Mechanical Engineering - IC Engines and Nuclear Power Plants - Discussion

In CI engine knocking is caused by ignition delay, so an increase in wall temperature reduce knocking.

Then, What is for si engine?

Knocking will increase when in case IC engines, where as in CI engines knocking will decreases.

@All.

Why Wall Temperature Reduces Knock in CI Engines.

In a diesel (CI) engine, knocking is caused by a long ignition delay. When the ignition delay is long, a large amount of fuel accumulates in the combustion chamber before the first flame appears. When this large mass of fuel finally ignites, it burns almost instantaneously, causing a violent pressure rise known as "diesel knock".

Increasing the wall temperature helps reduce this delay through the following mechanisms:.

Faster Vaporization: Hotter walls transfer more heat to the incoming air and fuel droplets, causing the fuel to vaporize and mix with air much faster.

Reduced Ignition Delay: Higher temperatures accelerate the chemical pre-flame reactions, shortening the time between fuel injection and the start of combustion.

Smoother Pressure Rise: Because the fuel ignites sooner after being injected, less fuel accumulates in the chamber, leading to a more controlled and gradual pressure rise.