What is Combustion Chamber? | How does a Combustion Chamber work?

An engine is a most important part of the vehicle. An engine consists of a combustion chamber, carburetor, piston, and fuel pump. The combustor chamber is a part of the IC engine in which the air-fuel mixture burns at a constant temperature, and in a gas turbine, this combusted air-fuel mixture expands to produce electricity. This article mainly explains the types, working, and applications of the combustion chamber.

What is a Combustion Chamber?

A combustion chamber is a part of the internal combustion engine in which the combustion of the air-fuel mixture takes place. This is an enclosed cylinder. A combustion chamber is also known as a combustor.

The combustion chamber of the reciprocating engine has a piston. This piston reciprocates inside the chamber to compress the air-fuel mixture. 

As the mixture is compressed, a spark plug (in an SI engine) generates a spark and ignites the compressed air-fuel mixture. The air-fuel mixture ignition process inside the combustion chamber highly increases the chamber’s inner temperature and pressure. After the ignition process, the piston expels the combusted mixture out of the chamber.

The IC engine combustion cylinder contains many parts such as a fuel pump, fuel nozzles, spark plug, and piston.

The combustion chambers are most commonly used in the engines of cars, ships, airplanes, buses, trucks, and many other vehicles. If you have an automobile or car, you can easily find it there.

Working of Combustion Chamber

The combustion chamber is one of the most important parts of the engine. The main function of the combustion chamber is to burn the air-fuel mixture and generate high pressure and temperature gases.

combustion chamber working

A combustion chamber works in the following way:

  1. Firstly, the carburetor sucks air from the environment, mixes it with fuel, and delivers this mixture to the engine combustion chamber.
  2. The chamber has a reciprocating piston.
  3. As the air-fuel mixture enters the chamber, the piston compresses it.
  4. At the end of the compression process, a spark plug ignites the mixture.
  5. The combusted air-fuel mixture generates high-pressure and high-temperature gases inside the chamber.
  6. As the combustion process completes, the piston expels the high-pressure mixture out of the chamber and introduces it into an expansion valve where it expands.
  7. When the high-pressure mixture expands, it exerts a force on the top of the piston and reciprocates it.
  8. As the piston receives pressure energy from the combusted mixture, it converts this energy into mechanical energy (reciprocating motion). A connecting rod connects to the piston. As the piston transfers its motion to the connecting rod, the rod coverts reciprocating motion into rotary motion.
  9. The connecting rod delivers its rotary motion to the crankshaft.
  10. When the crankshaft receives motion, it turns the flywheel, further turning the vehicle tire.

Types of Combustion Chambers

The combustion chamber has the following major types:

  1. According to the fuel type or combustion cycle
  2. According to the

1) According to the Combustion Cycle

i) Combustion chamber in SI Engine

The combustion chamber of the petrol or SI engine has an easy design than the diesel engine chamber. In this engine, a carburetor uses to mix the air and fuel out of the chamber.

When the air and fuel mixture is mixed, it transfers into the combustion chamber for the combustion process. This engine has a spark plug at the top of the combustion chamber. When the fuel-air mixture is compressed, the spark plug produces a spark that starts the combustion of the mixture.

The SI engine combustor has the following functions:

  1. It helps to generate the highest engine power. 
  2. The combustor lowers the maintenance needs of the engine
  3. It achieves high thermal efficiency.
  4. It ensures a smooth operation of the engine. 
  5. Extends engine service life.
  6. It helps to stop detonation or to knock.

Read More: Different types of SI Engines

2) Combustion Chamber in CI Engine

The diesel engine has no carburetor. Therefore, the mixing of the air and fuel occurs inside the combustion chamber. The diesel engine combustor has no spark plug. In this chamber, the combustion of the air-fuel mixture occurs due to the high compression of the air.

The design of the diesel engine chamber is more complex than the petrol engine chamber. The working of the diesel engine is totally different than the SI engine.

The diesel engine combustion chamber has the following major function:

  • In the diesel engine, only air is present during suction and compression strokes while fuel is injected at the end of the compression stroke.
  • The diesel chamber takes a very short time to mix the fuel and air.
  • Air swirls play a vital function for better mixing and better combustion during the combustion process. Swirl is a variety of air transfer methods used to properly mix air and fuel in the combustion chamber.
  • The combustor’s proper working is very important for efficient combustion, atomization, vaporization, and proper mixing with air. It completes all these steps faster than the SI engine chamber.
  • It provides increased power, less lag time, quieter engine operation, smooth operation, better engine efficiency, and reduces the chance of detonation.

Read More: Working and types of Diesel Engines

Types of Combustion Chamber for Diesel Engine

  1. Energy cell combustor
  2. Open combustor
  3. Pre-combustion chamber
  4. Squish combustor
  5. Swirl combustor
  6. Air cell and energy-cell

1) Open Combustion Chambers

These types of combustion chambers are most commonly used in high and medium-speed engines.   

This chamber has a fuel injector installed at the center of the cylinder head so that it can easily inject fuel into the chamber. The Leyland Bus engine uses this combustor.

Advantages and Disadvantages of Open Combustion Chambers
This combustor has maximum thermal efficiency due to minimum heat transfer losses.The engine having these chambers have a large size.
The engine having these combustion chambers are easy to start.This chamber requires high pressure and a nozzle with multiple holes.
They have a simple design.It has a high maintenance cost.

2) Pre-Combustion Chamber

These chambers are commonly employed in high-speed engines. These engines have two chambers:

  1. Auxiliary combustion chamber (pre-combustion chamber)
  2. Main combustion chamber

The auxiliary combustion chambers have a small size than the main combustion chambers.

The pre-combustion chamber burns the fuel partially. This partially combusted fuel enters the main combustion chamber through a small hole, where fuel is burnt completely. The pre-ignition chamber assists in fully igniting the fuel.

Advantages and Disadvantages of Pre-combustor
These types of combustion chambers have the capability to use fuel with high cetane number.The construction of the engine becomes complicated because of the pre-combustion chamber.
The fuel injection nozzle of these combustors has a simple design.The pre-combustion chamber engines have low thermal efficiency.
The engine having this combustion chamber generates a small knocking and high compression ratio.They have high fuel consumption.
The engines have a smooth operation.It has significantly high heat loss.
These engines can run at very high speed.The engine has a difficult cold starting.

3) Swirl Chamber

A swirl chamber is also called a turbulence chamber. A swirl is a rotary motion imparted to the flowing air during the suction process.

In this chamber, a swirl provides to the air as it enters the combustor. Fuel is injected into this swirling air. This swirling air completely mixes with the fuel and burns completely.

Advantages and Disadvantages of Swirl Combustor
They can use a high cetane number fuel.These combustors also have high losses.
These chambers use a simple nozzle because the pattern of injection and injection pressure is not compulsory due to swirl.The engine has low thermal efficiency.
The engine requires low maintenance.Difficult start of a cold engine.
The engine has smooth operation.High fuel consumption.
The swirl combustion chamber engines can run at high speed because they have a very small delay period. 
There are very low chances of knocking. 

4) Squish Combustion Chamber

This chamber has a squish air flow. This air flows from the periphery of the cylinder towards the chamber center. A slot is made inside the piston head to create a sizzling combustion chamber.

During the compression stroke, the piston of this chamber squeezes the air from its periphery to its center. This action creates vortices in the air. A fuel pump injects fuel into the center of the chamber.

5) Air Cell Combustor

It is a small combustion chamber. It connects to the main combustion chamber by air through a slim passage. The cell air chamber compresses air in the air cell during the compression stroke. 

As the fuel pump injects fuel into the chamber, the fuel burns and the piston travels from TDC to BDC. During this motion of the piston, the hot compressed air from the air cell enters the main chamber, generates swirling air, and completes the combustion process. 

These combustors are mainly employed in high-speed engines. These chambers also require a heater plug to heat up the compressed air. The air cell combustor engine has a high compression ratio. Due to the larger cylinder surface with air cells, they have a high heat loss rate.

Advantages and Disadvantages of Air Cell Combustion Chamber
The engines having these combustors have an easy cold start.They have high fuel consumption.
It has a low rate of exhaust emission.The air cell combustion chambers are not best suitable for variable speed engines.
It provides excellent fuel and air mixing that improves the burning process.They have low thermal efficiency.
These engines have a smooth operation because of the low rise of maximum pressure. 

6) Lanova Combustor

The Lanova combustor is also referred to as an energy cell combustor. It works on the air cell and pre-combustion chamber principle.  

The energy cell connects to the main combustion chamber by a narrow duct. It has a minor cell and a major cell. A narrow opening uses to connect these cells. A plunger uses to close the opening.  

At the engine starting time, the narrow opening remains shut, which rises the combustion chamber capacity. When you turn on the engine, the narrow opening opens and links the minor cell with the major cell. As the fuel injects into the main combustor, a small portion (about 10%) of fuel also enters the energy cell.

In these chambers, the fuel combustion process firstly occurs in the main combustion chamber and then diffuses into the power cells where pressure builds. A pressure difference generates when the piston goes from the TDC to BDC because the high-pressure air-fuel mixture moves from the power cell to the main combustion. This process creates turbulence flow of air, and complete combustion takes place.

FAQ Section

What are the types of Combustion Chambers?

The combustion chambers have the following major types:

  1. Air cell and energy-cell
  2. Swirl combustor
  3. Energy cell combustor
  4. Open combustor
  5. Squish combustor
  6. Pre-combustion chamber

What are the parts of the combustion chamber?

The combustion chamber has the following major parts:

  1. Piston walls
  2. Cylinder liners
  3. Cylinder heads
  4. Exhaust port walls
  5. Crowns of piston
  6. Sealing ring
  7. Flare
  8. Fuel spray nozzle
  9. Primary zone

What is a Combustion Chamber used for?

A combustion chamber is a place where the combustion of the air-fuel mixture takes place. Its main function is to burn the air-fuel mixture and prevents the generated heat from escaping. This output heat generates a thrust which moves the piston. As the piston moves, it further moves the crankshaft which turns the vehicle wheels.

Read More
  1. Types of Engines
  2. Types of IC Engines
  3. Working and types of Petrol Engine
  4. Working and types of Diesel Engine
  5. Function of Piston

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