Investigation on the internal flow characteristics of pressure-swirl atomizers.

摘要

The performance of liquid fuel atomizer in gas turbine combustor has direct effects on flame stability, combustion efficiency, and pollutant emissions. Therefore, further understanding of the underlying physics of these atomizers is one of the primary requirements for advanced gas turbine combustor design. Simplex atomizers are commonly used in air-breathing gas turbine engines because they produce good atomization characteristics and are relatively simple and inexpensive to manufacture. Internal flow characteristics of simplex nozzles play a very important role on the atomizer performance. So it is of great practical interest to examine the relationships between internal flow characteristics, nozzle design variables, and important spray features.; Part I of this dissertation revealed the detailed flow structure inside simplex atomizers through the DPIV and LDV study. The internal flow field is generally symmetric except very near the inlet slot plane. The velocity profiles are very similar at different axial locations within the swirl chamber. The discharge parameters were measured and used to examine the correlations from previous researchers. Detailed flow field information was linked with the discharge parameters to obtain more insight into the nozzle performance. The relationship between the internal flow characteristics and discharge parameters confirmed that the internal flow structure plays a very important role on the atomizer performance.; Part II presents the internal flow structure of large-scale simplex nozzles at two different working-fluid/ambient-fluid density ratios. The effects of density ratio, Reynolds number and orifice geometry on the internal flow field were examined by using a 2-D LDV probe. At the higher density ratio, Reynolds number and orifice geometry has little impact on the internal flow field. At the lower density ratio, the orifice contraction angle has little effect on the internal flow field, whereas the expansion angle can significantly affect the internal flow structure. A dominant frequency was found from the velocity frequency analysis, which indicates that the internal flow is controlled by certain dominant frequency. A dimensionless vortex shedding frequency, similar to the Strouhal number in the flow past a cylinder, was defined using the orifice diameter and mean axial velocity in the orifice.; In the part III of this dissertation, the internal flow field of the simplex atomizer with macrolaminated geometry was measured using the refractive index matching fluid method and DPIV system. In the swirl chamber, the liquid flow shows unsteady three-dimensional features, which is more evident as the flow rate increases. In the orifice, the liquid flow is more uniform and axisymmetric. The discharge parameters were measured and compared with the correlations from previous researchers.