Quick Answer: What is normal combustion in SI engine?

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 the normal combustion and abnormal combustion in SI engine?

Normal combustion spark-ignited flame moves steadily across the combustion chamber until the charge is fully consumed. Abnormal combustion fuel composition, engine design and operating parameters, combustion chamber deposits may prevent occuring of the normal combustion process.

What is abnormal combustion in SI engine?

But in this downsized engine, abnormal combustion, which occurs under the condition of low speed and high intake pressure, is a serious problem. It has been referred to as Super Knock, Mega Knock or Low Speed Pre-Ignition (LSPI). In this paper, we use the term Super Knock.

What is normal combustion?

In normal combustion, the piston is on its way up the cylinder toward Top Dead Center. It’s compressing a mixture of fuel and air above it. At a point, before TDC, a spark passes across the gap of the spark plug electrodes and that sets the mixture to burning, creating a tiny flame kernel.

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What is normal combustion in CI engine?

Combustion in a spark ignition engine is termed normal if it is initiated by a timed spark plug and the air-fuel mixture (charge) is consumed solely by the propagating flame front which originated from the discharged spark and completely moves across the combustion chamber.

What is meant by SI engine?

A spark-ignition engine (SI engine) is an internal combustion engine, generally a petrol engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug.

How knocking can be reduced?

Because pressure and temperature are strongly linked, knock can also be attenuated by controlling peak combustion chamber temperatures by compression ratio reduction, exhaust gas recirculation, appropriate calibration of the engine’s ignition timing schedule, and careful design of the engine’s combustion chambers and …

What is delay period in SI engine?

Explanation: Delay period is defined as the time immediately following injection of the fuel during which the ignition process is being initiated and the pressure does not rise beyond the value it would have due to compression of air.

What is flame speed in SI engine?

The flame speed is the measured rate of expansion of the flame front in a combustion reaction. The flame is generally propagated spherically and the radial flame propagation velocity is defined as the flame speed. … Flame speed is typically measured in m/s, cm/s, etc.

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.

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What is knocking in fuel?

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. … Engine knocking happens when fuel burns unevenly and those shocks go off at the wrong time.

Which cycle is more efficient?

Explanation: Otto cycle is more efficient than Diesel cycle for a given compression ratio. 6. For constant maximum pressure and heat input, the air standard efficiency of the gas power cycle is in the order.

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