Explain Delay Period in detail.
1 Answer
Answer :
Delay period: Ignition delay period is the time period between start of injection and start of combustion, has a great influence on the correct optimization of a diesel engine. The knock phenomenon of C.I. engine depends upon delay period. If delay period is small then less amount of fuel is admitted into cylinder. When small amount of fuel is burns then there is smooth pressure rise, so there is no knocking. If the delay period is very long, then more amount of fuel is accumulated in the combustion chamber. When it actually burns, sudden pressure rise will cause the cylinder wall to vibrate, thus it produces noise and this is said to be knocking. It is period during which some fuel has been admitted but has not yet been ignited. The ignition delay is counted from the start of injection to the point where P-θ curve separates from the pure air compression curve. This ignition delay can be further divided into Physical delay and chemical delay. Physical delay includes fuel atomization, vaporization, mixing with air, and mixture rose in temperature. Pre-flame reactions occur during chemical delay