Comparison of Flow and Mixing in a Gas-fired Furnace in Tangential and Opposed Injection Modes

In diffusion combustion systems, fuel and oxidizer are admitted into the furnace in separate streams. In these systems, turbulent mixing of the oxidant (usually air) with fuel is typically the rate-limiting step of the combustion process. Making any changes to the injection system to enhance the mixing process can help to tailor the performance of the flame. So far researchers have developed and assessed a vast array of injectiontypologies to enhance the mixture formation. In the present study, two different injection modes, namely, tangential and opposed injection modes are compared to find out their effects on flow and mixing in a gas-fired furnace with square horizontal cross-section. The study is performed numerically, under isothermal conditions. A turbulent round jet injected into cross flow is simulated to verify the simulation methodology and thesolution algorithm. The calculated jet trajectory and velocity profile are compared with the experimental and numerical data of existing references and good agreement is observed. Unmixedness index is defined and used to judge the performance of the injection system. Results show that tangential injection can improve the mixing process considerably compared to opposed injection.

Keywords:

Injection typology , turbulent mixing , diffusion combustion , CFD