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What Is Preignition - Causes and Disadvantages of Preignition

What is preignition? Preignition is a phenomenon in the IC engine in which homogeneous fuel charge burned before the normal ignition starts ...

What Is Preignition - Causes and Disadvantages of Preignition


What is preignition?

Preignition is a phenomenon in the IC engine in which homogeneous fuel charge burned before the normal ignition starts (or in the absence of spark). The preignition is initiated by the overheated projecting parts such as spark plug, exhaust valve head, carbonaceous deposits and hot spot in the combustion chamber. The autoignition (or knocking) may overheat spark plug, valve head and it remains so hot that it may ignite the fuel charge in compression stroke of the next cycle.

Difference Between Knocking and Detonation? Theories of Knocking

Detonation

 

What is the difference between knocking and detonation?

“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. 1) auto-ignition theory and 2) detonation theory. These theories led many people to use the term detonation for knocking. In general, detonation is the cause and knocking is the after effect.

What Are the Various Factors Influencing Flame Propagation?

Flame speed

 

Abnormality in SI engine like detonation is depends on the rate of pressure rise in the combustion chamber. Since the rate of pressure rise directly related to the rate of flame propagation, it is very important to study about the factors affecting flame propagation. Important factors that influence the flame propagation is listed below.

 

Flame Propagation and Flame Speed Across the Combustion Chamber and Factors Affecting Flame Propagation

Flame propagation in SI engine

Flame propagation and flame speed

Flame propagation is defined as the progress (spread) of the flame inside the engine cylinder (combustible environment) outward from the point at which the combustion started. Flame generally propagates spherically. The rate of radial propagation of flame is known as flame speed. It is typically measured in m/s. It gives an idea about how rapidly fame propagates from a reference point. The flame speed determines the ability of a fuel to undergo controlled combustion without detonation.

What is Sintering? Applications, Advantages and Disadvantages of Sintering

metal_piece

What is sintering?

Sintering is a thermal treatment technique of compacting and forming of solid material using heat and pressure without melting the main constituent (or without heating it to its liquefaction temperature). It is basically atomic diffusion. It will happen in any material at any temperature above absolute zero, but it is faster in higher temperature. When the heat is applied to powder compact, the average grain size increases, reducing the porosity and the compact gets densified. This basic phenomenon is known as sintering.

Electron Beam Machining EBM Applications, Advantages and Disadvantages

EBM applications advantages

🔗EBM operating principle and working

EBM applications

EBM now found application in many industrial equipments. Special characteristics of EBM, such as high-resolution long depth of field, make them suited for specific application. Other special characterises are their extraordinary high energy, controllability and compatibility with high vacuum. It also has the ability to catalyse many chemical reactions. EBM is used to cut and hole making on thin material. Hole drilling is the main application of EBM (e.g. wire drawing dies, making of the fine gas orifice). It can cut thin hole and slots in metals, plastics and ceramics of any hardness. It finds application in food, chemical, aerospace, textile, and automobile industries.
 
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