CUT SECTIONAL INTERNAL COMBUSTION ENGINES

CUT SECTIONAL INTERNAL COMBUSTION ENGINES

INTRODUCTION AND THEORY:

A HEAT ENGINE IS A DEVICE, WHICH CONVERTS THE CHEMICAL ENERGY OF A FUEL INTO THERMAL ENERGY AND USES THIS ENERGY TO PRODUCE MECHANICAL WORK. HEAT ENGINES ARE CLASSIFIED INTO TWO BROAD TYPES.

ANY TYPE OF ENGINE OR MACHINE, WHICH DERIVES HEAT ENERGY FROM THE COMBUSTION OF FUEL OR ANY OTHER SOURCE AND CONVERTS THIS ENERGY INTO MECHANICAL WORK, IS TERMED AS A HEAT ENGINE.

·         EXTERNAL COMBUSTION ENGINES

·         INTERNAL COMBUSTION ENGINES.

INTERNAL COMBUSTION ENGINES:

INTERNAL COMBUSTION ENGINE IN WHICH THE COMBUSTION OF FUEL TAKES PLACE INSIDE THE CYLINDER IS KNOWN AS I.C. ENGINE. IN AN INTERNAL COMBUSTION ENGINE, THE PRODUCTS OF COMBUSTION ARE DIRECTLY THE MOTIVE FLUID. DIESEL ENGINE AND PETROL ENGINE ARE THE EXAMPLES OF THIS TYPE, WHERE THE WORKING SUBSTANCE IS THE PRODUCT OF COMBUSTION. RECIPROCATING INTERNAL COMBUSTION ENGINES OFFERS FOLLOWING ADVANTAGES OVER EXTERNAL COMBUSTION ENGINES:

·         OVERALL EFFICIENCY IS HIGH.

·         GREATER MECHANICAL SIMPLICITY.

·         GENERAL LOWER INITIAL COST.

·         EASY STARTING FROM COLD CONDITIONS.

·         THESE UNITS ARE COMPACT AND THUS REQUIRE LESS SPACE.

·         WEIGHT TO POWER RATIO IS GENERALLY LOWER.

I.C. ENGINE CLASSIFICATION

THE I.C. ENGINE CAN BE CLASSIFIED ON THE FOLLOWING BASIS

WORKING CYCLE

·         SPARK IGNITION ENGINES

·         COMPRESSION IGNITION ENGINES

NO. OF STROKES

·         TWO STROKE ENGINES

·         FOUR STROKE ENGINES

 

PARTS COMMON TO BOTH PETROL AND DIESEL ENGINE

·         CYLINDER

·         CYLINDER HEAD

·         PISTON

·         PISTON RINGS

·         GUDGEON PIN

·         CONNECTING ROD

·         CRANKSHAFT

·         CRANK

·         ENGINE BEARING

·         CRANK CASE

·         FLYWHEEL

·         GOVERNOR

·         VALVE AND VALVE OPERATING MECHANISMS

PARTS FOR PETROL ENGINES ONLY

·         SPARK PLUGS

·         CARBURETTOR

·         FUEL PUMP

 

PARTS FOR DIESEL ENGINE ONLY

·         FUEL PUMP

·         INJECTOR

CYLINDER: THE CYLINDER CONTAINS GAS UNDER PRESSURE AND GUIDES THE PISTON. IT IS IN DIRECT CONTACT WITH THE PRODUCTS OF COMBUSTION AND IT MUST BE COOLED. IT IS ONE OF THE MOST IMPORTANT PART OF THE ENGINE IN WHICH THE PISTON MOVES TO AND FRO IN ORDER TO DEVELOP POWER. GENERALLY, THE ENGINE CYLINDER HAS TO WITHSTAND A HIGH-PRESSURE AND TEMPERATURE MORE THAN 2000⁰C.THE CYLINDER IS MADE OF HARD GRADE CAST IRON AND IS USUALLY CAST IN ONE PIECE.

ENGINE BODIES ARE DESIGNED OF STEEL ALLOYS OR ALUMINIUM ALLOYS.

CYLINDER HEAD: HEAD IS AN ARRANGEMENT WHICH COVERS CYLINDER BORE AND CONSISTS OF SUCTION AND EXHAUST VALVES. CYLINDER AND CYLINDER HEAD ARE MADE FROM THE SAME MATERIAL, USUALLY CAST AS ONE PIECE. THE MAIN FUNCTION OF CYLINDER HEAD IS TO SEAL THE WORKING ENDS OF THE CYLINDER AND NOT TO PERMIT ENTRY AND EXIT OF GASES ON COVER HEAD VALVE ENGINES.

PISTON: PISTON IS THE HEART OF AN ENGINE WHOSE MAIN FUNCTION IS TO TRANSMIT THE FORCE EXERTED BY THE BURNING OF CHARGE TO CONNECTING ROD. A PISTON IS FITTED TO EACH CYLINDER AS A FACE TO RECEIVE GAS PRESSURE AND TRANSMIT THE THRUST TO THE CONNECTING ROD

PISTON RINGS: PISTON RINGS ARE HOUSED IN THE CIRCUMFERENTIAL GROOVES PROVIDED ON THE OUTER SURFACE OF THE PISTON. TWO SETS OF RINGS ARE USED GENERALLY. THE FUNCTION OF UPPER RING IS TO PROVIDE AIRTIGHT SEAL TO PREVENT LEAKAGE OF BURNT GASES IN TO THE LOWER PISTON. SIMILARLY, THE FUNCTION OF LOWER RING IS TO PROVIDE EFFECTIVE SEAL TO PREVENT LEAKAGE OF THE OIL RING IN TO THE ENGINE CYLINDER.

CONNECTING ROD: IT IS A LINK BETWEEN THE PISTON AND CRANKSHAFT.

FUNCTION - TO TRANSMIT FORCE FROM THE PISTON TO THE CRACK SHAFT. RECIPROCATING MOTION IS CONVERTED IN TO CIRCULAR MOTION OF CRACK SHAFT. A SPECIAL CARE IS TO BE TAKEN WHILE DESIGNING THE CRANKSHAFT, AS IT IS SUBJECTED TO ALTERNATIVELY COMPRESSIVE AND TENSILE STRESSES, AS WELL AS BENDING STRESSES. A CONNECTING ROD IS MADE OF SPECIAL STEEL ALLOYS OR ALUMINUM ALLOYS.

CRANK SHAFT: CRANKSHAFT IS THE BACK OF AN ENGINE. IT CONSISTS OF ONE OR MORE ECCENTRIC PORTIONS CALLED CRANKS. THAT PART OF THE CRANK, TO WHICH BIGGER END OF THE CONNECTING ROD IS FITTED, WITH THE HELP OF CRANK PIN. THE CRANK SHAFTS OF AN INTERNAL COMBUSTION ENGINE RECEIVE VIA ITS CRANKS THE EFFORTS SUPPLIED BY THE PISTONS TO THE CONNECTING RODS. THE SHAPE OF THE CRANKSHAFTS I.E. THE MUTUAL ARRANGEMENTS OF CRANKS DEPENDS ON THE NUMBERS AND ARRANGEMENTS OF CYLINDERS AND THE TURNING ORDER OF THE ENGINE.

CRANK CASE: IT HOLDS THE CYLINDER AND CRANKSHAFT OF AN ENGINE. IT ALSO SERVES AS A SUMP FOR THE LUBRICATING OIL.

FLYWHEEL: A WHEEL MOUNTED ON THE CRANKSHAFT, WHOSE FUNCTION IS TO MAINTAIN ITS SPEED CONSTANT. IT IS DONE BY STORING EXCESS ENERGY DURING THE POWER STROKE, WHICH IS RETURNED DURING OTHER STROKES. THE WEIGHT OF THE FLYWHEEL DEPENDS ON THE NATURE OF VARIATION OF THE PRESSURE.