BASIC DEFINITIONS IN THERMAL ENGINEERING

THERMAL ENGINEERING :

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

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

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

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

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

Nozzle:
          Nozzle is a duct of varying cros-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 combustion chamber of engine cylinder.

Supercharging:          Actually, power output of engine depends on what amount of air enter into the engine through intake manifold. Amount of entry aiy if increased, then must be engine speed will increased. 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.Superchargeris driven by a belt from engine crakshaft. It is installed in intake system.

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

Governeor:          Its function is to regulate mean speed of engine when there are variation in the load. If load incrases on the engine, then engine's speed must decrease. In that case supply of working fluid have to increase. In the otherway, if load decrease on the engine, then engine' speed must increase. In that case supply of working fluid have to decrease.Governor automatcally, controls the supply of working fluid to the engine with varying load condition.

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

Rating of fuel:
S.I. Engine:
Octane number. Octane number indicates ability of fuel to resist knock.

C.I. Engine:
Cetane Number.cetane number indicates ability of ignition of diesel fuel. That means, how much fast ignites diesel fuel.