Turbulent flow simulation behind a V-shaped flame stabilizer using a nonlinear K-ε model and a smoothing algorithm

摘要

The two-dimensional turbulent recirculating flow field behind a V-shaped bluff body has been investigated numerically. Similar bluff bodies are sued in combustion chambers for flame stabilization. The study helps to gain understanding of the mechanism of the flame stability and major factors that affect this stability. Both standard and a nonlinear version of the k-ε turbulence closure model are sued in the computation. Modification has been made to the nonlinear model to take into consideration of low Reynolds number effects in the near wall regions. A new localized smoothing filter based on the least squares technique is used The new smoothing filter effectively eliminated numerical fluctuations due to the nonlinearity of the turbulence model and the higher order approximation. The code is validated against available experimental data. Parametric investigation of the flow field by varying the shape and size of the bluff body is performed. It has been found that the axial distributions of normalized reverse mass flow rate for different configurations are similar. The maximum reverse mass flow rate increases monotonically with the base height as well as with the included angle of the bluff body, but normalized axial location of the maximum reverse mass flow rate remains unchanged. Similarly, although the recirculating bubble length increases linearly as the base height or included angle is increased, the normalized separation bubble length is almost the same for all cases.