Tuesday, 12 November 2019

Group 4 result check it now


Tamil Nadu Public Services Commission (TNPSC) conducts the combined civil services examination - 4 (Group-IV )was conducted dated on 1-9-2019  and the result was published to evening  below link is direct link you can check your link without any traffic all the best fnds







http://www.tnpsc.gov.in/Resultget-CCSE_IV_2K19.


htmlhttp://www.tnpsc.gov.in/Resultget-CCSE_IV_2K19.html
Technical world 

Monday, 11 November 2019

Mother is the super power






"Mother" is not just a word.

Everything we have learned in this world is from our mother
When I speak to her, she teaches to speak, only in poverty and in the way of integrity.

Anger of the evil demon, the absence of God's noble creative mother only such quality anywhere else in the annals view available priceless life lesson Mother only in the form that we learn, we are able, atomic than the excess energy is Mother's loving policy of the tower's beauty enjoys world, Enoch foundation of the sacrifice do not know Yes we have a tower height to reach the Nama My mother not only withstand the foundation.
Even though you are like a ghost, we can use our body, material and spirit

The only reason anyone in this world who has struggled with the sixth sense is the seventh sense is that he will take medication even before we feel pain in our body.

There is no obedience to slavery from an early age, it is only Mother who sows within us the human dignity.
Edison's declaration of foolishness in the eyes of the world made the world wonder

Mariappan was the only asset of the Paralympics to win gold in the excluded community

She is a mother
She is the only one who can carry the burden of life on her head to carry the crown load on our heads

Only the world-renowned editor, who knew the author,
There are students who have lost their education but there is no one who is affectionate
Mother only has the power to turn grievances into subjectivities. Therefore, I conclude my speech by saying that the head of our life is the best teacher and mother.
Thank you and good bye

Sunday, 10 November 2019

Spark Plug in IC Engines


Spark Plug in IC Engines

A spark plug in IC engines is a device used to produce spark for igniting the charge of petrol engines. It is always screwed into the cylinder head. It is, usually, designed to withstand a pressure upto 35 bar and operate under a current of 10 000 to 30 000 volts. The spark plug gap is kept from 0.3 mm to 0.7 mm.

Super chargers by prof moses dhilipkumar


Super charger acts as an air compressor. It is used to increase the density and pressure of the air that is supplied to the internal combustion engine. In the engine, during the intake of the cycle it takes more oxygen and burn more fuel to accomplish the work. This is due the power increase.
By using the belts, gears, shafts, chains all of these are connected to the engines crank shaft to produce super charge.
We can see two types of the super chargers. To that matter after super charging, the air enters into the engine. After compression the pressure in the air is compressed and it super charges the system by 1.5 to 2 times to increase the entry of the pressure.
In one type of the super charger the engine shaft is mechanically linked to the shaft. The shaft energy must turn into useful work input for the super charger.
In another type of the super charger the compressor is attached to the turbine. Exhaust gas must be allowed to enter into the turbine. The turbine drives the super charger; this type of super charger is known as the turbo 
Super chargers
Super charger drive types:
They are divided into mechanical, exhaust gas turbine and other types:
Mechanical drives are divided into four types they are belt drive, chain drive, direct drive and gear drive.
Exhaust gas turbines are divided into two types they are radial turbine and axial turbine.
And the other type of the drives is electrical motor and auxiliary power unit.
Advantages of supercharger:
  • The work output and the overall efficiency of the engine must be increased by 50% of the supercharger.
  • At the higher heights, the low density air is converted into the normal density air.
  • In the supercharge engine the specific fuel consumption is saved
  • In the volumetric efficiency of the super charger engine will be higher
  • To run the super charger, exhaust gas must be re-circulated in the engine. In this case the work input will be increases.
  • In the super charged engine the scavenging is improved.

Disadvantages of supercharger:
  • On the engine, different moving parts are observed like the thermal stress, mainly on the bearing of the engine shafts.
  • So it results in the wear and tear in the moving parts
  • We need to replace the parts frequently in the engine
  • During the time of compression stroked by the piston there is a leakage of the air in the super charge engine
  • Due to the super charging, the temperature of the air entering the engine cylinder will be higher.
  • The detonation tendency of the engine increases.
  • In the petrol engine, the detonation reduces so inter coolers are used to increases the size of the engine.






Saturday, 9 November 2019

Hydraulic Turbines by proff moses dhilipkumar


Hydraulic Turbines

hydraulic turbine is a machine which converts the hydraulic energy into mechanical energy. The hydraulic turbines are also known as water turbines. Following two types of hydraulic turbines are important.
1.     Impulse turbine
2.     Reaction turbine
In an impulse turbine, the total energy at the inlet of a turbine is only kinetic energy. The pressure of water both at entering and leaving the vanes is atmospheric. It is used for high head of water. A Pelton wheel is a tangential flow impulse turbine.
In a reaction turbine, the total energy at the inlet of a turbine is kinetic energy as well as pressure energy. It is used for low head of water. The Francis and Kaplan turbines are inward flow and axial flow reaction turbines respectively.






Bolt | Types, Parts, Manufacturing, Material Selection, Applications by moses dhilipkumar

Bolt | Types, Parts, Manufacturing, Material Selection, Applications




A bolt is a type of threaded fastener (like a screw) and is a male part. It is generally made of a metal. It is used to keep two or more hardware parts together (in a specific position).

Shank of the bolt is only partially threaded, just to accommodate a nut.

A bolt is sometimes also known as through bolt.

Note: Those who don’t know ‘shank’. It is discussed later in this article.

Note: Those who don’t know ‘What is a fastener?’. A fastener is a hardware device which mechanically affixes or joins two or more parts together.

However, there are many similarities between bolts and screws, there are some differences too.

Differences between screws and bolts
You can find some differences between screws and bolts, just by looking above figures. Below are some other differences.

A screw can have a tapered shank but a bolt can’t because it has to be assembled with a nut
Bolt require nut to have a grip on the joining parts but screw doesn’t.


Bolts are used to assemble two non-threaded parts together (unlike screw).
Screws are smaller in size when compared to bolts.
Screws have a large variety of head whereas bolts have either hexagonal or square head.

As shown in above diagram a bolt can be divided into following parts.

Head: It is the part of a bolt from where a spanner can hold it (to make it tight or loose).
Shank: A bolt can be broadly divided into two parts head and shank. Shank is partially threaded (as shown in figure) to accommodate a nut.


Grip length: It is the part of bolt that accommodates the parts which are to be assembled. Grip length should be equal to the combined thickness of joining parts.
Thread length: It is the part of bolt that accommodates the nut.
Nominal length: It is the sum of thread length and grip length (as shown in figure).
Type of bolt heads
Following are some most common types of bolt heads

Hexagon flange head
Hexagon (trimmed) head
Indented hexagon washer head
Indented hexagon head
Square shoulder head
Types of bolts
Following are some most common types of bolts

U-Bolt
Shoulder bolt or Stripper bolt
Sex bolt or Chicago Bolt
Rock bolt
Lag bolt
J bolt
Hex bolt
Hanger bolt
Elevator bolt
Carriage bolt
Arbor bolt
Anchor bolt
Flange bolt
Machine bolt
Plow bolt
Square head bolt
Stud bolt
Timber bolt
T-head bolt
Toggle bolt
Selection of bolt material
Following materials are generally used for manufacturing the bolts


Nylon Bolts: They are lightweight and water resistant
Bronze and Brass Bolts: They are water resistant
Stainless Steel Bolts: They have good strength and are corrosion resistant
Steel Bolts: They have good strength
Titanium Bolts: They are strong, light and corrosion resistant
Plastic Bolts: They are inexpensive and corrosion resistant. They are generally used for light loads.
Copper alloy Bolts: They are wear resistant and have good load capacity.
Aluminium Bolts: They are thermally and electrically conductive. They are light and easy to manufacture.
Apart from above material, sometimes finishing material is also applied to the bolts. Finishing material provides durability and corrosion resistance to the bolt. Here are some finishing materials used for bolts.

Zinc: Its coating acts as a sacrificial anode, protecting the underlying metal. It is applied as fine white dust.
Black oxide: Its coating is mostly used for aesthetic purpose. It does not enlarge the dimensions of the bolt. It is a processed black rust.


Chrome: Its coating gives a bright, reflective finish. It is decorative and very durable. It is applied by electroplating.
Manufacturing of Bolts
There are three major steps in the manufacturing a bolt.

Heading
Thread rolling
Coating
Bolts are normally made from wire. The wire is then cut to the proper length for the type of bolt being made. Heading produces the head of the bolt. The shape of the die in the machine dictates the features to be pressed into the bolt head for example a round head bolt uses a round die.

The threads are generally produced via thread rolling. However, some are machined.

Finally, a coating, such as electroplating with zinc or black oxide, is applied to prevent corrosion.

Applications of Bolt (or Through Bolt)
Bolt can be used in following conditions

When the parts that are fastened, require frequent dismantling and reassembly.
When the parts that are fastened, are made of material which is too weak to make durable threads.
When the parts that are fastened have medium thickness. For example, beams, flanges or plates etc.


When there is a place available for bolt head and nut.
When there is a place available for spanner.
Relative advantages and disadvantages of screws and bolts
Screws are cheaper compared to bolts.
Bolts are good for frequent dismantling and reassembling, unlike screws.
Bolts carry load on a larger shank area when compared to screw

STARTING SYSTEM: COMPONENTS AND WORKING PRINCIPLES

STARTING SYSTEM: COMPONENTS AND WORKING PRINCIPLES

The engine can’t “start” rotational movement on its own. It needs an electric motor to get it up to a minimal RPM to run, then the engine can run under its own power. The starter is the biggest load on the vehicles electrical system. We cannot simply run all that current through the ignition switch, in most systems a relay is used to activate the starter solenoid, and the starter solenoid itself acts as another relay to engage the starter motor (explained later). Before electric starters, automobile owners needed to crank the engine over themselves! This was not ideal for any kind of quick getaway.

The starter motor is an electric motor that rotates your engine in order to allow the spark and fuel injection systems to begin the engine's operation under its own power. Typically, the starter is a large electric motor and stator coil mounted to the bottom (generally to one side) of the vehicle's transmission bell housing where it connects to the engine itself. The starter has gears which mesh with a large flywheel gear on the backside of the engine, which turns the central crankshaft. Because this is a lot of physical weight and friction to overcome, starter motors are generally powerful, high-speed motors and use an ignition coil to ramp up their power before engaging.

COMPONENTS OF STARTING SYSTEM

1. Battery

The automotive battery, also known as a lead-acid storage battery, is an electrochemical device that produces voltage and delivers current. In an automotive battery, we can reverse the electrochemical action, thereby recharging the battery, which will then give us many years of service. The purpose of the battery is to supply current to the starter motor, provide current to the ignition system while cranking, to supply additional current when the demand is higher than the alternator can supply and to act as an electrical reservoir.

2. Ignition Switch

The ignition switch allows the driver to distribute electrical current to where it is needed. There are generally 5 key switch positions that are used:

1. Lock- All circuits are open ( no current supplied) and the steering wheel is in the lock position. In some cars, the transmission lever cannot be moved in this position. If the steering wheel is applying pressure to the locking mechanism, the key might be hard to turn. If you do experience this type of condition, try moving the steering wheel to remove the pressure as you turn the key.

2. Off- All circuits are open, but the steering wheel can be turned and the key cannot be extracted.

3. Run- All circuits, except the starter circuit, are closed (current is allowed to pass through). Current is supplied to all but the starter circuit.

4. Start- Power is supplied to the ignition circuit and the starter motor only. That is why the radio stops playing in the start position. This position of the ignition switch is spring-loaded so that the starter is not engaged while the engine is running. This position is used momentarily, just to activate the starter.

5. Accessory- Power is supplied to all but the ignition and starter circuit. This allows you to play the radio, work the power windows, etc. while the engine is not running.

Most ignition switches are mounted on the steering column. Some switches are actually two separate parts;

* The lock into which you insert the key. This component also contains the mechanism to lock the steering wheel and shifter.

* The switch which contains the actual electrical circuits. It is usually mounted on top of the steering column just behind the dash and is connected to the lock by a linkage or rod.

3. Neutral Safety Switch

This switch opens (denies current to) the starter circuit when the transmission is in any gear but Neutral or Park on automatic transmissions. This switch is normally connected to the transmission linkage or directly on the transmission. Most cars utilize this same switch to apply current to the backup lights when the transmission is put in reverse. Standard transmission cars will connect this switch to the clutch pedal so that the starter will not engage unless the clutch pedal is depressed. If you find that you have to move the shifter away from park or neutral to get the car to start, it usually means that this switch needs adjustment. If your car has an automatic parking brake release, the neutral safety switch will control that function also.

4. Starter Relay

A relay is a device that allows a small amount of electrical current to control a large amount of current. An automobile starter uses a large amount of current (250+ amps) to start an engine. If we were to allow that much current to go through the ignition switch, we would not only need a very large switch, but all the wires would have to be the size of battery cables (not very practical). A starter relay is installed in series between the battery and the starter. Some cars use a starter solenoid to accomplish the same purpose of allowing a small amount of current from the ignition switch to control a high current flow from the battery to the starter. The starter solenoid in some cases also mechanically engages the starter gear with the engine.

5. Battery Cables

Battery cables are large diameter, the multi-stranded wire which carries the high current (250+ amps) necessary to operate the starter motor. Some have a smaller wire soldered to the terminal which is used to either operate a smaller device or to provide an additional ground. When the smaller cable burns, this indicates a high resistance in the heavy cable. Care must be taken to keep the battery cable ends (terminals) clean and tight. Battery cables can be replaced with ones that are slightly larger but never smaller.

6. Starter Motor

The starter motor is a powerful electric motor, with a small gear (pinion) attached to the end. When activated, the gear has meshed with a larger gear (ring), which is attached to the engine. The starter motor then spins the engine over so that the piston can draw in a fuel/ air mixture, which is then ignited to start the engine. When the engine starts to spin faster than the starter, a device called an overrunning clutch (Bendix drive) automatically disengages the starter gear from the engine gear.

Starter motor parts

1. Starter Solenoid

The starter solenoid sits on top of the starter motor and performs two main functions, it acts as a heavy-duty relay for the starter and it engages the starter pinion gear to the ring gear on the flywheel/flex-plate/torque converter. The solenoid has 3 terminals; a B+ terminal, an S terminal, and an M terminal. The B+ terminal is connected directly to the battery positive at all times. This wire is infused meaning that if there is a short to ground on this wire, there will be sparks until the battery is drained. The wire from the battery to the B+ terminal will be very thick because it needs to carry call the current necessary to turn the starter motor and overcome engine compression. The S terminal receives power from the ignition switch either directly or indirectly with a relay. The S terminal connects to two winding, the pull-in winding and the hold in the winding. These winding are simply coils of wire wrapped around a plunger, which when energized produce and electromagnet. The pull-in winding is made up of thicker winding and creates a strong electromagnet. It is grounded through the M terminal and starter motor. The hold-in winding is smaller and creates a weaker electromagnet. It is grounded directly to the starter case. The plunger sits in the middle of the winding and is held in place by a spring. The plunger gets pulled/held in by the winding when they are energized. At one end it is connected to a lever which forces the starter pinion gear to mesh with the ring gear. At the other end, when the plunger reaches the end of its travel, it pushes a contact disk which connects the B+ terminal to the M terminal which is connected to the starter motor. This energizes the starter motor and also causes the pull-in winding to stop flowing power. This is because once the contact disk connects B+ to M there is 12v on both sides of the pull-in winding and no ground. The hold-in winding continues to flow electricity and holds the plunger in place until the key is returns to the run position. The solenoid needs both windings to pull the plunger in but only the hold-in winding to keep it there. It takes much more effort to move the plunger to engage the starter than it does to hold it there. Since the pull-in winding is no longer necessary, it would only waste electrical power to continue to power it.

2. Starter Motor

The starter motor converts electric energy into rotational motion, using electromagnetism or electromagnetic repulsion. Most starters used in automotive today are permanent magnet starters. These starters have several permanent magnets placed inside the case around an armature. An armature is used to make an electromagnetic field of the same polarity as the permanent magnets, causing the armature to repel the magnets. Power from the M terminal and ground from the case is supplied to the commutator strip through the brushes. The commutator strips Are connected to each other through the armature windings, this causes an electromagnetic field to form around the armature strips that are flowing power. If power is fed to commutator strip 1, the ground is on commutator strip 5, power will have to travel through armature strips 2,3, and 4 to get to commutator strip 5. This will create a magnetic field around armature strips 2,3 and 4. To get the armature to rotate, a permanent magnet is placed near, but not right on top of where the electromagnetic field is formed. When the two like polarities repel, the armature begins to rotate. As the armature rotates, the brushes will contact the next commutator strips, keeping the electromagnetic field in one place (just next to the permanent magnet) but allowing the armature to spin. This is what creates the rotational movement necessary to start the engine. Starters may also have a planetary gear-set to reduce RPM and increase torque to the ring gear. Heavy-duty starters use field coils instead of permanent magnets. Basically, they make both magnetic fields using electromagnetism instead of relying on permanent magnets. These starters are much more powerful than a permanent magnet starter but they take up more space, are much heavier and cost more to produce.

3. Starter Drive Pinion

The starter drive pinion is held out mesh with the ring gear by a spring until the starter solenoid engages and moves the lever, pushing the starter pinion into mesh with the ring gear. When the engine starts, the operator allows the key to return to the run position. This cuts power to the starter solenoid, which allows the spring to push the plunger back to its normal position. The plungers lever will pull the starter drive pinion back, out of mesh with the ring gear. It is important that the starter drives the flywheel and not the other way around. This is why starter drives have a one-way clutch. The one-way clutch allows the starter to turn the flywheel, but if the flywheel starts to cause the starter pinion to turn faster than the armature, the one-way clutch will slip. This protects the starter from spinning too fast.

WORKING PRINCIPLES

To make an engine start it must be turned at some speed, so that it sucks fuel and air into the cylinders, and compresses it.

The powerful electric starter motor does the turning. Its shaft carries a small pinion (gear wheel) which engages with a large gear ring around the rim of the engine flywheel.

In a front-engine layout, the starter is mounted low down near the back of the engine.

The starter needs a heavy electric current, which it draws through thick wires from the battery. No ordinary hand-operated switch could switch it on: it needs a large switch to handle the high current.

The switch has to be turned on and off very quickly to avoid dangerous, damaging sparking. So a solenoid is used - an arrangement where a small switch turns on an electromagnet to complete the circuit.

The starter switch is usually worked by the ignition key. Turn the key beyond the 'ignition on' position to feed current to the solenoid.

The ignition switch has a return spring so that as soon as you release the key it springs back and turns the starter switch off.

When the switch feeds current to the solenoid, the electromagnet attracts an iron rod.

The movement of the rod closes two heavy contacts, completing the circuit from the battery to the starter.

The rod also has a return spring -when the ignition switch stops feeding current to the solenoid, the contacts open and the starter motor stops.

The return springs are needed because the starter motor must not turn more than it has to in order to start the engine. The reason is partly that the starter uses a lot of electricity, which quickly runs down the battery.

Also, if the engine starts and the starter motor stays engaged, the engine will spin the starter so fast that it may be badly damaged.

The starter motor itself has a device, called a Bendix gear, which engages its pinion with the gear ring on the flywheel only while the starter is turning the engine. It disengages as soon as the engine picks up speed, and there are two ways by which it does so - the inertia system and the pre-engaged system.

The inertia starter relies on the inertia of the pinion - that is, its reluctance to begin to turn.

The pinion is not fixed rigidly to the motor shaft - it is threaded on to it, like a freely turning nut on a very coarse-thread bolt.

Imagine that you suddenly spin the bolt: the inertia of the nut keeps it from turning at once, so it shifts along the thread of the bolt.

When an inertia starter spins, the pinion moves along the thread of the motor shaft and engages with the flywheel gear ring.

It then reaches a stop at the end of the thread, begins to turn with the shaft and so turns the engine.

Once the engine starts, it spins the pinion faster than its own starter-motor shaft. The spinning action screws the pinion back down its thread and out of engagement.

The pinion returns so violently that there has to be a strong spring on the shaft to cushion its impact.

The violent engagement and disengagement of an inertia starter can cause heavy wear on the gear teeth. To overcome that problem the pre-engaged starter was introduced, which has a solenoid mounted on the motor.

There's more to a car starter system: As well as switching on the motor, the solenoid also slides the pinion along the shaft to engage it.

The shaft has straight splines rather than a Bendix thread so that the pinion always turns with it.

The pinion is brought into contact with the toothed ring on the flywheel by a sliding fork. The fork is moved by a solenoid, which has two sets of contacts that close one after the other.

The first contact supplies a low current to the motor so that it turns slowly - just far enough to let the pinion teeth engage. Then the second contacts close, feeding the motor a high current to turn the engine.

The starter motor is saved from over-speeding when the engine starts by means of a freewheel clutch, like the freewheel of a bicycle. The return spring of the solenoid withdraws the pinion from engagement.