# ME - Mechanical EngineeringOnline resource for Mechanical Engineers

Gas Laws explain the behavior of an ideal gas in terms of Temperature, Pressure, Volume. The following are some of the important gas laws are
• Boyle’s Law
• Charles Law
• Gay-Lussac’s Law
• Universal Gas Law

## Boyle’s Law:

Boyle’s law states that the volume of a given mass of gas (V) is inversely proportional to its absolute pressure (P), provided the temperature of the gas (T) remains constant.
Boyle’s law formula

## Charles Law:

According to Charles law, the volume of a given mass of gas (V) is directly proportional to its absolute temperature (T), when its pressure remains constant.
Charles law formula

## Gay-Lussac’s Law:

Gay-Lussac's Law is also know as Amontons’ law. It states that if the volume of a given mass of a gas (V) is kept constant, then the pressure of the gas (P) is directly proportional to its absolute temperature (T).
Gay-Lussac's Law Formula

Avogadro's law states that equal volumes of different perfect gases, at the same temperature (T) and pressure (P), contain equal number of molecules (n).

## Universal Gas Law:

Combined Gas law is derived from the three gas laws Boyles law, Charles law and Gay-Lussacs law.
Universal Gas Law Formula
The sliding of a solid body in contact with another solid body is always opposed by  force of friction. Friction acts in the direction opposite to that of relative motion and it is tangential to the surface of two bodies at the point of contact.
Friction is a necessary in every machine because it involves wearing of machine component and consumes energy that transfers into heat. In come cases friction is desirable in case for functioning of a machine, such as belt drives, friction clutches.

## The Five Laws of Friction:

1. When a body is moving, the friction is directly proportional to normal force and frictional force direction is perpendicular to the normal force.
2. Friction doesn't depend on the area of contact so long as there is an area of contact.
3. The coefficient of static friction is slightly higher the value than the coefficient of kinetic friction.
4. Kinetic friction is independent of velocity of the body.
5. Friction depends upon the type of the surfaces in contact.
A manometer is a device used for measure the pressure of a fluid by balancing it with against a column of a liquid. Five different types of manometers are shown with pictures below.

### U-Tube Manometer :

It consist a U – shaped bend whose one end is attached to the gauge point ‘A’ and other end is open to the atmosphere. It can measure both positive and negative (suction) pressures. It contains liquid of specific gravity greater than that of a liquid of which the pressure is to be measured.
where 'γ' is Specific weight, 'P' is Pressure at A.
Pressure at A is P = γ2h2 – γ1h1

### Differential Manometer : A U-Tube manometric liquid heavier than the liquid for which the pressure difference is to be measured and is not immiscible with it.

Pressure difference between A and B is given by equation
PA – PB = γ2h2 – γ3h3 – γ1h1

### Inverted U-Tube Manometer :

Inverted U-Tube manometer consists of an inverted U - Tube containing a light liquid. This is used to measure the differences of low pressures between two points where where better accuracy is required. It generally consists of an air cock at top of manometric fluid type.
Pressure difference can be calculated from equation
P1 - ρ1*g*H1 – ρm*g(H2 – H1) = P2 – ρ2*gH2

### Micro Manometer :

Micro Manometer is is the modified form of a simple manometer whose one limb is made of larger cross sectional area. It measures very small pressure differences with high precision.
Let 'a' = area of the tube,
A = area of the reservoir,
h3 = Falling liquid level reservoir,
h2 = Rise of the liquid in the tube,
By conversation of mass we get A*h3 = a*h2
Equating pressure heads at datum we get
P1 = (ρm ρ1)*gh3 + ρm*gh2 - ρ1*gh1

### Inclined Manometer :

Inclined manometer is used for the measurement of small pressures and is to measure more accurately than the vertical tube type manometer. Due to inclination the distance moved by the fluid in manometer is more.
Pressure difference between A and B is give by equation
Governor is a device used to maintain the speed of an engine within specified limits when the engine works in varying of different loads.
Based on the source of controlling force, the governors can be classified into two types. They are centrifugal governors and inertia governors.

### Centrifugal Governors :

In centrifugal governors, multiple masses know as governor balls, are responsible to revolve about the axis of a shaft, which is driven through suitable gearing from the engine crankshaft. Each ball is acted upon by a force which acts in the radially inward direction and is provided by dead weight, a spring or a combination of two. This force is commonly called as the controlling force and it will increase as the distance of the ball from the axis of rotation increases. The inward or outward movement of the ball is transmitted by the governor mechanism to the valve which controls the amount of energy supplied to the engine.

Image Source : flickr.com

### Inertia Governor :

In inertia governors, the balls are arranged in manner that the inertia forces caused by angular acceleration or retardation of the governor shaft tend to change their position. The obvious advantage of inertia governor lies in its rapid response to the effect of a change of load. This advantage is small, however by the practical difficulty of arranging for the complete balance of the revolving parts of the governor. For this reason Centrifugal governors are preferred over the inertia governors.
In statics, Lami's theorem is an equation that relates the magnitudes of three coplanar, concurrent and non-collinear forces, that keeps a body in static equilibrium.
Lami’s theorem states that if three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two forces.
Consider three forces A, B, C acting on a particle or rigid body making angles α, β and γ with each other.

According to Lami’s theorem , the particle shall be in equilibrium if
The angle between the force vectors is taken when all the three vectors are emerging from the particle.

A belt is a looped strip of flexible material used to mechanically link two or more rotating shafts. A belt drive offers smooth transmission of power between shafts at considerable distance. Belt drives are used as source of motion to transfer to efficiently transmit power or to track relative movement.

Image source : wwag.com

## Types of Belt Drives:

In a two pulley system, depending upon direction the belt drives the pulley, the belt drives are divided into two types. They are open belt drive and crossed belt drive. The two types of belt drives are discussed below in brief.

### Open belt drives :

An open belt drive is used to rotate the driven pulley in the same direction of driving pulley.  In motion of belt drive, power transmission results makes one side of pulley more tightened compared to the other side.  In horizontal drives, tightened side is always kept in the lower side of two pulleys because the sag of the upper side slightly increases the angle of folding of the belt on the two pulleys.

### Crossed belt drives :

A crossed belt drive is used to rotate driven pulley in the opposite direction of driving pulley. Higher the value of wrap enables more power can be transmitted than an open belt drive. However, bending and wear of the belt are important concerns.

### Advantages of belt drives :

• Belt drives are simple are economical.
• They don't require Parallel shafts.
• Belts drives are provided with overload and jam protection.
• Noise and vibration are damped out. Machinery life is increased because load fluctuations are shock-absorbed.
• They are lubrication-free. They require less maintenance cost.
• Belt drives are highly efficient in use (up to 98%, usually 95%).
• They are very economical, when distance between shafts is very large.

### Disadvantages of belt drives :

• In Belt drives, angular velocity ratio is not necessarily constant or equal to the ratio of pulley diameters, because of slipping and stretching.
• Heat buildup occurs. Speed is limited to usually 35 meters per second. Power transmission is limited to 370 kilowatts.
• Operating temperatures are usually restricted to –35 to 85°C.
• Some adjustment of center distance or use of an idler pulley is necessary for wearing and stretching of belt drive compensation.

### Newton’s First Law of Motion :

Newton’s first law of motion states that every object will remain at rest or in uniform  motion in a straight line unless compelled to its state by the action of an external force.
The first law of motion is normally taken as the definition of inertia. If there is no net force acting on an object then object will remain a constant velocity. If an external force is applied, the velocity of body will change because of force.

### Newton’s Second law of Motion :

Newton’s Second law of motion states that if the resultant force acting on a particle is not zero, the particle will have acceleration proportional to the magnitude of the resultant and in the direction of this resultant force.  This law explains how velocity of an object changes when it is subjected to an external force. The law defines force to be equal to change in momentum (mass times velocity) per unit time.
For an object  with constant mass m, Newton’s second law of motion states that the force 'F' is the product of an object’s mass 'm' and its acceleration 'a'.
F = m.a
For an externally applied force, the acceleration depends on mass of the object and a change in velocity will generate a force. The above equation works in both ways.

### Newton’s Third Law of Motion :

Newton’s third law of motion states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object 'A' exerts a force on object 'B', then object 'B' also exerts an equal force on object 'A'.
The third law of motion can be used to explain the generation of lift by a wing and the production of thrust by a jet engine.

Heat exchanger is a process equipment designed for the effective transfer of heat energy between two fluids. For the heat transfer to occur two fluids must be at different temperatures and they must come thermal contact. Heat exchange involve convection in each fluid and conduction through the separating wall. Heat can flow only from hotter to cooler fluids, as per the second law of thermodynamics.

Heat exchangers can be classified into four types, according to

### 1. Nature of heat exchange process:

• Direct contact heat exchanger: this is done by complete physical mixing of heat and mass transfer. Examples are water cooling towers and jet condensers in steam power plants.
• Regenerator: here hot and cold fluids flows alternately when hot fluid passes, the heat is transferred to the solid matrix and then stopped the flow of hot fluid, next cold fluid is passed on the matrix which takes heat from solid matrix. Examples are Open hearth and blast furnaces.
• Recuperator: the cold fluid flows simultaneously on either side of a separating wall. Examples are super heaters, condensers, economizers and air pre-heaters in steam power plants, automobile radiators.

### 2. Relative direction of motion of fluids:

According to flow of fluids, the Heat Exchangers are classified into three categories:

#### 2.1 Parallel flow heat exchangers:

In parallel flow heat exchangers, both the tube side fluid and the shell side fluid flow in same direction. In this case, the two fluids enter the heat exchanger from the same end with a large temperature difference.

#### 2.2 Counter flow heat exchangers:

In counter flow heat exchangers, the two fluids flow in opposite directions. Each of the fluids enter the heat exchanger from opposite ends. Because the cooler fluid exists the counter flow heat exchanger at the end where the hot fluid enters the heat exchanger, the cooler fluid will approach the inlet temperature of the hot fluid.

#### 2.3 Cross flow heat exchangers:

In cross flow heat exchangers, one fluid flows through tubes and second fluid passes around the tubes perpendicularly.

### 3. Mechanical Design of Heat Exchanger Surface:

1. Concentric tubes
2. Shell and tube
3. Multiple shell and tube passes

### 4. Physical state of heat exchanging:

1. Condenser
2. Evaporator

The following are the important dimensions and geometries concerned with toothed gear:

#### Pitch Circle :

Pitch circle is the apparent circle that two gears can be taken like smooth cylinders rolling without friction.

Addendum circle is the outer most profile circle of a gear. Addendum is the radial distance between the pitch circle and the addendum circle.

#### Dedendum Circle :

Dedendum circle is the inner most profile circle. Dedendum is the radial distance between the pitch circle and the dedendum circle.

#### Clearance :

Clearance is the radial distance from top of the tooth to the bottom of the tooth space in the mating gear.

#### Backlash :

Backlash is the tangential space between teeth of mating gears at pitch circles.

#### Full Depth :

Full depth is sum of the addendum and the dedendum.

#### Face Width :

Face width is length of tooth parallel to axes.

#### Diametral Pitch :

Diametral pitch (p) is the number of teeth per unit volume.
p =  (Number of Teeth) / (Diameter of Pitch circle)

#### Module :

Module (m) is the inverse of diametral pitch.

m = 1/p

#### Circular Pitch :

Circular pitch is the space in pitch circle used by each teeth.

#### Gear Ratio :

Gear ratio is numbers of teeth of larger gear to smaller gear.

#### Pressure Line :

Pressure line is the common normal at the point of contact of mating gears along which the driving tooth exerts force on the driven tooth.

#### Pressure Angle :

Pressure angle is the angle between the pressure line and common tangent to pitch circles. It is also called angle of obliquity. high pressure angle requires wider base and stronger teeth.

#### Pitch Angle :

Pitch angle is the angle captured by a tooth.
Pitch angle = 360/T

#### Contact Ratio :

Contact ratio is angle of angle of action and pitch angle.

#### Path of Approach :

Path of approach is the distance along the pressure line traveled by the contact point from the point of engagement to the pitch point.

#### Path of Recess :

Path of recess is the distance traveled along the pressure line by the contact point from the pitch point to the path of disengagement.

#### Path of Contact :

Patch of contact is the sum of path of approach and path of recess.

#### Arc of Approach :

Arc of approach is the distance traveled by a point on either pitch circle of the two wheels from the point of engagement to the pitch.

#### Arc of Recess :

Arc of recess is the distance traveled by a point on either pitch circle of the two wheels from the point to the point of disengagement.

#### Arc of Contact :

Arc of contact is the distance traveled by a point on either pitch circle of the two wheels during the period of contact of a pair of teeth.

#### Angle of Action :

Angle of action is the angle turned by a gear during arc of contact.

Gears can be classified according to relative positions of their shaft axes into three types. They are:
1. Gears for Parallel shafts
2. Gears for Intersecting Shafts
3. Gears for Skew Shafts

 Different types of gears

### 1. Gears for Parallel Shafts:

The motion between parallel shafts is same as to the rolling of two cylinders. Gears under this category are the following:

#### 1.2 Helical Gears:

In helical gear teeth are part of helix instead of straight across the gear parallel to the axis. The mating gears will have same helix angle but in opposite direction for proper mating. As the gear rotates, the contact shifts along the line of contact in in volute helicoid across the teeth.

#### 1.3 Herringbone Gears:

Herringbone gears are also known as Double Helical Gears. Herringbone gears are made of two helical gears with opposite helix angles, which can be up to 45 degrees.

#### 1.4 Rack and Pinion:

In these gears the spur rack can be considered to be spur gear of infinite pitch radius with its axis of rotation placed at infinity parallel to that of pinion. The pinion rotates while the rack translates.

### 2. Gears for Intersecting Shafts:

The motion between two intersecting shafts is equivalent to the rolling of two cones. The gears used for intersecting shafts are called bevel gears. Gears under this category are following:

#### 2.1 Straight Bevel Gears:

Straight bevel gears are provided with straight teeth, radial to the point of intersection of the shaft axes and vary in cross section through the length inside generator of the cone. Straight Bevel Gears can be seen as modified version of straight spur gears in which teeth are made in conical direction instead of parallel to axis.

#### 2.2 Spiral Bevel Gears:

Bevel gears are made with their teeth are inclined at an angle to face of the bevel. Spiral gears are also known as helical bevels.

### 3. Gears for Skew Shafts:

The following gears are used to join two non-parallel and non-intersecting shafts.

#### 3.1 Hypoid Gears:

The Hypoid Gears are made of the frusta of hyperboloids of revolution. Two matching hypoid gears are made by revolving the same line of contact, these gears are not interchangeable.

#### 3.2 Worm Gears:

The Worm Gears are used to connect skewed shafts, but not necessarily at right angles. Teeth on worm gear are cut continuously like the threads on a screw. The gear meshing with the worm gear is known as worm wheel and combination is known as worm and worm wheel.

An automobile is a vehicle that is capable of propelling itself. Since 17th century, several attempts have been made to design and construct a practically operative automobile.
Today, automobiles play crucial role in the social, economic and industrial growth of any country.
After the designing of Internal Combustion Engines, the Automobile industries has seen a tremendous growth.

### Classification of Automobiles :

Automobiles can be classified into several types based on many criteria. A brief classification of automobiles is listed below:

#### 1. Based on Purpose :

• Passenger vehicles : These vehicles carry passengers. e.g: Buses, Cars, passenger trains.
• Goods vehicles : These vehicles carry goods from one place to another place. e.g: Goods lorry, Goods carrier.
• Special Purpose : These vehicles include Ambulance, Fire engines, Army Vehicles.

#### 2. Based on Load Capacity:

• Light duty vehicle : Small motor vehicles. eg: Car, jeep, Scooter, motor cycle
• Heavy duty vehicle :  large and bulky motor vehicles. e.g: Bus, Truck, Tractor

#### 3. Based on fuel used:

• Petrol engine vehicles : Automobiles powered by petrol engine. e.g: scooters, cars, motorcycles.
• Diesel engine vehicles : Automobiles powered by diesel engine. e.g: Trucks, Buses, Tractors.
• Gas vehicles : Vehicles that use gas turbine as power source. e.g: Turbine powered cars.
• Electric vehicles : Automobiles that use electricity as a power source. e.g: Electric cars, electric buses.
• Steam Engine vehicles : Automobiles powered by steam engine. e.g: Steamboat, steam locomotive, steam wagon.

#### 4. Based on Drive of the vehicles :

• Left Hand drive : Steering wheel fitted on left hand side
• Right Hand drive : Steering wheel fitted on right hand side
• Fluid drive : Vehicles employing torque converter, fluid fly wheel or hydramatic transmission.

#### 5. Based on number of wheels and axles :

• Two wheeler : motor cycles, scooters
• Three wheeler : Tempo, auto-rickshaws
• Four wheeler : car, Jeep, Bus, truck
• Six wheeler : Buses and trucks have six tires out of which four are carried on the rear wheels for additional reaction.
• Six axle wheeler : Dodge(10 tire) vehicle

#### 6. Based on type of transmission:

• Automatic transmission vehicles: Automobiles that are capable of changing gear ratios automatically as they move. e.g: Automatic Transmission Cars.
• Manual transmission vehicles: Automobiles whose gear ratios have to be changed manually.
• Semi-automatic transmission vehicles: Vehicles that facilitate manual gear changing with clutch pedal.

#### 7. Based on Suspension system used:

• Convectional - Leaf Spring
• Independent - Coil spring, Torsion bar, Pneumatic.
Heat is a form of energy which transfers between bodies which are kept under thermal interactions. When a temperature difference occurs between two bodies or a body with its surroundings, heat transfer occurs.
Heat transfer occurs in three modes:
1) Conduction 2) Convection and 3) Radiation

### Conduction :

In Conduction, heat transfer takes place due to temperature difference in a body or between bodies in thermal contact, without mixing of mass. The rate of heat transfer through conduction is governed by the Fourier's law of heat conduction.
Q = -kA(dT/dx)
Where: Q is the heat flow rate by conduction
K is the thermal conductivity of body material
A is the cross-sectional area normal to direction of heat flow and
dT/dx is the temperature gradient of the section.

### Convection :

In convection, heat is transferred to a moving fluid at the surface over which it flows by combined molecular diffusion and bulk flow. Convection involves conduction and fluid flow. The rate of convective heat transfer is governed by the Newton's law of cooling.
Q = hA(Ts-T∞)
Where: Ts is the surface temperature
T∞ is the outside temperature
h is the coefficient of convection

In radiation, heat is transferred in the form of radiant energy or wave motion from one body to another body. No medium for radiation to occur. The rate of heat radiation that can be emitted by a surface at a thermodynamic temperature is based on Stefan-Boltzmann law.
Q = σT⁴
Where: T is the absolute temperature of surface
σ is the Stefan-Boltzmann constant.
Brake system used to slow down a vehicle by converting its kinetic energy into heat energy.

### Classification of Brake system :

#### On the basis of mode of actuation

• Foot brake (also called main brake) operated by foot pedal
• Hand brake – it is also called parking brake operated by hand

#### On the basis of mode of operation

• Air brakes
• Electric brakes
• Hydraulic brakes
• Mechanical brakes
• Vacuum brakes

#### On the Basis of Action on Front or Rear Wheels

• Front-wheel brakes
• Rear-wheel brakes

#### On the Basis of Method of Application of Braking Contact

• Externally – contracting brakes
• Internally – expanding brakes
Pipes are in circular cross section area, identical to the shape of a roll of paper towels. We general use pipes in our homes to supply water from water tank to kitchen, bathroom.

#### Fluid flow can be classified into three types:

• Laminar flow
• Turbulent flow
• Transitional flow

#### Laminar flow :

Occurs when the fluid flows in parallel layers, with no mixing between the layers. Where the center part of the pipe flow the fastest and the cylinder touching the pipe isn't moving at all.
The flow is laminar when Reynolds number is less than 2300.

#### Turbulent flow :

In turbulent flow occurs when the liquid is moving fast with mixing between layers. The speed of the fluid at a point is continuously undergoing changes in both magnitude and direction.
The flow is turbulent when Reynolds number greater than 4000.

#### Transitional flow :

Transitional flow is a mixture of laminar and turbulent flow, with turbulence flow in the center of the pipe and laminar flow near the edges of the pipe. Each of these flows behave in different manners in terms of their frictional energy loss while flowing and have different equations that predict their behavior.
The flow is transitional when Reynolds number is in between 2300 and 4000.
Performance of a centrifugal pump can be determined by finding the following efficiencies:
• Mechanical efficiency
• Hydraulic efficiency
• Volumetric efficiency
• Overall efficiency

### Mechanical efficiency of a centrifugal pump (ηm):

Mechanical efficiency of a centrifugal pump (ηm) is the ratio of theoretical power that must be supplied to operate the pump to the actual power delivered to the pump.
Mechanical efficiency can be used to determine the power loss in bearings and other moving parts of a centrifugal pump. It determines the actual power that must be supplied to a centrifugal pump for desired result.

### Hydraulic efficiency of a centrifugal pump (ηH):

Hydraulic efficiency of a centrifugal pump (ηH) is defined as the ratio of the useful hydrodynamic energy in fluid to Mechanical energy supplied to rotor.

### Volumetric efficiency of a centrifugal pump (ηv):

Volumetric efficiency of a centrifugal pump (ηv) is defined as the ratio of the actual flow rate delivered by the pump to the theoretical discharge flow rate (flow rate without any leakage) that must be produced by the pump.
Volumetric efficiency can be used to determine the amount of loss of liquid due to leakage in a pump during the flow.

### Overall efficiency of a centrifugal pump (ηo):

Overall efficiency of a centrifugal pump is the ratio of the actual power output of a pump to the actual power input to the pump. It is the efficiency that determines the overall energy loss in a centrifugal pump.

Overall efficiency of a centrifugal pump is the product of the volumetric efficiency and mechanical efficiency of a centrifugal pump.
Overall efficiency of a centrifugal pump (ηo) = Mechanical efficiency (ηm) × Volumetric efficiency (ηv)

Fluids are defined as substance that flow or deform under the applied shear stress. Fluid has no definite shape of its own. It assumes the shape of its container. Liquids and gases are known as fluids.

## Types of Fluids:

Depending on the behavior of fluids, fluids are divided into two types. They are

• Newtonian Fluid
• Non-Newtonian Fluid
Below about these types of fluids are discussed in brief.

### Newtonian Fluid:

Fluids that obey Newton law of viscosity are known as Newtonian Fluids.
Newton law of viscosity states that the shear stress on a fluid element layer is directly proportional to the rate of shear strain.
Examples of Newtonian fluids : water, air, kerosene

### Non-Newtonian Fluid:

Fluids that doesn't obey Newton law of viscosity are known as Non-Newtonian fluids. These fluids are the opposite of Newtonian fluids.
Examples of Non-Newtonian fluids : colloids, thick slurry, emulsions.

Engineering mechanics is the study of forces that act on bodies and the resultant motion that those bodies experience Engineering mechanics involves the application of the principles of mechanics to solve real time engineering problems.

## Types of Engineering Mechanics:

Engineering mechanics can be broadly classified into two types. They are:
1. Statics and
2. Dynamics

### 1) Statics:

Statics is the branch of mechanics that deals with the study of objects at rest. Objects at rest may or may not be under the influence of forces.

### 2) Dynamics:

Dynamics is the branch of mechanics that deals with the study of objects in motion and the forces causing such motion.

### Types of Dynamics:

Dynamics can be further classified into two types. They are:
• Kinematics
• Kinetics

Kinematics:
Kinematics is the study of motion of bodies without consideration of the cause of the motion. Kinematics deals with the space-time relationship of the motion of a body. Some examples of kinematic concepts are displacement, velocity and acceleration.

Kinetics:
Kinetics is the branch of mechanics which deals with the study of motion of bodies by considering the cause of motion.
Hydraulic turbines are Machines which convert hydraulic energy in to mechanical energy . Use the potential energy and kinetic energy of water and rotate the rotor by dynamic action of water.

### Classification of Hydraulic turbines :

#### 1) Based on type of energy at inlet to the turbine:

• Impulse Turbine : The energy is in the form of kinetic form. e.g: Pelton wheel, Turgo wheel.
• Reaction Turbine : The energy is in both Kinetic and Pressure form. e.g: Tubular, Bulb, Propellar, Francis turbine.

### 2) Based on direction of flow of water through the runner:

• Tangential flow : water flows in a direction tangential to path of rotational, i.e. Perpendicular to both axial and radial directions.
• Radial outward flow e.g : forneyron turbine.
• Axial flow : Water flows parallel to the axis of the turbine. e.g: Girard, Jonval, Kalpan turbine.
• Mixed flow : Water enters radially at outer periphery and leaves axially. e.g : Modern francis turbine.

### 3) Based on the head under which turbine works:

• High head, impulse turbine. e.g : Pelton turbine.
• Medium head,reaction turbine. e.g : Francis turbine.
• Low head, reaction turbine. e.g : Kaplan turbine, propeller turbine.

### 4) Based on the specific speed of the turbine:

• Low specific speed, impulse turbine. e.g : pelton wheel
• Medium specific speed, reaction turbine. e.g : francis wheel
• High specific speed, reaction turbine. e.g : Kaplan and Propeller turbine.

### 5) Based on the name of the originator:

• Impulse turbine - Pelton wheel, Girard, Banki turbine
• Reaction turbine - Forneyron, Jonval, Francis, Dubs, Deriaze, Thomson kalpan, Barker, Moody, Nagler, Bell.

### Three most popular hydraulic turbines are :

• Pelton wheel (Pelton turbine)
• Kaplan turbine (Propeller turbine)
• Francis turbine

#### A) Pelton turbine :

• Pelton turbine is an impulse turbine working under high head 300 metres and handling low quantity of water.
• The flow of water in Pelton turbine is tangential to the runner. So it is a tangential flow impulse turbine.
• A Pelton’s runner consists of a single wheel mounted on a horizontal shaft. Water falls towards the turbine through a pipe called  and flows through a nozzle.
• The high speed jet of water hits the buckets (vanes)on the wheel and causes the wheel to rotate.
• A spear rod which has a spear shaped end can be moved by a hand wheel.
• This movement controls the flow of water leaving the nozzle, before it strikes the bucket.
• The bucket or vane is so shaped that when the water strikes, it gets split into two and gives it an impulse force in the centre of the bucket. This bucket is also known as splitter.

#### B) Kaplan turbine :

• Kaplan turbine is a low head turbine and used for heads of less than 80 metres.
• The runner of a Kaplan turbine resembles with propeller of a ship. That is why, a Kaplan turbine is also called as propeller turbine.
• The turbine wheel, which is completely under water, is turned by the pressure of water against its blades. Guide vanes regulate the amount of water reaching the wheel.

#### C) Francis turbine :

• Francis turbine is used when the head is between 80 to 300 metres. i.e. it is a medium head turbine.
• It is a mixed flow reaction turbine. A Francis turbine rotates in a closed casing. Its wheel has many curved blades called runner vanes as many as 24. Its shaft is vertical. The wheel of a Francis turbine operates under water. The guide vanes and stay vanes control the amount of water flowing into the runner vanes.
• The runner is rotated mainly due to the weight or pressure of the flowing water.

Vibration is a mechanical phenomenon, It is a movement first in one direction and then back again in the reverse direction.
e.g: the motion of a swinging pendulum, the motion of a tuning fork.
Any simple vibration is described by three factors: its amplitude; its frequency and rate of oscillation.

Some of the general terms you will come across while studying on vibration topic are Oscillatory motion, Simple Harmonic Motion, Periodic Motion. now we will see the above mentioned terms in brief.

#### Oscillatory Motion :

Oscillatory motion is described as motion that repeats itself in a regular intervals of time. for example a sine wave or cos wave or pendulum. The time taken for an oscillation to occur is often referred to as the oscillatory period.

#### Simple Harmonic Motion :

Simple Harmonic Motion is periodic motion in which the restoring force is directly proportional to the displacement.
F = -k*x
A simple harmonic motion of a pendulum is an example of motion that is frequently used by physicists as a mean of explaining systems which are part of potential energy.
e.g such as the oscillation of a spring.

#### Periodic Motion :

In mathematics, a periodic function is a function that repeats its values in regular intervals or periods. The most important examples are the trigonometric functions, which repeat over intervals of 2π radians.
A function f(x) is said to be periodic with period P
f(x+P) = f(x) for all values of x.
An engine is a device which transforms one form of energy into another form with its associated conversion efficiency. Heat engines can be classified into two types.
They are: 1. External Combustion Engine ( EC Engine )
2. Internal Combustion Engine ( IC Engine ).

External Combustion Engine (EC Engine) :
External combustion engines are those in which combustion takes place outside the engines. Heat produced during external combustion is used for inducing useful mechanical motion in the cylinder of the engine.
Steam Engine, Stirling Engine, Steam Turbine, Closed cycle gas turbine are the types of External Combustion Engines.

Internal Combustion Engine (IC Engine) :
Internal combustion engines combustion takes place within the engine. Chemical energy of the fuel is converted to thermal energy and thermal energy is converted to mechanical energy, which moves the piston up and down inside the cylinder. Power from the piston is transmitted to the crankshaft which is ultimately transmitted to the wheels via a transmission system. Modern automobiles use internal combustion engines for propulsion.
Gasoline Engine, Diesel Engine, Wankel Engine, Open cycle Gas Turbine are the types of Internal Combustion Engines.

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine the expansion of the high temperature and high pressure gases produced by combustion apply direct force to some component of the engine. The force is applied typically to pistons, turbine blades or a nozzle.

#### Principle of operation:

Air-fuel mixture in the combustion chamber is ignited, either by a spark plug (in case of SI Engines) or by compression (in case of CI engines). This ignition produces tremendous amount of heat energy and pressure inside the cylinder. This induces reciprocating motion in the piston.
Power of the piston is transmitted to a crankshaft which undergoes rotary motion. The rotary motion is ultimately transmitted to the wheels of the vehicle, via a transmission system, to produce propulsion in the vehicle.
As the combustion takes place internally inside the cylinder (a part of working fluid circuit) the engine is called internal combustion engine.

### Classification of Internal Combustion Engines:

Today's IC engines can be classified in several ways. The major classification of Internal Combustion engines is given below:

#### 1) Application

• Automobile Engine
• Aircraft Engine
• Locomotive Engine
• Marine Engine
• Stationary Engine

#### 2) Basic Engine design

i)Reciprocating
• Single cylinder
• Multi-cylinder In-line, V, radial, opposed cylinder, Opposed Piston.
ii)Rotatory
• Single motor
• Multi motor

#### 3) Operating cycle

• Atkinson (For complete expansion SI Engine)
• Diesel (For the Ideal Diesel Engine)
• Dual (For the Actual Diesel Engine)
• Miller (For Early/Late Inlet valve closing type SI Engine)
• Otto (For the Convectional SI Engine)

#### 4) Working cycle

• Four stroke cycle
• Two stroke cycle
a) Scavenging ; direct/crankcase/cross flowback flow/loop; Uni flow
b) Naturally Aspirated or Turbocharged

#### 5) Valve/port Design and location

i) Design of valve/port
• Poppet valve
• Rotatory valve
ii) Location of valve/port

#### 6)Fuel

i) Convectional
• Crude oil derivatives; Petrol, diesel
• Other sources; coal, Bio-mass, Tar stands, shale
ii) Alternative
• Petroleum derived: CNG, LPG
• Bio-mass Derived: alcohols, Vegetable oils, producer gas,   Biogas and Hydrogen
iii) Blending
iv) Bi-fuel and Dual fuel

#### 7)Mixture preparation

• Carburetion
• Fuel injection

#### 8) Ignition

a)Spark ignition

b)Compression Ignition

#### 9) Stratification of charge

i) Homogeneous Charge
ii) Stratified charge
• With carburetion
• With fuel injection

#### 10) Combustion chamber Design

i). Open chamber: Disc, wedge, hemispherical, Bowl-in-piston, Bath tub.
ii). Divided chamber : (For CI) 1. Swirl chamber, 2. Pre-chamber
(for SI) 1. CVCC, 2. Other designs

#### 11) Cooling

• Direct air-cooling
• Indirect air-cooling
• Low heat rejection engine