The term "Governing" means the action of varying the fuel supply in accordance with the load demand so that the engine runs at practically constant speed. Below are the some important methods of governing of internal combustion engines.
01) Hit & Miss Governing-
This method is suitable for small gas engines. In this, the rotational motion of the cam actuates the rocker through the roller. The rocker carries a pecker, which strikes against the pecker block and lifts the valve against the pressure of the spring. At very high speed, the pecker block is lifted by the rod due to rise up of governor sleeve resulting the engine performs an idle cycle because no fuel is now being supplied.
This method of governing is quite simple but owing to the violent explosions which usually occurs as a result of extra scavenging which takes place immediately after "missed explosion', produces uneven turning moment necessitating the use of heavy flywheel which increase the friction at the bearing and lowers the mechanical efficiency of the engines.
02) Qualitative Governing-
This method is widely used in all heavy oil engines besides being always used on two stroke cycle engines in which the air fuel mixture has to be admitted to the engine cylinder to drive out the burnt charge of the previous cycle.
In this method, under the action of centrifugal governor the amount of fuel entering the cylinder is varied by altering the stroke of the Oil Pump or by passing a part of fuel which would have otherwise been injected into the engine cylinder back to the oil tank or by delaying the closing of the suction valve in the fuel pump.
03) Quantitative Governing-
In this method, the quantity of air -fuel mixture flowing into the cylinder is varied accordingly. This may be done by decreasing the lift of the inlet valve or by throttling the mixture before it is made to enter the engine cylinder. This method is largely used for governing petrol and big gas engines.
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Saturday
How To Prevent Diesel Knock In Internal Combustion Engine?
When sudden and violent knock are experienced in petrol engine, these knocks are termed as "Detonation". Just like petrol engines, a high-pressure wave set up in compression ignition engine (Diesel Engine) and this wave strikes the cylinder wall, cylinder head and piston resulting in knock. These knocks are known as "Diesel Knock".
There is power and efficiency loss along with rough running of engine is observed due to diesel knock. In severe cases it may wreck the engine.
A considerable amount of air -fuel mixture may ignite at the same instant and result in a combustion knock or heavy thud rather than pink. While it is end mixture which knocks in the spark ignition engine (petrol engine) it may fairly large part or parts of the mixture, which knock in compression ignition engine.
To prevent diesel knock, following important methods can be used very effectively.
01) Add 1% of ethyl nitrate or any nitrate to accelerate the combustion of fuel. This process in known as "Doping" and reduce delay period considerably and hence prevent diesel knock.
02) For spontaneous ignition of the fuel, we require much higher temperature this can be achieved by raising the compression ratio. The rate of pressure rise increases resulting in smooth running of the engine. If compression ratio increased in petrol engine, the engine is more liable to detonate, but in diesel engine it reduce the diesel knock.
03) Diesel knock can be reduce by increasing the turbulence of the compressed air injected promotes homogeneous mixture by stripping the fuel from the spray.
04) Arrange the fuel injector in such a way that it should start injecting only a small quantity of fuel in starting of the engine. If we increase the injection pressure, which encourages the atomization of fuel and prevent knock.
05) By raising the temperature of the coolant that of the intake air as well as cylinder head and combustion chamber.
06) By increasing the inlet pressure of air (Supercharging) we can prevent diesel knock.
Many times we noted this sudden noise but not aware about the phenomenon behind this, now above description will clear the doubt about knock in your automotive engine. What you say?
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There is power and efficiency loss along with rough running of engine is observed due to diesel knock. In severe cases it may wreck the engine.
A considerable amount of air -fuel mixture may ignite at the same instant and result in a combustion knock or heavy thud rather than pink. While it is end mixture which knocks in the spark ignition engine (petrol engine) it may fairly large part or parts of the mixture, which knock in compression ignition engine.
To prevent diesel knock, following important methods can be used very effectively.
01) Add 1% of ethyl nitrate or any nitrate to accelerate the combustion of fuel. This process in known as "Doping" and reduce delay period considerably and hence prevent diesel knock.
02) For spontaneous ignition of the fuel, we require much higher temperature this can be achieved by raising the compression ratio. The rate of pressure rise increases resulting in smooth running of the engine. If compression ratio increased in petrol engine, the engine is more liable to detonate, but in diesel engine it reduce the diesel knock.
03) Diesel knock can be reduce by increasing the turbulence of the compressed air injected promotes homogeneous mixture by stripping the fuel from the spray.
04) Arrange the fuel injector in such a way that it should start injecting only a small quantity of fuel in starting of the engine. If we increase the injection pressure, which encourages the atomization of fuel and prevent knock.
05) By raising the temperature of the coolant that of the intake air as well as cylinder head and combustion chamber.
06) By increasing the inlet pressure of air (Supercharging) we can prevent diesel knock.
Many times we noted this sudden noise but not aware about the phenomenon behind this, now above description will clear the doubt about knock in your automotive engine. What you say?
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Friday
10 Important Terms Used In Internal Combustion Engine.
For the better knowledge of internal combustion engine every one must know about the following terms,
01) Carburetion: -
The process of breaking up the fuel into minute particles and mixing it with air is called "Carburetion". This process is mostly used in the internal combustion engine, which have low compression ratio and which use highly volatile liquid fuels such as petrol. The process of breaking up fuel in minute particles is known as "Atomization". Carburettor is the device where all the carburetion takes place.
02) Scavenging: -
The process of removing burnt exhaust gases from the combustion chamber of the engine cylinder is known as "Scavenging". In four-stroke cycle engine, the piston pushes the burnt gases to exhaust manifold during its exhaust stroke. In the two-stroke cycle engine a blast of fresh charge is made to enter at higher Velocity into a combustion chamber at the end of working stroke and thus drives out burnt exhaust gases.
03) Compensation: -
The process of providing additional fuel or reducing the fuel by certain means to correct the mixture strength to meet the varying nature of speeds and load on the engines is known as "Compensation". This process is mostly used in simple carburettor specially used for automotive purposes.
04) Firing Order: -
The sequences in which firing or power impulses occur in an internal combustion engine are called "Firing Order". The firing order should be such that there is always a proper balance and it does not cause vibrations.
05) Detonation: -
Some sudden and violent knocks are experienced in internal combustion engine at sometimes. This knocks are known by "Detonation". This knock is set up by a high-pressure wave giving a loud pulsating noise as it strikes against the cylinder walls, cylinder head and piston. It should be noted that detonation is not pre-ignition but something, which occur after the spark, has started the ignition.
06) Doping: -
The process of adding small quantity of Tetraethyl lead to suppress the detonation in petrol engine is called "Doping". If the tetraethyl lead used in large proportion, there are chances of engine damage due to deposition of lead oxide in the combustion chamber.
07) Diesel Knock: -
A high-pressure wave set up in compression ignition engine (Diesel Engine), which causes knocks. This knock is called as "Diesel knock". It badly affects the engine efficiency and power drop; also engine runs very rough due to diesel knock.
08) Dissociation: -
If a gas or mixture of gases is heated to very high temperature, the vibrating molecules of different gases make violent encounters resulting in splitting up of the compound molecules into smaller molecules which recombine to form their compound molecules as the temperature lowered. The phenomenon is called "Dissociation". The dissociation is mainly due to breaking up of carbon dioxide into carbon monoxide and oxygen.
09) Supercharging: -
The process of increasing the weight or density of air-fuel mixture or compressed air, induced into the cylinder during the induction stroke is known as "Supercharging". This is achieved by a separate compressor and known as supercharger or blower.
10) Turbulence: -
When the atomised fuel injected into the combustion chamber of compression ignition engine may be burnt efficiently there should be a high relative velocity between the air and fuel so that a thorough mixing takes place. This is achieved by "Turbulence".
I hope this will help you to get better knowledge about your engine and can increase the performance of engine.
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01) Carburetion: -
The process of breaking up the fuel into minute particles and mixing it with air is called "Carburetion". This process is mostly used in the internal combustion engine, which have low compression ratio and which use highly volatile liquid fuels such as petrol. The process of breaking up fuel in minute particles is known as "Atomization". Carburettor is the device where all the carburetion takes place.
02) Scavenging: -
The process of removing burnt exhaust gases from the combustion chamber of the engine cylinder is known as "Scavenging". In four-stroke cycle engine, the piston pushes the burnt gases to exhaust manifold during its exhaust stroke. In the two-stroke cycle engine a blast of fresh charge is made to enter at higher Velocity into a combustion chamber at the end of working stroke and thus drives out burnt exhaust gases.
03) Compensation: -
The process of providing additional fuel or reducing the fuel by certain means to correct the mixture strength to meet the varying nature of speeds and load on the engines is known as "Compensation". This process is mostly used in simple carburettor specially used for automotive purposes.
04) Firing Order: -
The sequences in which firing or power impulses occur in an internal combustion engine are called "Firing Order". The firing order should be such that there is always a proper balance and it does not cause vibrations.
05) Detonation: -
Some sudden and violent knocks are experienced in internal combustion engine at sometimes. This knocks are known by "Detonation". This knock is set up by a high-pressure wave giving a loud pulsating noise as it strikes against the cylinder walls, cylinder head and piston. It should be noted that detonation is not pre-ignition but something, which occur after the spark, has started the ignition.
06) Doping: -
The process of adding small quantity of Tetraethyl lead to suppress the detonation in petrol engine is called "Doping". If the tetraethyl lead used in large proportion, there are chances of engine damage due to deposition of lead oxide in the combustion chamber.
07) Diesel Knock: -
A high-pressure wave set up in compression ignition engine (Diesel Engine), which causes knocks. This knock is called as "Diesel knock". It badly affects the engine efficiency and power drop; also engine runs very rough due to diesel knock.
08) Dissociation: -
If a gas or mixture of gases is heated to very high temperature, the vibrating molecules of different gases make violent encounters resulting in splitting up of the compound molecules into smaller molecules which recombine to form their compound molecules as the temperature lowered. The phenomenon is called "Dissociation". The dissociation is mainly due to breaking up of carbon dioxide into carbon monoxide and oxygen.
09) Supercharging: -
The process of increasing the weight or density of air-fuel mixture or compressed air, induced into the cylinder during the induction stroke is known as "Supercharging". This is achieved by a separate compressor and known as supercharger or blower.
10) Turbulence: -
When the atomised fuel injected into the combustion chamber of compression ignition engine may be burnt efficiently there should be a high relative velocity between the air and fuel so that a thorough mixing takes place. This is achieved by "Turbulence".
I hope this will help you to get better knowledge about your engine and can increase the performance of engine.
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Thursday
How To Cool Exhaust Valve Of Internal Combustion Engine?
Various strokes are performed in internal combustion engine to get work done up to our requirement. To complete suction and exhaust stroke, there are some valves used which are known as suction valve and exhaust valve. Suction valve allow the fresh charge of air-fuel mixture inside the cylinder, where it is compressed and burnt by other parts. Due to combustion process large heat is developed and it makes exhaust valve very hot as burnt gases are escape from this valve to atmosphere.
As exhaust valve of an internal combustion engine is subjected to very high temperatures, it is therefore necessary to cool it down for the better performance of engine. Following ways can cool exhaust valve in,
01) By providing a suitable number of jets on the channel through which cold water directs from the radiator are pumped. The water flowing from these jets or nozzles in contact with the areas adjacent to the exhaust valve and exhaust port, which are thus cooled.
02) An improved Cooling can also be achieved if cooling jackets are provided more elaborately near exhaust valve and exhaust port.
03) By filling a part of the stem of the exhaust valve by sodium, we can achieve better Cooling. The solid melts at high temperature (Near about 750 degree centigrade) and is thrown up and down due to the motion of the exhaust valve. The heat from the hot region is thus conveyed to the comparatively cold region. Sodium is good conductor of heat and has a high boiling point. (750 degree centigrade)
It is more important to keep all the parts in workable limits for the better efficiency of the internal combustion engine. As a mechanical engineer, we have to take care of all our various machines and components.
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As exhaust valve of an internal combustion engine is subjected to very high temperatures, it is therefore necessary to cool it down for the better performance of engine. Following ways can cool exhaust valve in,
01) By providing a suitable number of jets on the channel through which cold water directs from the radiator are pumped. The water flowing from these jets or nozzles in contact with the areas adjacent to the exhaust valve and exhaust port, which are thus cooled.
02) An improved Cooling can also be achieved if cooling jackets are provided more elaborately near exhaust valve and exhaust port.
03) By filling a part of the stem of the exhaust valve by sodium, we can achieve better Cooling. The solid melts at high temperature (Near about 750 degree centigrade) and is thrown up and down due to the motion of the exhaust valve. The heat from the hot region is thus conveyed to the comparatively cold region. Sodium is good conductor of heat and has a high boiling point. (750 degree centigrade)
It is more important to keep all the parts in workable limits for the better efficiency of the internal combustion engine. As a mechanical engineer, we have to take care of all our various machines and components.
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Sunday
Factors Affecting Detonation In Internal Combustion Engine.
In an internal combustion engine cylinder sometime sudden and violent knocks are experienced, this is known as "Detonation". This knock is set up by a high pressure wave giving loud pulsating noise as it strikes against cylinder walls, cylinder head and piston.
A mild detonation will simply heat the engine but if the detonation is severe, it may even result in fracture of the piston or other damages to the engine.Detonation also results in increased carbon deposits. If detonation continue for a long time it may overheat the cylinder and spark plug so as to ignite the Charge even before sparking and lead to pre-ignition. These are the disadvantages of detonation. A properly designed combustion chamber will reduce detonation considerably.
Following are the main factors, which affects detonation,
01) The fuel used in internal combustion engine will considerably effects on the chances of detonation. Alcohol and benzol do not cause detonation but it can not be use due its low calorific value and other objections to use as fuel. Again alcohol cannot blend with petrol in the presence of water.
02) The detonation is also promoted by increase in compression ratio. The compression ratio at which detonation just occurs is known as the Highest Useful Compression Ratio. Higher the compression ratio higher the chances of detonation and lower the output.
03) If the carbon deposits are in the cylinder and used excessive sparking temperature, the detonation will increased rapidly.
04) The position of the spark plug in a combustion chamber determines the distance the flame has to travel in order to reach the detonation zone. More the distance more the chances of detonation. A centrally placed spark plug works better. Spark plug must be placed near to exhaust valve but the exhaust must be located away from detonating zone.
05) Higher temperature of the walls of combustion chamber tends to raise the temperature combustion chamber tending to raise the temperature of Detonation zone.
06) The rate at which the combustion of the portion of the fuel, which is first to ignite immediately after the application of the spark, also affects detonation.
Hence from the above description we must know, the detonation is dangerous for internal combustion engine and must be removed or reduced.
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A mild detonation will simply heat the engine but if the detonation is severe, it may even result in fracture of the piston or other damages to the engine.Detonation also results in increased carbon deposits. If detonation continue for a long time it may overheat the cylinder and spark plug so as to ignite the Charge even before sparking and lead to pre-ignition. These are the disadvantages of detonation. A properly designed combustion chamber will reduce detonation considerably.
Following are the main factors, which affects detonation,
01) The fuel used in internal combustion engine will considerably effects on the chances of detonation. Alcohol and benzol do not cause detonation but it can not be use due its low calorific value and other objections to use as fuel. Again alcohol cannot blend with petrol in the presence of water.
02) The detonation is also promoted by increase in compression ratio. The compression ratio at which detonation just occurs is known as the Highest Useful Compression Ratio. Higher the compression ratio higher the chances of detonation and lower the output.
03) If the carbon deposits are in the cylinder and used excessive sparking temperature, the detonation will increased rapidly.
04) The position of the spark plug in a combustion chamber determines the distance the flame has to travel in order to reach the detonation zone. More the distance more the chances of detonation. A centrally placed spark plug works better. Spark plug must be placed near to exhaust valve but the exhaust must be located away from detonating zone.
05) Higher temperature of the walls of combustion chamber tends to raise the temperature combustion chamber tending to raise the temperature of Detonation zone.
06) The rate at which the combustion of the portion of the fuel, which is first to ignite immediately after the application of the spark, also affects detonation.
Hence from the above description we must know, the detonation is dangerous for internal combustion engine and must be removed or reduced.
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Saturday
Various Parts Of Water Cooling System.
Internal combustion Engine can be cooled by air-cooling or water-cooling method. Various Water Cooling Methods Of I.C.Engine is covered in earlier post, which you can refer to know in details. Impeller Thermosyphon system has required following components to perform the cooling action.
01) Radiator:-
The function of the radiator is to cool down the hot water from engine. It consists of a large number of vertical tubes through which water flows down. The temperature of water is reduced appreciably by drawing the air through spaces between the radiator tubes with the help of fan, which is mounted on the impeller spindle driven by a suitable pulley arrangement.
There are many types of radiator tubes are used in field but the most common is tubular type. It consists of a large number of circular brass tubes pressed into a number of suitable punched parallel brass fins. The tubes are tinned to guard against corrosion and are staggered. The main disadvantage of this design is, a greater inconvenience to repair any damaged tubes. Still it is cheaper than the honeycomb type design due its initial cost. The honeycomb radiator is used in racing cars.
The water used for cooling must be soft because the deposits given out by hard water act as insulator of heat between the cylinder walls and the radiator water, but in case where soft water is not available, 0.03 kilogram of sodium bichromate should be added for every 13 kilogram of water.
The maximum temperature, which can be allowed in a radiator, is 3 degree centigrade below boiling point of water. The ratio of the observed temperature difference to the greatest permissible temperature difference in a radiator is called suitability of of the radiator.
Some radiators are equipped with a heater, which not only averts the danger of freezing of water but also greatly reduces the time taken by the engine to reach its normal operating temperature.
02) Fan and Pump:-
The pump increases the velocity of water through the system. The fan, which draws air through the radiator spaces, is usually mounted on the same spindle as that of the impeller having widely spaced vanes to facilitate the flow of water through it is case of failure.
The bottom of the radiator is connected to the suction side of the pump. The power is transmitted to the pump spindle from a pulley mounted on the end of the camshaft or crankshaft.
03) Thermostat:-
A thermostat fitted in such a manner that it prevents the flow of water below certain temperature, from engine to the radiator. The "Bellows Type" thermostat is generally used.
The disc is connected to the bronze bellow through link. The bellows are sealed against the atmosphere and contain alcohol inside it. On cooling, the bellows contract due to the condensation of alcohol vapour into liquid. The disc therefore closes the passage, which could be reopened only if a certain minimum temperature of the circulating water is reached which expands the bellow due to evaporation of the alcohol liquid inside. Generally, a thermostat does not allow the water to flow below 70 degree centigrade.
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01) Radiator:-
The function of the radiator is to cool down the hot water from engine. It consists of a large number of vertical tubes through which water flows down. The temperature of water is reduced appreciably by drawing the air through spaces between the radiator tubes with the help of fan, which is mounted on the impeller spindle driven by a suitable pulley arrangement.
There are many types of radiator tubes are used in field but the most common is tubular type. It consists of a large number of circular brass tubes pressed into a number of suitable punched parallel brass fins. The tubes are tinned to guard against corrosion and are staggered. The main disadvantage of this design is, a greater inconvenience to repair any damaged tubes. Still it is cheaper than the honeycomb type design due its initial cost. The honeycomb radiator is used in racing cars.
The water used for cooling must be soft because the deposits given out by hard water act as insulator of heat between the cylinder walls and the radiator water, but in case where soft water is not available, 0.03 kilogram of sodium bichromate should be added for every 13 kilogram of water.
The maximum temperature, which can be allowed in a radiator, is 3 degree centigrade below boiling point of water. The ratio of the observed temperature difference to the greatest permissible temperature difference in a radiator is called suitability of of the radiator.
Some radiators are equipped with a heater, which not only averts the danger of freezing of water but also greatly reduces the time taken by the engine to reach its normal operating temperature.
02) Fan and Pump:-
The pump increases the velocity of water through the system. The fan, which draws air through the radiator spaces, is usually mounted on the same spindle as that of the impeller having widely spaced vanes to facilitate the flow of water through it is case of failure.
The bottom of the radiator is connected to the suction side of the pump. The power is transmitted to the pump spindle from a pulley mounted on the end of the camshaft or crankshaft.
03) Thermostat:-
A thermostat fitted in such a manner that it prevents the flow of water below certain temperature, from engine to the radiator. The "Bellows Type" thermostat is generally used.
The disc is connected to the bronze bellow through link. The bellows are sealed against the atmosphere and contain alcohol inside it. On cooling, the bellows contract due to the condensation of alcohol vapour into liquid. The disc therefore closes the passage, which could be reopened only if a certain minimum temperature of the circulating water is reached which expands the bellow due to evaporation of the alcohol liquid inside. Generally, a thermostat does not allow the water to flow below 70 degree centigrade.
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Wednesday
Various Water Cooling Methods Of I.C.Engine
To pass some of the heat generated due to combustion in the cylinder of internal combustion engine, air-cooling or water-cooling methods are used. The Details about air-cooling were covered in previous post (Air Cooling Of Internal Combustion Engine.). In this post you will find some more methods of water-cooling.
In water-cooling method, the advantage of superior convective and conductive properties of water is used. Water is circulated continuously through the Cylinder with an annular space known as Water Jacket. To avoid unequal expansion in the cylinder bore and burning of lubricating oil, the water jackets are so designed that they will cover the entire length of piston stroke.
For the cleaning of water jackets in large cylinders, cleaning doors are provided. This method is also employed in large reciprocating air compressor where we have to add cooling tower in addition to cool the circulating water.
Water Cooling can be done by any of the following methods,
01) Direct Method:-
In this method, water from a storage tank is directly supplied through an inlet valve to the engine cylinder. The hot water is simply discharged and not cooled for reuse. It is suitable for large industrial units and where plenty of water is easily available.
02) Thermosyphon Method:-
In this method, hot water from engine cylinder flows towards radiator, which has comparatively cold water, and get cool down.
In order to ensure that the coolest water is always made available to the water jackets the latter should be located at as low a level as possible with respect To the radiator.
This system is useful due its simplicity and automatic operation, but there is disadvantage of water freezing in cold weather condition. We have to use large Quantity of water, as there is slow rate of circulation observed.
03) Impeller Thermosyphon Method:-
Here the flow of water takes place by convection assisted by a pump. The latter is made non-positive type, which even when stationary; allows the flow of water to take place. Thus when the working of pump fails water can still circulate on the thermosyphon system.
In its simplest form, water flow from radiator to engine and back to radiator. A thermostat is employed in system, which prevents the flow of water below a certain temperature, from the engine to the radiator. This we have to do to acquire some of the temperature at starting of the engine.
This system has three major parts, (The details about this parts will be covered in coming post.)
01) Radiator
02) Fan and Pump
03) Thermostat
04) Full Pump Circulation Method:-
In this method, a positive supply of water by a centrifugal pump placed in the system. This system works on higher Velocity of circulating water due to which less quantity of water is required hence we can use smaller radiator.
In some designs the piston is cooled by oil squirted against the piston crown underside through a nozzle located in the connecting rod small end.
05) Evaporative Cooling Method:-
In this method, the engine may be cooled by evaporating the water in the cylinder jackets, into the steam, which absorbs Large quantity of heat and raise to the top of the engine from where it flows into a tank at the bottom of the radiator and then flows upwards and gets Condensed before reaching the top.
Due to large quantity of latent heat absorbed during evaporation of water into steam the weight of the circulating water is only 40% of that in other water Cooling methods. Hence smaller radiator can be employed.
This system is quite useful where plenty of water is not available. The higher running temperature no doubt reduces the friction in the piston but the volumetric efficiency is reduced and the engine is also liable to detonate.
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In water-cooling method, the advantage of superior convective and conductive properties of water is used. Water is circulated continuously through the Cylinder with an annular space known as Water Jacket. To avoid unequal expansion in the cylinder bore and burning of lubricating oil, the water jackets are so designed that they will cover the entire length of piston stroke.
For the cleaning of water jackets in large cylinders, cleaning doors are provided. This method is also employed in large reciprocating air compressor where we have to add cooling tower in addition to cool the circulating water.
Water Cooling can be done by any of the following methods,
01) Direct Method:-
In this method, water from a storage tank is directly supplied through an inlet valve to the engine cylinder. The hot water is simply discharged and not cooled for reuse. It is suitable for large industrial units and where plenty of water is easily available.
02) Thermosyphon Method:-
In this method, hot water from engine cylinder flows towards radiator, which has comparatively cold water, and get cool down.
In order to ensure that the coolest water is always made available to the water jackets the latter should be located at as low a level as possible with respect To the radiator.
This system is useful due its simplicity and automatic operation, but there is disadvantage of water freezing in cold weather condition. We have to use large Quantity of water, as there is slow rate of circulation observed.
03) Impeller Thermosyphon Method:-
Here the flow of water takes place by convection assisted by a pump. The latter is made non-positive type, which even when stationary; allows the flow of water to take place. Thus when the working of pump fails water can still circulate on the thermosyphon system.
In its simplest form, water flow from radiator to engine and back to radiator. A thermostat is employed in system, which prevents the flow of water below a certain temperature, from the engine to the radiator. This we have to do to acquire some of the temperature at starting of the engine.
This system has three major parts, (The details about this parts will be covered in coming post.)
01) Radiator
02) Fan and Pump
03) Thermostat
04) Full Pump Circulation Method:-
In this method, a positive supply of water by a centrifugal pump placed in the system. This system works on higher Velocity of circulating water due to which less quantity of water is required hence we can use smaller radiator.
In some designs the piston is cooled by oil squirted against the piston crown underside through a nozzle located in the connecting rod small end.
05) Evaporative Cooling Method:-
In this method, the engine may be cooled by evaporating the water in the cylinder jackets, into the steam, which absorbs Large quantity of heat and raise to the top of the engine from where it flows into a tank at the bottom of the radiator and then flows upwards and gets Condensed before reaching the top.
Due to large quantity of latent heat absorbed during evaporation of water into steam the weight of the circulating water is only 40% of that in other water Cooling methods. Hence smaller radiator can be employed.
This system is quite useful where plenty of water is not available. The higher running temperature no doubt reduces the friction in the piston but the volumetric efficiency is reduced and the engine is also liable to detonate.
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Tuesday
Air Cooling Of Internal Combustion Engine.
When the combustion of fuel takes place in cylinder of internal combustion engine, a very high temperature is developed. It is, therefore necessary to extract some of the heat from cylinder to atmosphere. It will avoid damage to the cylinder and piston. Heat also burns lubrication oil and form carbon. There is possibility of seizure of piston inside the cylinder, which will lead to more break down and repairing cost. To avoid this, cooling is necessary.
Air Cooling is mostly used in motorcycles, scooters where the forward motion of the machine gives a good velocity of air to cool the engine. Air Cooling is also provided in small industrial engines. In bigger unit a circulating fan is employed. But the fan absorbs 5% of the power developed by the engine.
Air Cooling is the simplest method in which the heat is carried out by the air flowing over and around the engine cylinder. In this system a current of air is Made to blow past the outside of cylinder barrel whose outer surface is area has been considerably increased by providing radiating fins. The cooling fins are arranged so that they are perpendicular to the axis of the cylinder.
In this system there is no such problem as corrosion or clogging of the radiator occurs, since there is no radiator is used (Radiator is used in water cooled Engines). There is also a complete absence of water freezing in cold weather conditions as in water-cooled engine.
Air Cooling is particularly advantageous where there are extreme climatic conditions as arctic or where there is lack of water as in deserts. It gives less Starting troubles.
Beside above advantages, this cooling system has some disadvantages also. Air-cooled engines on the average have limited size, non-uniform cooling and Higher working temperatures. They also produce more noise, gives a less petrol economy, lower maximum allowable compression ratio and lower output.
In next post, you will come to know about water-cooling of internal combustion engine.
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Air Cooling is mostly used in motorcycles, scooters where the forward motion of the machine gives a good velocity of air to cool the engine. Air Cooling is also provided in small industrial engines. In bigger unit a circulating fan is employed. But the fan absorbs 5% of the power developed by the engine.
Air Cooling is the simplest method in which the heat is carried out by the air flowing over and around the engine cylinder. In this system a current of air is Made to blow past the outside of cylinder barrel whose outer surface is area has been considerably increased by providing radiating fins. The cooling fins are arranged so that they are perpendicular to the axis of the cylinder.
In this system there is no such problem as corrosion or clogging of the radiator occurs, since there is no radiator is used (Radiator is used in water cooled Engines). There is also a complete absence of water freezing in cold weather conditions as in water-cooled engine.
Air Cooling is particularly advantageous where there are extreme climatic conditions as arctic or where there is lack of water as in deserts. It gives less Starting troubles.
Beside above advantages, this cooling system has some disadvantages also. Air-cooled engines on the average have limited size, non-uniform cooling and Higher working temperatures. They also produce more noise, gives a less petrol economy, lower maximum allowable compression ratio and lower output.
In next post, you will come to know about water-cooling of internal combustion engine.
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Common Defects In Water Cooling System And Its Rectifications.
The heat is generated in engine due to combustion of air-fuel mixture that is why the Necessity Of Cooling In Internal Combustion Engine is required.This is done by air or water.Each cooling system has its own advantages and disadvantages,the most common defects occurring in water cooling system are,
01) Loss Of Coolant:-
Water leakage and water evaporation is the main cause of water loss from the cooling system.Water leakage may occur due to faulty head gasket,loose cylinder head,cracked head or engine block,loosening of hose clamps and radiator pipe leaks.
To stop such a leakage,head gasket may be replaced,hose clamp may be tightened and radiator pipe soldered.To compensate the loss of water due to evaporation can be done by filling the water at correct level in radiator.
02) Overheating Of Coolant:-
This is caused due to rusting,sealing of water jackets and radiator, defective hose,defective water pump,defective thermostat,slipping of fan belt,blocking of air passage in the radiator and loss of cooling water.
The heat transfer from the wall of the cylinder to the coolant is mostly effected due to rusting and scaling takes place on the walls.This may be removed by washing the cavities with ordinary washing soda or some other chemical and reverse flushing.
Sometimes worn out hose material goes into the water passage and accumulates there restricting the flow of coolant.Replace the defective hose at earliest.Repair defective water pump and replace defective thermostat Will solve the problem.The circulation of air is effected by slipping of fan belt.To remove this defect,tightened the fan belt as per requirement or replace if required.Remove the greasy material if found on pulley grooves.
Clean the radiator by blowing air under pressure from fan side.If there is loss of coolant due to any reason,the water must be filled in radiator up to required level without hesitation.
03) Over cooling Of Coolant:-
Over Cooling is generally caused by a thermostat that opens too early or remain open at all times.In some cases,it is observed that there is no thermostat employed or missing.If By-Pass valve remain open at all time,it results the over cooling of water.to avoid over cooling,the defective thermostat must be replaced and early action should be taken to close the By-Pass valve.
The circulation of water may be effected due to freezing of cooling water as it blocks the circulation passage.To overcome this problem,the engine must be run idle for some time until it attains the proper temperature.
04) Water Circulating Pump Noise:-
Water pump gives noise due to dry bearing or bushing,loose pulley on the pump shaft,loose impeller on the shaft etc.The proper cause of trouble may be found out and rectified.
05) Defective Temperature Gauge:-
If the temperature gauge on the panel is suspected to be giving incorrect readings the temperature of the cooling water be measured by inserting a thermometer in the radiator upper tank and then compared with the reading of the gauge.If the gauge is found defective it should be replaced.
There are may be some more defects which you know better than me,add it by comment.
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Construction Of Spark Plug Used In Automotive Engine.
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01) Loss Of Coolant:-
Water leakage and water evaporation is the main cause of water loss from the cooling system.Water leakage may occur due to faulty head gasket,loose cylinder head,cracked head or engine block,loosening of hose clamps and radiator pipe leaks.
To stop such a leakage,head gasket may be replaced,hose clamp may be tightened and radiator pipe soldered.To compensate the loss of water due to evaporation can be done by filling the water at correct level in radiator.
02) Overheating Of Coolant:-
This is caused due to rusting,sealing of water jackets and radiator, defective hose,defective water pump,defective thermostat,slipping of fan belt,blocking of air passage in the radiator and loss of cooling water.
The heat transfer from the wall of the cylinder to the coolant is mostly effected due to rusting and scaling takes place on the walls.This may be removed by washing the cavities with ordinary washing soda or some other chemical and reverse flushing.
Sometimes worn out hose material goes into the water passage and accumulates there restricting the flow of coolant.Replace the defective hose at earliest.Repair defective water pump and replace defective thermostat Will solve the problem.The circulation of air is effected by slipping of fan belt.To remove this defect,tightened the fan belt as per requirement or replace if required.Remove the greasy material if found on pulley grooves.
Clean the radiator by blowing air under pressure from fan side.If there is loss of coolant due to any reason,the water must be filled in radiator up to required level without hesitation.
03) Over cooling Of Coolant:-
Over Cooling is generally caused by a thermostat that opens too early or remain open at all times.In some cases,it is observed that there is no thermostat employed or missing.If By-Pass valve remain open at all time,it results the over cooling of water.to avoid over cooling,the defective thermostat must be replaced and early action should be taken to close the By-Pass valve.
The circulation of water may be effected due to freezing of cooling water as it blocks the circulation passage.To overcome this problem,the engine must be run idle for some time until it attains the proper temperature.
04) Water Circulating Pump Noise:-
Water pump gives noise due to dry bearing or bushing,loose pulley on the pump shaft,loose impeller on the shaft etc.The proper cause of trouble may be found out and rectified.
05) Defective Temperature Gauge:-
If the temperature gauge on the panel is suspected to be giving incorrect readings the temperature of the cooling water be measured by inserting a thermometer in the radiator upper tank and then compared with the reading of the gauge.If the gauge is found defective it should be replaced.
There are may be some more defects which you know better than me,add it by comment.
You may also interested in following.........
Construction Of Spark Plug Used In Automotive Engine.
Different Ignition Systems Of Four Cylinder Engine.
Various Parts And Its Function In Internal Combustion Engine.
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