Question

Low engine speeds will give low turbulence and low flame velocities and knock may occur at low speed.

(a) True

(b) False

The question was posed to me in an international level competition.

I want to ask this question from Knocking in S.I. Engine in portion Combustion and Combustion Chambers of IC Engine

Answer 1

The correct answer is:

(a) True

Explanation: At low engine speeds, the turbulence within the combustion chamber is typically lower, and the flame velocity (the rate at which the combustion front propagates through the mixture) tends to decrease as well. This slower combustion process can lead to incomplete combustion and increased chances of knocking (detonation), especially at low speeds or under high load conditions. Knocking occurs when the air-fuel mixture ignites prematurely or unevenly, creating pressure waves that cause engine damage. While knocking is more common at higher engine speeds, it can still occur at low speeds due to these factors. Thus, low engine speeds with insufficient turbulence and flame velocity can indeed contribute to knocking in an S.I. engine.