What is the difference between knocking and detonation

There are generally two theories for knocking. These theories led many people to use the term detonation for knocking. In general, detonation is the cause and knocking is the after effect. Those who deal the terms knocking and detonation as a separate phenomenon, do so by referring auto-ignition theory as knocking and detonation theory as detonation. So, depending on the context it can mean the same thing or different thing. Knocking is the result of the rapid combustion of end gas ahead of flame front prior to normal combustion.

This cause a sharp rise of pressure inside the cylinder and cause metal pinging sound known as knock. Severe knocking causes the wear of cylinder, piston, rod etc. This wear gives the appearance of erosion, abrasion or the sandblasted look similar to the damage caused in hydraulic machines by cavitation. Most of the times, the two terms are confusing and used interchangeably. But they are two different situations in engines, as discussed above in this article. The difference between knocking and detonation is that, knocking brings some several drawbacks to the engine such as, overheating of spark plug points, erosion of the combustion chamber surface and rough, inefficient operation whereas detonation can cause abrasion, mechanical damage and overheating in engines.

Available here 2. Firestone Complete Auto Care. Available here 3. Available here 4. Available here. With a mind rooted firmly to basic principals of chemistry and passion for ever evolving field of industrial chemistry, she is keenly interested to be a true companion for those who seek knowledge in the subject of chemistry.

Your email address will not be published. Figure A Car Engine. Figure A Combustion Chamber. Leave a Reply Cancel reply Your email address will not be published. Knocking vs Detonation. Effect on the Engine. Knocking brings several drawbacks to the engine such as, overheating of spark plug points, erosion of the combustion chamber surface and rough, inefficient operation.

Detonation can cause abrasion, mechanical damage and overheating in engines. It is most important to note that factors that tend to reduce detonation in the SI engine increase knocking in CI engine and vice versa because of the following reason.

The detonation of knocking in the SI engine is due to simultaneous auto ignition of the last part of the charge. To eliminate detonation in the SI engine we want to prevent all together the auto ignition of the last part of the charge and therefore desire a long delay period and high self ignition temperature of the fuel. To eliminate knocking the CI engine we want to achieve auto ignitions early as possible therefore desire a short delay period and low self ignition temperature of the fuel.

Table 6. Developed by Therithal info, Chennai. Toggle navigation BrainKart. Posted On : Diesel knocking and detonation We already know that if the delay period is long, a large amount of fuel will be injected and accumulated in the chamber. Solved Problems: Gas Power Cycles. Internal Combustion Engines. Components and functions of IC Engines.