172.After burning

After Burning

After burning is said to occur when the third phase of combustion extends over a long period. It may be caused by incorrect fuel grade, bad atomization, poor or excess penetration, incorrect fuel temperature, incorrect injection timing, insufficient air supply, or any combination of these. Slow burning, high viscosity, high density, high carbon content fuels may also cause after burning of a serious nature leading to engine damage.

Effect of After Burning

After burning creates high exhaust temperatures and may cause overheating of the engine in severe cases. Some drop in the maximum firing pressure usually accompanies this. There is a loss of thermal efficiency when after burning occurs, due to greater loss of heat to exhaust gases and the transfer of large amount of heat to the cooling water. There is a risk of damage to exhaust valves and scavenge fires.