dead Center). The intake valve is open.
and the exhaust valve is closed. The piston moves downwards to draw a charge of air-fuel mixture into the cylinder through the open intake port. The mixture of air and vaporized fuel is provided by the carburetor or the fuel injection system. (The air-fuel mixture is not actually drawn into the cylinder. As the piston moves downwards, it creates a partial vacuum, and atmospheric pressure forces the mixture into the cylinder)
Intake
Compression stroke. When the piston reaches BDC (Bottom Dead Center) and begins to move upwards on the compression stroke, the intake valve closes. The exhaust valve is already closed, so that the air-fuel charge in the cylinder is compressed as the piston moves up the cylinder. By the time the piston reaches TDC, the mixture will be compressed to about one-eighth of its original volume and also state as a compression ration (1:8). The pressure in the cylinder will also have increased.
Compression
Power stroke. Both valves remain closed during the power stroke. As the piston reaches TDC at the end of the compression stroke, the ignition system produces a spark at the spark plug. The spark ignites the air-fuel mixture which burns very rapidly to produce gases at high pressure in the cylinder. The expanding gases force the piston down the cylinder on the power stroke. The force is transferred through the connecting rod to the crank pin, causing the crankshaft to rotateNOTE : When the Ignition system may apply, it will be explained separately.
Power
Exhaust stroke. As the piston again reaches BDC, the exhaust valve opens but the intake valve remains closed. The piston moves up-wards on the exhaust stroke to force the burnt gases out of the cylinder through the exhaust port. When the piston reaches TDC, the exhaust stroke is completed and so is the cycle.
Exhaust
The above strokes constitute a four-stroke cycle. When the piston reaches TDC on the exhaust stroke, the intake valve will again open to commence the cycle all over again. This will continue as long as the engine is running.Diesel Engine
Most diesel engines are four-stroke engines, but there are some large truck engines which are two- stroke. These operate in a different way to small two-stroke petrol engines.
A diesel engine injects fuel directly into the cylinder. It does not have a carburetor or electronic fuel injection like a petrol engine to supply an air-fuel mixture.
In a diesel, air only is taken into the engine during the intake stroke. During the compression stroke.
the air is compressed to about 6000C, and this is hot enough to ignite the fuel as it is sprayed into the combustion chamber. If does not need a spark plug to fire the charge.
The four strokes of diesel engine are shown in figure below. These are
Air intake (down stroke). The intake valve is open and air is being drawn into the cylinder as the piston moves downwards at BDC, the cylinder will be full of air.
Air Intake
Compression (upstroke). Both valves are closed and air is being compressed in the cylinder. By the time the piston reaches TDC, the air will be compressed to about one-sixteenth of its original volume, and will be hot enough to ignite the diesel fuel that will be injected into it.
Compression.
Power (down stroke). Just before the piston reaches TDC, a small quantity of fuel is sprayed through the injector at the top of the cylinder into the combustion chamber. The hot air in the combustion chamber not only forms a combustible mixture with the fuel, but also ignites it. Pressure resulting from combustion forces the piston down the cylinder on the power stroke.
Power
Exhaust (upstroke). The exhaust valve is opened towards BDC of the previous stroke. As the piston moves upwards on the exhaust stroke, it forces the exhaust gases from the cylinder through the open exhaust port.Diesel engines are fitted with a fuel injection pump which delivers fuel at high pressure to the injector situated in the cylinder head. The amount of fuel can be varied and the speed of the engine controlled in this way
Exhaust.
Diesel engines are often classed as compression- ignition engines because the fuel is ignited by the heat of compression; however, the name 'diesel' is the one most commonly used.
Two Stroke Cycle.
Petrol Engine
The common arrangement for a two-stroke engine is the three-port cylinder, which is used mainly in small single-cylinder petrol engines.
The three ports in the cylinder are:
the intake port, which admits the air-fuel mixture from the carburetor; the exhaust port, which exhausts the burnt gases the transfer port, which transfers the air-fuel mixture from the crankcase to the cylinder.
The ports are opened and closed (exposed or covered) by the piston as it moves up and down the cylinder there are no separate valves.
The four parts of the operating cycle of an engine (intake, compression, power and exhaust) still occur. Some events take place in the cylinder above the piston, while others take place in the crankcase below the piston at the same time. This enables the complete operating cycle to occur during two piston strokes - one upstroke and one down stroke.
The crankcase in sealed and forms part of the fuel intake system. A petrol and oil mixture is usually used. As well as providing the air-fuel mixture for combustion, this also provides lubrication for the piston and bearings. There is no oil in the crankcase, or sump, as in a four stroke engine.
Events that occur above the piston are combustion of the air-fuel mixture for the power stroke, the exhaust stroke, and the compression stroke.
Events that occur below the piston are the intake of the fuel mixture into the crankcase, and the transfer of the fuel mixture from the crankcase through the transfer port to the cylinder.
Two - Stroke Operation.
Operation of a two-stroke engine.
The operation (events) are as follow figurePiston upstroke. The upward movement of the piston compresses the fuel mixture in the cylinder above the piston. At the same time, it creates a low pressure in the crankcase ready for the intake port to be opened. (The volume of the cylinder is reduced and so the pressure is increased; the volume of the crankcase is increased and so the pressure is reduced).
Top of the stroke. Combustion occurs near the top of the stroke and so the power stroke commences. The piston has opened the intake port on its way up the cylinder to allow the fuel mixture into the crankcase, which has a low pressure.
Operation of a two-stroke engine.
Piston down stroke. The piston is forced down on the power stroke. Near the end of the stroke, the piston opens the exhaust port to allow the burnt gases in the top of the cylinder to escape
At the same time, the pistons downward movement has decreased the volume of the crankcase compressing the air-fuel mixture in the crankcase ready for transfer.
Bottom of the stroke. Also near the bottom of the stroke, movement of the piston opens the transfer port. This allows the compressed fuel charge to transfer from the crankcase below the piston to the cylinder above the piston. The exhaust port opens before the transfer port, so most of the exhaust gases will have escaped before the transfer port opens to admit the fresh charge.
NOTE:
The parts are described as being opened and closed, but in effect. They are covered and uncovered. Remember there are no valves to open and close as in a four stroke engine.
The piston is often designed with a deflector on its head which directs the intake mixture upwards and the exhaust gases downwards towards the exhaust port. This prevents the incoming mixture from escaping through the exhaust port and also assists in blowing out the exhaust gases. This is known as scavenging.
Two Stroke Engine with Reed Valve
Two-stroke engine with reed valve: 1 exhaust port, 2 transfer port, 3 transfer passage, 4 crankcase,
5 intake from carburettor, 6 cover, 7 reed valve
When the piston is moving upwards, a partial vacuum (a pressure below atmospheric) is produced in the crankcase, and the air-fuel mixture from the carburetor (which is close to atmospheric pressure) lifts the reed valve off its port to enter the crankcase as shown in figure.
After the piston reaches TDC and commences to move downwards on the power stroke, pressure develops in the crankcase and forces the reed valve closed. Further downward movement of the piston compresses the trapped air-fuel mixture in the crankcase.
When the piston nears the bottom of its stroke, it uncovers the transfer port. The pressure which has built up in the crankcase then forces the mixture through the transfer passage into the cylinder above the piston as shown in figure.
The cylinder shown operates in the horizontal position. The crankcase is fitted with a cover, which forms a chamber between it and the crankcase. The carburetor is attached to the cover and the air-fuel mixture passes from the carburetor into this chamber.
The reed valve is located between the chamber and the crankcase. In engines with more than one cylinder, the section of the crankcase for each cylinder is sealed separately and fitted with a reed valve, which admits fuel to that particular part of the crankcase when required.
Diesel Engines
Some two-stroke diesel engines have ports for both intake and exhaust, but one of the most commonly used designs has intake ports and exhaust valves. This arrangement is shown in figure below. The piston in the diagram is almost at TDC on the compression stroke, where fuel is being injected into the combustion chamber and combustion is commencing.
The engine does not depend on crankcase compression and a transfer port, but uses a blower to force air into the cylinder through an intake port. The exhaust gases leave the cylinder through and exhaust valve.
Basic two-store diesel engine
Rotary Engine
The rotary engine uses a rotor in a housing instead of a piston in a cylinder. The rotary motion of the rotor is transferred to an eccentric shaft which performs the same function as the crankshaft in a piston engine.
Shows the action of the rotor in its housing and demonstrates the four strokes which occur in the working cylinder. These are semilar to the four strokes in a four stroke piston engine but they are performed in a working chamber formed between the rotor and its housing.
The four strokes shown in sequence in the figure are intake, compression, expansion (or power) and exhaust. There are no valves in the engine. The air-fuel mixture enters through an inlet port in the side of the housing, and the exhaust gases are discharged through an exhaust port in the housing. The rotor covers and uncovers the ports as it rotates.
The sequence shown occurs three times during each rotation of the rotor - once in each of the three working chambers.
Written Activity #2
Answer all of the following questions
1. What is a cycle of operation?
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2. Name the four strokes of a four stroke engine cycle.
1. ------------------------------------
2. ------------------------------------
3. ------------------------------------
4. ------------------------------------
3. Which types of valves will a petrol I/C engine have?
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4. Which valves are open on the following strokes of a four stroke engine?
1. ---------------------------------------------------------------
2. ---------------------------------------------------
3. ----------------------------------------------------
4. -------------------------------------------------------------
5. Instead of valves, a two stroke engine has what?
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6. How many ports does a two stroke engine have?
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7. What are the ports of a 2 stroke called.
1. --------------------------------------------------------------
2. ---------------------------------------------------------------
3. ----------------------------------------------------
8. What are the events which occur above and below the piston in a two stroke engine?
Above: Below
1------------------ 1.-----------------
2.------------------ 2------------------
3.------------------ 3 ------------------
9. Are diesel engines two stoke, four stroke or either ?
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10. How is the fuel delivered to the cylinder of a diesel engine ?
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11. What is taken into the cylinder of a diesel engine on the intake stroke.
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12. What causes the fuel to ignite in a diesel engine ?
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13. Do the diesel engines have spark plugs ?
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14. Why are diesel engines sometimes called compression ignition engines ?
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15. Do the two - strokes diesel engine have valves ?
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Multi Cylinder Engines
A single cylinder engine operating on the four- stroke cycle provides only one power stroke for every two crankshaft revolutions. The power is not uniform throughout the stroke, but is delivered more as an impulse, with the greatest power being delivered at the start of the stroke and decreasing towards the end of the stroke. To provide a more uniform power flow and smoother operation, most automotive engine have more than one cylinder. Four, six and eight, twelve, sixteen cylinders, are commonly used.
With multi cylinder engines, the power stroke are evenly spaced, so that a four-cylinder engine has two power impulses for each crankshaft revolution (four-strokes engine). Six-cylinder engines have three power strokes for each revolution of a four- stroke engine, and in this case, the power strokes overlap to provide an even smoother flow of power.
With two-stroke, each cylinder provides a power impulse for each crankshaft revolution, so a multi cylinder engine will deliver twice as many power impulses as a similar four-stroke engine.
Arrangement of the cylinders
The arrangement of the cylinders is referred to as the engine configuration. Cylinders can be arranged in-line, as a 'V', or horizontally opposed. These arrangements are shown in figure below. These engines operate in just the same way, whatever the arrangement, whether the pistons are moving up and down or from side to side.
Engine configurations: a. four-cylinder in-line, b. six- cylinder in-line, c. v-6, d. v-8, e. four-cylinder horizontally opposed.
In-Line Engines
In line engines their cylinders arranged one behind the other an straight line. A cylinder block of a four - cylinder engine is shown in figure below.
The cylinders are usually vertical, but in some in - line engines, the cylinders are tilted at an angle to the vertical and so are referred to as slant engines
Cylinder block for a four-cylinder in-line engine.
Tilting the engine has the effect of reducing its height, and this enables it to be used in a passenger car with a lower bonnet line, or installed in a truck where the engine is mounted beneath the cab.In - line engines can also be designed as flat engines. 'Flat' is a term used with engines that have horizontal cylinders. This configuration is used for some engines that are mounted under the cab in trucks or under the floor in buses or coaches.
V - Type Engines
The cylinders of V-type engines are arranged in two banks, with half the cylinders in each bank. The cylinders in each bank are in - line, and the banks are set at an angle to each other. In many engines the angle is 900, but other angles are also used.
Cylinder block and a cylinder head for a V-type engine with eight cylinder.
Compared with an equivalent in - line engine, a V-type engine will be wider and shorter, and generally will be more rigid and will have a shorter and more rigid crankshaft.Horizontally Opposed Engines
These engines have their cylinders arranged in two horizontal banks with the crankshaft mounted between them. Because this is a flat arrangement, the term flat engine is often applied to horizontally opposed engines. An engine of this design is wider and lower than an equivalent in - line engine. It also has better natural balance because the movement of a piston in one direction is balanced by the movement of a piston in the opposite direction.
Arrangement of a horizontally oppased engine.
Engine Classifications
There are many variations in engine design, but they can be classified, or grouped, according to their main design features. The various engine classifications are:
Number of cylinders. Engine vary cosideralble in regard to the number of cylinder. Four, six and eight cylinders are the most commonly used, but there are also automotive engines with one, two, three, five and twelve cylinders.
Arrangement of the cylinders. Engines are designed with their cylinders in-line, at an angle to each other (V-type engine) or horizontally.
Engine capacity. The capacity or size of the engine is the total volume of all the cylinders of the engine. This provides a common basis for comparing the size of engines. This does not mean that all engines of the same capacity will produce exactly the same out put power, because some engines are designed for higher performance than others.
Arrangement of the valve mechanism. The common arrangements are overhead valves (OHV)) and overhead camshaft (OHC). Both these engines are actually overhead-valve engines, but they are given different names because the camshafts are located in different parts of the engine. Some engines have two camshafts and this arrangement is referred to as double overhead camshafts (DOHC). Some engines have four valves per cylinder, and this feature is sometime used to describe the engine. For example, a four- cylinder engine with four valves for each cylinder is called a sixteen - valve engine
Type of cooling. Engines can be liquid - cooled or air-cooled. Liquid-cooled engines have water- jackets and a radiator. Air-cooled engines depend on a flow of cooling air.
Operating cycle. Engines are classed by their operating cycle, either as four stroke engines or two- stroke engines.
Type of fuel used.
There are three automotive fuels : petrol, distilate (for diesel) and gas.
Other Engines
The classifications above relate to piston engines. Rotary engines are spark-ignition engine using petrol as fuel, but they are not used in motor vehicles.
Engines Systems
In addition to the actual engine components, an engine requires a number of systems to enable it to operate. Some of the engine components previously mentioned form part of these systems.
These system are as follows:
Fuel system. Includes a fuel tank and a fuel pump to supply the fuel to the engine.
Lubrication system. Uses a pump and passages to supply oil to all the moving parts of the engines.
Cooling system. Includes the radiator, hoses, water pump, water-jackets in the cylinder block and head, and also the coolant which is circulated through the system to prevent the engine from overheating.
Starting system. With a battery and a starter motor, rotates the engine by means of the ring gear on the fly wheel.
Charging system. Includes an alternator to recharge the battery.
Ignition system (in a spark-ignition engine). Provides the spark at the spark plug to ignite the mixture in the combustion chamber.
Intake system. Includes the air cleaner, ducting and intake manifold
Exhaust System.
Consist of the exhaust manifold, exhaust pipes, and muffler to convey the exhaust to the rear of the vehicle
The systems outlined above are required for all engines, except the ignition system which is not required for diesel engines. In addition to the various components and systems which have been covered, other auxilaries may be fitted to an engine, such as power-steering pumps and air- conditioning compressors. In heavier vehicles, vacuum pumps or air compressors for the breaking system.
Written Activity #2
Answer all of the following questions.
1. In a four stroke engine how many power strokes per cylinder occur for two crankshaft revolutions?
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2. What is the effect on the operation of an engine if there is more than one cylinder?
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3. At what part of the stroke is power greatest?
---------------------------------
4. In a six cylinder engine, how many power strokes are there for each revolution of the crankshaft?
---------------------------------
5. In a two-stroke engine how many power impulses per cylinder are there for each crankshaft revolution?
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6. How would you describe the engine configurations in the following diagram?
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1. ------------------------------
2. -----------------------------
3. -----------------------------
7. What are the seven features of engines which can be used to classify them?
1. ---------------------
2. ---------------------
3. --------------------
4. ---------------------
5. ----------------------
6. ---------------------
7. --------------------
8. What systems (other than the engine)are required to allow the engine to operate?
1. ---------------------------------------------------
2. --------------------------------------------------
3. ------------------------------------------------
4. ---------------------
5. ---------------------
6. -----------------------------------------------
7. ----------------------
KEY ANSWER OF WRITTEN ACTIVITY
Written Activity #2
Answer all of the following questions.
1. What is the purpose of an engine?
To converts chemical energy into the mechanical energy.
2. Why do we call petrol and diesel engines "internal combustion" engines?
Because burn the fuel internally
3. Internal" means what?
Inside
4. "Combustion" means what?
Is the act of burning
5. Name the points in the following diagram.
6. What do you call straight line, or up and down motion?
Reciprocating motion
7. What do you circular or spinning motion ?
Rotary motion
8. What are the main parts of an engine which changes straight line movement into spinning movement.
1. Connecting rod
2. Crankshaft
6. What do you call the movement of a piston from the top of a cylinder to the bottom of the cylinder?
Stroke
7. What do the letters T.D.C. and B.D.C stand for ?
1. TDC = Top Dead Centre
2. BDC = Bottom Dead Centre
Written Activity #2
Answer all of the following questions
1. What is a cycle of operation ?
a Cycle is a series of events that repeats it self over and over
2. Name the four strokes of a four stroke engine cycle.
1. Intake stroke
2. Compression stroke
3. Power stroke
4. Exhaust stroke
3. Which types of valves will a petrol IVC engine have ?
Intake valve Exhaust Valve
4. Which valves are open on the following strokes of a four stroke engine?
1. Intake stroke- intake valve open and exhaust valve closed.
2. Compression stroke - intake valve closed and exhaust valve closed
3. Power stroke- intake valve closed and exhaust valve closed
4. Exhaust stroke- intake valve closed and exhaust valve open
5. Instead of valves, a two stroke engine has what ?
PORT
6. How many ports does a two stroke engine have ?
Three port
7. What are the ports of a 2 stroke called.
1. Intake port
2. Transfer port
3. Exhaust port
8. What are the events which occur above and below the piston in a two stroke engine?
Above: Below :
1. Power stroke Intake stroke
2. Exhaust stroke transfer
3. Compression stroke
9. Are diesel engines two stoke, four stroke or either ?
both two or four stroke
10. How is the fuel delivered to the cylinder of a diesel engine ?
Fuel is sprayed through the injector into the combustion chamber
11. What is taken into the cylinder of a diesel engine on the intake stroke.
Drawn air into the cylinder
12. What causes the fuel to ignite in a diesel engine ?
Hot air
13. Do the diesel engines have spark plugs ?
No spark plugs
14. Why are diesel engines sometimes called compression ignition engines ?
Because the fuel is ignited by the heat of compression
15. Do the two - strokes diesel engine have valves ?
No valve
Written Activity #2
Answer all of the following questions.
1. In a four stroke engine how many power strokes per cylinder occur for two crankshaft revolutions?
One power stroke
2. What is the effect on the operation of an engine if there is more than one cylinder?
Smoother flow of power
3. At what part of the stroke is power greatest?
Power stroke
4. In a six cylinder engine, how many power strokes are there for each revolution of the crankshaft?
Three power stroke
5. In a two-stroke engine how many power impulses per cylinder are there for each crankshaft revolution?
One power implus
6. How would you describe the engine configurations in the following diagram?
7. What are the seven features of engines which can be used to classify them?
1. Number of cylinder
2. Arrangement of the cylinder
3. Engine capacity
4. Arrangement of the valve mechanisim
5. Type of cooling
6. Operating cycle
7. Type of fuel used.
8. What systems (other than the engine) are required to allow the engine to operate?
1. Fuel system
2. Cooling system
3. Starting system
4. Charging system
5. Ignition system
6. Intake system
7. Exhaust system
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BASIC ENGINE
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