Basics of internal combustion engine by BjManindarKumar

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									Objective:
This paper presents the information about the series of History & Development of the Internal Combustion Engine,
Types of Engine & Moment, Basic Main Components of Engine & Construction & Cycles, Basic Connecting Rod
Mechanism, Essential Mechanical Systems and Important Properties, functions of Lubricant Oils.


   Aim: In order to know the History and the basics of combustion engine and the important properties
   of the Lubricating oil.


Introduction:
History of the internal combustion engine
During the 19th century the steam reciprocating engine was developed. These were Crude
engines, which had poor efficiency, were unpredictable and used a lot of labour. By the late
1880s, they were widely used in transport on land and sea and in industry. The power
introduced into the engine in the form of steam, which obliges the use of a boiler and
auxiliary pumps, requiring a lot of space.
        At this time, there is an idea of power that could create within the cylinder itself. If
this achieved, it will be easy to manage without the steam power unit. Many changes made
in order to withstand the high temperatures and pressures inside the cylinder and various
fuels and blends used to bring the required power.
        At last, by 1900, all the problems cleared; which result followed by two definite lines of thought and
from these the SPARK IGNITION ENGINE and COMPRESSION IGNITION ENGINE designed.

Development of the internal combustion engine
1770 First steam carriage – Cagnot, French. It kept turning over at corners.
1794 Crude Gas Engine – Robert Steel, English.
1801 Gas Engine from wood – Lebon d‟Humberstien, French. Basic 2 stroke.
1805 First Internal Combustion Engine vehicle. Voltaic spark, kick open exhaust – Issac de Rivaz, Swiss.
1826 Forty liter Gas Engine. Poor power/weight ratio – David Gordon.
1858 First proper 2 stroke. Coal gas using platinum spark plug – Joseph Lenoir Belgium.
1877 Niklaus Otto tried to patent the 4 stroke but Karl Benz fought the patent, and in 1886 the patent was made
invalid and Benz was in charge of the 4-stroke development. The actual designer of the 4 stroke was Otto‟s
Chief Engineer – Gotlieb Daimler. (Hence the Daimler cycle).
1884 Engines were mass produced by Benz.
1892 Rudolph Diesel designed a heat engine. (Compression Ignition Engine).
1897 First Great British Diesel Engine – Mirlees.
1900 Engines followed two paths – Spark Ignition Engine (SIE) and Compression Ignition Engine (CIE).

The different types                                               Heat Engines
of engine:
                             Steam Engines         Internal Combustion Piston Engines            Gas Turbines


                                     Spark Ignition Engines (Petrol)       Compression Ignition Engines (Diesel)


       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                  M/V Arelia.
Steam Engines – These can be reciprocating or rotary (turbine). They require a boiler and auxiliary pumps to
provide the power, described as external combustion engines, taking up much more space than internal
combustion engines.
Gas Turbines - These are high-powered, expensive and used to power modern major warships, trains and
aircraft. They are not piston engines.
 Internal Combustion Piston Engines (ICPE) – This term includes both the Spark Ignition Engine and the
Compression Ignition Engine.
An IC engine is one in which the heat transfer to the working fluid occurs within the engine itself, usually by
the combustion of fuel with the oxygen of air.
In external combustion engines, heat is transferred to the working fluid from the combustion gases via a heat
exchanger. E.g., steam engines.
IC engines include spark ignition (SI) engines using petrol as a fuel, and compression ignition (CI) engines
(usually referred to as Diesel engines) using fuel oil, DERV, etc as a fuel.
Spark Ignition Engine (SIE) – In the spark ignition engine an easily vaporized fuel, normally petrol is mixed
with air and is ignited by an electric spark at the end of the compression stroke.
Compression Ignition Engine (CIE) – In this engine a fuel of a much higher flash point is used, giving a much
higher safety factor. The fuel is ignited by the high temperature of the air at the end of the compression stroke.
When the air is compressed in the cylinder, by the piston, to several hundred degrees, fuel is injected as a fine
spray into the cylinder. Diesel engines are used because they are economical, self contained and are more
efficient than petrol engines, are generally cheaper to maintain, and their fuel is less hazardous than petrol.

Types of movement
There are two types of movement that can transmit power – reciprocating and rotary.
They transmit power from the piston through the engine to the shaft and propeller.
Reciprocating Movement - Movement in up and down motion. An example is the piston moving from the top
of the cylinder to the bottom of the cylinder.
Rotary Movement – Movement in a circular motion. An example is a propeller shaft.
In a piston engine, both rotary and reciprocating movements are used to convert power from the engine to the
propeller.

Main components of a basic piston engine in general.
The General Basic components of an engine are listed below:
1. Cylinder block and crankcase. The unit forms the principal part of
the engine. It may be cast as a single unit, or the cylinders may be
detachable from the crankcase.
2. Cylinder head. The head, usually detachable, is bolted to the cylinder
block and forms a gas tight and water tight „lid‟ on each cylinder.
3. Sump. This is a light casing fitted to the underside of the crankcase to
contain the lubricating oil.
4. Piston. The piston is a sliding fit in the cylinder bore. It is fitted with
piston rings to prevent gas leakage past the piston. The top of the piston
is known as the crown. The lower part, which acts as the guide is called
the piston skirt.
5. Connecting rod. The connecting rod is attached to the piston at one
end by a gudgeon pin which is fitted to the piston. This is known as the
Little End / Small End Bearing. The bottom end of the connecting rod is
attached to the crankshaft, at the Big End Bearing.
                                                                                    Fig: Basic Engine Components
6. Crankshaft. The crankshaft is carried in main bearings which are part
of the crankcase casting. It converts the reciprocating movement of the piston to more useful rotary movement.




       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                M/V Arelia.
7. Flywheel. Most internal combustion piston engines have a heavy flywheel to carry the engine over the non-
power strokes, particularly in the four-stroke engine where there is only one power stroke in four on each
piston. The flywheel is attached to the crankshaft, and is outside the crankcase.
8. Valves. The valves are usually fitted in the cylinder head, and are called overhead valves. When open they
allow the passage of Air, Fuel, and Exhaust gas, when shut they seal the cylinder.
9. Camshaft. Each valve is lifted by a cam, which is pear shaped and machined in an angular position on the
camshaft so that it will lift the valve for the correct period.
10. Rocker gear. Overhead valves are operated by rockers with one end of each rocker bearing on the cam or
push rod, and the other end on the valve stem.


Engine Construction
General Arrangement of a Diesel Engine
                       Diesel engines have an various number of things to
                       carry out and are, therefore, of various shapes and
                       sizes. Heat utilization of a diesel engine is shown.
                       From simple single cylinder engines to multi-cylinder
                       engines however, the basic components remain the
                       same.

                       Description of the main components
Engines may vary considerably but the major components incorporate the
same:
1. Cylinder block and crankcase. The unit forms the principal part of the engine. It
may be cast as a single unit, or the cylinders may be detachable from the crankcase. A
water cooling space is included in the cylinder block. Small air cooled engines have
fins to provide a large surface area for the cooling air.
2. Cylinder head. The head, usually detachable, is bolted to the cylinder block. In
some small two-stroke engines, however the cylinder head is part of the cylinder and
cannot be detached. A water cooling space in the head communicates with the water
cooling passages in the cylinder block. Air-cooled types incorporate fins, as in the cylinder block.
3. Sump. This is a light casing fitted to the underside of the crankcase to contain the lubricating oil. This is
normally OMD (oil mineral detergent), or a commercial equivalent.
4. Piston. The piston is a sliding fit in the cylinder bore. It is fitted with
piston rings to prevent gas leakage past the piston. The top of the piston
is known as the crown. The lower part, which acts as the guide is called
the piston skirt. Compression rings are fitted to maintain a seal between
the piston and the cylinder wall and an oil control (scraper) ring removes
excess oil from the cylinder wall.
5. Connecting rod. The connecting rod is attached to the piston at one
end by a gudgeon pin, which is fitted to the piston. A bush in the end of
the connecting rod provides a bearing surface. This is called the small
end bearing. The bottom end of the connecting rod is attached to the
crankshaft, with a halved bearing and bottom cap securely bolted to the
connecting rod. This is called the big end bearing.
6. Crankshaft. The crankshaft is carried in main bearings, which are
part of the crankcase casting, with halved bearing shells and bottom
caps securely bolted to the crankcase.
7. Flywheel. Most internal combustion piston engines have a heavy flywheel to carry the engine over the non-
power strokes, particularly in the four-stroke engine where there is only one power stroke in four on each


       Basics Of Internal Combustion Engine By: M.Manindar Kumar                               M/V Arelia.
piston. The flywheel is attached to the crankshaft, and is outside the crankcase, but sometimes it is enclosed by
the clutch case, or the reversing gear case. The flywheel usually incorporates a toothed ring into which the
engine starter pinion engages to start the engine.
8. Valves. The valves fitted to all four-stroke engines and some to two-
stroke engines are mushroom-shaped. They have a long stem, over which a
spring is installed to hold the valve on the seating. The valves are usually
fitted in the cylinder head, these are called overhead valves.
9. Camshaft. Each valve is lifted by a cam, which is pear shaped and
machined in an angular position on the camshaft so that it will lift the valve for the correct period. The camshaft
may lie above the cylinder head, when it is called an overhead camshaft or alongside the crankshaft with push
rods to lift the valves if they are of the overhead type.
10. Rocker gear. Overhead valves are operated by rockers with one end of each rocker bearing on the cam or
push rod, and the other end on the valve stem. Side valves are usually placed immediately above the cams so
that the rockers are not required.
11. Tappets. All valve gear is fitted with tappets, a form of set screw and
locknut, which may be fitted to the rockers, the push rods, or the tappet
spindle for side valve engines. The tappets are adjusted to give a slight
clearance for expansion between the tappet and the valve stem. This
clearance is always stated for inlet and exhaust valves of each engine.
12. Timing gear. The camshaft must be accurately timed to the crankshaft
so that the valves will open when required and for the correct period. The
timing gear consists of gear wheels usually mounted at the front end of the
crankcase and enclosed by a timing case. The gear wheels are marked to
show the correct setting.
13. Fuel pump and injectors. The fuel injection pump may be fitted on the
side of the engine, or an individual fuel injection pump may be fitted
alongside each cylinder. The pump is driven by the timing gear so that fuel
is injected into each cylinder at the correct time. Each cylinder head is fitted
with an injector, which consists of a non-return valve and a nozzle which
produces a fine spray of fuel into the cylinder. The speed of the engine is
varied by a governor which controls the quantity of fuel discharged by the
fuel pump.
14. Joints/Gaskets. These are fitted to prevent the leakage of oil, gas or water. The cylinder head gasket is
normally made from copper and compressed fiber, whilst other joints are of treated paper or metal-to-metal with
joining compound between the mating faces.

Engine Cycles
The Four Stroke Cycle
The four-stroke cycle is so called because there are
four distinct operations to complete each cycle. The
cycle keeps the piston moving upwards and
downwards and the crankshaft revolving, and the
sequence is as follows:

The Induction / Suction / Intake Stroke – The
piston is moving down the cylinder and sucking in
clean air through the air inlet filter, down through the
inlet manifold and into the cylinder, via the inlet
valve. The inlet valve has opened for this specific
operation and closes when the piston is at the bottom and the cylinder is full of clean air.



       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                M/V Arelia.
The Compression Stroke – The piston is now moving back up the cylinder, both the inlet valve and the exhaust
valve are shut and no air can escape. The air is now being compressed (compression) and as this occurs it heats
up. When the piston is at the top of the stroke and the air is at its most compressed state, diesel fuel is injected
into the cylinder as a high-pressure spray.
The Power stroke – The fuel and air mixture compressed within the cylinder, burn
rapidly and expand, driving and forcing the piston down, producing the power.
The Exhaust stroke – The piston travels back up the cylinder pushing all spent
gases out of the opened exhaust valve, which closes when the piston reaches the top
of its travel. The inlet valve then opens as the cycle starts again.
The power produced is, in part, directly related to the volume of the cylinders,
although other factors enhance performance. It is the amount of fuel/air burnt that
produces the power.
Combustion (the fire triangle) – All internal combustion engines require Heat, Fuel
and Air for combustion. Combustion takes place when energy is released by the
atomizing of the fuel under pressure and bringing it into contact with the high
temperature of the compressed air. This mix of fuel, air and heat causes an increase
in temperature and pressure in the top of the cylinder. The ignition and expansion
that occur will push the piston downward.

The Two Stroke Cycle
The exhaust valve opens much earlier in the power stroke than in the case of the 4- stroke cycle. With the piston
still descending inlet ports cut into the base of the cylinder walls are uncovered. Air enters the cylinder until the
piston again covers the inlet ports as it ascends. The exhaust valve has by this time closed so that a charge of air
is trapped in the cylinder. The piston continues to rise, compressing air until just before the top of the stroke
when the fuel is injected. The fuel is ignited by the heat of compression and the burning gases drive the piston
down in the power stroke.
         Fig1: Two Stroke Cylce                                   Fig2: Two-Stroke Cycle




      THE CRANKSHAFT WILL ROTATE TWO REVOLUTIONS TO COMPLETE ONE FULL CYCLE IN THE 4-
      STROKE CYCLE AND ONE REVOLUTION IN THE 2-STROKE CYCLE.




       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                  M/V Arelia.
Basic Connecting Rod Mechanism:




Bore = Cylinder Diameter
Stroke = piston movement (BDC to TDC) = 2 * crank radius
Bore / stroke = “squareness”
        If >1 is “over square”
        If <1 is “under square”




The force on the piston is affected by the quantity of air induced. It is therefore affected by the gas dynamics
(breathing) of the engine, which is mainly determined by engine speed. The mechanical losses (friction) depend
on the piston forces and RPM.
 Friction power loss is directly proportional to RPM³ (approx.)
Thus, the fundamental output of a reciprocating IC engine can be considered to be torque - it is theoretically
produces even when engine speed (RPM) is ZERO.

The torque fluctuations are smoothed out by:
   1. Multi – cylinder arrangement
   2. The use of a flywheel

       So that the torque output from the engine‟s drive shaft is “smooth” at any given condition of speed and
       load.




       Basics Of Internal Combustion Engine By: M.Manindar Kumar                              M/V Arelia.
Essential Mechanical Systems
Diesel engines have 3 main systems that provide the following functions.
     Lubricating oil system to cool and lubricate the moving parts of the engine.
     Fuel system to provide clean fuel to the injectors so that it can be burnt to give power.
    Cooling system that will cool the engine and its auxiliary components.
The basic mechanical system
Any basic system consists of a tank, filter, pump and a method of
indicating it is running correctly. Systems also have a way of
returning excess fluid back to the tank.
The tank is filled to the correct working level, excess can be drained
away. The liquid is drawn through the filter which removes any
debris. The liquid is then pumped up to pressure using the pump and
discharged to the system where it is used. Liquid is then returned
back to the tank and the cycle repeats itself. Oil is feed to the sump
and cooling water into the fresh water header tank. The system
pressure can be monitored using a pressure gauge. Oil, water and fuel levels are always checked prior to starting
the engine.
It is good practice to monitor the conditions of the mechanical systems regularly for problems such as
overheating, lack of cooling or leaks on the various systems.

Lubricating oil system
The lubrication system will supply clean oil under pressure, from
the sump to the engine bearings, gears and rocker gear. Most
lubricating oil systems will have an oil pressure gauge for checking
the system pressure. The lubricating oil level is checked using a dip
stick which shows the level in the engine sump. The oil system has
a thermostat to keep the lubricating oil at a constant temperature.
Fuel system
Diesel engine fuel systems supplies clean fuel from the fuel tank,
through filters to a lift pumps and finally to the injection pump, it is
then delivered to the individual injectors which spray the fuel into
the top of the piston. Fuel systems must be kept clean and free of
any water, which would otherwise collect at the bottom of the fuel
tank.




                                                                                       Cooling systems
                                                                                       Diesel engines are cooled
                                                                                       by air or by a water
                                                                                       cooling system. Air is
                                                                                       used to cool the outer fins
                                                                                       of the cylinder head. It is
                                                                                       directed over the fins
                                                                                       giving a cooling effect.
                                                                                       Most diesel engines are




       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                  M/V Arelia.
cooled by fresh water which circulates under pressure around the engine cylinder block and cylinder head‟s
narrow passages; this fresh water is cooled by pumped sea water which also passes through a fresh water cooler.
The fresh water is maintained at the correct temperature by a thermostat.


 THERE ARE MANY PARTS ON ENGINES WHICH GET HOT AS THE ENGINE WARMS
 UP, CARE SHOULD BE TAKEN TO KEEP CLEAR OF MOVING AND HOT
 COMPONENTS. THE COOLING WATER PIPE WILL GET VERY HOT UNTIL THE
 THERMOSTAT VALVE STARTS TO REGULATE THE ENGINES TEMPERATURE.




                                                                             Engine     Air        Oil
                                              Fresh Water Pump               Cylinder              Cooler
                                                                                        Cooler
                                                                             Head &
                                                                             Block




                                              Thermostat


                                                                         Header
                                                                         tank &
                                                                         Heat
                               Strainer




                Sea Cock                        Sea Water                                        Exhaust
                                                Pump                     Exchanger
                                                                                                 Manifold



                                          Directly Attached to the Engine - Indirect or Fresh Water Cooling

Important Properties of lubricating oils
Lubricating oils are a product of the crude oil refining process. The various properties required of the oil are
obtained as a result of blending and the introduction of additives. The physical and chemical properties of oil
are changed by additives which may act as oxidation inhibitors, wear reducers, dispersants, detergents, etc.
The important lubricant properties will now be examined.
Viscosity has already been mentioned with respect to fuel oils, but it is also an important property of lubricating
oils. Viscosity index is also used, which is the rate of change of viscosity with temperature.
The Total Base Number (TBN) is an indication of the quantity of alkali, i.e. base, which is available in a
lubricating oil to neutralize acids.


       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                            M/V Arelia.
The acidity of oil must be monitored to avoid machinery damage and neutralization number is used as the unit
of measurement.
The oxidation resistance of a lubricant can also be measured by neutralization number. When excessively
oxidized an oil must be discarded.
The carbon-forming tendency of lubricating oil must be known, particularly for oils exposed to heat. A carbon
residue test is usually performed to obtain a percentage value.
The demulsibility of oil refers to its ability to mix with water and then release the water in a centrifuge. This
property is also related to the tendency to form sludge.
Corrosion inhibition relates to the oil's ability to protect a surface when water is present in the oil. This is
important where oils can be contaminated by fresh or salt water leaks.

         The modern lubricant must be capable of performing numerous duties. This is achieved through
blending and additives. It must prevent metal-to-metal contact and reduce friction and wear at moving parts.
The oil must be stable and not break down or form carbon when exposed to high temperatures, such as where
oil cooling is used. Any contaminants, such as acidic products of combustion, must be neutralized by alkaline
additives; any carbon build up on surfaces must be washed away by detergent additives and held in suspension
by a dispersant additive. The oil must also be able to absorb water and then release it during purification, but
still should protect the metal parts from corrosion.

The various types of engine and other equipment will have oils developed to meet their particular duties.
         Trunk piston engine lubricating oil must lubricate the cylinders as well as the crankcase: some
contamination from the products of combustion will therefore occur, resulting in acidity and carbon deposits.
The oil must, in addition to lubricating, neutralize the acids and absorb the deposits.
         Turbine oil, while lubricating the moving parts, must also carry away considerable quantities of heat
from the bearings. This calls for stable oil which will not break down at high temperatures or form deposits.
Where gearbox lubrication is also required certain extreme pressure (EP) additives will be needed to assist the
lubricating film. Contact with water in the form of steam will be inevitable so good demulsifying properties will
be essential.
         Slow-speed diesel engines will have separate cylinder and crankcase lubrication systems. The cylinder
oil will have to neutralize the acidic products of combustion and also have good detergent properties to keep the
metal, surfaces clean. Crankcase oils are detergent type, multi-purpose oils or rust and oxidation inhibited.
Good demulsifying and anti-corrosive properties are required together with oxidation resistance which is
provided by the inhibited crankcase oil. The detergent or multi-purpose oil is particularly useful where oil
cooling of pistons occurs or where contamination by combustion products is possible.

Oil treatment
Both fuel oils and lubricating oils require treatment before passing to the engine. This will involve storage and
heating to allow separation of water present, coarse and fine filtering to remove solid particles and also
centrifuging.
The centrifugal separator is used to separate two liquids, for example oil and water, or a liquid and solids as in
contaminated oil. Separation is speeded up by the use of a centrifuge and can be arranged as a continuous
process. Where a centrifuge is arranged to separate two liquids, it is known as a 'purifier'. Where a centrifuge is
arranged to separate impurities and small amounts of water from oil it is known as a 'Clarifier'. The separation
of impurities and water from fuel oil is essential for good combustion. The removal of contaminating impurities
from lubricating oil will reduce engine wear and possible breakdowns. The centrifuging of all but the most pure
clean oils is therefore an absolute necessity.


       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                 M/V Arelia.
Functions of a lubricant:
The further less obvious, functions that lubricants perform are
A sealant: sealing the piston rings of an engine, to reduce the leakage of hot high pressure gases from the
combustion space.
A cleaner: Removing products of combustion, such as wear debris, and soot (carbon), maintaining cleanliness.
A coolant: transporting heat away from pistons and bearings to oil coolers, thus performing the function of a
heat transfer fluid.
Anti-Corrosion: acting as a carrier for alkali additives, to neutralize acids formed during the combustion
process.
Hydraulic medium: transmission of control signals and force in hydraulic power systems, control systems,
governors, fluid couplings etc.
Preservative: Preservation of metallic components, by being coated with a lubricant, oxidation is prevented,
preventing rusting.
        A lubricant comprises two main ingredients namely: Base oils and additives.
Base oils: the base oils forms the greatest part of the lubricant, typically some 85-95%. With some high additive
content oils, such as cylinder oils, the base oil content is about 70%.
Additives: The additive is blended with the base oil, to enhance or modify the performance characteristics of the
lubricant. This allows the finished oil to perform its specific function. There are many different additives and
the additive selection is dependent on the final use of the lubricant.
The base oil may be one of three basic types:
        Mineral oil: This is derived from crude oil
        Synthetic oil: which is a man made oil.
        Vegetable or animal oil: This is derived from vegetable or animal origins like: castor oil, sperm oil, rape
seed oil, lard oil, corn oil, and tallow.
The selection of the type of base oil is made primarily on the characteristics required

Conclusion:
Lubrication is the minimization of energy losses due to friction between any two surfaces in contact
and possibly moving. Lubricant is the medium, which separates any two surfaces, which are arranged
to move relative to each other. The basic properties of the lubricating oil are studied.

References:
-Marine Engineering Guide, Slow Speed Diesel By Griffiths, Marine Engineering Practice by Rogers &
Mayhew, Eastop & McConkey, Richard Stone.




       Basics Of Internal Combustion Engine By: M.Manindar Kumar                                M/V Arelia.

								
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