BASICS OF HEAT ENGINE AND ITS CLASSIFICATION

BASICS OF HEAT ENGINE AND ITS CLASSIFICATION

HEAT ENGINE:

A HEAT ENGINE IS A DEVICE WHICH TRANSFORMS THE CHEMICAL ENERGY OF A FUEL INTO THERMAL ENERGY AND USES THIS ENERGY TO PRODUCE MECHANICAL WORK.

IT IS CLASSIFIED INTO TWO TYPES:

•  EXTERNAL COMBUSTION ENGINE
• INTERNAL COMBUSTION ENGINE

1.       EXTERNAL COMBUSTION ENGINE:

IN THIS ENGINE, THE PRODUCTS OF COMBUSTION OF AIR AND FUEL TRANSFER HEAT TO A SECOND FLUID WHICH IS THE WORKING FLUID OF THE CYCLE.

EXAMPLES:

• IN THE STEAM ENGINE OR A STEAM TURBINE PLANT, THE HEAT OF COMBUSTION IS EMPLOYED TO GENERATE STEAM WHICH IS USED IN A PISTON ENGINE (RECIPROCATING TYPE ENGINE) OR A TURBINE (ROTARY TYPE ENGINE) FOR USEFUL WORK.
• IN A CLOSED CYCLE GAS TURBINE, THE HEAT OF COMBUSTION IN AN EXTERNAL FURNACE IS TRANSFERRED TO GAS, USUALLY AIR WHICH THE WORKING FLUID OF THE CYCLE. 

2.       INTERNAL COMBUSTION ENGINE:

IN THIS ENGINE, THE COMBUSTION OF AIR AND FUELS TAKE PLACE INSIDE THE CYLINDER AND ARE USED AS THE DIRECT MOTIVE FORCE. IT CAN BE CLASSIFIED INTO THE FOLLOWING TYPES:

a.       ACCORDING TO THE BASIC ENGINE DESIGN

·         RECIPROCATING ENGINE (USE OF CYLINDER PISTON ARRANGEMENT)

·         ROTARY ENGINE (USE OF TURBINE)

b.       ACCORDING TO THE TYPE OF FUEL USED

·         PETROL ENGINE

·         DIESEL ENGINE

·         GAS ENGINE (CNG, LPG)

·         ALCOHOL ENGINE (ETHANOL, METHANOL ETC)

c.        ACCORDING TO THE NUMBER OF STROKES PER CYCLE

·         FOUR STROKE

·         TWO STROKE ENGINE

d.       ACCORDING TO THE METHOD OF IGNITING THE FUEL

·         SPARK IGNITION ENGINE

·         COMPRESSION IGNITION ENGINE

·         HOT SPOT IGNITION ENGINE

e.       ACCORDING TO THE WORKING CYCLE

·         OTTO CYCLE (CONSTANT VOLUME CYCLE) ENGINE

·         DIESEL CYCLE (CONSTANT PRESSURE CYCLE) ENGINE

·         DUAL COMBUSTION CYCLE (SEMI DIESEL CYCLE) ENGINE

f.         ACCORDING TO THE FUEL SUPPLY AND MIXTURE PREPARATION

·         CARBURETTED TYPE (FUEL SUPPLIED THROUGH THE CARBURETTOR)

·         INJECTION TYPE (FUEL INJECTED INTO INLET PORTS OR INLET MANIFOLD, FUEL INJECTED INTO THE CYLINDER JUST BEFORE IGNITION)

g.       ACCORDING TO THE NUMBER OF CYLINDER

·         SINGLE CYLINDER

·         MULTI-CYLINDER ENGINE

h.       METHOD OF COOLING

·         WATER COOLED

·         AIR COOLED

i.         SPEED OF THE ENGINE

·         SLOW SPEED

·         MEDIUM SPEED

·         HIGH SPEED ENGINE

j.         CYLINDER ARRANGEMENT

·         VERTICAL

·         HORIZONTAL

·         INLINE

·         V-TYPE

·         RADIAL

·         OPPOSED CYLINDER OR PISTON ENGINES.

k.       VALVE OR PORT DESIGN AND LOCATION

·         OVERHEAD (I HEAD)

·         SIDE VALVE (L HEAD); IN TWO STROKE ENGINES: CROSS SCAVENGING, LOOP SCAVENGING, UNIFLOW SCAVENGING

l.         METHOD GOVERNING

·         HIT AND MISS GOVERNED ENGINES, QUANTITATIVELY GOVERNED ENGINES

·         QUALITATIVELY GOVERNED ENGINE

m.     APPLICATION

·         AUTOMOTIVE ENGINES FOR LAND TRANSPORT

·         MARINE ENGINES FOR PROPULSION OF SHIPS

·         AIRCRAFT ENGINES FOR AIRCRAFT PROPULSION

·         INDUSTRIAL ENGINES

·         PRIME MOVERS FOR ELECTRICAL GENERATORS.