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What is engine knocking and why does it occur?

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What is engine knocking and why does it occur?

Knocking (also knock, detonation, spark knock, pinging or pinking) in spark ignition internal combustion engines occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but one or more pockets of air/fuel mixture explode …

What affects knock in IC engine?

The usage of hydrogen in compression ignition engine leads to production of knocking or detonation because of its lower ignition energy, wider flammability range, and shorter quenching distance. Knocking combustion causes major engine damage, and also reduces the efficiency.

What is knocking and how is avoided in engines?

Once the knock sensor receives the signal that knocking has started inside the cylinder, it sends the signal to the ECU. The ECU commands the spark plug to retard the timing of the ignition. Therefore, the ignition takes place at a bit later stage and the high pressure and temperature are avoided.

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How can I stop my IC engine from knocking?

In spark ignition engines knocking can be reduced by:

  1. Increasing the cooling water temperature.
  2. Retarding the spark advance.
  3. Increasing the inlet air temperature.

What does knocking sound in engine mean?

The knocking sound often occurs when the air-fuel mixture is incorrect, which causes the fuel to burn in uneven pockets rather than uniform bursts. Left untreated, it can cause damage to the piston and cylinder wall. A knocking sound can also be caused by a lack of lubrication in the upper cylinder head area.

What is the main objective of supercharging of the engine?

The objective of supercharging is to increase the charge density of the working medium (air or air-fuel mixture), by any means and with the help of a suitable system, before it enters the work cylinder, i.e., to precompress the charge.

What are the factors causing knocking?

From the above discussion on knock, it may be seen that four major factors are involved in either producing or preventing knock. These are the temperature, pressure, density of the unburned charge and the time factors.

What are the factors of knocking?

Factors affecting Detonation or Knocking in SI engine:

  • Compression ratio: The pressure and temperature at the end of compression increases with increase in compression ratio.
  • Supercharging:
  • Increasing inlet temperature:
  • Increase in load:
  • Advancing the spark:
  • Flame travel distance:
  • Spark plug location:
  • Engine size:
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What is the difference between knocking and detonation?

Knocking vs Detonation Knocking is the making sharp sounds due to uneven combustion of fuel in the cylinder of a vehicle engine. Detonation is the process of pre-ignition or auto-ignition of a fuel in an engine’s combustion chamber.

What causes diesel knock?

Diesel knock is the clanking, rattling sound emitted from a running diesel engine. This noise is caused by the compression of air in the cylinders and the ignition of the fuel as it is injected into the cylinder. In a diesel engine, only the air is compressed.

What causes a knocking sound when you accelerate?

If your car makes noise when accelerating, it can be a problem like a worn-out clutch disc or wheel bearing. That can be a clutch problem in a manual transmission, an automatic transmission issue, a worn u-joint or CV joint, or something in the brakes, suspension or steering.

What is knocking in a car engine?

Spark ignition In internal combustion engines, knocking (also knocking, explosion, spark knocking, pinging or pinking) occurs when the combustion of some air/fuel mixture in the cylinder does not result in flame front propagation by the spark plug, but air / One or more pockets of the fuel mixture burst outside the normal combustion front envelope.

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What causes a knocking sound in a motorcycle engine?

The fuel-air charge is meant to be ignited by the spark plug only, and at a precise point in the piston’s stroke. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. The shock wave creates the characteristic metallic “pinging” sound,…

What are the effects of knocking on a piston?

Such wear gives the appearance of erosion, abrasion, or a “sandblasted” look, similar to the damage caused by hydraulic cavitation. Severe knocking can lead to catastrophic failure in the form of physical holes melted and pushed through the piston or cylinder head (i.e., rupture of the combustion chamber ),…

What is the difference between knocking and detonation in an engine?

This creates a typical noise, known as knocking. If knocking is severe enough, it may actually break engine parts. It should note as knocking and detonation are the synonymous terms, having the same meaning. Detonation is the name giving to the sudden and violent knocking occur inside the engine cylinder. Detonation is not pre-ignition.