Diesel Engine Proper 2

B. Cylinder Head

(1) Cylinder Head Structure
The cylinder head is mounted on the top of the cylinder block with head bolts. The cylinder head makes up the combustion chamber together with the cylinder and piston. Cylinder heads for water-cooled engines are manufactured by integral casting. Ordinarily they are made of cast iron.
Cylinder heads for super charged engines are made of alloy cast iron containing nickel, chrome, molybdenum etc. because of the large thermal load. (The temperature between the valves in supercharged engines is 350- 400 degree celcius while the temperature in ordinary engines is below 350"C.)

a) Intake port (duct) This connects the intake manifold and the combustion chamber as the passage for the intake air. Since the shape and inner surface finish of this passage have a large influence on intake efficiency they are important factors related to power output. The shape is designed to minimize air-flow resistance.
Swirling is specially used with direct injection type engines to promote combustion by fully mixing the fuel and intake air. The intake port plays an important role in producing swirls.

b) Exhaust port This connects the combustion chamber and the exhaust manifold as the passage for the exhaust gas. It usually has a round section on the combustion chamber side and an angular section on the manifold side.

c) Valve seat
A valve is mounted on a valve seat. A ring-shape valve insert is used for engines that operate under severe conditions, especially for diesel engines and for light alloy cylinder heads. When it wears out, it is replaced instead of replacing the cylinder head.
Valve seats are made of heat resistant steel such as special cast iron and satellite.
The shape of a valve insert is shown in the following illustration. The valve seat angle is 45 degree against the axial center in most cases, but may be 30 degree or 60 in some cases.

d) Valve gulde
A valve guide is made of special cast iron and is press fitted into the cylinder head. The valve stem slides up and down in the valve guide. The valve guide takes heat away from the valve into the cylinder head and supports the side thrust of the valve stem.

e) Water Jacket
This is the coolant passage provided to radiate the heat generated in the combustion chamber.
In addition to the above parts, a cylinder head has lubricant passages, valve spring seats, push rod holes, rocker bracket seats, cylinder head bolt holes, and rocker cover mounting.

(2) Handling of the Cylinder Head
A cylinder head will happen the following problems:

a) The bottom surface of the cylinder head does not have the correct flatness.
When mounted on the cylinder block such a cylinder head cannot maintain the necessary air tightness. This causes gas leakage and decrease the power output. Deformation of this surface must be measured using a straight edge and a thickness gauge, as with the cylinder block. In a diesel engine the bottom surface of a cast iron cylinder head is exposed to burnt gas. The Cylinder head cooling system is designed so that the temperature of the lower face (part of the combustion chamber) will be 350- 400 degree Celsius or less where it contacts the combustion frame. Since the top and the sides of the cylinder head are exposed to the outside air, there are considerable temperature differences within the cylinder head. As a result, it cannot expand uniformly and tends to deform into a concave shape in the upward direction. This produces internal stress (thermal stress) in extreme cases. Repeated occurrence of internal stress may cause fatigue and cracking. The solid lines and broken lines in the illustration on the light show how a head can be deformed when it is tightened and when it is exposed to burnt gas pressure.
The double-dot and dash lines in the illustration show how a head can be deformed by thermal expansion.

b) A cylinder head can be cracked by careless handling or by trouble in the cooling system.

c) If a valve seat is not in close contact with the cylinder head the combustion chamber will lose its air-tightness. This causes reduced the power output.

d) Solid carbon will accumulate in the combustion chambers when low quality lubricating oil is used or when the lubricating oil gets into the combustion chamber. Since solid carbon has low heat conductivity, an engines will overheat if the carbon accumulates.

C. Cylinder Head Gasket, Head Bolts

(1) Functions of Cylinder Head Gasket
A cylinder head gasket is mounted between the cylinder block and the cylinder head to prevent gas leakage between them and to prevent the entry of air from the outside.

a) It must seal openings on the cylinder block such as the cylinders, water holes and lubricant passages, and the corresponding openings on the cylinder head at the same time.

b) It should not be corroded by high temperature, High pressure burnt gas, pressurized lubricating oil, or cooling water.

c) It must have enough strength to withstand large pressure fluctuations and strong vibrations. It must withstand rapid temperature changes.

d) It must be easy to mount and dismount. It must be reusable.

(2) Handling of the Cylinder Head Gasket a) Do not carry a cylinder head gasket by both ends. It may become curved and the asbestos in the middle may be cracked.

b) Do not damage or deform the gasket. Do not store it under a heavy object. Hang gaskets on the wall in a storage area.

c) Do not immerse the gasket in liquid, because the asbestos structure will be destroyed.

d) Mount the gasket on the correct side.

(3) Cylinder Head Bolts
Cylinder head bolts are used for tightening the cylinder head and cylinder block. Generally, the cylinder head will be deformed as shown the illustration due to tightening to the block through the gasket. This is because the top end of the liners protrude above the top of the block. This raises the pressure on the sealed part around the combustion chamber. Be sure to adjust the valve clearance after re-tightening the cylinder head bolts.

Tightening and dismounting the cylinder head
When mounting a cylinder head on a cylinder block or when dismounting it, be sure to tighten (or loosen) the bolts in the correct sequence. The cylinder head can be deformed by tightening (or loosening) the bolts in the wrong sequence.
To tighten the bolts, start at the center and move out in a radial direction. To loosen the bolts, start from the outside.
Do not tighten the bolts to the specified torque all at once. Tighten them gradually step by step. Be sure to follow any instructions about tightening the cylinder head in a cold state or warm state.

Diesel Engine Proper 1

A. Cylinder, Cylinder Block
(1) Cylinder
A combustion chamber is made up of a cylinder, a cylinder head and a piston. A cylinder has a cylindrical shape and its inner surface is perfectly finished.

The piston slides up and down between top dead center and bottom dead center within the cylinder. The cylinder receives the most complicated forces in the entire engine because of the influence of the pressure and heat generated by the burnt gas.

Cylinder classification
Cylinders can be structurally classified into the following types:
1.In block cylinder : The cylinder and the cylinder block have singgle integrated structure
2.Liner type cylinder : The cylinder is inserted into separately manufactured cylinder block
(Dry liner type & Wet liner type )

In block cylinder type
The cylinder and the cylinder block are manufactured as a solid unit. Since no cylinder liner is used with an in-block cylinder, it has fewer parts than a liner type cylinder. For this reason, this type is suitable for mass production. Currently in-block cylinders are used most widely for gasoline engines with cast iron cylinder blocks.

Dry liner type
The cylinder liner housing of the cylinder block is finished into a cylindrical diameter with a fitting tolerance from the finished dimensions of the cylinder. A separately manufactured cylinder liner is inserted into this. The cylinder liner is surrounded by the walls of cylinder block, so it never comes into direct contact with the engine cooling water.

Wet liner type
The cylindrical part of the cylinder is made up entirely of the cylinder liner. The outer surface of the wet liner comes directly in contact with the cooling water.
For this reason, this type of cylinder liner can be cooled efficiently. Wet liners are easier to manufacture and assemble than dry liners.
The upper part of the cylinder liner has a flange which is used for positioning during assembly and which prevents water from leaking from the top. The lower part of the cylinder liner has a "rubber ring" to prevent water leakage. Ordinarily the liner thickness is 6 – 8% of the inner diameter of the liner.

(2) Cylinder Block

a) Cylinder block structure
A cylinder block has the following structural parts in addition to the cylinders that generate the power:
* Water jacket : The passage for the cooling water used to cool off the heat generated by the engine ( Not needed in an air-cooled engine).
* Oil gallery : Passage for oil sucked in by the oil pump.
* Crankshaft bearings : These hold the crankshaft by the bearings.
* Camshaft bearings : These hold the camshaft (Not needed for an overhead cam type cylinder block).
* Oil pan mountings, gear train mountings, etc,

The cylinder block must have enough strength to withstand the forces generated by the
explosions (combustion) within the engine and the inertia related to high speed rotation of the crankshaft. For this reason, the upper part of the cylinder block and the crankcase usually have a mono-block structure.

b) Cylinder and cylinder block materials
Cylinders must have the following properties because they are constantly exposed to the high temperature and high pressure generated by repeated combustion explosions:
a) They must have superior abrasion resistance in order to endure the reciprocating motion of the pistons.
b) They must have high melting temperature in order to withstand the hot burnt gas.
c) They must have high strength and hardness at high temperatures.
d) They must have large oil film retention strength.
Special cast iron is the most widely used material for cylinders at present. This is because cast iron has large abrasion resistance. Special cast iron contains phosphorus, nickel, chrome or molybdenum to achieve even higher abrasion resistance or copper to raise corrosion resistance.

(3) Cylinder Characteristics
a) Cylinder capacity
The highest piston position in a cylinder is called top dead center, while the lowest position is called bottom dead center. The distance that the piston moves between these two points is called the stroke and the capacity is called the cylinder capacity (displacement). This is the maximum volume of air that can be sucked in by the descent of the piston. The engine displacement of a multi cylinder engine is obtained by multiplying the cylinder capacity by the number of cylinders. It can be calculated by the following formula:

b) Compression ratio
If the air taken into a cylinder is burnt without being compressed, not enough force will be generated to operate the engine. In order to obtain sufficient rotational power, the air must be compressed to some fraction of its original volume before it is burnt, causing explosive combustion.
Air is sucked in by the descent of the piston to bottom dead center, and the air is then compressed by the ascent of the piston to top dead center. The ratio of the volume after compression to the original volume is called
the compression ratio. The compression ratio
can be obtained by the following formula:

DIESEL ENGINE PERFORMANCE

Diesel Engine Performance

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Diesel Engine Combustion Chambers and Their Characteristics

The combustion chambers of diesel engines can be structurally classified as follows.

Combustion Chamber 1. Open combustion chamber

a. Direct injection type

&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp2. Divided combustion chamber

a. Pre combustion chamber

b. Swirl chamber type

c. Air chamber type

The various types of combustion chambers which give such a large influence on engine performance are explained as follows.

(1) Direct injection Type
Direct injection type combustion chambers are illustrated on the next page. They have the Simple ststructure.

Fuel is injected into the combustion chamber between the cylinder head and the piston head,as the following illustrations show. In most cases fuel is injected at high pressure (150- 300kglcm\ using a hole nozzle (multihole nozzle) in order to burn the fuel completely.

Advantages of the direct injection type
1) Since the combustion chamber has a simple shape and relatively small surface area the heat lossis small. Therefore thermal efficiency is high and the specific fuel consumption is good (150 - 200 gr/PS-Hr). This kind of engine can start smoothly and does not require a glow plug.
2) Since this structure of ths cylinder head is simple, and trouble due to thermal strain rarely occurs.

Disadvantages of the direct injection type1) Combustion starts at a higher pressure than with other types of chamber.
2) The state of atomization has a sensitive influesce on combustion.
3) There is more noise and vibration during operation than in other types of chamber, because the combustion pressure is high.
a) The NOx (nitrogen oxides) concentration in the exhaust gas is higher than with other types of injection because the combustion temperature is high.

(2) Pre-combustion chamber typePre-combustion chamber type chambers are illustrated in the following figure. Combustion chambers of this tlpe have a pre-combustion chambers in the upper part of the main combustion chamber. Fuel is injected into the pre-combustion chamber where part of the fuel is burnt, and the remaining fuel is injected into the main combustion chamber by the pressure produced from the fuel combustion in the pre-combustion chamber. Swirling created a thorough mixture of fuel and air, which is burnt in the main combustion chamber.

Generally the volume ratio (the ratio of pre-combustion chamber volume to total compression volume) of the pre-combustion chamber is between 25% and 45%.



Advantages of the pre-combustion chamber type
1) Since the fuel is burnt in the main combustion chamber after being partially burnt in the pre-combustionc hamber, combustion is not as easily influenced by fuel quality. Diesel knock is relatively small and engine operate quietly.
2) The initial fuel injection pressure is relatively low (80 - 150 kg/cm)
and combustionis not easily influenced by the state of atomization.
3) The NOx concentration of the exhaust gas is lower than with the direct injection type.

Disadvantages of the pre combustion chamber type
1) The cylinder head structure is complicated.
2) Sincet he compressed air is throttled by a nozzle hole, the pressure increase in the pre-combustion chamber is delayed. The compression temperature in the pre-combustion chamber is lower than the direct injection type because heat is dissipated for the large area of the pre-combustion chamber. Therefore, a glow plug is needed for starting.
3) The specific fuel consumption is low.

(3) Swirl Chamber Type
The characteristic of the swirl chamber types that it has a swirl chamber on the cylinder head as illustrated in the figure below. During the compression stroke a strong swirl of air is produced in the swirl chamber. Fuel is injected into that swirl and burnt. In the pre-combution type, fuel is burnt only partially in the pre-combustion chamber, but in the swirl type, most of the fuel is burnt in the swirl chamber.

Therefore, the volume of the swirl chamber accounts for 50 - 70% of the total combustion volume. There is only one passage from the swirl chamber into the cylinder.

The characteristics of the swirl type lie somewhere between those of the direct injection type and those of the pre-combustion type.

Advantages of the swirl type1) The fuel and air are thoroughly mixed by the swirl of compressed air, so the excess air factor can be relatively low and the mean effective pressure is high.
2) Since this structure is suitable for relatively high speeds, it is advantageous from the view point of maximum output and specific fuel consumption.

Disadvantages of the swirl type
1) The structure of combustion chambers of this type is complicated because a swirl chamber must be mounted on the cylinder or cylinder head.
2) It is sensitive to the ignitability of the fuel. Diesel knock occurse asily.
3) It needs a pre-heater for starting.

DIESEL KNOCK

One of the characteristics of combustion in a diesel engine is diesel knock.
Knocking in a gasoline engine and knocking in diesel engine are the same in that they occur due to a sudden pressure increase during the combustion process. However, there are a number of fundamental differences betwen the two in terms of the timing, cause, and state of knocking.

Diesel knock occurs when the combustible gas mixture produced during the ignition lag period burns explosively and the pressure rises suddenly.

Knocking in gasoline engine occurs when self ignition occurs too easilly, but diesel knock occurs when self ignition does not occurs easilly enough. Therefore, the causes of two types of knocking are completely opposite from one another.

In gasoline engine , there is large difference between normal combustion and knocking combustion. In a diesel engine, knocking combustion is hard to distinguish during operation. Therefore, knocking is distinguished from normal combustion according to whether or not a sudden pressure increase generates a hitting noise or brings about shock to engine parts.

Because of the nature of its cause, diesel knock can be prevented by shortening the ignition lag period. Fuel injection nozzles are generally designed to lower fuel injection during the ignition lag period.

COMBUSTION IN DIESEL ENGINE

The combustion process in a diesel engine is explained in detail as follows.
Fuel particles injected rom a nozle into the cylinder in the form of high pressure mist are heated by the high temperature and high pressure air. They ignite and burn when they begin to evaporate and are mixed with hot air.

The ilustration shows this process in terms of the pressure in reference to the crank angle. The combustion process can be divided into the following 4 periods.

1. Ignition Lag period.
During the period from A to B, fuel is injected from A in mist form, heated by compressed air in the cylinder and approaches the ignition temperature. Although this period is short, and the pressure does not increase suddenly, because the length o this period heavily influences combustion, it should be as short as possible. The length of this period is influenced by the ignitability o the fuel, the compression pressure and temperature of the air, and the injection state of the fuel.

2. Flame propagation period (Explosive combustion period).
This is the period from B to C in the ilustration. At point B in the ilustration the fuel prepared for combustion during the ignition lag period ignites at one or more locations in the gas mixture. This propagates very quickly to all parts, causing nearly simultaneous combustion. Fuel injected betwen B to C burns at the same time. As a result, the pressure increases suddenly. The increase in pressure is related to the quantity and the atomized state of the fuel injected during the ignition lag period. Most of the injected fuel is completely burnt by the end pf this period (C).

3. Direct combustion period.
This is the period from C to D. Fuel injection continues after point C. Fuel injection and combustion take place simultaneously because of the flames produced betwen B and C. Therefore, the pressure change between C and D can be regulated to some extent by controlling the rate of the fuel injection.

4. Post-combustion period.
Injection ends at point D in the illustration and the burnt gas expands. Any fuel that has not burnt completely burns during this period of expansion. The period after point D is called the post-combustion period.

If this period is too long, the exhaust temperature becomes too high and the thermal efficiency is lowered. Therefore, this period must be short. Combustion during this period is heavily influenced by the size and distribution of the fuel particles and their contact with the air.

Thus, combustion can be divided into four periods. The ignition lag period and the flame propagation period can be regarded as a preparatory period for the direct combustion period ; the quality of these periods gives a large influence on combustion.

Therefore, the initial injection pressure of the nozzle, the state of atomization, the compression pressure and the injection timing are important maintenance items for diesel engines.

Valve Timing In a 4- Cycle Engine

The Discharge of the combustion gas from the cylinder and the intake of fresh air are closely related to the combustion of the fuel, and therefore to the engine output.

It is desirable to maintain a high intake efficiency (volume effeciency) through out the intire range of engine speed. Intake eficiency (volume efficiency) ; The amount of air that is actually. sucked in by an engine can never be 100 percent o the stroke volume. The ratio of the actual amount of air intake to the sroke volume is called intake efficiency. However, when timing that results in high intake efficiency in the high speed range is used, intake eficiency decreases in the low speed range. And when timing that is good in the low speed is used, efficiency tends to be poor in the high speed range. Therefore the timing is determined through consideration of the operating conditions of the engine. Some engine has Variable Valve Timing (VVT) to prevent this.

Generally, the inlet valve and the exhaust valve open early and close with some delay in relation to the top dead center and bottom dead center of the piston, as ilustrated in the valve timing diagram.

The valve timing is explained as follows.

1. Advance opening angle of the inlet valve.
The opening area of inlet valve is very small at the moment the valve leaves the seat. If the inlet valve were to begin to open at top dead center. the opening area would not be sufficiently large when the piston began to go down. The intake efficiency would be low because the intake resistance would be high. Therefore, as shown in the figure the inlet valve is opened slightly earlier than that so that the intake area will be large enough when the piston begins to move down and the piston speed increases.
The advance opening angle of inlet valve depends on the caracteristics of the engine, but it is generally betwen 15 degree and 30 degree before top dead center.

2. Delayed Closure angle of the inlet valve.
Even when the piston has reached bottom dead center during the intake stroke, the air pressure in the cylinder is still lower than atmospheric pressure because of intake resistance. Air will flow into the cylinder as long as the air pressure in the cylinder is lower than the pressure inside intake manifold. Therefore, air intake can be increased by delaying closure of the inlet valve until after the piston reaches the bottom dead center. This delay angle is related to the rotational speed and the cam shape. It is advantageous for the delayed closure angle to be small in the low speed range, but a large angle is advantageous in the high speed range. However, some of the intake air will be discharged if the delay is too large. Therefore, the delayed closure angle is generally betwen 40 degree and 60 degree after botton dead center.

3. Advance opening angle of the exhaust valve.
In the combustion stroke, the combustion pressure could theoritically be used most effectively by keeping the exhaust valve closed until the piston reaches bottom dead center. However because of the resistance of the exhaust gas pressure (back pressure), after the piston passes bottom dead center (after the exhaust stroke begins), the pump loss of the piston increases. Therefore, it is advantageous to open the exhaust valve early to decrease the back pressure. For this reason, the exhaust valve is given a suitable advance opening angle. This angle depends on the characteristic of the engine, but it is generally betwen 40 degree and 60 degree before bottom dead center.

4. Delayed clossure angle of the exhaust valve.
The inlet valve and the exhaust valve are both open for some period of time when the piston is near top dead center, because ofthe advance opening angle of the inlet valve and the delayed closure angle of the exhaust valve. This is called Valve Overlap. In this state, because of the inertia of the intake air and exhaust gas, air can be cusked in and the remaining exhaust gas can be discharged. Therefore, the exhaust gas can be replaced by fresh air. Generally, the delayed closure angle of the exhaust valve is between 15 degree and 30 degree after top dead center

During engine operation if a valve hits the rocker arm due to thermal expansion, the valve timing will be disturbed. Valve clearence is provided to prevent this. Excessively large or small valve clearence will upset the valve timing.

OPERATING PRINCIPLE OF 4-CYCLE DIESEL ENGINE

1. Intake Stroke
During the intake stroke the exhaust valve are closed and only the inlet valve is open. As the piston moves down from the top dead center (TDC), air sucked in from the inlet manifold through the inlet valve.

2. Compression Stroke
When the intake stroke ends, piston begins to move upward again from bottom dead center (BDC). The inlet valve closes and air flow stop. The air in the cylinder is compressed as the piston moves up. As the air is compressed, its temperature rises as well as its pressure. Since a diesel engine burns fuel using the compression heat of air, the air must be compressed until its temperature reaches at least the self ignition temperature of the fuel.
The ignition temperature of the fuel decreases the higher the air pressure becomes. Theoritically, the compression pressure is determined by the compression ratio, so it is not directly related to the rotational speed. in reality, the compression pressure depend depends on various condition, such as rotational speed and leakage from the clearence betwen the piston and the cylinder. The compression pressure is heavily dependent on rotational speed in the low speed range, but not in the high speed range.

3. Combustion Stroke
Near the end of the compression stroke, fuel is injected from a nozzle in the form of high pressure mist. The compression heat of the air makes the fuel self ignite and burn. As a result, the pressure in the cylinder rises suddenly and the piston is pushed down. This force becomes the power that generates a turning force (torque) on the crankshaft.

4. Exhaust Stroke
When combustion ends and piston approaches bottom dead center, the exhaust valve opens. The combustion gas, which added work to the piston during the combustion stroke, is discharged into the atmosphere from the exhaust valve by the ascent of the piston. When the piston reaches top dead center, the intake stroke begins again and the same cycle is repeated.
An engine with a cycle consisting o these 4 strokes is called a 4- cycle engine

OUTLINE OF DIESEL ENGINE II

(5) Classification by Cooling Method
1) Water Cooled type
This cooling method is used for ordinary automobile
2) Air-Cooled type
This cooling method is used for motor bicycles and some small cars.

(6) Classification by Valve Type
1) Side valve type (SV type)
The Valves are located on the side of cylinder. This design is not used for high speed diesel engines.
2) Overhead valve type (OHV type)
The valve are located on the top of the cyliner, that is, on the cylinder head. This design is used or high-speed diesel engines.
3) Overhead camshaft (OHC type)
Both the valve and the camshaft are located on the cylinder head.

(7) Classification by Number and Arrangement of Cylinders
Engines are classified both by number of cylinders and by the arrangement of cylinders :
1) In- Line (Straight) type
2) Horizontal type
3) Horizontal opposed type
4) V type
As the number of cylinders increases, the rotational force (torque) of the engines becomes more balanced, and the high and low limit on the speed of the engine are extended. As a result the range of the enginen speed can be enlarged. It is widely known that a multi engine cylinder generates less vibration than a single cylinder engine.

1) In-Line type
The cylinders are arranged in a straight line. This type of engine encounters dimensional limits when attempting to produce a large output by increasing the number of cylinders. However, these engines are easy to maintain and their production cost is relatively low.

2) Horizontal type
The cylinders are arranged horizontally in this kind of engine. The engine height can be decreased using this design. For example, the engine may be mounted under the floor of a bus to increase the passenger room area.

3) Horizontal opposed area

The cylinders are arranged so that they are opposed in the horizontal direction. This type o engine has a larger capacity and produces a higher output than the horizontal type. In Japan, these have been used as underfloor engines in high-speed buses. However, the engines is rarely manufactured now because of its high manufacturing cost and large weight. This type is superior to then in-line type and the horizontal type from the viewpoint of engine balance.

4) V type
As the capacity of an in-line engine is increased, physical restrictions (length and weight) arise. This is why V-type engine are used for large capacity engines. The boundary betwen the in-line type and the V-type seems to be a displacement of about 13 - 14 l. Selection betwen the two types is made based on consideration of their relative advantages and disadvantages.
Basically, a V-type engine is structurally the same as in-line type engine. However, the cylinder block manufacturing cost tends to be height.
V6, V8, V10 and V12 types are used. The V8 type is used most widely.
The angle of V shape is generally 90 degree V, which is the best angle for obtaining equal interval ignition.

OUTLINE OF DIESEL ENGINE

I. Engine Classifications
A diesel engine is a type of internal combustion engine, which is in turn a type of combustion engine. A combustion engine changes thermal energy generated by fuel combustion into mechanical work. Combustion engine can be classified into internal combustion engines and external combustion engines. Internal combustion engines can be classified into Reciprocating type (Diesel and Gasoline Engine) and Rotational Motion type (Gas Turbine and Rotary Engine).

II. Classification of Reciprocating Internal Combustion Engines

(1) Classification by Ignition Method
1) Spark ignition engine.
2) Compression ignition engine
Air is heated (450 - 550C) by compression and fuel injected into the compressed air in the form of high pressure atomized fuel. The atomized fuel is ignited and burnt by the compression heat of the air. Diesel engines belong this group.
3) Hot-bulb ignition engine.

(2) Classification by Combustion Method (Thermodynamic Classification)
1) Otto cycle (Constant volume cycle)
Combustion take place under constant volume. Gasoline engines belong this group.

2) Diesel cycle (Constant pressure cycle)
Combustion takes place under a constant pressure. This combustion method is called the diesel cycle because the first engine built by Rudolf Diesel, the inventor of the diesel engine, was an engine that operated by constant pressure combustion. However, current-day high-speed diesel engines (for automobiles) do not belong this category.

3) Sabathe cycle (Mixed cycle)
In the Sabathe cycle, the above two cycles are combined. In other words, combustion takes place under constant volume and constant pressure. Current high-speed diesel engines (for auto mobiles, general power units and small boats) belong this category.

(3) Classification by Fuel Type and Fuel Method

Fuels used for internal combustion engines can be broadly classified into the following types :
1) Gasoline, 2) Kerosene, 3) Light Oil, 4) Heavy Oil, 5) Liquefied-petroleum gas (LPG).
Fuel feed methods can be classified as follows :
1) Fuel is charged into the engine together with air, using carburetor.
2) Fuel is injected into the cylinder (combustion chamber) using an injection pump.
Note's : On current gasoline engine is now no longer use the carburetor, fuel and air mix using injection technology (Electronic Fuel Injection). The different between diesel and gasoline injection is : Gasoline engine injected a fuel into intake manifold (before intake valve) its still mean fuel is charged into the cylinder together with air.

(4) Classification by Operation Technique
1) 4-cycle engine
One cycle (suction, compression, combustion, and exhaust) of the engine requires two rotations of the crankshaft, that is, four strokes.
2) 2-cycle engine
One cycle of the engine requires one rotation of the crankshaft.

HISTORY OF DIESEL ENGINE

In 1892, Rudolf Diesel, a German engineer, announced a new type of engine which fuel is injected into compressed air and ignited. This engine came to be known as the diesel engine.
By 1897, diesel engine that used heavy oil as fuel had been developed for practical use in Germany. (Low speed diesel engine)
Betwen 1924 and 1926, the development of the injection pump by Robert Bosch (from Germany) led to the development of high-speed diesel engines.
In Japan, research and development into diesel engines started around in 1930. By 1936, 6-cylinder air-cooled diesel engine with a total displacement of 8l had been developed and put to use.
In 1939, 5.1l-6-cylinder water-cooled automotive diesel engine began to be utilized, and diesel engine research and improvements have been continually pursued since then.



The history of diesel engines was briefly explained above. Research and development on diesel engines has been promoted in two separate areas; low-speed diesel engines for boats using heavy oil as fuel and high-speed diesel engine for automobiles such us Truck using light oil as fuel. In Japan research and develpoment on low-speed diesel engine has a longer history than hig-speed diesel engines. Low speed diesel engines have been used for boats and agricultural machinery and as power sources in industry.