Table of Contents
What causes detonation in SI engine?
In S.I. engines detonation is caused by the auto-ignition of end gas towards the end of combustion whereas knocking in CI engines is due to auto-ignition of the first charge at the start of combustion.
What Happens When detonation occurs?
When detonation happens, some of the air/fuel ignites before the normal burn can get to it. This causes a brief, but intense, spike in cylinder pressure. Detonation is also called an “Engine Knock”, “Knocking”, or “Pinging” because of the sound it makes.
How does SI engine separate detonation?
The detonation in an SI engine can be controlled by the following ways:
- Decreasing intake manifold pressure.
- Retarding spark timing.
- Reducing the compression ratio.
- Using the high octane fuel.
- Reducing the intake temperature of air.
- Reducing peak cylinder pressure.
- Reducing the engine size.
On what factors does the detonation depend?
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:
What is the definition of a detonation?
Definition of detonation 1 : the action or process of detonating. 2 : rapid combustion in an internal combustion engine that results in knocking.
What causes pre-ignition and detonation?
Pre-Ignition is defined as combustion that begins before it is intended to, before the regular timed spark. Pre-Ignition can occur alone or as a result of detonation. Hot spots from detonation, improper heat range spark plugs and glowing carbon deposits from lean mixtures are common causes of pre-ignition.
What is knocking and detonation and its causes?
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.
Which of the following defines detonation?
A detonation is a large or powerful explosion. Detonation is the action of causing a device such as a bomb to explode.
How is detonation initiated?
A detonation can be initiated directly e.g. by strong shock waves via a localized explosion where a large amount of energy was released. An interesting possibility of the detonation initiation in hydrogen-air caused by focusing of shock waves reflected inside a wedge was recently studied by Smirnov et al [5].
Which of the following factors increase detonation in the SI engine?
Knocking or detonation is due to the auto-ignition of the end portion of the unburned charge in the combustion chamber. Factors affecting knocking in SI engine: Compression ratio:- Higher compression ratio will result in the higher temperature of the charge, the tendency to knock will increase.
What is meant by detonation in IC 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 pre-ignition in SI engine?
Pre-ignition is a situation in which the fuel-air mixture in a spark ignition engine ignites before the timed spark, because of contact with a hot surface. Over-heated spark plugs and exhaust valves are the main causes of pre-ignition. Pre-ignition might be the consequence of the spark plug tip getting too hot.
What is a detonation knock?
What is explosion and detonation?
An explosion is a rapid expansion in volume associated with an extremely vigorous outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Supersonic explosions created by high explosives are known as detonations and travel through shock waves.
On what factor does detonation depend?
Mostly Detonation is occurred because of following reasons: Low Octane Fuel. High Compression engine. High Mileage engine.
Which of the following factors decrease the detonation in SI engine?
Use of low octane fuel can eliminate detonation.
Is detonation a combustion?
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.
What is detonation in IC engine?
Detonation is the abrupt combustion or explosion of the fuel charge inside the cylinder. During normal combustion, the spark plugs ignite the fuel charge and the fuel has a consistent and even burn as the piston moves through the power stroke and chemical energy is efficiently converted to mechanical.
What is detonation and what causes detonation?
By definition, detonation is when the flame fronts or propagation of a chemical reaction through the medium is faster than sonic velocities…causing unusually fast increases in temperature and pressure.
How does detonation affect the combustion cycle?
With detonation, almost all of the combustion happens right at TDC, greatly increasing the overall temperature and pressure inside the combustion chamber for a short time, putting greater cyclic stresses on all associated pressure boundaries, as well as exposing them to higher temperatures.
How does deflagration work in an SI engine?
During normal deflagration combustion, in an SI engine, there is a laminar and controlled oxidization of the charge, with a succinct flame front. (Combustion in a CI engine combustion is via a diffusion flame, which is another matter for another time).
What is the difference between knocking and detonation?
Knocking is also known as detonation, they are not different. Detonation is defined as a sudden explosive combustion process due to the burning of end-gas (An unburnt air-fuel mixture) that produces high-pressure waves and sound inside the cylinder. What causes detonation in engine?