Car Air-conditioning System

       *Car Air-conditioning System

CAR AIR-CONDITIONING SYSTEMS Some of the important air-conditioning systems used and manufactured by Ford and general Motors are given here:

Ford Air-conditioning System:-

This system uses a factory installed unit. It has the blower, heat exchangers and housing on the engine side of the finned wall. A thermostat expansion valve with a built in sight glass and a two cylinder compressor usually mounted horizontally is used. There are two service valves mounted on the head of the compressor. A thermostat having its sensitive bulb clamped to the evaporator fins operates the compressor magnetic clutch. For providing the air circulation, duct dampers operated by a vacuum activating system are used.

General Motors Air-conditioning System:-

This system uses a rotary compressor. To control the evaporator pressure and exhaust muffler on the compressor, a pressure operated altitude valve is used. Basic refrigeration circuit of automatic air-conditioning system consists of an electrically controlled heating system, air cooling system and air duct flow using a vacuum activator system for controlling the dampers and the valves. Three temperature sensors (one outside the car, one inside the car and another in the discharge disc) connected to an amplifier and a programmer are used in this system.

Major components and refrigerant flow of the air conditioning system for Maruti MF 410 vehicle is shown

in picture

The recent research has called for a ban on 'R134a' refrigerantalso and to replace the same with CO2. In addition to the environmental benefits, CO, as a refrigerant has also the following advantages: 

1. 20% less fuel consumption than today's systems, due to better average efficiency throughout the year.

2. Cooling capacity of the present air conditioning systems is limited by the compressor piston displacement, which itself is limited by the insufficient space in the engine compartment. CO, air conditioning systems only need about 13% of the volume flow of an 'R134a' system, making it possible to use smaller compressors enabling CO, system to cool the passenger compartment faster.

3. As the process is also reversible, unlike today's air conditioners, it also has a heat pump function. This can be used to heat up the vehicle interior very quickly. replacing the electric supplemental heaters that are common with modern direct-injection diesel engines.

It is expected that due to the above clear advantages, CO₂ technology will start replacing present air conditioners in 2007. 'Luk' has specialized in the development of compressors for the new technology.

Important tips for the maintenance of car AC system are:

1. Clean the condenser during normal servicing. Clogged condenser can result in frequent AC tripping and lesser cooling.

2. Maintain correct refrigerant level. Less refrigerant would result in less cooling. Excessive refrigerant would also result in lesser cooling and excessive tripping.

3. Top up the compressor with adequate oil.

4. Clean the evaporator periodically. Clogging of evaporator would cause poor airflow and hence lesser cooling.

5. Maintain proper belt tension. A loose belt will slip whereas overtight belt would cause noise and premature compressor failure.

Important precautions while using car AC systems are:

1. Do not use AC with fresh air mode open always since this mode is for occasional use just to release the air in circulation for a long time. Frequent use of fresh air mode may result in the accumulation of dust and clogging of evaporators.

2. Never operate AC with heater on.

3. Never run AC without refrigerant, otherwise compressor may cease. 4. Do not leak-test AC with more than 2 MPa pressure,

higher pressure can damage the components.

5. Do not leave AC joints open, which may cause the moisture to enter the system. 6. Do not charge the refrigerant in the AC system before flushing.

 7. Do not switch on the AC at high speeds, which may result in the ceasing of compressor.

Bus Air-conditioning:-

Air-conditioning system used for a bus is of standard design. Its condensing unit is very compact and is generally installed in the bus in such a way that for servicing it is readily accessible. Due to large size of the unit, a separate gasoline engine with an automatic starting device is used to drive the compressor. To permit sliding of the condensing unit out of the bus body during servicing the condensing unit is generally mounted on rails with flexible suction and liquid lines. Standard thermostat expansion valves refrigerant controls and air cooled condensers are used. Evaporator used are finned blower. The ducts, usually one on each side of the bus. run between a false ceiling and roof of the bus. Grills controlled by passengers are provided at their seats.

TRUCK AIR-CONDITIONING:-

Due to varying conditions of heating, ventilating, cooling and dehumidification in the atmosphere at various places, long distance hauling trucks and truck tractors carrying perishable products are air-conditioned. Air-conditioned equipment used is of the "hang on" type. It is generally installed after the body has been made. Generally, two evaporators, one on the cab and other for product compartment, are used. A remote condenser mounted on the roof of the cab is generally used. To enable the radiator to operate at fuel efficiency, it helps to remove the condenser from infront of the radiator.

ROVAC AIR-CONDITIONER:-

This system of air-conditioning of the car uses air. It is yet to be commercially deployed in cars. The system has been designed by Dr. Thomas C. Edwards. It is rotary vane air cycle air-conditioning system. The system has the following distinguishing features:

1. It does not use Freon gas. Hence, there is no high pressure gas to store, seal against leaks or replace. The system is thus much simpler.

2. It has high coefficients of performance when compared with conventional type. This makes the system to consume less power of engine and hence there is fuel economy.

3. It gives instant cold. There is no detectable time lag from start up to cold air.

4. It gives instant heat. This makes the heat available from intermediate coils for defrosting long before the engine gets warmed up.

ROVAC system alternately compresses and expands the air. The conventional sealed units make use of reversed Rankine cycle with a gas-to- liquid and back-to-gas phase change. ROVAC uses no phase change like the conventional sealed units, except for the incidental moisture normally present in the air. Edwards calls this a reversed Brayton cycle.

The oval shaped housing acts as a compressor on the inlet side and an expander on the exhaust side. The air enters the compressor at atmospheric pressure and passenger compartment temperature. This air is compressed to a pressure of about 21N/cm and temperature of about 140° C. From the compressor, the air travels through heat exchanger which is provided with fins. In fact, the heat exchanger has large tubes. The inside air is cooled by the outside air flowing past the tubes. This drops the temperature of inside air to 45° C. There is no appreciable change in the pressure.

Now, this air is lead through the expander where the pressure drops to atmospheric and the temperature of the air drops to about 6° C. This air is circulated inside the passenger compartment, thus cooling the occupants. The cycle gets repeated.

It may be mentioned that the ROVAC can be designed to produce outlet temperatures well below freezing point. Modulation and moisture control is handled in the distribution ducts. It is worth mentioning that when the hot air is passing through the expander, it returns part of its heat energy to the vaned rotor, thus saving engine power.

  *Car Air-conditioning System

Air- Conditioning System Components

 Air- Conditioning System Components

AIR-CONDITIONING SYSTEM COMPONENTS:-

A typical automobile air-conditioning system. It includes compressor, magnetic clutch, condenser, receiver drier, strainer, expansion valve, evaporator, blower and the air distributor system. The evaporator and the expansion valves are located inside the passenger compartment, the other components usually put under the car hood. The components and the behavior of the refrigerant in them are briefly described here:

1.Compressor:-  The compressor used in the automobile air conditioning system is belt-driven from the engine crank shaft pulley. A magnetic clutch engages the compressor shaft. When the voltage is applied to the compressor clutch coil, the magnetic force so generated locks the clutch plate and the pulley together as one unit; and then the compressor shaft is turned with the pulley. Springs in clutch plate and hub assembly automatically moves the plate away from the pulley when the voltage to the clutch coil is interrupted. This causes the compressor to stop. Most compressors used are piston type compressors with one or two cylinders. The compressor draws in low pressure, high temperature vaporized refrigerant and compresses it to high pressures. The refrigerant never reaches its liquid state in the compressor. The compressor compresses the refrigerant to maximum of about 200 N/cm² and 100° C; and pushes it along the condenser.

The refrigerant used is a chlorine-fluorine mixture known by the trade name of 'Freon-12'. It has a boiling point of -22° at atmospheric pressure and exerts a vapor pressure of 125 N/cm2 at 133° F.

2. Magnetic clutch:- The electrically controlled magnetic clutch is housed in pulley assembly and the system selector switch controlling the clutch operation is mounted on the control panel inside the passenger compartment. In the Off or Vent position, the compressor and its clutch are off. In other four positions of the selector switch, the clutch is engaged or disengaged depending upon the temperature of the air in the ambient temperature. Below 40° F, the ambient switch located infront of the condenser remain open and the compressor cannot be operated. Above 55° F, this switch closes and completes the circuit to the compressor clutch. 

3. Condenser:- Condenser is basically a fin-and-tube radiator, usually placed infront of car's radiator. The condenser receives heated and compressed refrigerant vapor from the compressor and is cooled by the air passing across the condenser. The refrigerant is now in the form of a high pressure liquid which is fed to the receiver-drier unit.

4. Receiver-drier (or Dehydrator):- The refrigerant is stored under pressure in the receiver-drier or the dehydrator. The pressure in the receiver lines is between 50 N/cm² to 200 N/cm depending upon the compressor speed and the surrounding air temperature. The drier removes any traces of moisture present in the system to avoid freezing of moisture at low temperature and, thus, clogging the lines. Even a small amount of moisture can cause running troubles. Drier is usually a silica gel filter that absorbs any water that may be in the refrigerant. A liquid-sight glass is mounted on high pressure line between the receiver and the expansion valve for ascertaining the quantity of the refrigerant in the system.

5. Expansion valve:- The refrigerant goes from the receiver drier to the expansion valve where a sudden expansion to a much lower pressure occurs. The refrigerant changes back to vapor state and this causes a big chilling effect that drops the surface temperature of the evaporator coils to near freezing. It is here that the cooling effect is obtained.

The expansion valve is operated by opposing pressures on either side of the diaphragm. If the evaporator outlet temperature is higher the refrigerant expands and exerts more pressure against the diaphragm, thereby, providing a greater opening to the expansion valve and hence, a greater flow of refrigerant into the evaporator for increased cooling. When the outlet temperature of the evaporator is low, the expansion valve starts closing.

6. Evaporator:- The evaporator unit, where the cooling effect is obtained, is usually located inside the passenger compartment below the dash board. A high capacity blower circulates the air in the car interior across the evaporator coils; and this drops the temperature of the air inside the passenger compartment. The heat picked up by the refrigerant goes back to the compressor in the vapor from where the refrigerant is again compressed to a high pressure and the cycle starts again.

7. Suction throttling valve:- Suction throttling valve ensures that the refrigerant in the evaporator stays at such a pressure that the evaporator core surface temperature does not fall below the freezing point of water (0°C), thus preventing ice formation in the evaporator. A pressure equalizing tube is usually connected between the suction side of the suction throttling valve and the expansion valve diaphragm for effective expansion valve functioning.

EFFECT OF AIR-CONDITIONING ON FUEL ECONOMY

Because the cooling capacity of the automobile air-conditioning system is quite high, the engine driven compressor may absorb 0.75 to 7.5 kW and the fuel economy of the car is affected. If the car reserve power is small, it can affect its acceleration. A loss in economy level of order of 1 to 1.5 km/litre can occur due to use of air-conditioning. The maximum compressor power is required when the car is running at maximum speed under high ambient temperature conditions.

TYPES OF CONTROL SYSTEM:-

In order to control the function and operation of a unit, there are four basic cycles and mechanical systems used. These systems vary in size and installation procedures and are as follows:

1. Low side pressure control.

2. Pressure operated by-pass. 3. Solenoid operated by-pass.

4. Electromagnetic clutch.

5. Combination of above controls.

Low Side Pressure Control:-

In this system, an evaporator pressure controlled regulator valve is installed in the suction line. A constant pressure is kept in the evaporator by this valve. If the evaporator tends to go below a certain setting while holding the evaporator at constant pressure and temperature, the valve would close.

This pressure control prevents the compressor from producing a high vacuum at high speeds causing the compressor to lose its oil. A system with an automatic expansion valve having small bleeder hole in the orifice is used to overcome this problem. To prevent a very high vacuum from forming, a small amount of refrigerant enters the suction line. In this system, the compressor is run continuously.

Pressure Operated Hot Gas By-pass Valve:-

In this system, the pressure operated bypass valve is connected between the compressor discharge (high side) and compressor low side or suction line.  When the pressure difference reaches the valve setting, the valve is set to open and by-pass hot vapor from the high side to the low side. The valve will close or open if the suction line pressure decreases or increases respectively. To maintain a certain pressure in the evaporator, hot gas (vapor) is fed into the low pressure side. In this system, a continuously operated compressor is used.

Solenoid Operated Hot Gas By-pass:-

In order to open a solenoid valve and by-pass the hot gas from the high pressure side to the low pressure side when the temperature of the evaporator falls to 0° C, a thermostat mounted on the evaporator is used. It is located in the return air flow with a sensing bulb. When the return air temperature is lowered, so that the thermostat is at a temperature of 0°C, the solenoid valve opens to allow hot gas from the condenser to by-pass back into the suction line. This valve does not provide the throttling effect of a pressure operated valve since it is either closed or wide opened. In this system, either a continuous operating compressor or a rotary compressor is used. When the circuit is closed or when the current is on, the solenoid is in a closed position. When the circuit is open, the valve also opens. Hence, the thermostat opens on temperature drop. When the pressure in the system balances to reduce the starting load and the power is off, the solenoid valve also opens up.

Electromagnetic Clutch:-

In certain automobiles air-conditioning systems, a mechanism permitting the engine to run without the compressor running is used. To engage the compressor belt pulley to the compressor crank shaft or the disengage it, a clutch is used. This clutch operated by electromagnetism by forcing the clutch disk against the pulley is known as magnetic clutch. Two types of magnetic clutches used are - revolving magnetic coil and stationary magnetic coil.

***Air- Conditioning System Components

Auto Air-conditioning System

 Auto Air-conditioning System

INTRODUCTION:-

Due to varying conditions of heating, ventilating, cooling and dehumidification in the atmosphere at various places, the air conditioning of automobiles is very essential. To maintain human comfort and improve internal atmosphere in an enclosed space, proper control of freshness, temperature, humidity and cleanliness of the air is required.

automobile, the air-conditioning system involves three main processes of heating, cooling and dehumidification. In the heating system, the heat needed to warm the automobile is derived from the engine coolant or circulating warm water after passing through a heating coil. The system either consists of the recirculatory heaters or fresh air intake systems with provisions of recirculation. For producing a cooling effect, an evaporator coil operated by a refrigerating system is placed inside the chamber of automobile. The air to be circulated inside the passenger compartment is cooled by the evaporator coil. Depending upon the speed of vehicle, frequency of stops, atmospheric and traffic conditions, the air conditioning loads vary from instant to instant and place to place. Due to moving nature of the vehicle, the equipment used should be light, compact, quickly serviceable and unaffected by vibrations.

The dust particles are entrapped by the wet surfaces of the evaporator core and are drained of with the condensed moisture. This provides clean and pure air for breathing.

In comparison to domestic air-conditioning, very large amount of air-conditioning capacity is required for a car. This is due to the metal construction of the car, the flow of air around a moving car and relatively large glass areas in the passenger compartment. Typically, a car air-conditioning system may be between 1 to 4 tons.

A refrigerating machine driven by the car engine is used in the automobile air conditioner to maintain the desired comfortable temperature level. For heating purposes, the warm water from the engine cooling system is used. The heat required to warm the automobile is generally provided by circulating warm water through a heating coil.

The air-conditioning system of the most of the car consists of 1.5 kW compressor located under the engine hood and belt driven from the crank shaft. The evaporator and the blowerunit were located in the trunk compartment while the air cooled condenser was placed infront of the radiator.

A typical air-conditioning system used in automobiles, as shown in primarily consists of compressor, condenser, receiver, expansion, evaporator, dehydrator, filter, sight glass, blower and the air distribution system as well as certain type of capacity control.

Operating conditioning:-. In an automobile, the air-conditioner g should provide comfort and control conditions in the car during mild or damp weather as well as hot weather. The operation should include heating, defogging, as well as removing dust, smoke and odor.

The compressor is belt driven from the engine. Since the engine speed changes with the change in car speeds, therefore, the compressor speed will also vary. Only the hottest day in the sun as well as underside wind conditions the compressor as well as the cooling is at idling speed. Considerable excess capacity, particularly under cool weather conditions, is provided of by the above capacity condition. The problems of controlling the temperature as well as the refrigerant flow (both liquid and vapor) within the system is provided by this condition. The high side pressure is liable to build up while the low sidepressure will drop very low when the compressor is operating very rapidly; and little or no refrigeration is needed.

The evaporator temperature will be lowered by dropping of the low side pressure. Since the evaporator surface is liable to circulation through it, it is, therefore, necessary that the evaporator temperature should not be allowed to drop below 0°C. The compressor valves are liable to damage as well as result in its burning out if the system is operated under a low side pressure.

To overcome these problems, different types of cycle and mechanical systems are used. To obtain maximum cooling during high heat loads in cooling season as well as in washing or during heavy rainstorm, it is necessary that the fresh air ducts should be closed. About 10 minutes are taken by a standard automobile air-conditioner to cool an automobile from 43.3°C to 29.44°C standing in the sun. Generally, the inside temperature of a car parked in sun with windows closed is 65.5°C. The sun load and the heat conducted through the car windows is the highest heat load or the heat gains. Usually 100% fresh air or no fresh air (all circulated) to 25% fresh air are used by different units.

Performance rating:-The compressor capacity will decrease when the automobile slows down, while it will increase when it speeds up. Except during the interval of parking or moving in a slow moving traffic, the variation in compressor capacity is directly proportional to the changing heat loads. This changed capacity is below the required capacity. To obtain the required capacity, the engine may be idled at higher speed and for higher engine speeds, travel in traffic in some intermediate gear.

At high speeds, the refrigerating system consumes as much as 6 kW with a unit capacity of 3 tons or 9072 kcal/h approximately. For each ton of refrigeration effect, about 0.4 kW to 2 kW are required which is comparably more than a motor driven constant speed compressor comparably built and with the evaporator coil and condenser more ideally located requiring 0.75 kW for each ton of refrigeration.

A hot water coil using engine heat is installed in the air duct for heating purposes. During both the cooling and heating purposes, the same fans may be used.

Typical installation. A factory installed air-conditioner to be fitted as a compact unit or cooling unit which can be fitted in any standard make of automobile are manufactured by most of the automobile manufacturers. A small mixing chamber is by a V-belt from a special pulley on the engine crank shaft. In certain systems, the compressor driven pulley contains an electrically operated clutch to declutch it from the pulley. The condenser is mounted at the front of the car while the receiver is mounted at the side of the engine. The expansion valve, which is the controlling valve in the system, is placed near the evaporator. The evaporator is fitted in the tank compartment.

The cooled air enters the passenger compartment at its rear before distribution. Below the rear seat, the warm air is returned through a grill to the cooling unit after passing through a filter.

Units of generally 1 to 1.5 tons capacity, with compressor ranging from 1.5 to 3 kW (maximum) are used in most of the cars. To control the car temperature fitted under the dash board receives air from both the evaporator coil as well as the heater coil. The passenger compartment receives the conditioned air travelling from the plenum or mixing chamber.

For heating the motor vehicle, the controls are set. The hot water from the engine block water jacket circulating through the heater coils in the passenger compartment is used for heating purposes. To provide air-conditioning cooling, the controls are again set. The air blown through the cold evaporator coils is circulated through the passenger compartment of the motor vehicle for this purpose. Certain units are also operated by automatic systems.

A typical installation of air-conditioning system used in automobiles is shown in

The compressor is generally mounted on the side of the engine. It is motor driven and compensate for the variable compressor speeds a thermostat is also used. A recent development in automobile air-conditioning is a complete factory assembled unit which can be bolted near the engine.

**Describe about.....................Auto Air-conditioning System 

Alternator(A.C Generator) Principle

 Alternator(A.C Generator) Principle

ALTERNATOR (A.C. GENERATOR) PRINCIPLE:-

In D.C. generator, the conductors are rotated in a stationary magnetic field and current flows in the same direction. But in A.C. generator, the magnetic field is rotated and the conductors remain stationary. The current flows first on one direction and then in other alternately. 

As shown in a rotating bar magnet furnishes the moving field which cut the U-shaped conductor. As at (a), when the north pole passes the upper leg of the conductor, the current flows in one direction. As at (b), when the south pole passes the upper leg of the conductor, the direction of the magnetic lines of force is reversed and the current flows in reverse direction in the conductor. Thus, the magnet is revolving continuously, the direction of lines of force is also changing continuously, the current alternate in direction-alternating current flows. The strength of current depends upon the following factors:

1. Strength of the magnetic field.2

. Speed of the magnetic field with which it revolves. 3. Number of conductors.

Instead of a simple bar magnet, two or more pole pieces, having field winding, are assembled on a shaft. When the current flows in the winding, a strong magnetic field is created and the pointed ends of the pole pieces become alternately north and south poles. The two ends of the conductors are connected to the two slip rings fixed on the shaft. The brushes make continuous sliding contact with the slip rings, through which the current is taken out to an external circuit for transmission and distribution.

The alternator type generator differs from the commutator type generator in the method of voltage and current control and also in design. It uses silicon diodes to change the alternating current to direct current for the vehicle's electrical system. Also, it does not require any cutout to prevent the battery from discharging through it, because the diode rectifiers allow the current to flow in one direction only.

Construction of Alternator:-

Shows rotor of an A.C. generator. The rotor consists of a circular field coil encased by two end pole pieces, each having six protruding fingers spaced 60 degrees apart. These fingers are alternately spread to provide twelve poles. The end of the field coils are connected to the slip rings.

The carbon brushes make sliding contact with the slip rings, through which the current is taken out to an external circuit. The rotor is mounted on a shaft supported in the front by ball bearings and in the rear by needle bearings. A pulley is keyed at the front end of the shaft to turn by means of an engine driven belt.

The stator of A.C. generator consists of an internally slotted, laminated iron core around which three sets of windings are made. One of each winding is connected to a common Y-junction. The other end is connected to one positive diode rectifier and one negative rectifier.  

shows the charging circuit of A.C. generator. When the ignition switch is turned on, the rotor receives current from the battery through the voltage regulator. This current produces the magnetic field of the rotor. As the rotor is turned by the pulley, current is induced in the stator winding. This alternating current is changed into direct current by rectifiers. The voltage depends upon the rotor speed. A voltage regulator is used to limit the generator voltage to a correct value.

RECTIFIERS:-

The A.C. generator of the alternator produces alternating current. It is to be converted or rectified to direct current because the battery ignition system and other electrical components of the automobile are all D.C. units. To change the alternating current to direct current, six silicon diode rectifiers are used. The diode is an electric device that permits current to flow through it in one direction only. The three positive rectifiers are pressed into a heat sink (an insulated die cast aluminum holder) which is electrically insulated from the generator frame. It is large enough to dissipate the heat generated by the rectifiers. The positive rectifiers are connected to the battery terminal of the generator and the negative rectifiers are grounded by being pressed into the rear aluminum frame.

By turning on the ignition switch, the rotor receives current from the battery through the voltage regulator. This current energizes the rotor field magnets, which induce a current in the stator windings as the rotor is turned by the pulley. The induced alternating current is changed to direct current by the rectifiers.

GENERATOR CONTROL:-

If the full charging current is generated at low engine revolutions, the charging current would be excessive at higher engine revolutions and may damage the battery and the general electrical system. The generator output must automatically adjust itself to the electrical needs of the vehicle. The charging rate of the generator must be adjusted to the condition of the battery, a high rate for a low battery and a low or no rate for a fully charged battery. Also, the battery must be disconnected from the generator when it is not being turned; and reconnected when it is able to furnish electrical energy. Therefore, it is necessary to introduce some means of controlling the voltage or the current. By generator control (or regulation) we mean preventing the generator from producing excessive voltage and current without any control, a generator would continue to increase its output as speed goes up until it would be producing so much current that it would overheat and burn up.

REGULATORS FOR A.C. GENERATORS

Various types of regulators for A.C. generator are developed in recent years. Some operate and are adjusted like those for D.C. generators. Others have no moving parts at all. A popular type has been described here.

shows the wiring circuit of a voltage regulator for A.C. generator. In this system, only the voltage is to be regulated. When the voltage reaches to a predetermined value, the regulator contact points open to insert resistance into the generator field circuit and thus prevent excessive voltage. The contact points of the regulator vibrate to maintain a steady voltage. There are two sets of contact point in this regulator-a lower set and an upper set. At intermediate speeds, the lower contact points vibrate to open and close; and control the generator voltage. This action inserts and removes the resistance in the generator field circuit. At higher speeds, the higher voltage generator causes the upper contact points to vibrate. When the upper contact points are closed, the generator field winding is shorted, that is, both the ends are connected to ground, so that further voltage regulation is obtained. Thus, the voltage is properly regulated throughout the full range of generator speed with the help of two sets of contact points.

The system does not require current regulator and cutout relay.The current flows only in one direction to charge the battery. The diodes prevent the current to flow in reverse direction. When the generator slows or stops, the battery cannot discharge back through the generator, even though the two still remain connected to each other. When the ignition switch is turned off, the field is disconnected from the battery to prevent any drain on the battery, when the engine is not running.

CUTOUT RELAY:-

The cutout relay (or circuit breaker) closes the circuit betweenthe generator and the battery when the generator is producing current. Also, it opens the circuit so that the battery cannot discharge back through the generator when the generator stops or slows down. The D.C. generator is connected to the battery through a cutout relay and an ammeter.

The cutout relay is simply a magnetic switch. It consists of two windings shunt winding and series winding, assembled around a core and a flat steel armature mounted on a hinge above the core. The series winding consists of a few turns of heavy wire and the shunt winding consists of a few turns of fine wire. The armature is connected to the battery through an ammeter by contact points.

When the generator is not operating, a spring on the armature holds the contact points apart, this keeps the circuit between the generator and the battery open. When the generator is operating, the core winding creates magnetic field which attract the armature, contact points are closed and generator is connected to the battery. Current flows from the generator to the battery and passes through the series winding. But when the generator stops, the current begins to flow from battery to generator. This reverse direction of current flow in the series winding causes the magnetic field to reverse. Thus, the magnetic fields of the winding no longer aid and is so weakened that it cannot hold the armature down. The spring tension pulls the armature up, separating the contact point. This opens the circuit between the generator and the battery.

AMMETER:-

Ammeter is connected in the charging circuit between the battery and generator to show how much current is flowing to the battery during the charging; and how much current is flowing from the battery during the discharging. Ammeter is fitted on the instrument panel infront of the driver. It is used in most of the vehicles, however, an indicator lamp is also used in some vehicles to indicate whether or not the generator is charging the battery.shows the simplified diagram of a car ammeter. It consists of a pivoted vane to which a needle is attached, a permanent magnet and a heavy conductor. The needle moves on a graduated scale, one side of which indicates charging current and the other side discharging current. At the centre, zero is marked. When the needle points zero, no current flows to or from the battery, the pivoted vane is held between the two poles of the permanent magnet. When the current flows to the battery, needle swings to "charge" side. When the current flows from the battery, the needle swings to "discharge" side. When the current flows in any side, it passes through the conductor. The magnetic field forces the vane to move. The stronger the current, the farther the van moves. Therefore, the needle swings on the scale point in the amount of current flowing through.

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Alternator(A.C Generator) Principle

DC Generator

 Dc Generator:

Introduction:-Generator is a device to convert mechanical energy from the automobile engine into electrical energy. The generator replaces in the battery the current used in starting the engine and also supplies current for operation of electrical devices such as ignition system, lights, radio, etc. The automobile generator is usually a low voltage D.C. generator producing direct current, because the use of battery requires direct current.

The generator or the dynamo, is usually mounted on the side of the engine block. It is driven by the engine fan belt. As the engine speed is subjected to large variations, the generator speed will also vary. But the necessity demands that the voltage should remain nearly constant. When the generator is driven by the engine, it supplies electrical energy for all the circuits of the vehicle and keeps the battery fully charged. All the motor vehicles use generators to supply direct current. Many manufacturers use the commutator type shunt-wound, self energizing generator unit. In recent years, alternator type generator is also used, which uses diodes to convert the generated alternating current into direct current.

Generator Principle:- When a conductor is moved in a magnetic field, a current is produced in it. The direction of flow of the current is determined by Fleming's left hand rule. It gives the relationship between direction of lines of force, direction of conductor motion and direction of current flow. If left hand is placed around the conductor with fingers pointing in the direction of lines of force circling the conductor, the thumb will point in the direction of the current. The conductor must move across the magnetic field so that it cuts through lines of force. As shown in Fig. 23.1, if the conductor moves towards the right, the direction of current flow induced in conductor will be outwards, that is, towards the reader.

The conductor must move across the magnetic field so that it cuts the lines of force. If it moves parallel to the lines of force, it will not cut the lines of force and no current will be induced in the conductor. The amount of current induced in the conductor depends upon the rate at which the lines of force are cut. Thus, if the conductor moves more rapidly through the magnetic field, more lines of force will be cut per second and more current will flow through the conductor. If the magnetic

Instead of a straight conductor, a U-shaped conductor is rotated in the magnetic field, so that the direction of current flows in the two legs of U will be opposite, because of their opposite direction of motion. If the ends of the conductor are connected to the commutator through the carbon brushes, the current can be taken to the outer load. However, the current produced in single conductor will not be uniform, its shape will be as given in . To make it uniform, many such conductors are used in generator. The magnets are not permanent type but they are electromagnets, the energy for which is taken from the current produced by the generator itself.

Direction of electromotive force:- The direction of the electromotive force generated in a conductor within a magnetic field will vary with changes in the direction of the magnetic flux and the direction in which the conductor moves. If a conductor is moved (in the direction indicated by the large arrow in the illustration below) between the magnetic north and south poles, the electromotive force will flow from right to left (the direction of the magnetic flux is from the north to the south pole).

The direction of the electromotive force can be understood by use of Fleming's Right-hand rule.

Fleming's Right-hand Rule. With the thumb, forefinger and middle finger of one's right hand are outstretched at right angles to each other, the forefinger will indicate the direction of the magnetic flux (magnetic lines of force), the thumb the direction of conductor movement, and the middle finger the direction of the electromotive force.

CONSTRUCTION OF D.C. GENERATOR:-It consists of pole pieces fitted in a frame, armature, commutator and field winding. The pole pieces or shoes are the laminated iron cores for the field winding that furnish the magnetic field for the generator. Most generators contain one pair of poles (N-S), shaped to allow the armature to rotate between them with very little clearance. The armature is made up of conductors of insulated wire around on a laminated iron core. The conductor ends are soldered to copper wires, separated from each other by mica, which make the commutator. A steel shaft running the armature and commutator is supported by means of bearings so that the pulley and fan mounted on the front end can be turned by an engine-driven belt. Two carbon brushes are held in the brush holders, which make firm contact with the commutator segments in order to connect the coils of the rotating armature with the outside circuit.

When the armature rotates, the current is induced and flows in the conductors through the load. Part of the current induced in the conductors flows through the two field windings assembled around the two magnetic poles. This current strengthens the magnetic field between the poles, thus increasing the conductors as they move through the magnetic field.

The armature and commutator are designed to rotate together. They allow the generator to produce a flow of direct current that, is, the current continues to flow in the same direction. As the two ends of a conductor rotate and change position with respect to each other, the two segments of the commutator also changes positions so that the current continues to be fed to one brush in the same direction.

REGULATORS FOR D.C. GENERATORS

Regulators for D.C. generators are made by different companies, the most famous of them are as follows:

1. Delco-Remy regulator. 2. Auto-lite regulator.

3. Ford regulator.

The working principle of these regulators is the same. Fig. 23.16 shows Delco-Remy regulator, designed by Delco-Remy division of General Motors Corporation. It consists of a cutout relay, a voltage regulator and a current regulator. It is connected to the shunt wound generator and battery of the car electrical system.

Voltage regulator. The voltage regulator maintains practically constant voltage in the electrical circuit. When the battery is low, it is supplied current at a high charging rate by the generator and when the battery is charged, the charge rate becomes slow.

The voltage regulator consists of two windings on a single core a shunt winding of many turns of fine wire and a series winding of a few turns of heavy wire. The shunt or voltage winding is connected at one end to the input side of the cutout and grounded to the other end. The series or current winding is connected at one end to the field circuit of the generator and at the other end to the contact point of armature. The armature above the windings is hinged and held in upper position by a spiral spring. In this position, it closes a set of contact points which complete the generator field circuit through the series winding to ground.

When the battery is in a low stage of charge, the regulator does not operate. When the generator voltage reaches a predetermined value (7.2 - 8 volts or 13.6-15.8 volts) both the windings build up sufficient magnetic strength that pulls down the armature against spring tension. Thus, the contact points of the voltage regulator open, collapsing the magnetic field of the series winding. It also causes the field circuit to ground througth the resistance. This increased resistance in the generator field circuit reduces the current through it and hence the magnetic strength. This cuts down the generator output which reduces the current in the shunt coil. Because the magnetic field strength is reduced, the armature is again pulled back making the contact points closed. This directly groundsthe generator field circuit again and the output increases. The entire sequence is repeated many times a second, causing the resistance to be inserted into and removed from the generator field circuit as many as 200 times a second. This holds the voltage to a constant value. The constant voltage thus maintained becomes less and less able to send current into the battery because the battery voltage increases as it approaches a charged condition. Thus, the charging rate is reduced in proportion to the condition of charge of the battery.

Current regulator. The current regulator is constructed in the

similar manner as the voltage regulator, excect that the winding consists of a few turns of heavy wire connected in series with the generator armature, so that the full generator current passes to the battery through the cutout relay. When the generator current reaches a set value, it creates sufficient magnetic force in the core which attracts the armature to open the contact point. This action adds resistance to the generator field to cut down the generator output. When the generator current is reduced. n) the magnetic force is also reduced, the spring tension pulls the armature to close the contact points. The generator field circuit is directly grounded. This causes the generator current to again increase. The cycle is repeated very rapidly, about 250 times a second, causing the current regulator to limit the current output of the generator to the rated value.

Combined action. Both the regulators do not operate simultaneously, only one regulator can operate at a time. When the battery is low and load requirements are 'ioh, the current regulator operates to prevent the generator output from exceeding its safe maximum. When the battery is high and the load requirements are high, the voltage regulator operates to reduce the generator output. It falls below the value required to cause the current regulator to operate.

The voltage regulators and also some current regulators are temperature compensated. They have higher settings when cold than when hot. Temperature compensation of the voltage regulator allows the increase of voltage with low temperature. The current regulator is compensated to permit a higher generator output when the current regulator is cold than when it is hot. The generator output decreases as the temperature o the current regulator increases.

All details about Dc Generator. 

Engine components

* Engine components

Types of engine components:- 

                                1. Engine head

                                2. engine block

                                3. Liners

                                4. crank-shaft

                                5. connecting rod

                                6. piston

                                7. piston ring

                                8. camshaft

                                9. valve

                              10. valve and it's operation

                              11. intake manifold

                              12. exhaust manifold

                              13. spark plug

                              14. Fly wheel

                              15. carburetor

                              16. Radiator

                              17. Thermostate valve

                              18. Distributor

                              19. Ac mechanical pump

                              20. Lubricating oil pump

                              21. Air filter

1.Engine Bolck:-  The top of the cylinder is covered by a separate cast piece known as the cylinder head. The cylinder head is bolted to the top of the cylinder block. It contains combustion chamber. Spark plug and sometimes valves (in I-and F-head) are mounted in it. It incorporates passages for the flow of cooling water.The cylinder head is usually made of gray iron or aluminum alloy. Aluminum has the advantages of lightness in weight and high heat conductivity. It is cast separately from the cylinder block so that it may be removed for cleaning carbon and grinding valves. To retain compression in the cylinder, a flat piece of gasket is placed between the cylinder head and the cylinder block. In certain cases, such as a racing car engine, a separate head is not used. But a single piece of cylinder block and head is difficult and costlier to make; and the internal parts of the engine are not as accessible. 

2.Engine block:-  Cylinder block, cylinder head and crankcase-these three parts form the foundation and main stationary body of the automobile engine. They serve as support and enclosure for moving parts. In modern engines, the cylinder block and crankcase form a single casting, which gives a rigid structure. Ribs are cast in the crankcase to give it extra strength and to support the main and, in some cases, the cam shaft bearings. The cylinder block may also have a separate crankcase for the crankshaft, which is mainly confined to large engines, marine and stationary engines. A separate aluminum crankcase would result in saving the weight as well as enable cheaper and quicker replacement.

A cylinder block consists of three parts:

1. The cylinders in which the pistons slide up and down.

2. The ports or openings for the valves. 3. The passages for the flow of cooling water.

The round cylinder surfaces are given precision mirror finish" by accurate grinding and honing processes.

The cylinder block is usually made from gray cast iron, and sometimes, with addition of nickel and chromium. Some blocks are cast from aluminum, in which cast iron or steel sleeves are used. For most engines, cast iron has been found to be a satisfactory cylinder wall material, as it has better wearing qualities. In some small engines, the cylinder walls are plated with chromium, a very hard metal, to reduce wall wear and to increase their service life. Tests are being carried out on high silicon-aluminum alloys to determine their possibilities as a material for cylinder blocks and crankcases. These alloys have a low coefficient of thermal expansion and high wear resistance.

3.Liners:-   The problem of cylinder wear is considerable and this has been solved by the use of cylinder liners. The cylinder liners are in the form of barrels made of special alloy iron containing silicon, manganese, nickel and chromium. They are cast centrifugally. It is now customary to fit cylinder liners on engines of cars and commercial vehicles. These liners are of the oil hardening type and offer considerably longer life for the engine. The cylinder liners are of the two types-dry liners and wet liners.

1. Dry liners. A dry liner is made in the shape of a barrel having a flange at the top which keeps it into position in the cylinder block. The entire outer surface of the dry liner bears against the cylinder block casting and hence has to be machined very accurately from the outside also. Thus, it is not in direct contact with the cooling water and hence is known as dry liner. Its thickness ranges from 1.5 mm to 3 mm. It is used mostly for reconditioning worn cylinders.

2. Wet liners. A wet liner forms a complete cylinder barrel. It is provided with a flange at the top which fits into the groove in the cylinder block. At the bottom either the block or the liner is provided with grooves, generally three in numbers, in which the packing rings made of rubber are inserted. The liner is in direct contact with the cooling water and hence is known as wet liner. The outer surface of the liner does not require accurate machining. Wet liners are thicker than dry liners, ranging from 1.5 mm to 6 mm.

3. Crank-shaft:-  Crankshaft is the first part in the power transmission system on to which the reciprocating motion of the piston is converted into the rotating motion with the help of connecting rod. A crankshaft consists of crankpins, webs (crank arms or cheeks) balancing weights and main journals. Big end of the connecting rod is connected to the crankpin of the crankshaft. Centre to centre distance between the crankpin and crankshaft is half of the piston displacement during a stroke. Thus, one complete revolution of the crankshaft makes two strokes of the piston. The parts of the crankshaft inside the main bearings are called the main journals. The crankshaft is supported by the main bearings on the main journals. Balancing weights are provided on the opposite side of the crank arms for balancing.

The crankshaft is made of casting or forging of heat treated alloy steel and is machined and ground to provide suitable journals for the connecting rod and main bearings. It must be strong enough to take the thrust of the pistons during the power strokes without excessive distortion. Also, it must be carefully balanced to eliminate undue vibration resulting from the weight of the offset cranks.

Crankshafts have drilled oil passages through which oil can flow from the main bearing to the connecting rod bearings. 

5.Connecting rod:- The connecting rod is the connection between the piston and the crankshaft. It joins the piston pin with the crankpin. Small end of the connecting rod is connected to the piston pin and big end to the crank pin. The function of the connecting rod is to convert linear motion of the piston into rotary motion of the crankshaft.The connecting rod usually has I-beam cross-section; and is. made of forged steel. Aluminum alloy is also used for connecting rods. They are carefully matched in sets of uniformweight in order to maintain engine balance. The lighter the connecting rod and the piston, the greater the resulting power and the lesser the vibration because the reciprocating weight is less. The connecting rod carries the power thrust from piston to the crank pin and hence it must be very strong, rigid and also as light as possible.

6.Piston:-  Piston is considered to be one of the most important parts in a reciprocating engine in which it helps to convert the chemical energy obtained by the combustion of fuel into useful mechanical power. The purpose of the piston is to provide a means of conveying the expansion of the gases to the crankshaft, via the connecting rod, without loss of gas from above or oil from below. Piston is essentially a cylindrical plug that moves up and down in the cylinder. It is equipped with piston rings to provide a good seal between the cylinder wall and piston. Although the piston appears to be a simple part, it is actually quite complex from the design stand point.The efficiency and economy of the engine primarily depends on the working of piston. It must operate in the cylinder with minimum friction and should be able to withstand the high explosive force developed in the cylinder and also the very high temperature ranging from 2000° C to over 2800° C during operation. The piston should be as strong as possible, however, its weight should be minimized as far as possible in order to reduce the inertia due to its reciprocating mass.

The top of the piston is called head. Ring grooves are cut on the circumference of the upper portion of the piston. The parts below the ring grooves is called skirt. The portions of the piston that separate the grooves are called the lands. Some pistons have a groove in the top land called a heat dam which reducesheat transfer to the rings. The piston bosses are the reinforced sections of the piston designed to hold the piston pin or wrist pin.

7.Piston Rings:- Piston rings are fitted into the grooves of the piston to maintain good seal between the piston and the cylinder wall. There are three functions of the piston rings as follows:

1. To provide a pressure seal to prevent blow-by of burnt gases. Blow-by is the name that describes the escape of burnt gases from the combustion chamber, past the piston, and into the crankcase.

2. To form the main path for conduction of heat from the

piston crown to the cylinder walls.

3. To control the flow of oil to the skirt and rings themselves in adequate quantity while preventing an excessive amount reaching the combustion chamber with consequent waste and carbonization.

Material. Piston rings are usually made of fine-grained alloy cast iron. This material possesses excellent heat and wear resisting quantities inherent in its graphitic structure. The elasticity of this material is also sufficient to impart radial expansion and compression which is necessary for assembly and removal of the ring; and particularly to enable it to exercise flexible pressure on the cylinder walls.

There are two types of piston rings:

1. Compression rings. 2. Oil control rings.

8.camshaft:-A cam shaft is simply a shaft on which cams are mounted. The cam shaft is mounted in bearings in the lower part of the cylinder block in most in-line engines. In a few engines it is located on the cylinder head. In V-8 engines it is located between the two banks of cylinders.A cam is a device that changes rotary motion of the cam shaft into linear motion of the follower or lifter. The cam has high spot or lobe. The follower riding on the cams will move away from or toward the cam shaft as the cam rotates.The cam shaft is driven by the crankshaft either by a pair of meshing gears (timing gears) or by means of a pair of timing sprockets connected by a chain. The cam shaft gear or sprocket has twice as many teeth as the gear or sprocket on the crank shaft. This gives 1 : 2 gear ratio, the cam shaft turns at half the speed of the crank shaft. Thus, every two revolutions of the crank shaft produce one revolution of the cam shaft; and one opening and closing of each valve, in the four-cylinder engine. The gear and sprocket maintain a definite time relationshipbetween the cam shaft and crank shaft to insure opening the valves exactly at the correct time in relation to piston position. Timing marks on the gears and sprockets are used to set the shaft in correct time with each other when the units are assembled. In the small circles on the crank shaft timing gear must fall between the two small circles on the crank shaft timing gear to insure correct valve timing. The marks of the sprockets are in a straight line with the centres of both shafts to insure correct valve timing.

9,10> valve and it's operation:- Valve is a device to close and open a passage. In motor vehicle engines, two valves are used for each cylinder - an inlet or intake valve and an outlet or exhaust valve. Fuel is admitted to the cylinder by the inlet valve, and the burned gases escape by the exhaust valve. When closed, the valve must seal the combustion space tightly. The valves are usually made of austenitic stainless steel which is a corrosion and heat resisting material. Exhaust valve is usually made of silchrome steel which is an alloy of silicon and chromium with unusual resistance to heat. Inlet valve being subjected to less heat is usually made of nickel chromium alloy steel.

Overhead Poppet Valve Mechanism.  the valve mechanism to operate the valve when it is in the cylinder head (in /-and F-head design). This type of mechanism requires two additional moving parts-the push rod and the rocker arm. As the cam rotates, it lifts the valve-tappet or the lifter which actuates the push rod. The push rod rotates the rocker arm about a shaft- the rocker-arm shaft, or a ball joint in some designs to cause one end to push down on the valve stem to open the ck valve, thus connecting the valve port with the combustion chamber.

11,12> Intake, Exhaust Manifold:-   The exhaust manifold is a tube for carrying the exhaust gases away from the engine cylinders. It collects exhaust gases from the exhaust ports of the various cylinders and conducts them to a central exhaust passage.The exhaust manifold is usually made of cast iron. It is bolted to the side of the cylinder block on L-head engines and to the side of the cylinder head on I-head engines. On V-8 engines, there are two exhaust manifolds, one for each bank of cylinders. On some V-8 engines, each manifold is connected to a separate exhaust pipe, muffler and tail pipe. On others, they are connected by a crossover pipe and exhaust through a common muffler and tail pipe. 

13.spark plug:-Spark plug is a device to produce electric spark to ignite the compressed air-fuel mixture inside the cylinder. The spark plug is screwed in the top of the cylinder so that its electrode projects in the combustion chamber.Construction. A spark plug consists of mainly three parts:

 1. Centre electrode or insulated electrode. 

2. Ground electrode or outer electrode.

3. Insulation separating the two electrodes.

The upper end of the centre electrode is connected to the spark plug terminal, where H.T. cable from the ignition coil is connected. It is surrounded by porcelain insulator. The lower inalf portion of the insulator is fastened with a metal shell. The lower portion of the shell has a short electrode attached to one side and bent in towards the centre electrode, so that there is a gap between the two electrodes. The two electrodes are thus separated by the insulator. The sealing gaskets are provided between the insulator and the shell to prevent the escape of gases under various temperature and pressure conditions. The lower part of the shell has screw threads and the upper part is made in hexagonal shape like a unt, so that the spark plug may be screwed in or unscrewed from the cylinder head.

14.Fly-wheel:-  A flywheel is a fairly heavy steel wheel attached to the rear end of the crankshaft. The size of the flywheel depends upon the number of cylinders and the general construction of the engine.

The flow of power from the engine cylinders is not smooth. Although the power impulses in a multi-cylinder engine overlap or follow each other to provide a fairly even flow of power, however, additional levelling of power impulses is required. This is done by a flywheel.

To understand the function of a flywheel in a better way, take the example of a four-stroke, single-cylinder engine. There are times when more power is being delivered than at other times. This tends to make the crankshaft speed up and then slow down.The engine delivers power during one stroke only the power stroke; and it absorbs power during the other three strokes-to push out the exhaust gases, to intake fresh charge in the cylinder and to compress this charge. Thus, during power stroke the engine tends to speed up and during the other three strokes it tends to slow down. The inertia of the flywheel tends to keep it running at constant speed. When the engine tends to speed up the flywheel resists it. When the engine tends to slow down, the flywheel resists it. Thus, the flywheel absorbs energy as the engine tries to speed up and gives back energy as the engine tries to slow down, keeping the engine speed almost constant. In multi-cylinder engine, the flywheel acts in the same way to smooth out still more the peaks and valleys of power flow from the engine.

15.Carburetor:- The carburetor is a device for atomizing and vaporizing the fuel and mixing it with the air in varying proportions to suit the changing conditions of spark ignition engines. The air-fuel mixture so obtained from the carburetor is called the combustible mixture. The process of mixing the gasoline fuel with air to obtain the combustible mixture is called carburetion.

Hence, the terms vaporization and atomization should be understood clearly. Vaporization is the change of state of the fuel from liquid to vapor. Atomization is the mechanical breaking-up of the liquid fuel into small particles (but not actually breaking-up into atoms, as the name implies) so that every particle of the fuel is surrounded by air. In order to produce very quick vaporization of the liquid fuel, it is sprayed into the air passing through the carburetor. Spraying of the liquid turns it into many fine particles, so that the vaporization occurs almost instantly.

The carburetor supplies the air-fuel mixture of varying proportions to suit the changing conditions of the engine. The mixture must be rich (have a higher percentage of fuel) for starting, acceleration and high speed operation. The mixtures should be lean (have a lower percentage of fuel) for operation at intermediate speed with a warm engine. The theoretically perfect mixture of air and gasoline contains 15 parts of air and part of gasoline by weight. An ideal carburetor would pass the mixture of completely vaporized fuel and air in the proper proportion to the intake manifold and cylinder. But in the present-day carburetors, the complete vaporization of fuel is not achieved, due to the heavy nature of fuel and other limitations. The heated intake manifold and hot spots in the manifold vaporize part of atomized fuel. Even until the end of the compression stroke in the cylinder, the gasoline does not vaporize completely, although the heat and pressure during the. 

16.Radiator:- Radiator is a device for having a large amount of cooling surface to the large amount of air so that the water circulating through it is cooled efficiently. It consists of an upper tank and a lower tank and between them a core. The upper tank is connected to the water outlet or outlets from the engine jacket by a hose pipe; and the lower tank is connected to the jacket inlet through the water pump. The core is a radiating element, which cools the water.There are two basic types of radiator cores-tubular type and cellular type. In tubular type core the upper and lower tanks are connected by a series of tubes through which water passes. Fins are placed around the tubes to improve heat transfer. Air passes around the outside of the tubes, between the fins, absorbing heat from the water in passing. In cellular type core, air passes through the tubes and the water flows in the spaces between them. The core is composed of a large number of individual air cells which are surrounded by water. Because of its appearance, the cellular type is usually known as a honeycomb radiator, especially when the cells are hexagonal in form.In a tubular radiator, because the water passes through all the tubes, if one tube becomes clogged, the cooling effect of the entire tube is lost. In a cellular radiator, the clogging of any passage results in a loss but of a small part of the total cooling surface.

Radiators are also classified according to the direction of the water flow through them. In some, the water flows from top to bottom-down flow type radiators. In other, the water flows horizontally from an input tank on one side to another tank on the other side-cross flow type radiator.

Radiators are usually made of copper and brass because of their high heat conductivity. The various sections of the radiator are almost completely joined together by soldering.

17.Thermostat Valve:-A thermostat valve is used in the water cooling

system to regulate the circulation of water in system to maintain the normal working temperature of the engine parts during the different operating conditions. The thermostat valve automatically works in the cooling system. When the engine is started from cold, the thermostat valve prevents the flow of water from engine to radiator so that the engine readily reaches to its normal working temperature, after which it automatically comes into action. Generally, the thermostat valve does not permit the water below 70°C. the water cooling system using the thermostat valve.

18.Distributor:-The distributor consists of a housing, driving shaft with breaker cam, breaker plate with contact points, governor, condenser, rotor, advance mechanism and cap. The shaft is driven by the engine cam shaft directly or indirectly through the oil pump drive shaft. The drive shaft is rotated at half the engine speed in four-stroke engines. When the shaft moves, it opens and closes the breaker points. The breaker cam contains the same number of lobes as the number of cylinders in the engine. Arotor is mounted on the breaker cam which is carried by the drive shaft. The rotor connects the centre terminal of the cap with each outside terminal in turn, so that high voltage surges from the coil are directed first to one spark plug and them to another, according to the firing order.

19.ac mechanical pump:-This is a Diaphagm type pomp. The Diaphy is made of a great cotton imprega impregnated with synthtic high great robber having two value (NAV) ane made of bakelite which is So light to Keeps the enertia stresses minimum the drive of the pump is taken from camshaft by means of an Eccentric com the eccentric operate rocker arm while in Conjuction with Dinghy nowon spring pushes the diaphangen op op and down during Diaphagm which causes movement the inlet side to goes though the strainer to casues vacum in the chamber open and the fuel than the chamber. The next upward movement of the Diaphagm causes the inlet valve to close while the outlet valve open and feel goes to the Carburetor float.

20.Lubricating system:-    wet sump lubricating System (ii) Dry Sump lubricating system. Buttom of the Crankcase Contains and oil Pan or Sump

from which the lubricating oil is Pumped to verious Compained of the engine inside and outside both by the Lubricating pomp and after Lubricating the parts of the engine lubricating oil flows back to the pump by gravity. There are 3 vanities types of wet Sump

Lubricating System @ stlash Lubricating 

System stlash and pressure system

Stlash lebnicating system

This type of Lebricating system used in light duty engine. The lubricating cond a oil Change into the buttom of the crankcase maintained at pre-determined leal the oil is drawn Pump delivered to a distributing pipe into and slash through in stlasher on dipped is provided under the each conecting rod cap.stlash and pressione system

under pressureto main

The Lubricating oil is bearing, big end bearing and Encamshaft bearing the oil also Sopplied onder pressure bearing also do all pipe and Crank Pin Lubricated by the stash. Pressure feed system

main tamed engine oil Pressite of both Low idle and high Idle of the hole is driving from the center of each crank pin. to the center of in adjusting of main Journal through which oil Chaakpass to main bearing to crank pin

(2) Day Sump Lubricating Budem

an In this system oil is cooked in external tank and oil Pump Grows oil from the supply tank circulate is under Pressure to the various bearing of the engine dripping oil the ginder bening into the Semp is removed by and Scave ging pomp which in trom the all is first to filter cand fed back to supply tanko the exparity of sewering pump this always batter than Lubricating oil pump a separate Oil Cooler provided to ree lubricating oil. 

1 Gravity

2) The flash point

3) viscosity

4 Cloud Point

5 Pour point

6) Carbon residue test

7 Ash test 

8) Precitition Number

All details about engine components in automobile.