HIGHLIGHTS OF INTERNAL COMBUSTION ENGINES

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HIGHLIGHTS OF INTERNAL COMBUSTION ENGINES

The followings are the highlights of the internal combustion engines:

  1.  There is one working stroke in one revolution in a two stroke cycle, .
  2. In a four stroke cycle, there is one working stroke in two revolutions.
  3. In the petrol or diesel engine, exhaust gases are forced out. This process is called Scavenging.
  4.  Burnt gases are exhausted during the discharge stroke in a four stroke engine.
  5. While in the case of two stroke, fresh charge enters at a high velocity and it pushes the exhaust gases out.
  6. Application of four stroke petrol engines are for light vehicles. These are cars, jeeps and small power generating sets.
  7. Two stroke petrol engines are for very light vehicles. These include motor cycles, scooters, three wheeler and portable crop sprayers.
  8.  Four stroke diesel cycles are used for heavy machinery. These include diesel power plants, trucks, buses, road rollers, water pumps, diesel locomotives and tractors.
  9. Applications of two stroke diesel cycle is found in marine engines.
  10. Stoichiometric air-fuel ratio (AFR) is the theoretical air-fuel ratio required for complete combustion.  For a petrol engine, the stoichiometric air-fuel ratio is around 14.7:1.  It means that 14.7 kg of air is required to burn completely 1 kg of petrol.
  11. When the air-fuel ratio is more , the air-fuel mixture is called lean mixture. When the air-fuel ratio is less  the air-fuel mixture is called rich mixture. For a petrol engine, if the air fuel ratio is 16:1, it will be a lean mixture. If the air fuel ratio is 10:1, it is a rich mixture.
  12. Air fuel ratio even for diesel is almost the same.
  13. Petrol engine uses a spark plug to ignite the mixture. In case of diesel, mixture is ignited by a higher compression ratio.
  14. Rich mixture is required for starting, idling and maximum power generation.
  15. Lean mixture is never required as it will result in wastage of fuel.
  16. There are two methods of fuel injection in diesel engines. These are  air blast injection and airless (or solid) injection.
  17. When combustion of the fuel takes place, there is as high as 2500 0 C temperature. Piston and other parts may not be able to withstand such high temperatures.  Hence engine cooling is a must.
  18. Sudden rise of temperature and pressure in the cylinder with a loud sound is called detonation. It has to be stopped at any cost.
  19. Chemicals added to suppress detonation are called Dopes.
  20. Supercharging is the process of increasing the density of the air fuel mixture in petrol engines and that of air in petrol engines using compressed air with the help of a compressor.
  21. Highlights of the internal combustion engines helps in the proper selection of an engine for a particular application.