Table of Contents
What causes abnormal combustion?
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.
What is abnormal combustion in SI engines?
When the 2 conditions of normal combustion do not occur, the combustion process is abnormal, causing engine damages or simply performance worsening and noise. There are two forms of abnormal combustion in SI engines: 1)Surface ignition: combustion originates from some hot spots in the combustion chamber.
What are the reasons for incomplete combustion in SI engine?
Flame speed is reduced both for lean and as well as for very rich mixture. Lean mixture releases less heat resulting lower flame temperature and lower flame speed. Very rich mixture results incomplete combustion and also results in production of less heat and flame speed remains low.
What causes combustion in an engine?
In a spark ignition engine, the fuel is mixed with air and then inducted into the cylinder during the intake process. After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion. The expansion of the combustion gases pushes the piston during the power stroke.
What’s abnormal combustion?
The Abnormal Combustion:- ➢ When the combustion gets deviated from the normal behavior resulting loss of performance or damage to the engine. ➢It is happened when the charge inside the cylinder may be ignite before the flame front reach it.
What are the two types of abnormal combustion?
There are three forms of abnormal combustion: Detonation, Pre-Ignition and Detonation of fuel before Ignition or (Pre-Ignition due to Detonation). The process of burning the fuel in the combustion chamber has always been the most misunderstood concept by people who modify engines and tune engines.
What is abnormal combustion?
In Internal combustion engines, abnormal combustion is a significant phenomenon associated with the combustion processes on which the life and performance of the engine depends. The two important abnormal combustion phenomenons are 1. KNOCK and 2. SURFACE IGNITION.
Which among the following is not an abnormal combustion in SI engine?
Explanation: None. 10. Abnormal combustion knock produced by surface ignition in SI engines is not harmful as normal combustion knock.
Which factor in the design of combustion chamber to avoid detonation in SI engine is not applicable?
Q. | Which factor in the design of combustion chamber to avoid knocking and detonation in SI engine is not applicable |
---|---|
B. | exhaust valves away from end gas |
C. | cooling of exhaust valve |
D. | small bore |
Answer» a. long flame travel |
What is the difference between normal and abnormal combustion?
Normal combustion is the process where the fuel is burned layer by layer i.e. in a wave form by the help of spark only. And abnormal combustion is the process where the fuel burns not only by spark but also by self ignition process where a no. of waves of flames are produced from different parts of cylinder.
Which of the following is not a part of SI engine?
3. Which of the following does not relate to spark ignition engine? Explanation: Fuel injector is not related to spark ignition engine as there is no fuel injection in spark ignition engine.
Which of the following factors affect combustion in CI engine?
In CI engine, combustion occurs by the high temperature produced by the compression of the air. Explanation: None. 2. In the CI engine, the intake is air alone and the fuel is injected at high pressure in the form of fine droplets at the start of compression.
What is abnormal combustion in an engine?
When the 2 conditions of normal combustion do not occur, the combustion process is abnormal, causing engine damages or simply performance worsening and noise. There are two forms of abnormal combustion in SI engines: 1)Surface ignition: combustion originates from some hot spots in the combustion chamber.
How does a conventional SI engine work?
In a conventional SI engine, the fuel is completely vaporized and homogeneously premixed with air and residual gas, when combustion occurs. Under normal operating conditions, the mixture is ignited by the spark plug in a optimized moment of the cycle (usually 20-40° before TDC).
What is surface ignition in an engine?
Surface ignition is ignition of fuel air charge by overheated valves or spark plugs, by glowing combustion chamber deposits, or by any other hot spot in the engine combustion chamber. It is the initiation of flame front by a hot surface other than the spark plug. Mostly surface ignition is due to carbon deposits.
What causes a car to overheat before ignition?
The usual cause is an overheated spot, which may occur at spark plugs, combustion chamber deposits, or exhaust valves. Mostly it is due to spark plug. Exhaust valve usually run hot and sometimes when there is increase in heat load for these valves there will be an increase in the temperature and may cause pre ignition.
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