Fluid coupling is also known as hydraulic coupling is a
hydrodynamic device which is used to transfer rotational power from one shaft
to another by the use of transmission fluid. It is used in automotive
transmission system, marine propulsion system and in industries for power
transmission. It is used as an alternative for the mechanical clutch.
It was discovered by Dr. Hermann Fottinger. He patented his
discovery of fluid coupling and torque converter in the year 1950.
Main Parts
It consists of three main components
Housing: It is also known as the shell. It has oil-tight
seal around the drive shaft. It also protects the impeller and turbine from
outside damage.
Impeller or pump: It is a turbine which is connected to
the input shaft and called as impeller. It is also known as pump because it
acts as a centrifugal pump.
Turbine: It is connected to the output shaft to which the
rotational power is to be transmitted.
The impeller is connected to the prime mover (internal
combustion engine) which is a power source. The turbine is connected to the output
shaft where rotation power is needed to be transmitted. The impeller and
turbine is enclosed in an oil-tight sealed housing. The housing consists of
transmission fluid.
The working principle of fluid can be easily explained by the
taking two fans in which one is connected to the power supply and other is not.
When the power switch is ON, the air from the first fan is starts to blow
towards the second fan (which is not connected to the power source). Initially when
the first fan is blowing at lower speed, it does not able to drive the second
fan. But as the speed of the powered fan increases, the speed of air striking the
blades of second fan also increases and it starts to rotate. After some time it
acquires the same velocity of that of the first fan.
On the same principle the fluid coupling works. In that the impeller
act as first fan and the turbine act as second fan. Both impeller and turbine
enclosed in an oil tight housing. The impeller is connected the input shaft of
the prime mover and the turbine with the output shaft. When the impeller is
moved by the prime mover, the fluid in housing experiences centrifugal force
and due to curved vanes of the impeller the fluid directed towards the turbine
blades. As the fluid strikes the turbine blades it starts rotating. With the
increase in the speed of impeller, the velocity of the turbine increases and
becomes approximately equal to the impeller speed. The fluid after passing
through the turbine blades again return to the impeller. Also Read: How Ignition Distributor Works?
Working of Fluid Coupling
As the prime mover moves, it rotates the impeller of the
coupling. The impeller acts as a centrifugal pump and throws the fluid outward
and directs it towards the turbine blade.
As the high moving fluid strikes the turbine blades, it also
starts rotating, after striking on the blades, the direction of the fluid is changed
and it is directed towards the impeller again. The blades of turbine are
designed in such a way that it can easily change the direction of the fluid. It
is the changing of direction of the fluid that makes the turbine to rotate.
As the impeller speed increases, the speed of the turbine
also increases. After sometime the speed of both impeller and turbine becomes
equal. In this way power is transmitted from one shaft to another by the use of
fluid coupling.
In same way torque converter works but the difference is that
it has stator placed in between impeller and turbine for torque multiplication.
For better explanation watch the video given below:
Application
It is used in automotive industries for the transmission of
power from the engine to the wheel as alternative of clutch.
It is used in marine propulsion systems.
It is used in various industries for the power transmission.
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A torque converter is a type of fluid coupling which is used to transfer rotating power from the engine of a vehicle to the transmission. It takes place of mechanical clutch in an automatic transmission. The main function of it is to allow the load to be isolated from the main power source. It sits in between the engine and transmission. It has the same function as the clutch in manual transmission. As the clutch separates the engine from the load when it stops, in the same way it also isolates the engine from load and keep engine running when vehicle stops.
Its main functions are:
1. It transfers the power from engine to the transmission input shaft.
2. It drives the front pump of the transmission.
3. It isolates the engine from the load when the vehicle is stationary.
4. It multiplies the torque of the engine and transmits it to the transmission. It almost doubles the output torque.
For understanding the working principle of torque converter, let’s take two fans. One fan is connected to the power source and other is not connected with power source. When first fan connected to the power source starts moving, the air from it flows to the second fan which is stationary. The air from the first fan strikes on the blades of the second fan and it also starts rotating almost at the same speed to the first one. When the second fan is stopped, it does not stop the first one. The first fan keeps rotating.
On the same principle the torque converter works. In that the impeller or pump acts as first fan which is connected to the engine and turbine act as the second fan which is connected to the transmission system. When the engine runs, it rotates the impeller and due to the centrifugal force the oil inside the torque converter assembly directed towards the turbine. As it hits turbine blades, the turbine starts rotating. This makes the transmission system rotate and the wheels of the vehicle moves. When engine stops, the turbine also stops rotating but the impeller connected the engine keeps moving and this prevent the killing of engine.
The impeller is connected to the housing and the housing connected to the engine shaft. It has curved and angled vanes. It rotates with the engine speed and consists of automatic transmission fluid. When it rotates with the engine, the centrifugal force makes the fluid move outward. The blades of the impeller are designed in such a way that it directs the fluid towards the turbine blades. It acts as centrifugal pump which sucks the fluid from the automatic transmission and delivers it to the turbine.
2. Stator:
The stator is located in between the impeller and turbine. The main function of the stator is to give direction to the returning fluid from the turbine, so that the fluid enters to the impeller in the direction of its rotation. As the fluid enters in the direction of the impeller, it multiplies the torque. So stator helps in the torque multiplication by changing the direction of the fluid and allows it to enter in the direction of the impeller rotation. The stator changes the direction of fluid almost upto 90 degree. The stator is mounted with a one way clutch that allows rotating it in one direction and preventing its rotation in other direction. Turbine is connected to the transmission system of the vehicle. And the stator is placed in between the impeller and turbine.
3. Turbine
Turbine is connected to the input shaft of the automatic transmission. It is present at the engine side. It also consists of curved and angled blades. The blades of the turbine are designed in such a way that it can change the direction of the fluid completely that strikes on its blades. It is the change in the direction of the fluid that forces the blades to move in the direction of the impeller. As the turbine rotates the input shaft of the transmission also rotates and made the vehicle to move. The turbine is also has a lock up clutch at its back. The lock up clutch comes into play when the torque converter achieves coupling point. the lockup eliminates the loses and improves the efficiency of the converter.
Working of Torque Converter
It has three stages of operations
1. Stall: During stall (stop) condition of the vehicle, the engine is applying power to the impeller but the turbine cannot rotate. This happens, when the vehicle is stationary and driver has kept his foot on the brake paddle to prevent it from moving. During this condition maximum multiplication of torque takes place. As the driver removes its foot from the brake paddle and presses the accelerator paddle, the impeller starts moving faster and this set the turbine to move. At this situation, there is a larger difference between the pump and turbine speed. The impeller speed is much greater than the turbine speed.
2. Acceleration: During acceleration, the turbine speed keeps on increasing, but still there is large difference between the impeller and turbine speed. As the speed of the turbine increases the torque multiplication reduces. During acceleration of the vehicle the torque multiplication is less than that is achieved during stall condition.
3. Coupling: It is a situation when the turbine achieved approximately 90 percent speed of the impeller and this point is called coupling point. The torque multiplication seizes and becomes zero and the torque converter behaves just like a simple fluid coupling. At the coupling point the lock up clutch come into play and locks the turbine to the impeller of the converter. This puts the turbine and impeller to move with the same speed. Lock up clutch engages only when coupling point is achieved. During coupling the stator also starts to rotate in the direction of the impeller and turbine rotation.
1. The maximum torque multiplication takes place during stalling condition.
2. The stator remains stationary before coupling point and helps in the torque multiplication. As the coupling attained, stator stops torque multiplication and starts rotating with the impeller and turbine.
3. Lock up clutch engages when coupling point is achieved and removes the power losses resulting in increased efficiency.
For better Explanation watch the video given below:
Advantages and disadvantages
Advantages
It produces the maximum torque as compared with the vehicle equipped with clutch.
It removes the clutch pedal.
It makes the job of driving a vehicle easier.
Disadvantages
Its fuel efficiency is low as compared with the vehicle with manual transmission.
Application
The torque converter is used in the vehicle that is equipped with the automatic transmission. It is also used in industrial power transmission such as conveyer drives, winches, drilling rigs, almost all modern forklifts, construction equipment, and railway locomotives.
Ignition Coil is (also called as spark coil) an induction coil which is used to increase the low voltage of battery (12 Volt) to a very high voltage ( about 50000 Volt) to produce spark within the engine cylinder for the combustion of fuel. It is used in automobile ignition system. We can also say that it is a short step-up transformer.
Working Principle
Ignition coil mainly consists of primary winding, secondary winding and an iron core. When the current through the primary winding makes and breaks repeatedly by contact breaker, it induces a very high voltage in the secondary winding (about 50000 V). This high voltage from the secondary winding is transferred to the spark plug through ignition distributor to produce spark within the cylinder.
Main Parts
The various main parts of ignition coil are
1. Primary Winding
2. Secondary Winding
3. Iron core
It is made up of thick copper wire having 200 to 300 turns insulated from each other
2. Secondary Winding
It is made up of thin copper wire having large number of turns about 21000 turns. The wires in the secondary winding are insulated from each other by enameled on the wire.
3. Iron Core
It consists of a laminated iron core. It is used to store energy in the form of magnetic field.
Construction
In ignition coil, the iron core is present at the center, and the primary and secondary windings surround it. The primary winding consists of thick wire of copper having 200 to 300 turn insulated from each other. On the other hand secondary winding is made up of thin copper wire having 2100 turns and insulated form each other by enamel on the wires and layers of oiled paper insulation.
Working
When the ignition switch is ON, the current through the primary winding starts to flow, this creates magnetic field in the iron core and around it.
As contact breaks in the contact breaker, the primary current collapses. This also collapses the magnetic field in the core. This sudden breaking of the magnetic field induces a very high voltage across the secondary winding. The magnitude of the voltage induced is about 50000 Volt.
This high voltage then is transferred to the spark plug through the ignition distributor to produce spark for the ignition.
It is mostly used in automobile ignition system and in those vehicles which is run by petrol engines such as scooter, motorcycles, cars etc.
It is not used in the vehicles running form diesel engine.
How to Identify Failure of Ignition Coil?
The various symptoms of its failure are
Backfiring
Starting problems
Less fuel economy
Engine misfiring
Vehicle stalling
Engine shaking
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Ignition Distributor is a mechanical device which is used to transfer the high voltage current produced by the secondary coil to the correct spark plugs in correct firing order and in correct amount of time.
It has a mechanically-timed ignition. It was the year 1910 in which the first reliable battery operated ignition system was developed by Delco (Dayton Engineering Laboratories Co.). And this ignition was developed by Charles Kettering.
It is a cover which protects the internal parts of the distributor. It has one post for each cylinder and in contact points types ignition system it also has one central post which is connected to the ignition coil to receive the current from it.
Some engines have two spark plugs per cylinder; in that case the distributor has two leads per cylinder. In the wasted spark system, a single contact is used for two leads, but each lead connects one cylinder.
In General motors where high energy ignition (HEI) system used, there is no central post in the distributor cap. The ignition coil is placed on the top of the distributor. Inside the distributor cap, the plug terminals are arranged around the circumference of the cap on the basis of the firing order so that the secondary voltage current must be send to the correct spark plug at right time. The rotor rotates inside the distributor cap.
The rotor is present at the top of the distributor shaft. It is driven by the camshaft of engine and hence synchronized to it. The rotor is pressed against a carbon bush on the central terminal of the distributor cap. The central terminal of the distributor is connected to the ignition coil.
The rotor is made in such a way that its central tab is electrically connected to its outer edge so the current that is coming into the central terminal travels through the carbon bush point to the outer edge of the rotor.
As the camshaft rotates, it rotates the distributor shaft. Due to this the rotor attached to the distributor shaft also starts rotating. When the outer edge of the rotor passes to each internal plug terminal in distributor cap, it fires each spark plug in correct sequence.
3. Contact Breaker
It is mechanically designed breaker point. Its one end is fixed and other end is movable. It is attached to the breaker assembly. Its main function is to makes and breaks the primary circuit current.
When the lobes of the cam pushes the cam follower of the contact breaker, the points of the breaker which were touching each other moves apart and breaks the primary current to flow through the primary winding of the ignition coil.
4. Distributor Shaft
It is a shaft which lies in the middle of the ignition distributor . It is connected directly to the camshaft of the engine through a gear drive. It consists of a cam which is used to break the point of the contact breaker.
5. Cam
It is attached to the distributor shaft and rotates with it. It has lobes which are used to open the contact breaker point. The number of lobes is equal to the number of engine cylinder. As the cam rotates, it pushes the cam follower and the breaker points moves apart leads to breaking of current.
6. Capacitor
It is used to prevent the overheating of the contact point of the contact breaker. It helps in production of high voltage current by reverse the current flow through the primary coil.
7. Spark Advance Mechanism:
It is a mechanism which is used to advance the spark in the spark ignition engine. We have generally two types spark advance mechanism and i.e. centrifugal advance spark and vacuum spark advance mechanism.
Its main function is to ignite the fuel before the piston reaches the TDC. This allows the complete burning of the air-fuel mixture with in the cylinder and results in the maximum pressure on the piston.
Working
As the ignition distributor shaft rotates, it rotates the cam and rotor.
When the cam pushes the cam follower of the contact breaker, the contact points of the contact breaker opens and collapses the primary current through the primary winding.
This produces a high voltage current in the secondary winding. The high voltage current produced is transfer to the distributor’s central terminal.
The current from the central terminal reaches to the outer edges of the rotor through the carbon bush. As the rotor comes in front of the internal terminal of the spark plug in the distributor cap, the high voltage electrical pulses (or surge) pass to the spark plug and it produces a spark within the cylinder head.
The distributor produces spark in each of the spark plug in in correct sequence and in correct amount of time.
In this way the ignition distributor works.
For better explanation Watch the video given below:
Spark Plug is a device which is used to ignite the air fuel
mixture in the engine cylinder. They are generally used in petrol engine. For
the combustion of the fuel, we need spark to initiate the combustion.
Requirements
It must be reliable at high voltage transmission i.e. up to
40,000 V.
It must have good insulation capability even at temperatures
of 1000 0C, and prevention of arcing and flashover.
It must possesses resistance to thermal shock (Hot exhaust gases-cold
intake mixtures)
It must make pressure tight and gas-tight sealing with the
combustion chamber.
It must be capable to resist oscillating pressures up to approx.
100 bar.
It should have high mechanical strength for reliable
installation.
It must have good thermal conduction by insulator tip and
electrodes.
It must possess resistance to spark erosion, combustion
gases and residues.
It must be capable of preventing of build-up of deposits on
the insulator.
They are made with high quality materials to meet the above
requirements.
Plug Terminal: It
is the portion that is connected to the high tension cable coming from the
distributor cap. It conducts the high voltage to the central electrode.
Ceramic Insulator:
It is made up of Aluminum oxide ceramic and acts as an insulator. It separates
the central electrode from earth at up to 40000 Volts. It can be manufactured
in plain form or with profiles to prevent flashover.
Metal Body: it is
steel shell manufactured with precision rolled threads for a secure fit, and
easy installation and removal. It provides electrical ground to the cylinder
head and helps to cool plug by transferring heat to the cylinder head.
Central Electrode:
It is made nickel based alloys consists of a copper core enclosed in it. Depending
upon the type, the central electrode can be in platinum or iridium. The high
voltage is applied to the central electrode from the secondary winding through
the distributor.
Ground Electrode:
It is welded to the metal body of the SP. It makes spark path with the central
electrode. It is made up of nickel based alloys ( or iridium or titanium
reinforcement)
Sealing washer/ Gasket:
It makes sealing with the cylinder head and helps in heat dissipation.
Insulator tip: It
is extended into the combustion chamber. It has greater influence on the
thermal rating of the spark plug
Electrode Gap: It
is the distance in between the central electrode and ground electrode. The
electrode has crucial role in the spark generation. If an appropriate gap is
not provided to the plug than if cannot produce sufficient spark to ignite the
fuel and may leads to misfire.
Types of Spark Plug
On the basis of the relative operating temperature range of
the tip of the high tension electrode, it is divided into two types.
Hot spark plug:
It has long heat transfer path and a large area exposed to the combustion gases.
Cold spark plug:
It has short heat transfer path and small area exposed to the combustion
gasses.
Working
When a high voltage current from the distributor is passes
to the spark plug.
The central electrode and ground electrode is applied to a
very high voltage up to 40000 V.
Due to this high voltage difference between the central
electrode and ground electrode, the air in between the electrode gap gets
ionized.
The ionized gas becomes conductor and conducts current from
central electrode to the ground electrode producing spark.
The spark produced is used to ignite the air-fuel mixture in
the engine cylinder.
For better explanation of working watch the video given below:
Application
It is used in the petrol engines of scooters, motorcycles, cars, etc. where the petrol is burnt
with the help of spark.
Battery Ignition System is used in automobile to produce spark in the spark plug for the combustion of fuel in the I.C. engine. Here the main source for the spark generation is the battery. It is mostly used in light commercial vehicles.
Let’s us discuss the function of each components one by one
1. Battery
It is a device which provides electrical energy for the ignition. The battery is charged by dynamo driven by engine. Generally two types of batteries are used in spark ignition engine, lead acid battery & alkaline battery. The lead acid battery is used in light duty commercial vehicle whereas alkaline battery is used in heavy duty commercial vehicle.
2. Ignition switch
It is a switch which is used to ON or OFF ignition system. One end of the ignition switch is connected to the battery and the other with the primary winding through a ballast resistor.
3. Ballast Resistor
It is connected in series with the primary winding. It is present in between the ignition switch and ignition coil. The function of ballast resistor is to prevent the overheating of primary winding of ignition coil. How it does this? The Ballast Resistor is made of iron wire and iron wire has a property that its electrical resistance increases rapidly with small increase in temperature. If the current from the primary winding flows continuously, the temperature of the ballast resistor increases and this increases the electrical resistance and reduces flow of electric current through the primary winding. The reduction of current by ballast resistor prevents the overheating of the primary winding.
It is used to produce high voltage sufficient to generate spark across the electrodes of spark plug. It acts a step transformer and converts a 6 or 12 V of a battery into very high voltage of about 15000 to 30000 V.
It Consist of a soft iron core surrounded by two insulated coil, named as primary winding and secondary winding. The primary winding consists of 200-300 turns of 20 gauge wires capable of producing resistance of 1.15 ohm. The secondary winding consists of 21000 turns of 38-40 gauge enameled wire and it is sufficiently insulated to withstand high voltage.
One end of the primary winding is connected to the battery terminal through ballast resistor and ignition switch. And other end is connected with the contact breaker as well as secondary winding. In the case of secondary winding, its one end id connected to the central high tension terminal of the distributor. And other end is connected with the primary winding.
5. Contact breaker
It is a mechanical device which is used for making and breaking of the primary circuit of the ignition coil.
It has two metal points made up of tungsten and place against each other. These metal points have circular flat face of about 3mm diameter. Among the two metal points, one is fixed and other is moveable. The fixed contact point is being earthed by mounting it on the base of the contact breaker assembly. The movable contact point is attached to the spring loaded pivoted arm which is electrically insulated.
The pivoted arm generally has a heel or rounded part (cam follower) made up of some plastic material and attached in the middle of the arm. The heel is rest on the cam driven by the engine. Every time when the cam passes under heel, the contact points are forced apart and the circuit is broken. The pivoted arm is spring loaded and in the case when the points are not separated by the cams, it is held together by the spring force and closes the primary circuit. When the points are closed, the current flows through the primary circuit and it stops if open.
6. Capacitor
The capacitor used in the ignition system is similar to the electrical capacitor. The capacitor is an electrical device in which two metal plates are separated from each other through insulating materials (air).
It is connected in parallel with the contact breaker. It prevents the contact points of the contact breaker from being damage. If there is no condenser or capacitor used in the primary circuit, the high primary voltage caused by the collapse of the magnetic field around the primary winding would cause an arc across the breaker points. The arc produced would burn and destroy the points and would also prevent the rapid drop in primary current and magnetic field which is necessary for the generation of high secondary voltage.
7. Distributor
It is a device used in the Battery Ignition System to distribute the ignition pulses (surges) to the individual spark plug in a correct sequence and at the correct instant in time.
There are two types of distributor
1. Brush type: In the brush type distributor, it contains carbon brush carried by the rotor arm slides over the metallic segments embedded in the distributor cap.
2. Gap type: In this type of distributor the rotor arm pass very close to the segments of the distributor cap but do not touch it.
It also contains some other auxiliary units too. In lower part of the housing, it has a speed sensitive device or governor whose main function is to advance the spark with increase in the engine speed. Contact breaker assembly is present above this, which can be rotated to adjust the timing of the spark.
In the upper part of the housing, high tension distributor is located. It also carries the vacuum ignition governor which serves to retard the spark as the load on the engine increases. Each metallic segments of the distributor is connected to each spark plug.
As the rotor rotates, the contact point opens; this allows the high tension current to pass to the spark plug through the segments to which the spark plug is connected. The sequence in which the spark plug is connected to the distributor cap depends upon the firing order of the engine.
8. Spark Plug
The spark plug is used to generate sparks to ignite the air-fuel mixture in the combustion chamber. Each spark plug is connected to the distributor of the ignition system.
Working Of Battery Ignition System
In the Battery ignition system as the ignition switch is ON, the current from the battery starts to flow through the primary circuit through ballast register, primary winding and contact breaker.
The current flowing through the primary winding induces magnetic field around it. The more will be the current, the stronger will its magnetic field.
As the contact breaker opens, the current through the primary winding collapse and this immediate collapse in the current induces a voltage of about 300V in the primary winding. This voltage induced in the winding charges the capacitor to the much greater voltage than the battery. As the capacitor charged, the current through the primary winding stops and the current starts to flow to the battery form the capacitor. This reverses the direction of current and magnetic field in the primary winding. Due to the collapsing and reversing of the current and magnetic field, a very high voltage of about 15000 to 30000 V induced in the secondary winding.
The high voltage current induced in the secondary winding is transferred to the distributor through a high tension cable.
The distributor has a rotor that rotates inside the distributor cap. The distributor cap has metallic segments embedded into it. As the rotor rotates, it presses and opens the contact breaker point. This allows the high tension current to transfer to the spark plugs through the metallic segments.
As the high tension current reaches the spark Plug, it produces spark in the engine cylinder for the combustion of the air-fuel mixture.
For better explanation watch the video given below
Advantages
It provides good spark at low engine speed.
Low maintenance cost.
Disadvantages
In battery ignition system, battery is necessary for the ignition. It becomes difficult to start the engine when the battery is discharged.
Occupies large space
Efficiency of the system decreases as the engine speed increases.
Since the breaker contact points are continuously subjected to mechanical as well electrical wear which results in short maintenance intervals.
Application
The Battery Ignition system is used in light commercial vehicle such cars, buses motorcycles etc.
Water Jet Machining (WJM) also called as water jet cutting, is a non-traditional machining process in which high velocity jet of water is used to remove materials from the surface of the workpiece. WJM can be used to cut softer materials like plastic, rubber or wood. In order to cut harder materials like metals or granite, an abrasive material is mixed in the water. When an abrasive material is used in water for the machining process, than it is called as Abrasive Water Jet Machining (AWJM).
Working Principle
It is based on the principle of water erosion. When a high velocity jet of water strikes the surface, the removal of material takes place. Pure water jet is used to machine softer material. But to cut harder materials, some abrasive particles mixed with the water for machining and it is called as AWJM
It is used to circulate the water from the storage tank during the machining process. The pump delivers water to the intensifier at low pressure of about 5 bars. A booster is also used which increase the initial pressure of water to 11 bar before delivering it to the intensifier.
2. Hydraulic Intensifier
It is used to increase the pressure of water to a very high pressure. It receives the water from the pump at 4 bar and increases its pressure up to 3000 to 4000 bar.
3. Accumulator
It stores the high pressurized water temporary. It supplies that fluid when a large amount of pressure energy is required. It eliminates pressure fluctuation conditions in the machining process.
4. Mixing chamber or tube
It is a vacuum chamber where the mixing of abrasive particles into water takes place.
5. Control Valve:
It controls the pressure and direction of the water jet.
6. Flow Regulator or Valve
The flow of the water is regulated with the help of flow regulator.
7. Nozzle
It is device which is used to convert pressure energy of water into kinetic energy in water jet machining. Here nozzle converts the pressure of water jet into high velocity beam of water jet. The tip of the nozzle is made of ruby or diamond to prevent it from erosion.
8. Drain and Catcher System
After the machining, the debris and machined particles from the water is separated out with the help of drain and catcher system. It removes the metal particle and other unwanted particles from the water and sends it back to the reservoir for further use.
The water from the reservoir is pumped to the intensifier with the help of a pump.
The intensifier increases the pressure of the water from 5 bars to 3000 to 4000 bar. This high pressure water from the intensifier is moved to the nozzle as wells as in accumulator.
The accumulator stores the high pressure water and supplies it at any instant when it is required. It is used to eliminate the fluctuation of high pressure requirement of machining hard material.
The high pressure water is than passed to the nozzle where the high pressure energy of the water is converted into kinetic energy. A very high velocity jet of water (1000 m/s) comes out through the nozzle in the form of narrow beam.
abrasive such as garnet or aluminum oxide is mixed with water within the nozzle. A mixing chamber is there in the nozzle where the abrasives get mixed with the high pressure water.
This high velocity jet of water when strikes the surface of the w/p removes the material from it.
The water jet after machining is gets collected by the drain and catcher system. Here the debris, metal particles from the water is removed and it is supplied to the reservoir tank.
The working will same for the water jet machining but abrasive particles is not mixed with the high velocity jet. only pure water jet comes out from the outlet of the nozzle.
Advantages
It has the ability to cut materials without disturbing its original structure. And this happens so because there is not heat affected zone (HAZ).
It is capable of producing complex and intricate cuts in materials.
The work area of in this machining process remains clean and dust free.
It has low operating and maintenance cost because it has no moving parts.
The thermal damage to the workpiece is negligible due to no heat generation.
It is capable of cutting softer materials (WJM) like rubber, plastics or wood as well as harder material (AWJM) like granite.
It is environment friendly as it does not create any pollution or toxic products.
It has greater precision of machining. The tolerances of order of ± 0.005 inch can be achieved easily.
Disadvantages
It is used to cut softer materials. But AWJM can cut harder material of limited thickness.
Very thick material cannot be machined by this process.
Initial cost of WJM is high.
Application
Water jet machining is used in various industries like mining, automotive and aerospace for performing cutting, shaping and reaming operations.
The materials which are commonly machined by water jet (WJM or AWJM) are rubber, textiles, plastics, foam, leather, composites, tile, stone glass, food, metals paper and much more.
WJM is mostly used to cut soft and easy to machine materials such as thin sheets and foils, wood, non-ferrous metallic alloys, textiles, honeycomb, plastics, polymers, leathers, frozen etc.
AWJM is typically used to machine those materials which are hard and difficult to machine. It is used to machine thick plates of steel, Al and other commercial materials, reinforced plastics, metal matrix and ceramic matrix composites, layered composites, stones, glass etc.
Beside Machining process the high pressure water jet is used in paint removal, surgery, cleaning, peening to remove residual stress etc.
AWJM can also be used to perform drilling, pocket milling, turning and reaming.
A combustion engine which has some vivid characteristic like high speed and high internal compression requires a system that produces very high ignition from the spark plug which is used as the source. The ignition system is the system which uses the spark plug as their source where electrical energy is input given to the spark plug.
There are three types of ignition system
Battery Ignition System
Magneto Ignition System
Electronic Ignition System
The Magneto Ignition System is a unique kind of Ignition System which has its own source to generate the necessary amount of energy for an automobile or a vehicle to work.
The source that generates energy in the Magneto Ignition System is the Magneto. Generally, a magneto is a small generator that works on electricity. When magneto is rotated by the engine, it produces the voltage. The higher the rotation, the greater will be the amount of voltage produced by the system. The magneto does not need any external power source such as a battery to kick start it as it itself is a source for generating the energy. There are two types of winding in it. It has a primary binding and a secondary binding.
In addition to this, magneto has 3 types based on its engine rotation
Armature rotating type
Magnet rotating type
Polar inductor type
In the armature rotating type, armature rotates between the stationary magnet whereas in the magnet rotating type, the armature is stationary and the magnets are rotating around the armature. In the polar inductor type, both the magnet and the windings remain stationary but the voltage is generated by reversing the flux field with the help of soft iron polar projections, called inductors.
2. DISTRIBUTOR
The distributor that is used in the Magneto Ignition System is also used in the multi-cylinder engine. The multi-cylinder engine is used for regulation of spark in a correct sequence in the spark plug. The surge of the ignition is distributed uniformly among the spark plugs. There are two types of distributors
Carbon brush type distributor
Gap type distributor
In carbon brush type, the rotor arm sliding over the metallic segment carry the carbon brush which is embedded inside the distributor cap or molded insulating material. This help to provide an electric connection with the spark plug. In gap type, the distributor electrode of rotor arm is close to the distributor cap, but no contact is made leading no wear for the electrode.
3. SPARK PLUG
The spark plug used in the this Ignition System has two electrodes that are parted from each other. A high voltage flows through it which causes the generation of the spark and used to ignite cylinders combustion mixture like oil. The electrode used in it is a steel shell and an insulator. The central electrode is connected to the supply of ignition coil and outer steel shell which is grounded insulating both of them. There is a small air gap that is left between the central electrode and the steel shell where the spark is generated. The central electrode is close when the spark is generated and hence it is made of a high nickel alloy that can withstand high temperature and resistances.
4. CAPACITOR
The capacitor used in the Magneto Ignition System is a simple electrical capacitor in which two metal plates are separated by an insulating material with a distance. Commonly, air is used as insulating material, but for a particular technical requirement, some high-quality insulating material is used.
Working Principle Of Magneto Ignition System
The working principle of the this ignition System is similar to the working principle of coil or battery ignition system except that in it magneto is used to produce energy but not the battery. Here are the following scenarios that occur in it.
When engine in the system starts it help magneto to rotate and thereby producing the energy in the form of high voltage.
The one end of the magneto is grounded through contact breaker and ignition capacitor is connected to it parallel.
The contact breaker is regulated by the cam and when the breaker is open, current flows through the condenser and charges it.
As the condenser is acting like a charger now, the primary current flow is reduced thereby reducing the overall magnetic field generated in the system. This increases the voltage in the condenser.
This increased high voltage in the condenser will act as an EMF thereby producing the spark at the right spark plug through the distributor.
At the initial stage, the speed of the engine is low and hence the voltage generated by the magneto is low but as the rotating speed of the engine increases, it also increases the voltage generated by the magneto and flow of the current is also increased. To kick start the engine, we can use an external source such as the battery to avoid the slow start of the engine.
The main advantage of the magneto ignition system over other ignition system is it doesn't require any external source to generate energy. It was managed at low tension and high tension. In the high tension, a huge amount of voltage is generated using a step-up transformer which can be used for engines like the airplane engine and low tension can manage this voltage letting it flow in the smallest part of the wiring and this avoid the leakage too.
Disadvantages
It has starting problem due to the low rotating speed at starting of the engine.
It is more expensive when compared to battery ignition system.
There is a possibility of misfire due to leakage because the variation of voltage in the wiring can occur.
Application
Here is the partial list of the applications of engines equipped with magneto ignition system.
Tractors, Oil Burners, and Outboard Motors
Washing Machines
Trucks and Cement Mixers
Buses
Airplane Engines
Power Units, Marine Engines and Natural Gas Engines
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Electrochemical machining (ECM) is a machining process in which electrochemical process is used to remove materials from the workpiece. In the process, workpiece is taken as anode and tool is taken as cathode. The two electrodes workpiece and tool is immersed in an electrolyte (such as NaCl). When the voltage is applied across the two electrodes, the material removal from the workpiece starts. The workpiece and tool is placed very close to each other without touching. In ECM the material removal takes place at atomic level so it produces a mirror finish surface.
This process is used to machine only conductive materials.
Working Principle
ECM working is opposite to the electrochemical or galvanic coating or deposition process.
During electrochemical machining process, the reactions take place at the electrodes i.e. at the anode (workpiece) and cathode (tool) and within the electrolyte.
Let’s take an example of machining low carbon steel which is mainly composed of ferrous alloys (Fe). We generally use neutral salt solution of sodium chloride (NaCl) as the electrolyte to machine ferrous alloys. The ionic dissociation of NaCl and water takes place in the electrolyte as shown below.
As the potential difference is applied across the electrode, the movement of ions starts in between the tool and w/p. The positive ions moves towards the tool (cathode) and negative ions move towards the workpiece.
At cathode the hydrogen ions takes electrons and gets converted into hydrogen gas.
In the same way the iron atoms comes out from the anode (w/p) as Fe++ ions.
Within the Electrolyte, the sodium ions combines with Hydroxyl ions and form sodium hydroxide and ferrous ion combine with Chloride ions and forms ferrous chloride. Also iron ions combine with hydroxyl ions and forms Iron hydroxide.
In the electrolyte the FeCl2 and Fe(OH)2 produced and gets precipitated in the form of sludge and settle down. In this way material is removed from the workpiece as sludge.
The various reactions taking place in the Electrochemical machining process are in the figure given below.
Schematic Diagram of ECM Reactions
Main Equipment of ECM
The ECM system has the following modules
Power Supply
Electrolyte filtration and delivery system
Tool Feed system
Working Tank
Schematic Diagram of Electrochemical Drilling Unit
Working Process of Electrochemical Machining
First the workpiece is assembled in the fixture and tool is brought close to the workpiece. The tool and workpiece is immersed in a suitable electrolyte.
After that, potential difference is applied across the w/p (anode) and tool (cathode). The removal of material starts. The material is removed as in the same manner as we have discussed above in the working principle.
Tool feed system advances the tool towards the w/p and always keeps a required gap in between them. The material from the w/p is comes out as positive ions and combine with the ions present in the electrolyte and precipitates as sludge. Hydrogen gas is liberated at cathode during the machining process.
Since the dissociation of the material from the w/p takes place at atomic level, so it gives excellent surface finish.
The sludge from the tank is taken out and separated from the electrolyte. The electrolyte after filtration again transported to the tank for the ECM process.
Ultrasonic Machining (USM) also called as ultrasonic vibration machining is a machining process in which material is removed from the surface of a part by low amplitude and high frequency vibration of a tool against surface of material in the presence of abrasive particles.
The motion of the tool takes place vertically or orthogonal to the surface of the part. The tool travel with an amplitude of 0.05 mm to 0.125 mm (0.002 in to 0.005 in).
Slurry is formed by mixing fine abrasive grains in the water. This slurry is made to flow across the w/p and the tip of the tool during machining process. The abrasive gain particles in the slurry helps in the removal of the material form the surface of the w/p. The grain sizes of the abrasive material are typically ranges from 100 to 1000. The smaller grains (i.e. higher number of grain) results in smooth surface finishes.
This machining process is usually used to machine brittle materials and materials that have high hardness.
Working Principle
An electric current at high frequency (in ultrasonic range i.e. 18 kHz to 40 kHz) is used to generate mechanical vibration of low amplitude and high frequency. The mechanical vibration generated is used for machining the surface of a part in the presence of abrasive grain particles in the form of slurry. The slurry flows across the tool and workpiece. When the tool presses against the w/p, the slurry containing abrasive particle chips off the materials from surface.
The ultrasonic machining machine consist of two main parts transducer and sonotrode (also called as horn), connected to an Electronic control unit with cables.
The function of various parts are described below
1. Transducer: The transducer mainly consists of a cylinder which is made up of piezoelectric ceramic. It converts electrical energy into mechanical vibration. Transducer then vibrates sonotrode at low amplitude and high frequency.
2. Sonotrode: It is made of low carbon steel. One end of it is connected with the transducer and other end contains tool. The sonotrode vibrates at low amplitude and high frequency and removes material from the w/p by abrasion where it contacts it.
3. Control Unit: The control unit consists of an electronic oscillator which produces an alternating current at high frequency. The frequency produced is usually in between 18 kHz to 40 kHz in ultrasonic range.
Types of USM
1. Rotary Ultrasonic vibration machining (RUM): In RUM, a vertically rotating tool is allowed to revolve about the axis of the sonotrode. The surface of the tool is impregnated with diamonds that is used to grind down the surface of the part. Abrasive slurry is not used in this type of machine for material removal.
2. Chemical-Assisted USM: In this machining, a chemically reactive abrasive fluid is used for the machining process.
Working
The transducer and sonotrode is attached to control unit with a cable.
The control unit has an electronic oscillator that produces an alternating current with high ultrasonic frequency ranges in between 18 kHz to 40 kHz.
This high frequency alternating current is supplied to the transducer. The transducer converts this alternating current into mechanical vibration and transmits this mechanical vibration to the sonotrode attached to it.
The sonotrode is vibrated by the transducer with low amplitude and high frequency. When this vibrating sonotrode strikes the surface of the w/p, it removes the material form it. The slurry flows in between the tool and workpiece and helps in the removal of the material from the surface.
The slurry used in the ultrasonic machining contains 20 % to 60% of water by volume, aluminum oxide, boron Carbide and silicon carbide particles.
This is how ultrasonic machining works.
Advantages
This machining method is capable of machining brittle and hard material with high precision.
It can machine fragile materials such glass and non-conductive metals which are not machined by non-traditional methods such as electrochemical machining or electrical discharge machining.
It is capable of producing high tolerance parts.
There is no distortion produced in the worked material. And this is because, no heat is generated by the sonotrode against the w/p.
There is no change observed in the physical properties of the material.
The machined parts produced require fewer finishing process because of absence of burrs in the process.
Disadvantages
The metal removal is slow due to micro chipping or erosion mechanism.
The wear of sonotrode tip occurs more quickly.
The machining of deep holes is not easy by this method because of the inability of abrasive slurry to flow at the bottom of the hole (Except rotary ultrasonic machining).
Ultrasonic vibration machining can be used only to machine materials that have hardness value atleast 45 HRC (HRC: Rockwell Scale to measure hardness of a material).
Application
It is commonly used to machine brittle and hard materials. Glass, carbides, ceramics, precious stones and hardened steels are the most common materials machined by USM.
It is very precise machining method and used in the creation of micro-electrochemical system components like micro-structured glass wafers.
