What are the Types of Combustion?
What are the Types of Combustion?
Combustion is the oxidation reaction of combustible elements or substances, which reflects the release of a large amount of heat by colleagues
There are two types of combustion: homogeneous combustion and heterogeneous combustion, depending on whether the reactants are in an interphase or not. The micro combustion of gaseous fuels is homogeneous, while liquid and solid fuels belong to heterogeneous combustion.
Homogeneous combustion can be divided into two basic processes: the diffusion process of mass exchange between fuel and oxidant molecules, and the process of mixture reaction. The former is a physical process, and the latter is a chemical process. If the physical process is long and the combustion time mainly depends on the diffusion time, this combustion is called “diffusion combustion”; on the contrary, if the combustion time mainly depends on the chemical reaction rate (chemical kinetics factor), then combustion is called “dynamic combustion”.
Under high temperature conditions of actual combustion, the rate of chemical reaction is very fast. If fuel and air are supplied separately and mixed and burned after entering the furnace, no matter how the mixing process is strengthened, the diffusion time is still much longer than the chemical reaction time, so combustion at this time belongs to diffusion combustion. If the diffusion time is zero, no matter how fast the chemical reaction progresses, it is also the main factor determining the combustion time, so the combustion at this time is dynamic combustion. However, it should be noted that power combustion is not only achievable in premixed situations. When fuel slowly oxidizes in the air, the reaction time is longer than the diffusion time, and the combustion at this time should be dynamic combustion. However, under high temperature conditions of actual combustion, power combustion requires pre mixing the fuel gas with all combustion supporting air to achieve this, which is commonly referred to as premixed combustion.
Industrial combustion is carried out under the condition of gas flow, and the combustion airflow is called a flame. According to the airflow state, flames can be divided into laminar flames and turbulent flames. As the second level characteristic, the flow state does not change the combustion type. Therefore, both diffusion combustion and premixed combustion can have two types of flames, respectively. Therefore, there are four types of flames: premixed laminar flame, premixed turbulent flame, laminar diffusion flame, and turbulent diffusion flame.