Hi there, today I am going to discuss about Direct injection (DI) and Indirect injection (IDI) engines combustion chamber.
What is the combustion chamber?
The combustion chamber is a place, where the mixture of air and fuel burnt, produces heat.
And what is Injection?
Injection is a process, in which pressurized fuel is injected or sprayed on the high temperature and the high-pressure air at the end of the compression stroke.
And what is air swirl: air swirl is a controlled turbulence motion of air inside the cylinder and is useful for better ignition.
The design of CI engine combustion chambers is a very important and challenging task because the mixing of air and fuel takes place inside the cylinder in a very short period is about 250-350 crank angle at the end of the compression stroke.
The combustion chamber design plays a very important role in the proper mixing of fuel in this short period of time. The moment of air inside the cylinder during the injection of fuel is important to achieve proper mixing and better combustion of fuel within a shorter period. The moment of air is called “air swirl”.
There are three types of air swirl on the basis of how they are produced.
First is Induction swirl – it is achieved by directing the flow of air during its entry to the cylinder, known as induction swirl.
Different inlet manifold like deflector wall, helical wall ramp, masking on inlet valve, shrouding on inlet valve, etc. are used to generate swirl in the cylinder in suction stroke. By using the above systems Intake air tangentially enters into the cylinder.
Second is compressed swirl, in this system, an auxiliary chamber is used with the main chamber, during compression stroke; the air is forced to enter in auxiliary chamber tangentially to generate swirls motion. The auxiliary chambers known as swirl chambers.
The third is induced swirl, in an auxiliary chamber called pre-combustion chamber is used where swirl is induced by pre-combustion of fuel. Pre-combustion leads to pressure rise which rushes the gases in the main chamber for further combustion.
Next is injection systems, there are two types of injection systems are used in CI engines, first is direct injection second is indirect injection.
In Direct injection fuel is directly injected in the cylinder with high-pressure fuel jet, the jet pressure is sufficient to generate air swirl for mixing of air and fuel, and start the ignition. It is used in large cylinder engines where mixture requirements are least stringent. The shape of the combustion chamber is shallow in the piston crown. For small engines bowl in the chamber is used to achieve a fast mixing rate.
In an indirect injection system, fuel is injected in an auxiliary chamber instead of the main chamber, it is used in small automobile engines which requires a high rate of swirl motion for fast mixing of fuel and air.
High turbulent motion is generated by compression swirl or induced swirl in the pre-combustion chamber or divided chamber. The compressed air is forced from the main chamber to the auxiliary chamber, through the nozzle or orifice. The fuel is injected in a divided chamber at lower injection pressure than the DI engine. The ignition starts in the pre-chamber, pressure rises, and flame rushes to the main chamber through nozzle or orifice, and mix with the main chamber air.
The combustion chamber is a place, where the mixture of air and fuel burnt, produces heat.
And what is Injection?
Injection is a process, in which pressurized fuel is injected or sprayed on the high temperature and the high-pressure air at the end of the compression stroke.
And what is air swirl: air swirl is a controlled turbulence motion of air inside the cylinder and is useful for better ignition.
The design of CI engine combustion chambers is a very important and challenging task because the mixing of air and fuel takes place inside the cylinder in a very short period is about 250-350 crank angle at the end of the compression stroke.
The combustion chamber design plays a very important role in the proper mixing of fuel in this short period of time. The moment of air inside the cylinder during the injection of fuel is important to achieve proper mixing and better combustion of fuel within a shorter period. The moment of air is called “air swirl”.
There are three types of air swirl on the basis of how they are produced.
First is Induction swirl – it is achieved by directing the flow of air during its entry to the cylinder, known as induction swirl.
Different inlet manifold like deflector wall, helical wall ramp, masking on inlet valve, shrouding on inlet valve, etc. are used to generate swirl in the cylinder in suction stroke. By using the above systems Intake air tangentially enters into the cylinder.
Second is compressed swirl, in this system, an auxiliary chamber is used with the main chamber, during compression stroke; the air is forced to enter in auxiliary chamber tangentially to generate swirls motion. The auxiliary chambers known as swirl chambers.
The third is induced swirl, in an auxiliary chamber called pre-combustion chamber is used where swirl is induced by pre-combustion of fuel. Pre-combustion leads to pressure rise which rushes the gases in the main chamber for further combustion.
Next is injection systems, there are two types of injection systems are used in CI engines, first is direct injection second is indirect injection.
In Direct injection fuel is directly injected in the cylinder with high-pressure fuel jet, the jet pressure is sufficient to generate air swirl for mixing of air and fuel, and start the ignition. It is used in large cylinder engines where mixture requirements are least stringent. The shape of the combustion chamber is shallow in the piston crown. For small engines bowl in the chamber is used to achieve a fast mixing rate.
In an indirect injection system, fuel is injected in an auxiliary chamber instead of the main chamber, it is used in small automobile engines which requires a high rate of swirl motion for fast mixing of fuel and air.
High turbulent motion is generated by compression swirl or induced swirl in the pre-combustion chamber or divided chamber. The compressed air is forced from the main chamber to the auxiliary chamber, through the nozzle or orifice. The fuel is injected in a divided chamber at lower injection pressure than the DI engine. The ignition starts in the pre-chamber, pressure rises, and flame rushes to the main chamber through nozzle or orifice, and mix with the main chamber air.
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