Performance evaluation methods of two-stage axial swirler:Ⅰ influence of total swirling intensity

Theoretical and numerical studies on the reaction flow field and combustion performance of two-stage axial swirler combustors were carried out. A performance evaluation method of multi-stage swirlers was developed. In addition, the total swirl intensity and energy utilization efficiency were put forward to evaluate the swirler performance. It was found that the total swirl intensity and flow resistance coefficient were the main influential factors to the swirler energy utilization efficiency. The interaction between the two stage swirlers was investigated numerically. And the results indicate that the inner swirl intensity has a greater impact on the width of central toroidal recirculation zone (CTRZ). The total swirl intensity plays a most important effect on combustor overall performance. When the total swirl intensity is less than 0.43, weak swirling flows will be produced; when the total swirl intensity is between 0.43 and 0.6, medium strength swirling flows will be produced and weak CTRZs are presented; when the total swirl intensity is more than 0.6, strong swirling flows will be produced and moderate CTRZs are presented at the same time; when the total swirl intensity is more than 1.03, very strong swirling flows will be generated. If the total swirl intensity is constant, a two-stage axial swirler will get better energy utilization efficiency than a single stage axial swirler. The results by the evaluation method are compared with the experimental and numerical results. Its found that the evaluation method for multi-stage axial swirler performance can accurately evaluate the performance of swirlers, providing a practical and effective method for the design of multi-stage swirlers in the future.