How Roots Supercharger Works - Easily Explained?

Roots supercharger is the oldest among the other superchargers, roots name comes after the roots type blower the American inventors and brothers Philander and Francis Marion Roots, founders of the Roots Blower Company of Connersville, Indiana USA, who actually patented the basic design and idea for this. All the superchargers mean to produce more power in internal combustion engine. Engine works by drawing a mixture of air and fuel into its cylinders, compressing that mixture, and then burning it. If is used for pressurizes the air at intake or increase the air density which supplied to internal combustion, more air means more oxygen allowing it to burn more fuel and to get more power by increase in air during the combustion in an engine. The more air that can be used to create the large amount of explosion to produce the more power and torque the engine produces. For that Roots supercharger is a one of its kind of the supercharger like other centrifugal and twin-screw supercharger.

Main Parts 

Main Parts of Roots Supercharger


The roots supercharger is constructed almost entirely of cast iron, with the exceptions of shafts, bearings and gears. A rotor is a combination of lobes and shafts. There are two different designs available for this type of supercharger, one is straight and another is twisted lobes. The lobes are supported on anti-friction bearings by the end plates or head plates which are fixed at front and back side of the device and surround the lobes.

Also Read: How Turbocharger Works - Explained?

Let’s see each part in detail:

1. Drive pulley:

From the drive pulley this device gets the rotational power from engine belt. As pulley rotate two rotors and lobes can try to move in different direction as per mechanism. It can initiate further process for the root supercharger.

2. Lobes:

The most important part of the root supercharger is the lobe also known as impeller. Lobes normally are cast grey iron with cast ductile iron for greater strength. It required corrosion or erosion resistance because of continuous air flow from outside can make humidity and temperature differ as per environment.

3. Bearings:

Which support the lobes and anti-friction type; it may be ball or roller. After a long use of device bearing may be wear out and causes noise problem

4. Gears:

It has the helical types of gears. And it must be of high quality with good tolerance to maintain clearance between two lobes of the rotor. A small inaccuracy in gear profile makes contact in rotating lobes and also causes the noise.

5. Shafts:

Both shafts are support the lobes. It has restricted design and diameter in order to support rotor and lobe. Shaft is usually made up of ductile iron. It has the unique characteristic that can be replaceable without changing the other components when damage cause.

6. Casing:

The casing is outer body of root supercharger, it looks like the box, In that all parts lobes, rotors, inlet and discharge ports are fixed and casing made up of cast grey iron. Another consideration is noise level, if thicker the casing the lower the noise.

Working Principle of Roots Supercharger

It can be powered mechanically by engine belt. The roots supercharger is a positive displacement supercharger, works on a very simple principle. As the drive shaft is rotated by engine belt, the lobes turn in opposite directions with very tiny clearances between each other and between the rotors and the casing. As each lobe passes air at the inlet fill side, a measured quantity of air is trapped between the lobes and the casing. As the shafts continue to rotate, this amount of air is transported around the casing to the discharge port side and created high pressure air directly send to inlet manifold through inter cooler and then cylinder of an engine. With this more quantity of air is used to burn more fuel and produce more power and torque in result.

Roots supercharger


Lets discuss its working step by step.
  1. The air from the air filter enters into the casing of the supercharger. The left lobe rotates anti-clockwise and right lobe rotates clockwise. 
  2. As the lobes rotates it traps the air in the space between the lobes and casing and compresses it.
  3. The compressed air is then discharged to the inlet manifold of the internal combustion engine through intercooler. the intercooler reduces the temperature of the air and brings it to the desired value suitable for combustion.
  4. Both the lobes works in the same manner but the direction their rotation is different.

For Better Explanation Watch the Video Given Below:




Advantages:

  • It creates the instant boost at low engine rpm.
  • Simple in construction and easier installation.
  • Do not use engine oil.

Disadvantages:

  • Create lot of heat.
  • Bulky in size.
  • Only delivers fixed amount of air per revolution.

Application:

  1. It is widely used in automobiles, especially in muscle and drag racing cars and hot rods 
  2. Used in Truck, tractors and pickup trucks.
In this article we have learnt about how roots supercharger works, it main parts, working principle, advantages and disadvantages with application. If you find anything missing or modification, please give your valuable comment. And if you get some information from this article than don't forget to like and share it.


What is Capillarity or Capillary Action?

The rise and fall of a liquid surface in a small thin tube, when it is immersed vertically in a liquid is called capillarity (capillary action). The rise of the liquid surface in the tube is called as capillary rise and the fall of the liquid surface is called as capillary depression. The capillary rise and fall of the liquid is expressed in terms of cm or mm of liquid.

The value of capillary rise and fall depends upon

Examples Based on What is Capillarity or Capillary Action 

  1. In plants the rise of water from the roots to all its parts takes place because of capillary action.
  2. The capillary action draws ink to the tips of a fountain pen from cartridge (reservoir) inside the pen.
  3. The towels that we use after taking bath, absorb water from our body because of capillary action.
  4. Sponge which has larger number of small pores acts as small capillaries and absorbs a large amount of water.
  5. The cotton clothes that we wear in hot summer day shows capillary action and absorbs all our body sweat and maintains the temperature of the body to normal.

Expression for Capillary Rise

Expression for Capillary Rise

In order to find expression for the capillary rise, let us take a small tube having diameter ‘d’ opened at both ends. It is inserted in a liquid say water. Gradually the rise of the liquid takes above the level of the liquid.

Let h is the height of the liquid that rises in the tube. Under equilibrium condition, the weight of the liquid of height h is balanced by the forces at the surface of the liquid. But the force that acts at the surface of the liquid is due to surface tension of the liquid.

Let

σ = Surface tension of the liquid.
θ = Angle of contact between liquid and glass tube.

The weight of liquid of height h in the tube
ml = mass of liquid in tube = ρv

v = volume of liquid in tube

From the figure above,

The vertical component of the surface tensile force

= (σ x circumference)cosθ
= σ π d cosθ

Under equilibrium condition, the weight of the liquid in the tube is balanced by the vertical component of the surface tensile force. i.e.

The weight of liquid in the tube = vertical component of the surface tensile force

capillary rise formula
The value of θ in between clean glass tube and water is nearly equal to zero.

Expression for capillary fall

Expression for capillary fall
When the glass tube is dipped in mercury than instead of rising, the level of mercury in the tube goes down than the normal level of the outside liquid. Let the ‘h’ is the height of depression of liquid in the tube.

Under equilibrium condition two forces are acting on the mercury inside the tube. The first force is due to surface tension acting in the downward direction and second force is because of hydrostatic force acting in upward direction.

The force due to surface tension acting downward direction is given by

= σ π d cosθ

And the force due to hydrostatic force acting downward is given by

Under equilibrium condition the two forces i.e. the force due to surface tension is equal to the hydrostatic force.

force due to surface tension = hydrostatic force
capillary depression formula
The value of θ for the mercury and glass tube is 128 degree.

In this article we have learnt about what is capillarity and capillary action, we have also discussed about the examples showing capillarity and derived the expression for the rise and fall of liquid in a tube.

If you find anything missing or incorrect than comment us. And it this article has given you some valuable information then don't forget to like and share it on social networks.

Types of Supercharger in Automobile

What is Supercharger? 

It is used for pressurizes the air at intake or increase the air density which supplied to internal combustion, more air means more oxygen allowing it to burn more fuel and to get more power by increase in air during the combustion of an engine.

All the supercharger can be powered mechanically by means of belt, shaft or chain connected to engine’s crankshaft. Operate in similar way to turbocharger, but are in fact less efficient, where a turbocharger get energy from exhaust gases to power its air compressor, a super charger runs on engine belt. This device adds an average of 40 percent more horsepower, 30 percent more torque and 50 percent more air into the engine.

Also Read: Difference Between Turbocharger and Supercharger

Types of Supercharger

There are three types of supercharger used in automobiles Roots Style, twin screw and centrifugal supercharger. Root style is oldest among them. Centrifugal type uses an impeller whereas other two types are uses different meshing lobes with rotors and they look like same, there is no much physical difference between them in design and construction. Air intake to manifold is different for each of them.

Roots Type Supercharger:


As the rotating meshing lobes spin in different direction right side lobe in clock wise and left one in anti-clock wise. Air comes from outside through the inlet fill side, the two rotors can trap the air by these lobes and actually pushes the air down towards the discharge outlet. Each time it compresses the fixed amount of air at outlet during each rotation. Air gets compressed below the rotary lobes while inlet only sucks the air. Eventually pushing it more pressurized air at the inlet manifold.

Pros:

  • Excellent reliability.
  • Low rpm big boost; at low engine speed it can produce greater boost.
  • Simple in design.

Cons:

  • Creates lots of heat.
  • Heavy in weight and due to bigger in size it can comes out of the hood.
  • Least efficient.

Twin-Screw Supercharger:



In these types of supercharger, two spiral rotors have screw shape and worm gear which pushes air towards to inlet manifold. Rotation of rotors are different from the roots type supercharger , the direction of right side of rotor is take anti-clockwise and left side rotor in clockwise direction. Air get start suction at fill side and convert it to pressurized air due to rotation of both the screw types rotor lobes. Air compresses in rotor housing because of conical taper and air moves from fill side to discharge side.

Pros:

  • It provides Instant boost.

Cons:

  • Noisy, it means it more noise during its working.

Centrifugal Supercharger:



Its look like a turbocharger; when air sucks through impeller having high speed and low pressure thrown towards to diffuser can converts into low speed and high pressure. Impeller and diffuser blades are different in construction. From diffuser air moves towards to volute casing and air pressure further increased. This high pressure air goes to outlet and then inlet manifold of the engine.

Pros:

  • High thermal efficiency and creates less heat.
  • Small and compact in size.

Cons:

  • Bad low rpm boost; there is no fixed amount per revolution.

After Supercharging Process:

As the air is compressed at the end of supercharger, air gets hotter, this means that it loses its density so air molecules are less and cannot expand as much during the explosion in combustion chamber. For a supercharger to work at efficiency, the compressed air needs to cool down for more air molecules. At the discharge unit compressed air must be cooled before it enters the intake manifold. The intercooler is responsible for this cooling process. Due to intercooler reduction in air temperature, the density of the air increases, which makes more oxygen entering the combustion chamber.

In this article we have learnt about types of supercharger used in automobile for boost of engine. if you find anything missing or incorrect then comment us. If you enjoyed the article than don't forget to like and share on Facebook and Google+.

How Turbocharger Works - Explained?

Air intake for engine there are two procedures, one is natural aspiration and another is forced aspiration. Naturally aspirated engines take the air from outside environment through intake manifold from air filter. This kind of engines were used in earlier days but now a days mostly every engine is equipped with mechanical device for forcibly air intake which is helps the engine at inlet valve to compress the air from air filter. This is collectively called turbocharger.

Turbocharger is powered by exhaust gases from engine, its means turbocharger get the power from exhaust gases whereas all superchargers get the power from pulley or engine belt. It is used for regaining energy from waste gases at exhaust. It increase the power output for compressing more air into cylinder.

Main Parts

It consist two housings;
  1. Exhaust housing and 
  2. Compressor housing
Exhaust Housing has the turbine wheel, when Exhaust gases directly strikes at turbine get start rotating by heat energy converted into kinetic energy. Turbine wheel connect with compressor of same shaft so compressor also start rotating automatically. Exhaust housing made up of special material (NI RESIST) to resist high temperature of exhaust gases (temperature around 900°-1000°Celsius).

Compressor Housing has the compressor wheel, this will get rotation from turbine wheel and compressor sucks the air from outside environment. It means less pressurized air converted into high pressurized air due to compressor. Compressor wheel made up of INCONEL.

Middle Portion of Turbocharger:

Between Turbine and Compressor Housing, Shaft is the only way of connecting both wheels. This shaft made up of pure steel. Shaft only takes rotation with either bush or bearing. In turbocharger bearing construction is complex compared to bush, so bushes are having the oil seals at both ends on shaft. Bushes and shaft both are made up of metal so friction is more, to reduce the friction between them move oils (Turbo oil) are added in the device. To stop the oil leak of move oil (Turbo oil) oil seals are fixed at in front of bushes.

Also Read: Difference Between Turbocharger and Supercharger

How Turbocharger Works?

How Turbocharger Works - Explained?

  • Turbocharger can start its process at high RPM around 1000-1200 rpm. And this is why because engine produces more exhaust smoke at high rpm; so that it can able to rotate turbine wheel while with low rpm it doesn’t have that much of rotational force which is required to turn the turbine wheel. 
  • Turbocharger is suitable for multi cylinder engines because single cylinder engine cannot produce that much of exhaust gas as the Multi cylinder engines.
  • Compressor wheel get its rotation from turbine wheel, thus compressor wheel get starts sucking air from air filter through outside. The main work of compressor wheel is to send pressurized air into the intercooler. We may actually send air from compressor to directly at intake manifold after the compressor wheel. But air after the air filter has temperature around 45° Celsius which depends upon the outside atmosphere and due to compressor, this air temperature increased up to 200° Celsius.
  • We know that the air density of high temperature is less as compare to cold air. That’s why to cool down the air; intercooler plays the major role for turbocharger. Air density of less temperature air is high that’s means more air molecules means more oxygen to burn fuel for high explosion in combustion chamber. So, intercooler decreases air temperature for more air molecules.
For better explanation about how turbocharger works watch the video given below:

Turbocharger Limit

It has the maximum rpm 2.5 Lakh-3 Lakh/minute, by crossing its limit an imbalance is created at shaft that breaks the oil seals and it can cause engine damage. To prevent this issue turbocharger is equipped with valve between two housing. At a particular high pressure, means pressure produced after 3 lakh rpm/min valve can automatically open up and it can divert the extra exhaust gas towards the silencer rather than the turbine wheel so that it can stop the crossing the limit of 3 lakh rpm/minute automatically.

Also Read: How Anti-lock Braking System (ABS) Works - Explained

Turbocharger is actually forcing the air in to cylinder, so by forcing additional air which is called boost. More air means more oxygen and can burn more fuel which can create greater explosion compare to normal combustion in cylinder. Piston moves very rapidly as compared to normal piston movement in normal engine. Without turbocharger it does not create this fast reciprocating motion in engine. At high reciprocating motion, piston force is high that can provide crankshaft greater turn. In transmission system engine crankshaft converts reciprocating motion of the piston into rotary motion then this motion drives the flywheel and drive shaft respectively. If this entire process runs at higher rotation, so it can produce more speed at vehicle differential. Effectively by increasing the explosion inside cylinder gives greater rotational force at wheels.

Advantages:

  • Decrease in Emission.
  • Increase in Horsepower.
  • Does not require external power source to run turbocharger

Disadvantages:

  • Turbo lag is the time between the demand for an increase in power and turbocharger providing increased intake pressure, and hence increased power. Turbo lag occurs because turbochargers rely on the buildup of exhaust gas pressure to drive the turbine. In simple words turbocharger is turned on after a particular amount of exhaust gas is produced which happens at a certain rpm. So when this threshold rpm is crossed the turbo does not instantly delivery requisite power surge or boost, and during this period the vehicle does not move very fast when the throttle is given or accelerated. This is due to the time needed for the exhaust system and turbocharger to generate the required boost. Load on the compressor, friction and inertia are main contributor for turbo lag.
  • Space requirement is more.
In this article we have learnt about how turbocharger works in a internal combustion engine. If you find anything missing or incorrect than comment us. If you found this article informative than like and share it on Facebook and Google+.

Anti-lock Braking System (ABS) - Working Principle, Main Components with Advantages and Disadvantages

Anti-lock Braking System also known as anti-skid braking system (ABS) is an automobile safety system which prevents the locking of wheels during braking and avoid uncontrolled skidding. The modern abs system allows steering during braking which gives more control over the vehicle in case of sudden braking.

the main advantages of using ABS system in vehicle is that it provides better control over the vehicle and decreases stopping distance on dry and slippery surfaces. Since in ABS installed vehicle the chance of skidding is very less and hence it provides a better steering control during braking. Without ABS system, even a professional driver can fail to prevent the skidding of the vehicle on dry and slippery surfaces during sudden braking. But with ABS system, a normal person can easily prevent the skidding of the vehicle and get better steering control during braking.


Principle of Working

It works on the principle of threshold braking and cadence braking. Cadence braking and threshold braking is a technique in which a driver applies the brakes and releases it before locking up the wheel and then applies the brakes and releases it again before locking. This process of applying and releasing the brakes on the wheel is done in pulse form to prevent it from locking and stop skidding of the vehicle. The driver practices this technique to achieve better control over the vehicle during instant braking and stop skidding of the vehicle. The ABS system automatically does this cadence braking to prevent locking of wheel and skidding of vehicle when brakes are applied.

Also Read: Centrifugal Clutch - Working Principle, Main Parts Advantages and Disadvantages

Why Anti-lock Braking System (ABS) is essential in vehicles?

To understand this in a better way lets us take an incident. When you are driving your car on a highway and suddenly an obstacle comes in front of you and you apply brake with full power. This will locks wheels of your car and your car will start skidding on the road and also during skidding you lost your steering control and unable to move the car in desired direction in which you want. Finally you hit that obstacle and meet an accident.


Let’s us take another situation, now you are driving a car which is equipped with anti-lock braking system. When you encounter with an obstacle on the road and suddenly apply the brakes. But this time the ABS system of your car prevent the locking of the wheel and avoid skidding. At this time you can control your steering and can stops your car hitting from the obstacle. This is how the abs system prevents the skidding of the vehicle and provides greater control over it and prevents accidents.

Main Components of ABS System

It has four main components
1. speed sensors
2. Valves
3. Pump
4. Controller

1. Speed Sensors

It is used to calculate the acceleration and deceleration of the wheel. It consists of a toothed wheel and an electromagnetic coil or a magnet and a Hall Effect sensor to generate signal. When the wheel or differentials of the vehicle rotates, it induces magnetic field around the sensor. The fluctuation in this magnetic field generates voltage in the sensor. This voltage generated sends signals to the controller. With the help of the voltage the controller reads the acceleration and deceleration of the wheel.

2. Valves

Each brake line which is controlled by the ABS has a valve. In some of the systems, the valve works on three positions.
  1. In position one, the valve remains open; and pressure from the master cylinder passed through it to the brake.
  2. In position two, the valve blocks the line and separates the brake from the master cylinder. And this prevents the further rise of the pressure to the brakes. Valve operates in second position when the driver applies the brake harder.
  3. In position three, some of the pressure from the brake is released by the valve.
The clogging of the valve is the major problem in ABS. When the valve is clogged, it becomes difficult for the valve to open, close or change position. When the valve is in inoperable condition, it prevents the system form modulating the valves and controlling pressure to the brakes.

3. Pump

Pump is used to restore the pressure to the hydraulic brakes after the valve releases the pressure. When the controller detects wheel slip, it sends signals to release the valve. After the valve releases the pressure supplied from the driver, it restore a desired amount of pressure to the braking system. The controller modulates (adjust) the status of the pump so as to provide desired amount of pressure and reduce slipping of the wheel.

4. Controller

The controller used in the ABS system is of ECU type. Its main function is to receives information from each individual wheel speed sensors and if a wheel losses it traction with the ground, a signal is sent to the controller, the controller than limit the brake force (EBD) and activate the ABS modulator. The activated ABS modulator actuates the braking valves on and off and varies the pressure to the brakes.

Also Read: Torque Converter Working, Principle, Main Parts and Application.

Working of Anti-lock Braking System (ABS)

  • The controller (ECU-Electronic Control Unit) reads the signal from each of the speed sensors of the wheel.
  • As the brakes are suddenly applied by the driver, this makes the wheel to decelerate at faster rate and may cause the wheel to Lock.
  • As the ECU reads the signal which indicates the rapid decrease in the speed of the wheel, it sends signal to the valve which makes the valve close and the pressure to the brake pad reduces and prevents the wheel from locking.
  • The wheel again starts to accelerate, again the signal sends to the controller, this time it opens the valve, increasing the pressure to the brake pad and brakes are applied, this again reduces the speed of the wheel and tries to make it stop.
  • This process of applying brakes and releasing it happens 15 times in a second when a driver suddenly applies the brake harder. Due to this the locking of the wheel is prevented and the skidding of the vehicle eliminated. During braking with ABS system, the driver can steer the vehicle and reduces the risk of vehicle collision.

For Better Explanation about Anti-lock Braking System Watch the Video Given Below:


How Would you Know that the ABS System is in Operation?

When the ABS in operation, it can be felt by the driver through pulsation in the brake pedal; this happens because of the rapid opening and closing of the valves. The pulsing action of the pedal tells the driver that ABS system is in operation. Any fault in the ABS system is indicated on the instrument panel of the vehicle and it will work when the fault is completely removed.

Advantages

It prevents the locking of the wheel and thus eliminates the chance of skidding.
The skidding of the vehicle is completely removed, which results in excellent control during braking?
A better steering control is obtained with the ABS system.
It reduces the chance of collision by 30 %.

Disadvantages

A vehicle equipped with ABS (Anti-lock Braking System) is costlier as compared with a vehicle without ABS.

Image sources:
https://www.britannica.com/technology/automobile

What is Surface Tension?

Surface Tension (ST) is defined as the tensile force acting on the free surface of liquid which is in contact with a gas or on the surface in between two immiscible liquids such that the contact surface behaves like a thin membrane under tension. It is more interesting to know how this tensile force acts on the free surface of the liquid. 

What is Surface Tension?


To understand that lets us take three molecules of liquid as A, B and C. Molecule A is completely lie inside the free surface of liquid, it experiences equal tensile force in all direction from its neighboring molecules. So the net resultant force on the molecule A is zero.

The molecule B is situated near the free surface of the liquid. It is experiencing upward and downward forces. But the magnitude of the downward force is greater than the upward force; hence it experiences a net downward force.

The molecule C which is situated on the free surface of the liquid experiences a net downward force. So all the molecules of liquid which is situated on the free surface of the liquid experiences a net downward force. Due to this, the free surface of the liquid acts likes a thin film under tension.

Cause

Surface tension occurs due to cohesive forces existing in between the molecules of liquid. It is the cohesive forces that allows one molecule of liquid to attract its neighbouring molecules. Due to this cohesive forces the molecules of liquid on the free surface experiences a tensile force. 

Formula 

When the tensile force acting on the free surface of the liquid is calculated on unit length than the quantity we get is called surface tension. It is also equal to the surface energy per unit area.
  • It is denoted by the Greek letter σ (sigma)
  • Its SI unit is N/m.

Mathematically,
surface tension formula
Where

σ = Surface tension
F = Tensile force
l = length on which tensile force acts

  • The ST of water in contact with air at 20 degree celsius is 0.0725 N/m. and 
  • The ST of mercury in contact with air at 20 degree celsius is 0.52 N/m.

Examples

  1. Drops of water: it is observed that the drops of water have spherical shape and this happens due to the ST of the water.
  2. Insects walking on water: We have seen so many times that small insects are capable of walking on the surface of water. This is possible because of the ST of the water, it provides a thin film for the insects on which they can balance their body and prevent them from sinking.
  3. Needle or paper clip floating on water: A needle or paperclip is a metallic part which has more density than water. But even after than they can float on the free surface of the water and this is due to the surface tension.


                                                                                                                                                             

What is Engineering Mechanics?

Engineering mechanics is the branch of applied science which works with the laws and principle of mechanics. Whatever the body we seen around us experiences forces and due the forces experienced by the body they undergo motion. The study of object which is either in motion or at rest because of the forces acting on them is done under mechanics branch.

What is engineering mechanics?

Why  Study of Engineering Mechanics is Essentials?

Nowadays engineers are inventing a lot of machines and structures. To make a proper planning, design of these machines and structures the knowledge of mechanics is very essential. In order to perform his/her job more efficiently and more precisely the study of this branch is necessary for mechanical engineers. It is the mechanics which is recommended for every branch of engineering to study. Without mechanics the design of anything is not possible. The mechanics is present everywhere where forces exist.

The engineering mechanics is subdivided into two types
  1. Statics
  2. Dynamics

Statics

This branch of mechanics deals with the forces and their effect on the bodies which are at rest. For example: if a block is resting on a ground and if we are studying the forces and their effect on that block, than we are dealing with statics branch of mechanics.

A civil engineer mostly works with statics as they design bridges, buildings, roads etc which cannot move. In civil engineering if something moves, it means it gets failed.

Dynamics

It is the branch of mechanics that deals with forces and their effects on the bodies which are in motion. A mechanical engineer works more with dynamics. As they design mechanisms, machines and things which contains moving parts. They create moving objects like automobiles, airplane etc.
For Example: Study of motion of a car running on road, study of motion of thrown object above the ground etc.

Dynamics is further divided into two types: 
  1. Kinetic
  2. Kinematics

Kinetics

It works with the bodies in motion because of the applied forces. In other words it is the branch which deals with the bodies in motion considering the cause of motion (i.e forces).

Kinematics

This branch deals with the bodies in motion without considering the forces causing the motion. It is used to describe the motion of points, bodies and system of objects without taking the mass of each or the forces which caused that motion. It is used in astrophysics to describe the motion of celestial bodies. In mechanical engineering it used in robotics and biomechanics. It describes the motion of systems which is composed of joined parts such as engine, a robotic arm or the human skeleton.

This is all about the engineering mechanics if you find anything missing than comment us to improve the article.


What is Cavitation and How it Occurs?

Cavitation is a phenomenon of formation of vapor bubbles of a flowing liquid in a region where the pressure of the liquid becomes equal or less than the vapor pressure. When these vapor bubbles reaches into the region of higher pressure, they collapse and creates high impact pressure. These high impact pressure created by the vapor bubbles eroded the materials from metallic surface and produces cavity.

What is Cavitation and How it Occurs?

For better explanation of the above cavitation phenomenon one must have knowledge of vaporization and vapor pressure.

What is Vaporization?

The change of liquid phase into gaseous phase is called vaporization. The vaporization depends upon the prevailing temperature and pressure condition. It occurs due to the continuous escaping of the liquid molecules from free surface of the liquid.

What is Vapor Pressure?

In order to understand vapor pressure, let’s take a closed vessel in which a liquid (say water) is present. Let the temperature of the water is 20 oC and pressure is atmospheric. In this situation the vaporization of water takes place at 100 oC. As the vaporization of water starts, the molecules of liquid (vapor) start escaping out from the free surface of the liquid. The vapor molecules escaping out from the liquid free surface gets collected between the free surface of the liquid and top of the vessel. These vapor molecules exerts pressure on the free surface of liquid. This pressure exerted by the vapor is called vapor pressure. Vapor pressure is also defined as the pressure at which the liquid changes into vapor

Now, again take a closed vessel filled with a liquid (say water). Let the temperature of the water is 20 oC and the pressure in the vessel is reduced by some external source. When the pressure is reduced, the vaporization temperature is also reduced. Let the pressure inside the vessel is reduced to such an extent that it becomes equal or less than the vapor pressure. In this situation the boiling of water takes place even though the temperature of liquid is 20 oC. Thus the boiling of water takes place even at ordinary temperature; if the pressure is reduced as such it becomes equal to or less than the vapor pressure.

Explanation of Cavitation

Considered a system in which a liquid (say water) is flowing. When the flowing water enters into a region where the pressure becomes equal to or less than that of the vapor pressure. Than the vaporization of water starts and vapor bubbles are formed in the water. When these vapor bubbles are carried by the flowing liquid in the region of higher pressure they explode. The explosion of vapor bubbles creates impact pressure of high intensity. Since the liquid flows over the metallic surface, the high pressure produced by explosion of vapor bubbles erodes the material from the metallic surface and creates cavity. This phenomenon is called cavitation. The bursting of the vapor bubbles creates noise and vibration.

For better explanation watch the video given below:


Cause

Cavitation occurs when pressure of flowing liquid in any region becomes equal to or less than the vapor pressure.

Effect

  • It results in damage to the metallic surfaces and creates cavity.
  • Creates noise and vibration due to sudden collapsing of vapor bubbles.
  • It reduces the efficiency of hydraulic machines like turbine and pumps.

Precaution

  • The pressure of the liquid in any part of the hydraulic system should not be reduced below its vapor pressure.
  • The special materials or coating such as stainless steel and aluminium bronze, which are cavitation resistance should be used.
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Centrifugal Pump - Working Principle, Main Parts with Application

Centrifugal pump is a hydraulic machine which converts mechanical energy into hydraulic energy (i.e. pressure energy) by the use of centrifugal force acting on the fluid. The flow of liquid takes place in radial outward direction which is reverse of the inward radial flow reaction turbine. It is used in different areas where fluid is needed to raised from low level to high level.

Working Principle

It works on the principle of forced vortex flow. The forced vortex flow means when a certain mass of fluid or liquid is allowed to rotate by an external torque than there is a rise in pressure head of the rotating liquid takes place. This rise in pressure head is used to deliver water from one location to another. It is centrifugal force acting on the fluid that makes it to flow within the casing.

The rise in the pressure head of the rotating liquid at any point is directly proportional to the square of the tangential velocity of the rotating liquid.

Mathematically

How liquid is lifted to high level?

At the outlet of the impeller, radius is more and because of this the rise in the pressure head is more and the liquid at the outlet discharged with a high pressure head. And because of this high pressure head, the liquid can be lifted to a very high level.

Also Read: Pelton Turbine Working, Main Parts, Application with Diagram

Main Parts

The various main parts of a centrifugal pump are:

Centrifugal Pump Working Principle, Main Parts with Application

  1. Impeller
  2. Casing
  3. Suction pipe with a foot valve and strainer
  4. Delivery pipe

Let’s discuss about each one of them one by one

1. Impeller

It is the rotating part of the pump. The impeller is mounted on a shaft and the shaft of impeller is again connected with the shaft of an electric motor. It is rotated by the motor and consists of series of backward curved blades.

2. Casing

It is an air tight passage which surrounds the impeller. The design of the casing is done in such a way that it is capable of converting the kinetic energy of the water discharging from the outlet of the impeller into pressure energy before it leaves the casing and enters into the delivery pipe.

Commonly three types of casing are used in centrifugal pump and these are

(i). Volute Casing: It is a spiral type of casing in which the area of flow increases gradually. The increase in area of flow decreases the velocity and increases the pressure of the liquid that flows through the casing. The volute casing is shown in figure above:

(ii). Vortex Casing: In vortex casing, a circular chamber is introduced in between the impeller and casing. This is done in order to prevent the loss of energy due to formation of eddies. The efficiency of the vortex casing is more than that of the volute casing.

(iii). Casing with Guide Blades: In this casing, the impeller is surrounded by series of guide blades. The guide blades are mounted on a ring which is called as diffuser. The design of the guide vanes are kept as such that the water which is leaving the impeller enters the guides without shock. The area of the guide vanes increases; this helps to decrease the velocity of the liquid and increases its pressure. After guide vanes, water passes through the surrounding casing. In most of the cases, the casing remains concentric with the impeller.

Also Read: Types of Turbine

3. Suction Pipe with Foot Valve and Strainer

A pipe whose one end is connected with the inlet of the impeller and the other end is dipped into the sump of water is called suction pipe. The suction pipe consists of a foot valve and strainer at its lower end. The foot valve is a one way valve that opens in the upward direction. The strainer is used to filter the unwanted particle present in the water to prevent the centrifugal pump from blockage.

Delivery Pipe

It is a pipe whose one end is connected to the outlet of the pump and other end is connected to the required height where water is to be delivered.

Working

  • As the electric motor starts rotating, it also rotates the impeller. The rotation of the impeller creates suction at the suction pipe. Due to suction created the water from the sump starts coming to the casing through the eye of the impeller.
  • From the eye of the impeller, due to the centrifugal force acting on the water, the water starts moving radially outward and towards the outer of casing.
  • Since the impeller is rotating at high velocity it also rotates the water around it in the casing. The area of the casing increasing gradually in the direction of rotation, so the velocity of the water keeps on decreasing and the pressure increases, at the outlet of the pump, the pressure is maximum. 
  • Now form the outlet of the pump, the water goes to its desired location through delivery pipe.
For better explanation watch the video given below:



What is priming and why it is necessary?

It is process in which the suction pipe, casing and delivery pipe upto the delivery valve is filled completely with liquid to be raised from outside source before starting the motor. Priming is done to remove the air from the pump.

If air is not removed from the pump than a small negative pressure is created at the suction pipe and it cannot suck the water from the water sump. So it is advised to fill the pump with water before starting it.

Application

The centrifugal pump is used in almost every field to raise the liquid from low level to high level. They are mostly used at home for filling water tanks, almost in every industry such as chemical, automobile, marine, manufacturing, for irrigation etc.


Centrifugal Clutch - Working Principle, Main Parts Advantages and Disadvantages

Centrifugal Clutch is type of clutch in which centrifugal force is used to connect engine drive shaft with the shaft of transmission. It is placed in between the engine flywheel and transmission system. Its main function is to connect the engine shaft with the transmission shaft. It works more efficiently at higher speeds.

Main Parts

The main parts of centrifugal clutch are

Centrifugal Clutch Main Parts

  1. Shoes: The shoes are of sliding types which slides in the guide ways. It consists of friction lining at the end and this friction lining makes contact with the drum during engagement.
  2. Spring: Spring is used to disengage the clutch when the engine rotates at lower speed. 
  3. Spider or guides: The spiders are mounted on the driver (engine) shaft or motor shaft. The spiders are equally spaced. Equally spaced means, if they are four guides than each guide is separated from each other by 90 degree. The sliding shoes are kept in between these guides and each guide is holding a spring. 
  4. Friction lining: The outer surface of sliding shoes has friction lining. It helps in making grip with the inner surface of the drum.
  5. Drum: The drum of the clutch act as housing which encloses all the parts of the clutch that includes sliding shoes, guides, springs etc. It is connected to the driven shaft of the transmission system or chains or belt.

Working Principle

Its working is totally depends upon the centrifugal force created by the driving member (engine or motor).  The centrifugal force is used to engage the clutch with driven shaft. As the engine starts rotating, it produces a centrifugal force which makes the sliding shoes to move outward. The friction lining of the shoes gets connected to the inner surface of the drum and it starts moving. Since the drum is connected to the driven shaft, so the power is transmitted from the engine shaft to the transmission shaft and finally to the load.

Working of Centrifugal Clutch

Centrifugal Clutch Working

  1. As the engine rotates, the inside assembly of the centrifugal clutch starts rotating but drum remains stationary and no power is transmitted. At lower speed, the centrifugal force produced is not sufficient to overcome the spring force. So the clutch remains disengaged. But as the speed increases, the centrifugal force also increases and now the centrifugal force becomes greater than the spring force. 
  2. As the centrifugal force becomes greater that the spring force, this allows the sliding shoes to move outward against the spring and get engaged with the inner surface of the drum.
  3. The drum starts rotating and transfer the rotating power from the engine to the driven shaft of the transmission.
  4. When the load on the engine increases, its speed decreases and disengages the clutch. 
For better explanation watch the video given below:



Advantages

  • It is simple and requires less maintenance.
  • It is inexpensive.
  • Since it is automatic, so it does not need necessary control mechanism.
  • Its engagement speed can be controlled by selecting appropriate spring.
It helps to prevent the engine from  stalling.

Disadvantages

  • There is a loss of power in it due to slipping and friction.
  • It is not capable of transferring high amount of power and it shoes slip in heavy load condition.
  • It experiences overheating problem.
  • Its engagement depends upon the speed of the driving shaft.

Application

Centrifugal clutch is mainly used in lawn movers, mopeds, go karts, mini bikes, chainsaws etc. It is also used in some paramotors and boats to keep the engine running during stalling and disengage loads during starting and idling.

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