In mechanical or automobile field petrol engine or diesel engine is used for any particular job.So,it is most important to know which type of engine is most suitable for selection.For the proper selection of engine,we must compare these engines with each other.By this way we come to know the advantages and disadvantages of particular engine.Here i am comparing petrol engine and diesel engine which is widely used in one or another purpose.
01)In petrol engine a charge of petrol and air is taken inside the cylinder during suction stroke which is further compressed during compression stroke.Pre-ignition can be achieved in petrol engine as there is increase in temperature due to compression above the ignition point of petrol.In diesel engine,only air is compressed during compression stroke and fuel is injected afterwards.That's why no pre-ignition achieved in diesel engine.
02)The diesel engine is more difficult to start due to greater cranking efforts required to overcome the higher compression ratio.
03)Petrol engines has more chances of fire hazards as compared to diesel engine.
04)A carburettor is used in petrol engine,which supplies the mixture of air and petrol in the proper portion according to requirement but in diesel engine,an injector or auto miser is used to inject the fuel at the end of compression stroke.
05)No external source of heat is required to burn the fuel in diesel engine as it burns by the heat of compressed air.In petrol engine,a spark plug is required to ignite the charge with an electric spark.
06)The diesel engine is heavier and stronger than petrol engine.As a result,diesel engine is more expensive in initial cost and repairing cost.A higher grade of material and workmanship is required in diesel engine due to high compression ratio.
07)Though initial cost of diesel engine is more but it will run almost double than petrol engine for same quantity of fuel.The cost of diesel is less than petrol,hence running cost is lower than petrol engine.For all sort of heavy work diesel engine gets more preference than petrol engine.
08)On reduced load,the the petrol engine is superior to the diesel engine because of better mixing of fuel and air.
09)The thermal efficiency of diesel engine is higher than petrol engine because of high compression ratio used.
10)The petrol engine works on Otto cycle where as diesel engine works on Diesel cycle.
From the above comparison we can see that both engines have certain advantages and disadvantages.The determination of the type selected for a particular job must be based on these relative advantages and disadvantages in relation to the requirement of the task to be performed.
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