Back to the Basics: 5 Important Classifications of Combustion

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Combustion is a technical term for burning, which is a chemical process that occurs when a fuel reacts with an oxidant to produce heat. Some common examples of combustion include burning wood to heat a home, the burning of petrol to run a car and the combustion of natural gas to cook on a stovetop.

The process of combustion can be broken down into different classifications based on the energy it needs to occur and the byproducts of the reaction. Here’s a closer look at five types of combustion:

1. Complete Combustion

Complete combustion requires a combination of fuel and oxygen. During the combustion process, the reactant is completely burned in oxygen, leaving a limited amount of byproduct. When a hydrocarbon is burned in oxygen, the reaction will usually lead to the production of carbon dioxide and water. 

When other elements are burned, they typically leave commonly known oxides leftover. For example, carbon will produce carbon dioxide, nitrogen leads to nitrogen dioxide and sulfur will yield sulfur dioxide

2. Incomplete Combustion

Incomplete combustion occurs when there is not enough oxygen for the fuel to fully react. In this case, the byproducts, carbon dioxide and water, are not produced. Instead, the reaction will leave behind carbon monoxide and soot. Incomplete combustion also produces less energy than complete combustion, making it less efficient overall. 

3. Rapid Combustion

When rapid energy requires external heat energy for a reaction to occur, it is classified as rapid combustion. This reaction will continue to remain live until all of the fuel is burned up. As a byproduct, this form of combustion produces large amounts of heat and light energy at a rapid pace. 

One common example of this occurs when you light a candle. The combustion reaction takes place when a flame ignites the wick, producing a constant light that doesn’t stop until all of the wax has been burned through. 

4. Spontaneous Combustion

Spontaneous combustion received its name because no outside energy is required for the reaction to begin. It occurs spontaneously. During spontaneous combustion, an increase in temperature due to an internal reaction, followed by thermal runaway and the presence of sufficient oxygen will start the process. Once the fuel reaches a temperature that is high enough, it will ignite all on its own. For example, phosphorus will self-ignite at room temperature without any application of heat. 

5. Explosive Combustion

Explosive combustion is exactly what you would expect; an explosion. This type of combustion occurs at an extremely rapid pace. When a force is used to ignite the fuel, heat, light and sound energy are produced immediately. One common example of this can be seen in fireworks. When a spark lights the fuse, the fireworks explode, causing heat, light and sound. 


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