If the Ignition in Internal Combustion Engine takes place at the end of the Compression Stroke then the engine runs without knocks, with good efficiency.
The Compression Ignition Engine is so designed that the temperature at the end of the Compression is above the self-ignition Temperature of Fuel.
In this case (ignition system), no spark plug as like in Spark Ignition is required for Ignition.
So, here are the Details of Different Ignition Systems
Hot Tube Ignition Systems
This is the old method which was used in old days, now this method has become obsolete. But to gain some information, here I disclose the description.
In this method used in Gas and Light Oil Engines, a porcelain or metal tube closed with one end is heated red hot from an external source, to a Temperature well above the Ignition Temperature of the Fuel so that when the latter is injected into the tube it immediately ignites.
The tube is heated in the middle, through a Timing Valve.
The hot tube communicates alternatively with the Cylinder when Ignition takes place and with the Atmosphere during expansion.
In some Gas Engines, this Timing Valve has been dispensed with and the ignition tube is in free communication with the Cylinder throughout, the instant of firing being determined by Compression of some of the Explosive Mixture into the tube.
As the Engine starts the heat of the tube from the previous explosion is sufficient to ignite the fuel in the next cycle.
Spark Ignition Systems
This method is mostly used on Engines working on the “Otto Cycle”. And consists in ignite the Fuel by producing a high tension Electric Spark.
The Engines which are using this type of Ignition method are called “Spark Ignition Engines”.
In which one Spark must be produced at each cylinder at the correct moment.
Hot Combustion Chamber Ignition Systems
Another name for this method is “Surface Ignition or Hot Surface Ignition”. This method is used in Engines working on the “Dual Combustion Cycle”.
The bulb which is located at the compression end of the Engine Cylinder and connected by a narrow space or throat to the combustion space of the cylinder is jacketed and initially heated from an external source, like a Lamp.
At the end of the Compression Stroke, the Fuel injected comes in contact with the red-hot bulb and thus the ignition commences.
Once the Engine starts the heat retained from the previous explosion is sufficient to ignite the fuel in the next cycle.
This method is used in heavy oil engines working on a Constant Pressure Cycle (Diesel Cycle).
The Air is compressed to such a high pressure that its Temperature is higher than that at which the fuel burns.
The Fuel is then injected into this hot compressed air where its ignition starts spontaneously.
In Hot Tube Ignition and Hot Combustion Chamber Ignition, the exact point of the cycle at which ignition commences is quite uncertain.
This problem does not occur in the Compression Ignition system.
I hope the information above will help you to understand the ignition systems of the engines.
Besides this information, you are suggested to read something more from below engineering books
To get the more details about the topic, I further recommended reading
- Internal Combustion Engines
- Internal Combustion Engine Fundamentals
- Engineering Fundamentals of the Internal
- A Textbook of Internal Combustion Engines
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