422 / 2018-12-27 13:37:07

Influence of swirler type and mixing zone shape on burner performance analysis

double swirler; DoE; mixing zone shape; center recirculation zone; flashback

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There are two main design targets for partially premix burner, one is to stabilize flame, and the other one is to enhance mixing to reduce flame front local temperature, thus lower the thermo-NOx. One method to stabilize flame is to use recirculation zone which might be produced by swirl flow. In order to analysis the performance of different swirler type, three different swirler types were chosen, single swirler, double swirler same direction and double swirler counter direction. Based on the iso-thermal RANS result, the double swirler with same direction was chosen for further study. DoE is used to analysis the influences from different geometrical parameters:
1, Inner layer swirl number.
2, Outer layer swirl number.
3, Nozzle diameter.
4, Air ratio between outer layer and inner layer.
The optimal parameters of double swirler same direction were obtained. After the investigation of swirl, three different mixing zone was designed.
Model A: fully contractive mixing zone (outer diameter) and center-body shape (inner diameter) along flow direction.
Model B: straight center-body shape. Contractive outer diameter then expanded close to burner exit.
Model C: since using diffusor shape would leads to local low velocity and induce flashback, here the center-body is cut axially and increased downstream diameter.
The flow field and flame field were calculated with same inlet boundary condition under atmospheric condition.