The flowfields in a model combustor with primary holes after different swirl cups

The characteristics of the flow fields in a model combustor's primary zone, which is confined by different swirl cups and the flame tube with primary holes and cooling air films, is experimentally investigated by a Particle Dynamic Analyzer (PDA). The spray of RP-3 jet fuel from the atomizer is used as the trace particles for laser detection. The inlet air pressure and temperature are 110 KPa and 300 K, respectively. The test sections start from 10 mm and end at 50 mm downstream the swirl cup, ensuring that the primary holes are located within the test range. The results show that the swirl cup with double radial swirlers causes a greater flow expansion than that with double axial swirlers, thus results in a greater recirculation zone. By comparison with the previously reported data for the flow field after a pure swirl cup, it can be concluded that the flow field, especially the recirculation zone, in the primary zone with primary hole jets, is no longer axisymmetrical, as it was after a pure swirl cup. The presence of primary hole air flows remarkably squeezes the recirculation zone, especially for double radial swirlers; thus resulting in a elliptic-like cross section, with the longer axis greater than the shorter one up to 2.3 times, and causing the diminish of the corner recirculation zone. The recirculation zone is always ended at the primary holes, resulting in a much shorter length of the recirculation zone, which is only about 1.3 times of the exit diameter of the swirl cup, instead of 2.5 times for the pure swirl cup structure without the primary holes.