What is the turbulent diffusion combustion process of gas fuel jet
Due to the intense disturbance caused by turbulence in the airflow, its diffusion rate greatly increases and can achieve much higher intensity than laminar diffusion combustion. Therefore, the most widely used diffusion combustion in industry is turbulent diffusion combustion.
Whether the gas and air flowing out of the coaxial sleeve can undergo turbulent combustion depends on their speed and the speed difference between the two. The mixing of coaxial jets is also closely related to the velocity difference between the central airflow and the peripheral airflow.
The turbulent combustion of gas fuel can be achieved by increasing the gas flow rate or adopting artificial reinforcement measures. According to the different methods of causing turbulence, turbulent diffusion combustion can be divided into two types: free turbulent diffusion combustion and forced turbulent diffusion combustion. The former is based on free jet, while the latter is achieved through methods such as cross jet and rotating jet.
The flow state of spraying one medium from the nozzle into another stationary medium is called a free jet. When the gas flows freely from a smaller nozzle to static air, the flow rate changes from low to high, and the process and characteristics of the flame transition from laminar diffusion combustion to turbulent diffusion combustion can be observed.
If combustible gas (fuel) and air are transported separately, but the rate of transporting air is very small, it can be considered that combustible gas is sent into a space filled with static air. In this way, the velocity of combustible gas flowing out of the injector will determine the flow state of the airflow. If the airflow velocity is large enough to be in a turbulent state, then this turbulence becomes a freely sinking jet. After the jet flows from the outlet of the burner, it entrains air from the surrounding space during turbulent diffusion. As a result, the mass of the airflow continuously increases, the width of the jet also expands, and the airflow velocity decreases and gradually becomes uniform. At the same time, various mixtures of different concentrations are formed under the jet width.