Stainless Steel

Stainless steel also known as inox steel, is a metal alloy formed by alloying chromium with steel, It generally contains 10.5% chromium content by mass. Stainless steel does not readily corrode, rust or stain with water, because the chromium makes an oxide film on the surface of the steel.

stainless steel rods

There are other elements used to make stainless steel as well, including nickel, nitrogen and molybdenum. Bringing these elements together forms different crystal structures that enable a variety of properties in machining, welding and forming.

stainless steel pipes

High oxidation-resistance in air at ambient temperature is normally achieved with additions of a minimum of 13% by weight chromium, and up to 26% is used for harsh environments. The chromium forms a passivation layer of chromium(III) oxide (Cr₂O₃) when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous. The layer is impervious to water and air, protecting the metal beneath. Also, this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, such as aluminium and titanium. Corrosion-resistance can be adversely affected if the component is used in a non-oxygenated environment.

Types of stainless steel 

There are four major types of stainless steel:

•  Austenitic stainless steel: Austenitic  stainless steels have an austenitic crystalline structure, which is a face-centered cubic crystal structure. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy.

• Ferritic stainless steel: Ferritic stainless steels generally have better engineering properties than austenitic grades, but have reduced corrosion resistance, because of the lower chromium and nickel content. Most compositions include molybdenum; some, aluminium or titanium.

• Martensitic stainless steel: Martensitic stainless steels are not as corrosion-resistant as the other two classes but are extremely strong and tough, as well as highly machinable, and can be hardened by heat treatment. Martensitic stainless steel contains chromium (12%–14%), molybdenum (0.2%–1%), nickel (less than 2%), and carbon (about 0.1%–1%) giving it more hardness but making the material a bit more brittle. It is quenched and magnetic.

• Duplex stainless steel: It have a mixed microstructure of austenite and ferrite. Duplex stainless steels have roughly twice the strength compared to austenitic stainless steels and also improved resistance to localized corrosion, particularly pitting, crevice corrosion and stress corrosion cracking. They are characterized by high chromium (19%–32%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels.

 Applications:

• cookware, 

• cutlery, 

• household hardware,

•  surgical instruments,

•  industrial equipment e.g, in sugar refineries,

•  as an automotive and aerospace structural alloy,

•  construction material in large buildings,

•  Storage tanks and tankers used to transport orange juice and other food are often made of stainless steel, because of its corrosion resistance.

Brass forging

Brass forging is a process in which a forging press places places extreme pressure on a single piece of brass that has been heated to about 815 degrees C. The softened metal is then forced, beaten, and shaped to produce a part made from a single piece of brass and free of imperfections.

The brass forging process actually makes the metal around 15% stronger than mold cast parts as the process does not change the structure of the metal. Extruded brass stock is made into a shape already close to the final part that it will be forged into when the brass is heated.

forged brass products

The various types of brass forging include closed die forging, open die forging, cold forging, and seamless rolled ring forging:

• Closed die forging, also known as impression-die forging, utilizes two or more dies made in the shape of the part desired. The brass is heated until it becomes malleable, or reaches a plastic state, and is then compressed by the die machine. This forging process creates brass parts that have enhanced density, aligned grain flow, and high strength. Closed die brass forging produces extremely strong and durable products. 

• In open die forging the heated, malleable brass is not confined in a die or mold. Instead, it is accomplished with the use of two flat die surfaces with no type of impression. This type of brass forging is typically used to create and shape very large single pieces of brass up to 36,000 kg or more.

• Cold brass forging only requires that the brass be heated to a few hundred degrees. Cold forging is typically used to create things like coins, automotive steering parts, anti-lock braking systems, and other smaller parts. This process produces parts that require high strength and close tolerances. 

• Rolled ring forging uses round, open ring-shaped parts that were shaped using the open die forging process. This type of forging is accomplished through the forced pressure of two axial rolls, a driver roll and an idler roll. The ring of brass is rotated by the idler roll while applying pressure to the inside of the ring. The driver roll applies pressure to the outside edge of the ring. As the process progresses, the ring becomes flatter until the desired ring diameter is achieved.

Advantages

• Forging brass parts reduces metal scrap and is faster than machining the parts. 

• The forging process also produces a pore-free surface which makes for a more attractive brass part. 

• It produces strong and durable products.

Electromagnet

An electromagnet is a magnet in which the magnetic field is produced due to the flow of electric current. The magnetic field disappears when the current is turned off.

electromagnet

An electric current flowing in a wire creates a magnetic field around the wire. To concentrate the magnetic field, in an electromagnet the wire is wound into a coil with many turns of wire lying side by side. The magnetic field of all the turns of wire passes through the center of the coil, creating a strong magnetic field there. A coil forming the shape of a straight tube or helix is called a solenoid. Much stronger magnetic fields can be produced if a ferromagnetic material, such as soft iron, is placed inside the coil. The ferromagnetic core increases the magnetic field to thousands of times the strength of the field of the coil alone, due to the high magnetic permeability ( μ ) of the ferromagnetic material. This is called as ferromagnetic-core or iron-core electromagnet. The direction of the magnetic field through a coil of wire can be found from a form of the right-hand rule. If the fingers of the right hand are curled around the coil in the direction of current flow through the windings, the thumb points in the direction of the field inside the coil. The side of the magnet that the field lines emerge from is defined to be the north pole.

 

The main advantage of an electromagnet over a  permanent magnet is that the magnetic field can be rapidly varied over a wide range by controlling the amount of electric current. But, a continuous supply of electrical energy is required to maintain the field.

Side effects in electromagnets

• Ohmic heating: The power consumed in a DC electromagnets is due to the resistance of winding, and is dissipated as heat. This heating is called ohmic heating and in large electromagnets require cooling water circulating through pipes in the windings to carry off the waste heat. Since power dissipation, P = I²R, increases with the square of the current but only increases approximately linearly with the number of windings, so the power lost in the windings can be minimized by reducing I and increasing the number of turns N . For example halving I and doubling N, halves the power loss. This is the one reason most electromagnets have windings with many turns of wire.

•  Lorentz forces: In powerful electromagnets, the magnetic field exerts a force on each turn of the windings, due to the Lorentz force (qv *B) acting on the moving charges within the wire. The Lorentz force is perpendicular to both the axis of the wire and the magnetic field. It has two effects on an electromagnet's windings:

• The field lines within the axis of the coil exert a radial force on each turn of the windings, tending to push them outward in all directions. This causes a tensile stress in the wire.
• The leakage field lines between each turn of the coil exert a repulsive force between adjacent turns, tending to push them apart.

• Core losses: In alternating current (AC) electromagnets, used in transformers, inductors, AC motors and generators, the magnetic field is constantly changing. This causes energy losses in their magnetic cores that are dissipated as heat in the core. The losses occurs due two processes:  

• Eddy currents:  From Faraday's law of induction, the changing magnetic field induces circulating electric currents inside nearby conductors, called eddy currents. The energy in these currents is dissipated as heat in the electrical resistance of the conductor, so they are a cause of energy loss. Eddy currents are closed loops of current that flow in planes perpendicular to the magnetic field. The energy dissipated is proportional to the area enclosed by the loop. To prevent them, the cores of AC electromagnets are made of stacks of thin steel sheets, or lamination, oriented parallel to the magnetic field, with an insulating coating on the surface.
• Hysteresis losses: Reversing the direction of magnetization of magnetic domains in the core material each cycle causes energy loss, because of the coercivity of the material. These loses are called as Hysterisis. To minimize this loss, magnetic cores used in transformers and other AC electromagnets are made up of "soft" or "low coercivity" material, such as silicon steel or soft ferrite.

 Uses of electromagnets

Electromagnets are widely used in electric and electromechanical devices, including:

• Motors and generators,
• Transformers,
• Electric bells and buzzers,
• Loudspeakers and earphones,
• Actuators,
• Magnetic recording and data storage equipment: tape recorders, VCRs, hard disks,
• Scientific instruments such as MRI machines and mass spectrometers,
• Particle accelerators,
• Magnetic locks,
• Magnetic separation equipment, used for separating magnetic from nonmagnetic material,
• Industrial lifting magnets,
• Electromagnetic suspension used for MAGLEV trains.

 

Permanent magnets

A magnet is a material that produces a magnetic field. This magnetic field is invisible but is responsible for the property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.

Permanent magnets are made out of substances like magnetite (Fe₃O₄), the most magnetic naturally occurring mineral, or neodymium, a powerfully magnetic synthetic substance. The Earth itself is a huge permanent magnet, though its magnetic field is quite weak relative to its size. Humans have used the magnetic field of the Earth for navigation since the compass was invented in ancient China.

Every permanent magnet generates a magnetic field, which circulates around the magnet in a distinct pattern. The size of the magnetic field is related to the size of the magnet and its strength. The easiest way to view a magnetic field generated by a permanent magnet is to scatter iron filings around a bar of  magnet, which quickly orient themselves along the field lines. 

Every permanent magnet has two poles, named north and south, Similar poles repel while opposite poles attract. It takes a lot of effort to hold repelling poles of a magnet together, while it takes a lot of effort to remove attracting poles.

Even the most powerful permanent magnet is not as strong as the stronger electromagnets, so their applications are limited, but they still have many uses. The most significant use is as refrigerator magnets, but magnets can be found everywhere, including your hard disk, ATM and credit cards, speakers and microphones, electric motors, and toys. Electric motors work through an interaction between an electromagnet and a permanent magnet.

Hydraulics

When we talk about hydraulics then a question arise in our mind that how could it works, and the answer is by using a pressurized liquid.

Hydraulic technology provides a more environmental friendly way to power everything from automobiles to heavy machinery through the use of liquid. The basic idea behind any hydraulic system is very simple: Force that is applied at one point is transmitted to another point using an incompressible fluid. 

Hydraulic systems are based on Pascal's Law,that pressure at any one point in a confined liquid is
the same in every direction and applies equal force on equal areas. So when we apply less force on smaller area then the liquid applies a greater force on larger area That's why hydraulic system is very popular in engineering field.

Pascal's law and Hydraulics

 

A hydraulic system contains a master cylinder connected with the lever and with delivery tank. The delivery tank stores the hydraulic liquid. The master cylinder is connected with secondary cylinders with hydraulic lines or pipes, These secondary cylinders are those points where the output is needed. So when we push the lever the piston pushes the incompressible hydraulic liquid and due to smaller area of pipes and in-compressibility the pressure of liquid increases and it reaches to the secondary cylinders and pushes them to get desired output. A drain line is also provided in every cylinder to drain the used liquid back to the delivery tank. The delivery tank or reservoir collects the used or fresh liquid and sends it to the master cylinder after passing through a filter and the whole process repeats itself.

 

An example of braking system powered by hydraulics

Some places where hydraulics are frequently used are:

•  Steering wheel,

• Brakes, 

•  Lifts,

•  Cranes, 

• Aircraft, etc

Some hydraulic fluids are:

•   Arnica, 

•  Tellus, 

• Durad, 

• Fyrquel, 

• Houghto-Safe, 

• Hydraunycoil, 

• Lubritherm Enviro-Safe,

•  Pydraul,

•  Quintolubric,

•  Reofos, 

• Reolube,

• Valvoline Ultramax,

• Skydrol. etc

Advantages:

• It uses incompressible liquid which results in a greater, more efficient & consistent work or power output. And minimal energy loss is experienced and work applied is directly transferred to the actuating surfaces.

• Hydraulic fluid operates very well in a very hot working environment, it is able to sustain its airworthiness viscosity, density & fluid temperature even if it subjected under extreme heat.

•  Hydraulic systems can perform on very heavy loads.

• They have a very high accuracy.

Disadvantages:

• Leakage is its major disadvantage.

• Maintenance  is very difficult.

• Hydraulic fluid is highly corrosive to most of the aircraft materials.

• If disposed improperly, a hydraulic fluid is an environmental risk.

• Mishandling and constant exposure to hydraulic fluid and its gas fumes without proper equipment and precautions is a health risk.

Gears

A gear is a rotating machine part having cut teeth or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine. Geared devices can change the speed, torque, and direction of a power source. An advantage of gears is that the teeth of a gear prevent slipping.

gears

Types of gears:

• External gear: An external gear is one with the teeth formed on the outer surface of a cylinder.

external gears

• Internal gear: An internal gear is one with the teeth formed on the inner surface of a cylinder or cone.

internal gears

• Spur gear: Spur gears are the simplest type of gear. They consist of a cylinder with the teeth projecting radially, the edge of each tooth is straight and aligned parallel to the axis of rotation. These gears can be meshed together correctly only if they are fitted to parallel shafts.

spur gears

• Helical gear: The leading edges of the teeth are not parallel to the axis of rotation, but are set at an angle. Since the gear is curved, this angling causes the tooth shape to be a segment of a helix. Helical gears can be meshed in parallel or crossed orientations. The angled teeth engage more gradually than do spur gear teeth, causing them to run more smoothly and quietly.

helical gears

• Bevel gear:  A bevel gear is shaped like a right circular cone with most of its tip cut off. When two bevel gears mesh, their imaginary vertices must occupy the same point. Their shaft axes also intersect at this point, forming an arbitrary non-straight angle between the shafts. The angle between the shafts can be anything except zero or 180 degrees.

bevel gears

• Hypoid:  Hypoid gears resemble spiral bevel gears except the shaft axes do not intersect. The pitch surfaces appear conical but, to compensate for the offset shaft, are in fact hyperboloids of revolution. Hypoid gears are almost always designed to operate with shafts at 90 degrees.

hypoid gears

• Crown:  Crown gears are a particular form of bevel gear whose teeth project at right angles to the plane of the wheel; in their orientation the teeth resemble the points of a crown. A crown gear can only mesh accurately with another bevel gear, although crown gears are seen meshing with spur gears. A crown gear is also sometimes meshed with an escapement such as found in mechanical clocks.

crown gears

• Worm gear: Worm gears resemble screws. A worm gear is usually meshed with a spur gear or a helical gear, which is called the gear, or worm wheel. Worm-and-gear sets are a simple and compact way to achieve a high torque, low speed gear ratio.

worm gears

• Rack and Pinion:  A rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely large radius of curvature. Torque can be converted into linear force by meshing a rack with a pinion: the pinion turns; the rack moves in a straight line. Such a mechanism is used in automobiles to convert the rotation of the steering wheel into the left-to-right motion of the tie rod.

rack and pinion gears

Springs

Springs are those mechanical devices which absorbs energy when a load is applied on it. It means it contracts when we apply a load on it and when the load is removed it comes to its original shape. So that  springs have very important role in mechanical industries.

There are several types of mechanical springs they are:

• compression spring, 
• extension spring, 
• torsion spring, 
• constant force spring, and
• belleville spring.

Compression springs are mechanical springs that oppose compression forces. It squeezes together to absorb the force and expands once the load has been removed. Compression springs are used in car suspensions.

compression springs

Extension springs are mechanical springs that stretch beyond their rest positions when a load is applied. After the load is removed, they contract back to their original size. Extension springs are used as screen door hinge or garage door hinge.

extension springs

Torsion springs are mechanical springs that rotate around an axis to create a load. As the load is released, the spring rotates back to its starting position. This type of spring is usually used in mouse traps.

torsion springs

A type of spring that releases a controlled amount of energy, instead of the quick burst associated with torsion springs, is the constant force spring. it is made of a band of steel that is wrapped around itself in the shape of a spiral. The mechanical springs that are found in clocks are typically constant force springs. they are also found in toy cars.

constant force springs

The belleville spring, also known as the belleville washer, is a flat, disk-shaped spring with a hole in the center. It is typically used with a bolt to maintain pretension, which reduces the stress on the bolt when a load is applied. It is generally used to support lager loads.

belleville spring

Wind Turbines

Wind turbine is a large rotating device which converts the wind energy into the mechanical energy. Wind turbine contains large blades which rotates on the impact of wind on it. If the mechanical energy is used to produce electricity, the device may be called a wind turbine or wind power plant. If the mechanical energy is used to drive machinery, such as for grinding grain or pumping water, the device is called a windmill or wind pump. And, it may be referred to as a wind charger when used for charging batteries.

There are two types of wind turbines classified according to their axis of rotation, they are:

• Horizontal axis,
• Vertical axis.

Horizontal axis:

Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator. Since a tower produces turbulence behind it, the turbine is usually positioned upwind of its supporting tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted forward into the wind a small amount.

Vertical axis:

Vertical-axis wind turbines (VAWT) have the main rotor shaft arranged vertically. The main advantages of this arrangement are that the turbine does not need to be pointed into the wind to be effective. This is an advantage on sites where the wind direction is highly variable. The main disadvantages include the low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient, the 360 degree rotation of the aerofoil within the wind flow during each cycle and hence the highly dynamic loading on the blade. With a vertical axis, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, hence improving accessibility for maintenance.

Spark plugs

Spark plug is a device used for the ignition of compressed air-fuel mixture in an internal combustion engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. The central electrode, which may contain a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil. The spark plug's metal shell is screwed into the engine's cylinder head and thus electrically grounded.

Spark plug construction:

A spark plug is composed of a shell, insulator and the central conductor.

Parts of plug:

• Terminal: The top of the spark plug contains a terminal to connect to the ignition system.
• Insulator:  The main part of the insulator is typically made from sintered alumina, a very hard ceramic material with high dielectric strength.
• Ribs: The physical shape of the ribs functions to improve the electrical insulation and prevent electrical energy from leaking along the insulator surface from the terminal to the metal case.
• Central electrode: The central electrode is connected to the terminal through an internal wire and commonly a ceramic series resistance to reduce emission of RF noise from the sparking. The tip can be made of a combination of copper, nickel-iron, chromium, or noble metals. The central electrode is usually the one designed to eject the electrons because it is the hottest part of the plug.

 Operation:

The plug is connected to the high voltage generated by an ignition coil. As the electrons flow from the coil, a voltage difference develops between the central electrode and side electrode. No current can flow because the fuel and air in the gap is an insulator, but as the voltage rises further, it begins to change the structure of the gases between the electrodes. Once the voltage exceeds the dielectric strength of the gases, the gases become ionized. The ionized gas becomes a conductor and allows electrons to flow across the gap. Spark plugs usually require voltage of 12,000–25,000 volts or more to 'fire' properly, although it can go up to 45,000 volts. They supply higher current during the discharge process resulting in a hotter and longer-duration spark.

Cascade system

In a cascade system a series of refrigerants with progressively lower boiling points are used in a series of single stage units. The condenser of lower stage system is coupled to the evaporator of the next higher stage system. The cascade system may be of 2-stage, 3-stage and so on. The two systems are connected with a cascade condenser or heat exchanger which acts as an evaporator for low temperature cascade and as a condenser for high temperature cascade. An example of refrigerant combination is the use of carbon dioxide in low temperature cascade and ammonia in high temperature cascade.

Applications of cascade system:

• Liquefaction of petroleum vapours,
• Liquefaction of industrial gases,
• Manufacturing of dry ice,
• Deep freezing, etc.

Electric Discharge Machining

Electric Discharge Machining is an unconventional machining as here tool doesn't touches the workpiece. The basic principle behind EDM is concept of current, as we know that current is also a form of heat, as if we applied current to any material it definitely gets heated. In EDM we use sparks to melt the metal from the workpiece.

The basic components an EDM are:

• Power generator and control unit
• Servo system to feed the tool
• Tool holder
• Dielectric reservoir, pump and circulation system

In EDM, a potential difference is applied between the tool and workpiece. Both the tool and workpiece are electrically conductive. The tool and workpiece are immersed in a dielectric medium. Generally, kerosene or deionized water is used as the dielectric medium. A gap is maintained between the tool and the workpiece, due to the applied potential difference between the gap an electric field is generated which produces sparks from tool to workpiece and due to this, local heat increases rapidly resulting in melting of the metal from the workpiece.Generally the workpiece is made anode as it melts faster than the cathode terminal.

Francis Turbine

The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts.

A Francis turbine comprises mainly the four components:

• Spiral casing,
• Guide or Stay vanes,
• Runner blades,
• Draft tube.

Spiral Casing :

 Most of these turbines have vertical shafts although some smaller turbines of this type have horizontal shaft. The fluid enters from the penstock to a spiral casing which completely surrounds the runner. This casing is known as scroll casing or volute. The cross-sectional area of this casing decreases uniformly along the circumference to keep the fluid velocity constant in magnitude along its path towards the guide vane. This is so because the rate of flow along the fluid path in the volute decreases due to continuous entry of the fluid to the runner through the openings of the guide vanes or stay vanes. 

 Guide or Stay vane:

The basic purpose of the guide vanes or stay vanes is to convert a part of pressure energy of the fluid at its entrance to the kinetic energy and then to direct the fluid on to the runner blades at the angle appropriate to the design. The guide vanes impart a tangential velocity and hence an angular momentum to the water before its entry to the runner. The guide vanes are also known as wicket gates.

Runner blades:

The flow in the runner of a Francis turbine is not purely radial but a combination of radial and tangential. The flow is inward, i.e. from the periphery towards the centre. The height of the runner depends upon the specific speed. The height increases with the increase in the specific speed. The main direction of flow change as water passes through the runner and is finally turned into the axial direction while entering the draft tube.

Draft tube:

The draft tube is a conduit which connects the runner exit to the tail race where the water is being finally discharged from the turbine. The primary function of the draft tube is to reduce the velocity of the discharged water to minimize the loss of kinetic energy at the outlet.

Ultrasonic Machining

Ultrasonic machining is an unconventional machining process. Ultrasonic machining is a method of grinding that uses an abrasive liquid rather than direct tool contact.

 
Principle

In ultrasonic machining, a liquid filled with abrasive material flows through over the work piece, and the work tool vibrates against the abrasives. The abrasive materials affect the work piece and remove material. For vibration we use a piezoelectric material, which vibrates on providing an emf.

Construction

The basic mechanical structure of USM is very similar to that of drill machine, howevee it can also be used on brittle materials also. The workpiece is mounted on a vice, which can be located at the desired position under the tool using a 2-axis table. The table can further be lowered or raised to accommodate work of different thickness.

 The basic elements of a USM are:

• Slurry delivery and return system,
• Feed mechanism to provide a downward feed force on the tool during machining,
• The piezoelectric material, which generates the ultrasonic vibration,
• The horn or concentrator, which mechanically amplifies the vibration to the required amplitude of 15-50 microns and accommodate the tool at its tip.

Working

In an ultrasonic machining, a tool of desired shape is vibrates at an ultrasonic frequency of 19-25 kHz with an amplitude of around 15-50 microns over the workpiece. Generally the tool is pressed downward with a feed force, F. Between the tool and the workpiece, the machining zone is flooded with hard abrasive particles generally in the form of water based slurry. As the tool vibrates over the workpiece, the abrasive particles acts as indenters and indent both the workpiece and the tool.

Pelton Turbine

Pelton wheel turbine is a high efficiency water turbine.  Water turbines are used to make electricity and serve as industrial power sources. The Pelton wheel works by extracting energy from the forward momentum of the water. It is an impulse turbine. It was invented by Lester Allan Pelton in 1870.

A Pelton wheel consists of two basic parts, the turbine and the penstock. The turbine is shaped like a wheel. The rim of the wheel is covered with buckets shaped like spoons. As water hits these spoons, it changes direction. Most of the energy in the water is transferred to the wheel, which causes it to turn. The wheel is attached to a shaft and the shaft is connected to a generator, which converts the rotational energy into electricaenergy.

The penstock is the apparatus that brings water to the wheel. The penstock has a nozzle with an opening smaller than the width of the pipe. Nozzle contains a spear which helps to increase the velocity of water and also regulate the amount of water striking the buckets, the spear is controlled by handle in either outward or inward direction. As water is forced through this smaller opening, the water pressure decreases, but the speed at which the water moves is increased.

For the Pelton wheel to reach maximum efficiency, the water must be moving twice as fast as the buckets. 

Steam Turbine

A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. 

Steam turbines utilize the principle of allowing pressurized steam to expand in controlled stages. Each turbine can be composed of a number of impulse and reaction turbines, each of which allows the steam to expand and turn the blades, or buckets, within the device. Most steam turbines employ both of these variations in concern, with the impulse turbines operating under high pressure, and low pressure being utilized for the reaction turbines. The difference between the two is that the impulse turbine uses a nozzle to introduce high velocity steam into the rotors, while the rotors in reaction turbines are themselves a type of nozzle.

The arrangement of impulse and reaction turbines within a steam turbine can effectively make the system very efficient. By making use of both high and low pressure, and having the steam do work at each stage of its expansion, the process may remain highly isentropic. This simply means that the entropy that goes into the system is similar to that which comes out. The other benefit of the design is that the spinning of the turbines creates rotary motion, which can be ideal for both power generation and turning paddles or other drive mechanisms on ships.

The modern steam turbine was invented in 1884 by Sir Charles Parsons, whose first model was connected to a dynamo that generated 7.5 kW or 10 hp of electricity. 

 

parson's turbine

A number of other variations of turbines have been developed that work effectively with steam. The de Laval turbine invented by Gustaf de Laval accelerated the steam to full speed before running it against a turbine blade. De Laval's impulse turbine is simpler, less expensive and does not need to be pressure-proof. It can operate with any pressure of steam, but is considerably less efficient.

 

de laval turbine

Gas Turbine

A turbine is a machine used to deliver power and so gas turbine uses gas as its intake for power delievery.

A gas turbine is a rotary combustion engine that converts the potential energy in gas, plus the kinetic energy of moving air, into a massive amount of energy that turns an output shaft, performing actual work.

Fresh atmospheric air flows through a compressor that brings it to higher pressure. Energy is then added by spraying fuel into the air and igniting it so the combustion generates a high-temperature flow. This high-temperature high-pressure gas enters a turbine, where it expands down to the exhaust pressure, producing a shaft work output in the process. The turbine shaft work is used to drive the compressor and other devices such as an electric generator that may be coupled to the shaft. The energy that is not used for shaft work comes out in the exhaust gases, so these have either a high temperature or a high velocity. The purpose of the gas turbine determines the design so that the most desirable energy form is maximized.

 Gas turbines are used to power aircraft, trains, ships, electrical generators, or even tanks.There are many types of turbine engines, For example, a windmill is a classic, very simple turbine, and steam engines are turbine engines as well.