What is combustion delay?

Abstract The ignition delay in a diesel engine is defined as the time interval between the start of injection and the start of combustion. This delay period consists of (a) physical delay, wherein atomisation, vaporization and mixing of air fuel occur and (b) of chemical delay attributed to pre-combustion reactions.

What causes ignition lag?

The longer ignition delay can be caused by a number of factors including: lower intake air temperature, lower boost pressure due to turbocharger lag, lower combustion chamber wall temperature and more advanced dynamic injection timing.

What is ignition lag and ignition delay?

Ignition lag or ignition delay as the name suggests is the time interval between the passage of spark and the ignition of the fuel-air mixture.

What is ignition lag Mcq?

6. What is Ignition lag? a) the time taken by fuel after injection to reach upto auto-ignition temperature. b) time before actual fuel injection and the pump plunger starts to pump fuel. c) time corresponding to actual injection and top dead center.

What are the four stages of combustion?

The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.

What are the stages of combustion?

Different significant phases of combustion are explained as under. 1) Ignition Delay Period • Physical delay • Chemical Delay 2) Uncontrolled Combustion 3) Controlled Combustion 4) After Burning Page 3 • Injection of fuel in atomized form is initiated into the combustion space containing compressed air.

Which is long ignition lag?

Heat release rate Second, the fuel that gets accumulated in the chamber during the time between fuel injection and the start of combustion undergoes rapid combustion and releases heat rapidly. Alcohol blends, having a longer ignition delay, result in higher HRR than diesel fuel.

What is the ignition lag in SI engine?

Ignition lag stage: An ignition lag of 0.002 seconds corresponds to 35 deg crank rotation when the engine is running at 3000 RPM. Angle of advance increase with the speed. This is a chemical process depending upon the nature of fuel, temperature and pressure, proportions of exhaust gas and rate of oxidation or burning.

What is scavenging air?

Scavenging is the process of replacing the exhaust gas in a cylinder of an internal combustion engine with the fresh air/fuel mixture (or fresh air, in the case of direct-injection engines) for the next cycle. Scavenging is equally important for both two-stroke and four-stroke engines.

What is cetane in diesel?

What is cetane? Simply put, cetane is a chemical compound found naturally in diesel, and it ignites easily under pressure. Because of its high flammability, it serves as the industry-standard measure for evaluating fuel combustion quality. Specifically, this measure is referred to as cetane number.

What is the hottest phase of fire?

Fully Developed
3) Fully Developed (Transition): As more fuel becomes consumed, the fire moves into a fully developed state. This is the most dangerous phase of a fire, and the hottest. At the peak of combustion, once all the material has been ignited, the fire begins its downward spiral.

What is the longest stage of fire?

A fire will enter its decay stage when the fire runs out of oxygen or fuel for it to sustain itself. This is the longest stage and can take weeks for larger fires such as wild fires. A burning tree stump can smolder for many weeks at a time, sustaining a fairly high level of heat.

When does ignition lag occur in an internal combustion engine?

In the internal combustion engine, the time interval between the passage of the spark and the inflammation of the air-fuel mixture. Also known as ignition delay.

What does lag mean in valve timing diagram?

This is known as valve lag. Valve lag – Inlet valve close after piston passed the BDC (at beginning of compression stroke), the exhaust close after piston passed TDC (at the beginning of suction stroke). Both were described as valve lag. ? Variable valve timing VVT of internal combustion engine – Advantages

What does lag mean in a compression stroke?

This is known as valve lag. Valve lag – Inlet valve close after piston passed the BDC (at beginning of compression stroke), the exhaust close after piston passed TDC (at the beginning of suction stroke). Both were described as valve lag.

When does abnormal combustion occur in an engine?

Abnormal combustion. When unburned fuel/air mixture beyond the boundary of the flame front is subjected to a combination of heat and pressure for a certain duration (beyond the delay period of the fuel used), detonation may occur.