DAILY ONE INFORMATION

What is detonation? Detonation : At present the amount of power that can be developed in the cylinder of a petrol engine is fixed by the liability of a fuel to detonate, just before the flame has completed its course across the combustion   chamber and remaining unburnt charge fires throughout its mass spontaneously without external assistance. The result is a tremendously rapid and increase in pressure which sets up pressure waves that hit the cylinder walls with such violence that the walls emit a sound like a ping. It is the ping that   manifests detonation. Thus a very sudden rise of pressure during combustion accompanied by metallic hammer like sound is called detonation. The region in which detonation occurs is farthest removed from the sparking plug , and is named the detonation zone and even with severe detonation this zone is rarely more than one quarter the clearance volume.

What is per-ignition???? Pre-ignition:         Is the ignition of the homogeneous mixture in the cylinder, before the timed ignition spark occurs, caused by the local overheating of the combustible mixture? For premature ignition of any local hot-spot to occur in advance of the timed spark on the combustion stroke it must attain a minimum temperature of something like 700-800 degree centigrade. ·          Pre-ignition is initiated by some overheated projecting part such as the sparking plug electrodes, exhaust valve head , metal corners in the combustion chamber, carbon deposits or protruding cylinder head gasket rim ·          However, pre-ignition is also caused by persistent detonating pressure shock waves scoring away the stagnant gases which normally protect the combustion chamber walls. The resulting increased heat flow through the walls raises t...

Comparison Between a Petrol Engine and A Diesel Engine: In this post the information is purely based on exam point of view for the students struggling for the answer for the above topic Petrol engine: 1 Air petrol mixture is sucked in the engine cylinder during suction stroke. 2 Spark-plug is used. 3 Power is produced by spark ignition. 4 Thermal efficiency up to 25% 5 Occupies less space. 6   More running cost. 7   Light in weight. 8 Fuel costlier. 9 Petrol being volatile is dangerous. 1 Pre ignition possible. 1 Works on otto cycle. 1 Less dependable. 1 Used in cars and motor cycles. Diesel engine:   Only air is sucked during suction stroke.     Employs an injector. 3 Power is produced by compression ignition. 4 Thermal efficiency up to 40%. 5 Occupies more space. 6 Less running cost.   Heavy in weight. 8 Fuel cheaper. 9 Diesel is non dangerous as it is non volatile. 1 Pre ignition not...