Elements of mechanical engineering pdf


 

PDF | On Dec 16, , GURURAJ D GOKAK and others published ELEMENTS OF MECHANICAL ENGINEERING. ELEMENTS OF MECHANICAL ENGINEERING. [15EME14 / 24]. Department of ME, ACE. CHETHAN B S. Page 2. 1. Direct solar energy. 2. Wind energy. 3. Download Elements of Mechanical Engineering Notes pdf. We provide nbafinals.info 1st -year Elements of Mechanical Engineering study materials to.

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Elements Of Mechanical Engineering Pdf

Mechanical Engineering Ebooks. Download free element of Mechanical engineering ebooks. Available in PDF. Click on chapter for download tutorials and for. related to mechanical engineering so that they will have a minimum K.R. Gopalkrishna, “A text Book of Elements of Mechanical Engineering”-Subhash. Department of Aerospace and Mechanical Engineering An understanding of what Mechanical Engineering is and to a lesser extent what it is.

Energy exists in various forms. There are different other forms of energy namely, kinetic energy, potential energy, internal energy, mechanical energy, thermal energy, chemical energy etc. All forms of energy are inter-convertible by appropriate processes. The energy existing in the earth is called capital energy and that which comes from the outer space is called celestial or income energy. Electromagnetic energy, gravitational energy, particle energy and potential energy of meteorites. The useful celestial energy sources are the electromagnetic energy of the Sun, called direct solar energy.

Select your rental days. Select your chapters. Rajput Number of Pages Available. Snapshot About the book. Audience of the Book: This book has been written specially to meet the exhaustive requirements of the subject 'Elements of Mechanical Engineering' of B. Key Features: The main features of the book are as follows: The presentation of the subject matter is very systematic and the language of text is in a lucid, direct and easy to understand manner. The book provides a comprehensive treatment of the subject matter under wide range of topics mentioned in the syllabus common to the above mentioned universities, including a large number of solved examples to support the text wherever required.

At the end of each chapter Highlights, Objective Type Questions, Theoretical Questions and Unsolved Examples have been added to make the book a complete unit in all respects. Table of Contents: PART - A 1. Basic Concepts of Thermodynamics 2. First Law of Thermodynamics 3. Gas Power Cycles 5. Internal Combustion Engines 6. The rain water flowing as river can be stored at high levels by building dams across river and released in a controlled manner to generate mechanical power using water turbines.

This mechanical energy is further converted into electricity using generators coupled connected to the turbines. This results in rainfall. This is called the hydrological cycle. Such water having high potential energy is allowed to flow through penstock pipes to convert it to kinetic energy.

Enormous amount of energy is released during nuclear fusion process. The nuclear energy measured in millions of electron volts MeV is released by either fusion or fission nuclear reactions. As a result of such reactions. The nucleus is made up of protons and neutrons.

U isotope is a fissile material which is used directly as nuclear fuel. Any atom consists of a small. Nuclear Power Plant Page Nuclear fuels include uranium. A nuclear reaction involves changes in the structure of the nucleus.

During fission. Chances of radiation hazards is more. Free from air pollution. Mysuru Nuclear power plant consists of a nuclear reactor. Fuel cost is high. It is further cooled by mixing with cooling water drawn from cooling towers.

Storage and transportation costs of fuel are less. Plant maintenance cost is high. Control rods made of cadmium. It is then pumped back to the steam generators and this cycle continues. This steam is used to drive turbines and turbines are coupled with generators to produce power.

High power generation. Disposal of radioactive waste is difficult. The reactor and steam generators are housed inside a structure. Nuclear reactions produce enormous amount of energy which is transferred to steam generators boilers. Since its basic function is to generate steam.

Steam is produced in a closed vessel called boiler. It should be easy to maintain and inspect. Applications of boilers The steam generated by boiler has wide industrial and domestic applications. Power generation in steam turbines 2. Cooking etc. It should provide stem quickly after starting. These include: Materials used in building a boiler should be corrosion and wear resistant. A boiler is a vessel in which steam is generated at the required pressure.

It should occupy less floor space. It should have all types of necessary mountings for safe operation. It should be simple in construction. Hot water generation 6. Steam engines 3. Heating rooms of buildings 5.

It needs to have various mountings fitted to the vessel for safety and requirements of operation and they will be under pressure even when the steam is shut off.

Function of a boiler The function of a boiler is to supply steam at the required constant pressure with its quality either dry or nearly dry. It should meet the variations in steam requirements.

Such boilers have low rate of water circulation and hence. Lancashire and Locomotive boilers. Cochran boilers. Lancashire and Cochran boilers. Babcock and Wilcox boiler. Classification of boilers 1. Locomotive boilers. Such boilers are of high capacity. LaMount and Benson boilers. Cornish and Cochran boilers. Mysuru It should not accumulate mud. Babcock and Wilcox boilers.

Scotch Marine. Locomotive boiler etc.

Stirling boiler. Yarrow boiler etc. Cornish boiler. Natural air at atmospheric pressure is used for fuel combustion due the draft created by chimney. Marine boilers. Mysuru Boiler pressure Low pressure boilers: Generate steam in the range 3. Gaseous fuel: LPG or natural gas is used as fuel.

These boilers are fixed and cannot be used mobile while moving the boiler from one place to the other. Generate steam in the range 10 to 25 bar. These have more than one tube. Coal is used as a fuel to generate steam. High pressure boilers: Generate steam at pressure greater than 25 bar.

Boilers using nuclear or electrical energy are also used but their industrial application is limited. Liquid fuel: Oil fired boilers. These have only one fire tube. Here air is forced through the boiler using fans or blowers. If the boilers can be used while moving them from one place to the other.

Mysuru Comparison of fire tube and water tube boilers includes advantages and disadvantages of fire tube and water tube boilers Page It can generate steam up to 15 bar and 8.

Underneath the grates. It is used where large amount of steam is required. It has good steaming capacity since flue gases heat the water from three sides. It is a horizontal. The two tubes are connected at their rare ends in to common passage which is connected to the chimney. The two large flue tubes have grates to prevent ash and coal particles from entering the tube. Steam pressure that can be generated is as low as 15 bar. At the rear end. Efficiency of the boiler is high due to accessories like superheater.

Upon combustion of the fuel at the bottom tube channel. The pressure gauge is provided at the front end and blow-off cock at the bottom of the shell. After passing along the bottom channel. Once again. Boiler takes more time to generate steam initially. From the rear end.

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After this pass. Since flue tubes are used. If superheated steam is required. Occupies large floor area. Dampers are used to control fuel combustion by closing or opening the passage of air flow.

The boiler has most of the mountings and accessories for efficient operation. The top of the boiler has steam collecting pipe. Flue gases pass along the length of the side flue tubes channels from the front end to the rear end of the shell. These water tubes are connected to two headers.

The chain grate moves at slow speeds with coal burnt on top of it. Dampers are provided to control the rate of fuel combustion. The superheater is a U-shaped tube suspended underneath boiler drum. It has high steaming capacity and can be operated under sudden pressure variation requirements. This generates superheated steam. Water tubes are suspended at low inclination angle from the water drum with one of its bottom end supported by brick structure.

Headers help in easy circulation of water. If required. This steam rises to the main drum and is tapped out using steam pipes.

Large number of parts to be assembled. Flue gas and draft pressure can be easily controlled. It forms steam in the process of movement within the water tubes. Support structure is made of steel which is flexible and supports well. The pressure gauge and water level indicators are provided at the front end. Can meet fluctuating load requirements. Initial planning and management of operations is more. Over-burnt tubes can be replaced easily.

The density of water decreases as it gets heated up and hence rises in water tubes due to thermo-syphon effect. High initial cost.

The boiler mountings are required for the complete control of steam generation, measurement of some of the important steam properties, and to provide safety to the boiler. They are fitted directly on the boiler. The essential boiler mountings are, Water level indicators two nos. Boiler accessories are required to improve the efficiency of boiler and to ensure proper working of the boiler.

The boiler accessories are not mounted directly on the boiler. The boiler accessories are, Economizer, Air preheater, superheater, feed pump, steam separator and steam trap. Safety mountings Safety valves two nos. Feed pump 7. Feed water heater 8. Safety Mountings a. A boiler is designed to produce steam at a certain rated pressure called the designed pressure.

However, working pressure is less than the designed pressure. When boiler is in operation, there may be sudden increase in the steam pressure due to low water levels or increased rate of combustion. Due to this, excess steam accumulates inside the boiler and may pose danger to the boiler. This excess steam must be immediately released from the boiler. A safety valve does the function of expelling opens the excess steam from the boiler.

After this, the safety valve shuts off closes automatically. The safety valves blow off the excess steam with a loud distinct noise so as to alert the boiler operator. Boilers are fitted with at least two safety valves so that even if one fails, the other will definitely work.

The commonly used types of safety valves are, dead weight safety valve, lever-operated safety valve, spring-loaded safety valve and, high steam and low water safety valve. Fusible plug is a safety device used to extinguish fire in the boiler furnace, when the water level falls too much below the normal level. It is fitted on the crown of the furnace or the combustion chamber.

The fusible plug consists of a plug made of a bi-metal which melts at high temperatures. The molten fusible plug material makes holes at the bottom of the boiler drum, thus making way for the steam inside the drum to escape to the atmosphere. By this, safety hazards due to high temperature steam are avoided. One of them will serve as a standby in case the other fails. The pressure gauge is mounted on the front top end of the boiler so that it is clearly visible to the boiler operator.

The pressure in a pressure gauge is indicated to be higher the atmospheric pressure. The function of a steam stop valve or junction valve is to regulate the flow of steam from the boiler. Junction valves change the direction of steam by 90o and steam stop valves allow steam to pass in the same direction without changing its direction.

When the level of water inside the boiler drum falls below a specified minimum level, it is supplied with additional water called feed water, to bring it back to the specified level. The feed water is fed into the boiler at high pressure using feed water pump and via feed check valves.

The feed check valve performs dual functions; it regulates the rate of feed water flowing into the boiler, and it does not allow the water from inside the boiler to escape out through the regulator openings. Blow-off valve The function of the blow-off valve is to periodically remove sediments collected at the bottom of the boiler, while the boiler is in operation.

It is also used to empty out the boiler drum during inspection and cleaning. The operational efficiency of the boiler is increased by cleaning or overhauling the boiler drum and fittings regularly or on a schedule-basis.

An air preheater is installed between the economizer and the chimney. Thus the thermal heat efficiency of the boiler increases. The manhole serves as an entry for manual inspection and cleaning of the boiler drum. Supply of preheated air to the furnace increases the temperature of the furnace and accelerates the combustion of fuel.

Inspection mountings a. Thus the gases coming out of the boiler contain large amount of heat. The economizer and air preheater improve the overall efficiency of the boiler by reducing fuel consumption and by increasing the rate of combustion. Air preheater recovers heat by heating the air supplied to the combustion chamber for combustion of fuel in the furnace.

It is usually located at one of the sides or on top of the boiler. Maximum amount of heat from the gases can be recovered used before it escapes to the atmosphere through the chimney. The economizer recovers heat by heating the feed water. The two accessories that recover heat from the exit gases are: Economizer and Air preheater.

Mudhole is used to periodically drain the mud. The hot combustion gases from the combustion chamber flow over the tubes and increase the temperature of feed water by a few degrees. It is installed very close to the steam turbine on the main supply line. It is connected to a small bypass pipeline which branches off from the main steam pipeline. The atomized water. The hot feed water is let inside the boiler to form steam.

Steam separator A steam separator separates the water particles from the steam flowing in the pipelines. Reciprocating pumps and rotary pumps are commonly used for the purpose. At the same time the high pressure steam does not escape out of it. Superheater Superheaters are used in boilers to increase the temperature of the steam above the saturation temperature. Injector The injector is located between the exit of the feed check valve and the boiler drum entrance. The injector injects or atomizes conversion into small particles the feed water.

Heating the feed water forms steams at a faster rate compared to cold feed water. The dry saturated steam generated in the boiler is passed through a set of tubes placed in the path of the flue gases. Mysuru c. By using the feed water heater. Steam trap Steam trap is a device used to drain off the condensed water accumulated in the steam pipelines. The injector helps in increasing the steam generation rate of the boiler.

This condition of water at 00 C is represented by the point A on the temperature-enthalpy graph as shown in the T-h or T-S graph. After vaporization is complete.

In all the three phases. The important properties of steam are pressure. Steam is formed in steam generators called boilers. When this water is Page To determine the various properties of steam at a particular pressure. Water is one of the pure substances which can exist in three different phases. When ice melts. During this transformation. As the steam is generated. Consider 1 kg of water at 0o C taken in a cylinder fitted with a freely moving frictionless piston as shown in the figure A.

Since the steam is generated at constant pressure. This constant pressure and constant temperature heat addition is represented by the line BC on the graph. This evaporation will be continued till the same saturation temperature TS until the whole of the water is completely converted into steam as shown in figure E. The saturation temperature is defined as the temperature at which water begins to boil at the stated pressure.

This is point C on the graph. This condition of water at temperature TS is represented by the point B on the graph. When the boiling point of water is reached. Mysuru heated at constant pressure. Further addition of heat. The temperature at which water boils depends on the pressure acting on it. The heating from of water from 0o C to TSo C at constant pressure is represented by the inclined line AB on the graph. This temperature is called saturation temperature TS. When superheating is done by the exhausting combustion gases in a boiler.

Mysuru On heating the steam further at the same constant pressure. The high superheated temperatures pose problems with regard to lubrication. At a given pressure. While expanding in a steam turbine. Both the entrained water molecules and steam co-exist to form a two-phase mixture called wet steam. The steam when superheated is called superheated steam. During this process. Disadvantages of superheated steam 1. The difference between the superheated temperature and the saturation temperature is called the degree of superheat.

The steam evolving from the surface of the water entrains finely divided water molecules in it. The temperature of the steam above the saturation temperature at a given pressure is called superheated temperature. Higher depreciation and initial cost. This superheating is shown by the line CD on the graph.

The entrained water molecules suspended in the steam will be at the saturation temperature and will not yet have absorbed the latent heat and got evaporated in to steam.

Advantages of superheated steam 1. The amount of heat required to increase the temperature of dry steam from its saturation temperature to any desired higher temperature at the given constant pressure is called the amount of superheat or enthalpy of superheat. The wet steam is defined as a two-phase mixture of entrained water molecules and steam in thermal equilibrium at the saturation temperature corresponding to a given pressure.

Mysuru Dryness fraction of steam The quality of steam is specified by the dryness fraction. At constant pressure steam generation process.

Dry saturated steam Saturated steam or dry saturated steam at the saturation temperature corresponding to a given pressure is the steam having no water molecules entrained in it. Dryness fraction of dry saturated steam is equal to 1.

The dryness fraction of a steam is defined as the ratio of mass of the actual dry steam present in a known quantity of wet steam to the total mass of the wet steam. The superheated steam is defined as the steam which is heated beyond its dry saturated state to temperature higher than its saturated temperature at the given pressure.

It is equal to the sum of sensible heat and the latent heat of evaporation. Enthalpy of steam Enthalpy is defined as the sum of the internal energy and the product of the pressure and volume. The steam in this state is said to be superheated. Superheated steam When a dry saturated steam is heated further at the given constant pressure. It is equal to the sum of enthalpy of dry saturated steam and the amount of superheat. Specific volume The specific volume is the volume occupied by the unit mass of a substance.

Specific volume of saturated water It is defined as the volume occupied by 1kg of water at the saturation temperature at a given pressure. Specific volume of wet steam vw When the steam is wet. Specific volume of dry saturated steam It is defined as the volume occupied by 1kg of dry saturated steam at the saturation temperature at a given pressure.

It is equal to the sum of sensible heat and the product of dryness fraction and the latent heat of evaporation. The fraction of the latent heat of vaporization which does an external work is called external work of evaporation. The energy required to change the phase is called true latent heat or internal latent heat.

Internal latent heat The latent heat of evaporation at a given pressure comprises of the energy required to do external work and the energy required to change the phase. The reduction of enthalpy is converted into kinetic energy high velocity of steam loss of enthalpy of steam is converted into gain in its velocity.

The main objective of steam technology is to extract maximum amount of energy from steam. It can generate power ranging from 1 MW to 1. During its movement. The steam gains high velocity at the throat itself. The nozzle is stationary and is well insulated to reduce heat loss to the atmosphere.

Steam turbines are used in electricity generation. The divergent part helps in converting the remaining steam into high velocity and avoids spreading of steam. Steam after doing work in stages. Remaining steam does the work and get exhausted. Drop in pressure causes reaction and change in momentum causes force generation.

Change in momentum leads to work. It is called impulse-reaction turbine. Steam flows along the axis of the main shaft. It is used in high capacity power plants. Steam expands only in the nozzle. In these turbines. It results in reaction and generates more kinetic energy. There is not much difference in inlet and outlet steam pressure over turbine blades. Here the turbine has only two cylinders casing and hence two power outputs. Here steam at different pressures enters at two stages but have single exhaust after work has been done.

Here the turbine has only one cylinder casing and hence only one power output. Here the turbine has more than two cylinders casing and hence more than two power outputs. Steam expands continuously as it passes over the blades. These are used in low capacity power plants and are used to meet demand in peak load.

These turbines exhaust the steam after work is done at a constant pressure. These turbines have single steam supply and steam gets exhausted after work is done. The steam at back pressure is used for other applications sugar industries use such turbines 5. This type is used when steam condensation on blades is to be avoided. The high velocity steam coming out of the nozzle is made to glide over a moving blade.

Such turbines drive compressors. Medium pressure turbines: These turbines operate at 2 to 40 bar pressure. These changes result in maximum change in momentum of steam. These maintain the frequency of AC power. High pressure turbines: These turbines operate at more than 40 bar pressure. Since the impelling action of steam jet on the turbine blades causes them to rotate in the same direction as that of the propelling force.

These are provided with gear box to provide variable speed outputs. The blades are so designed that steam is made to change its direction of motions and velocity. Mysuru Based on inlet steam conditions Low pressure turbines: These turbines operate at 1. These operate at constant speeds. Hence it called reaction turbine.

When steam flows over turbine blade. Thus the net force acting on the blades is the sum of reaction force and change in momentum as shown in the diagram. The blades are so designed that steam passing over it expands. The change in direction and velocity of steam causes change in momentum of the blades. Mysuru High pressure steam is made to pass over the blades without expansion in the nozzle unlike impulse turbines.

When a number of such blades are fitted on a circular wheel called rotor. As there is no change in pressure while steam flows over the blades. The resultant of this causes the blades to move.

The steam particles exert centrifugal pressure all along their path on blades. Velocity increase of steam in nozzle is shown by the line PQ and velocity reduction on the blades is shown by the line QR. Figure shows the pressure-velocity diagram of the DeLaval turbine operation. Mysuru It is an impulse turbine. Steam is initially expanded in a nozzle from high pressure to low pressure and from low velocity to high velocity.

The change in direction of steam leads to a change in momentum of the blades. Pressure drop in the nozzle is represented by the curve AB. In the DeLaval turbine impulse. These turbines produce mechanical power by the combined action of resultant of centrifugal forces and change in velocity of steam.

The velocity of the steam gradually decreases as it glides over the blade surface. The high velocity steam coming out of the nozzle is made to glide over a curved vane called blade. The actual reaction turbine called the impulse-reaction turbine consists of a number of rows with moving blades as well as fixed blades fixed alternatively as shown in the figure. Pressure drops continuously when steam passes over the blades causing simultaneous increase in its velocity.

In addition of reaction force of steam. Thus the net force acting on blades is a vector sum of centrifugal and reaction forces. The high pressure steam passing over the first row of fixed blades undergoes drop in pressure with increase in its velocity.

This causes a reaction force enough to sustain the blade motion. Then it enters first row of moving blades where its pressure further drops and velocity is converted into mechanical energy by way of rotation of the rotor.

Again Page Turbines blades are specially designed to cause the nozzle effect. Mysuru this enters second row of fixed blades and this process continues till all the energy in the steam is exhausted.

Both the compressor and gas turbine are mounted on the same shaft. The combustion gases at high pressures are made to pass over moving blades of the turbine. The low pressure.

A gas turbine consists of a combustion chamber in which liquid fuel is burnt in presence of compressed air. The high pressure and high temperature gas is made to pass over turbine blades.

This is the mechanical power thus produced. In the combustion chamber. Open cycle gas turbine. Closed cycle gas turbine and. The gas coming out of turbine is made to pass through cooler where it is cooled. This cycle repeats. The air compressor sucks the air from the atmosphere and compresses it.

The compressed air coming out of compressor is heated by the heater. Again the compressor draws fresh air from atmosphere and compresses it and this continues.

Both the compressor and turbine rotor are mounted on the same shaft. The atmospheric air is drawn and compressed to high pressure by the compressor. The impulsive force of the jet exerted on the curved blades sets the wheel in to rotation rotates the wheel in the direction of jet impingement.

Water drives the turbines and thus mechanical power is developed which is converted into electrical power by the generators coupled with the turbines. This high velocity water jet is made to strike a series of curved vanes blades mounted on the periphery of the rotor. The water comes out of the nozzle as a jet at high velocities. An impulsive turbine requires high head height or potential energy and low discharge flow rate at the inlet of the turbine.

The difference of pressure at the entry and the exit of the blades is called reaction pressure. Impulse turbine e. Jonval turbines etc. Thompson turbines. The rotor is keyed to a shaft. Pelton wheel. A part of pressure energy is converted in to kinetic energy of water which is absorbed by the turbine wheel.

Reaction turbine Francis. Water leaving the turbine blades will be at a low pressure. They produce hydro-electric power. This pressure difference sets up the turbine wheel in to rotation in the opposite direction. The water passed onto the turbine will have both pressure and kinetic energies. Water flowing over blades will be at atmospheric pressure as high pressure of water is converted to its high kinetic energy in the nozzle. Dams are constructed across water to create reservoirs.

Water is carried from these dams to the turbines through large pipes called penstocks. The jet of water coming out of nozzle impinges on the curved blades known as pelton cups of the pelton wheel. This impulsive force rotates the pelton wheel. During this. The pressure inside the turbine casing will be atmospheric pressure.

Water at high head height is supplied to a nozzle which controls its flow. The other end of the draft tube is immersed in the discharging side of the water called tail race. From the runner. To discharge outlet the water at low pressure.

The Kaplan turbine is a low head reaction turbine in which water flows axially. The water from the guide blades strikes the runner blades axially imparting the kinetic energy to rotate it. The fuel supplies the thermal heat energy when it burns inside the I. An engine in which combustion takes place outside the engine is called external combustion E.

Steam engine. Many experimental engines were developed till But the breakthrough in engine technology was achieved when German engineer Otto built the famous Otto petrol-operated engine.

Due to this force acting on the piston, the piston moves and hence work is done which is utilized in various domestic and industrial applications. The reciprocating motion linear motion of the piston is converted into rotary motion with the help of linkages.

Stirling cycle, Ericsson cycle, Lenoir cycle, Atkinson cycle and Brayton cycle. Multicylinder engines are classified as: Here all cylinders are arranged linearly in the engine. Cylinders are arranged radially around a common power transmission arrangement.

Cylinder block: The cylinder block is the main supporting structure for engine components. It is an air-tight and gas-tight movable cylindrical component which reciprocates inside the cylinder. It houses cylinders. This is the cylindrical portion in which the piston moves up and down. Combustion chamber: This is the space between the piston and the cylinder head where combustion of fuel takes place.

Cylinder head: The top end of the cylinder is closed by a removable cylinder head. The cylinder head consists of two valves the inlet valves and the exhaust valves.

Here the fuel releases thermal energy and exerts high pressure and temperature on the piston. The bottom portion of the cylinder block is called crank case where lubricating oil sump is present. The varying volume inside the cylinder is due to reciprocation of the piston.

EME (Elements of Mechanical Engineering) Notes 2015-16 Even

It is heavy circular mass gets energy during power stroke and gives it back during other strokes of the engine. One end of the crank is connected to the connected rod and the other end to the crankshaft. It is enclosed in a crank case where lubricating oil is present and using splash method. It is mounted on the crankshaft and eliminates the cyclic fluctuations created by gases inside the engine. Spark plug or injector: The SI engine has spark plug and the CI engine has injector for the fuel to be ignited.

Feed pump: It is provided in the diesel engine to pump fuel to the injector which is kept on the cylinder head. Inlet manifold: It is provided in the petrol engine for proper mixing of air and fuel. This prevents escape of high pressure gases into the crank case. Inlet and exhaust valves: These are mechanical members which are provided at the top or side of the cylinder for intake of charge and exhaust of gases. Cams have followers.

Mysuru 6. Piston rings: These are fitted to the slot provided around the piston and form a tight seal between cylinder and the piston wall.

Crank transmits the motion given by the connecting rod to the rotary motion of the crankshaft. Connecting rod: It links the piston with the crank and transmits the force exerted by the gases on the piston. These are connected to the camshaft using a simple gear arrangement and operate at half the speed of the crankshaft. Its small end is connected to the piston using a gudgeon pin and the big end is connected to the crank pin. It is the principal rotating component of any engine through which power is transmitted to the wheels or other systems.

The compression rings press the cylinder walls hard. In a two stroke engine. The function of oil rings is to extract the lubricating oil from the cylinder walls and send it back to the oil sump crank case through the holes provided on the piston. They are normally mounted on top of the cylinder. Bottom dead center BDC: The extreme position of the piston nearer to the crankshaft is called bottom dead center or BDC.

Clearance volume Vc: It is the volume of cylinder above the top of the piston. Piston Speed: Compression ratio RC: The ratio of the total cylinder volume to the clearance volume is called the compression ratio. Top dead center TDC: The extreme position of the piston nearer to the cylinder head is called top dead center or TDC.

The inside diameter of the cylinder is called bore. Swept volume or Stroke volume Vs: As the piston reaches BDC. The working of each stroke is shown in the figure below and its details have been discussed further.

A 4-stroke petrol engine performs four different strokes to complete one cycle. As the piston moves downwards. Hence it is also known as Otto cycle engine.

The suction stroke is represented by the line AB on P. Suction stroke At the beginning of the stroke. V diagram as shown in the figure. The inlet valve opens and the exhaust valve will be closed. Working of a 4-stroke petrol engine 1. Hence it is also called diesel cycle engine. In the next cycle the piston which is at TDC moves to BDC thereby allowing fresh charge to enter the cylinder and the process continues.

When the piston reaches the TDC. The working principle of a 4-stroke diesel engine is based on theoretical diesel cycle. As the piston moves upwards. Also gas expands and does work on the piston so this stroke is also called an expansion stroke. The inlet valve is closed and exhaust valve is opened.

The combustion of fuel liberates gases and these gases starts expanding. Thus work is obtained in this stroke. Mysuru P-V diagram 2. V diagram. The expansion of gases is adiabatic in nature and this is shown by the curve DE on P. The compression ratio in petrol engines ranges from 7: Due to expansion. The power impulse is transmitted down through the piston to the crank shaft through the connecting rod.

As the piston reaches the BDC. This causes crankshaft to rotate at high speeds. A part of the burnt gases escape through the exhaust valve out of the cylinder due to their own expansion. As the piston moves upward.

Both inlet and exhaust valves are closed. Both inlet and exhaust valves remain closed. The combustion of the fuel takes place at the constant volume and is shown by a line CD on the P. The pressure and temperature of the charge increases and this is shown by the curve BC on the P. Exhaust Stroke The details regarding the working of each stroke and the theoretical diesel cycle have been shown in the respective diagrams.

Compression Stroke 3. The 4 different strokes are 1. Suction Stroke 2. P-V diagram Page Mysuru Working of 4-Stroke Diesel Engine 1. When the piston reaches the BDC. Suction stroke At the beginning of the stroke piston is in TDC and during the stroke. The downward movement of the piston creates suction in the cylinder and as a result.

The inlet valve is closed and the exhaust valve is opened. As combustion of fuel takes place. Mysuru 2. There are three ports. In a 2-stroke engine. Exhaust port: Through which the burnt gases are discharged out of the cylinder. In these engines there are no suction and exhaust strokes. This process is shown by the line CD on PV diagram. Transfer port: Through which the charge is transferred from the crankcase to the cylinder.

Inlet port: Through which admitting of charge into the crankcase takes place. This is shown by the line SA on PV diagram. In the next cycle the piston which is at the TDC moves to BDC thereby allowing fresh air to enter into the cylinder and the process continues.

The ports are the openings in the cylinder opened and closed by the movement of piston within the cylinder.

The compression ratio ranges from Exhaust stroke At the beginning of the stroke piston is in BDC and during this stroke. Both inlet and the exhaust valves are closed. At the point D fuel supply is cutoff. Both inlet and the exhaust valve remain closed.

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