Question
Download Solution PDFWhich of the following factors contribute towards detonation in a SI engine?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
Knocking or detonation is due to the auto-ignition of the end portion of the unburned charge in the combustion chamber.
Cause of detonation:
Compression ratio:
Increasing the compression ratio increases both the temperature and pressure. An increase in temperature reduces the delay period of the end charge. Hence tendency to knock increases. Therefore, in order to reduce the possibility of detonation, it is essential to keep the compression ratio as low as possible.
Lean fuel mixture:
A lean mixture burns slower than a rich mixture. This longer burning time causes higher combustion chamber temperature, which promotes the tendency for unburned fuel in front of the spark ignition flame to detonate.
Engine Overheating:
Even the excessive intake air temperature or overheating of the engines can cause pre-ignition because the mixture in the cylinder will be at a higher temperature and so closer to the ignition point.
Last updated on Jul 1, 2025
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