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Tuesday, 25 December 2012

Internal Combustion Engine



Cooling: Why Cooling is required in Internal Combustion Engine?

In Automobile engineering, to get the work done from internal combustion engine, we have to burn air-fuel mixture inside the cylinder. When the combustion of air-fuel mixture takes place in the engine cylinder, a temperature as high as 2500 degree centigrade is reached. To withstand such a high temperature we have to use very high melting point material for construction of engine. 



 Practically it is less possible because,"Platinum”a metal which has one of the highest melting point, melts at above 1800 degree centigrade.It has been practically found that out of total heat generated by internal combustion engine due to combustion of fuel, only 30% of heat is converted in useful work, out of remaining 70% about 40 % is carried by exhaust gases into the atmosphere during exhaust stroke. The rest of 30% must be passed to atmosphere by some suitable arrangement.

Here we find the necessity of cooling. In addition to overheating, large temperature differences may lead to distortion of the engine components due to set up of thermal stresses. If the cooling system is not provided to internal combustion engine, the lubricating oil film would break down and the lubricating oil will decompose to give gummy and carbon deposits.


In lack of cooling system, a complete seizure of the piston, bearing and other important parts will occur. Due to this, there will be more frequent replacements of the components are required. It will also increase the repairing cost and breakdown period. The engine life will be reduced considerably.


It should also be noted that higher temperatures lower the volumetric efficiency of the engine, promote pre-ignition and tendency of the engine to detonate. The object of cooling is achieved by any of the two methods,
01)Air Cooling
02)Water Cooling


Properties of an efficient cooling system
The following are the two main properties desired of an efficient cooling system,


01)It must be capable of removing only about 30% of the heat generatedin the combustion chamber. Too much heat removal will lower the thermal efficiency of the engine.


02) It should remove heat at a fast rate when engine is hot. It is also required to be very slow cooling at the starting of the engine, so that the different working parts of the internalcombustion engine reach their operating temperature in a short time period.


If you are using water cooled engine, then are little chances of freezing of water in cold weather conditions, if we keep engine without use for very long time. To overcome this problem, we have to mix anti freezers in cooling water.


Hope the information above will help you to understand about cooling.

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