The knock in diesel engine occurs due to

The knock in diesel engine occurs due to Instantaneous and rapid burning of the first part of the charge. Diesel engine knocks when there is accumulation of fuel in the combustion chamber which happens when the injected fuel fails to burn as there will a huge delay period. And at a specific time all mixture burns simultaneously which causes increase in peak pressure and shock waves travel at higher speeds and can lead to permanent damage to piston crown and cylinder wall and head.