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 called knocking?
knocking, in an internal-combustion engine, sharp sounds caused by premature combustion of part of the compressed air-fuel mixture in the cylinder. In a properly functioning engine, the charge burns with the flame front progressing smoothly from the point of ignition across the combustion chamber.
What is knocking and anti knocking in chemistry?
Usually fuels (petrol) that have low octane numbers create a knocking sound. Octane number is the measure of the knocking resistance. To prevent these knocking sounds, anti – knocking agents are used. These are chemical compounds added in the fuels that help in effective combustion.
What is knocking simple?
1 : to strike something with a sharp blow. 2 : to collide with something. 3a : bustle heard them knocking around in the kitchen. b : wander knocked about Europe all summer.
What is cracking and knocking?
Example – Fluid cracking process to produce petrol and LPG. Knocking is associated with internal combustion engine that works on petrol and a mixture of gasoline vapors and air is used as a fuel. Knocking is a sharp, metallic sound produced due to ignition of air and gasoline mixture in the internal combustion engine.
What causes knocking?
Knocking happens when the fuel in the cylinder ignites before it should. This premature ignition disrupts the smooth rotation of the engine by firing before the piston reaches top dead center.
What are the effect of knocking?
What are the effects of knocking? vi) preignition. 8. Increase of pressure increases the self ignition temperature and the induction period.
What does have a knock mean?
idiom. to be damaged because of a bad experience: Her confidence took a hard knock when her application was rejected. Experiencing and suffering.
What is the difference between knock and Nock?
Well, nock is actually a common misspelling for knock (the silent k does a lot of people in). But the curious fact is that nock is a word in itself, and in general is used to refer to the notch at the end of the arrow into which the bowstring fits.
What are the types of knocking?
- Bad Belt Tensioners/Pulleys.
- Rod Knock: Worn Bearings.
- Detonation Knock: Bad Knock Sensor.
- Detonation Knock: Lean Air/Fuel Mixture.
- Detonation Knock: Bad Timing.
- Detonation Knock: Too Low Octane. First, we need to know what detonation knock is.
Which catalyst is used as knock inhibitor?
TEL act as a negative catalyst. It is an anti-knocking substance is added to petrol to decrease the ignition of petrol vapours.
What is anti-knocking compound give example?
An anti-knocking agent is the substance which is used to reduce the engine knocking. It increases the octane number of the fuel. It helps in auto-ignition by raising the temperature and pressure. TEL is tetraethyl Lead which is used as an Anti-Knocking compound.
What do you mean by knocking and compression ratio?
Higher compression ratios can make gasoline (petrol) engines subject to engine knocking (also known as “detonation”, “pre-ignition” or “pinging”) if lower octane-rated fuel is used. This can reduce efficiency or damage the engine if knock sensors are not present to modify the ignition timing.
What is hard knocking?
Definition of hard-knock : marked by difficult or painful experiences or circumstances For all of his gifts, Cabrera’s greatest strength may be a toughness that came from his hard-knock life.— Alan Shipnuck.
What is the effect of humidity on knocking?
Clearly, an increase in the water content in air substantially increases the Knock Limited Spark Timing (KLST), as is known in practice. From this we conclude that the presence of water vapor increases the resistance to knocking of the gaseous fuel/air mixture substantially.
What is knocking agent?
An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel’s octane rating by raising the temperature and pressure at which auto-ignition occurs.
What is a cracking reaction?
Cracking is a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated: the original starting hydrocarbons are alkanes. the products of cracking include alkanes and alkenes , members of a different homologous series.
What is cracking with example?
Cracking, as the name suggests, is a process in which large hydrocarbon molecules are broken down into smaller and more useful ones, for example: The cracking products, such as ethene, propene, buta-1,3-diene and C4 alkenes, are used to make many important chemicals.
What is knocking tendency of fuel?
Knock, in spark ignition engine is the combustion caused by the autoignition of the fuel-air mixture. It is the phenomenon that limits engine performance and thermal efficiency. Knock also has an adverse effect on emissions and fuel economy.
What causes knocking in petrol?
Knocking occurs when fuel burns unevenly in your engine’s cylinders. When cylinders have the correct balance of air and fuel, fuel will burn in small, regulated pockets instead of all at once. (Think sparklers, not fireworks.)
How do you stop knocking?
enriching the air–fuel ratio which alters the chemical reactions during combustion, reduces the combustion temperature and increases the margin to detonation. reducing peak cylinder pressure. decreasing the manifold pressure by reducing the throttle opening or boost pressure. reducing the load on the engine.
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 are effects of knocking Mcq?
The knocking tendency in compression ignition engines for a given fuel will be Enhanced by decreasing compression ratio. In SI engine, knocking tendency increases with increase in compression ratio. … In CI engine, knocking tendency decreases with increase in compression ratio.
What is the synonym of knock?
In this page you can discover 59 synonyms, antonyms, idiomatic expressions, and related words for knock, like: injury, rap, bang, bump, stroke, pick-apart, hurt, tap, beat, hit and beat.
What is a sentence of knock?
Knock sentence example. I better knock on his door. There was a soft knock at the door. A knock at the door interrupted their conversation.