Basic Terms used in mechanical engineering (part-2)

Boiler/Steam Generator:It is a closed vessel which is made of steel. Its function is to transfer heat to water to generate steam

Economiser:
It is a part of the boiler. Its function is to heat feed water which is supplied to the boiler.

Superheater:
It is a part of the boiler. Its function is to increase the temperature of steam into the boiler.

Air-Preheater:
It is a part of the boiler. Its function is to preheats the air to be supplied to the furnace and it recovers heat from exhaust gas.


Boler Draught:

It is an important term for the boiler. It is the difference of pressure above and below the fire grate. This pressure difference has to maintain very carefully inside the boiler. It actually maintained the rate of steam generation. This depends on the rate of fuel burning. Inside the boiler rate of fuel burning is maintained with the rate of entry fresh air. If the proper amount of fresh air never entered into the boiler, then the proper amount of fuel inside the boiler never be burnt. So, proper fresh air enters into the boiler only by maintaining boiler draught.

Nozzle:

The nozzle is a duct of varying cross-sectional area. Actually, it is a passage of varying cross-sectional area. It converts steam's heat energy into mechanical energy. It is one type of pipe or tube that carrying liquid or gas.

Scavenging:
It is the process of removing burnt gas from the combustion chamber of the engine cylinder.

Supercharging:

Actually, the power output of an engine depends on what amount of air enter into the engine through the intake manifold. The amount of entry air if increased then must be engine speed will increase. The amount of air will be increased by increasing inlet air density. The process of increasing inlet air density is supercharging. The device which is used for supercharging is called supercharger.The supercharger is driven by a belt from the engine crankshaft. It is installed in the intake system.

Turbocharging:

Turbocharging is similar to the supercharging. But in that case, the turbocharger is installed in exhaust system whereas supercharger is installed in the intake system. The turbocharger is driven by force of exhaust gas. Generally, the turbocharger is used for the 2-stroke engine by utilizing exhaust energy of the engine, it recovers energy otherwise which would go waste.

Governor:

Its function is to regulate the mean speed of the engine when there is variation in the load. If load increases on the engine, then engine's speed must decrease. In that case supply of working fluid have to increase. In the other way, if load decrease on the engine, then engine' speed must increase. In that case supply of working fluid have to decrease.Governor automatically controls the supply of working fluid to the engine with varying load condition.

Flywheel:

It is one of the main parts of the I.C. engine. It's main function id to store energy in the time of working stroke or expansion stroke. And, it releases energy to the crankshaft in the time of suction stroke, compression stroke & exhaust stroke. Because the engine has only one power producing stroke.

Rating of fuel:
S.I. Engine (Spark Ignition Engine):
Octane number. Octane number indicate the ability of the fuel to resist knock.

C.I. Engine (Compression Ignition Engine):
Cetane Number. Cetane number indicates the ability of ignition of diesel fuel. That means, how much fast ignites diesel fuel.

Stoichiometric ratio:

It is the chemically correct air-fuel ratio by volume. By which theoretically sufficient oxygen will be gotten to burn all combustible elements in fuel completely.

Heat Transfer:

It is a science which deals with energy transfer between material bodies as a result of temperature difference.There is three way to heat transfer such as-Conduction, Convection, Radiation.

Heat Exchanger:

It is one type of device which can transfer heat from one fluid to another fluid. Example- Radiator, Intercooler, preheater, condenser, boiler etc.

Refrigeration:

It is the process of removing heat from a substance. Actually, extraction of heat from a body whose temperature is already below the temperature of its surroundings.

1 tonne of refrigeration (T.R):

It is the amount of refrigeration effect or cooling effect which is produced by uniform melting of 1-tonne ice in 24 hours from or at 0-degree centigrade or freezing 1-tonne water in 24 hours from or at 0-degree centigrade.

Humidification:It is the addition of moisture to the air without change dry bulb temperature.

Dehumidification:
It is the removal of moisture from the air without change dry bulb temperature.

Gear Train:The meshing of two or more gear. It can transmit power from one shaft to another shaft.