What is knocking in petrol and diesel engine?

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 is knocking in diesel engine?

It is the high pressure-rise rates associated with the auto-ignition of fuel during the premixed combustion stage that produces the characteristic “knocking” noise widely associated with diesel engines. This noise is often referred to as diesel knock [1] or combustion roughness [2].

What is knocking in petrol engine?

knocking, in an internal-combustion engine, sharp sounds caused by premature combustion of part of the compressed air-fuel mixture in the cylinder. Knocking can cause overheating of the spark-plug points, erosion of the combustion chamber surface, and rough, inefficient operation.

What causes detonation in a petrol engine?

Answer: Detonation, or engine knock, occurs simply when fuel pre-ignites before the piston reaches scheduled spark ignition. Detonation is generally caused by excessive heat, excessive cylinder pressure, improper ignition timing, inadequate fuel octane or a combination of these.

What is 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 are the effect of knocking?

Explanation: The effects of knocking are. i) noise and roughness. ii) mechanical damage. iii) carbon deposits. iv) increase in heat transfer.

What causes diesel knocking?

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. The telltale sound of an operating diesel engine is due in part to the fuel injection process.

What is knocking tendency?

When the spark is advanced, burning gas is compressed by the rising piston and therefore temperature and pressure are increased, thus, the tendency to knock increases. In SI engine, knocking occurs before TDC and because of early combustion of charge/more than one flame propagation.

What is detonation explain in detail?

Detonation (from Latin detonare ‘to thunder down/forth’) is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it.

How is knocking produced in a petrol engine Mcq?

Explanation: In the mixture of air and petrol vapour, there occurs a condition when the rate of oxidation increases to such a value that it starts producing sound in the engine which are called a knock. This decreases the octane rating of gasoline.

What is a diesel knock explain how it affects engine performance?

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 detdetonation or knocking?

Detonation or knocking is one of the most frequent problems in engine. Knocking in an engine is due to detonation. It is the abnormally high pressure situation which is more than the maximum pressure occuring with wrong timing(earlier or later than the required timing) It is due to accumulation of fuel and inefficient combustion.

Why do diesel engines knock when starting up?

Also such engines were sensitive to ignition advance and had less power. Knocking is more or less unavoidable in diesel engines, where fuel is injected into highly compressed air towards the end of the compression stroke. There is a short lag between the fuel being injected and combustion starting.

What is the difference between knocking and detonation in IC engines?

“Knocking” and “detonation” are the interchangeable terms refers to the phenomenon of uncontrolled combustion in the IC engine. “Knock” is the sharp metal pinging sound produced in the engine due to uneven combustion. There are generally two theories for knocking.

What is detonation in engines?

Detonation is the process of pre-ignition or auto-ignition of a fuel in an engine’s combustion chamber. This is often occurred due to use of fuel with low octane rating. This means that the fuel starts to burn before the spark plug fire and electric current. Detonation is characterized by an instantaneous, explosive ignition.