Numerical Investigation on the Effect of Fuel Injection Location in a Multi-Swirl Lean Direct Injection Burner

The lean direct injection (LDI) concept can potentially replace the existing combustion systems for future aircraft engines because of its low NOx emissions without compromising other parameters. A novel multi-swirl LDI burner1 with distributed fuel injection surrounded by airflow through multiple hexagonal swirlers of vane angle 45° was developed. The flow dynamics and combustion characteristics of three different fuel injection LDI configurations were compared using a three-dimensional (3D) computational fluid dynamic (CFD) study. Realizable k-ε turbulence model with a scalable wall function was adopted to get the flow features, distribution of velocity, pressure, and turbulent kinetic energy in the swirl burner, and combustion was parameterized by using non-premixed steady diffusion flamelet model with a PDF approach. Results obtained in the numerical model for temperatures and mole fractions of CO2, O2, and mass fraction of NOx show a behavior similar to that of the experimental model. Four types of flow structures were present in the flow field, and interaction of these structures plays an essential role in rapid mixing and flame stabilization. The numerical results showed that the LDI-2A burner achieved better mixing and had a lower flame temperature than the other two burners, which would improve flame stability and reduce the NOx emission.