What is detonation and knocking in SI engine?

What is detonation and knocking in SI engine?

“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. In general, detonation is the cause and knocking is the after effect.

What is knocking in SI engine Explain with diagram?

knocking, in an internal-combustion engine, sharp sounds caused by premature combustion of part of the compressed air-fuel mixture in the cylinder. These pressure waves force parts of the engine to vibrate, which produces an audible knock.

What is detonation tendency?

Detonation — generally caused by fuel with a low octane rating — is the tendency for the fuel to pre-ignite or auto-ignite in an engine’s combustion chamber. The effects of detonation may be anywhere from arbitrary to severe.

What are the differences between detonation knocking and preignition?

Detonation is an uncontrolled combustion event which occurs after the spark event. Pre-ignition is an uncontrolled combustion event which occurs before the spark event. Knock (pinging) is the actual noise that can be audibly heard if detonation is bad enough.

How does SI engine reduce detonation?

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 causes detonation in an aircraft engine?

Detonation – Detonation, as the name suggests, is an explosion of the fuel-air mixture inside the cylinder. Other causes of detonation are improper ignition timing, high inlet air temperature, engine overheating, oil in the combustion chamber, or a carbon build up in the combustion chamber.

What is difference between explosion and detonation?

Discovered in 1881 by French scientists, detonation is the result of a supersonic wave initiating a secondary explosion. Explosion, on the other hand, is a general term for an accelerated release of energy generating extreme temperatures, releasing of gases and expanding volume.

What is the difference between combustion and detonation?

Detonation differs from normal combustion in its ignition mechanism and in the supersonic velocity of 2–5 kilometres per second for gases and 8–9 kilometres per second for solid and liquid explosives. Detonation is impossible when the energy loss from the reaction zone exceeds a certain limit.

In which engine detonation occurs in the beginning of combustion?

Solution: -In compression ignition engines, detonation occurs near the beginning of combustion. -Since the fuel, in compression ignition engines, is injected at the end of compression stroke, therefore, there will be no pre-ignition.

What is detonation in a 2 stroke?

Detonation is one cause of two stroke aircraft engine failure. In a normal combustion process the fuel-air mixture is ignited at a specific point before the piston has reached top dead center on the compression stroke. As the fuel is ignited it propagates a flame from the original spark.

Is detonation and knocking same?

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 is a detonation wave?

A detonation is a supersonic combustion wave that consists of a shock wave driven by energy release from closely coupled chemical reactions. These waves travel at many times the speed of sound, often reaching speeds of Mach 5, as in the case of a hydrogen–air fuel mixture.

Why is detonation called detonation in SI engines?

In SI engine, the charge that autoignites is homogeneous and therefore intensity of knocking or the rate of pressure rise at explosive autoignition is likely to be more than that in CI engines where the fuel and air are not homogeneously mixed even when explosive autoignition of charge occurs. Therefore, it is often called detonation in SI engines.

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

Compared to SI engines knocking in CI engines have less occurrence. This is due to time delay or ignition delay. Detonation is a kind of knocking. Generally, it is an abnormal combustion in SI and CI engines. But, this is a very important phenomenon which occurs in both Spark Engines (SI) and Compression Ignition Engines (CI).

What happens when you detonate a car engine?

An engine is designed to work in a specific way. Because detonation interrupts that design, it robs the engine of power. Most engines can handle some minor detonation. Modern, fuel injected engines can sense a knock and adjust the Air/Fuel Ratio and Ignition Timing.

What is detdetonation and how is it indicated?

Detonation is also called an “Engine Knock”, “Knocking”, or “Pinging” because of the sound it makes. How is it indicated? Drop in Exhaust Gas Temperature (EGT)